Environmental Engineering and Management Journal, Vol. 6 Nr. 6

Environmental Engineering and Management Journal November/December 2007, Vol.6, No.6, 479-482

http://omicron.ch.tuiasi.ro/EEMJ/

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PHENOL DEGRADATION IN WATER THROUGH A HETEROGENEOUS

PHOTO-FENTON PROCESS

Beatrice Iurascu1, Ilie Siminiceanu1∗, Miguel Vincente2

“Gh. Asachi” Technical University of Iasi, Faculty of Chemical Engineering, Department of Engineering Inorganic Substances,

71A D.Mangeron Bd., 700050 - Iasi, Romania 2University of Salamanca, Department of Inorganic Chemistry, Spain

Abstract A new photo-Fenton catalyst has been manufactured from synthetic layered clay laponite (Laponite RD) by the pillaring technique Eight different catalyst samples were prepared: four without thermal aging (WTA) calcined at 523 0K, 623 0K, 723 0K and 8230 K, and other four with thermal aging (TA) calcined at the same temperatures. The activity of the TA- 623 sample was evaluated in the phenol degradation by the photo- Fenton process. The influence of five important operating factors has been studied experimentally: the wavelength of the light source (UV-C and UV-A); catalyst dose( 0 to 2 g/L), initial phenol concentration ( 0.5 to 1.5 mM), hydrogen peroxide initial concentration ( 20 to 100 mM) and th initial solution pH (2.5 to 3.5 ) at 303 K.The results have shown that the almost complete conversion was possible , after only 5 minutes, under the following operating conditions: a low pressure mercury lamp as source of UV-C of 254 nm; pH3; a dose of 1 g catalyst/ L, a hydrogen peroxide concentration of 50 mM for a solution containing 1mM phenol , at 303 K. Key words: phenol degradation, Fe- Lap-RD catalyst, photo- Fenton, kinetic experiments, factor influence

∗ Author to whom all correspondence should be addressed: [email protected]

1. Introduction

The phenols have become the most abundant pollutants in industrial wastewater, due to their wide utilization in different industries (Almaizy and Akgerman, 2000; He et al., 2005; Kusic et al., 2006). Their presence contributes notably to the pollution of the effluents due to their high toxicity to aquatic life. The LD50 dose for aquatic organisms, determined on Daphnia is 12 mg phenol/L in 48 hours. They also may cause carcinogenic and mutagenic effects to humans (Kusic et al., 2006). Therefore, the maximum concentration of phenol in EU in water is 0.5 µg/L.

Common commercial wastewater treatment methods utilize the combination of the biological, physical and chemical treatment (Droste, 1997; Gogate and Pandit, 2004a/b).The biological treatment units tend to become very large due to the slow biological reactions. The physical methods only transfer waste components from one phase to another. Chemical treatment of phenols, such as chlorination,

can result in formation of chlorinated phenols and their byproducts which have been reported as toxic and non biodegradable (Gogate and Pandit, 2004a).

An attractive alternative for the removal of organic contaminants from wastewater are the so called advanced oxidation processes (AOPs) which generate hydroxyl radicals in sufficient quantities to oxidize the majority of the organics present in the effluent water (Siminiceanu, 2003). The AOPs used in the laboratory studies for phenol degradation have been reviewed and compared (Esplugas et al., 2002; Gimeno et al., 2005).The photo-Fenton process has been found the most effective among the investigated AOPs. The high effectiveness of the photo-Fenton process is attributed to the formation of hydroxyl radicals (HO.) in the reaction (1), and the regeneration of Fe(II) ions by photo- reduction of Fe(III) ions (reaction 2):

Fe2+ + H2O2 + hν = Fe (OH)2+ + HO. (1)

“Gh. Asachi” Technical University of Iasi, Romania

Iurascu et al. /Environmental Engineering and Management Journal 6 (2007), 6, 479-482

480 4

Fe (OH)2+ + hν = Fe2+ + HO. (2)

Despite its effectiveness, the homogeneous photo- Fenton process has an important drawback for practical application to large water flow rates, caused by sludge formation in the final neutralization step (Siminiceanu, 2003). Therefore, new heterogeneous Fe-based catalysts have been prepared and tested (Carriazo et al., 2003; Feng et al., 2006; Iurascu et al., 2006; Sum et al., 2005; Timofeeva et al., 2005).

Sum et al. (2005) prepared a new laponite clay-based Fe nanocomposite as heterogeneous photo- Fenton catalyst, and tested it in the mineralization process of an azo- dye Acid Black 1 (AB 1) in water , in the presence of H2O2 and UV light. Under the optimal reaction conditions found by the authors (0.1 mM AB1, 6.4 mM H2O2, 1.0 g catalyst/L, pH3, 8W UV-C) they achieved a complete discoloration and a 90% mineralization after 90 min reaction time, and a complete TOC removal after 4 cycles of 2h reaction time. These encouraging results determined the authors of the present paper to prepare a similar catalyst and to test it in process of the degradation of phenol in water.

2. Experimental

The synthetic laponite clay (laponite RD) was

supplied by Bresciani S.R.L. and used as starting material to prepare a series of Fe-Lap-RD catalysts. The laponite RD powder has a specific area of 370 m2/g. The rest of the chemicals employed in the experiments were supplied by Merck (H2SO4 98% and H2O2 35%), Sigma-Aldrich (Na2CO3, KI, KH2PO4, NaOH, phenol and Fe (NO3)3⋅9H2O). The water used was of Milli-Q quality.

A series of Fe-Lap-RD catalysts were prepared through a reaction between a solution of iron salt and a dispersion of laponite RD clay. Firstly an aqueous dispersion of laponite RD clay was prepared by adding 2 g laponite RD to 100 mL H2O under vigorous stirring. Secondly, sodium carbonate was added slowly as a powder into a vigorously stirred 0.2 M solution of iron nitrate such that a molar ratio of 1:1 for [Na+]/[Fe3+] was established. The obtained solution was added very slowly into the dispersion of laponite clay prepared in the first step until a ratio of 11 mmol Fe3+ per gram clay was achieved. The suspension was stirred 2 h and then divided into two portions. One portion was kept in an oven at 373 K for two days. For simplicity this portion will be referred as “thermally aged” (TA). Another portion, referred as “without thermal aging” (WTA) was stirred for two days at room temperature to allow sufficient intercalation of the clay. After that, the precipitate of each portion was collected by centrifugation and washed several times with deionised water to ensure that all the Na+ ions were removed. The recoveries were dried at a temperature of 373 K for 24 h and further divided into four equal portions. The two portions underwent a calcination process at different temperatures for 24 h. The

calcination temperatures were 523, 623, 723, and 823 K. For simplicity, the clays will be referred as: WTA-T for the clays obtained without thermal aging and TA-T for the clays prepared by thermal aging; T represents the calcination temperature used in this study: 523, 623, 723, and 823 K The characterization of catalyst samples by chemical analysis, SEM/EDS, XRD and DTA was described in a previous paper (Iurascu et al., 2006).

The photocatalytic activity of each pillared clay was evaluated in the process of mineralization and conversion of a 0.1 mM phenol solution in the presence of 5 mM H2O2, 1 g/L catalyst and UV irradiation using a Unilux Philips lamp (15W UV-C, λ=254 nm). Irradiation was carried out in magnetically stirred, cylindrical Pyrex quartz cell (4 cm diameter, 2,3 cm height) containing 10 mL solution, at room temperature. The pH was adjusted to 3 using a H2SO4 solution. This is the optimal pH in the homogeneous photo-Fenton process (Siminiceanu, 2003). The start of the reaction was considered to be the moment when the cell was put under the UV-C lamp. After irradiation the catalyst was separated from the solution by filtration with Hydrophilic PTFE Millex-LCR filter (pore diameter 0.45x10-9 m).

The conversion of phenol was measured using a Merck-Hitachi HPLC. The column used was a RP-C18 LichroCARP (Merck, length 125 mm, diameter 4mm) packed with Li-Chrospher 100 RP-18 (5x10-9 m diameter). Isocratic elution was performed with a 30/70 mixture of acetonitrile/aqueous phosphate buffer (0.05 M, pH 2.8). The mineralization of phenol was measured using a Shimadzu TOC 5000 Analyzer. The leaching iron (Fe3+ and Fe2+) from the catalysts was measured using a UVVIS Cary 100 Scan spectrophotometer and a Merck reagent Spectroquant. The experimental determinations were carried out at a wavelength of 565 nm. Because the reaction was still going on after the irradiation time was over, it was necessary to use a stopping reagent, which contained 0.1M Na2SO3, 0,1M KH2PO4, 0,1M KI and 0,05M NaOH. The stopping reagent was injected in the sample solution immediately after filtration, using a 1:1 volumetric ratio. After the selection of the pillared clay with the best activity and the smallest quantity of leached iron, the influences of several parameters over photo-activity such as UV light wavelength, initial concentration of phenol, initial concentration of H2O2, initial catalyst dose and initial pH, were studied. 3. Result and discussion

The results are presented under the form of the kinetic curves CPh versus time, or XPh versus time. The conversion degree of the phenol XPh has been calculated with Eq. (3):

XPh = 1- CPh/ Co

Ph (3)

Phenol degradation in water through a heterogeneous photo-Fenton process

481

where C0Ph is the initial molar concentration of the

phenol, and CPh is the molar concentration of the residual phenol at a given time. 3.1. Influence of the light source

Fig. 1 presents the influence of the light source

on the phenol conversion, at different catalyst doses, and the other constant factors ( C0

Ph = 1 mM; C0H2O2 =

50 mM, pH3; T= 303 K). The low pressure mercury lamp emitting UV-C of 254 nm was more effective than the lamp emitting UV-A.

Fig.1. Influence of light source (C0Ph = 1 mM; C0

H2O2 = 50 mM, pH3; T= 303 K)

3.2. Influence of the catalyst dose

Fig. 2 presents the results for different catalyst

doses with a UV-A lamp of 40 W and the other constant factors (C0

Ph = 1 mM; C0H2O2 = 50 mM, pH3;

T= 303 K). The best results have been obtained with a dose of 1g catalyst/ L.

Fig.2. Influence of catalyst dose on the phenol conversion. ( C0

Ph = 1 mM; C0H2O2 = 50 mM, pH3; T=

303 K)

3.3. Influence of initial phenol concentration in water The influence of the initial phenol

concentration is illustrated in the Fig. 3.

Fig.3. Influence of the initial phenol concentration (catalyst dose of 1g/L; C0

H2O2 = 50 mM, pH3; T= 303 K

3.4. Influence of hydrogen peroxide dose

Fig. 4 presents sections at constant reaction time of the kinetic curves. The results show that for a solution with 1mM phenol the optimal dose is of 50 mM hydrogen peroxide.

Fig.4. Influence of the hydrogen peroxide dose at different reaction time (C0Ph = 1 mM; catalyst dose of 1g/L, pH3;

T= 303 K)

3.5. Influence of pH The results, represented in Fig. 5, have shown

that the maximal conversion could be obtained with a pH between 2.5 and 3.0. This is in accordance with previous experimental and theoretical studies on homogeneous photo-Fenton process.

Iurascu et al. /Environmental Engineering and Management Journal 6 (2007), 6, 479-482

482 4

Fig.5. Influence of pH on the phenol conversion. ( C0

Ph = 1 mM; C0H2O2 = 50 mM, catalyst dose of 1g/L; T=

303 K) 4. Conclusions

A new heterogeneous photo-Fenton catalyst

has been prepared by the intercalation and pillaring of a laponite clay with iron salt. Eight different catalyst samples were prepared: four without thermal aging (WTA) calcined at 523 K, 623 K, 723 K and 823 K, and other four with thermal aging (TA) calcined at the same temperatures. Catalyst samples thermally aged at 623 K have been used to study the influence of five factors on the phenol conversion by the photo-Fenton process: light source, catalyst dose, initial phenol concentration, hydrogen peroxide dose, and pH.

The results could be useful for the selection of optimal operating parameters as well as for further kinetic interpretation. References Almaizy R., Akgerman A., (2000), Advanced oxidation of

phenolic compounds, Adv.Environ. Res, 4, 233- 244.

Carriazo J.G., Guelou E., Barrault J., Tatibouet J.M., Moreno S., (2003), Catalytic wet peroxide oxidation

of phenol over Al- Cu or Al- Fe modified clays, Appl. Clay Science, 22, 303- 308.

Droste R.J., (1997), Theory and Practice of Water and Wastewater Treatment, John Wiley and Sons, New York, 450.

Esplugas S., Gimenez J., Contreras S., Pascual E., Rodriguez M., (2002), Comparison of different advanced oxidation processes for phenol degradation, Water. Res., 36, 1034- 1042.

Feng J., Hu X., Yue P.L., (2006), Effect of initial solution pH on the degradation of Orange II using clay-based Fe nanocomposites as heterogeneous photo-Fenton Catalyst, Water Res., 40, 641- 646.

Gimeno O., Carbajo M., Beltran F.J., Rivas F.J., (2005), Phenol and substituted phenols AOPs remediation, J. Hazard. Mater. B, 119, 99-108.

Gogate P.R., Pandit A.B., (2004a), A review of imperative technologies for wastewater treatment.I.Oxidation technologies at ambient conditions, Adv. Environ. Res., 8, 501- 551.

Gogate P.R., Pandit A.B., (2004b), A review of imperative technologies for wastewater treatment.II.Hybrid methods, Adv. Environ. Res., 8, 553- 597.

He Z., Liu J., Cai W., (2005), The important role of the hydroxyl ion in phenol removal using pulsed corona discharge, J. Electrostat., 65, 371- 386.

Iurascu B., Siminiceanu I., Vione D., (2006), Preparation and characterization of a new photocatalyst from synthetic laponite clays, Bul. Inst. Polit. Iasi, 51, 21-27.

Kavitha V., Palanivelu K., (2004), The role of ferrous ion in Fenton and photo-Fenton processes for the degradation of phenol, Chemosphere, 55, 1235- 1243.

Kusic H., Koprivanac N., Bozic A.L., Selanec I., (2006), Photo-assisted Fenton type processes for the degradation of phenol: a kinetic study, J.Hazard.Mater., 120, 109-116.

Siminiceanu I., Procese fotochimice aplicate la tratarea apei, Tehnopres, Iasi, 125- 136.

Sum O.S.N., Feng J., Hu X., Yue P.L., (2005), Photo-assisted Fenton mineralization of an azo- dye Acid Black 1 using a modified laponite clay-based Fe nanocomposite as heterogeneous catalyst, Topics in Catalysis, 33, 233- 242.

Timofeeva M.N., Khankhasaeva S.Ts., Badmaeva S.V., Chuvilin A.L., Burgina E.B., Ayupov A.B., Pachenko V.N., Kulikova A.V., (2005), Synthesis, characterization and catalytic application for wet oxidation of phenol of iron- containing clays, Applied Catalysis B: Environment, 59, 243- 248.



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STUDY CONCERNING THE INFLUENCE OF OXIDIZING AGENTS

ON HETEROGENEOUS PHOTOCATALYTIC DEGRADATION OF PERSISTENT ORGANIC POLLUTANTS

Anca Florentina Căliman1∗, Camelia Beţianu1, Brînduşa Mihaela Robu1, Maria Gavrilescu1, Ioannis Poulios2

1“Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering, Department of Environmental Engineering

and Management, 71 Mangeron Blvd., 700050 - Iasi, Romania 2Aristotle University of Thessaloniki, Department of Chemistry, Laboratory of Physical Chemistry, 54006 Thessaloniki,

Greece

Abstract In this paper, the application of the heterogeneous photocatalysis in degradation of a cationic copper phtalocyanine dye, used as model of persistent organic compound is investigated by assessing the efficiency of the process. The influence of hydrogen peroxide on the photocatalytic process is studied using two types of commercial catalysts, such as TiO2 Degussa (88% anatase, 20% rutile) and TiONa Millennium (100% anatase). Another electron acceptor, FeCl3 is also used for investigation of adsorption and photocatalytic degradation efficiencies of the dye on TiO2 Degussa photocatalyst. The results have shown that Millennium photocatalyst and the iron(III) salt exhibit a negative influence upon the studied process. Key words: Keywords: heterogeneous photocatalysis, oxidizing agents, persistent organic pollutants

∗ Author to whom all correspondence should be addressed: e-mail: [email protected]

1. Introduction

Heterogeneous photocatalysis was intensively studied in the last decade due to the fact that it may be applied for degradation of a big number and various types of persistent pollutants, resulting in complete mineralization of the majority of non-biodegradable compounds.

Thus, the heterogeneous photocatalytic process was used for oxidation of pesticides (Mahmoodi et al., 2007; Kwan and Chu, 2003; Oreopoulou and Philippopoulos, 2003; Konstantinou and Albanis, 2002; Parra et al., 2002(a); Parra et al., 2002(b); Higarashi and Jardim, 2000; Malato et al., 2000; Gawlik et al., 1999), dyes (Subramani et al., 2007; Byrappa et al., 2006; Miranda et al., 2006; Guettai and Amar, 2005; Bhattacharyya et al., 2004; Fernandez at al., 2004; Neppolian et al., 2003), phenol and phenolic compounds (Kusvuran et al., 2005; Pandiyan et al., 2002, San et. Al., 2002; Peiro et al., 2001; Ilisz and Dombi, 1999) or substances that are contained in products for hygienic use (Couteau et al.,

2000), as well as for reduction of heavy metals (Chan and Ray, 2001; Datye at al., 1998).

Among the numerous toxic pollutants, dyes may exhibit an eco-toxic hazard, introducing the potential danger of bioaccumulation that may eventually affect humans by transport through the food chain, hence their removal from wastewaters and sludge is highly requested.

As dyes are designed to be chemically and photolytically stable, they are highly persistent in natural environments and, consequently, powerful tools for remediation of the environmental factors are necessary.

The ineffectiveness of conventional methods such as adsorption, precipitation, chemical coagulation etc. for color removal led to the necessity to develop other efficient treatment processes. In this context, heterogeneous photocatalysis emerged as a very attractive alternative to the conventional treatment methods.


Caliman et al. /Environmental Engineering and Management Journal 6 (2007), 6, 483-489

484 4

*In heterogeneous photocatalysis, conduction band electrons (e-) and valence band holes (h+) are generated by the irradiation of an aqueous TiO2 suspension with artificial or solar light having energy greater than the band gap energy of the semiconductor. The photogenerated electrons react with the adsorbed molecular O2 on the Ti(III)-sites, reducing it to superoxide radical anion O2•-, while the photogenerated holes can oxidize either the organic molecules directly or the OH- ions and the H2O molecules adsorbed at the TiO2 surface to hydroxyl radicals, which act as strong oxidizing agents. These can easily attack the adsorbed organic molecules or those located close to the surface of the catalyst, leading finally to their complete mineralization.

In order to enhance the efficiency of heterogeneous photocatalysis, substances that act like electron acceptor are used, with the aim at preventing the electron-hole recombination by reacting with the excess electrons from the conduction band. Literature reports indicate the increase of the photocatalytic rate upon addition of different compounds, such as: H2O2 (Hofstadler and Bauer, 1994); K2S2O8 (Shankar et al., 2001); KBr (Al-Ekabi et al., 1993); AgNO3 (Ilizs et al., 1999); FeCl3 (Sakthivel et al., 2000); potassium peroxymonosulphate (oxone) (Al-Ekabi et al., 1993); Fenton’s reagent (Malato et al., 2002).

In this paper, the influence of two oxidizing agents, such as hydrogen peroxide and iron(III) salt, on the semiconductor mediated photodegradation of organic pollutants using aqueous solutions of cationic dye Alcian Blue 8 GX as model molecule, was studied. 2. Experimental 2.1. Regeants

The reactive Alcian Blue 8GX (Ingrain Blue 1) with molecular formula C56H68Cl4CuN16S4 and the average molecular weight M = 1298.86, a product of Sigma Chemie Gmbh was used as received. TiO2 P-25 Degussa (anatase/rutile = 3.6/1, surface area 56 m2g-1) and TiONa PC 500 (100% anatase, more than 250 m2 g-1), product of Millennium Chemicals, were utilized (Fig. 1).

Fig.1. Molecular structure of Alcian Blue 8 GX

2.2. Procedures and analysis

Experiments were carried-out in a closed Pyrex cell of 500 ml capacity, provided with ports, at the top, with the aim at bubbling air necessary for the reaction (Fig. 2).

The reaction mixture was maintained as suspension by magnetic stirring. Previously irradiation, the reaction mixture was left 30 minutes in the dark in order to achieve the maximum adsorption of the dye onto the semiconductor catalyst surface.

The irradiation was performed with a 9 W central lamp The spectral response of the irradiation source (Osram Dulux S 9W/78 UV-A, 14.5 cm length and 2.7 cm diameter), according to the producer is ranged between 350 and 400, with a maximum at 366 nm and two additional weak lines in the visible region. The photon flow per unit volume of incident light was determined by chemical actinometry using potassium ferrioxalate. The initial light intensity, under exactly the same conditions in the photocatalytic experiments, was assessed as being 7.16 Einstein min-1.

In all the cases, during experiments, 450 ml of Alcian Blue 8 GX solution containing appropriate amount of semiconductor powder was magnetically stirred before and during irradiation. Specific quantities of samples were withdrawn at periodic intervals and filtered through a 0.45 µm filter (Schleicher and Schuell) in order to remove the catalyst particles.

With the aim at assessing the extent of color removal, changes in the concentration of the dye were observed from its characteristic absorption band using a UV-Vis spectrophotometer Shimadzu UV-160 A.

Fig.2. Experimental set-up for study of photocatalytic oxidation of Alcian Blue 8 GX

The photodecomposition was monitored

spectrophotometrically at 609 nm in the absence and at 597 nm in the presence of iron salt, when linear dependences between the initial concentration of the Alcian Blue solution and these absorptions, for the two studied conditions, was obtained.

Study concerning the oxidizing agents on heterogeneous photocatalytic degradation

485

3. Results and discussions 3.1. Comparison of photocatalytic degradation of Alcian Blue 8 GX in the presence of H2O2 on two commercial catalysts

In general, hydrogen peroxide contributes to the enhancement of the heterogeneous photocatalytic efficiency through generation of the hydroxyl radicals in the presence of light, as well as by scavenging the electrons, inhibiting hence, their recombination with the generated holes. However cases of a negative influence of H2O2 were reported when the anatase form of the commercial catalysts was used in the system (Caliman et al., 2006; Velegraki et al., 2006).

The efficiency of 15 minutes dark adsorption (a) as well as the efficiencies of the photocatalytic degradation (b) of 40 mg L-1 Alcian Blue 8 GX on 0.5 g L-1 TiO2 P-25, at the natural pH of solution (equal to 4.35 units) and in the presence of different amounts of H2O2 (which were calculated for 20 minutes of irradiation, when data were available for the whole interval of studied concentrations of the oxidant ranged between 10 and 400 mg L-1) are presented in figure 3.

The efficiencies for the two situations were calculated with the relations (1, 2):

1000

0

a

taaads C

CC −=η (1)

1000

0

ph

tphphph C

CC −=η (2)

where Ca0 = concentration of the solution before the catalyst was added, Cat = concentration after t minutes of dark adsorption (15 minutes), Cph0 = concentration of dye solution before UV irradiation and Cpht = concentration of solution after t minutes of UV exposure.

One may see that a strong adsorption of the dye in the presence of the oxidizing agent occurs. While at the natural pH of the solution, in the absence of a H2O2, the efficiency of the dark adsorption on 0.5 g/L TiO2 P-25 was of around 24%, in the presence of 200 mg L-1 oxidant, it reaches almost 70%. This strong adsorption may be the result of decrease of the acidity of the environment through addition of H2O2, decrease that has a positive influence on the adsorption of the cationic dye on the catalyst surface, as it was shown in the study of pH influence upon the process, concordant to the data reported in a previous paper (Caliman et al., 2007).

The effect of hydrogen peroxide resulted in an increase of the pH from the value of 4.35 units, in the absence of the oxidant, to 5.7 in the presence of 400 mg L-1 H2O2, the average value of the pH in the limits of the used concentrations being equal to 5.

At the same time, high amounts of hydrogen peroxide results in up to 90% color removal under irradiation.

Analysis of the concentration of hydrogen peroxide revealed that 66%-74% of the oxidant remained in solution at the end of the photocatalytic process, when high concentrations of oxidant were used, as it is shown in Table 1. Thus, it may be observed that the oxidant was totally consumed when low concentrations of H2O2 were added into the system, while at concentration above 100 mg L-1 different percents of hydrogen peroxide remained unconsumed. This support the data depicted in Fig. 3, which shows that above this concentration, the photocatalytic efficiency is almost constant.

-25 0 25 50 75 100125150175200225 250275300325350375400 4250

10

20

30

40

50

60

70

80

90

100(a)

different concentrations of H2O2 no H2O2

dark

adsor

prtion

efffi

cienc

y (%)

H2O2 concentration (mg L-1)

-25 0 25 50 75 100 125150175 200 225 250275 300 325350 375 400 4250

20

40

60

80

100(b)

different concentrations of H2O2 no H2O2

phtod

egrad

ation

effic

iency

(%)

H2O2 concentration (mg L-1)

Fig.3. Influence of H2O2 concentration upon dark adsorption (a) and photocatalytic degradation (b)

efficiencies of 40 mg L-1 Alcian Blue 8 GX (0.5 g L-1 TiO2 P-25, pH = 4.35)

The influence of H2O2 was also studied in the

case of other photocatalyst (TiONa Millennium) the results being compared with those obtained when TiO2 Degussa was utilized (Fig.4). It is obviously that addition of the oxidant has a bigger influence in the case of P-25, when also strong adsorption of the


486 4

intermediates is observed in the first minutes of irradiation. In the second case, the results concerning the degradation degree are not very much different, as data from the Table 2 reveal.

Table 1. Values of the percent of H2O2 remained

unconsumed at the final of the process H2O2 initial

concentration mg L-1

% H2O2 in solution at the end of the process

mg L-1 10 - 25 - 50 - 100 32 200 66 400 74.5

-20 0 20 40 60 80

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8 0,5 g L-1 TiO2 P-25

0,5 g L-1 TiO2 P-25 + 100 mg L-1 H2O2

0,5 g L-1 TiONa

0,5 g L-1 TiONa + 100 mg L-1 H2O2

abso

rban

ta (6

09 n

m)

durata iradierii, min

Fig. 4. Influence of optimum concentration of H2O2 (100

mg L-1) on photocatalytic degradation of 40 mg L-1 Alcian Blue upon two different catalysts: TiONa and P-25

(concentration of catalysts: 0.5 g L-1)

Table 2. Comparison between degradation rates in the case of heterogeneous photocatalytic degradation of 40 mg L-1

Alcian Blue 8 GX on two types of catalysts (TiONa and TiO2 P-25 in the presence and, respectively, absence of

H2O2

Concentration of catalyst or catalyst +

H2O2

Reaction rate

(mg L-1 min-1)

Correlation coefficient

R 0.5 g L-1 TiO2 P-25 0.62831 0.99396

0.5 g L-1 TiO2 P-25 + 100 mg L-1 H2O2

1.16706 0.99913

0.5 g L-1 TiONa 0.62502 0.97736 0.5 g L-1 TiONa + 100 mg

L-1 H2O2

0.39774 0.95963

3.2. Study concerning dark adsorption and photocatalytic degradation of Alcian Blue 8 GX on TiO2 P-25 in the presence of FeCl3

Addition of FeCl3 should have a positive effect on photocatalytic degradation of the organic compounds owing to generation of HO• in aqueous solutions with the participation of ferric ions and the products of their hydrolysis, although there were reported also cases of a detrimental action of the iron salt (Baran et al., 2003).

The efficiencies of the dark adsorption process (15 minutes) on 0,5 g L-1 P-25, respectively photocatalitic process, after 30 minutes of irradiation of 40 mg L -1 Alcian Blue 8 GX, in the presence of FeCl3 are exhibited in Fig. 5. As one can see, the removal of color was mainly achieved in the dark period (70%), followed by a small variation of the process efficiency after irradiation, especially for the higher amounts of iron salt (>28 mg L-1).

0 7 14 21 28 35 42 49 56 630

20

40

60

80

100

(a)

dark

adso

rption

effic

iency

%

FeCl3 concentration, mg L-1

0 7 14 21 28 35 42 49 56 630

20

40

60

80

100 (b)

phot

odeg

radati

on ef

ficien

cy %

FeCl3 concentration, mg L-1

Fig. 5. Influence of FeCl3 concentration upon dark adsorption (a) and photocatalytic degradation (b)

efficiencies of 40 mg L-1 Alcian Blue 8 GX (0.5 g L-1 P-25, pH = 3.7)

Considering the fact that the removal of color

was observed mainly for the dark adsorption period, the study of the dark adsorption process appeared necessary in order to assess the influence of the iron salt upon this process. Thus, experiments concerning the measurement of the absorbance after 15 minutes of dark adsorption of 20 mg L-1 dye in the presence of different concentrations of catalyst P-25 only (Fig. 6a) and also in the presence of 0.1 g L-1 catalyst and different amounts of FeCl3 (Fig. 6b) were conducted.

The values regarding the percents of color removal after dark adsorption were calculated with the following expression:


487

100%0

0

AAA −

= (3)

where: A0 = absorbance of dye solution before adding catalyst, A = absorbance of dye solution after a certain time t.

The calculated values are presented in Table 3 for 1 minute and 15 minutes, respectively, of dark adsorption.

0 5 10 15 20 25 300,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0 0,02 g L-1 TiO2 P-25

0,05 g L-1 TiO2 P-25

0,1 g L-1 TiO2 P-25

0,2 g L-1 TiO2 P-25

abs/a

bs0 (

609 n

m)

dark adsorption time, min

0 2 4 6 8 10 12 14 160,0

0,2

0,4

0,6

0,8

1,0 0,1 g L-1 TiO2 P-25 14 g L-1 Fe3+, pH = 3,5 28 g L-1 Fe3+, pH = 3,55 56 g L-1 Fe3+, pH = 3,45

abs/a

bs0 (

597 n

m)

dark adsorption time, min

Fig. 6. Effect of concentrations of catalyst and iron salt,

respectively, on dark adsorption of 20 mg/L Alcian Blue 8 GX: abs/abs0 vs irradiation time at various concentrations of

TiO2 P-25 (0.02-0.2 g L-1) (a) and abs/abs0 vs irradiation time at various concentrations of FeCl3 (14-56 mg L-1) (b)

In the absence of FeCl3, it is obvious that the

adsorption is very fast at the beginning, in the first minute being removed around 34-42 % of the dye color, after this time, the process becoming almost constant, with slow variation of dye concentration. Thus, after 15 minutes, which was the period of dark pre-equilibration of the dye solution in all the experiments, percents of color removal ranged between 36–46% were achieved. The same trend is also observed for the case of FeCl3 presence in system, but the percent removal of color was higher (75-79%). Due to the fact that, generally, when FeCl3

is added in system, a competition must occur between its molecules and that of the dye for the active sites of the catalyst one can conclude that color removal may be the result not of adsorption but of precipitation of the formed insoluble complex formed by the dye with iron.

Table 3. Dark adsorption efficiency (percent removal of color) at different concentration of TiO2 P-25 and FeCl3,

respectively

% Removal of color at different catalyst

concentration (g L-1)

Duration of dark adsorption of 20 mg L-1 AB 8 GX on P-25 (min) 0.02 0.05 0.1 0.2

1 33.78 34.28 37.83 41.66 15 45.94 36 40.54 37.77

% Removal of color at different concentration of FeCl3 (mg L-1)

Duration of dark adsorption of 20 mg L-1 AB 8 GX on 0.1 g L-1 P-25

(min) 14 28 56

1 69.69 66.66 70.83 15 78.84 78.18 75

In the case of solution with very high amount

of FeCl3 (112 mg L-1), a smaller decrease of color removal (75%) was achieved after 15 minutes dark adsorption, while a higher one was observed after first minutes of irradiation (Fig. 7).

-20 -10 0 10 20 300,1

0,2

0,3

0,4

0,5

0,6

0,7

abso

rban

ce (5

97 n

m)

irradiation time, min

Fig. 7. Absorbance versus irradiation time for

degradation of 40 mg L-1 Alcian Blue 8 GX on 0.5 g L-1 P-25 in the system containing very high amounts of FeCl3

(112 mg L-1)

In order to check this behavior, another experiment was done with the system containing 112 mg L-1 FeCl3 that was subjected one hour to dark adsorption and one hour to irradiation (Fig. 8). One may observe that a significant decrease of the absorbance occurs in the first 20 minutes, remaining almost constant after this period and decreasing quite high again under the first 10 minutes of irradiation.

It should be noticed that, while for 7-56 mg L-1 FeCl3 most of the dye color was removed in 15 minutes of dark adsorption, in the case of using very high amount of iron(III) salt (112 mg L-1), removal of color of the solution in the adsorption process is smaller, as Figs. 7 and 8 show. The lower decolorization in the latter case may owe to the excess of Fe3+ and colored products resulted from its


488 4

hydrolysis, while the higher decrease of absorbance after 60 minutes of dark adsorption and 10 minutes of irradiation to be the results of transformation of the excess of colored Fe3+ into colorless Fe2+ concordant to the photo-Fenton reaction:

Fe3+ + hυ + H2O→ Fe2+ + OH• + H+ (4)

After this period the efficiency of the UV exposure increased slower due to deposition on TiO2 of the precipitate formed in the reaction of the dye with the salt, which results in catalyst poisoning.

Fig. 8. Absorbance in the case of photocatalytic degradation of 40 mg L-1 on 0.5 g L-1 P-25 in the presence of 112 mg L-1

FeCl3 after 60 minutes adsorption in the dark and 60 minutes irradiation (pH=3.7)

4. Conclusions

The influence of H2O2 on heterogeneous photocatalysis was studied by comparison of the efficiency of the process obtained on TiO2 Degussa and TiONa Millennium. Data show that addition of P-25 is favorable up to a limit concentration, above which the efficiency of the process remained practically unchanged. Addition of the same amount of hydrogen peroxide into the system containing Millennium catalyst is detrimental to the process due to the strong chemisorption on TiONa of resulted intermediates, phenomenon that leads to blocking of the active centers.

Measurements of absorbance in the period of dark pre-equilibration of 20 mg L-1 dye, not only at different concentrations of P-25 catalyst, but also in the presence of 0.1 g L-1 TiO2 P-25 and diverse amount of FeCl3 have demonstrated that adsorption was very fast even from the beginning. Thus, in the first minute, percents of color removal of 34-42 % in the first case, and above 67 in the second case, were achieved. At the end of the 15 minutes of dark adsorption representing the pre-equilibration period in all experiments, efficiencies of 36–46% of the adsorption are attained in the system without iron salt.

When FeCl3 is present in the system, the percents of color removal are higher (75-79%), as a result of precipitation of the insoluble complexes formed by the dye with the iron. However, the influence of the iron salt on the process under irradiation is rather negative. Acknowledgement Part of this study was done within the PN-II-ID-595 project: “Integrated studies on the behavior of persistent pollutants and risks associated with their presence in the environment”. References Al-Ekabi H., Butters B., Delany D., Ireland J., Lewis N.,

Powell T., Story J., (1993), TiO2 advanced photo-oxidation technology: Effect of electron acceptors, In: Photocatalytic purification and treatment of water and air, Elsevier Publ, NL., 321-335,

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Bhattacharyya A., Kawi S., Ray M.B., (2004), Photocatalytic degradation of orange II by TiO2 catalysts supported on adsorbents, Catalysis Today, 98, 431-439.

Byrappa K., Subramani A.K., Ananda S., Rai K.M.L., Dinesh R.., Yoshimura M., 2006, Photocatalytic degradation of Rhodamine B dye using hydrothermally synthesized ZnO, Bull. Mater. Sci., 29, 433–438.

Caliman A.F., Cojocaru C., Antoniadis A., Poulios I., (2007), Optimized photocatalytic degradation of Alcian Blue 8 GX in the presence of TiO2 suspensions, Journal of Hazardous Materials, 144, 265-273.

Caliman A.F., Antoniadis A., Poulios I., Macoveanu M., (2007), Slurry reactor for heterogeneous photocatalytic degradation of Reactive Orange 16, Bulletin of Polytechnic Institute of Iasi, Section Chemistry and Chemical Engineering, tome 52, 1-2, in press.

Chen D., Ray A.K., (2001), Removal of toxic metals from wastewater by semiconductor photocatalysis, Chemical Engineering Science, 56, 1561-1570.

Couteau C., Jadaud M., Peigne F., Coiffard L.J.M., (2000), Influence of pH on the photodegradation kinetics under UV light of climbazole solutions, Analusis, 28, 557-560.

Datye A.K., Sherry H., Huang M., Griego J.R., Guryevich L., Peden C.H.F., (1998), TiO2 photocatalysts for treatment of hazardous waste: Removing strontium from wastewater, Technical Completion Report 92-08.

Fernandez J., Kiwi J., Freer J., Lizama C., Mansillia H.D., (2004), Orange II photocatalysis on immobilised TiO2. Effect of the pH and H2O2, Applied Catalysis B: Environmental, 48, 205-211.

Gawlik B. M., Moroni A., Bellobono I. R., Muntau H. W., (1999), Soil adsorption behaviour and photomineralization by photocatalytic membranes immobilizing titanium dioxide of atrazine and intermediates, Global Nest: the Int. J., 1, 23-32.


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Guettai N., Amar H.A., (2005), Photocatalytic oxidation of methyl orange in presence of titanium dioxide in aqueous suspensions. Part I: Parametric study, Desalination 185, 427-437.

Higarashi M.M., Jardim W.F., (2000), Photocatalytic treatment pf pesticide-contaminated soils using solar light and titanium dioxide, American Environmental Laboratory, 25, May.

Hofstadler K., Bauer R., (1994), New reactor design for photocatalytic wastewater treatment with TiO2 immobilised on fused silica glass fibres; photomineralization of 4- chlorophenol, Environ. Sci. Technol., 28, 670- 674.

Ilisz I., Laszlo Zs., Dombi A., (1999), Investigation of the photodecomposition of phenol in near-UV-irradiated aqueous TiO2 suspensions. I. Effects of charge traping species on the degradation kinetics, Applied Catalysis A: General, 180, 25-33.

Ilisz I., Dombi A., (1999), Investigation of the photodecomposition of phenol in near-UV-irradiated aqueous TiO2 suspensions. II. Effects of charge trapping species on product distribution, Applied Catalysis A: General, 180, 35- 45.

Konstantinou I.K., Albanis T.A., (2002), Photocatalytic transformation of pesticides in aqueous titanium dioxide suspensions using artificial and solar light: intermediates and degradation pathways, Applied Catalysis B: Environmental, 1310, 1–17.

Kusvuran E., Samil A., Atanur O.M., Erbatur O., (2005), Photocatalytic degradation kinetics of di- and tri- substituted phenolic compounds in aqueous solution by TiO2/UV, Applied Catalysis B: Environmental 58, 211-216.

Kwan C.Y., Chu W., (2003), Photodegradation of 2,4- dichlorophenoxyacetic acid in various iron-mediated oxidation systems, Water Research, 37, 4405–4412.

Mahmoodi N.M., Arami M., Limaee N.Y., Gharanjig K., (2007), Photocatalytic degradation of agricultural N-heterocyclic organic pollutants using immobilized nanoparticles of titania, Journal of Hazardous Materials, 145, 65-71.

Malato S., Blanco J., Richter C. Fernandez P., Maldonado M.I., (2000), Solar photocatalytic mineralization of commercial pesticides: Oxamyl, Solar Energy Materials and Solar Cells, 1-14.

Malato S, Blanco J, Vidal A., Richter C., (2002), Photocatalysis with solar energy at a pilot-plant scale: an overview, Applied Catalysis B: Environmental, 37, 1-15.

Miranda T., Alves R., Lichy L., MachalickY O., Hrdina R., Oliveira-Campos A., (2006), Photodegradation studies on C.I. Reactive Red 158, 3rd International textile, clothing and design conference – Magic World of Textiles, October 08-11, Dubrovnik, Croatia.

Neppolian B., Kanel S.R., Choi H.C., Shankar M.V.,

Arabindoo B., Murugesan V., (2003), Photocatalytic degradation of Reactive Yellow 17 dye in aqueous solution in the presence of TiO2 with cement binder, International Journal of Photoenergy, 5, 45-49.

Oreopoulou A., Philippopoulos C., (2003), Photocatalytic oxidation of agrochemical industry liquid wastewaters, 8th International Conference in Environmental Science and Technology, September 8-10, Lemnos Island, Greece.

Pandiyan T., Rivas O,. Martinez J., Amezuca G., Carillo M.A., (2002), Comparision of methods for the photochemical degradation of chlorophenols, Journal of Photochemistry and Photobiology A: Chemistry, 146, 149-155.

Parra S., Malato S., Pulgarin C., (2002), New integrated photocatalytic-biological flow using supported TiO2 and fixed bacteria for mineralization of isoproturon, Applied Catalysis B: Environmental, 36, 131–144.

Parra S., Olivero J., Pulgarin C., (2002), Relationships between physicochemical properties and photoreactivity of four biorecalcitrant phenylurea herbicides in aqueous TiO2 suspension, Applied Catalysis B: Environmental, 36 75–85.

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Shankar M.V., Neppolian B., Sakthivel S., Palanichamy M., Arabindoo B., Murugesan V., (2001), Kinetics of photocatalytic degradation of textile dye reactive red 2, Indian Journal of Engineering & Material Science, 8, 104-109.

Subramani A.K, Byrappa K., Ananda S., Rai K.M.L., Ranganathaiah C., Yoshimura M., (2007), Photocatalytic degradation of indigo carmine dye using TiO2 impregnated activated carbon, Bull. Mater. Sci., 30, 37-41.

Velegraki Th., Poulios I. Charalabaki M., Kalogerakis N. Samaras P., Mantzavinos D., (2006), Photocatalytic and sonolytic oxidation of acid orange 7 in aqueous solution, Applied Catalysis B: Environmental, 62, 159–168.



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NONMARKET VALUATION OF ACEQUIAS: STAKEHOLDER

ANALYSIS

Steven Archambault ∗, Joseph Ulibarri

University of New Mexico, Department of Economics MSC 05 3060, Albuquerque, NM 87131-0001, United States

Abstract From a traditional market economy perspective, the productivity attained when water and land is used for acequias is much lower than the productivity achieved when applying these same resources to urban and industrial uses. An analysis of key stakeholders has indicated that there are cultural and environmental attributes of acequia agriculture landscapes that are not captured in the market-assigned value of acequias. This analysis revealed the motivations behind the value placed on acequias by government, developers, policy organizations, religious groups, and other stakeholders. Such context may not be fully captured in a quantitative nonmarket valuation study. This research also identified potential policy and management initiatives that could improve the nonmarket value of acequias. These include investments in less water intensive acequia infrastructure and agriculture techniques; supporting education and research of the cultural and environmental contributions of acequias; and promoting the interests in tourism in acequia communities. Key words: Nonmarket valuation, stakeholder, agriculture, acequias


1. Introduction

Acequia comes from the Arabic word “saqiya,” or water conduit, and refers to irrigation canals originally used in Iberia by Arab farmers. The technique, which diverts water from rivers to agricultural fields, was introduced in New Mexico by Spanish colonizers several hundred years ago (Brown and Rivera, 2000). Through the present day, acequias have been collectively owned and democratically governed by members of the acequias de común. Mayordomos (ditch bosses) are democratically appointed to provide executive leadership for community maintenance of the acequias, and to oversee the distribution of acequia water (Rivera, 1998). With the scarcity of water and frequency of droughts due to the desert climate, the early development of villages and towns in New Mexico relied heavily on water from acequias to grow maize, vegetables, and other crops.

During the 1900s, with the arrival of new economic and development opportunities, acequias became less important for providing the survival

needs of New Mexico’s communities. In the last several decades, the output from acequia agriculture production has had much less value than the productivity achieved when acequia land and water is used for urban development, industrial production, and other economic activities (Rivera and Martinez, 2000). Additionally, increased environmental demands for water to be used to maintain river flows have called into question the continued utilization of water for acequias. Despite these pressures, over 1000 acequias continue to operate in New Mexico (Brown and Rivera, 2000). Many stakeholders advocate that the cultural significance of acequias is reason enough to support their existence. Further, it is suggested that acequias provide important environmental contributions, including buffering against floods, contributing to riparian habitat, and adding to the recharge of groundwater systems (Brown and Rivera, 2000). The objective of this research is to explore and understand the context in which acequias provide value through their nonmarket cultural and environmental attributes, and to identify measures that may lead to increases in this value.


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Economists classify environmental and cultural attributes as nonmarket goods, which do not have prices and cannot be traded in a traditional market place. Valuation studies are carried out to name a monetary figure to represent society’s willingness-to-pay (WTP) for nonmarket goods. Valuation techniques have traditionally been used to capture the nonmarket value of environmental goods, although the techniques have been expanded to capture the value of cultural and agriculture amenities. Brunstad et al. (1999) suggested that the total value of agriculture should not only include the market value of products produced, but also take into account agriculture landscape amenities, such as open space and tree cover, the security of food production capacity, and the preservation of rural communities and rural lifestyles. Understanding the full value of agriculture production, beyond solely the market value of agricultural output, can be used to weigh the costs and benefits to society of policy measures that impact agricultural production.

There have been a number of previous nonmarket valuation studies of agriculture landscapes, several are mentioned here. Hedonic pricing studies have determined that the presence of agricultural open space, pastureland, and irrigation water increased property values and rents of nearby residences, while the presence of large animal farms decreased the value of these nearby properties (Faux and Perry, 1999; Ready and Abdalla, 2005). Employing the contingent valuation method (CVM), surveys have asked respondents their WTP for hypothetical changes to a landscape that could potentially impact the existing agricultural attributes, such as the amount of grazing land utilized, or the chosen conservation and land management strategies (Berrens et al., 1998; Schlapher and Hanley, 2003).

The primary purpose of nonmarket valuation studies is to discover a quantitative value for nonmarket goods. However, valuation studies have been criticized for not including input from organizational structures that have specific interests in, and knowledge of, the nonmarket good in question. It is argued that there is a need to analyze the key stakeholders, institutions, and agencies that are interconnected with the good to fully understand the context in which nonmarket values are perceived by society (Kontogianni, et al., 2001). Stakeholder analyses have become increasingly popular tools for evaluating the role various stakeholders have in influencing policy (Brugha and Varvasovszky, 2000). Ecological modernization studies use stakeholder analyses to understand the political ecology of an industry, to determine strategies for integrating policies and activities that promote principles of sustainability in the industry (Archambault, 2004). The contribution of this research is to use a stakeholder analysis to qualitatively explore the context with which environmental and cultural attributes of traditional agriculture practices are deemed valuable by society. This analysis is then

used to identify management and policy initiatives that increase the value of these attributes. 2. Case Study: Acequia stakeholder analysis

The stakeholder analysis carried out for this study relied primarily on secondary data collected from academic journal articles, as well as government and non-government policy and report documents. Meetings were carried out with members of New Mexico’s legislative finance committee, Think New Mexico, and academic researchers. Other agencies were contacted via email. The primary purpose of this communication was to verify interpretation of the documents reviewed.

2.1. Governmental agencies

A brief database search of New Mexico state law turns up a number of rules that pertain to the operation, maintenance, preservation, or water rights of acequias (NMCC, 2007). In 2005, the state government put in place the Strategic Water Reserve, which allows the state to buy or lease water rights from users to ensure rivers and streams have the legally required quantities of water to be delivered to nearby states, and to maintain levels needed by endangered river ecosystems (New Mexico, 2005). Under the law, the Interstate Stream Commission (ISC) is given the power to purchase or lease water rights from willing sellers for a price no greater than the appraised market value. However, the policy does not allow water to be purchased from acequia communities. Additionally, state and federal funds are available for acequia rehabilitation and improvement projects. In 2004, the state’s funding share to these projects was $2.4 million (ISC, 2004).

One of the major players for water use in New Mexico are the quasi-government irrigation districts that regulate and distribute water according to the state’s established doctrine of prior appropriation, whereby those who have been using the water the longest have the most senior water rights (Thompson, 1986). This hierarchy means that users with junior rights may not receive water in times of low supply. The Middle Rio Grande Conservancy District (MRGCD) was created in the early 1900s through the incorporation of seventy-nine independent acequia communities who recognized the need to coordinate the use of water from the Rio Grande (MRGCD, 2007). However, with the rapid development of urban and industrial centers, the MRGCD must now balance the various demands placed on this surface water (Thompson, 1986). Because acequia communities collectively hold senior water rights, the MRGCD and other irrigation districts must give them higher priority for water delivery.

The exemption for acequias in the Strategic River Reserve, the funds provided annually to acequias, and the mechanism of protecting senior water rights indicates that the state recognizes that acequias have value to New Mexico. The support

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provided by the state ensures acequias are able to continue their operations.

2.2. Local development

Local city governments have to contend

directly with the conflicting demands on water and land resources from acequias and urban development. One example of balancing growth and acequia cultural preservation is seen in the agricultural village of Los Lunas, located just south of large city of Albuquerque. Los Lunas has relied on acequias for many generations, but now faces pressure to develop residential communities for its rapidly growing population. The Los Lunas comprehensive plan emphasizes the need for a mode of development that maintains their agricultural heritage (Los Lunas, 1999). The interest and struggles of communities to maintain acequias despite development pressures, underscores the presence of a cultural value held for acequias.

2.3. Policy advocacy groups

There are different special interest groups, think tanks, and policy lobbyists who advocate for specific policy objectives that concern acequias. Think New Mexico is an advocacy organization that was extensively involved in promoting the implementation of the strategic water reserve, and lobbied for acequias to be exempt from transferring water to the reserve. Their policy documents call attention to the unique social, cultural, and ecological benefits of acequias that would be damaged if the reserve policy transferred water away from acequias. They mention the millions of dollars New Mexico is able to generate from tourists who come to experience the state’s cultural heritage, of which acequias play a visible role (Think New Mexico, 2003).

Another advocacy group is the New Mexico Acequia Association (NMAA). NMAA was founded in 1990 to serve as a platform for expressing the common concerns and goals of acequia communities around the state. Acequia users and other interested parties pay dues to have membership in the NMAA. The association organizes people and resources to meet goals, provide education, and advocate for policies that are in the interest of acequia communities. The association particularly calls attention to its mission of sustaining the acequia culture and traditions, protecting water as a community resource, and maintaining the ability to grow food (NMAA, 2007).

One category of special interest groups includes those groups with specific interests in promoting environmental issues. The Forest Guardians are particularly vocal about their interest in maintaining healthy river ecosystems. They have concern for the large quantities of water required for some agriculture activities, including the growing of alfalfa, which many modern acequia communities produce (Forest Guardians, 2007). However, many

environmental advocacy groups do not promote the termination of acequia culture. Instead, they emphasize the contribution acequias make to the cultural landscape, and propose ways that acequias could be managed in the most environmentally feasible manner, so there is water available for both acequias and instream flows. Possible techniques include growing valuable crops that use less water (Brown and Rivera, 2000). A series of environmental organizations, including Forest Guardians, made a statement in 2000, saying that increasing the efficiency of agriculture irrigation is the most effective way to increase river flows and maintain river habitats (Alliance for the Rio Grande Heritage et al., 2000). This statement indicates that acequias have a potentially valuable role to play in managing New Mexico’s scarce water resources. 2.4. Religious organizations

Historically, the predominant religious

institution in New Mexico is the Roman Catholic Church. There is evidence in activities of the Church that highlights the cultural significance of acequias. The Archdiocese of Santa Fe has an Ecology Ministry through their Peace and Social Justice Office, which advocates for acequia communities. Along with community and environmental organizations, such as Amigos Bravos, the Church is involved with the annual Fiesta de San Isidro, where acequias are blessed and a traditional Catholic Mass is held (Amigos Bravos, 2007). The work of the Church to support and advocate for acequia culture represents the Church’s recognition that acequias contribute value to New Mexico communities. 2.5. Academic research

Academic research also gives some insight

into the cultural value of acequias. The hypothesis is that if there are large numbers of researchers involved with studying acequia culture and activity, one might conclude that acequia culture has a level of importance in New Mexico. Social research concerning acequias has included acequia history and culture (Rivera, 1998), acequia legal structure (Delara, 2000), and efficiency, equity and shared resource studies (Klein-Robbenhaar, 1996).

3. Discussion and policy implications

This analysis has indicated that stakeholders

look beyond market economics, and assign value to acequias based on their unique social structure, cultural and traditional heritage, and actual and potential environmental contributions. There are also characteristics of acequias that may diminish their nonmarket value, including interference with urban and industrial development, as well as inefficient use of water. There is specific environmental concern that acequias leave less water available for endangered river ecosystems.

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The stakeholder analysis allows for the identification of points of intervention where policy measures or activities can be implemented to strengthen the cultural and environmental attributes of acequias. Through the government’s support of acequia rehabilitation, methods could be introduced that decrease acequia water consumption. The government could support lining the acequias to minimize seepage, or fund the removal of non-native trees that consume large amounts of water along acequia banks. The government and policy groups, such as NMAA and environmental organizations, should encourage acequias to grow crops that are less water intensive. These organizations may aim to educate farmers about such subjects as drip irrigation and other techniques that would reduce the water needed for crops. Improving their environmental performance is likely to cause stakeholders and the general public to increase the value they assign to acequias.

Increases in the cultural value achieved from acequias may be wrought through the promotion of tourism that focuses on New Mexico’s acequia cultural heritage. Tourism could further promote the benefits of the riparian habitats associated with acequias, bringing visitors to view birds and other wildlife that are found in the bosque habitat. Such improvements may also bring added value to the residential neighborhoods that exist or are being planned near acequias. Developers may recognize the benefit of maintaining the environmental and cultural attributes of acequias, to increase the value of their development projects.

The nonmarket values of acequias are likely to increase if society is more familiar with the environmental and cultural contributions acequias provide. This could be achieved through educational and promotional efforts, and through the sponsorship of academic research focused on acequias.

4. Conclusions

Infrastructure changes, the promotion of

tourism, and educational activities are likely to require additional investment by the government and other organizations. A quantitative study of acequia nonmarket value could assist in determining society’s WTP for acequias, through increased taxes, fees, or other payment vehicles. The current dollar figure spent by the government to support acequias may be either below or above society’s WTP. An actual WTP value would assist the state in designing a more accurate budget for acequia support. A hedonic study may assist developers in adjusting their projects to account for additional revenue they may receive from striving to maintain acequias within their urban development projects. A travel cost study may indicate the WTP of tourists for certain acequia cultural and landscape amenities when they visit New Mexico.

The stakeholder analysis approach is useful for unraveling the complexities that may exist in valuing

an activity or policy. It draws attention to those potentially competing stakeholder preferences for nonmarket goods. In this study, stakeholders are seen to recognize a non-market value of acequias. However, the actual monetary value placed on acequias by the government, local developers, members of the Church’s ecological ministry, environmental groups, and other stakeholders is likely to vary. Such context is useful for fully interpreting nonmarket valuation estimates. Understanding the value preferences of individual stakeholders allows for policy and management decisions that may lead the way to strengthened cultural and environmental attributes to maximize the utility of all stakeholders. References Alliance for the Rio Grande Heritage, (2000), Forest

Guardians, Rio Grande Restoration, Defenders of Wildlife, Land and Water Fund of the Rockies, Amigos Bravos, Diverting the Rio Grande: Inefficient, wasteful and illegal water use by the MRGCD, On line at: http://www.fguardians.org/support_docs/report_rio-grande-diversions_4-21-00.pdf.

Amigos Bravos, (2007), Fiesta de San Isidro & blessing of the waters, Amigos Bravos Bulletin, Spring, On line at: http://www.amigosbravos.org/docs/bulletin/07 bulletin/BulletinSpring2007.pdf.

Archambault S., (2004), Ecological modernization of the agriculture industry in southern Sweden: reducing emissions to the Baltic Sea, Journal of Cleaner Production, 12, 491-503.

Berrens R., Brookshire D., Ganderton P., McKee M., (1998), Exploring nonmarket values for the social impacts of environmental policy change, Resource and Energy Economics, 20, 117-137.

Brugha R., Varvasovszky Z., (2000), Stakeholder analysis: A review, Health Policy and Planning, 15, 239-246.

Brunstad R., Gaasland I., Vardal E., (1999), Agricultural production and the optimal level of landscape preservation, Land Economics, 75, 538-546.

Faux J., Perry G., (1999), Estimating irrigation water value using hedonic price analysis: A case study in Malheur County, Oregon, Land Economics, 75, 440-452.

Forest Guardians, (2007), Agriculture water use: The key to living rivers, On line at: http://www.fguardians.org/sr/index.asp.

Interstate Stream Commission, (2004), Annual report 2003-2004, New Mexico Office of the State Engineer, On line at:, http://www.ose.state.nm.us/publications/03-04-annual-report/03-04-AnnualReport.pdf.

Kontogianni A., Skourtos M., Langford I., Bateman I., Georgiou S., (2001), Integrating stakeholder analysis in non-market valuation of environmental assets, Ecological Economics, 37, 123–138.

Los Lunas, (1997), Los Lunas Comprehensive Plan, Village of Los Lunas, New Mexico.

Middle Rio Grande Conservancy District (MRGCD), (2007), Albuquerque, New Mexico, On line at: http://www.mrgcd.org.

New Mexico Acequia Association (NMAA), (2007), On line at: http://www.lasacequias.org.

New Mexico, (2005), Interstate stream commission, additional powers: strategic water reserve, NM Statute 72-14-3.3.

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New Mexico Compilation Commission (NMCC), (2007), New Mexico One Source of Law, State of New Mexico, On line at: http://www.conwaygreene.com/nmonesource/publicLicense.aspx?dest=cg.

Ready R., Abdalla C., (2005), The amenity and disamenity impacts of agriculture: Estimates from a hedonic pricing model, American Journal of Agricultural Economics, 87, 314-26.

Rivera J., (1998), Acequia Culture: Water Land and Community in the Southwest, Albuquerque, New Mexico, 49-62.

Rivera, J., Brown, J., (2000), Acequias de Común: The tension between collective action and private property rights, International Association for the Study of Common Property, Proceedings, Bloomington, Indiana, May 31-June 4, On line at: http://eprints2.dlib.indiana.edu/archive/00000227/00/rivieraj041300.pdf.

Rivera, J., Martinez, L., (2000), Acequias de común and sustainable development: reflections from the upper Rio Grande watershed, Congreso Nacional: Gestión del Agua en Cuencas Deficitarias, October 5, Universidad Miguel Hernández, Orihuela, Spain.

Schlapfer, F., Hanley, N., (2003), Do local landscape patterns affect the demand for landscape amenities protection?, Journal of Agricultural Economics, 54, 21–35.

Think New Mexico, (2003), Rio Vivo! The need for a strategic river reserve in New Mexico, Policy Publication, Santa Fe, New Mexico.

Thompson, S., (1986), Urbanization and the Middle Rio Grande Conservancy District, Geopgraphical Review, 76, 35-50.



______________________________________________________________________________________________

METALS CONCENTRATION IN SOILS ADJACENT

TO WASTE DEPOSITS

Camelia Drăghici1, Elisabeta Chirilă2∗, Narcisa Elena Ilie2

1Transilvania University of Brasov, 29 Eroilor Blvd. 500036 – Brasov, Romania

2“Ovidius” University, Chemistry Department, 124 Mamaia Blvd., 900527 Constanta, Romania

Abstract The paper presents original results concerning concentrations of eight heavy metals in soils adjacent to two improperly built municipal waste deposits located in Eforie Sud and Techirghiol, Constanta County, Romania. Measurements have been done on surface and depth soils, during April-October 2006. The applied analytical technique for metal determination was flame atomic absorption spectrometry (FAAS). The mean measured values ranged as follows (in mg/kg dry weight): Cd: 0.09 – 0.15; Co: 7.92 - 9.27; Cr: 11.37 – 13.86; Cu: 16.91 – 20.92; Mn: 379 – 441; Ni: 20.58 – 28.95; Pb: 7.24 – 9.08 and Zn: 44.28– 49.93. Except nickel all other metals concentrations have been founded below the accepted limits by the Romanian regulations. As a general observation, in depth soil samples the concentrations were higher for Cr, Cu, Ni and Pb, or similar for Mn, Zn, than in surface samples. Cadmium and cobalt have different concentration evolution between depth and surface samples, in the studied locations. Key words: heavy metals, soils, FAAS, waste deposits


1. Introduction

Soils and sediments are the solid components of terrestrial and aquatic ecosystems which serve as sources and sinks for nutrients and solid chemicals. The use of soils for industrial, agriculture and urban activities always involves a drastic modification of their composition and can eventually create enormous problems for its future use, involving high capital investments and health risks. (Manea, 2004).

Soil pollution is defined as the build-up in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease causing agents, which have adverse effects on plant growth and animal health. The degree of antropogenous effect of metal cycles can be represented as a global interference factor: it indicates the ratio of the antropogenously-induced amount of material to that of the natural (geochemical) material cycle. Processes in the geochemical cycle that are common are equilibriums of dissolution-precipitation, the transition of metal compounds in aerosols and the

return to the soil and water via precipitations (Schwedt, 2001).

The term municipal solid waste (MSW) is used to describe most non-hazardous solid waste from a city, town or village that requires routine collection and transport to a processing or disposal site. MSW is not generally considered hazardous. But certain types of commercial and industrial wastes like those poisonous, explosive or dangerous can cause immediate and direct harm to people and the environment if they are not disposed of properly. Soil contamination as well as surface water and ground water pollution can be caused by the disposal of solid waste in improperly built landfills. These kinds of pollution problems can have important public health consequences (Manea, 2003). In “typical European household waste”, batteries contained 93% of the mercury and 45% of cadmium, ferrous metals accounted for about 40% of the lead, the fine (<20mm) fraction contained 43% of the copper and 20% of the lead, and plastics contained 38% of the cadmium. A recent study revealed that the heavy metal content of the different fractions of household


Draghici et al. /Environmental Engineering and Management Journal 6 (2007), 6, 497-503

498

waste tended to be concentrated in the metal wastes, batteries and electronic equipment and tended to have elevated concentrations of cadmium compared to the other fractions in plastics (Burnley, 2007).

Heavy metals or trace metals is the term applied to a large group of trace metals which are both industrially biologically important. Agricultural productivity can be limited by deficiencies of essential trace elements such as Cu, Mn and Zn in crops and Co, Cu, Mn and Zn in livestock. However, when are presented in excessive concentrations, certain heavy metals give rise to concern with regard to human health and agriculture (Dobra and Viman, 2006; Statescu and Cotiusca-Zauca, 2006) and their accurate analytical determination remains a challenge for chemists (Anderson, 1999; Baiulescu et al., 1990; Crompton, 2001; Draghici et al., 2003). The purpose of this paper is to present original results concerning concentrations of eight metals in soils adjacent to Eforie Sud and Techirghiol improperly built municipal waste deposits located in Constanta County, Romania, in April-October 2006. 2. Experimental

Total Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn

concentrations in soils using flame atomic absorption spectrometry (FAAS) have been determined.

Adjacent soils of two improperly built landfills located in Constanta County, Romania have been analysed: Eforie Sud waste deposit, corresponding to 8650 people and Techirghiol waste deposit which corresponds to 7150 people.

In order to determine metals concentration from soils, five samples were collected using a special device from the surface and depth of 20-40 cm from each location at 1 – 2.5 m distance of the landfill boundary between April and October 2006 (Chirila, 2004). Mean samples from surface and depth have been obtained each month by the appropriate omogenization of collected samples, previously dried for 16 hours at room temperature.

To obtain soil solutions, 3 grams of soil sample has been extracted with aqua regia in 250 mL volumetric flask (ISO 11466). The supernatant, the filtrate and the washing solution have been collected in 100 mL calibrated flask (Chirila and Draghici, 2003).

The spectrometric measurements have been done using a flame atomic absorption spectrometer Spectr AA220, provided by Varian Company. Analyses have been done in triplicate and the mean values are reported.

For the background correction, the zero calibration solution was done using aqua regia and deionised water (for Cd, Co, Cu, Ni, Pb and Zn); for Cr and Mn, the zero calibration solution was prepared by adding of 3.7 mg/L La, using a lantanum chloride solution. All used reagents were of spectral purity grade.

3. Results and discussions

Heavy metals existence in the soil can be explained by the natural concentration of (that depends on the soil type and its composition) and by soil contamination with heavy metals, provided by human activity. Soil pollution with heavy metals can be available from infiltration of highly contaminated storm water.

The studies were performed in order to observe the heavy metal concentration evolution in adjacent soils to solid waste deposits. Once metals are introduced and contaminate the environment, they will remain. Metals neither are nor degraded like carbon-based (organic) molecules.

The measured concentrations have been compared with the Romanian regulations (Table 2).

Table 2. Regulatory limits for heavy metals in soils (after 756/1997 – Romanian regulation of environment pollution

evaluation)

Concentration, mg/kg dry weight Alert limit Intervention limit

Metal Normal value S NS S NS

Cd 1 3 5 5 10 Co 15 30 100 50 250 Cr 30 100 300 300 600 Cu 20 100 250 200 500 Mn 900 1500 2000 2500 4000 Ni 20 75 200 150 500 Pb 20 50 250 100 1000 Zn 100 300 700 600 1500

S- sensible utilization, NS non-sensible Cadmium concentration in soil depends on

the geological origin of the parent material, texture, intensity of weathering processes, organic matter and other factors. Cadmium enters the soil in smaller quantities than lead and it reach the soil through air. It is derived from incinerator exhaust gases and from phosphate fertilizers. Generally, in acidic soils with pH<6, Cd is very mobile and does not accumulate. Compounds with humic acids are less stable. Under reductive conditions and in presence of sulfate ion, CdS is formed. The mean reported Cd concentration in lithosphere is 0.1 mg/kg dry weight. Fig. 1 presents the evolution of cadmium concentration in the studied soil samples.

In Eforie Sud soil samples Cd concentration ranged between 0 - 0.9 mg/kg dry weight in surface samples and 0 – 0.46 mg/kg dry weight in depth samples. Soil samples from Techirghiol registered lower Cd concentrations (0 – 0.54 mg/kg dry weight in surface samples and 0 – 0.37 mg/kg dry weight in depth samples). All determined Cd concentrations were below the normal limit in soil.

Cobalt is a trace component in the earth’s crust (0.003%), an element that occurs naturally in many different chemical forms throughout our environment. Cobalt usually occurs in association with other metals such as copper, nickel, manganese and arsenic. Natural sources of cobalt in the

Metals concentration in soils adjacent to waste deposits

499

environment are soil, dust, seawater, volcanic eruptions and forest fires. All soil contains some amount of cobalt. The average concentration of cobalt in soils around the world is 8 mg/kg dry weight. Toxic effects on plants are unlikely to occur below soil cobalt concentrations of 40 ppm. One of the most important soil properties is soil acidity. The more acidic the soil, the greater are the potential for cobalt toxicity, at any concentration.

Fig. 1. Cadmium concentration evolution in soil adjacent to

waste deposits in April-October 2006 (mean values, mg/kg dry weight); a) Eforie Sud; b) Techirghiol

The cobalt concentration evolution in studied

soil samples are presented in the Fig. 2. All founded values are lower than 15 mg/kg

dry weight, the normal Co concentrations in soil. Chromium is a trace component in the earth’s

crust (0.02%), a unique element in soil, because of essentiality to human and animal life and non-essentiality for the vegetable kingdom and its possible presence in two main oxidation forms, trivalent and hexavalent which show opposite properties. The reported mean total chromium concentration in lithosphere is 69 mg/kg dry weight. The two forms have completely different effects on living organisms: the first Cr(III) is apparently useful or harmless at reasonable concentrations, while the second Cr(VI) is extremely toxic. In addition, Cr(III) is not mobile in soil, therefore the risks of leaching are negligible, while Cr(VI), mainly present in the forms of chromates (CrO4

2−) and dichromates (Cr2O72−), is

generally mobile and often is part of crystalline minerals.

02468

10121416

Co c

onc.

, mg/

kg

d.w

.

Apr Iun Aug Oct

month

a)

surface

depth

02468

101214

Co

conc

., m

g/kg

d.w

.

Apr Iun Aug Oct

month

b)

surfacedepth

Fig. 2. Cobalt concentration evolution in soil adjacent to


Conversion of Cr(III) to Cr(VI) has been

shown in some particular soils: rich in manganese oxides, poor in organic matter and high redox potential. On the contrary, the reverse transformation of Cr(VI) to Cr(III) is very common and easier, so that it is difficult to find hexavalent chromium forms in soil solution or in leaching waters. The problem of Cr enrichment in soil has been often discussed not only in relation to the discharge of tannery wastes, but also to the possibility of Cr presence in soil amendments, mainly organics, and to the existence of excellent organic fertilizers produced from leather residues or wastes.

Fig. 3 presents the mean total chromium concentration in studied soil samples.

In Eforie Sud soil samples Cr concentration ranged between 3.24 – 28.72 mg/kg dry weight in surface samples and 7.25 – 30.06 mg/kg dry weight in depth samples. Soil samples from Techirghiol registered similar Cr concentrations (7.50 – 28.55 mg/kg dry weight in surface samples and 8.40 – 19.32 mg/kg dry weight in depth samples). All determined Cr concentrations were below the normal limit in soil.

Copper is also a trace element in the earth’s crust (0.007%); Cu is among the trace elements essential for life, in the case of plants toxic effects occur at 20 or more mg/kg dry weight. In the past, the


500

major source of Cu pollution was smelters that contributed vast quantities of Cu–S particulates to the atmosphere.

0

5

10

15

20

25

30

Cr c

onc.

, mg/

kg d

.w.

Apr May Iun Iul Aug Sept Oct

month

a)

surface

depth

0

5

10

15

20

25

30

Cr c

onc.

, mg/

kg d

.w.


month

b)

surfacedepth

Fig. 3. Chromium concentration evolution in soil adjacent to waste deposits in April-October 2006 (mean values,

mg/kg dry weight); a) Eforie Sud; b) Techirghiol

Presently, the burning of fossil fuels and waste incineration are the major sources of Cu to the atmosphere and the application of sewage sludge, municipal composts, pig and poultry wastes are the primary sources of anthropogenic Cu contributed to the land surface. The amount of Cu available to plants varies widely by soils.

Available Cu can vary from 1 to 200 ppm (parts per million) in both mineral and organic soils as a function of soil pH and soil texture. Availability of Cu is related to soil pH and texture. As soil pH increases, the availability of this nutrient decreases and the finer-textured mineral soils generally contain the highest amounts of Cu. Copper is not mobile in soils, being attracted to soil organic matter and clay minerals. Toxic at high doses, excess Cu can lead to Zn deficiencies and vice-versa.

Fig. 4 presents the mean copper concentration in studied soil samples.

In Eforie Sud soil samples Cu concentration ranged between 15.80 – 21.75 mg/kg dry weight in surface samples and 13.37 – 47.60 mg/kg dry weight in depth samples. Soil samples from Techirghiol registered similar Cu concentrations (15.80 – 19.25 mg/kg dry weight in surface samples and 16.25–

22.11 mg/kg dry weight in depth samples). The determined Cu concentrations in Eforie Sud soils sometimes slowly exceeded the normal limit in soil. Another observation consists in the fact that copper concentration is higher in depths samples than in the surface samples in both locations.

0

10

20

30

40

50

Cu

conc

., m

g/kg

d.w

.


month

a)

surfacedepth

0

5

10

15

20

25C

u co

nc.,

mg/

kg d

.w.

Apr Iun Aug Oct

month

b)

surfacedepth

Fig. 4. Copper concentration evolution in soil adjacent to


Manganese is a less abundant major

component (0.1%) in the earth’s crust. The major anthropogenic sources of environmental manganese include municipal wastewater discharges, sewage sludge, mining and mineral processing (particularly nickel), emissions from alloy, steel, and iron production, combustion of fossil fuels, and, to a much lesser extent, emissions from the combustion of fuel additives. Mean reported Mn concentration in soils is 300–600 mg/kg dry weight. Availability of Mn increases as soil pH decreases. Soils with a high organic matter and neutral pH will be low in Mn. As the organic matter increases the complexing of Mn with organic matter also increases. Soils high in organic matter will usually be low in available Mn. The role of Mn in plants was discovered in 1922. It is essential for photosynthesis, production of chlorophyll and nitrate reduction. Plants which are deficient in Mn exhibit a slower rate of photosynthesis by as much as half of a normal plant.

Plants which are low in Mn causes other metals such as iron to exist in an oxidized and


501

unavailable form the reduced form of metals are available for metabolism.

The mean manganese concentrations in studied soil samples are presented in the Fig. 4.

In Eforie Sud soil samples Mn concentration ranged between 235 – 665 mg/kg dry weight in surface samples and 247 – 628 mg/kg dry weight in depth samples.

0100200300400500600700

Mn

conc

., m

g/kg

d.

w.

Apr Iun Aug Oct

month

a)

surfacedepth

0100200300400500600700

Mn

conc

., m

g/kg

d.

w.

Apr Iun Aug Oct

month

b)

surfacedepth

Fig. 5. Manganese concentration evolution in soil adjacent

to waste deposits in April-October 2006 (mean values, mg/kg dry weight); a) Eforie Sud; b) Techirghiol

Soil samples from Techirghiol registered

higher Mn concentrations (343 – 684 mg/kg dry weight in surface samples and 382 – 616 mg/kg dry weight in depth samples). All founded values are lower than the normal Mn concentrations in soil.

Trace component on the earth’s crust (0.008%), nickel combined with other elements occurs naturally in the earth's crust, is found in all soils, and is also emitted from volcanoes. Nickel compounds are used for nickel plating, to color ceramics, to make some batteries, and as substances known as catalysts to increase the rate of chemical reactions. Nickel may be released to the environment from the stacks of large furnaces used to make alloys or from power plants and trash incinerators.

Soil generally contains between 4 and 80 mg/kg dry weight nickel. The highest soil concentrations (up to 9.000 ppm) are found near industries where nickel is extracted from ore. High concentrations of nickel occur because dust released from stacks during processing settles out of the air.

Nickel is essential to maintain health in animals. Although a lack of nickel has not been found to affect the health of humans, a small amount of nickel is probably also essential for humans. Fig. 6 presents the mean nickel concentration in studied soil samples.

0

5

10

15

20

25

30

35

Ni c

onc.

, mg/

kg d

.w.


month

a)

surface

depth

0

10

20

30

40

50

Ni c

onc.

, mg/

kg d

.w.


month

b)

surfacedepth

Fig. 6. Nickel concentration evolution in soil adjacent to


In Eforie Sud soil samples Ni concentration

ranged between 16.62 – 26.55 mg/kg dry weight in surface samples and 15.68 – 30.95 mg/kg dry weight in depth samples. Soil samples from Techirghiol registered higher Ni concentrations (11.30 – 28.55 mg/kg dry weight in surface samples and 15.44 – 49.47 mg/kg dry weight in depth samples). The determined Ni concentrations in both analyzed soils sometimes exceeded the normal limit in soil. Another observation consists in the fact that generally nickel concentration is higher in depths samples than in the surface samples.

Lead is a trace component in the earth’s crust; the average reported lead concentration in the lithosphere is 14 mg/kg dry weight. The most important environmental sources for Pb are gasoline combustion (presently a minor source, but in the past 40 years a major contributor to Pb pollution), Cu–Zn–Pb smelting, battery factories, sewage sludge, coal combustion, and waste incineration.

Lead exhibits a pronounced tendency for accumulation in the soil, because it is minimally mobile even at low pH value. High levels of lead pollution still occur in the vicinity of industrial


502

facilities and waste incinerators that have insufficient elimination of suspended dust.

The mean lead concentrations in studied soil samples are presented in the Fig. 7.

02468

101214

Pb c

onc.

, mg/

kg

d.w

.

Apr Iun Aug Oct

month

a)

surfacedepth

02468

1012141618

Pb c

onc.

, mg/

kg d

.w.

Apr Iun Aug Oct

month

b)

surfacedepth

Fig. 7. Lead concentration evolution in soil adjacent to


In Eforie Sud soil samples Pb concentration

ranged between 4.69 – 12.40 mg/kg dry weight in surface samples and 5.98 – 11.42 mg/kg dry weight in depth samples. Soil samples from Techirghiol registered higher Pb concentrations (1.02 – 16.27 mg/kg dry weight in surface samples and 5.05 – 17.93 mg/kg dry weight in depth samples).

Lead concentration is generally higher in depths samples than in the surface samples and all determined values are lower than the normal Pb concentrations in soil.

Zinc is an essential element, a trace component in the earth’s crust (0.013%); the average reported Zn concentration in lithosphere is 80 mg/kg dry weight. Zinc occurs naturally in air, water and soil, but zinc concentrations are rising unnaturally, due to addition of zinc through human activities. Most zinc is added during industrial activities, such as mining, coal and waste combustion and steel processing.

Zinc is one of the most mobile metals in the soil. The solubility of zinc in soil increases especially at pH <6. At higher pH and in the presence of phosphates, the zinc appropriated by plants can be

significantly reduced. Fig. 8 presents the mean zinc concentration in studied soil samples.

0

20

40

60

80

100

Zn c

onc.

, mg/

kg

d.w

.

Apr Iun Aug Oct

month

a)

surfacedepth

01020304050607080

Zn c

onc.

, mg/

kg d

.w.


month

b)

surfacedepth

Fig. 8. Zinc concentration evolution in soil adjacent to


In Eforie Sud soil samples Zn concentration

ranged between 28.27 – 96.14 mg/kg dry weight in surface samples and 23.16 – 88.80 mg/kg dry weight in depth samples. Soil samples from Techirghiol registered lower Zn concentrations (29.70 – 79.08 mg/kg dry weight in surface samples and 31.64– 66.18 mg/kg dry weight in depth samples). All determined Zn concentrations were below the normal limit in soil.

4. Conclusions

Eight metal concentrations (Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) determination in soils adjacent to improperly built municipal solid waste deposits from Constanta County has been done using FAAS technique.

The mean measured values ranged as follows (in mg/kg dry weight): for cadmium between 0.09 – 0.15 in surface samples and 0.09 – 0.11 in depth samples; for cobalt between 9.02 – 9.11 in surface samples and 7.92 – 9.27 in depth samples; for chromium between 11.37 – 13.46 in surface samples and 12.45 – 13.86 in depth samples; for copper between 16.91 – 17.55 in surface samples and 19.65 – 20.92 in depth samples; for manganese between 385 – 425 in surface samples and 379 – 441 in depth samples; for nickel between 20.58 – 23.52 in surface


503

samples and 20.90 – 28.95 in depth samples; for lead between 7.24 – 8.94 in surface samples and 7.90 – 9.08 in depth samples and for zinc between 44.55 – 47.71 in surface samples and 44.28– 49.93 in depth samples.

Except nickel all other metals concentrations have been founded below the normal limits from Romanian regulations. As a general observation, in depth soil concentrations are higher (Cr, Cu, Ni, Pb) or similar (Mn, Zn) than in surface samples. Cadmium and cobalt have different concentration evolution between depth and surface samples in studied locations. References Anderson K.A., (1999), Analytical Techniques for

Inorganic Contaminants, AOAC International. Baiulescu G.E., Dumitrescu, P., Zugrăvescu Gh., (1990),

Sampling, Ellis Horwood London. Burnley S.J., (2007), The use of chemical composition data

in waste management planning – A case study, Waste Management, 27, 327-336.

Chirila E., Draghici C., (2003), Pollutants analysis. I. Water Quality Control (in Romanian), Transilvania University Press, Brasov, Romania.

Chirila E., (2004), Sampling, In: Colbeck I., Drăghici C., Perniu D., (Eds), Polution and Enviromental

Monitoring, The Publishing House of the Romanian Academy, Bucharest, 109-128.

Crompton T.R., (2001), Determination of Metals and Anions in Soils, Sediments and Sludges, Spon Press, Taylor & Francis Group.

Dobra M., Viman V., (2006), Determination of the concentration of heavy metals in soils and plants by ICP-MS, Environmental Engineering and Management Journal, 5, 1197-1203.

Draghici C., Coman Gh., Sica M., Perniu D., Tica R., Badea M., (2004), Capilary electrophoresis for soil analysis, Proceedings Bramat Brasov Romania 2003, 494-501.

ISO 11466 (1995) Soil quality – Extraction of trace elements soluble in aqua regia.

Manea F., (2003), Solid waste management, In: Waste management, Pretty J., Oros V., Draghici C. (Eds), The Publishing House of the Romanian Academy, Bucharest, 87-93.

Manea F., (2004), Soil monitoring, In: Pollution and Environmental Monitoring, Colbeck I, Draghici C., Perniu D., (Eds), The Publishing House of the Romanian Academy, Bucharest, 87-95.

Schwedt G., (2001), The Essential Guide to Environmental Chemistry, John Wiley &Sons, Ltd.

Statescu Fl., Cotiusca-Zauca D., (2006), Heavy metal soil contamination, Environmental Engineering and Management Journal, 5, 1205-1213.



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POLYELECTROLYTE – SURFACTANT COMPLEXES

Mihaela Mihai∗, Gabriel Dabija, Cristina Costache Polytechnica University Bucharest, Faculty of Applied Chemistry and Materials Science, 1 – 7 Polizu Street, Sector 1, 011061

Bucharest, Romania

Abstract The formation of the polyelectrolyte – surfactant complexes has been studied. On this purpose has been measured the critical micelle concentration for every polyelectrolyte and surfactant which had been used. The phase behaviour of mixtures of a cationic polyelectrolyte (Praestol 611) and an anionic surfactant (sodium lauryl sulphate – SLS) has been studied. For a given polyelectrolyte concentration, with increasing surfactant concentration, three phase regions were identified. The first region is a single homogeneous phase. Within this region, at some surfactant concentration, above the critical aggregation concentration (cac), stable open – network ‘particles’ form, typically 100 nm in size, which are net positively charged. However, as the surfactant concentration is increased further, these particles aggregate and form a two – phase system: a separated gel phase, containing a high percentage of water co-existing with an aqueous surfactant phase. The rheological consequences of interactions of polyelectrolytes with surfactants of the opposite charge are experimentally studied. Key words: polyelectrolyte, surfactant, complex polyelectrolyte – surfactant, rheologie


1. Introduction Polyelectrolytes are used in a number of

technical applications, such as water treatment. With polyelectrolytes can change the surface properties of colloids, rheology of solutions, wettability etc. In particular, cationic polyelectrolytes are used in the water treatment because of their ability to interact with negatively charged surfaces. Using surfactants in combination with polyelectrolytes increases the width of the applications even further, and mixtures of polymers and surfactants in aqueous solution have been used for colloidal stabilization or flocculation as well as rheology control.

The interaction between polyelectrolytes and oppositely charged surfactants can be understood considering electrostatic and hydrophobic interactions (Vautrin, 2006). At low concentrations, the surfactant binds individually to the polyelectrolyte through electrostatic interactions. A cooperative association occurs at the critical aggregation concentration, cac, as the concentration is raised due to hydrophobic interactions between the surfactant tails. This aggregation process leads in some cases to a bead-and-necklace type structure, where surfactant

aggregates are located along the polyelectrolyte chain (Bastardo, 2005).

The addition of a simple salt lowers the viscosity of polyelectrolyte solutions because salt screens the electrostatic repulsion that expands the size of the polyelectrolyte. The addition of an equivalent amount of oppositely charged surfactant has a larger effect on viscosity (Abuin and Scaiano, 1986). This is because flexible polyelectrolytes bind to the spherical surfactant micelles by wrapping around the exterior of the micelle, thereby shortening the effective length of the polyelectrolyte chain (Konop, 1997). The polyelectrolyte stabilizes the large charge on the micelle surface and no counterion condensation on the micelle surface is needed (Goddard, 1993). These effects stabilize the spherical micelles, reflected in micelles forming at a much lower concentration when oppositely charged polyelectrolytes are present (Colby, 2000). 2. Experimental

The cationic Praestol 611 is a commercial

denomination of a copolymer of polyacryl amide with acrylic acid. The association between the cationic


Mihai et al. /Environmental Engineering and Management Journal 6 (2007), 6, 505-509

506

polyelectrolyte Praestol 611 and the anionic surfactant sodium lauryl sulphate (SLS) has been studied using the surface tension measurements of the solutions. These are simple measurements that monitor the polyelectrolyte and surfactant aggregates formed in solution.

The rheological study is experimentally studied with cylinder – cylinder rheoviscosimetre Rheotest RV. 3. Results and Discussion

The consequences of interactions of polyelectrolytes with surfactants of the opposite charge are presented in Figs 1 – 6.

From the diagrame analysis of those Figures results that for cSLS < 10-5 % there are polymer – surfactant associations, which significantely reduce the superficial tension of the solution.

At these concentrations neither the polymer nor the surfactant are associated in miceles. It results that the surfactant molecules jointo the polymer – macromolecule and both form associations, based on electrostatic attraction forces. For cSLS > 10-4 % the surfactant molecules are associated in miceles but the macromolecules of polymer are not associated and the complex forms by engraftment of surfactant miceles on the macromolecules polymer. The complex solution superficial tension is lower then the one of the polymer solution. This properties recomend the use of this solution in interfacial liquid – solid processes. The same results are obtained at higher concentration of the polymer solution, while this concentration is lower then the micelar critical concentration.

1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1 1 10 10010

20

30

40

50

60

70

80

90

σ, m

N/m

2

cSLS

c = 1.0 10-5

c = 5.0 10-5

c = 1.0 10-4

c = 4.2 10-3

c = 1.0 10-2

c = 4.2 10-2

Praestol 611, c = 7.5 10-4and SLS complex solutions

Fig. 1. Superficial tension dependence for the aqueous

concentration solutions of the Praestol 611 and SLS complex for different SLS concentration solutions at 20 °C

1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.110

20

30

40

50

60

70

80

90

100

σ, m

N/m

2

cSLS

complex solution between Praestol 611 c = 7.5 10-4 and SLS cSLS = 4.210-3

SLS solution

cca ccsccm

Fig. 2. Superficial tension dependence for the aqueous concentration solutions of the Praestol 611, c = 7.5 10-4 %

and SLS complex for c = 4.2 10-3 % SLS concentration solution at 20 °C

1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.010

20

40

60

80

100σ,

mN

/m2

cSLS, %

c = 1.0 10-5 % c = 5.0 10-5 % c = 1.0 10-4 % c = 4.2 10-3 % c = 1.0 10-2 % SLS solution

Praestol 611 c = 1.2 10-4 and SLS complex solutions

Fig. 3. Superficial tension dependence for the aqueous concentration solutions of the Praestol 611 and SLS

complex for different SLS concentration solutions at 20 °C

1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.010

20

40

60

80

100Praestol 611 c = 1.6 10-3 and SLS solutions

c = 1.0 10-5 % c = 5.0 10-5 % c = 1.0 10-4 % c = 4.2 10-3 % c = 1.0 10-2 % solutie SLS

σ, m

N/m

2

cSLS, %

Fig. 4. Superficial tension dependence for the aqueous concentration solutions of the Praestol 611 and SLS complex for different SLS concentration

solutions at 20 °C

Polyelectrolyte – surfactant complexes

507

At concentrations c > 10-2 of the polymer

solution the formed complex precipitates entering in the heterogeneous zone of complex formation. In the analysed situations the concentrations for aggregation and critical concentration of saturation have the same values for every experiment, cca = 4·10-4 %, and ccs = 4·10-3 %.

The results of the measurements of the rheological study of complex solutions are presented in Figs 5 – 8. Fig. 5 shows that the Praestol 611 solution has the Bingham pseudoplastic behaviour and the rheological model is 46,044,13871,235 γτ &+= .

0 200 400 600 800 1000 1200 14000

1x103

2x103

3x103

4x103

5x103

6x103

Equation: y = a + b*x^c a 235.71b 138.44c 0.46

τ, N

/m2

γ, s-1

going return

Solution of Praestol 611 c = 0,01%

a.

1 10 100 10001

10

100

η, c

P

γ, s-1

going return

Solution of Praestol 611 c = 0,01%

b. Fig. 5. Rheograme of Praestol 611 c = 0.01 % solution at 20

°C in coordonate τ = f(γ) (a) and η = f(γ) (b)

The surfactant admixture in polymer solution in low quantities (Fig. 6a) significantly modifies the rheogram of the polymer solution (the value of apparent viscosity lowers and for a certain value of share rate it raises). The same effect but amplified can be observed for admixture of greater quantities of surfactant (Figs 6a, 7a and 7b).

1 10 100 100010-2

10-1

100

101

102

103

104

105

γ, s-1

τ = f(γ) η = f(γ)

Praestol 611 c = 0.1 and SLS c = 7.0 10-4 complex solution

a.

10 100 100010-2

10-1

100

101

102

103

104

105


γ, s-1

τ = f (γ) η = f(γ)

b.

Fig. 6. Rheograme of complex solution made with Praestol 611 c = 0.01% and SLS concentrations solutions c = 7 10-4

% (a) and c = 1.2 10-3 % (b) The repetition of the experiment at the

increase and decrease of the share rate is presented in Figs 8 – 9. The rheogrames show that under share stress the structure of the polymer surfactant complex restructures.

4. Conclusions

The interaction between polyelectrolytes and oppositely charged surfactants are experimentally studied. At low concentrations, the surfactant binds individually to the polyelectrolyte through electrostatic interactions. A cooperative association occurs at the critical aggregation concentration, cac, when the surfactant aggregates are located along the polyelectrolyte chain.

Mihai et al. /Environmental Engineering and Management Journal 6 (2007), 6, 505-509

508

1 10 100 100010-2

10-1

100

101

102

103

104

105

106


γ, s-1

τ = f(γ) η = f(γ)

a.

1 10 10010-2

10-1

100

101

102

103

104

105


γ, s-1

τ = f(γ) η = f(γ)

b.

Fig. 7. Rheograme of complex solution made with Praestol 611 c = 0.01 %

1 10 100 1000100

101

102

103

104

105


τ, N

/m2

γ, s-1

going return

a.

1 10 100 100010-1

100

101

102

103

104


η, c

P

γ, s-1

going return

b. Fig. 8. Rheograme of complex solution (Praestol 611 c = 0.01 % and SLS c = 1.6 10-3 %) in coordonate τ = f(γ) (a)

and η = f(γ) (b).

1 10 100 1000100

101

102

103

104

105

106


τ, N

/m2

γ, s-1

going return

a.

1 10 1000.1

1

10

100

1000


η, c

P

γ, s-1

going return

b. Fig. 9. Rheograme of complex solution (Praestol 611 c = 0.01% and SLS c = 2,3 10-3 %) in coordonate τ = f(γ) (a)

and η = f(γ) (b)

Polyelectrolyte – surfactant complexes

509

The rheology of polyelectrolyte solutions are

profoundly altered by the presence of surfactants. The addition of an oppositely charged surfactant lowers the viscosity of polyelectrolyte solutions. This is because flexible polyelectrolytes bind to the spherical surfactant micelles by wrapping around the exterior of the micelle. References Abuin E. B., Scaiano J. C., (1984), Exploratory study of the

effect of polyelectrolyte surfactant aggregates on photochemical behavior, J. Amer. Chem. Soc., 106, 6274-6283.

Bastardo L. A., (2005), Self assembly of Surfactants and Polyelectrolytes in Solutions at Interfaces,

PhD.Thesis at the Royal Institute of Technology Stockholm.

Colby R., (2000), Polyelectrolyte interactions with surfactants and proteins, XIIIth International Congress on Rheology, Cambridge, UK, 414-416.

Goddard E. D., Ananthapadmanabhan K. P., (1993), Interaction of Surfactants with Polymers and Proteins, CRC Press, London.

Konop A. J., (1997), Polyelectrolyte Collapse Induced by Aggregation of Oppositely Charged Surfactant, Masters Thesis, Pennsylvania State University.

Konop A.J, Colby R. H., (1999), Role of condensed counterions in the thermodynamics of surfactant micelle formation with and without oppositely charged polyelectrolytes, Langmuir 15, 58-65.

Vautrin C., (2006), Stabilité et Structure d’Agrégats Catanioniques, PhD.Thesis University Versailles Saint-Quentin-en-Yvelines, France.



_____________________________________________________________________________________________

MODELLING OF SORPTION EQUILIBRIUM OF Cr(VI) ON ISOMORPHIC SUBSTITUTED Mg/Zn-Al – TYPE HYDROTALCITES

Laura Cocheci1∗, Aurel Iovi1, Rodica Pode1, Eveline Popovici2

1 “Politehnica” University of Timisoara, Faculty of Industrial Chemistry and Environmental Engineering, 2 Victoriei Sq., 300006 Timisoara, Romania

2“Al. I. Cuza” University of Iasi, Faculty of Chemistry, 11 Copou Blvd., 700506 Iasi, Romania

Abstract This paper dealt with Cr(VI) sorption on isomorphic substituted Mg/Zn-Al – type hydrotalcites under proper working conditions. The prepared samples were named Mg3Al, Mg2ZnAl, Mg1.5Zn1.5Al, MgZn2Al and Zn3Al. The experimental data concerning sorption isotherms were modelled in accordance with four equilibrium equations: Langmuir (L), Freundlich (F), Langmuir-Freundlich (L-F) and Redlich-Peterson (R-P) by using two ways: (i) estimation of qmax, K and n; and (ii) estimation of K and n, for qmax values equal to the experimental maximum uptake value. It was proved that Langmuir-Freundlich model was the best solution for fitting the experimental data. The results also allowed setting up a ranking order of the sorption capacities for the studied hydrotalcites. Key words: equilibrium modelling, hydrotalcites, hexavalent chromium sorption


1. Introduction

Chromium compounds are used in various industries (e.g. textile dying, tanneries, metallurgy, metal electroplating and wood preserving); hence, large quantities of chromium have been discharged into the environment due to improper disposal and leakage (Gheju and Iovi, 2006).

The toxicity of chromium strongly depends on its oxidation state. Although Cr(III) is an essential dietary nutrient, it can be toxic in high doses. Cr(VI) has also been associated with increased incidents of cancers. The different bioavailability and bioactivity between the trivalent and hexavalent species might account for the differences in toxicity (Toxicological Profile of Chromium, 1998).

Several methods are available for chromium ions removal: chemical reduction followed by precipitation, sorption, electrochemical treatment, membrane separation processes and bioremediation.

Sorption is one of the most popular methods for the removal of chromium from wastewaters. The pollutant adsorbs onto the solid adsorbent surface from the effluent with the quantity of the removed

pollutant depending on the adsorption capacity of the sorbent.

Layered double hydroxides (LDHs), also called hydrotalcite-like compounds, constitute a class of lamellar ionic compounds containing a positively charged layer and exchangeable anions within interlayer. The chemical composition of LDHs can be represented by the general formula [MII

1-x MIIIx

(OH)2]x+ [An-x/n . mH2O]x-, shortly noted [MII

R – MIII – A] with R = (1-x)/x , where MII is a divalent cation, MIII a trivalent cation and An- charge compensating anions. MII/MIII molar ratios (denoted R) between 1 and 5 are possible (Kooli et al., 1997; Miyata, 1975). Carbonates are the interlayer anions in the naturally occurring mineral hydrotalcite, which is a member of this class of materials. The decomposition of Mg3Al – CO3 LDH when heated at around 500 °C leads to mixed metal oxides, which are characterized by high specific surface areas and homogeneous dispersion of metal cations. The mixed metal oxides can take up anions from aqueous solution, with concomitant reconstruction of the original layered structure, as expressed by the equations (1) and (2) (Lv et al., 2006):


Cocheci et al. /Environmental Engineering and Management Journal 6 (2007), 6, 511-515

512

Mg1-xAlx(OH)2(CO3)x/2 . mH2O ⎯⎯ →⎯ °C500 Mg1-xAlxO1+x/2 + x/2CO2 + (m+1)H2O (1) Mg1-xAlxO1+x/2+(x/n)An-+(m+1+(x/2)+y)H2O ⎯→⎯ Mg1-xAlx(OH)2(An-)x/2 . mH2O + xOH- (2)

Therefore, the calcined layered double

hydroxides can be used as potential ion exchangers/adsorbents for removal of toxic anions from wastewaters.

This paper focuses on the study of equilibrium removal of chromate ions by isomorphic substituted Mg/Zn-Al – type hydrotalcites. Four equilibrium models are used to fit the experimental data: Langmuir (L), Freundlich (F), Langmuir-Freundlich (L-F) and Redlich-Peterson (R-P). 2. Experimental

Five formulations having various Mg/Zn ratios were obtained from the corresponding nitrates by using the co-precipitation method under low oversaturation (Vaccari, 1998). The five materials were named as follows: Mg3Al, Mg2ZnAl, Mg1.5Zn1.5Al, MgZn2Al and Zn3Al.

The fractions lower than 0.080 mm were used as adsorbent. The samples activation was performed in an oven, at temperatures of 500°C in air, at a rate of 5°C/min for 4 hours. The calcined products were kept in a desiccator over fused CaCl2 in order to avoid adsorption of CO2 and moisture from the atmosphere.

All sorption experiments were performed on activated Mg/Zn-Al hydrotalcite samples. Conic flasks of 100 ml were used to contact 50 mL K2Cr2O7 solutions containing Cr(VI) from 5 to 50 mg/L with the hydrotalcite samples corresponding to a solid : liquid ratio of 1g/L. The initial pH was adjusted to 7 ± 0.2 by a minimum addition of NaOH 0.1 M. Under these circumstances, Cr(VI) occurred as chromate ions. The pH before and after sorption experiments was checked by using an Inolab pH meter. The use of a pH buffer was avoided to restrict the addition of foreign anions. For the same reason, the flasks were hermetically sealed during experiments. The chromium removal was conducted batchwise in an orbital shaker model GFL 3017, at 20±2 °C, in order to reach the sorption equilibrium for 10 hours.

At equilibrium, the solid was separated by filtration. Cr(VI) concentration in aqueous solution was spectrophotometrically determined at 540 nm by means of diphenylcarbazide colorimetric method (Eaton et al., 2005). Replicate measurements on Cr(VI) samples showed that relative precisions of less than 2% could be routinely obtained.

Chromium uptake by the sorbent was calculated by using the Eq. (3):

qe = (C0 – Ce) V/m (3)

where qe is the sorption loading of sorbent material at equilibrium (mg/g), V the volume of solution (L), C0 (mg/L) and Ce (mg/L) the initial and equilibrium concentrations of Cr(VI), respectively, and m is the mass of adsorbent (g).

The experimental data were processed by using four mathematical models: Langmuir (L), Freundlich (F), Langmuir-Freundlich (L-F) and Redlich-Petereson (R-P) to assess which of the proposed models described the sorption equilibrium to the best. 3. Results and discussions

The four mathematical expressions used for the fits are given in Table 1.

Table 1. The mathematical expressions of the isotherms

used for the modelling of the sorption experiments

Model Equation Langmuir (L)

eL

eLe CK

CKqq⋅+

⋅=

1max

Freundlich (F) neFe CKq /1⋅=

Langmuir-Freundlich (L-F)

neLF

neLF

e CKCKqq

)(1)(

max⋅+

⋅=

Redlich- Peterson (R-P) n

eRP

eRPe CK

CKqq)(1max

⋅+⋅

=

qe is the sorption loading of sorbent material at equilibrium (mg/g); Ce the equilibrium concentration of Cr(VI) (mg/L); qmax maximum sorbed quantity (mg/g); n is the non-homogeneity factor; K – constant)

The four mathematical models were chosen because other published papers reported the preponderant use of Langmuir and Freundlich equations, which can be changed into linear forms easily, to process the results from anion sorption equilibria on these kinds of materials (Das et al., 2003; Das et al., 2004; Ferreira et al., 2006; Lazaridis and Asouhidou, 2003; Lv et al., 2006). Some papers compared the two models to the Langmuir-Freundlich model (Lazaridis, 2003), and others mentioned the use of Redlich-Peterson model to assess anion sorption equilibria on these kinds of materials (Lazaridis et al., 2002). Moreover, despite the linearization resulted from the Langmuir model (Fig.1), R2 coefficients showing very good correlation (0.9996, 0.9972, 0.9992, 0.9968 and 0.9896 for Mg3Al, Mg2ZnAl, Mg1.5Zn1.5Al, MgZn2Al and Zn3Al respectively), when the experimental results were fitted in the Langmuir equation, the R2 coefficients were very low. Two types of calculation were performed by using the four equilibrium equations: (i) estimation of qmax, K and n; and (ii) estimation of K and n, for qmax values equal to the experimental maximum uptake value.

Modelling of sorption equilibrium of Cr(VI) on isomporphic substituted Mg/Zn-Al-type hydrotalcites

513

0 5 10 150.0

0.1

0.2

0.3

0.4

0.5C

e / q

e [g/

L]

Ce [mg/L]

Fig. 1. Linear fit of experimental data by using Langmuir

model for Mg3Al sample

The values of the parameters and the estimate of the goodness of the fit for each model are given in Table 2. Figures 2–5 compare the plots resulted by fitting experimental data for Mg3Al sample by using the four equilibrium equations.

0 5 10 150

10

20

30

40

exp K, qmax est K est

q e [m

g/g]

Ce [mg/L]

Fig. 2. Modelling of Cr(VI) sorption behaviour on Mg3Al

sample by using Langmuir equation

0 5 10 150

10

20

30

40

q e [m

g/g]

Ce [mg/L]

exp K, n est


sample by using Freundlich equation

The comparison showed lower R2 coefficients

for the second calculation type. This finding demonstrated that the increase of the number of assessed parameters decreased the computation error.

0 5 10 150

10

20

30

40

exp K, n, qmax est K, n est

q e [m

g/g]

Ce [mg/L]


sample by using Langmuir-Freundlich equation

0 5 10 150

10

20

30

40

exp K, n, qmax est K, n est

q e [m

g/g]

Ce [mg/L]


sample by using Redlich-Peterson equation

Langmuir, Freundlich and Redlich-Peterson models showed that the calculated sorption capacities qmax were higher than those resulted from experiments. This was most probably due to the fact that the initial chromium concentrations used in the experimental studies were not enough to achieve total sorbent saturation. For the Redlich-Peterson model, the calculated non-homogeneity index n was close to 1, which reduced the Redlich-Peterson equation to the Langmuir one.

For all situations, Langmuir-Freundlich equation showed the best R2 coefficients. The comparison of the experimental and calculated values and the observation of data indicated that the Langmuir-Freundlich model provided the best accurate description of the equilibrium data over the studied samples and concentration range.

Cocheci et al. /Environmental Engineering and Management Journal 6 (2007), 6, 511-515

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Table 2. Isotherm parameters obtained by fitting of the experimental data for the sorption of Cr(VI) on isomorphic substituted

Mg/Zn-Al – hydrotalcites

Estimation of qmax, K and n Estimation of K and n Model qmax K n R2 K n R2

Mg3Al qmax = 35.43 mg/g Langmuir 33.65 18.54 - 0.5408 14.10 - 0.5332 Freundlich - 29.69 14.80 0.7434 - - -

Langmuir-Freundlich 35.76 28.17 0.55 0.8622 27.55 0.58 0.8617 Redlich-Peterson 29.45 29.79 0.97 0.5424 15.56 1 0.5392

Mg2ZnAl qmax = 17.49 mg/g Langmuir 16.29 17.29 - 0.9086 13.46 - 0.8765 Freundlich - 12.98 11.79 0.9585 - - -

Langmuir-Freundlich 31.56 0.10 0.15 0.9603 22.05 0.45 0.9265 Redlich-Peterson 9.85 106.84 0.93 0.9288 14.72 0.99 0.9001

Mg1.5Zn1.5Al qmax = 16.17 mg/g Langmuir 15.67 5.01 - 0.8931 4.27 - 0.8878 Freundlich - 11.94 10.56 0.9497 - - -

Langmuir-Freundlich 17.53 5.96 0.46 0.9899 6.13 0.68 0.9754 Redlich-Peterson 11.70 12.98 0.94 0.9007 4.52 1.01 0.8912

MgZn2Al qmax = 15.25 mg/g Langmuir 14.22 13.51 - 0.8551 9.89 - 0.8223 Freundlich - 11.46 12.71 0.9140 - - -

Langmuir-Freundlich 16.97 0.06 0.09 0.9427 22.46 0.44 0.8610 Redlich-Peterson 5.18 245 0.92 0.8766 11.02 1.01 0.8475

0 10 20 30 40 500

10

20

30

40

q e [m

g/g]

Ce [mg/L]

Mg3Al Mg2ZnAl Mg1.5Zn1.5Al MgZn2Al Zn3Al

Fig. 6. Sorption isotherms for samples fitted in Langmuir- Freundlich model

By analyzing data from Table 2 and Fig. 6,

one can note that for Mg/Zn samples the maximum sorption capacities were close. Zn3Al sample showed a low sorption capacity under the working conditions while Mg3Al sample had a maximum sorption capacity of 35.76 mg/g, representing 71.5 % of the initial Cr(VI) amount, which was in accordance with previous reports (Das et al., 2004; Forano, 2004).

4. Conclusions

This paper aimed at characterizing sorption equilibrium of Cr(VI) on five isomorphic substituted

Mg/Zn-Al – type hydrotalcites. Four mathematical models and two kinds of assessment were used to describe the sorption equilibrium .

The three-parametered Langmuir-Freundlich model approximated the experimental data over the concentration range to the best.

The sorption of Cr(VI) on the investigated hydrotalcites showed continuous decrease of the sorption capacity in the following order: Mg3Al > Mg2ZnAl > Mg1.5Zn1.5Al > MgZn2Al > Zn3Al.

Acknowledgement

The results are obtained as part of the Project CEEX

No. 1/S1 – 2005 activities, under the auspices of MATNANTECH Scientific Authority. The authors wish to thank the MATNANTECH for supporting this research.

References Das D.P., Das J., Parida K., (2003), Physicochemical

characterization and adsorption behavior of calcined Zn/Al hydrotalcite-like compound (HTlc) towards removal of fluoride from aqueous solution, J. Colloid Interf. Sci., 261, 213-220.

Das N.N., Konar J., Mohanta M.K., Srivastava S.C., (2004), Adsorption of Cr(VI) and Se(IV) from their aqueous solutions onto Zr4+-substituted ZnAl/MgAl-layered double hydroxides: effect of Zr4+ substitution in the layer, J. Colloid Interf. Sci., 270, 1-8.

Eaton A.D., Clesceri L.S., Rice E.W., Greenberg A.E. (Eds.), (2005), Standard Methods for the Examination of Water and Wastewater, 21th Edition, American Public Health Association, Washington, DC.

Ferreira O.P., de Morales S.G., Duran N., Cornejo L., Alves O.L., (2006), Evaluation of boron removal from water by hydrotalcite-like compounds, Chemosphere, 62, 80-88;

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Forano C., (2004), Environmental Remediation Involving Layered Double Hidroxides, In: Clay Surfaces. Fundamentals and Applications, Wypych F., Satynarayana K. G. (Eds.), Elsevier, New York.

Gheju M., Iovi A., (2006), Kinetics of hexavalent chromium reduction by scrap iron, J. Haz. Mat., B135, 66-73.

Kooli F., Depege C., Ennaqadi A., de Roy A, Besse J.P., (1997), Rehydration of Zn–Al layered double hydroxides, Clays Clay Miner., 45, 92-98;

Lazaridis N.K., Hourzemanoglou A., Matis K.A., (2002), Flotation of metal-loaded clay anion exchangers. Part II: the case of arsenates, Chemosphere, 47, 319-324.

Lazaridis N.K., Asouhidou D.D., (2003), Kinetics of sorptive removal of chromium (VI) from aqueous solutions by calcined Mg-Al-CO3 hydrotalcite, Water Res., 37, 2875-2882.

Lazaridis N.K., (2003), Sorption removal of anions and cations in single batch systems by uncalcined and calcined Mg-Al-CO3 hydrotalcite, Water, Air, Soil Poll., 146, 127-139.

LeVan M.D., Carta G., Yon C.M., (1999), Adsorption and ion exchange, In: Green D.W. Perry’s chemical engineer’s handbook, 7th Edition, McGraw-Hill, New York.

Lv L., He J., Wei M., Evans D.G., Duan X., (2006), Uptake of chloride ion from aqueous solution by calcined layered double hydroxides: Equilibrium and kinetic studies, Water Res., 40, 735-743.

Lv L., He J., Wei M., Evans D.G., Duan X., (2006), Factors influencing the removal of fluoride from aqueous solution by calcined Mg-Al-CO3 layered double hydroxides, J. Haz. Mat., B133, 119-128.

Miyata S., (1975), The synthesis of hydrotalcite-like compounds and their structures and physico-chemical properties – I: The systems Mg2+-Al3+-NO3

-, Mg2+- Al3+-Cl-, Mg2+-Al3+-ClO4

-, Ni2+-Al3+-Cl- and Zn2+-Al3+-Cl-, Clays Clay Miner., 23, 369-375.

Praus P., Turicova M., (2007), A phisico – chemical study of the cationic surfactants adsorption on montmorillonite, J. Braz. Chem. Soc., 18, 378-383.

Toxicological Profile for Chromium, (1998), Agency for Toxic Substances and Disease Registry (ATSDR), U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA.

Vaccari A., (1998), Preparation and catalytic properties of cationic and anionic clays, Catal. Today, 41, 53-71.



______________________________________________________________________________________________

VIRTUAL ENVIRONMENTAL MEASUREMENT CENTER BASED ON

REMOTE INSTRUMENTATION

Marius Branzila1∗, Carmen Alexandru 2, Codrin Donciu1, Alexandru Trandabăţ1, Cristina Schreiner1

1Technical University of Iasi, Faculty of Electrical Engineering, 51-53 Mangeron Blvd., 700050, Iasi, Romania

2Technical University of Iasi, Faculty of Chemical Engineering, 71 Mangeron Blvd., 700050, Iasi, Romania

Abstract In this paper we propose system architecture for virtual environmental measurement center based on remote instrumentation. We use Internet facilities for transmission of the information. The station center can be used in remote control mode. Circumstance data can be collected with logging field station (Web-E-Nose or meteorological station). The environmental measurement center collects and automatically save data about the temperature in the air, relative humidity, pressure, wind speed and wind direction, rain gauge, solar radiation and air quality but also can perform smell detection using a purposed Web-E-Nose. Also can analyze historical data and evaluate statistical information and publish data in the Internet using LabVIEW Web Server capability. Key words: environmental monitoring, remote and virtual instrumentation, LabVIEW Web Server, Web-E-Nose


1. Introduction

The EU-funded conference on "Environment, Health, Safety: a challenge for measurements", held in Paris in June 2001, recognized the need to improve the performance of environmental measurement systems and their harmonization at EU level, to foster the dialogue between the providers of measurement methods and the users of measurement results, and to prepare the base - by establishing special communication tools – for the integration of research expertise and resources of environmental monitoring across Europe. The concept presented herein aims to respond to this actual challenge by combining the latest software trends with the newest hardware concepts in environmental monitoring, towards providing reliable measurement results and representative environmental indicators, evaluating trends and quantifying the achieved results in order to manage the potential environmental risk in compliance with European legislation and local particularities.

On the other hand, the climate change and the unpredictable environmental phenomena occurring in

the last years impose new and modern meteorological stations, updated to new evaluation conditions, and offering remote access to measurement infrastructure (Branzila et al., 2006).

The system presented below gives such an opportunity of performing measurements under real conditions from a remote location, of an optimum access to sophisticated and/or expensive apparatus and instrumentation - even geographically distributed, and/or of repeating the same experience for a certain number of times, at either convenient or unpredictable hours, with minimum support from the technical staff (Trandabat et al., 2005).

For this purpose, a new concept of performing high-speed data acquisition based on remote sensors, and an accurate transmission and processing of the meteorological parameters towards obtaining useful data for the users was developed in connection with the centre services. New methods of interconnecting hardware and dedicated software support were successfully implemented in order to increase the quality and precision of measurements.

In the same time, the Web concept itself is changing the way the measurements are made


Brinzila et al. /Environmental Engineering and Management Journal 6 (2007), 6, 517-520

518

available and the results are distributed/ communicated. Many different options are occurring as regards reports publishing, data sharing, and remotely controlling the applications (Girao, 2003).

2. The presentation of the system architecture

An adaptive architecture based on web server

application is proposed, in order to increase the performance of the server that hosts a dedicated (environmental monitoring) Web site, and customize the respective site in a manner that emphasizes the interests of the clients. The most virtual laboratories normally provide access either to one remote application, or accept only one user at a time. The system presented below provides a multitask connection, by accessing different detectors, working with different clients, and offering different variants for dedicated remote jobs, including technical tests of terminals, direct measurements of environment parameters, remote expertises, technical demonstrations or vocational training and education (Fig. 1).

Fig. 1. System architecture for remote and distributed environmental measurement center

The instrumentation control and

communication software has been designed under LabView graphical programming language. In particular, the PC-server – via TCP/IP protocol and the client-server - via CGI (Common Gateway Interface) technology, have the important role of developing the PC-instruments communication. CGI simply defines an interface protocol by which the server communicates with the applications. A dedicated software package supports the CGI applications in form of virtual instruments, used to develop interactive applications for Web-enabled experimental set-ups (that may be geographically distributed stations or expensive instruments, distributed areas of specialized sensors for water, air,

soil etc. and web-E-nose pollution monitor). The following procedures are implemented on laboratory server: dynamically allocation, web interfaces and Slab-SL interface. The communications between Centre server and each measurement workstation are performed by bi-directional interfaces SL-Slab and Slab-SL. On the front panel of application, the setup parameters are prescribed, and the data are transferred to the e-multitask interface. From the main web page of the centre server, the operator has the possibility to directly and selectively supervise the measurements protocols and select the parameters display, the publishing procedure, warning degree etc. On the other hand, due to the multitask facility, the number of users (clients) connected in the same time - to exploit the results - may become unlimited.

We propose an Internet Based Environmental Monitoring Center with an increasing data exchange speed of information between the small meteorological distributed centers and the other hand all the world can see the evolution of meteorological parameters using World Wide Web. In this case we can warn the people in utile time about bad weather. Electronic mail messages are automatically generated to notify researchers about any identified anomalies. The data are then stored in secure electronic databases and made available for retrieval and analysis via standard web browsers. Authorized users may select any portion of the data and conduct a variety of predefined, automated analysis procedures or import the data into local spreadsheets, databases, or other local analysis software.

Fig. 2. The main page of the virtual environmental measurement center and Virtual Laboratory for on-line

measurements

The authors propose in the same time an educational measurement remote system. Today, many academic institutions offer a variety of web-based experimentation environments so called remote laboratories that support remotely operated physical experiments. Such remote experiments entail remote operation of “distant” physical equipment offering students more time for laboratory work. This is one

Virtual environmental measurement center based on remote instrumentation

519

way to compensate for the reduction of lab sessions with face-to-face supervision without significant increase of cost per student. Remote experiments are adapted to the flexible environment of the students of today and permit low cost methods for lab work evaluation. Web-based experimentation is an excellent supplement to traditional lab sessions. The students can access lab stations outside the laboratory and perform experiments around the clock. It is possible to design virtual instructors in software which will protect the equipment from careless use; also theft of equipment will not be a problem. Interfaces enabling students to recognize on their own computer screen the instruments and other equipment in the local laboratory may easily be created. Apart from the fact that each student or team of students works remotely in a virtual environment with no face-to-face contact with an instructor or other students in the laboratory, the main difference between a lab session in the remote laboratory described here and a session in a local laboratory is that it is not possible for students to manipulate physical equipment e.g. wires and electronic components with their fingers in a remote laboratory.

In this way, the architecture of the system has two mains components: • client user that uses a client computer and • measurement provider who disposes the server

with the web site of the virtual laboratory. Two cases are possible for remote teaching

and education. In the first case, the professor from server room, after he set the students connected in this way, the students from their home study points can receive and follow the lessons. The number of students connected in the same time is unlimited. All communication software is designed under LabVIEW graphical programming language. The main web page is located in server that allows the access to every station, using a connection link. In this machine a web server is running. The LabVIEW server represents the back up for the individual stations.

In the second case the server is set to all user masters. The students are able to perform the connection via modem and provider until server, in order to training and practice the programs. An adaptive Web server application tries to increase the performance of the Web server that hosts a Web site, as seen from the point of view of clients. The adaptiveness is based on the customization of the Web site in a manner that emphasizes the interests of the clients. Our server with dynamic allocation of client number is auto restarting.

The monitories parameters are the fallowing: air temperature (T1-T4), humidity (HR1-HR2), pressure (P), wind speed (WS) and wind direction (WD), rain gauge (RG), solar radiation (SR), and air quality (AQ) using the Web-E-Nose. The sensor types and accuracies are listed in Table 1.

The meteo-system architecture is composed as follows: • the specialized sensors, • signal conditioning circuit,

• power supply - rechargeable batteries • a data acquisition board with data transfer by

RS232 port, • PC meteo-host, and the server provided with

an Ethernet controller, • PC video-host

The main components of the Web E-Nose with data distribution by Internet: • sensor array that “sniffs” the vapors from a sample and provides a set of measurements. • prototype data acquisition board SADI • a microcontroller • Tibbo Ethernet server,

The microcontroller is the WebE-Nose “brain” having the roll to communicate with the SADI and Tibbo Ethernet server, acquiring information from the gas sensors and SHT11 temperature and humidity sensor, processing data for pattern recognition and transmit the decision by RS232 protocol to the Ethernet server.

Table 1. Gradients of environmental sustainability

Parameter Sensor Accuracy

Temperature precision integrated-circuit centigrade temperature.

0.5°C accuracy guaranteeable (at +25°C)

Humidity

the RH sensor is a laser trimmed thermoset polymer capacitive sensing element with on-chip integrated signal conditioning.

±2% RH, 0-100% RH non-condensing, 25 °C, Vsupply = 5 Vdc

Wind speed

the sensor consists of a lightweight 3-cup anemometer, which is mechanically coupled to an AC generator.

± 2.0 mph (0.90 m/s) over entire range m/s). operating range: 0-100 mph

Wind direction

the sensor consists of a vane and counterweight assembly, which is mechanically coupled to a potentiometer

± 3.0°

Rain gauge tipping bucket 0.01 inch resolution

±1% at 1” per hour

Pressure

the sensor is made up of a bellows, which is directly coupled to the core of a linear variable differential transformer (LVDT)

±0,02” Hg over any ±2,00” Hg span

Solar radiation (total sun and sky)

photovoltaic sensor

±10% of the standard(48 junction thermopile black and white pyranometer)

3. Applications and perspectives

Pilot research cooperation for a regional high

speed environmental measurement centre, based on remote instrumentation, was established in 2007 with the kind support from the Local Council, Town Hall and the local Environmental Agency in Iasi.

The research is still under development, and the target lies in mapping all the residential and industrial areas of the county, improving the remote instruments and developing the fast communication with all distributed meteorological stations in the related area and centralizing the data at the central station level.

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The data will be further processed according to a statistical model, allowing the evaluation of peak, average and trend parameters and permitting a pertinent prediction of pollution - related either to temporal (season, day/night, peak hours etc.) or geographical parameters (altitude, vicinity etc.), or to atmospheric conditions (humidity, wind etc.), or even to societal demands, or to other relevant contextual circumstances.

The communication system is in work at this time, and will process on-line the data towards an active database, even corroborated with other information obtained previously or independently from the (autonomous) meteorological stations or balloons, or from the individually displayed ground sensors. By this way, the system primarily receives real-time information from the monitored sites, evaluates/predicts the potential risk for environment safety and can generate automatic reports to the central control centre, from where a potential pertinent intervention can be eventually done.

But, nevertheless, the proposed concept may be very useful not only for the decisional factors, local authorities, accreditation bodies etc., but also for the educational process and public aware. The proposed concept was tested already as an educational tool for the students dealing with “Environment Quality and Maintenance Management” discipline.

For higher education purposes, the proposed system accomplishes some peculiar tasks of a Virtual Laboratory for environment monitoring field, according to some of the applications described by Branzila M. et al. (2005 and 2006) or Schreiner C. et al. (2006). 4. Conclusions

The paper presents the architecture of a

versatile, flexible, cost efficient, high-speed environmental measurement centre, based on remote instrumentation, and having as final purposes the

monitoring of the air quality (physical and chemical parameters) and the advertising of the air pollution.

In many locations a basic infrastructure to evaluate the environment parameters already exists, but a unitary concept of an E-environment centre can be used to deliver services of comparable or higher quality, at a clear lower cost and a higher speed and reliability.

On the other hand, a prototype of Web-E-Nose system was tested, and provided to be well suited for repetitive and accurate measurements, without being affected by saturation. But the successful implementation of such Web-E-Nose concepts for air pollution evaluation at larger scales will require a careful examination of all costs, either direct or indirect, and should demonstrate its societal benefit over time.

The remote and distributed measurement system developed as environmental centre may be also particularized as virtual laboratory for on-line environmental monitoring, helping the formation of well trained specialists in the domain. References Branzila M., Alexandru C.I., Donciu C., Cretu M., (2006),

Design and Analysis of a proposed Web Electronic Nose (WebE-Nose), IPI , LII, 971-976.

Branzila M., Fosalau C., Donciu C., Cretu M., (2005), Virtual Library Included in LabVIEW Environment for a New DAS with Data Transfer by LPT, Proc. IMEKO TC4 , vol.1, Gdynia/Jurata Poland, 535-540.

Girao P., Postolache O., Pereira M., Ramos H., (2003), Distributed measurement systems and intelligent processing for water quality assessment, Sensors & Transducers Magazine, 38, 82-93.

Schreiner C., Branzila M., Trandabat A., Ciobanu R., (2006), Air quality and pollution mapping system, using remote measurements and GPS technology, Global NEST Journal, 8, 315-323, 2006.

Trandabat A., Branzila M., Schreiner C., (2005), Distributed measurements system dedicated to environmental safely, Proc. 4th Int. Conf. on the Manag. of Tech. Changes, vol.2, Chania, Greece, 121-124.



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MICROWAVE-ASSISTED CHEMISTRY. A REVIEW OF

ENVIRONMENTAL APPLICATIONS

Mioara Surpăţeanu1, Carmen Zaharia1∗, Georgiana G. Surpăţeanu2

1“Gh. Asachi”Technical University of Iasi, Faculty of Chemical Engineering, Department of Environmental Engineering and

Management, Bd.D.Mangeron 71A, 700050, Iasi, Romania 2 Laboratory of Medicinal Chemistry, University of Antwerp

Abstract The extraction of some pollutants from different matrices, the treatment of hazardous and infectious wastes, the destruction of refractory compounds and the prevention of noxious emissions are the main environmental applications of microwave-assisted chemistry. The advantages and disadvantages of this technique are also considered. Key words: microwave-assisted chemistry, environmental application


1. Introduction

In the latest time, microwaves have been exceeded the stage of domestic utilization or uses in telecommunications. Thus, many other applications are reported such as: synthesis of new compounds (Ferone et al., 2006; Logar et al., 2006), particularly drugs (Larhed and Haldberg, 2001), chemical analysis based on hydrolysis (Stenberg et al., 2001), digestion reactions or extraction procedures (Chang et al., 2004), hydrometallurgy (Al-Harahsheh and Kingman, 2004) and environmental protection, especially for accelerating the destruction of some pollutants (Horicoshi and Tokunaga, 2006).

These applications are based on the fact that the microwave irradiation procedures assure an efficient internal heat-transfer and make possible superheating even at atmospheric pressure (Larhed and Haldberg, 2001).

Consequently, a considerable reduction of reaction time is obtained and thus microwave chemistry proves their efficiency. Other benefits of microwave homogenous heating are: milder reaction conditions, higher chemical yields or a better recovery of volatile elements and compounds, lower contamination level, minimal volumes of reagents are required, lower energy consumption, more

reproducible procedures and a better working environment (Agazzi and Pirola, 2000).

2. Microwave chemistry basics

Microwave is a form of electromagnetic

energy with wavelength between 1 mm and 1 m that corresponds to frequencies between 300 MHz and 300 GHz. The most commonly frequency of 2450 MHz is used for microwave chemistry (Larhed and Haldberg, 2001; Al-Harhsheh and Kingman, 2004). This frequency just affects the rotation energy of molecules and the interference with telecommunications frequencies are avoided.

The heating effect of microwaves is mainly based on two mechanisms: dipolar polarisation and conduction.

Dipolar polarisation is due to the fact that the dipole is sensitive to external electric fields and will attempt to align with them by rotation but this motion is prevented by intermolecular inertia. Depending on irradiation frequency, the dipole may react by aligning itself in/out phase with the electric field. The microwave frequency is low enough that the dipoles have time to respond to the alternating field, and therefore to rotate, but high enough that the rotation does not precisely follow the field. As the dipole


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reorientates to align itself with the field, the field is already changing and a phase difference exists between the orientation of the field and that of dipole. This phase differences cause energy to be lost from the dipole in random collisions, and to give rise to dielectric heating (Whittaker, 1997).

Conduction mechanisms are related to movement of charge carriers (electrons, ions etc.) under the influence of the electric field. As a result of ion movements and collisions the conversion of kinetic energy to thermal energy occurs.

In conclusion, the mechanism of microwave heating in the case of an electric conductor includes both dipolar polarisation of polar substances and conduction mechanism of ions in liquid phase or locked up in solids interstices.

3. Microwave equipment and sample preparation

First experiments concerning the application

of microwave heating effect to chemical reactions were performed with multi-mode domestic oven. In these ovens microwaves are heterogeneously distributed, and less-defined regions of high and low energy intensity are produced. Actually, a large variety of microwave equipment is found on the market, which assures well-defined regions of maximum and minimum field strength (Larhed and Haldberg, 2001). These equipments must be provided with reliable temperature control system to assure an efficient application of microwave irradiation as energy source. Also, an adequate vessel must be used. Open vessel systems may be used but the closed vessel has some advantages. This is because microwaves only heat the liquid phase, while vapours do not absorb microwave energy. The temperature of the vapour phase is therefore lower than the temperature of liquid phase and vapour condensation on cool vessel walls takes place (Agazzi and Pirola, 2000). As a result, the actual vapour pressure is lower than the predicted vapour pressure and this thermal non-equilibrium is a key advantage of microwave technology, as very high temperatures can be reached at relatively low pressures.

The most limiting factor of microwave closed vessel are related to sample amount. This is because the larger sample amount, the higher is the pressure generated by the reaction.

Thus, the microwave degradation of phenol-containing polymeric compounds was accomplished by placing closed vessel inside a commercial oven (Chang et al., 2004). The microwave system was equipped with a Teflon-coated cavity and a removable 12-position sample carousel, a sensor for pressure measurements and an optical fibber to monitor and control the digestion temperature.

Sometimes the heating microwave power is associated with UV irradiation to assure the degradation of refractory pollutants e.g. chlorophenols and so the equipment is completed with a low- or medium-pressure mercury lamp as UV

light source (Cirva et al., 2005; Horicoshi et al., 2006).

4. Environmental applications of microwave chemistry

The most important and directly applications

of microwaves assisted chemistry into environmental field are related to extraction of some pollutants (especially persistent organic pollutants, POP) from liquid or solid media in the view of their analysis (Basheer et al., 2005; Fountoulakis et al., 2005), in the treatment of hazardous and infectious wastes (Gan, 2000; Diaz et al., 2005) and, also, in a range of environment-related heterogeneous catalytic reaction systems like as: the decomposition of hydrogen sulphide, reduction of sulphur dioxide with methane, reforming of methane with carbon dioxide etc. (Zhang and Hayard, 2006).

Generally, chemical reactions based on microwave heating are characterised by a good reproducibility, are cleaner that those by traditional way (water or oil bath) and many times lead to high efficiency. Supplementary advantage of microwave assisted chemistry is their applicability both to homogenous reactions in aqueous or non-aqueous solutions and dry media reactions. This ultimate aspect was considered for the application of heating microwave effect to improve the yield of metal extracted from minerals simultaneous with the increasing demand for more environmental friendly processes.

Many papers deals with the extraction of metals such as copper, gold, nickel etc. from their ores by microwave-assisted leaching, process more attractive comparatively with pyrometallurgy due to economical, technical and environmental reasons (Al-Harahsheh and Kingman, 2004). Thus, it was reported that by heating chalcopirite with concentrated sulphuric acid in an adapted domestic microwave oven (20 minutes, 200-260°C, 2,45 GHz), the leaching reaction product in water; the copper extraction was between 90-99% (Hsieh et al., 2007). In the same time the elemental sulphur was captured and only low volumes of sulphur dioxide was produced. The improvement of copper extraction was explained by the thermal convention currents generated as the result of different rate heating of liquid and heterogeneous reaction system. Similarly results were obtained for gold leaching from its refractory ores, especially pyrite and arsenopyrite. The enhancement of gold leachability after microwave pre-oxidation was explained by the formation of a porous (hematite) structure, which favorize gold extraction in a cyanide solution (Huang and Rowson, 2000).

The same microwave heating effect was applied for coal desulphuration as pre-treatment to minimise SO2 emissions during burning (Johnes et al., 2002).

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Other applications of microwave heating effect were focussed on environment-related heterogeneous catalytic reactions such as the decomposition of hydrogen sulphide into hydrogen and sulphur and reduction of sulphur dioxide with methane (Zhang and Hayard, 2006). Thus, to reduce the hydrogen sulphide emissions level into the atmosphere, it has been investigated the catalytic decomposition by microwave heating. The reactions were performed under continuous flow conditions in tubular quartz reactors using as catalyst either an impregnated molybdenum sulphide on γ-alumina or a mechanically mixed sample of molybdenum sulphide on γ-alumina. The temperature in the microwave cavity was monitored using an optical fibre thermometer. It was found that the H2S conversion degree under microwave conditions was much higher than those obtained with conventional heating at the same temperature, especially with mechanically mixed catalyst. The enhancement of the reaction rate and product selectivity under microwave conditions must be attributed to thermal effects which may result because of differences between the real reaction temperature at the reaction sites and the observed average temperature.

Microwave-assisted extraction technique is a new procedure used especially to recovery of POPs from soils, sediments and sewage sludge (Basheer et al., 2005; Horikoshi et al., 2006; Hsieh et al., 2007). Many papers underlines the advantages of this technique over the other new (sonication, pressurised liquid extraction and supercritical fluid extraction) or classical methods (Soxhlet extraction) but also their limitations.

Microwave-assisted extraction (MAE) is based on the nonionising radiation that causes molecular motion by migration of ions and rotation of dipoles, without changing the molecular structure (Fountoulakis et al., 2005). Due to the principles of microwave heating the choice of the solvent depends on its ability to absorb microwaves, defined by its dielectric constant ε (Budzinski et al., 1999). Non-polar solvents do not absorb microwave energy and therefore such solvents have poor extraction efficiencies compared to polar solvents or mixture of solvents at least one of which must be polar.

It was showed that the addition of water facilitates non-polar organic solvents to absorb microwave energy and so improves the release of target analytes from sample matrix (Basheer et al., 2005). This is because at high pressure and temperature its dielectric constant, viscosity, and surface tension become low these facts facilitating the extraction from solid samples of the organic compounds having different polarities. Nevertheless, because of low selectivity the main drawback of MAE is the need of a cleanup procedure (Yafa and Farmer, 2006; Pastor et al., 1997).

Thus, to overcome this disadvantage, a microwave-assisted extraction and partition method (MAEP) using water-acetonitrile and n-hexane was studied to determine some pesticides (trifluralin,

metolachlor, chlorpyriphos and triadimefon) from agricultural soils (Fuentes et al., 2006).

Studies were carried out using sieved soils (2 mm mesh) with diverse physico-chemical properties collected (0-20 cm depth) in different agricultural zones in Chile. Aliquots of spiked soil were weighed and transferred to a microwave extraction vessel and the extraction solution (water-acetonitrile) was added in 1:1 sample-to-solvent ratio. After homogenisation by manual shaking, hexane was added for partitioning. The extraction vessel was covered with pressure-resistant holders and preheated for 2 min at 250 W and then 10 min at 900 W, and 130°C maximum temperature using a microwave oven system (which allows the simultaneous heating of six vessels). An optic-fibber probe inside the monitoring cell was used to control temperature. After microwave irradiation, vessel was water-cooled, opened and hexane layer was evaporated at dryness; the residue was re-dissolved and directly analysed by gas chromatography electron capture detection. It was found that the method is efficient and fast to determine hydrophobic pesticides at ng g-1 level in soil with different clay-to organic matter ratios.

Among all the studied parameters (time and power of irradiation, nature of solvent, percentage of water) the quantity of water is of primary importance to maximise the recoveries of polycyclic aromatic hydrocarbons (PAH) from soils and sediments by microwave-assisted extraction technique (Budzinski et al., 1999). The studied PAHs range from three-ring aromatic compounds (phenanthrene, anthracene) to six-ring aromatic compounds (benzo[ghi]perylene), and the optimal conditions established by working with 0.1 to 1.0 g of freeze-dried sediments and soils were as follows: 30% water, 30 ml of dichloromethane, 30 W, 10 min irradiation time. The extracted aromatic compounds were analysed by gas chromatography coupled to mass spectrometry (GC-MS). In these conditions the recoveries for all the tested samples are very good (more than 85%). In comparison with Soxhlet extractions (SE) this technique are proved important advantages like as decreasing of solvents volumes (2x250 ml for SE up to 30 ml for MWAE) and reduction of operational time (at least 48 hours for SE and 10 minutes for MWAE).

MWAE was tested at laboratory-scale for the extraction of petroleum hydrocarbons from contaminated soil in Canada (Punt et al., 1999). It was found that microwaves could be used to enhance the solvent extraction of the contaminants from the soil and that the proprieties of soil greatly affected the extent to which the contaminants are removed.

MWAE also was applied to analyse organochlorine pesticides and polychlorinated biphenyls (Horicoshi et al., 2006). Thus it was developed a MWAE procedure coupled with a liquid-phase microextraction (LPME) using a porous polypropylene hollow fibber membrane (HFM) for cleanup, enrichment and extraction of these POPs from marine sediments. The sediment samples of 1 g,


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air dried to constant mass at room temperature and sieved (size 2 mm) were subjected to microwave heating with 8 ml of ultrapure water at 600 W. After that the extract containing POPs was transferred to a 10 ml volumetric flask. Sediments were further rinsed with 2 ml ultrapure water and the rinsate was transferred to the same 10 ml volumetric flask. For the enrichment and extraction procedure a particular syringe with a cone-tipped needle was used and toluene was selected as solvent. Toluene (5 µl) was drawn into the syringe and the needle was tightly fitted to a 1.3-cm length of HFM that was previously heat-sealed at the other end. The HFM was impregnated with toluene for 10 s to dilate the membrane pores then the syringe needle-HFM was immersed 5 mm below the surface of the sample solution under agitation on the magnetic stirrer. Extraction between the toluene within the HFM and the sample solution was allowed to proceed, allowing the analytes to diffuse though porous membrane and dissolve into the toluene. After the mass transfer of analytes from the aqueous sample solution to organic phase the toluene in the HFM was withdrawn into the syringe, which was then removed from sample solution. The extracted compounds (organochlorine pesticides such as Lindane, Heptachlor, Aldrin, Dieldrin etc. and polychlorinated biphenyls such as 2-dichlorobiphenyl, 2,3-dichlorobiphenyl, 2,4,5-trichlorobiphenyl etc.) were analysed by GC-MS. The proposed method for quantifying POPs exhibits some advantages compared to SE or conventional heating because is relatively simple, requires a low volume of solvent and eliminates carry-over effects through the use of disposable HFM.

Other categories of compounds analysed by intermediate of MWAE include nonylphenol ethoxylates (NPEO) and nonylphenol (NP), the first representing a significant fraction of non-ionic surfactant market. NPEO and their metabolites exhibit toxic effects on the aquatic organisms due to their ability to mimic natural hormones (estrogens) inducing endocrine disruption. Those compounds are discharged to the environment through the wastewater treatment plant effluents and they have been detected both in soils and aquatic organisms (Johnes and Heathwaite, 1992).

MWAE was used for the determination of NPEO and NO in sewage sludge and method efficiency was evaluated as to linearity, repeatability, accuracy, and sensitivity (Fountoulakis et al., 2005). Thus, it was pursue to develop and optimise MWAE for the specifically extraction of the two compounds followed by their determination using HPL coupled with fluorescence detector. Environmental samples were collected from the sewage treatment plants in Greece, conserved by immediate addition of 1% formaldehyde and, when not immediately analysed, were stored in the dark at 4°C. Prior to the analysis of NP and NPEO, the samples were filtered and dried in the oven at 35°C, and the resulting solids were grinded. MWAE procedure was performed on the dried samples (0.03-0.3 g) in perfluoroalcoxy (PFA)

copolymer resin Teflon-lined extraction vessel after the addition of 20 ml solvent, namely hexane/acetone: 1/1 (v/v) or dichloromethan/methanol: 3/7 (v/v). The extractions were performed at various conditions of temperature (100 and 120°C) and power (600 and 1200 W). The extraction time was 17 min. After cooling, the extracts were concentrated to an approximate volume of 1 ml using a rotary vacuum evaporator; the resulted concentrate was redisolved in 10 ml acetonitrile and the organic phase was analysed by HPLC-FD after filtration. It was observed higher extraction recoveries (61.4% for NPEO and 91.4% for NP) when 1 ml water was added to dry sample prior to extraction.

MWAE technique was successful aplicated for the determination of some quinolone antibacterial agents (flumequine and oxolinic acid) from sediments and soils (Prat et al., 2006). Such as many antibacterial agents, oxolinic acid (OXO) and flumequine (FLU) exhibit great chemical stability and high sorption coefficients and these characteristics contribute to their accumulation in sediments and soils. Half-lives of these compounds are appreciated at 150 days (Johnes et al., 2002). The extraction of the analytes was performed by liquid-liquid partition between a sample homogenate in an aqueous buffer solution and a non-miscible organic solvent and MWAE was used to improve the speed and efficiency of the extraction process. The environmental samples (marine sediments and soils) were oven-dried (110°C), sieved (90 µm) and stored in the dark at –20°C. Before the analysis the samples were thawed and, for recoveries studies, were spiked by adding 0.5 ml of an aqueous standard solution containing OXO and FLU to 0.5 g dray sediment or soil sample. The mixture was equilibrated by shaking for 15 min and then left standing overnight at room temperature in the dark. Microwave-assisted extraction was performed in a PFTE vessel before the addition of 10 ml of 1 M phosphoric acid buffer at pH 2 to samples prepared as above mentioned with 10 ml dichloromethane. After microwave irradiation (22 min, 90°C) the vessel was air-cooled to below 40°C then the content was transferred in a 30-ml glass tube and centrifuge (5 min, 4000 rpm). A clean-up step to remove some of coextracted compounds was introduced consisting in back-extraction in 1 M sodium hydroxide. The determination was carried out by reversed phase liquid chromatography on an octyl silica-based column and fluorimetric detection. Resulted solution was filtered by a 0.45 µm nylon membrane and injects into chromatograph. The absolute recoveries rates were determined from spiked samples by comparing peak areas of calibration standard solutions. The values range from 79% to 94% for the whole process.

In the same manner, microwave assisted extraction was used to determine methylmercury from polluted sediments in comparison with manual and supercritical fluid extraction techniques (Lorenzo et al., 1999). The experiments were carried out on freeze dried sediment samples sieved to a particle size below


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300 µm. Spiked samples were prepared with methanol containing known concentration of methylmercury to appreciate the extent of recoveries. The determination is based on the separation by gas chromatography followed by electron capture detection. It was showed that manual (conventional) and microwave-assisted extraction produce almost identical extract. Nevertheless, the conventional extraction procedure is time- and labour-intensive (2-3 hours) and requires the uses of relatively large amounts of toxic organic solvents. Supercritical fluid extraction in most cases produces similar recoveries with manual extraction and has the advantage that is relatively fast (50 min) but matrix effects may be important. MWAE provide a reliable and advantageous extraction procedure because requires smaller volumes of organic solvents than the manual technique, and total sample-processing time is reduced by the shorter extraction time (usually no more than 10 min) and simultaneous extraction of several samples. Moreover, the microwave-assisted extraction appears to be much less dependent on the sediment matrix.

A novel application of microwave heating effect in environmental protection regards the treatment and disposal of healthcare wastes (Diaz et al., 2005).

Wastes produced in healthcare facilities in developing countries have raised serious concerns because of the inappropriate treatment and final disposal practices accorded to them. Inappropriate treatment and final disposal of wastes can result in negative impacts to public health and to environment.

Some of the more common treatment and disposal methods used in the management of infectious healthcare wastes in developing countries are: autoclaves and retorts; microwave disinfection systems; chemical disinfections; combustion and disposal on land (dump site, controlled landfill, pits, and sanitary landfill).

Microwave systems in the healthcare waste sector commonly require the addition of water. Microwave disinfection systems typically consist of three major types of equipment: (1) material handling equipment, (2) the disinfection equipment itself, and (3) environmental control equipment. The disinfection area or enclosure includes a hermetically enclosed chamber, where the materials to be treated are placed and into which the microwaves are focused. Microwave systems are designed and built in a variety of sizes, ranging from a few kg per hour to more than 400 kg per hour. The units can be operated as a batch process or in a semi-continous mode. Large-scale systems can have from 1 to 6 microwave generators and, generally, each generator has a power output on the order of 1.2 kW. For microwave disinfection process the waste to be treated is placed in carts and transported to the treatment facility (e.g. a mobile microwave unit). The carts are lifted by a hydraulic mechanism and the waste is discharged into a hopper after the gate is opened. As the waste is introduced into the hopper, steam is injected there and

the air is extracted from the unit. All extracted air is passed through a high efficiency particulate air filter. The waste in hopper is forced into a shredder. The shredded waste is transported via a rotating screw, exposed to steam, and then heated between 95-100 °C by means of microwaves. The treated waste may be passed through a secondary shredder to achieve a higher degree of particle size reduction than with only one shredder.

The disinfection in microwave units is not a result of material exposure to the microwaves. The steam produced from the moisture in the waste by the microwave energy brings about the destruction of the pathogenic organisms in the waste.

Other papers indicate that microwaves proved effective in destruction of pathogens in sewage sludge (Hong et al., 2004). Thus, the mechanisms and roles of microwaves on fecal coliform destruction were investigated by different methods like as bacterial viability tests, electron transport system and β-galactosidase activity assay, gel electrophoresis etc. Live/dead cell bacterial viability kits were used to investigate the cell wall damage of fecal coliforms caused by microwaves compared with that by external heating.

Sludge samples from wastewater treatment plant were irradiated in a 200 ml beaker in a microwave oven, which operate at a frequency of 2450 MHz. In general, microwave irradiation for 60 s led to almost complete destruction of coliforms while external heating needed 100°C. This indicates that microwave technology is superior to external heating in terms of pathogen destruction, methane generation and energy requirement. So, the microwave irradiation of sludge appears to be a viable and economical method of destructing pathogens and generating environmentally safe sludge.

By means of microwave technology it is possible the processing of industrial of hazardous industrial waste. Such wastes are currently disposed on landfill sites and this practice is concerned in groundwater’s pollution as result of some toxic compounds leaching.

Differing from conventional treatments microwave irradiation may catalyse chemical reactions by a selective heating explained by a special dipolar oscillating and dielectric losses effect. Thus, reversed temperature gradients can be generated in a microwave field and the activation energy in sterilisation, sintering and chemical reactions can be reduced.

The microwave irradiation was also used to denature the β-glucosidase fraction associated with viable microorganisms from soils as an estimate of extracelular (abiontic) activity (Knight and Dick, 2004). This is because the β-glucosidase activity can detect soil management effects and has potential as a soil quality indicator that could be used in conjunction with other soil analyses for several reasons. First, it catalyzes the final step in the biodegradation of cellulose compounds and the subsequent release of glucose to microorganisms.


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Thus, it plays a vital role in the large-scale C cycle, as well as small-scale processes of releasing a labile energy source for microorganisms. Secondly, the abiontic form contributes to a significant amount of the total activity. Abiontic activity was estimated after subjecting soil samples to microwave that likely denatured most of the enzyme activity from the viable microbial population. The result showed that although β-glucosidase activity after microwave irradiation appears to be limited as a soil quality indicator, it maybe useful as research tool to separate abiontic enzyme fraction from activity of viable microbial biomass.

Using microwave technology was processed a hazardous metal hydroxide sediment sludge as advantageous alternative to jam on the leachate of toxic heavy metal ions such as Cu2+, Zn2+, Cr3+, Pb2+ (Gan, 2000). The effectiveness of microwave assisted binding and immobilisation of the metal ions within the sediment solids was studied in conjunction with an evaluation of microwave energy efficiency in comparison to the more conventional convective heating and drying processes.

The experiments were carried out on a sediment sludge resulted from a PCB manufacturer, dewatered through a compression and filtration process before microwave treatment. A semi-industrial combined convective heating and microwave oven was used as microwave equipment. An electric air fan heater was externally attached to the microwave oven so that hot air, at a constant temperature of 96°C, can be transported to and circulated within the microwave oven. Such a combination allows the heating and drying of solids to take place in three distinctively different modes of (i) sole heat convection; (ii) sole microwave heating and (iii) simultaneous microwave and convective heating and drying (combined mode). The moisture removal from the sediment sludge was determined by differentiating the total sample weight before and after the drying process.

It was found that the energy consumption per unit mass at the combined mode decrease with increasing total solid mass. Also, it was argues that microwave metal ion binding proved an efficient procedure to minimise or to prevent the leaching of heavy metal ions from hazardous sludge.

An other environmental application of microwave have as starting point the observation of many epidemiological studies that a correlation exists between the exposure to particulate mater and adverse human health effects at concentration commonly found in urban areas. Thus, microwave technique was used as sample preparation procedures for the determination of total and water-soluble trace metal fractions in airborne particulate mater (Karthikeyan et al., 2006).

Different size fractions of atmospheric particulate matter namely total suspended particulate matter, particulate mater with diameter ≤ 10.0 µm, and particulate matter with diameter ≤ 2.5 µm were collected directly onto different filter substrates

(Teflon, Zeflour, Quartz) and a closed vessel microwave digestion system was used. Half of the filter samples were subject to microwave digestion program (with HNO3-HF-H2O2) and after that total metals were determined by inductively coupled plasma-mass spectrometry. The remaining halves of the filters were employed for the microwave-assisted extraction of water-soluble trace metal fractions.

The experimental protocol for the microwave assisted digestion was established using two different standard reference methods and finally the application of the proposed microwave-based sample preparation methods was demonstrated by analysing trace elements in airborne particulate samples from different emission sources. The results show that these methods are very simple, fast, reliable and quality-assured. They can be used for the analysis of numerous air particulate samples collected from a network of air quality monitoring stations.

5. Conclusions

The microwave energy may be used with good

results in different related fields to assure the environment’s protection. The main applications of microwave-assisted chemistry are in extraction of some pollutants from different matrices or in their destruction. The principals’ advantages of this technique are due to the shorter reaction time, inexpensive materials, easy application and lower contamination level. Other advantages are minimal volumes of reagents that are required, lower energy consumption and more reproducible procedures. References Agazzi A., Pirola C., (2000), Fundamentals, methods and

future trends of environmental microwave sample preparation, Microchem. J., 67, 337-341.

Al–Harahsheh M., Kingman S.W., (2004), Microwave-assisted leaching – a review, Hydrometallurgy, 73, 189-203.

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______________________________________________________________________________________________

ENVIRONMENTAL POLLUTION WITH VOCs AND POSSIBILITIES

FOR EMISSION TREATMENT

Liliana Lazăr∗, Ion Balasanian, Florin Bandrabur

“Gh. Asachi” Technical University of Iasi, Faculty of Chemical Engineering, Department of Engineering Inorganic Substances, 71A D.Mangeron Bd., 700050 - Iasi, Romania

Abstract Volatile organic compounds (VOCs) constitutes an important class of environmental pollutants, which, together with other contaminants as NOx, SOx, CO, NH3, CO2 etc. participate in degradation of atmosphere and exhibit a potential risk for human health. VOC emissions may be generated in more than 25 percentages through the use of solvents in different industrial or house holding activities. For applying a certain plan concerning the pollution reduction, any user of organic solvents containing VOCs should accomplish a proper management of these ones, such as the concentrations of the pollutants to frame within the limits regulated by the European legislation. The pollutant emission containing VOCs may be subjected to a treatment process, established concordant to their characteristics and provenience, as well as to the possibility and the cost of implementation in the technological process. In this paper, a scheme for trapping and treatment of the gas emissions resulted from the activities related to degreasing in organic solvents containing VOCs is presented. Key words: VOC, environmental pollution, solvents, emissions, catalytic incineration


1. Introduction

The volatile organic compounds are considered to be organic substances, excluding methane, which contain carbon and hydrogen, total or partial substituted by other atoms, which exhibit a vapour pressure higher or equal to 0.01 kPa at 20 0C and which may be found in gas or vapour state in the operation conditions carried-out in units (EC Directive, 1999). Due to their specific characteristics (high volatility, harmful, toxic or carcinogenic effect), the VOC pollutants show a potential risk for human health, even at low concentrations in gas emissions. In consequence, the VOC pollution reduction and control became a major problem at the international level in the last decades. The basic objectives of the environmental policies consist in ensuring the protection and conservation of the nature, as well as durable use of its components in accordance to regulations regarding the integrated pollution prevention and control foreseen by the IPPC

Directive (EC Directive, 1996). The VOC environmental impact consists in

direct effects, as a result of their specific characteristics, as well as in indirect effects that owe to their participation in reactions occurring in the presence of atmosphere constituents and solar light. In these reactions, active radicals that disturb the normal cycle of nitrogen in atmosphere may form. VOC pollutants are able to participate in depletion of the ozone layer, in enhancement of the greenhouse effect, in appearance of the photochemical smog (Dumitriu and Hulea, 1999).

The effects of VOCs on the human body depend on their chemical nature, concentration in air and duration of their action. Most frequently, the action of these pollutants occurs at low concentration resulting in a chronic or a long–term effects that need long period to lead to changes in the human health. Very high concentrations yield to acute or immediate effects, cases when the body reactions appear fast. The VOCs may action not only upon the exposed


Lazar et al. /Environmental Engineering and Management Journal 6 (2007), 6, 529-535

530

population, but also on the descendents, leading to transmissible hereditary mutations or congenital malformations.

Evolution of the environmental pollution with VOC varied with the level of industrialization and urbanization of the society, in the last decade being registered a continuous decrease due to the more and more severe legislative regulations foreseen by the Directive 1999/13/EC and Directive 2004/42/EC. The limit values established for VOC emissions resulted from using solvents in different activities and plants, forced the economic agents to find practical solutions for reduction at the sources of emissions and to implement them in the technological process.

The European regulations concerning VOCs pollution prevention and control (EC Directive, 1999; EC Directive, 2004) are transposed in Romanian legislation by Governmental Decision HG 699, (2003) modified and added up through HG 1902 (2004). The Romanian economic agents that use organic solvents containing VOC have to implement the legislative regulations up to 31.12.2007. Romania engaged to reach, in 2010, the limit of 523 .103 tones VOC emissions, meaning a reduction of 15 % toward 1990 (616 .103 tones VOC). Implementation of Directive 1999/13/CE in Romanian plants is achieved by collaboration with Germany, concordant to the PHARE Twinning Project RO/2002/IB/EN/02 (PHARE Program, 2002).

Two objectives are foreseen in this paper: analysis of the main VOC pollution sources in Romania and, especially, in the region of Moldova and settlement of a scheme for trapping the VOC emissions aiming at achieve the catalytic depollution. For selection of the VOC emissions treatment method, any economic agent has to carry-out a mass balance of the solvents that should constitute the basis for calculation of the composition and flow of the pollutants emission. In this context, this paper presents the mass balance calculated for the case of using solvents in order to achieve the degreasing of the metallic surfaces. The solvents mass balances allow the establishment of VOC consumption, of the threshold value of the emission, as well as of limit value of fugitive and total emissions in order to conform to the operation conditions of these types of equipments. By solving the mass balance, the solvents user verifies if it conforms to the limit values for VOC emissions in the residual gases or in the fugitive emissions, but also to the limit values of the VOC total emissions. The mass balance analysis permits the establishment of a plan for reduction or selection of a certain treatment method for the gas emissions that meets the regulations. 2. Environmental pollution with VOC 2.1. VOC polluting sources in Romania

From the point of view of the total volume of pollutant VOC emitted in atmosphere, as well as of the affected sites, the mobile sources (road, railway,

air or sea conveyance) are situated on an important place in majority of the countries of the world. These are followed by the technological stationary sources (steam power plants, chemical and metallurgic industries, varnishes and paints industries, food and pharmaceutical industries, different economic agents which use organic solvents municipal, medical or industrial incinerators, etc.) and then, by the natural sources (volcanoes, gas emanations from soils, decomposing processes of organic substances in soils, woods burning etc.).

Analysis of the report from 2001 of Ministry of Water, Woods and Environmental Protection, Romania (MAPPM Romania, 2001), realized on the basis of the stock-taking and classification of the sources which generate VOC emissions (by EEA/EMEP/CORINAIR method), evidenced the fact that (Fig. 1), the main pollutants sources are the transportations (> 20 %), solvents manufacture and use (≅ 25 %), plants for fuel extraction, distribution and burning (> 15 %).

The biggest number of VOC emissions results form different activities or plants that use organic solvents. The main categories of activities that lye under the incidence of the Directive 1999/13/CE are: protective covering of the surfaces (metal, wood, plastics, textile, fabrics, leather) and car painting; dry cleaning; cleaning and degreasing of the surfaces; covering with adhesive; covering of the rolls; shoes manufacture; covering agents, varnishes, inks and adhesives manufacture; pharmaceutical products manufacture; printing; rubber conversion; extraction and refining of the vegetal oils and animal fats; wood impregnation (EC Directive, 1999).

In Romania, the stock-taking of the VOC pollutant emissions is done by the National Institute of Research – Development for Environmental Protection, in accordance to codification of the activities and consumption thresholds established through the legislative regulations (HG 699/2003; HG 1902/2004). Reporting of the statistic data is done by the M.M.G.A. from Romania to the European Environmental Agency (www.mmediu.ro).

On the basis of the national inventory realized at the level of the year 2005, it was observed that on the whole territory of Romania, 832 functioning plants existed, which have been developing activities using organic solvents containing VOCs (PHARE Program, 2004).

In order to evidence the percents of every type of activity that uses solvents, the data of the national inventory were analyzed (Implementation Plan, 2004), the results being presented in Fig. 2. The most important fraction is constituted by the activities of wood surfaces covering (> 25 %), followed by other diverse activities of covering and cleaning of the metallic surfaces, plastics, textiles and fabrics (≅ 35%), and car painting (7 %).

Environmental pollution with VOCs and possibilities for emission treatment

531

other mobile sources and units3%

agriculture8%

waste treatment and disposal

1%

use of solvents and other products

17%

productionprocesses

7%

fossil fuelextraction

and distribution5%

burning in processing industries

1%burning plants non-industrial

8%

burning in energetic and transformation

industries 2%

other sources30%

road conveys18%

other mobile sources and units3%

agriculture8%

waste treatment and disposal

1%

use of solvents and other products

17%

productionprocesses

7%

fossil fuelextraction

and distribution5%

burning in processing industries

1%burning plants non-industrial

8%

burning in energetic and transformation

industries 2%

other sources30%

road conveys18%

Fig. 1. Classification of the VOC pollution sources in Romania

wood surface covering

26.7%

other types of coverings 17.8%

car painting; 7.0%

surfaces cleaning8.9%

others 10.8%

varnishes, inks, adhesives

manufacture7.9%

adhesivecoverings4.9%

shoesmanufacture 10.3%

dry chemicalcleaning

5.6%

wood surface covering

26.7%

other types of coverings 17.8%

car painting; 7.0%

surfaces cleaning8.9%

others 10.8%

varnishes, inks, adhesives

manufacture7.9%

adhesivecoverings4.9%

shoesmanufacture 10.3%

dry chemicalcleaning

5.6%

Fig. 2. Percents of the most important activities/plants that use organic solvents containing VOC in Romania

The analysis of repartition of the technological

sources on counties evidences that, in the counties of Moldova, may be found around 25 % from the total of the plants that use organic solvents containing VOC (Fig. 3).

Fig. 3. Repartition on counties of the activities /plants that

use organic solvents

3. Possibilities to reduce pollution with VOC

In general, the organic solvents belong to the group of the aromatic hydrocarbons, oxygenated compounds (alcohols, ketones, esters, and glycolic ethers), chlorinated derivatives etc. A part of these solvents belong to the classes of carcinogenic, mutagenic and toxic substances (CMR substances –

carcinogenic, genetic modifications inducers, harmful for reproduction). Solvents are classified as a function of risks phases or combination of these ones (attributing the R indicative) and as a function of the effects on health in conformity with the legislative regulations (HG 699, 2003; HG 1902, 2004; SR-13253/1996).

3

525

12

13

4

32

9

34

51

11

6

24

14

49

32

7

249

7

612

30

3810

17

24

11

21

16

10

2

10

9

18

~ 16 %of the total plants from the country

33

525

12

13

4

32

9

34

51

11

6

24

14

49

32

7

249

7

612

30

3810

17

24

11

21

16

10

2

10

9

18


33

525

12

13

4

32

9

34

51

11

6

24

14

49

32

7

249

7

612

30

3810

17

24

11

21

16

10

2

10

9

18


3

Fig. 4. Repartition on counties of the activities of surfaces cleaning, car painting and different surfaces covering

(metallic, plastics, wood, textile etc.)

Since even for low VOC concentrations, the gas emissions exhibit a certain degree of risk upon the human health, the economic agents that exploit the equipments specified in Directive 1999/13/CE have the obligation of applying measures of control and reduction of environmental pollution with VOC. In this context, as a function of the solvent containing VOC consumption threshold, the economic agent must obey the limit value of VOC emissions in the residual gases and the fugitive emissions or the limit value of the total VOC emissions (Table 1) and to implement a plan for pollution reduction at source.

Table 1. Emissions limits imposed by the consumption

threshold of solvents containing VOC (HG 699, 2003)

Consumption

threshold of solvents containing VOC,

t/year

Emission limit

mg C/Nm3

Diffusive emission % form the used

amount of solvent

5 – 15 100 25

> 15 50 75 20

In general, for reduction of the environmental

pollution with VOC, there may be applied the following activities: treatment of gases resulted from a process, with or without solvent recirculation, reduction of emissions during the technological operations; replacement of the polluting processes with new ones that do not involve emission of volatile organics in atmosphere.


532

Treatment methods are grouped in two categories: non-destructive (condensation, adsorption, membrane separation) or destructive (thermal incinerators, catalytic incinerators, catalytic photo-degradation, and bio-degradation. The non-destructive techniques allow the recovery of the solvents for their use as raw material, while the destructive techniques are utilized for oxidative treatment of VOC emissions, with recovery of the heat resulted in the process (EPA, 1995; Dumitriu and Hulea, 1999). Selection of a certain treatment method is done considering: the process that generates pollutant emissions with VOC, the nature and flow of the emission, the minimum, average and maximum concentrations of VOC, the costs etc. These criteria involve a good management of the solvents within the technological phases of the activities that lead to VOC emissions (EPA, 1995; Lazaroiu, 2000).

4. The mass balance of the solvents in a plant for surfaces degreasing 4.1. Solvents management

Within a technological process for surface

covering with decorative-protective purposes, a stage for chemical degreasing in organic solvents is foreseen aiming at partially removal of the animal and soluble vegetal fats. Usually, degreasing occurs in a cave with a parallelepiped shape, containing a covering device and manufactured by materials resistant to the action of the solvents.

Due to degreasing of the metallic surfaces in organic solvents, result VOC emissions that should be controlled such as the emission limit value, concordant to the solvent consumption threshold, not to be exceeded. The control of these emissions involves a good management of the solvents, consisting in establishment of the mass balance for the degreasing industrial activity. The solvent consumption for a range of 12 months is determined through the mass balance, and the proof of fulfilling certain requirements regarding the limit value of fugitive and total emissions, respective, in accordance to the regulation is achieved (Table 1).

For the accomplishment of the solvents mass balance, all the input and output flows containing VOC should be considered. In Fig. 5, the input and output flows that constitute the basis of the solvents mass balance are presented (HG 699, 2003). 4.2. Calculus of the solvents mass balance

Taking into account the solvents management

plan and the methodology for calculus of solvents mass balance (HG 699, 2003), the mass balance for the cases of four solvents frequently used for degreasing of metallic surfaces, such as carbon tetrachloride, ethylene trichloride, acetone, butanol, toluene, is further presented. Considering the yearly necessary amounts of solvent ranged between 5 and 15 t/year, in Tables 2 and 3, the solvents consumption and the mass balance are shown.

Fig. 5. The input and output flows needed for calculus of the solvents mass balance


533

The solvents consumption (CS) is the sum of

the solvents partial consumption, established as a result of using the solvents purchased during 12 months (I1). From this amount, the solvents recovered for reusing are subtracted (O8), in the case they were not sold as products (O7) or used within the same process (I2). The calculus formula may be written as, Eq.(1):

CS = (I1 + I2) – (I2 + O8) = I1 – O8 (1)

Total emission (E) is the sum of fugitive emission value (F) and residual gases controlled emission (O1), Eq. (2): E = F + O1 (2)

Fugitive/diffusive emissions (F) should be

determined using the indirect method, subtracting from the used solvents flows (excepting I2) the flows that are not framed in the category of diffusive flows according to Eq. (3):

F = I1 – O1 – O5 – O6 – O7 – O8 (3)

The determined fugitive emissions should

not exceed the limit value regulated by legislation (HG 699, 2003, HG 1902, 2004). The limit value of the fugitive emission is calculated with formula Eq. (4):

( )F 1 2X 100 F I I , %= ⋅ + (4)

From the analysis of the solvents mass balance one can see that the fugitive emissions exceed the regulated limit value, meaning 25 % from the total solvent consumption (Table 1). The high value of the fugitive emissions leads in exceeding of the limit proposed for the value of the final emission, which is 100 mg C/Nm3 concordant to regulation (EC Directive, 1999). The total organic carbon content of the emission (mg C/Nm3) increases with the increase in the number of carbon atoms from the solvent molecular structure. At the same time, one may observe that the requirements of the Directive 1999/13/EC are not satisfied. These requirements have foreseen limit concentrations of 20 mg C/Nm3 for an emission flow of 100 g/h, in the case of using organic solvents containing halogenated VOC and 2 mg C/Nm3, respectively, for an emission flow of 10 g/h, in the case of using organic solvents containing carcinogenic or mutagenic VOC.

The solvents mass balances accomplished for the presented cases show that it is necessary a rigorous control of the emissions such as, finally, not to result more than 25 % fugitive emissions inside the industrial precinct and, in the same time, environmental pollution should be prevented by a good trapping of the residual emissions.

Table 2. Establishment of solvents consumption for degreasing of metallic surfaces

Amount yearly

consumed and disposed, Solvent Chemic

al formula

mol C

Molecular weight kg/mol

Density, kg/m3

kg/year L/year

Content of VOC,

%

Yearly VOC inputs,

I1, kg/year

Content of

impurities, kg/year

Target emission*

) kg/an

750 1203.8 723.8 26.25 91.9 Carbon tetrachloride CCl4 1 152 1.605 15000 24075.0 96.5 14475.0 525.0 1837.5

750 1103.3 727.5 22.5 78.8 Ethylene trichloride C2HCl3 2 131.5 1.471 15000 22065.0 97 14550.0 450.0 1575.0

750 592.5 716.3 33.8 118.1 Acetone C3H6O 3 58 0.79 15000 11850.0 95,5 14325.0 675.0 2362.5 750 607.5 712.5 37.5 131.3 Butanol C4H10O 4 74.12 0.81 15000 12150.0 95.0 14250.0 750.0 2625.0 750 652.5 723.8 26.3 91.9 Toluene C7H8 7 92.14 0.87 15000 13050.0 96.5 14475.0 525.0 1837.5

*)Multiplying factor for target emission = 3.5

Table 3. Mass balance for the solvents used in degreasing of metallic surfaces

Solvent

Yearly VOC

inputs I1, kg/year

O1, kg/year 50%I1

O2, kg/year

5%I1

O3, kg/year

O4, kg/year 40%I1

O5, kg/year

O6, kg/year

5%I1

O7, kg/year

O8, kg/yea

r

O9, kg/year

F, kg/year

XF , %

Total emission

E, kg/year

Flow C, kg C/ year

Conc. mg C/m3

723.8 361.9 36.2 0 289.5 0 36.2 0 0 0 325.7 45 687.6 67 55 Carbon tetrachloride 14475.0 7237.5 723.8 0 5790.0 0 723.8 0 0 0 6513.8 45 13751.3 1333 55

727.5 363.8 36.4 0 291.0 0 36.4 0 0 0 327.4 45 691.1 155 140 Ethylene trichloride 14550.0 7275.0 727.5 0 5820.0 0 727.5 0 0 0 6547.5 45 13822.5 3098 140

716.3 358.1 35.8 0 286.5 0 35.8 0 0 0 322.3 45 680.4 519 875 Acetone 14325.0 7162.5 716.3 0 5730.0 0 716.3 0 0 0 6446.3 45 13608.8 10373 875 712.5 356.3 35.6 0 285.0 0 35.6 0 0 0 320.6 45 676.9 538 886 Butanol 14250.0 7125.0 712.5 0 5700.0 0 712.5 0 0 0 6412.5 45 13537.5 10766 886 723.8 361.9 36.2 0 289.5 0 36.2 0 0 0 325.7 45 687.6 770 1180 Toluene 14475.0 7237.5 723.8 0 5790.0 0 723.8 0 0 0 6513.8 45 13751.3 15396 1180


534

Fig. 6. The block-diagram for the process of catalytic purification of pollutant emission resulted stationary sources

5. Reduction of pollution with VOC in the case of a degreasing plant

For obeying the limit values of VOC

emissions in accordance to Directive 1999/13/CE, the solvents users may choose a reduction plan. In this context, one may appeal to the primary measures for pollution reduction in the case of these types of emissions: a) taking into account the primary measures for replacement of solvents containing high amounts of VOC with other containing lower amounts; b) insertion of a new technology for treatment of the residual emissions inside the technological flux.

In the case of emissions of gases containing low VOC content (< 5000 ppm COV), an advantageous treatment is the oxidative destruction in the presence of a catalyst, process named catalytic incineration. This is based on the principle of thermal–oxidative destruction of VOC, in the presence of a catalyst, ensuring conditions for a total oxidation reaction up to formation of CO2 and H2O. The catalytic incinerators are constructed in function of the user specific requirements, the nature and concentration of the organic pollutant, the amount of the treated effluent and the method of heat recovery (Dumitriu and Hulea, 1999; Heck and Farrauto, 2002).

In figure 6, the block-diagram for the process of catalytic treatment of gaseous emissions polluted with VOC resulted from the stationary technological sources, is depicted.

In general, the incineration technological process involves unit operations such as: trapping and transport of the pollutant gases, separation of the components that may occur to catalyst deactivation, heating of the gases based on the external energy or on recovered heat, mixing with oxidizing agents, catalytic treatment and heat recovery (Balasanian and Lazar, 2002).

6. Conclusions

In this paper, an analysis of the polluting sources with VOC was accomplished, being also done a solvents mass balance for the process of decreasing of the metallic surfaces, that constitute the basis of the solvents management plan, as well as the resulting emissions reduction plan.

The volatile organic compounds are an important category of environmental pollutants being emitted into the atmosphere in a significantly amount as a result of the industrial activities were organic substances are used as solvents or diluents. The diversity, from the point of view of the chemical nature and the physical characteristics specific to the solvents (high volatility, flammability, toxicity, specific odor, carcinogenic effect etc.), confers to VOC emissions a major risk for the human health, even when they are present in low concentrations. For these reason, the prevention, control reduction at the source of pollution with VOC is required, obeying the admissible maximum concentration regulated by Directive 1999/13/CE.

Any user of solvents containing VOC should give a great importance to the management solvents, that is based on the mass balance, which is further used for establishment of solvents consumption for a period of one year, proving the compliance with the limit values for the diffusive emissions, in conformity with the yearly consumption threshold, regulated by law (HG 699, 2003).

The solvents mass balance is utilized as a system for control and management and for the reduction of the costs of plant operation. The economic agents gain, in the first time, a total view on using domains that need a replacement of the utilized solvents being thus, able to recognize easier the weak points of the industrial activity.


535

For complying with the limit values

concordant to the Directive 1999/13/CE, the economic agents may achieve a plan for reduction of the environmental pollution with VOC, choosing the replacement of the solvents containing high amounts of VOC, with others having a lower content or inserting in the technological flux of a technology for residual gases treatment. References Balasanian I., Lazar L., (2002), Waste Management,

(Chapter 6.2. Removal and Treatment of Gas and Vapour Polluants), Oros V., Draghici C. (Eds), EnvEdu Series, Transilvania University Press, Romania, Brasov, 150-171.

Dumitriu E., Hulea V., (1999), Heterogeneous Catalytic Methods Applied in the Environment Protection, BIT Press, Iasi, Romania (In Romanian).

EPA, (1995), Survey of Control Technologies for Low Concentration Organic Vapor Gas Streams, U.S. Environmental Protection Agency's (EPA's) and Office of Research and development (ORD), Control Technology Center, EPA-456/R-95-003, May 1995, on line at: http://www.epa.gov/ttn/catc

EC Directive, (1996), Directive of concerning integrated pollution prevention and control, Directive 96/61/EC.

EC Directive, (1999), Directive on the limitation of emissions of VOCs due to the use of organic solvents in certain activities and installations, Directive 1999/13/EC.

EC Directive, (2004), Directive on the limitation of emissions of volatile organic compounds due to the use of organic solvents in certain paints and varnishes and vehicle refinishing products and amending Directive 1999/13/CE, Directive 2004/42/EC.

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control: Commercial Technology, 2en ed., Wiley-Interscience, New York - USA.

HG 699, (2003), Governmental Decision 699/2003 concerning the establishment of measures for reduction of emission of volatile organic compounds resulted from use of organic solvents in certain activities and plants, published in Romanian, Official Journal M.Of. No. 489/8.07.2003.

HG 1902, (2004), Governmental Decision 1902/2004 for modifying and adding up of HG no. 699/2003, published in Romanian Official Journal , M. Of. No. 1102/25.11.2004.

Lazar L., (2006), Air treatment for volatile organic compounds removal, Ph.D. Thesis, Gh. Asachi Technical University of Iasi, Romania.

Lazaroiu Gh., (2000), Modern Technologies for Depollution of Air, AGIR Press, Bucharest, Romania (in Romania).

MAPPM Romania (2001), Inventory of the emissions of the atmospheric pollutants at national level for the year 2001, On line at: http://www.mappm.ro/legislatie/inventar%202001.html

PHARE Program, (2002), Implementation of the VOC’s, LCP and Seveso II Directives, Twinning project between the Romanian Ministry of Environment and Water Management and the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Twinning Project RO/2002/IB/EN/02.

SR 13253, (1996), Standard concerning the packaging and labeling of the hazardous substances and compounds.

The inventory of the atmospheric pollutants at national level including heavy metals and persistent organics for the years, 2000 and 2001, using the methodology EEA/EMEP/CORINAIR (2000), ICIM Bucharest, On line at: www.mmediu.ro

Preliminary inventory of the activities and plants that lye on the incidence of the regulations of the Directive1999/13/CE, MMGA, by APM (2002, 2003, 2004). On line at: www.mmediu.ro



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SUSTAINABLE IRRIGATION BASED ON INTELLIGENT

OPTIMIZATION OF NUTRIENTS APPLICATIONS

Codrin Donciu∗, Marinel Temneanu, Marius Brînzilă

“Gh. Asachi” Technical University of Iasi, Faculty of Electrical Engineering, 53 Mangeron Blvd., 700050, Iasi, Romania

Abstract The present paper proposes the design of a modules system of measurement and control of data distributed transmission, implemental on automatic irrigation systems of central pivot or linear movement type. By this it is intended to obtain a complex irrigation system that allows optimization of nutrient application. Key words: Power line communication, soil conductivity, precision irrigation


1. Introduction

Nutrients such as phosphorus, nitrogen, and potassium in the form of fertilizers, manure, sludge, irrigation water, legumes, and crop residues are applied to enhance production (Shifeng et al., 2004). When nutrients are applied in excess of plant needs, they can wash into aquatic ecosystems where they can cause excessive plant growth, which reduces swimming and boating opportunities, creates a foul taste and odor in drinking water, and kills fish. In drinking water, high concentrations of nitrate can cause methemoglobinemia, a potentially fatal disease in infants also known as blue baby syndrome. They are a lot of directive adopted by the Council of the EU concerning the nutrients policy. In December 1991, was adopted Nitrates Directive. The objectives of the directive are to ensure that the nitrate concentration in freshwater and groundwater supplies does not exceed the limit of 50 mg NO3- per liter, as imposed by the EU Drinking Water Directive, and to control the incidence of eutrophication. Having set the overall targets, the directive requires individual Member States, within prescribed limits, to draw up their own plans for meeting them. Cadmium and its compounds are toxic to human beings and therefore appear on the EU’s action list. With the exception of phosphate slag, which is a by-product of steel

production and in decreasing supply, almost all phosphate fertilizers contain traces of cadmium.

After collaboration between EFMA (European Fertilizer Manufacturers Association) and IFA (International Fertilizer Industry Association) the Code of Best Agricultural Practices was developed. The recommendations provided by the codes encourage appropriate application rate, correct timing of the application and the use of a suitable type of fertilizer and a correctly calibrated fertilizer spreader (Sun et al., 2000).

During the last few years, in the economically advanced countries a new notion appeared referring to the agricultural practicability called “precision agriculture” one of its constituents being “the precision irrigation”. This new approach supposes the entrapment of new multidisciplinary technologies on the classical structures, such as the satellite geographical localization, distributed measurements and transmissions, micro informatics, broadening the view that in the maintenance and exploitation works of the agricultural crops the heterogeneity of the working plot of land could be taken into account. In the traditional agricultural system the cultivated plot of land was evenly treated even though it is known for a fact that a plot of land is extremely variable from the viewpoint of: soil fertility, topography, parasites and weeds attack. Precision agriculture has


Donciu et al. /Environmental Engineering and Management Journal 6 (2007), 6, 537-540

538

as purpose a modular administration of incomes (seeds, irrigation water, fertilizers, fungicides, herbicides, insecticides) by adapting the works of the soil, sowing, and fertilizers to the heterogeneity characteristics of the plot.

The precision agriculture notion is based on the information provided by the production maps: a combine equipped with a production recorder for instance, connected to a satellite positioning (GPS), allows getting a production map on a certain plot. This information associated with other agronomical data ensures the income modulation with respect to the plot heterogeneity. In order to become e operational, these techniques must be joined with a series of agronomical models, only after this stage the decision can be finalized. The disadvantage of this method is that the investigations can be realized only in the absence of the crops and not during their vegetation period. Nevertheless, in opinion of the precision agriculture supporters, this can replace the side effect of the treatments evenly applied to the plot in the case of the conventional agriculture, through adapting the various actions to the plot characteristics variability. This way the negative impact of intensive treatments upon the environment is avoided.

2. System architecture

The present paper proposes the realization of

measurement and control modules of distributed data transmission, implemental on automatic irrigation systems so that it may lead to obtaining of an intelligent system of irrigation combined with automatic nutrients injection, relying on the sensory investigation of the environment and soil parameters conditions. The decisional algorithm of the control centre prescribes combined irrigation recipes according to the exploited crop and to its development specificity, and the investigation is carried out at irrigation cell level, modularly. Data flux communication has as a physical support the existent infrastructure of power supply of the automatic irrigation systems and is developed through the Power Line Communications technique (Benzekri et al., 2006). The system architecture is so conceived that it should allow its implementation on the automatic irrigation systems of both circular movement (central pivot), and linear movement.

In order to reach the notion of precision agriculture (Yang et al., 2006), which represents a model in progress of implementing in all the very developed countries and has in view a modular administration of incomes in terms of the plot heterogenic characteristics, the project proposes the introduction of a sensory modules network to entail a division of the farming field into characterization (Zhao et al., 2007).

The intelligent irrigation system architecture is structured on five main levels, as follows: • the irrigation modules level, which join the

automatic irrigation systems on angular or linear movement and which have as main function the

controlled command of the electro valves for the admission of the water-nutrients mixture, in accordance with the recipes prescribed by the control;

• the sensors modules level, which are fixed and placed at the ground, having as main purpose the sampling through sensors of the surrounding cell characterization data and their transmission towards the control centre;

• the nutrients injection batteries level, with the role of injecting nutrients into the irrigation water, in terms of the concentration prescribed by the control centre (Ruiliang et al., 1999);

• the data flux transmission through PLC level, has as physical support the network of the power supply of the engines operating on the automatic irrigation systems and water pumps and realizes the data transfer between the control centre on the one hand and the irrigation module and the nutrients injection batteries on the other (Kubota et al., 2006);

• the decisional level, based on the data resulted from the sensors modules level and those extracted from its own data basis, of combine irrigation recipe, delivers the execution commands to the injection batteries regarding the irrigation output and the characterization cell geographical localization (Mohan et al., 2003).

The general architecture of the intelligent irrigation system is shown in Fig. 1. There can be noticed the existence of two independent circuits, one of water supply and one of power supply. The water supply circuit CAA makes the junction between the water supply source AA and the nutrients injection batteries BIN. This circuit converts into combine supply circuit CLC, after the nutrients injection with the pulverization nozzles of the irrigation module MI. The electric circuit powers up the engines and the pumps afferent to the automatic irrigation system and is the data transmission physical environment.

Fig. 1. The intelligent irrigation system architecture

Sustainable irrigation based on intelligent optimization of nutrients applications

539

The irrigation module is set up at the level of

the mobile arms of the automatic irrigation system and it is made up of the communication interface IPCL, the microchip control device µP, the radio receiver RR and the electro valve EV. On the MI module movement, the identification of the membership to a characterization cell is performed on the grounds of the entering its range of action. The emission power of the sensors modules MS is limited within the cell and towards its detection there interferes the criterion of the emission maximum.

Following the communication settlement between the sensors module transmitter and the irrigation module receiver, the data are transmitted by the command device µP to the PLC interface, joined with the supply circuit of the operative electrical engine (Sohag et al., 2005). By the PLC transmission the useful information is received by the control centre CC, on a computer server. As a consequence of the interpretation of the response type data provided by the characterization cells sensors are taken the control decisions of reaching the limits of the nutrients concentrations and relative humidity imposed by the data basis. The quality and quantity commands are transmitted by the PLC system to the nutrients injection batteries, providing the combine irrigation agent to the pulverization nozzles, to the volume controlling electro valves belonging to the irrigation module.

By the communication system PLC useful data are delivered as modulated signal. The signal is of the broadband type and the physical environment enables multiple operations roll on the same existent infrastructure.

The hardware architecture of the sensors module is shown in Fig. 2 and is com posed by a set of sensors specialized on the climatic parameters detection (temperature, humidity, dew point, speed, direction and movement sense of air masses, precipitations) and a set specialized on the soil parameters detection (conductivity, humidity). For the air relative temperature and humidity measurement it is used an incorporated sensor on digital output STU, made in CMOS technology, which makes it thermally safe and stable. This generates a useful signal of superior quality, has a very quick response time and insensibility at external noises (EMC). The data delivered by this sensor are used to forecast the degree of the water evaporation off the ground. The need to utilize the rain gauge sensor type (SP) comes from that the irrigation procedure interruption, during precipitations, following the data provided by the soil humidity sensor, happens late because of the needed time of water permeating through the ground, up to the depth where the humidity sensor is set up. The data coming from the anemometer SV are used to eliminate irrigation unevenness caused by wind blasts.

At the ground level are set the conductivity sensor SC, the humidity sensor SU, on whose account will be supplied the input data for the estimation

procedure of the relative nutrients and humidity concentration. The bidirectional communication with the sensors block is performed through the microchip µP and is of the serial type. As the sensors module is an independent system it is equipped with a control keyboard and a LCD screening. The radio data delivery to the irrigation module is done by the transmitter ER, having the transmission force so adjusted that it should not surpass the characterization cell by more than half the radius. The assembly supply is performed by a dry B battery.

Fig. 2. Hardware architecture of the sensors module MS The control centre is the physical support of

the decisional algorithms which operate, relying on the data resulted from the level of the sensors modules the actions of the executor elements, the actors. The data basis found at this level contains information referring to the leguminous species classification in terms of the water consuming and the absorption capacity and it designs irrigation graphs regarding the cultivated species, zone climatic factors, culture denseness and rows orientation, plant habitus, root system and vegetation stage. Besides, beginning with this level is programmed the time diagram start (the culture initiation) and the spells designated for the maintenance works.

The Intervention and Monitoring Centre CIM designates the interface with the human operator in the process of supervision and monitoring the control actions elaborated by CC and allows the effectuation of modifications in the decisional algorithms development. Also, starting with this level can be completed or modified (upgrade software) the data basis with respect to the irrigation networks. Because the control centre is configured by the server, one can access it from any geographical area where there is internet access point. The TCP-IP communication between CC and CIM is provided by two dedicated virtual instruments, server and costumer. For security reasons the login to the server is permitted only on password basis. The problems identification and improvement with respect to the automatic systems irrigation are presented in Table 1.


540

Table 1. Inconvenient identification

3. Conclusions

The present paper proposes the design of irrigation intelligent system implemental on automatic systems of central pivot or linear movement type, in order to apply nutrients in optimal concentrations. The nowadays irrigation systems either are not operational, or offer the farmers the needed water at altered times, or have them use energy-intensive watering techniques that bring about large uneconomic consuming. The proposed system offers the following benefits: it offers water to the plants at the optimum moment, irrigations are done only when and where it is needed (the water consuming can be reduced up to 30%), it allows the phase fertilizations design, the water losses by infiltration are minimum, it presents a high efficiency for the watering, it creates conditions favorable to the maintenance works mechanization, it can be used at most of leguminous cultures and not only, it facilitates the applications of the modern technologies leguminous plants culture, it permits the exploitation of cultivated plots larger than 3 % for vegetable gardening, it does not need soil maintenance leveling, it permits the watering of certain cultures placed on high permeability fields, the possibility to dose exactly the irrigation water, which is very important especially on the low depth groundwater plots, favorable effect upon the microclimate (air temperature especially) which is very important in the case of certain cultures (cabbage, cucumbers, etc.), excessive irrigation is avoided (puddles), it is avoided the watering away of the nourishing substances and the irrigation is adjusted to the running vegetation stage.

References Benzekri A., Refoufi L., (2006), Design and

Implementation of a Microprocessor-Based Interrupt-Driven Control for an Irrigation System,

E-Learning in Industrial Electronics, 1st IEEE Int. Conference on, 1, 18-20 Dec., 68.

Kubota H., Suzuki K., Kawakimi I., Sakugawa M., Kondo H., (2006), High frequency band dispersed-tone power line communication modem for networked appliances, Consumer Electronics, IEEE Transactions on, 52, 44-50.

Meng H., Guan Y.L., Chen S., (2005), Modeling and analysis of noise effects on broadband power-line communications, Power Delivery, IEEE Transactions on, 20, 630-637.

Mohan S., Elango K., Sivakumar S., (2003), Evaluation of risk in canal irrigation systems due to non-maintenance using fuzzy fault tree approach, Industrial Informatics Proc. IEEE Int. Conference on, 1, 21-24 Aug, 351.

Ruiliang P., Peng G., Heald R.C., (1999), In situ hyperspectral data analysis for nutrient estimation of giant sequoia, Geoscience and Remote Sensing Symposium IGARSS '99 Proc., vol. 1, 28 June-2 July, 395.

Shifeng Y., Pei L., Okushima L., Sase S., (2004), Precision irrigation system based on detection of crop water stress with acoustic emission technique, Information Acquisition Proc. Int. Conference on, 1, 21-25 June, 444.

Sohag M.A., Mahessar A.A., (2005), Irrigation Network Regulation through CAD System, Information and Communication Technologies First Int. Conference on, 1, 27-28 Aug., 170.

Sun D., Zhang L., Xue M., (2000), The online measurements and estimation of nutrient solution in greenhouse agriculture, Intelligent Control and Automation, Proc. of the 3rd World Congress on, 3, Hefei, 28 June-2 July, 2155.

Yang L., Zhen-Hui R., Dong-Ming L., Xin-Ke T., Zhong-Nan L., (2006), The Research of Precision Irrigation Decision Support System Based on Genetic Algorithm, Machine Learning and Cybernetics, Int. Conference, 1, 15-18 Aug., 3123

Zhao Y., Bai C., Zhao B., (2007), An Automatic Control System of Precision Irrigation for City Greenbelt, Industrial Electronics and Applications, 2nd IEEE Conference on, 1, 23-25 May, 2013.

Automatic irrigation disadvantages

Detection manners used by the intelligent irrigation system

Improving actions used by the intelligent irrigation system

The unfavourable effect of the drops (in the case of average and high pressure aspersers) upon plants, especially when plants are young and blooming)

The launching in execution of the beginning of the time diagram (crop initiation mark) leads to the irrigation achievement in terms of the multiparametric graphs of the vegetation stage.

The irrigation time modification inverse proportionally with the irrigation pressure and maintaining evenly the water volume demanded by the respective cell.

The presence of the wind during the irrigation, if its intensity outruns 2.5 m/s they stay unwatered until 10-25% of the crop areas.

The information came from the SV anemometer processed by the decisional algorithm

The temporary reduction of the water volume used.

High water losses caused by the global irrigation and absence of cell level individualized information

The information from the humidity sensor (SU) and processed by the decisional algorithm

Differentiated irrigation with respect to the investigated cell demands.

Raised nutrients pollution of the phreatic layer

The information from the humidity sensor (SC) and processed by the decisional algorithm

Differentiated nutrients insertion in accordance with the investigated cell demands.

High level power consuming The information from all the sensors of the module (BS) processed by the decisional algorithm

The optimisation of the combined irrigation process (water and nutrients) by the control centre (CC)



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OBTAINING AND CHARACTERIZATION OF ROMANIAN ZEOLITE

SUPPORTING SILVER IONS

Corina Orha1, Florica Manea1, Cornelia Ratiu2, Georgeta Burtica1∗, Aurel Iovi1

1”Politehnica” University of Timisoara, P-ta Victoriei no. 2, 300006, Timisoara, Romania

2Institutul National de Cercetare-Dezvoltare pentru Electrochimie si Materie Condensata, Str.Plautius Andronescu, Nr.1, Cod 300224, Timisoara, Romania

Abstract The aim of this work was to obtain Ag - doped zeolite as antibacterial material using natural and sodium form of zeolite from Mirsid Romania with the dimensions ranged between 0.8-1.2 mm. The comparative structural characterization of natural and Ag - doped zeolite were performed using Laser Induced Breakdown Spectroscopy (LIBS), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and Infrared Spectroscopy (IR). In addition, the ion exchange total capacities for silver of natural and sodium forms of zeolite were determined. The quantitative assessment of silver amount incorporated into zeolite lattice was achieved by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Key words: Ag - doped zeolite, qualitative assessment, quantitative assessment, structural characterization


1. Introduction

In general, the sorption and ion exchange properties of zeolites, as well as, their inexpensive from the economical aspect can be advantageously used in drinking water technology (Cooney et al., 1999; Woinarski et al., 2006).

There are several studies concerning the use of synthetic and natural zeolites, e.g., A, X, Y, Z and clinoptilolite supporting metal ions (Ag, Cu, Zn, Hg, Ti) as antibacterial material in water disinfection (Inoue et al., 2002; Top et al., 2004; Rivera-Garza et al., 2000).

The mineral properties of natural zeolite from Mirsid, Romania, with 68 %, wt. clinoptilolite make it suitable for the obtaining of Ag-doped zeolite, with antibactericidal activity. It has been found that for the uniform retaining of the Ag ion with antibactericidal property, the zeolite must exhibit a SiO2/Al2O3 molar ratio at most 14, this molar ratio being ranged between 8.5 to 10.5 for clinoptilolite (Hagiwara et al., 1990). The antibactericidal activity of Ag-doped zeolite depends on the amount of Ag ions incorporated into zeolite lattice. If the Ag ions

amount is the same with the ion-exchange total capacity the bactericidal effect of the modified zeolite is very poor, due to the other form of Ag as silver oxide can be deposited on the zeolite surface. Under these conditions, it is required to prevent the deposition of such excessive silver onto the solid phase of zeolite.

The aim of our present study was the preparation and characterization of Ag – doped zeolite, with the dimensions ranged between 0.8-1.2 mm, which will be used further for drinking water disinfection. The ion-exchange total capacities of natural and Na form of zeolite from Mirsid, Romania were determined. The structural characterizations of Ag-doped zeolite with the Ag amount lesser than ion-exchange total capacity of zeolite for Ag ions were investigated relating its further utilization as antibacterial material.

2. Experimental

For this study, it was used the natural zeolite

from Mirsid (Romania), which contains 68%, wt. natural clinoptilolite.


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The preparation of Ag-doped zeolite requires two stages, i.e., in the first stage the natural zeolite was chemically treated with 2M HCl and 2M NaNO3 to obtain the sodium form. The second stage consists of the obtaining of the Ag - doped zeolite by the mixing of the sodium form of the zeolite with 0.1 N AgNO3 solution for 3 hours (Hagiwara et al., 1990).

As a previous stage for the preparation of Ag-doped zeolites the ion exchange total capacity of the zeolite for silver was determined. 1.000 g of zeolite with the dimension of pores between 0.8-1.2 mm was shaken with 25 mL of 0.1 N AgNO3 during 3, 5, 7, 12 and 14 days (Cerjan-Stefanovic et al., 2004). Once equilibrium was established water solution was separated by filtration from the zeolite phase and the Ag amount into zeolite was determined by using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) after sample mineralization. The ICP-AES analysis was made with an ICP-AES SpectroFlame spectrometer.

The thermal treatment of Ag – modified zeolite was realized in reducer environment at 500°C, when Ag - doped zeolite (Z-Ag) was formed and the thermal treatment of natural zeolite was not performed. To determine the presence of silver within zeolite lattice, the samples was analyzed by Laser Induced Breakdown Spectroscopy (LIBS). The material ablation and the excitation were performed with Q-switched Nd:YAG laser with an energy of 12-15 mJ, using an Ag standard.

The morphology and the composition of the unmodified/modified zeolite were characterized by using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Infrared Spectroscopy (IR). XRD spectra were recorded at room temperature on a BRUKER D8 ADVANCE X-ray diffractometer using Cu Kα radiation (λ = 1.54184 Å, Ni filter) in a θ: 2θ configuration. The peaks of the XRD patterns were identified using the PCPDFWIN Database of JCPDS, version 2.02 (1999). The SEM images were made in a Jeol JSM-6300LV scanning electron microscope. The AFM images were made in a NanoSurf EasyScan 2.0 atomic force microscope. The IR spectra were recorded in KBr pellet for solid compounds on a Jasco FT/IR-430 instrument. 3. Result and disscusion

The results of the ion exchange total capacity

of zeolite for silver that was determined by equilibrium of zeolite samples with 0.1 N AgNO3 are shown in Table 1 .

The form type of zeolite, e.g., natural and sodium form did not influence the ion exchange total capacity for silver ion. The Ag amount retained into zeolite as Ag-doped zeolite was 0.0065 mg/g zeolite almost twenty times smaller than the total exchange capacity of zeolite for silver, versus 0.008 mg/g zeolite (with the dimension of pores between 315-500 µm).

Table 1. The ion exchange total capacity of the zeolite

samples with 0.1 N AgNO3 solution

Zeolite type Contact time [days]

mg Ag/g zeolite

Z-N 3 0.115 Z-N 5 0.108 Z-N 7 0.102 Z-N 12 0.101 Z-N 14 0.101 Z-Na 3 0.115 Z-Na 5 0.107 Z-Na 7 0.102 Z-Na 12 0.101 Z-Na 14 0.099

Fig. 1 shows the laser spectrum of Ag-doped

zeolite versus silver standard one to identify qualitatively the presence of silver into zeolite.

320 322 324 326 328 330 332 334 3360

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6000 Ag standard

Rel

ativ

e In

tens

ity

Wavelength(nm)

*

328.16; 330.5 * - Ag

*

Z-Ag

Fig.1. The laser spectrum of Ag-doped zeolite (Z-Ag)

The comparative XRD spectra of natural and

Ag-doped zeolite (Z-Ag) are shown in Fig. 2.

6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 400

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* 21.5; 30.5 AgAlO2

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natural zeolite

Fig. 2. X-ray diffraction patterns of the natural zeolite and

of the Ag-doped zeolite The intensities of reflection observed at about

10°, 23°, and 30° corresponding to the clinoptilolite amount decreased due to the thermal treatment of Ag

Obtaining and characterization of Romanian zeolite supporting silver ions

543

- doped zeolite (Rivera-Garza et al., 2000). No major differences in the diffraction patterns

were observed due to de presence of the low amount of silver into zeolite. However, traces of AgAlO2 (21.5°; 30.5°) were identified.

Figs 3a and 3b illustrates the SEM images of natural and thermally treated Ag-doped zeolite.

Fig. 3a. SEM image of the natural zeolite

Fig. 3b. SEM image of Z-Ag Significant changes of the morphology of Ag-

doped zeolite in relation to the natural zeolite were shown in Figs. 3a and 3b, some small particles agglomerated on the zeolitic material were observed (Fig. 3b).

AFM was used to provide complementary information from both the internal and external structure of natural and Ag – doped zeolite and to image Ag particles located within the structure of zeolite. The natural zeolite consisted of particles with diameters ranged between 102.7 and 307.9 nm (Orha et al., 2007) and AFM image of thermal untreated/treated Ag - doped zeolite showed the existence of smaller particles ranged between 106.9 and 160.9 nm (Figs. 4a and 4b). With the existence of smaller particles (nanocrystals) the specific surface area increased, which means that the precipitation of silver oxide on the zeolite surface was avoided.

The IR spectra of the thermally treated Ag-doped zeolite sample (Z-Ag) and untreated (Ag-modified Z) were compared with the IR spectrum of natural zeolite (Z), and are presented in Fig. 5.

a)

b)

Fig. 4. AFM image of the Ag – doped zeolite: a) without thermal treatment; b) treated thermally at 500°C

Fig. 5. IR spectra of natural zeolite (Z), silver doped zeolite (Z-Ag) and silver modified zeolite (Ag modified-Z)

The influence of thermal treatment on Ag -

doped zeolite was clearly observed especial for the vibration bands in the range between 3000 and 4000 cm-1. Taking into account the literature data (Rivera-Garza et al., 2000; Rodriguez-Fuentes et al., 1998) the assignation of vibration bands shown in Table 2 can be proposed for the Romanian zeolite from Mirsid.

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The influence of both Ag cation and thermal treatment on the IR vibration is gathered in Table 3, and it can be underlined that the shoulder at 1205 cm-

1 corresponding the internal tetrahedral asymmetric stretching disappeared in the presence of silver. Also, small changes related to the transmittance intensity of the vibration bands at 456 cm-1, 1053 cm-1 in the presence of Ag cation were found out. The changes of the vibration bands, i.e., internal tetrahedral bending and internal tetrahedral asymmetric stretching in the presence of Ag gave information about the Ag incorporation into zeolite lattice.

Table 2. The vibration bands for Romanian natural zeolite

from Mirsid

Vibration modes Wavenumber [cm-1] Intensity Internal tetrahedral bending 456 strong

External tetrahedral double ring 604 medium

External tetrahedral linkage symmetric stretching

791 weak

External tetrahedral linkage asymmetric stretching

1053 strong

Internal tetrahedral asymmetric stretching 1205 shoulder

O-H bending 1650 wide

Table 3.The transmittance values at each wave number for unmodified/modified zeolite

Sample T1650 (%) T1205(%) T1053(%) T791(%) T604(%) T456(%) Natural zeolite 60.7356 25.014 6.72181 68.6638 42.8188 18.0681

Ag doped zeolite

58.6873 - 1.97174 63.8796 36.7916 8.58711

Z-Ag 81.0015 - 23.1584 81.0711 71.9144 38.5474 4. Conclusions

The ion exchange total capacities of natural

and sodium forms of zeolite from Mirsid, Romania with the dimension of pores ranged between 0.8-1.2 mm for silver depended slightly on the zeolite form (natural or Na-form).

The presence of Ag into zeolite was identified by LIBS and the quantitative assessment of Ag modified zeolite obtained for its use in water disinfection was achieved by ICP-AES, the Ag amount incorporated into zeolite lattice was 0.0065 mg/g zeolite. Ag amount incorporated into zeolite was about twenty times smaller than ion exchange total capacity of the zeolite for silver, this aspect being suitable for its use as antibacterial material due to the avoiding of undesired precipitation of silver oxide on zeolite surface.

The comparative characterization of natural and Ag - doped zeolite performed by XRD proved the

trace existence of AgAlO2 form into the zeolite lattice.

The existence of smaller particles in the presence of Ag proved by the structural characterization provided by SEM and AFM showed the specific surface area increasing of the Ag doped zeolite. The changes of internal tetrahedral bending and internal tetrahedral asymmetric stretching vibration bands of IR spectrum supported the Ag incorporation into zeolite lattice.

Acknowledgements

The structural analyses were made by co-operation

with University of PECS, Institute of Physics and Laser Spectroscopy within the framework of the Romanian - Hungarian bilateral scientific research Project RO-Hu-20/2002 – 2005. This study was supported by the Romanian National Research of Excellence Programs-CEEX, Grant 631/03.10.2005 - PROAQUA and 115/01.08.2006 SIWMANET. References Cerjan-Stefanovic S., Siljeg M., Bokic L., Stefanovic B.,

Koprivanac N., (2004), Removal of metal – complex dyestuffs by Croatian clinoptilolite, Proceedings: 14th International Zeolite Conference, 1900-1906.

Cooney E.L., Booker N.A., Shallcross D.C., Stevens G.W., (1999), Ammonia removal from wastewaters using natural australian zeolite, Separation Science and Technology, 34, 2741-2760.

Hagiwara Z., Hoshino S., Ishino H., Nohara S., Tagawa K., Yamanaka K., (1990), Zeolite particles retaining silver ions having antibacterial properties, United States Patent, No. 4, 911,898.

Inoue Y., Hoshino M., Takahashi H., Noguchi T., Murata T., Kanzaki Y., Hamashima H., Sasatsu M., (2002), Bactericidal activity of Ag-zeolite mediated by reactive oxygen species under aerated conditions, Journal of Inorganic Biochemistry, 92, 37-42

Orha C., Manea F., Burtica G., Barvinschi P., (2007) A study of silver modified zeolite envisaging its using as water disinfectant, submitted to Revue Roumaine de Chimie.

Rivera-Garza M., Olguin M.T., Garcia-Sosa I., Alcantare D., Rodriguez-Fuentes G., (2000), Silver supported on natural Mexican zeolite as an antibacterial material, Microporous and Mesoporous Materials, 39, 431-444.

Rodriguez-Fuentes G., Ruiz-Salvador A.R., Mir M., Picazo O, Quintana G., Delgado M., (1998), Thermal and cation influence on IR vibrations of modified natural clinoptilolite, Microporous and Mesoporous Materials, 20, 269-281.

Top A., Ulku S., (2004), Silver, zinc and copper exchange in a Na-clinoptilolite and resulting effect on antibacterial activity, Applied Clay Science, 27, 13-19.

Woinarski A. Z., Stevens G. W., Snape I., (2006), A natural zeolite permeable reactive barrier to treat heavy-metal contaminated waters in Antarctica: kinetic and fixed-bed studies, Process Safety and Environmental Protection, 84, 109-116.



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USING GPS TECHNOLOGY AND DISTRIBUTED MEASUREMENT SYSTEM FOR AIR QUALITY MAPING OF REZIDENTIAL AREA

Alexandru Trandabăţ1∗, Marius Branzila1, Codrin Donciu1, Marius Pîslaru2, Romeo Cristian Ciobanu1

1Technical University of Iasi, Faculty of Electrical Engineering, 51-53 Mangeron Blvd., 700050, Iasi, Romania

2Technical University of Iasi, Dept. of Management and Engineering of Production Systems, 53 Mangeron Blvd., 700050, Iasi, Romania

Abstract The project’s idea is really simple: using the LabView environment, we have realized a virtual instrument able to get from the GPS the information about latitude, longitude, altitude and from a prototype data acquisition board for environmental monitoring parameters the information about air pollution factors. The perfect solution regarding the costs, the covered area and the accuracy of the measured data is the use of a glider for flight, because of its characteristics: free flights (without engine – meaning no local air polluting source), mobility (it is able to cover in one flight hundreds of kilometers) and low cost maintenance. All the information obtained during the measurement flights are corroborate with the meteorological information obtained from the local automatic meteorological station This mapping system can be used to map the information about the air pollution factors dispersion in order to answer to the needs of residential and industrial areas expansion. Key words: Virtual Instrumentation, Distributed Measurements, GPS, Air Quality Assurance


1. Introduction

The atmospheric environment needs to be examined in consideration of the following three phenomena: global warming, ozone-layer depletion, air pollution.

Among these three, global warming is the most critical in terms of environmental conservation. Global warming is a result of greenhouse-gas emissions; therefore, to prevent it, greenhouse-gas emissions must be reduced. A major greenhouse gas is carbon dioxide (CO2). Therefore, reducing energy use, or saving energy, is the most effective way to help prevent global warming. There are some other gases that have a considerable influence on global warming. The first step to cutting the emissions of these gases as another environmental conservation measure is to monitor them in order to find a way to control those (Branzila et al., 2004).

The decisions related to the environment safety are often taken in the belief that they are

scientifically well founded, i.e. by placing an excessive faith in the reliability of the expert information on which they are based. But, during the last century, such a pursuit was denied by an alarming number of environmental injuries, causing a continuously growing societal concern.

Today – more than ever – the public demands credible and understandable information about the quality of the environment in which they live or work the trend of environmental indicators, the priority problems related to environment pollution and long term associated risks. Accordingly, the common uncertainty and/or ignorance in decision-making AIR QUALITY AND POLLUTION MAPPING SYSTEM 317 must be balanced by innovative and multidisciplinary methods in order to carry out an efficient exchange of information across the different sectors and aspects involved in environmental monitoring (Trandabat and Pislaru, 2005).


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One of the main concerns is represented by the atmospheric environment, very sensitive to a synergy of factors, as consequence of three phenomena: global warming, ozone-layer depletion and, above all, local air pollution. Among all, global warming is the most critical in terms of environmental conservation, a clear result of greenhouse-gas emissions excess, mainly carbon dioxide (CO2). Nevertheless, the first step towards environment quality conservation lies in monitoring efficiently the factors with potential risk at local dimension. The actual practice clearly demonstrated that the classical, local, static measurements are affected by uncertainties, even errors. These uncertainties are propagated through the models of complex systems and finally presented in some form to the decision-maker, with tragic consequences. Therefore, the need to revise the existing models by checking their compatibility with the precautionary principle of vertical and dynamic monitoring represents a must for the novel reliable measurement systems. Such an example is offered by the remote measurement system described below.

2. The system architecture

The main objective of this work is to realize a

complex device for environmental quality control and monitoring. The system consists of two main parts: the mobile and the field component (Fig. 1). In order to cover a large monitoring area, the mobile system is placed on the luggage compartment of a glider. In the free flight, the glider will cover a wide area, and caring the mobile part of the system assures a good measurement precision without polluting the monitoring site with the exhaust gases, as a motorized aircraft would.

The mobile part is compound from an acquisition block based on specialized sensors connected in a low cost prototype acquisition board, from a positioning system which is represented by a GPSmap 196, a laptop and a transmission module. The software platform for this project was developed in Labview programming environment (Trandabat and Branzila, 2005).

The communication between GPS and laptop is realized with RS232 interface, using the NMEA protocol. The recorded data from GPS on the database are the values corresponding to the longitude, latitude and altitude, and separately, for a further complex data analyze, the values for speed. At the same time, the database receives also the values for the monitored gases concentration through a parallel port from the acquisition prototype board where the sensors are connected. If the monitored value is discovered to be out of the normal values, the communication module is activated and a warning message with the position and the recorded value is sent using a normal GPRS mobile phone to the field base, from where the responsible authorities are informed.

On this stage of the project, the mobile system autonomy depends on the laptop accumulator power,

so it is limited to three hours of continuum monitoring (Schreiner et al., 2006).

Fig. 1. The system for on-line environmental monitoring using a prototype data acquisition board, GPS and GPRS

technology

On the ground station, the database is downloaded at the end of the flight in order to be analyzed. The data from the database are corroborated with the information picked up during the day from the automatic meteorological weather station. The aim of this analyzes is to realize an air quality map for the monitored site (Fig. 2).

For common communication procedure between the measurement point assisted by a laptop and the server, DataSoket communication and TCP/IP tools were preferred. The expert user from the ground has the possibility to visualize the real data and/or to analyze the environmental quality factors via a history diagram stored in the server database (Girao et al., 2003).

The bloc diagram of the server virtual instrument is presented in Fig. 2. All communication software is designed under LABVIEW graphical programming language as well, including three protocol types. Communication type PC-instruments is developed using GPIB protocol, PC-server using TCP/IP and Internet communication using data socket technology, as is presented in Fig. 1.

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Fig. 2. Example of 3D air quality map; with dark red - the major risk area

3. Detection circuit and data acquisition board

In our application, dedicated sensors for temperature and gas evaluation (sensing element - metal oxide semiconductor, mainly composed of SnO2) for air quality analysis were used. In principle, mainly the gas sensors should be of highest quality, because they should offer immediate pertinent information towards defining representative environmental indicators, allowing evaluation of trends and quantification of achieved results in connection with temporal (season, day/night, peak hours etc.) or geographical parameters (altitude, vicinity etc.), or to atmospheric conditions (humidity, wind etc.), or even to societal demands (residential or industrial areas). The sensing element is heated at a suitable operating temperature by a built-in heater, allowing a sensitive change in its electrical resistance. In pure air, the sensor resistance is high, but, when exposed to a variety of gases, the sensor resistance decreases selectively in accordance with the gas type and concentration. Based on this information, the expert system from ground server processes the data according to a statistical – pollution (contamination) process - control methodology, decrypting the gases type and concentration and mapping the potential risk for environment safety (Branzila et al., 2005).

On the basic detection circuit, the change in the sensor resistance is obtained as the change of the output voltage across the load resistor (RL) in series with the sensor resistance. The constant 5V output of the data acquisition board is available for the heater of the sensor (VH) and for the detecting circuit (VC). As already indicated, the LM12H458CIV chip was preferred to make a Data Acquisition Board for interfacing with the laptop by parallel port and realize a flexible and complex system to allow monitoring of environmental parameters via some detection circuits with gas sensors distributed around the glider. The data acquisition board is related to highly integrated DAS. Operating on just 5V, it combines a fully differential self-calibrating (correcting linearity and zero errors) 13-bit (12-bit + sign) analogue to digital converter (ADC) and sample-and-hold (S/H) with extensive analogue functions and digital functionality. Up to 32 consecutive conversions using two’s

complement format it is stored in an internal 32-word (16-bit wide) FIFO data buffer (figures 3 and 4). An internal 8- word RAM can store the conversion sequence for up to eight acquisitions through the LM12H458CIV’s eight-input multiplexer. The LM12H458CIV operates with 8-bit + sign resolution and in a supervisory “watchdog” mode that compares an input signal against two programmable limits.

Fig.3. Architecture of prototype data acquisition board, through parallel port of PC

Programmable acquisition times and

conversion rates are possible through the use of internal clock-driven timers. The reference voltage input can be externally generated for absolute or ratiometric operation or can be derived using the internal 2.5V bandgap reference. All registers, RAM, and FIFO are directly addressable through the high-speed microprocessor interface to either an 8-bit or 16-bit databus. The LM12H458CIV include a direct memory access (DMA) interface for high-speed conversion data transfer (Branzila et al., 2004). 4. Conclusions

The paper presents the architecture of a

versatile, flexible, cost efficient, high-speed instrument for either monitoring the air quality and/or mapping the air pollution. The concept is based on a remotely controlled acquisition part - placed in a glider - with distributed and virtually programmed gas sensors, and a local dedicated expert system. The system may be particularized as virtual laboratory for on-line environmental monitoring classes too, helping the formation of well trained specialists in the domain. The immediate potential application lies in mapping the air pollution in terms of: factors, dispersion, trend, evolution and causes identification, in order to answer to the needs of immediate action and/or residential and industrial areas sustainable expansion, very important problems met mainly by candidate countries to EC.

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References Branzila M., Temneanu M. ,Creţu M, Pereira M.D., Donciu

C., (2004), System for environmental monitoring using a data acquisition board by parallel port, IPI, L, 737-742.

Branzila M., Fosalau C., Donciu C., Cretu M., (2005), Virtual Library Included in LabVIEW Environment for a New DAS with Data Transfer by LPT, Proc. IMEKO TC4 , vol.1, Gdynia/Jurata Poland, 535-540.

Girao P., Postolache O., Pereira M., Ramos H., (2003), Distributed measurement systems and intelligent processing for water quality assessment, Sensors & Transducers Magazine, 38, 82-93.

Schreiner C., Branzila M., Trandabat Al., Ciobanu R., (2006), Air quality and pollution mapping system, using remote measurements and GPS technology, Global NEST Journal, 8, 315-323.

Trandabat A., Branzila M., Schreiner C., (2005), Distributed measurements system dedicated to environmental safely, Proc. 4th Int. Conf. on the Manag. of Tech. Changes, vol.2, Chania-Greece, 121-124.

Trandabat A., Pislaru M., Schreiner C., Ciobanu R., (2005), E-survey instruments based on remote measurements dedicated to peculiar areas with increased risk for environmental safety, 9th Int. Conf. on Environmental Science and Technology, Vol. B, Rhodes-Greece, 933-938.



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SYNTHESIS, CHARACTERIZATION AND CATALYTIC REDUCTION OF

NOx EMISSIONS OVER LaMnO3 PEROVSKITE

Liliana-Mihaela Chirilă1∗, Helmut Papp2, Wladimir Suprun2, Ion Balasanian1

“Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering, Department of Environmental Engineering

and Management, 71A D. Mangeron Bd., 700050 - Iasi, Romania 2Institute for Technical Chemistry, University of Leipzig, Linnéstr. 3, D-04103 Leipzig, Germany

Abstract The perovskite structure was synthesized by sol-gel method type citrate. Three perovskite LaMnO3 samples were obtained after calcination and were characterized by XRD, XPS and TPR. The catalytic testing was carried out in SCR-HC equipment (HC=C3H6 and C3H6 respectively) in presence and also in absence of oxygen atmosphere. The results pointed out a good activity in NOx reduction but only in oxygen absence. As it was expecting, LaMnO3 perovskite has shown a good activity for hydrocarbons oxidation Key words: citrate sol-gel, perovskites, SCR-HC


1. Introduction

Once the atmosphere pollution became a serious problem for environment, the scientific world in the field started to develop different methods for removing of emissions resulted from human activities. It is well known that a large amount of nitrogen oxides emissions are coming from lean burn engines.

Selective catalytic reduction (SCR) method of nitrogen oxides supposes the using of reduction agent which increases the requirements for mobile engines. Thus, for catalytic nitrogen oxides converting the attention was headed to the burn environment for a proper reduction agent. Many tests were used the hydrocarbons as reduction agent leading to good results of nitrogen oxides conversion (Buciuman et al., 2001; Haj et al., 2002; Rottländer et al., 1996; Tran et al., 2004).

Another problem in selective catalytic reduction is the catalyst choosing. A good catalyst must have a high stability, a high catalytic activity and to be cheap. A good catalytic potential for nitrogen oxides removing has shown different catalytic materials such noble metals, zeolites or oxides. The exotic character of some oxides with

perovskite structure is reflecting in their catalytic activity and makes them famous in oxidation catalytic processes. Different results were obtained in catalytic reduction over these structures (Ng Lee et al., 2001; Patcas et al., 2000; Spinicci et al., 2003).

The aim of this paper is synthesis and characterization of LaMnO3 perovskite and its testing as catalytic material in nitrogen oxides removing by SCR-HC method. Three LaMnO3 perovskite samples were obtained by calcinations at 600, 800 and 1000 oC and were characterized by XRD, XPS, gas physisorbtion and TPR. The catalytic testing of these samples was carried out in SCR-HC equipment where the hydrocarbons used like reduction agent were propene and propane.

2. Experimental 2.1. LaMnO3 synthesis

LaMnO3 perovskite structure was prepared by

citrate method type sol-gel using lanthanum and manganese nitrates 1:1 with an excess of citric acid 1.5. It was followed next steps of the perovskite synthesis: i) stirring of precursors in distilled water at 60 oC till obtaining a yellow viscous solution; ii)


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drying in oven at 80 oC and iii) calcination in muffle oven of the dried gel at three different temperatures: 600, 800 and 1000 oC (5 hours for each sample). 2.2. Characterization

The calcined solids were characterized by

different methods: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), gas physisorbtion (N2) and temperature programmed reduction (TPR).

The crystallographic data were obtained using a Siemens D5000 diffractometer with CuKα radiation for crystalline phase detection between 5 and 100 o

(2θ). XPS surface analysis were performed with a LHS 10 (Leybold AG) spectrometer using MgKα radiation (λ = 1256.6 eV). The specific surface area (BET) was determined by nitrogen adsorption at 300 oC using a Micrometics model ASAP 2000. TPR analysis was carried out under H2 atmosphere, in a temperature range between 30 and 900 oC. 2.3. Catalytic activity testing

The catalytic reduction of nitrogen oxides was carried out in a SCR-HC equipment with a gas mixture consisted by hydrocarbon (C3H6 – 600 ppm and C3H8 -800 ppm respectively), nitrogen oxides (600 ppm) under rich oxygen atmosphere (5%). 3. Results and discussions 3.1. The characterization of LaMnO3 perovskite

samples: XRD, XPS, gas physisorption and TPR

In order to assess the perovskite-like structure, XRD analysis was recorder. The diffractograms obtained for LaMnO3 perovskite samples are shown in Fig.1. The strong line of each XRD pattern showed the presence of single perovskite phase. In accordance with JCPDS-1998 data, all synthesized samples correspond to perovskite structure as is presented in Table 1.

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0

1 0 0 0 °C

8 0 0 °C

6 0 0 °C

2 T h e ta

Fig.1. X-Ray diffractograms of LaMnO3 perovskites

calcined at 600, 800 and 1000 oC, respectively It was found a full perovskite structure like

LaMnO3 for the synthesized sample at 600 oC while the synthesized sample at 800 oC has shown a

lanthanum deficit of perovskite structure. An oxygen excess in the perovskite structure has shown the last sample, synthesized at 1000 oC.

Table 1. The samples correspondence with perovkite

structure Samples Perovskite

structure JCPDS-1998 Symmetry

600oC LaMnO3 86-1234, 75-440 Cubic 800oC La0.92MnO3 82-1152 Rhombohedra 1000oC LaMnO3+δ 32-848 Hexagonal

These deviations from the perfect stoichimetry result from calcinations process when the perovskite phase is under transformation. Alongside with the temperature increasing, the crystallographic structure is changing due to octahedral distortion.

For all perovskite synthesized samples, the La 3d5/2 signal it was found around 833,6 eV. The Mn 2p3/2 binding energy is 640 eV for LaMnO3 structure and 641 eV for the others that showing the presence of Mn(III) in perovskite structure of the samples synthesized at 800 and 1000 oC. O 1s signal was appeared in three peaks typically corresponding to binding oxygen, the oxygen from hydroxyl or carbonate and oxygen from humidity.

The values of surface atom composition are presented in Table 2 and showed enrichment in lanthanum of the perovskite surface for all analyzed samples.

Table 2. Surface atom composition, BET surface area and

reduction degree

Atom % Mn La O 1s T cal.

°C I II II

BET (m2/g)

600 15,4 20,4 41 18,6 4,6 24,7 800 15,1 20,2 39 18,7 7 13,1 1000 15 21 39 19,4 6 2,4

BET surface area (m2/g) has values which decrease parallel with increasing of calcination temperatures at which the samples were obtained. Thus, sample obtained at 600 oC have higher value while the less value is given by surface of the sample calcined at 1000 oC, Table 2.

TPR shape is given by reduction behavior of manganese oxides in analyzed perovskite in the presence of reducing gas, behavior very important which is reflected in catalytic activity of whole structure.

In order to characterize resulted MnOx phases during synthesis of perovskite, it has to take into account that Mn4+ reduces at lower temperature (331-351oC) than Mn3+ (443-526oC) (Buciuman et. al., 2000; Stephan et. al., 2002). TPR curves of three LaMnO3 perovskite samples presented in Fig. 2 are characterized by two reduction regions.

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0 200 400 600 800 1000

(c)

(b)

(a)

Temperature (°C)

Fig. 2. TPR curves for three LaMnO3 perovskite samples

calcined at 600, 800 and 1000 oC, respectively

The first region corresponds to manganese oxides reduction, already discussed, reduction that gradually takes place as the corresponding temperature peaks show. The first peak corresponds to Mn4+ la Mn3+ reduction when reduction performs between 78 331-351oC, followed by Mn3+ la Mn2+ reduction ate temperatures comprised between 421-471oC. The high consuming oh hydrogen happens in the second region of reduction curves due to both, Mn3+ reduction to Mn2+ in LaMnO3 perovskite and carbonate species such as La2O2CO3 those reduction corresponds to this temperature interval. Considering that these perovskites were prepared by citric method it is very plausible that carbonates traces are in their structure (Hackenberger, 1998; Stephan et. al., 2002). 3.2. Catalitic activity testing SCR-C3H6

The perovskite samples were tested in nitrogen oxides removing by SCR-C3H6 in presence and also in absence of oxygen atmosphere. In oxygen atmosphere (5%), the experimental results indicated of 100% propene oxidation activity between 300 and 450oC for the samples obtained at 600 and 1000 oC while for sample obtained at 800 oC, the maxim activity was around 78% after which the oxidation activity had kept just below this value.

The maxim point of propene conversion corresponded to the temperature interval in which propene could decompose to carbon dioxide and water. The perovskite synthesized sample at 1000oC achieved maximal activity at 300oC then it sharply deactivated. Regarding nitrogen oxides reduction as it can be seen in the experimental data processing (Fig. 3) all three LaMnO3 perovskite samples practically showed negligible conversion values.

The tests performed on synthetic gas mixture without oxygen have shown high activity for propene oxidation process but these were moved on high temperature range, over 400oC.

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Fig. 3. Nitrogen oxides (a) and propene (b) conversin for the LaMnO3 perovskite samples (propene 600 ppm, NOx

600 ppm, 5% O2)

For LaMnO3 perovskite sample obtained at 600oC the catalytic activity test was carried out on a large temperatures range between 150 and 600oC. Therefore, it can be observed for this sample that oxidation activity becomes maxim over 500oC and it remains constant until 600 oC, experimental limit temperature. The other two perovskites samples, synthesized at 800 and 1000 oC, the values of nitrogen oxides conversion was increasing until ending of experiment, 450 oC. At this temperature, LaMnO3 sample calcined at 800oC presents the higher value (100%) while sample calcined at 1000oC has the lower catalytic activity (65.24%) (Fig. 4). 3.3. Catalytic activity testing SCR-C3H8

Data processing obtained in selective catalytic reduction of nitrogen oxides using propane as reduction agent with 5% oxygen in synthetic gas mixture has led to the curves grouped in Fig.5. In this case, oxidation reaction reaches maximal values at high temperatures interval (350-450oC). As it is shown in Fig. 5 diagram b, the LaMnO3 perovskite samples achieve maximal hydrocarbon conversion point at 450oC.

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Fig. 4. Nitrogen oxides (a) and propene (b) conversion for the LaMnO3 perovskite samples (propene 600 ppm, NOx

600 ppm)

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Fig. 5. Nitrogen oxides (a) and propane (b) conversion for the LaMnO3 perovskite samples (propane 400 ppm, NOx

600 ppm, 5% O2)

Oxygen lack in synthetic gas mixture leaded to important changes of conversion curves for both propane oxidation and nitrogen oxides reduction. Fig.6 displays, reduction reaction was favored, while oxidation reaction has kept constant values in whole temperature range in which tests were performed. The higher values for oxidation reaction belong to perovskite sample calcined at 600oC which proves to be again the most efficient perovskite in propane oxidation while LaMnO3 sample calcined at 800°C presented lower values, almost negligible.

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Fig. 6. Nitrogen oxides (a) and propane (b) conversion for the LaMnO3 perovskite samples (propane 400 ppm, NOx

600 ppm) 4. Conclusions

The characterization by presented physico-chemical methods confirmed that the synthesized samples are perovskite structures with a high homogeneity and crystallinity. The calcination process has leaded to three different symmetry of LaMnO3 perovskite due to octahedral distortion.

It is well known that perovskites present a certain small surface comparing with other catalysts. The BET specific surface of LaMnO3 perovskite was found 24m2/g corresponding to the sample obtained at 600 oC and decreases once with the calcinations temperature rising up to 2.5m2/g in the case of calcinations sample at 800 oC. The oxidation state of the manganese from the LaMnO3 perovskite leaded to

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a reducing character just like the reduction analysis at programmed temperature showed.

The catalytic activity tests made on the three LaMnO3 perovskite samples using propena and propan as reduction agent, showed a good oxidation catalytic activity in a rich oxygen medium. For lack of oxygen from the synthetic mixture of gas using propane, the LaMnO3 perovskite presents activity both in nitrogen oxides reduction and the propane oxidation. In the case of propane the oxidation activity takes place only in the presence of oxygen, while the reduction activity needs a poor oxygen medium and over 400 oC temperatures. For the temperature interval of 150o-450oC used in catalytic activity tests the “full” structure type LaMnO3 had the best activity. A good activity was obtained also in the case of the other two types of structures: La0.98MnO3 and LaMnO3.15. Using propene as a reduction agent leads to better results than using propane. The synthesized sample at 800oC revealed the lowest activity in nitrogen oxides reduction with propene in lack of oxygen References Hackenberger M., (1998), Untersuchungen an Perowskit –

Katalysatoren und Perowskit-Traegerkatalyzatoren fuer die Totaloxidation von Schadstoffen, Dissertation, Universität Leipzig, Germany.

Alifanti M., Kirchnerova J., Delmon B., (2003), Effect of substitution by cerium on the activity of LaMnO3 perovskite in methane combustion, Appl. Cat. A: Gen., 245, 231-244.

Buciuman F. C., Patcas F., Zsakó J., (2000), TPR-study of Substitution Effects on Reducibility and Oxidative Non-stoichiometry of La0.8A'0.2MnO3+δ Perovskites, Journal of Thermal Analysis and Calorimetry, 61, 819-825.

Buciuman F. C., Joubert E., Menezo J. C., Barbier J., (2001), Catalytic properties of La0.8A0.2MnO3 (A = Sr, Ba, K, Cs) and LaMn0.8B0.2O3 (B = Ni, Zn, Cu) perovskites: 2. Reduction of nitrogen oxides in the presence of oxygen, Appl. Cat. B: Env., 35, 149-156.

Kakihana M., Arima M., Yoshimura M., Ikeda N., Sugitani Y., (1999), Synthesis of high surface area LaMnO3+d by a polymerizable complex method, J. Alloys. Compd. 283, 102-105;

Haj K. O., Ziyade S., Ziyad M., Garin F., (2002), DeNOx reaction studies: Reactivity of carbonyl or nitro-compounds compared to C3H6: influence of adsorbed species in N2 and N2O formation, Appl. Catal. B: Env., 37, 49-62.

Liu Y., Zheng H., Liu J., Zhang T., (2002), Preparation of high surface area La1−xAxMnO3 (A=Ba, Sr or Ca) ultra-fine particles used for CH4 oxidation, Chem. Eng. J., 89, 213-221.

Ng Lee Y., Lago R. M., Fierro J. L. G., Cortés V., Sapiña F., Martínez E., (2001), Surface properties and catalytic performance for ethane combustion of La1−xKxMnO3+δ perovskites, Appl. Cat. A: Gen., 207, 17-24.

Patcas F., Buciuman F. C., Zsako J., (2000), Oxygen non-stoichiometry and reducibility of B-site substituted lanthanum manganites, Termochim. Acta, 360, 71-76.

Rottländer C., Andorf R., Plog C., Krutzsch B., Baerns M., (1996), Selective NO reduction by propane and propene over a Pt/ZSM-5 catalyst: a transient study of the reaction mechanism, Appl. Cat. B: Env., 11, 49-63.

Spinicci R., Faticanti M., Marini P., De Rossi S., Porta P., (2003), Catalytic activity of LaMnO3 and LaCoO3 perovskites towards VOCs combustion, J. Mol. Cat. A: Chem., 197, 147-155.

Spinicci R., Delmastro A., Ronchetti S., Tofanari A., (2002), Mater. Chem. Phys., 78, 393-399;

Stephan K., Hackenberger M., Kießling D., Wendt G., (2004), Total oxidation of methane and chlorinated hydrocarbons on zirconia supported A1-xSrxMnO3 catalysts, Chem. Eng. Technology, 27, 687-693.

Teraoka Y., Harada T., Kagawa S., (1998), Reaction mechanism of direct decomposition of nitric oxide over Co- and Mn-based perovskite-type oxides, J. Chem. Soc., Faraday Trans., 94, 1887-1891.

Tran D. N., Aardahl C. L., Rappe K. G., Park P. W., Boyer C. L., (2004), Reduction of NOx by plasma-facilitated catalysis over In-doped γ-alumina, Appl. Cat. B: Env., 48, 155-164.



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KINETICS OF CARBON DIOXIDE ABSORPTION INTO AQUEOUS

SOLUTIONS OF 1, 5, 8, 12- TETRAAZADODECANE (APEDA)

Ilie Siminiceanu1∗, Ramona-Elena Tataru-Farmus1, Chakib Bouallou2

1Technical University “Gh. Asachi” of Iaşi, Faculty of Chemical Engineering, 71 Bd. Mangeron, RO- 700050 Iaşi, Romania

2Ecole Nationale Supérieure des Mines de Paris, Centre d’Energétique (CENERG), 60 Bd. Saint Michel, 75006 Paris, France

Abstract The absorption of CO2 into an aqueous solution with 1.45 mol/L 1,5,8,12-tetraazadodecane (APEDA) polyamine has been studied at three temperature (298, 313, 333 K) in a Lewis type absorber with a constant gas-liquid interface area of (15.34 ± 0.05) x 10-4 m2. The experimental results have been interpreted using the equations derived from the two film model with the assumption that the absorption occurred in the fast pseudo- first- order kinetic regime. The results confirmed the validity of this assumption for the experimental conditions: the enhancement factor was always greater than 3. The rate constant derived from the experimental data (kov, s-1) was correlated through the Arrhenius plot ( ln kov = A- B/T), and the optimal values of the constants A and B were obtained by the linear regression. The absorption of CO2 from flue gas into APEDA solution is a promising process for practical application at least from the kinetic point of view. The rate constant derived from experiments is of the same order of magnitude as that for the absorption into 2- amino- 2- methyl- 1- propanol (AMP) activated with piperazine (PZ) which was found to be the most advanced system among the published data up to now. Key words: acid gas absorption, Lewis cell absorber, enhancement factor, rate constant


1. Introduction

The removal of carbon dioxide from gas streams by selective absorption into aqueous solutions is an important industrial process in both natural gas sweetening and ammonia synthesis gas production. Aqueous hot potassium carbonate promoted by diethanolamine (DEA) is the chemical solvent used in the ammonia plants of Romania. Today, there are seven such ammonia plants in Romania (each of 1000 t NH3/ day) where the absorption is operated at 30- 40 bar, 343 K, solution with 25- 30 % K2CO3 and 1-2 % DEA, in packed columns. The carbon dioxide, recovered by the reverse reaction (1) in the stripping column, is then consumed in the reaction (2) with ammonia, to produce urea- the best nitrogen fertilizer (Siminiceanu, 2004).

CO2 + K2CO3 + H2O = 2 KHCO3 (1)

CO2 + 2 NH3 = CO (NH2)2 + H2O (2)

The question is: could be this process

applied with the same high performances as in ammonia production to the capture of carbon dioxide from combustion flue gas of the fossil fuel power plants? Unfortunately, the answer is no. This is because the flow rates, composition, temperature and pressure of flue gas are different. The CO2 partial pressure in the flue gas is much lower then in ammonia synthesis gas. It is of maximum 15 kPa. Therefore, more reactive absorbents are needed, like monoethanolamine (MEA) aqueous solution. The absorption of CO2 into MEA solution is also a well established process (Kohl and Nielsen, 1997). It has been already applied in the only three industrial plants in the world for CO2 capture from fossil fuel power plant flue gas (Abu- Zahra et al., 2007a; 2007b). They have the commercial names Econamine FG, Econamine FG Plus, and ABB Lumnus, respectively. The simplified flow diagram of such a process is presented in Fig.1.After the removal of NOx and SOx


Siminiceanu et al. /Environmental Engineering and Management Journal 6 (2007), 6, 555-561

556

the flue gases are cooled at 40oC and transported with a gas blower to overcome the pressure drop caused by the MEA absorber. The MEA solution (30- 40 % MEA) is regenerated in the stripper at elevated temperatures (100- 120oC) and a pressure not much higher than atmospheric. Heat is supplied to the boiler using low- pressure steam which also acts as a stripping gas. Besides the high absorption rate, the MEA process has a number of drawbacks that are detailed bellow.

Fig. 1. Flow sheet of the CO2 removal from flue gas by the MEA process

(1) The first important drawback is the large

absorption/stripping enthalpy: 83 kJ/mol CO2 at 298 K, in a solution 5M of MEA (Hilliard, 2005). This is equivalent to 4.0 GJ/t of CO2 captured. The actual energy requirement in the Econamine FG process is of 4.2 GJ/t (Abu-Zahra et al., 2007a). The enthalpy of absorption of CO2 into MEA solution is higher than in both K2CO3 solution (63 kJ/ mol) and in other amine solutions (DEA, AMP, MIPA, PZ, MDEA). Therefore, the energy consumption of MEA capture system could be up to 40% of the power plant output (Hilliard, 2005) and a proportional more expensive electrical energy which must be peyed by consumers. Nevertheless, recently has been found (Dallos et al., 2001) that the absorption enthalpy of CO2 into a polyamine (TMBPA) is of only 44 kJ/mol. This suggested to the authors of this paper to study the absorption of CO2 into a similar polyamine:1,5,8,12- tetraazadodecane (APEDA).

(2) The second major drawback of MEA is the law cyclic absorption capacity. The theoretical value is of 0.5 mol CO2/ mol amine, according to the overall reaction (3), based on the carbamate formation through the zwitterions mechanism:

CO2 + 2 HOCH2CH2NH2= HOCH2CH2NCOO- +

HOCH2CH2NH+

2 (3)

The practical value is of only 0.35 (from 0.2 of the lean solution to 0.45 of the carbonated solution).Therefore, the MEA process needs about 55 m3 solution /ton CO2 captured. The polyamine named TMBPA has a saturation loading of 3 mol CO2/ mol

amine (Dallos et al., 2001). A higher cyclic capacity reduces the flow rate of the solution needed. APEDA is expected to have a cyclic absorption capacity of 2 because it includes two primary and two secondary amine groups in the molecule (Table 1).

(3). The third important disadvantage of MEA is its degradability. The reactions of MEA with NOx, SOx, CO and O2 which accompany the CO2 in flue gases leads to heat- stable salts which must be purged from the recalculated solution (Bello and Idem, 2005). These salts mainly consist of formate (87%), acetate (4.6%), oxalate (0.2%), thiocyanate (6.8%), thiosulphate (1.2%) and sulphate (0.2%). The production of these salts could be from 3.729 to 14.917 kg/ t CO2 captured (Thitakamol et al., 2007). This means that up to 10% of active amine is lost through degradation. It must be noted that the degradation oxidative reactions of MEA begin by the attack at the alcohol function of the alkanol radical (Strazisar et al., 2003). The replacement of MEA with an alkyl amine could avoid or mitigate the degradation reactions.

(4). The presence of heat- stable salts in the absorption solution causes a number of adverse effects: reduction of amine absorption capacity, increase in foaming tendency of the solution, increase in solution viscosity, increase in corrosion, reduced filter runtime due to the solid precipitation in solution. Consequently, the solution must contain at least three types of additives: oxygen scavengers (OS), corrosion inhibitors (CI), and antifoam agents AA). The addition of OS is claimed to reduce the formation of heat- stable salts. Potential OS are: quinine, oxime, hydroxylamine and their mixtures. Corrosion inhibitors developed and patented include organic inhibitors (thiourea, salicylic acid) and inorganic inhibitors (V, Cr, Cu, Sb, S compounds).The inorganic CI has superior inhibition performance (Tanthapanichakoon, 2006). Sodium metavanadate (NaVO3) is the most extensively used in amine treating plants for ammonia synthesis gas manufacture (Siminiceanu, 2004). Antifoam agents must also be used to reduce foam formation, which may occur due to the presence of fine solid particles and heat-stable salts. Common antifoam agents are high-boiling alcohols (Kohl and Nielsen, 1997) such as oleyl alcohol and octylphenoxyethanol, or silicone- based compounds such as amino silicon and dimetylsilicon. These special additives make the MEA solution an expensive one. The estimated cost of CO2 capture by absorption in MEA solution was evaluated at EUR 39.3/ tone of CO2 avoided (Abu- Zahra et al., 2007b). This could increase the cost of electricity production by 82.8 % (from EUR 31.4/MWh to EUR 57.4/ MWh). APEDA is not an alakanolamine and could be not degraded by oxidation with SOx, CO and O2. In addition, APEDA is frequently used as ingredient for corrosion inhibitors (http://www.chemicalland21.com/arokorhi/ specialtychem/finechem/)

The objective of this work was to study the kinetics of CO2 absorption into APEDA aqueous

Kinetics of carbon dioxide absorption into aqueous solutions of 1, 5, 8, 12- tetraazadodecane (APEDA)

557

solution. The originality of the present work consists of two aspects: the solvent, and the apparatus. The solvent was a 1.45 M APEDA aqueous solution, a polyamine which has not yet been used for the CO2 absorption. The apparatus is described in the next section. 2. Experimental

2.1. Experimental apparatus

The apparatus (Fig. 2) is a Lewis type absorber with a constant gas-liquid interface area of (15.34 ± 0.05) x 10 -4 m 2. The total volume available for gas and liquid phases is (0.3504±0.0005) 10-4 m3. The temperature is kept constant within 0.05 K by circulating a thermostatic fluid through the double glass jacket. The liquid phase is agitated by a six bladed Rushton turbine (4.25x 10-2 m diameter). The gas phase is agitated by 4x10-2 m diameter propeller. Both agitators are driven magnetically by a variable speed motor. The turbine speed is checked with a stroboscope.

The kinetics of gas absorption is measured by recording the absolute pressure drop through a SEDEME pressure transducer, working in the range (0 to 200) x103 Pa. A microcomputer equipped with a data acquisition card is used to convert the pressure transducer signal directly into pressure P units, using calibration constant previously determined, and records it as function of time.

Fig.2. Flow diagram of the absorption equipment

2.2. Experimental procedure

Water and APEDA are degassed

independently and aqueous solutions are prepared under a vacuum.

The amounts of water and amines are determined by differential weightings to within ±10-2 g. This uncertainty on weightings leads to uncertainties in concentrations of less then ± 0.05%.

The flask containing the degassed APEDA aqueous solution is connected to the absorption cell by means of a needle introduced through the septum situated at the bottom of the cell. Weighing the flask with the tube and the needle before and after transfer allows the determination of the exact mass of solvent transferred into the cell.

Once the amine aqueous solution is loaded and the temperature equilibrated, the inert gas pressure Pi corresponding mainly to the solvent vapor pressure plus eventual residual inert gases is measured. The pure CO2 is introduced over a very short time (about 2 s) in the upper part of the cell, the resulting pressure P0 is between (100-200) x103 Pa. Then stirring is started and the pressure drop resulting from absorption is recorded.

2.3. Materials

The main materials involved have been: water,

carbon dioxide, 1,5,8,12-tetraazadodecane (APEDA). Ordinary twice-distilled water was used. Carbon dioxide, purchased from Air Liquid, of 99.995% purity, was used as received. APEDA from Alfa Aesar (Store Road, Heysham) material certified 96.5 % was used as received. Table 1 lists the main properties of the amine used.

Solution densities were measured with an Anton Paar (Graz, Austria) vibrating tube densimeter, model DMA 512.

Table 1. The main properties of the APEDA

(http://www.chemicalland21.com/arokorhi/specialtychem/finechem)

Property Value

Physical state Pale yellow liquid CAS N0. 10563-26-5 Structural formula

2 2 2 2 2

2 2 2 2 2

CH NH CH CH CH NH

CH NH CH CH CH NHI

− − − − −

− − − − −

Name 1,5,8,12- Tetraazadodecane Synonyms N-[2—(3- Aminopropylamino)ethyl]-1, 3-

Propanediamine; N, N’-Bis(3 – aminopropyl) diaminoethane; N, N’- Bis(3- aminopropyl)ethylenediamine;

N, N’- Diaminopropylethylenediamine; N, N’- 1, 2- ethanediylbis- 1, 3-

Propanediamnine Molecular weight, kg/kmol

174.29

Chemical formula C8H22N4

Boiling point, o C 170 Melting point, o C - 1.5 Density, at 293 K, kg/m3

952

Flash point, o C 142 Stability Stable under ordinary conditions Solubility in water

Miscible

Refractive index, at 293 K

1.4910


558

3. Results and discussion

The primary experimental results have been interpreted on the basis of the gas- liquid chemical process theory (Siminiceanu, 2004). The rate of the chemical absorption of CO2 ( = i)is of the form (4):

- dni/ A dt = E ko

L Cei , mol/ m2 s, (4)

The gas phase is assumed ideal (Pi Vg = ni

RT), CO2 is completely consumed by the reaction in the liquid film, and the CO2 concentration at the interface is replaced by the Henry law ( Ce

i = Pie / Hi ).

The partial pressure of CO2 is obtained by subtraction of vapor pressure of the solution ( Pv) from the total measured pressure (PT) : Pi = PT – Pv. By integrating (4) under these assumptions, the equation (5) is derived:

ln (PT- Pv) t / (PT – Pv)to = - β (t- to) (5) where: β= E kL

0 ART/ Vg Hi (6)

The enhancement factor E can be calculated for each experiment, using the Eq. (6).

In order to compare our results with those for other solutions at the same temperature, the overall rate constant (kov) of the pseudo- first order reaction has been calculated for the fast reaction regime (E = Ha > 3):

kov = (kL

0 E )2 / Di (7)

The mass transfer coefficient kL0 is calculated

with the Eq. (8) which was established, using the N2O analogy, for the absorber also applied in these new kinetic experiments (Amararrene and Bouallou, 2004):

Sh = 0.352 Re 0.618 Sc0.434 (8)

Where the dimensionless Sherwood (Sh),

Reynolds (Re) and Schmidt (Sc) numbers have been defined as follows:

Sh= kL

0 Dc/ Di

Re= ρL N dst/ µL Sc= µL/ ρL Di

E being calculated with Eq. (6), using the experimental values of β from the Tables 2, 3, and 4.

The Henry constant (Hoi) and the diffusion

coefficient (Doi) for the system CO2- H2O have been

calculated with the Eqs (9) and (10), respectively (Versteeg and van Swaaij, 1988):

H0

i = 2.8249x106 exp (-2044/T) (9)

Doi = 2.35x10-6 exp (-2119/T) (10)

The presence of the amine in water decreases

the gas solubility (“salting out effect”). Taking into account the influence of the ionic strength of the solution on the solubility (Siminiceanu, 2004) with an equation of Sechenow type, the Hi for the solution of 1.45 M APEDA was evaluated with (11):

Hi= 1.113 xH0

i (11)

The diffusivity of CO2 in the APEDA aqueous solution was evaluated with Eq. (12), tested in a previous work (Siminiceanu et al., 2006):

Di = (Do

i/ 2.43) ( µL/ µW)0.2 (12)

The ratio µL/µW has been correlated for the APEDA solutions on the basis of experimental data published in a previous paper (Tataru-Farmus et al., 2007).

The results from the Table 3 (first row, for the same loading) can be compared to those obtained for the absorption of CO2 in a solution of AMP (1.5 M) with different doses of PZ as activator, in a wetted wall column absorber at the same temperature and a loading a= 0.288- 0.031 (Sun et al., 2005).

The value obtained in this work with APEDA (kov=17255.51 s-1) is higher than kov for AMP with 0.1 and 0.2 M piperazine, and inferior to that for larger doses of PZ. It must be noted that he solution AMP- PZ- H2O gives the grates absorption rate among the new systems studied in the literature in the last decades.

8.00

8.50

9.00

9.50

10.00

10.50

11.00

11.50

12.00

3.00 3.10 3.20 3.30 3.40

1000/T, K-1

ln k

ov

a=0.05-0.10

Fig. 3. The Arrhenius plot at low loading (a= 0.05- 0.10 mol CO2/ mol APEDA)


559

Table 2. Experimental and calculated data for the absorption of CO2 in APEDA (1.45 M) aqueous solution at 298 K.

a, molCO2/mol

APEDA β Hi,

Pa.m3/mol 2COD , m²/s 0lk , m/s E=Ha kov , s-1

0.012 0.028 2965.85 2.00E-09 1.96E-05 206.04 8 490.91 0.070 0.026 2965.85 2.00E-09 1.96E-05 191.32 7 030.98 0.180 0.025 2965.85 2.00E-09 1.96E-05 183.96 6 500.34 0.295 0.023 2965.85 2.00E-09 1.96E-05 169.24 5 501.79 0.382 0.022 2965.85 2.00E-09 1.96E-05 161.88 5 033.48 0.484 0.021 2965.85 2.00E-09 1.96E-05 154.52 4 586.39

Table 3. Experimental and calculated data for the absorption of CO2 in APEDA (1.45 M) aqueous solution at 313 K

a,

molCO2/mol APEDA

β Hi, Pa.m3/mol 2COD , m²/s 0

lk , m/s E=Ha kov , s-1

0.031 0.040 4110.08 2.10E-09 2.16E-05 278.69 17 255.51 0.087 0.036 4110.08 2.10E-09 2.16E-05 250.82 13 125.00 0.208 0.035 4110.08 2.10E-09 2.16E-05 243.85 12 487.19 0.305 0.034 4110.08 2.10E-09 2.16E-05 236.88 11 783.55 0.409 0.030 4110.08 2.10E-09 2.16E-05 209.01 9 173.88 0.508 0.027 4110.08 2.10E-09 2.16E-05 188.11 7 862.10

Table 4. Experimental and calculated data for the absorption of CO2 in APEDA (1.45 M) aqueous solution at 333 K

a,

molCO2/mol APEDA

Hi, Pa.m3/mol 2COD , m²/s 0

lk , m/s E=Ha kov , s-1

0.047 0.041 6098.76 2.23E-09 2.49E-05 445.95 55 292.49 0.109 0.041 6098.76 2.23E-09 2.49E-05 445.95 55 292.49 0.222 0.040 6098.76 2.23E-09 2.49E-05 435.07 52 627.42 0.330 0.033 6098.76 2.23E-09 2.49E-05 358.93 35 818.99 0.430 0.029 6098.76 2.23E-09 2.49E-05 315.43 27 663.03 0.518 0.026 6098.76 2.23E-09 2.49E-05 282.79 22 235.57

Table 5.The results for the absorption of CO2 in 1.5 M solutions of AMP activated with PZ at 313 K (Sun et al., 2005)

Co

PZ, mol/L ax 102, mol/mol

koLx 105, m/s

Di x109, m2/s

Hi, Pa m3/mol

NAx 106, kmol/m2s

kov, s-1

0.1 3.11 3.97 1.72 4 144 3.46 7 530 0.2 2.88 4.05 1.66 4 047 3.88 13 857 0.3 3.10 3.68 1.57 4 095 4.31 20 572 0.4 3.16 3.64 1.42 4 070 4.52 27 819

8.00

8.50

9.00

9.50

10.00

10.50

11.00

11.50

12.00

3.00 3.10 3.20 3.30 3.40

1000/T, K-1

ln k

ov

a=0.40-0.50

Fig. 4. The Arrhenius plot at high loading (a= 0.40- 0.50 mol CO2/ mol APEDA)

8.50

9.00

9.50

10.00

10.50

11.00

11.50

3.00 3.10 3.20 3.30

1000/T, K-1

ln k

ov

a=0.00-0.05a=0.05-0.10a=0.10-0.20a=0.20-0.30a=0.30-0.40a=0.40-0.50

Fig. 5. The Arrhenius plots for all experimental loadings


560

Table 6. The kinetic parameters derived from the Arrhenius plot

Ea a

molCO2/mol APEDA cal/mol kJ/mol

A= 0ln ovk

B=Ea/R, K

0.00-0.05 10 553.89 44.11 26.496 5 311.02 0.05-0.10 10 616.18 44.37 26.877 5 342.72 0.10-0.20 10 782.52 45.06 27.272 5 426.27 0.20-0.30 10.552.85 44.11 25.931 5 310.52 0.30-0.40 9 599.42 40.12 24.238 4 830.90 0.40-0.50 8 890.80 37.16 24.671 4 474.08 4. Conclusions

The aqueous monoethanolamine (MEA) is now considered the most convenient among the available absorption technologies for removing carbon dioxide from flue gas streams. Nevertheless, this process has a number of drawbacks, pointed out in the introductory section of this paper, which make it rather expensive. Its application to fossil fuel power plants could increase the cost of electricity production by up to 82.8 % (Abu- Zahra et al., 2007b). This paper presents some results of a study aiming to develop a new solvent in order to improve the efficiency of the CO2 removal from flue gas.

The absorption of CO2 into an aqueous solution with 1.45 mol/L 1,5,8,12- tetraazadodecane (APEDA) polyamine has been studied at three temperature (298, 313, 333 K) in a Lewis type absorber with a constant gas- liquid interface area of (15.34 ± 0.05) x 10 -4 m 2. The experimental results have been interpreted using the equations derived from the two film model with the assumption that the absorption occurred in the fast pseudo- first- order kinetic regime. The results confirmed the validity of this assumption for the experimental conditions: the enhancement factor was always greater than 3.

According to the results, the rate constat (kov) increased with the temperature, and decreased with the carbonation degree/ loading (a= mol CO2/mol amine). For each loading the Arrhenius equation was satisfactory verified. The activation energy (41.9 kJ/mol) indicated that the process proceeded close to the boundary between the kinetic and the mass transfer regime. The optimal values of the constants A and B from the Arrhenius equation (lnk = A- B/T) were derived by linear regression, for each loading. These will be useful for the industrial absorption column modeling and simulation.

The rate constant derived from experiments is of the same order of magnitude as that for the absorption into 2- amino- 2- methyl- 1- propanol (AMP) activated with piperazine (PZ) which was found to be the most advanced system among the published data up to now( Sun et al., 2005). At T= 313 K and a< 0.05, for instance, kov = 17 255 s-1 for APEDA, compared to 20 572 s-1 for 1.5M of AMP with 0.3M of PZ under the same conditions.

The preliminary results presented in this paper show that, from the kinetic point of view, the absorption of CO2 from flue gas into APEDA solution is a promising process for practical application .Other potential advantages of APEDA compared to MEA : higher loadings( smaller solution flow rates), less energy required for regeneration, lower degradability and corrosiveness. It is still to prove the unavoidable existence of some drawbacks, such as, volatility, toxicity and cost.

Notation A, area of the gas- liquid interface, m2; a, moles of gas absorbed per mole of amine (loading), mol/mol; Ci, molar concentration, kmol/m3; Do

i , diffusion coefficient of i in water, m2/s; Di, diffusion coefficient of i in solution, m2/s; Dc, absorption cell internal diameter, m; dst, stirrer diameter, m; E, enhancement factor of absorption by the chemical reaction; Hi, Henry constant for the absorption of CO2 in the APEDA solution, Pa. m3/ mol; Hi

o, Henry constant for the absorption of CO2 in water, Pa. m3/ mol; Ha, Hatta number; kL

0, liquid side mass transfer (without chemical reaction) coefficient, m/s; kL= E kL

0, liquid side mass transfer with chemical reaction

coefficient, m/s; kov, pseudo- first order reaction rate constant, s-1 ; N, rotation rate, s-1; ni , number of moles of i; P, total pressure, Pa; Pi, partial pressure of the gas i, Pa; Pv, vapor pressure of the solution, bar; R, gas constant (8.314 Pa m3/ mol); Re, Reynolds number; Sc, Schmidt number; Sh, Sherwood number; T, temperature, K; t, time, s; Vg, gas phase volume, m3; β, the slope in the equation (3), s-1; ρL, liquid density, kg/ m3; µL, liquid viscosity, Pa s; µ, viscosity of water, Pa s. References Abu-Zahra M.R.M., Schneiders L.H.J., Niederer J.P.M.,

Feron P.H.M., Geert F., (2007), CO2 capture from power plants. Part I. A parametric study of the technical performance based on monoethanolamine, International Journal of Greenhouse Gas Control, 1, 37- 46.

Abu-Zahra M.R.M., Niederer J.P.M., Feron P.H.M., Versteeg G.F., (2007), CO2 capture from power plants. Part II. A parametric study of the economic performance based on monoethanolamine, International Journal of Greenhouse Gas Control, 1,136- 142.

Amararrene F., Bouallou Ch., (2004), Kinetics of carbonyl sulfide absorption with aqueous solutions of


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diethanolamine and methyldiethanolamine, Ind. Eng. Chem. Res., 43, 6136-6141.

Bello A., Idem R.O., (2005), Pathways for the formation of products of the oxidative degradation of CO2 loaded concentrated aqueous MEA solutions during CO2 absorption from flue gases, Ind. Eng. Chem. Res., 44, 945- 969.

Dallos A., Altsach T., Kotsis L., (2001), Enthalpies of absorption and solubility of carbon dioxide in aqueous polyamine solutions, J. Thermal Analaysis and Calorimetry, 65, 419- 423.

Hilliard M.D., (2005), Dissertation Proposal, University of Texas at Austin, 1-27.

Kohl A.L., Nielsen R., (1997), Gas Purification, 5th ed., Gulf Publ.Corp., Texas, 250-281.

http://www.chemicalland21.com/arokorhi/specialtychem/finechem/1,5,8,12-TETRAAZADODECANE.

Siminiceanu I., (2004), Procese chimice gaz- lichid, Editura Tehnopres, Iasi, 180- 288.

Siminiceanu I., Tataru-Farmus R.E., Amann, J.-M., (2006), Kinetics of carbon dioxide bsorption into aqueous solutions of etilenediamine, Buletinul Inst. Polit. Iaasi, Tom 52, 1-2, Chim. Ing. Chim., 45- 50.

Strazisar B.R., Anderson R.R., White C.M., (2003), Degradation pathways for MEA in a CO2 capture facility, Energy Fuels, 17, 1034- 1039.

Sun W.-C., Yong C.-B., Li M.-H., (2005), Kinetics of the absorption of carbon dioxide into mixed aqueous solutions of 2- amino- 2- methyl- 1- propanol and piperazine, Chem. Eng. Sci., 60, 503- 516.

Tanthapanichakoon W., Veawab A., McGarvey B., (2006), Electrochemical investigation of the effect of heat stable salts on corrosion in CO2 capture plants using aqueous solution of MEA, Ind. Eng. Chem. Res., 45, 2586- 2593.

Tataru- Farmus R.E., Siminiceanu I.,Bouallou Ch., (2007), Carbon dioxide absorption into new formulated amine solutions (I), Chemical Engineering Transactions, 12, 175- 181.

Thitakamol B., Veawab A., Aroonwilas A., (2007),Environmental impacts of absorption- based CO2 capture unit for post- combustion treatment of flue gas from coal fired power plant, International Journal of Greenhouse Gas Control, 1, 318- 342.

Versteeg G.V., van Swaaij W.P.M., (1988), Solubility and diffusivity of acid gases (CO2, N2O) in aqueous alkanolamine solutions, J. Che. Eng. Data, 33, 29- 34.



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URBAN TRAFFIC POLLUTION REDUCTION USING AN INTELLIGENT

VIDEO SEMAPHORING SYSTEM

Codrin Donciu∗, Marinel Temneanu, Marius Brînzilă

“Gh. Asachi” Technical University of Iasi, 53 Mangeron Blvd., 700050, Iasi, Romania

Abstract The present paper suggests making an intelligent video system of command over crossroads with traffic lights, its main goal being diminishing road congestion, a better traffic speed of vehicles, diminishing the environment pollution and improvement of negative effects that vehicle concentration has over the physical and psychological state of the population. Key words: vision, image processing, segmentation


1. Introduction

On a global level, after the Bureau of Transportation Statistics, Ward's, Motor Vehicle Facts & Figures 2006, total production of automobiles (both for passengers and trade) gas grown from 15.200 thousands automobiles in 1961, reaching values of 33.401 thousands in 1971, 37.136 thousands in 1981, 47.283 thousands in 1991, 57.528 thousands in 2000 and finally 65.750 thousands auto vehicles in 2005 as shown in Fig. 1. It is notable that the entire auto-park of the rolling vehicles is obtained by summing the production for a number of years equal to the average of vehicles circulation, a specific average for each country (Chen et al., 2000).

Fig. 1. Global vehicle production

The exponential growth of the last decade of

the rolling vehicle number, on both national and global level, is, among other factors, an important cause of chemo-physical pollution level growth, of augmentation of global warming, of phonic pollution and of stress risk factor enlargement (Dementhon et al., 2000). Further more, as noticed in Fig. 2, the waiting of the cars with the engine on, or the rolling with speeds below 12km/h induces a fast growth of CO, organic volatile substances and azotes oxides emissions (Fan et al., 2000).

In this context, this project suggests making an intelligent command video system of the traffic-lighted crossroads, its main goal being to diminish of traffic congestions, to improve vehicle speed, to reduce environment pollution and to improve negative effects of traffic congestion over the physic and psychic state of the population (Ferman et al., 1997). On international level, automatic advanced command systems of crossroad traffic-lightening have a bigger spread. They are classified according to the physical area of sensible elements mounting (sensors and traitors) and can be placed: at the traffic rolling level, in the pavement or along the traffic lanes. Detection throughout pavement mounted sensors is the most commonly used technology in the present (Haritaoglu et al., 2000).



564

Fig. 2. CO, VOC, NOX variation depending of vehicle

speed

At the traffic rolling level there are the following constructive alternatives: • loop plates, similar to conventional inductive

loops, meaning that they generate an electromagnetic field, troubled by a vehicle’s passing-by;

• pressure plates, which upon the wheels passing-by discharge an electric current. This device is limited to the axles passing-by, not vehicles;

• magnetometer, which measure changes in the Earth’s magnetic field upon a vehicle’s passing-by.

At the pavement level the following constructive alternatives are used:

• magnetic inductive loops are the type of detector the most commonly used. They generate an electromagnetic field that is troubled upon the vehicle passing-by, and that detects the vehicle’s presence in this manner. The size of a loop is generally 1x1,5m;

• magnetic probes measure changes in Earth’s magnetic field, in order to detect the vehicle’s passing-by over them.

• sensitive cables. Upon the vehicle’s passing-by over a sensitive cable, the tires produce compression of the piezoelectric cable, which generates instantly an electric signal. Hey cannot however measure some traffic parameters, and are limited to detection of the axle.

Along the traffic ways, there are video cameras installed, set into crossroads with the main target of indicating any violation of the red signal in traffic lights (Krumm et al., 2000). They use a trigger for the beginning of the record which comes from a sensor set into the pavement. If the red signal appears at the traffic lights, and the pavement sensor detects a vehicle moving above it, the record is started (Puzicha et al., 1999). The above presented systems are used in low traffic crossroads, being able to interpret information only from the near proximity of the sensors, but unable to estimate the number of vehicles waiting in line on a traffic lane (Sista et al., 2000).

2. System architecture This project approaches the build of an

intelligent command video system for traffic-lightening crossroads, its main goal being to diminish of traffic congestions, to improve vehicle speed, to reduce environment pollution and to improve negative effects of traffic congestion over the physic and psychic state of the population. It also brings up the possibility of extending this system to a macro-type that can also offer the benefit of a ‘green wave’ inter-synchronizing.

The architecture of the suggested system is made on a hardware level from three different areas: the video sensor’s level (video cameras), the computer process level and the represented execution level and the traffic-lights that exist in the crossroad. (Fig. 3).

Webcams have the role to import in real time images of the road traffic and can be placed depending on the urban configuration of the crossroad (if there are/are not trees/buildings higher than 12 m, slopes leaned more than 5 %) in two alternatives: AC – altitude camera with an overview of the crossroad, or CS – camera system set on the directions of the traffic lanes. In this last choice, one of the cameras must have an optic view transverse to the center of the crossroad, by mounting it in a diametric opposite point compared to the crossroad and monitor artery conjunction.

Fig. 3. System architecture

The process computer represents the hardware support of the algorithms and routines destined to

Urban traffic pollution reduction

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image processing and fuzzy control. The data transmission between the process computer, the video cameras and the execution elements is made by radio or cable, depending on the crossroad configuration.

The software architecture of this system is made out of the main routine and a number of secondary routines of image processing and of the Fuzzy command. The fundamental routine has, as target, the determination of the vehicle number waiting in line on a traffic lane. For this, as you can notice in Fig. 3, the main IP image, that comes from the altitude camera AC or the one obtained by reconstructing the image (RIT) from the CS camera system, is submitted to a pre-processing process for removing the video sounds, followed by a numeric differentiation process from the background image IF and by applying a ‘high-pass’ filter to emphasize shapes. The processing operation is done by segmentation, obtaining the IS image. By segmenting we get to make partitions of the numeric image into sub-sets, by attributing individual pixels to these sub-sets (also named classes), resulting into distinctive objects from the scene, through the bridge method. And so, because of the significant differences between the grey levels of the object’s pixels and the background’s, the segmenting criteria are the grey level value. The pixel corresponding to the coordinate point (i,j) is considered to be an object-pixel if it’s value (i, j) is higher than a bridge value.

Obtaining good results by this method depends of the way the bridge is chosen, which can be a value for a certain image that is given or a slim function that depends on the pixel’s positioning. The last stage of the fundamental routine is the N sequence of estimating the number of vehicles waiting in line and the build of the E (e1, e2, ……. en) vector, who’s elements are the numbers of vehicles standing in line on the road artery, and the index represents the number allocated to the road arteries (or to the traffic lanes, if on from way there are several directions that can be followed).

The secondary routines of image processing gather the event memory EM routine, the algorithm for unfriendly weather conditions detection DCMN and the emergency situations detection algorithm SDU.

The event memory routine uses a circular recording buffer with a stocking capacity of 48 h and its role is to provide witness video digital recordings for road-event like situations (road accident of robbery from vehicles in crossroads). The routine also fulfils the “running the red light” function. In the case of traffic violation by crossing over the red signal at the traffic-lighted crossroads a digital trigger is activated and an image of the vehicle is stored in a special location. The bad weather condition detection algorithm DCMN has as a goal establishing the visibility conditions in a crossroad and the road adherence by identification night/day, the existence of rain/snow weather phenomenon’s and deposition level on the road. The going-out value of this algorithm through the BI delaying block applies

corrections depending on weather conditions and the times provided by BCF. The DSU - emergency situations detection algorithm’s goal is to establish the approach to the crossroad of a light-signaled vehicle – ambulance, police car, firemen’s cars or official cars - followed by priority on the identified lane given by the Fuzzy BCF command block. The Fuzzy BCF command block is the central part of the whole traffic-lightening system and has the role to establish, upon the data send by the fundamental and secondary routines, the command times of the traffic-lights.

On an overview look, by its architecture, this project represents a high novelty solution with also high complexity in crossroads traffic-lightening, taking into consideration that such a configuration is not yet implemented. Development of the algorithms necessary to this crossroads traffic-lightening intelligent video system requires a interdisciplinary and complex approach of this matter, by putting together knowledge from domains such as: numeric view of the signals, Fuzzy artificial intelligence and data transmission.

In particular, the project is distinctive by the following novelty aspects: • the secondary routines for image processing (the

memory routine EM, the bad weather condition detection algorithm DCMN and the emergency situations detection algorithm SDU) give to this system a high level in command decisions making and furthermore is gives adaptability to traffic-lightening depending on weather conditions and emergency situations;

• the development of a new FFT image processing algorithm, with a processing speed higher than the classical alternative and with frequency, amplitude and phase errors substantially reduced, necessary to the co-existence of the two different processing types: the fundamental routine and detection algorithm of the bad weather condition detection by using an overview level processing, while the emergency situations detection algorithm uses an identification processing on a detail level;

• the making of an adjustable traffic-lightening to the necessities of the traffic type and conditions.

3. Conclusions

Development of proposed system has a large

impact under economical, health and environment aspect. Under economical aspect, taking into consideration the overwhelming growth of the vehicle number in the past decades, the existence of an intelligent traffic-lighted crossroad system has as an immediate result a better traffic flow efficiency, this being emphasized under reduction of the medium time travel on a certain itinerary. On another side, the fuel burnings due to repeated stops/slowing-downs and accelerations is reduced, with significant values on medium and long time length.


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Health impact. The pollution substances emissions, such as nitrogen oxides, hydrocarbons, CO, powders causes or contributes to a series of health problems. Within the impact over population health attributed to road traffic we can assume a higher incidence of cancers and lung and cardiac diseases. The technological improvements, which reduced the emission level, have been compensated by a traffic growth, and so emissions are still growing. Auto vehicles, and especially cars, are the main source of air pollution in urban areas on European level. Approximately 65% of the European Union’s population is submitted to unacceptably high noise levels – mainly produces by urban traffic. Although noise affects individuals in different manners, it causes both discomfort and health problems. Among the effects over the physiological and psychical state there are: a higher heart rate (with associated higher risk of cardio-vascular diseases), physiological trouble and higher daily stress level, sleep disorders, cognitive troubles, comprehension and focusing troubles for the children, and at very high noise levels, hearing problems.

Implementing a smart system traffic-lightening level has as a direct result a higher life level quality for the people living in areas next to traffic congestions, both through diminishing noise level produced by the engines and through diminishing concentrations of atmospheric pollutant’s emissions. Furthermore, there are lower exposure levels for bicyclists, pedestrians and other categories of unprotected persons, such as police crews stationary in crossroads or workers that are set next to high traffic congestion crossroads, etc.

Under environmental impact, pressures of the urban traffic upon environment are expressed by: • street noise and vibrations; • air pollution with particles, sediment powders,

NOx; • SOx, hydrocarbons, Pb; • air emissions of gases that have warming and acid

effects, therefore leading to global warming. Congestions and traffic delays raise the fuel

burnings and, obviously, the level of physical-chemical pollution of the air. Latest studies estimate that, in the European Union, the transportation sector is responsible for 28% of the total CO2 emission, the main gas in global warming. Of this value, 84%, so the biggest part comes from road vehicles.

While industrial emissions are lowering their values, in agreement with EU ratification through Tokyo agreement, transportation emissions are growing continuously. It is estimated that in 2010, emission level will be 40% higher than the one in 1990, despite the fact that EU target for this period is to diminish by 8 % gas emissions with global warming effect.

Transportation sector is responsible for 63% of NOx emissions, 47% of organic volatile compounds emissions, such as benzene, 10-25% of the powder emissions and 6,5% of the SO2 emissions in country-side areas, those values increasing in the urban areas.

Bu achieving this project’s objectives, the level of physical-chemical pollution in the interested areas will lower significantly, contributing in this manner in a specific way to the improvement of combat against global warming. Just as important, due to traffic continuous flow in crossroads, the level of phonic pollution will diminish also. At this point, the maximum allowed decibels level is 50, but the value reaches 80, or even 100 in the big crossroads, extremely troubling for residents of near-by areas. From electromagnetic pollution point of view, there is a lowering in the intermittent wide range perturbations, generated by the vehicle’s lightening installations and associated with intense traffic and crossroads congestions. These perturbations level in the GHz domain depends on the distance and number of vehicles on a given area, being able to cause some electromagnetic compatibility problems. References Chen C., Shyu L., Zhang C., Kashyap R., (2000), Object

Tracking and Augmented Transition Network for Video Indexing and Modeling, 12th IEEE Int. Conference on Tools with Artificial Intelligence, 1, Vancouver, May, 428.

DeMenthon D., Stuckelberg M., Doermann D., (2000), Image Distance using Hidden Markov Models, International Conference Pattern Recognition: Image, Speech and Signal Processing, 1, Barcelona, Sept., 147.

Fan L., Sung K., (2000), Model-Based Varying Pose Face Detection and Facial Feature Registration in Video Images, 8th ACM Int. Conference on Multimedia, 1, Los Angeles, Oct., 295

Ferman M., Guensel B., Tekalp, M., (1997), Object-based Indexing of MPEG-4 Compressed Video, Proc. of SPIE: Visual Communications and Image Processing, 1, San Jose, Feb., 953.

Haritaoglu I., Harwood D., Davis, L., (2000), A Fast Background Scene Modeling and Maintenance for Outdoor Surveillance, 15th IEEE Int. Conference on Pattern Recognition: Applications, Robotics Systems and Architectures, 1, Barcelona, Sept., 179.

Krumm J., Harris S., Meyers B., Brumitt B., Hale M., Shafer S., (2000), Multi-Camera Multi- Person Tracking for EasyLiving, 3rd IEEE Int. Workshop on Visual Surveillance, 1, Dublin, July, 3.

Puzicha J., Hofmann T., Buhmann M., (1999), Histogram Clustering for Unsupervised Image Segmentation, IEEE Computer Society Conference Computer Vision and Pattern Recognition, 1, Fort Collins, June, 602.

Sista S., Kashyap L., (2000), Unsupervised Video Segmentation and Object Tracking, Computers in Industry, 42, 127-146.



______________________________________________________________________________________________

STUDY OF INCREASING SOIL FERTILITY INTO A SITE

WITH HIGH ELECTRIC FIELD AROUND USING POLYMERIC CONDITIONING AGENT

Ioan Ivanov Dospinescu , Carmen Zaharia, Matei Macoveanu ∗,

“Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering, Department of Environmental Engineering and Management, 71A D.Mangeron Bd., 700050 - Iasi, Romania

Abstract This paper discusses the applications of synthetic PONILIT GT-2 anionic polyelectrolyte as soil conditioning agent into a site with high electric field around. All experimental data conclude that the use of a polymeric conditioning agent was increased the soil ability to support vegetation expressed as germination degree for some grass species (e.g., Raigras aristat). The performed values for germination degree increase from 3.05 % to 12.20 % when was added fertilized soil, and respectively, 38.98-73.17 % when is added polymeric agent. Moreover, the experimental data concludes that the use of lower polyelectrolyte concentration is indicated (e.g., < 5 mL polyelectrolyte solution of 0.5 % per 1 Kg soil). The negative environmental impact of high electric tension into the investigated site can be attenuated if is used a soil conditioning agent as Ponilit GT-2 anionic polyelectrolyte. Key words: PONILIT GT-2 anionic polyelectrolyte, soil conditioning agent, germination degree, soil fertility, Raigras aristat


1. Introduction

It had been widely recognised by government that soil protection is important within the concept of sustainable development. A report commissioned by the Environmental Agency identified a bias towards indicators designed to monitor the quality of soil with respect to its ability to support all vegetation including grassland, arable crops and trees or other “agricultural activities" rather than the full range of broad soil functions (e.g., food and other biomass production; storing, filtering and transformation of minerals, organic matter, water and energy, and diverse chemical substances; habitat and gene pool; physical and cultural environment for mankind; source of raw materials etc.). It recommended the adoption of a “goods and services” approach whereby the ability of soils to perform the wide range of functions society needs is implemented and the definition of “soil quality” varies with these functions (Tzilivakis et al., 2005).

The heterogeneity of soils, the wide range of functions and services they perform and the variety

and combination of pressures placed upon them all require much consideration. Soils are poorly understood when compared with other environmental media. They vary enormously in their chemical and physical constitution and, as a consequence, their ability to perform functions (Zaharia et al., 2006; Surpateanu and Zaharia, 2002).

Different activities place different pressures on the soil and cause different impacts. Across the Europe, the threats to soil include erosion, decreasing levels of organic matter, local and diffuse contamination, sealing, compaction, declining bio-diversity and salinisation (European Commission, 2002). Recently, it had been investigated the high electric field impact on environment but especially on soil with respect to its ability to support vegetation. A negative impact of high electric field on “soil quality” as vegetation support was reported into a Moldavian site (Zaharia et al., 2006). This negative impact can be reduced if are used soil conditioning agents.

This paper presents the experimental results of soil quality as vegetation support performed by using of a polymeric product (e.g., Ponilit GT-2 anionic


Ivanov Dospinescu et al./Environmental Engineering and Management Journal 6 (2007), 6, 567-572

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polyelectrolyte) as soil conditioning agent into a site with high electric field around. 2. Experimental 2.1. Site characterization and location

The studied site is a northern Romanian area having a total surface of 5 ha situated no more than 5 km from the Iasi town, named Uricani-Valea Lupului relays region. It is proposed an impact case study on soil fertility of some vegetal grass species induced by the high electric tension network, and improved by adding of soil conditioning agent such as an anionic polyelectrolyte.

The investigated site is traversed by aerial electric tension network corresponding to values of 40 – 70 V/m2 into all investigation period (Antohi and Ivanov Dospinescu, 2003).

2.2. Experimental procedure

The paper is focused on soil characterization

as vegetable support, and investigation of its ability to support some vegetal species of Raigras aristat into the investigated site presented above, with addition or no of fertilized soil and polymeric conditioning agent. The “soil quality” as vegetation support is expressed by its germination degrees.

The experiments are organized into special vegetation vessels having rectangular shape (150x 120x 50 mm) and perforated bottom. Into these vegetation vessels were introduced the studied soils (e.g., more than 3 cm height), and also some mixture between the soil from the investigated area and commercial fertilized soil for plants (e.g., mixtures of 1:1, 2:1, 1:2 and 1:3 studied soil/commercial fertilized soil). The fertilized soil is produced by Matecsa Ker.Es Kert Kft Hungary and has a pH value of 6.6-7.

The vegetal species, Lollium multiflorum, is a pretentious species that need a soil enriched in nitrogen, high light and water. The grass species grows rapidly, but can not resist more than 1-2 years [6]. The sowing with Lollium multiflorum was made according with the literature data (Canache, 1990), ensuring an average number of 12.500 – 15.000 seeds/m2 which correspond to 0.5 g seeds/vessel, about ca 164 seeds/vessel. After sowing into each vegetation vessels was introduced BIONAT fertilizer, commercialized by PANETONE Company, Timişoara, Romania containing the following important compounds: 74 g/L nitrogen (N), 3 g/L K (K2O), 0.2 g/L phosphor (P), 5 g/L magnesium (Mg), 10 g/L sulphur, 1 g/L calcium (Ca) and microelements (1-2 g/L).

Comparative studies were performed on soil treated with soil conditioning agent such as Ponilit GT-2 anionic polyelectrolyte, and the same growing condition of vegetal species (e.g., between 3 and 5 mL polyelectrolyte solution of 0.5 % per kg soil and good homogenization).

The PONILIT GT-2 anionic polyelectrolyte is an aqueous solution of a sodium copolymer salt based on maleic acid and vinyl acetate. The polyelectrolyte stock concentration used for this study was 0.5 % (the polyelectrolyte is patented by the “P.Poni” Institute of Macromolecular Chemistry, Iaşi) (Patent, 1981). This polyelectrolyte was industrially produced by the Chemical Enterprise of Falticeni and commercialized by “Chimica” Company, Bucharest having the following characteristics: amber colour, specific smell, pH of 6.5 – 8, content of active product into solution of 33 – 36 % (w/w), density of 1.18 – 1.21 g/cm3, water soluble, viscosity at 20 ± 1°C of 1500 – 1800 cP, average molecular mass of 2.105 – 3.106, no corrosive or toxic effect.

The germination degrees, which express the fertility efficiency of soil as vegetal support, are calculated with Eq.(1) (Surpateanu and Zaharia, 2000; Zaharia and Surpateanu, 2001):

Germination degree (%) = 100⋅i

f

nn (1)

where: ni – the initial number of seeds; nf – the final number of vegetal species.

A comparative study of the same soil samples cultivated with these vegetal species of grass was performed at laboratory scale set-up into almost the same operational condition but with no high electric tension around. A reference soil sample from other area (e.g., 5 km far from Iasi, opposite side), and a soil sample from 100 m far of the investigated site were analyzed in the same condition for comparison of the germination degrees. 2.3. Analysis Methods

The investigated soil was preliminarily analysed concerning the following physical and chemical indicators using standardized methods internationally approved: pH, carbon organic content, exchangeable calcium, total content of soluble salts, total phosphor, total nitrogen etc. (Surpateanu and Zaharia, 2002; Davidescu et al., 1981; Zaharia, 2005).

3. Results and discussion

All experiments were performed on soil

samples characterized by the main physical-chemical indicators presented into Table 1 in order to obtain compact grassland.

Into laboratory conditions, the coming up of vegetal species was normal, based on difference of soil fertility; higher for reference soil (soil sample-III), followed by soil samples 100 m far of the studied area (soil sample-II) and investigated soil (soil sample-I).

Study of increasing soil fertility into a site with high electric field around using polymeric conditioning agent

569

Table 1. Soil characteristics

Soil Sample pH

(active pH, water)

pH (Exchangeable

pH, KCl 1%)

Corganic, %

P (g p/kg

soil)

Exchangeable Ca2+

(mg/kg soil)

CaO %

TCSS*

mg/100 g

Relay soil 8.78 7.72 2.15 44.8 48 2.576 400

Soil- 100 m far 8.72 7.76 0.084 44.7 36 2.016 1115

Mixture 1:3

7.94 7.59 3.72 - 40 2.24 300

Mixture 1:1

8.15 7.64 1.14 - 40 2.24 716

Mixture 2:1

8.29 7.66 2.54 - 36 2.016 375

Reference soil 7.75 7.18 0.774 15.96 48 2.688 275

* TCSS – total content of soluble salts

Nevertheless, the vegetal growth was

accelerated the first six days for the reference soil, but during the investigated period was decreasing. For the commercial fertilized soil, the results are the best, almost total sowing of vegetal species (ca 91.20 %) and formation of a good grassland beginning with the sixth day. The daily evolution at laboratory scale set-up of grassland into the vegetation vessels are presented into the next table (Table 2).

Table 2. Evolution of vegetal species growth at laboratory

scale set-up

Day no/ soil type

Soil sample I

Soil sample II

Soil sampleIII

6th day - 5 mm 5-10 mm

7th day 5-8.5 mm 10 mm 25 mm

8th day 10-10 mm 10-35 mm 35-50 mm

9th day 10-45 mm 10-50 mm 40-60 mm

10th day 10-60 mm 15-70 mm 50-80 mm

11th day 20-70 mm 20-80 mm 20-90 mm

12th day 20-70 mm 20-80 mm 25-100 mm

13th day 20-80 mm 40-110 mm 35-90 mm

14th day 30-80 mm 30-110 mm 35-100 mm

15th day 35- 85 mm 40-110 mm 40-110 mm

16th day 35-90 mm 45-110 mm 40-115 mm

17th day 35-90 mm 30-110 mm 40-130 mm

The grassland was mowed down for improving of grass strength, and after the growth was decreasing

It can be seen that after thirteen days of

observations the vegetal species have heights higher than 10 cm, and that is way the grassland need to be mowed down. The germination degrees for these soil samples and vegetal species number was measured or calculated being presented into Table 3.

Table 3. Efficiency of vegetal species growth (laboratory experiments)

Efficiency/ soil vessel

Soil – I Soil – II Soil – III

Vegetal species number

46 85 128

Germination degree, %

28.05 51.83 78.05

I–investigated soil; II –100 m far of investigated soil; III– reference soil

It can be considered that the germination

degree was not so high because the sowing was performed on surface no deeply inside the soil. Although this vegetal species is sensible and was tested for different soils and conditions, the existence and growth of vegetal species was possible.

Table 4. Efficiency of vegetal species growth (A point, irrigation), no treatment with polyelectrolyte


Relay soil

(1:1) (2:1) (1:2) (1:3)

Vegetal species no.

5 20 10 20 5


3.05 12.20 6.10 12.20 3.05

On the investigated site were organized four

prelevation and observation points separated each other by 35-45 m under and around the high electric tension lines between two relays in condition of daily irrigation (e.g., maximum 3-4 mL water), no soil conditioning agent (series 0), and treatment of each soil vessel with polyelectrolyte (series I- 3 mL Ponilit GT-2 solution of 0.5 % per kg soil, and series II- 5 mL Ponilit GT-2 solution of 0.5 % per kg soil). Into each observation points were studied daily the vegetation vessels (1- investigated soil, 2- mixture 1:1, 3- mixture 2:1, 4- mixture 1:2, 5- mixture 1:3) treated with 0, 3 or 5 mL polyelectrolyte solution of 0.5 % per kg soil. During the whole period of study was measured the height of vegetal species, with the mention that after the height of 10 cm, the grassland was mowed down for improving of grass strength.


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The worst results for soil series 0 and I were performed into A observation point (Table 4 and 5) (Zaharia et al, 2006).

It can be seen that the growth of vegetal species on soil from the investigated site was lower than of soil mixtures. thus, the fertility efficiency can be improved by mixing the investigated soil with fertilized soil for necessary soil stabilization and with soil conditioning agent.

The best results into soil series I were performed for soil mixture 1:3 (relay soil/ fertilized soil), and reference soil, followed by soil mixture 1:1, and relay soil. The relay soil was not the worst situation. This growing evolution is based on soil type and electric field impact of relays from Uricani- Valea Lupului, Iaşi. The vegetal species number and germination degrees for these treated soil samples with polymeric soil conditioning agent (series I) were measured or calculated (Table 6).

It can be observed that the addition of commercial fertilized soil and polymeric conditioning agent had positive impact of vegetation growth.

For the series II of vegetation vessels were used an other polyelectrolyte dose, and other operational regime: into 1 litter of water is added 5 mL polyelectrolyte and 300 g soil. The mixture of aqueous soil suspension is agitated 30 minutes on a magnetic stirrer followed by separation of the two phases. The aqueous phase was eliminated (ca 75 %), and the soil was cultivated with grass species. The same operational procedure was applied for each soils or soil mixtures. The experimental data are presented in Table 7.

The vegetation number and germination degrees for series II are presented in Table 8.

The results are good enough for the soil mixtures but slow decreasing for relay soil, because of electric field impact, conditioning agent, and soil type (soil composition and characteristics).

The comparison between the three series of experiments (series 0, I and II) was synthesized into Fig.1.

Fig.1 The influence of polyelectrolyte dose on the germination degrees of grass species

Table 5. Evolution of vegetal species growth into A point (60 m first relay), and daily irrigation (series I – 3 mL

polyelectrolyte solution of 0.5 % / kg soil))

Heights of grass species (mm)

Day no.

Relay soil

Mixture 1:1

(relay soil /

fertilized soil)

Mixture 1:3

(relay soil/

fertilized sol)

Mixture 2:1

(relay soil/

fertilized soil)

Refe-rence soil

1-6 - - - - - 7 - - 3 mm - 5 mm 8 - 5 mm 10 mm - 15 mm 9 5 mm 10 mm 18 mm - 25 mm

10 15 mm 20 mm 28 mm 3 mm 40 mm 11 28 mm 30 mm 40 mm 5 mm 60 mm 12 40 mm 45 mm 55 mm 10 mm 70 mm 13 60 mm 60 mm 75 mm 20 mm 90 mm 14 73 mm 71 mm 88 mm 26 mm 96 mm 15 80 mm 85 mm 95 mm 35 mm 98 mm 16 85 mm 95 mm 100 mm 40 mm 102 mm 17 90 mm 100 mm 102 mm 43 mm 105 mm 18 95 mm 102 mm 105 mm 45 mm 107 mm 19 103

mm 108 mm 112 mm 47 mm 115 mm

20

120 mm 119 mm 130 mm The grass is mowed down for

improving of grass straight

50 mm 130 mm The

grass is mowed down

21 125 mm 130 mm The

grass is mowed down

10 mm 50 mm 10 mm

22 128 mm 10 mm 18 mm 52 mm 18 mm

23 130 mm

The grass is mowed down

20 mm 20 mm 60 mm 20 mm

24 10 mm 25 mm 24 mm 70 mm 23 mm 25 15 mm 29 mm 25 mm 80 mm 23 mm 26 15 mm 30 mm 25 mm 80 mm 27 mm 27 16 mm 31 mm 28 mm 82 mm 30 mm 28 17 mm 31 mm 29 mm 85 mm 30 mm 29 20 mm 35 mm 30 mm 90 mm 30 mm 30 22 mm 36 mm 31 mm 100 mm 32 mm 31 25 mm 38 mm 32 mm 105 mm 32 mm 32 27 mm 39 mm 33 mm 111 mm 34 mm 33 21 mm 37 mm 33 mm 114 mm 34 mm 34 22 mm 40 mm 36 mm 117 mm 35 mm 35 25 mm 42 mm 39 mm 122 mm 37 mm 36 25 mm 44 mm 42 mm 127 mm 39 mm

37

28 mm

46 mm

46 mm

130 mm The

grass is mowed down

40 mm

38 30 mm 49 mm 48 mm 10 mm 42 mm 39 32 mm 51 mm 50 mm 11 mm 45 mm 40 37 mm 55 mm 52 mm 14 mm 50 mm 41 39 mm 70 mm 53 mm 17 mm 52 mm 42 42 mm 75 mm 55 mm 22 mm 52 mm 43 44 mm 78 mm 56 mm 26 mm 55 mm 44 45 mm 80 mm 58 mm 29 mm 57 mm 45 47 mm 82 mm 60 mm 30 mm 59 mm

Study of increasing soil fertility into a site with high electric field around using polymeric conditioning agent

571

Table 6. Efficiency of vegetal species growth (investigated

site, series I)

Table 7. Evolution of vegetal species growth into A point

(60 m first relay), and daily irrigation (series II – 5 mL polyelectrolyte solution of 0.5 % / kg soil)

Heights of grass species (mm)

Day no

Relay soil

1:1 1:3 Reference soil

2:1

1....8

- - - - -

9 - 5 mm 8 mm 5 mm 5 mm 10 - 10 mm 10 mm 8 mm 10 mm 11 - 14 mm 18 mm 10 mm 15 mm 12 - 20 mm 28 mm 20 mm 20 mm 13 - 23 mm 40 mm 31 mm 26 mm 14 - 28 mm 50 mm 43 mm 29 mm 15 - 34 mm 70 mm 50 mm 32 mm 16 5 mm 38 mm 85 mm 70 mm 38 mm 17 10 mm 40 mm 97 mm 90 mm 42 mm 18 20 mm 43 mm 105 mm 100 mm 50 mm 19 30 mm 48 mm 115 mm 110 mm 50 mm 20 40 mm 50 mm 125 mm 120 mm 52 mm 21

40 mm 55 mm 130 mm The grass is mowed down for improving of grass straight

130 mm The grass is mowed down for improving of grass straight

53 mm

22 42 mm 60 mm 10 mm 10 mm 55 mm 23 45 mm 70 mm 15 mm 15 mm 65 mm 24 45 mm 78 mm 25 mm 23 mm 70 mm 25 47 mm 85 mm 30 mm 29 mm 75 mm 26 47 mm 90 mm 40 mm 40 mm 80 mm 27 50 mm 112 mm 46 mm 45 mm 82 mm 28 52 mm 120 mm 50 mm 50 mm 90 mm 29

53 mm 130 mm The grass is mowed down

62 mm 60 mm 110 mm

30 55 mm 10 mm 70 mm 70 mm 120 mm 31

55 mm 15 mm 78 mm 77 mm 130 mm The grass is mowed down

32 58 mm 20 mm 85 mm 85 mm 10 mm 33 58 mm 25 mm 93 mm 93 mm 20 mm 34 60 mm 33 mm 100 mm 100 mm 30 mm 35 60 mm 40 mm 110 mm 110 mm 40 mm 36 64 mm 45 mm 115 mm 115 mm 50 mm 37 64 mm 50 mm 120 mm 120 mm 60 mm 38 64 mm 50 mm 120 mm 120 mm 60 mm 39 64 mm 55 mm 123 mm 122 mm 65 mm 40 64 mm 57 mm 126 mm 125 mm 70 mm

It seems that for the series II the germination degrees were almost twice times higher than of series I. The addition of soil conditioning agent favourites the increase of ability to support vegetation, particularly Raigras aristat species, into a site characterized by negative influence of high electric field on soil quality.

The remediation of soil quality using the polymeric soil conditioning agent can be applied on the investigated site, but additional studies must be taken into consideration.

Table 8. Efficiency of vegetal species growth (investigated

site, series II)


Relays Soil

1:1

1:3 2:1 Reference soil


12 65 120 40 60


7.32 39.63 73.17 24.39 36.59

4. Conclusions

The soils from the investigated northern

Romanian site with high electric tension around are not efficient supports for growth of Raigras aristat species because of the electric field around (e.g., 40 – 70 V/m2 for all investigation period), but also because of soil characteristics and meteorological condition on the site during the experiment period.

The applications of synthetic PONILIT GT-2 anionic polyelectrolyte as soil conditioning agent into the investigated site and high electric field around have positive impact on “soil quality” as support for vegetation species.

The performed values for germination degree increase from 3.05 % to 12.20 % when was added fertilized soil, and respectively, 38.98-73.17 % when is added polymeric conditioning agent. Moreover, the experimental data concludes that the use of lower polyelectrolyte concentration is indicated (e.g., < 5 mL polyelectrolyte solution of 0.5 % per 1 Kg soil).

The negative environmental impact of high electric tension into the investigated site can be attenuated if is used a polymeric soil conditioning agent as the anionic polyelectrolyte based maleic acid and vinyl acetate. References

Antohi C., Ivanov Dospinescu I., (2003), Radiation sources

and protection technologies, Performantica Press, Iasi, Romania.

Canarache A., (1990), Physics of agricultural soil (in Romanian), Ceres Press, Bucharest, Romania.

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Relay soil

1:1 (relay soil/

fertilized soil)

1:3 (relay soil/

fertilized soil)

2:1 (relay soil/

fertilized soil)

Refe-rence soil


33

42

59

24

60

Germi- nation degree, %

20.12

25.61

36.98

14.63

36.59


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METHODS AND PROCEDURES FOR ENVIRONMENTAL

RISK ASSESSMENT

Brînduşa Mihaela Robu∗, Florentina Anca Căliman, Camelia Beţianu,

Maria Gavrilescu

“Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering and Environmental Protection, Department of Environmental Engineering and Management, 71Mangeron Blvd., 700050 - Iasi, Romania,

Abstract This work presents the state of the art of qualitative and quantitative risk assessment methodologies in a variety of fields. Because risk exists in all ranges of human activity, both private and professional, risk assessment is an attempt to analyze precipitating causes of risk in order to more efficiently reduce its probability and effects. Numerous methodological guidelines within the field of environmental science exist to provide guidance for a risk assessment program, although the level of verifiable quantitative data, such as specific chemical effects and scientifically proven hazards, make a direct transfer of methodologies impossible. The risk-assessments and their key principles detailed within can be also used to assist in the development of decision making process. The common notion of risk is associated with actions or decisions that may have undesired to outcome. This implies that the risk-based approaches focus on the negative impacts and their prevention. Risk assessment places the emphasis on the potential negative environmental impacts of an organization’s activities and allows the identification of indicators that directly reflect its efforts, efficiency and effectiveness in reducing or even preventing them. Risk assessment is one of the steps of the general risk management procedure. Risk management is a technique used to identify, characterize, quantify, evaluate and reduce losses from actions or decisions that may have undesired outcomes. The first step of the generic procedure involves the risk identification that is the systematic identification of all potential actions or decisions with undesired consequences that may result from the operation of an organization. The next step involves the risk assessment, while further steps address issues like the evaluation of risks in order to determine the organizations ability or willingness to tolerate their consequences in view of the associated benefits, and the selection and implementation of the most preferable approach for the reduction of unacceptable risks. Lately, the trend is to integrate the risk principle into impact assessment procedure, and reasons for that are: risk assessment (RA) provides a structured framework for dealing with uncertainty in the assessment of impacts being the subject of debates and concerns, especially, concerning impacts on public health; environmental risk assessment (ERA) is specifically developed to address health issues and contains elaborate techniques for enhancing health impacts assessment comprehension in environmental impact assessment (EIA); ERA emphasizes scientific quantitative approaches and techniques in impact identification and evaluation and for improving the technical background for decision-making; closer cooperation between the environmental impact assessors and risk assessors and creation the mixed expert team would allow for more effective information collecting into environmental assessment process; ERA can be applied not only at the stage of impact prediction and evaluation, but also during project implementation and post-closure stages (over the whole project life cycle). Keywords: environmental risk assessment, models for risk assessment, event-tree risk analysis, HAZAN, HAZOP, integrated environmental impact and risk assessment

∗ Author to whom all correspondence should be addressed: e-mail [email protected]

1. Environmental evaluations into decision making process

Probably the most frequently argued thesis in environmental evaluation is that public perceptions have no place in environmental policy decisions because laymen do not have the knowledge to

evaluate accurately what may be the changes and consequences in the environment due to a certain (development) action, or what is best for society. Thus, the resulting judgments on alternatives and their acceptability will be subject to noise or bias.


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Analyses performed by experts should be free from such errors (Barrow, 1997; Calow, 1998). Nevertheless, besides an ethical foundation, one of the main reasons why the public should also be involved in the environment related decision making process is that the science itself is not capable of answering crucial questions regarding environmental valuation (O’Connor and Splash, 1999).

A fact which undoubtedly supports openness and transparency in environmental decision-making is the uncertainty of predictions of impacts (Morris and Therivel, 1995; Robu, 2005). It is often said that prediction is difficult, especially concerning the distant future. The response of science to uncertainty is routinely framed in the language of probability theory, but such probabilities are rarely ‘pure’. The risk analyst typically needs to invoke a variety of assumptions and hypotheses in order to estimate the impacts and their corresponding probabilities. Also, situations where one has to apply value judgments, preferences and expert opinion as inevitable components of the evaluation process are not exceptional (Andrews, 1988; Barrow, 1997; Cooke, 1991).

The common notion of risk is associated with actions or decisions that may have undesired to outcome. This implies that the risk-based approaches focus on the negative impacts and their prevention (Hokstad and Steiro, 2006). Risk assessment places the emphasis on the potential negative environmental impacts of an organization’s activities and allows the identification of indicators that directly reflect its efforts, efficiency and effectiveness in reducing or even preventing them. Risk assessment is one of the steps of the general risk management procedure. Risk management (Lalley, 1982; Kolluru et al., 1996; Aven and Kristensen, 2005) is a technique used to identify, characterize, quantify, evaluate and reduce losses from actions or decisions that may have undesired outcomes. The first step of the generic procedure involves the risk identification that is the systematic identification of all potential actions or decisions with undesired consequences that may result from the operation of an organization. The next step involves the risk assessment, while further steps address issues like the evaluation of risks in order to determine the organizations ability or willingness to tolerate their consequences in view of the associated benefits, and the selection and implementation of the most preferable approach for the reduction of unacceptable risks (Kolluru et al., 1996; Karrer, 1998).

Risk assessment, in general, refers to the decision making as far as the viability of a system is concerned, where the term system refers to any potential infrastructure (e.g. industry, bridge, software system, etc.). The viability of a system depends on the requirements upon which it has been built, which implies that a significant volume of information should be gathered in order to examine whether these requirements have been satisfied (Andrews, 1988; Den Haag et al., 1999). For a rational decision-

making regarding the risk assessment and the satisfaction of the system’s requirements, the following should be considered (Barrow, 1997; Christou and Amendale, 1998):

• the requirements and goals that have been set at the strategic planning of the system;

• the probability of failure to achieve the goals that have been set; and

• the consequences resulting from any failure to achieve the goals that have been set.

Environmental Impact Assessment (EIA) aims to predict environmental impacts at an early stage in project planning and design, find ways and means to reduce adverse impacts, shape projects to suit to the local environment and present the predictions and options to decision-makers, while the life cycle assessment (LCA) is estimating environmental burdens for energy and materials used and wastes released into the environment, and identifying opportunities for environmental improvements. The assessment includes the entire life cycle of the product, process or an activity starting from extraction (or excavation), processing, manufacturing, transportation, distribution, use, recycle, and final disposal. The LCA guides regulatory agencies and other stakeholders for decision-making in design, selection and evaluation of a process. It may be used to evaluate the environmental impacts of a segment within a product or process’s life cycle where the greatest reduction in resource requirements and emissions can be achieved. By using EIA and LCA both, environmental and economic benefits can be achieved, such as reduced cost and time of project implementation and design, avoided treatment/clean-up costs and impacts of laws and regulations (http://www.uneptie.org/pc/pc/tools/pdfs/EIA2-rpt.pdf). 2. Risk assessment – tool of environmental management system

To evaluate the quality of environmental components (air, water, soil, and human health), environmental management applied tools as risk assessment (RA), environmental impact assessment (EIA), life cycle assessment (LCA). EIA has tended to focus on the identification of impacts associated with planned activities or projects (Demidova, 2001; Robu, 2005), whereas environmental risk assessment (ERA) involves a rigorous analysis of those impacts: the calculation of the probability, and magnitude of effects (Robu and Macoveanu, 2005a,b). The reasons for integrating RA and EIA into one analytical procedure are of big interest (Jaeger, 1998; Robu, 2005):

- RA provides a structured framework for dealing with uncertainty in the assessment of impacts being the subject of debates and concerns, especially, concerning impacts on public health;

- ERA is specifically developed to address health issues and contains elaborate techniques for

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enhancing health impacts assessment comprehension in EIA;

- ERA emphasizes scientific quantitative approaches and techniques in impact identification and evaluation and for improving the technical background for decision-making; closer cooperation between the environmental impact assessors and risk assessors and creation the mixed expert team would allow for more effective information collecting into environmental assessment process;

- ERA can be applied not only at the stage of impact prediction and evaluation, but also during project implementation and post-closure stages (over the whole project life cycle).

Environmental impact and risk assessment consider human health and environmental components issues from different aspects. For this reason one can assume that the integration of risk assessment (RA) and environmental impact assessment (EIA) is a complex issue, which deserves to be considered from different aspects. The assessment of the risk may be realized through the use of either qualitative or quantitative methods (Karrer, 1998; Tixier et al., 2002).

The use of qualitative methods requires a sound level of knowledge and experience, while the use of quantitative methods requires a significant level of reliable information. The application of a qualitative method provides a better understanding of the system’s performance from the very beginning, even before any quantitative information become available. A quantitative method, on the other hand, allows the quantification and more precise estimation of the probabilities and the potential negative consequences. The best approach is the combination of both qualitative and quantitative methods.

The final output from risk assessment is an estimated measure of risk (Khan and Haddara, 2003). However, the process also provides a good understanding of the way the consequences of any failure to achieve a goal may reach and affect the environment. When risk assessment is constructed in a good and comprehensive way, it may go even further and include social and political consequences of environmental incidents, thus indicating short and long-term negative business impacts like the loss of brand loyalty, customer loyalty and corporate image (Karrer, 1998).

The application of risk management tools aid in selection of discreet, technically feasible and scientifically justifiable actions that will protect environment and human health in a cost-effective way. The risk based on life cycle assessment (RBLCA) is a process of weighting policy alternatives and selecting the most appropriate action by integrating the environmental risk assessment with social, economic, and political attributes to reach a decision (Sadiq and Khan, 2006).

The RBLCA will choose the alternatives, which cause minimum environmental damages and evaluate the costs and benefits of proposed risk reduction programs.

The RBLCA may integrate sociopolitical, legal and engineering factors to manage risks and environmental burdens of a process. The RBLCA considers human health, ecological, safety and economical risks information, which may involve preferences and attitudes of decision-makers (Sadiq and Khan, 2006).

The LCA starts with the identification of environmental hazards expected at various units (AICE, 1992). These hazards are due to the chemical compounds involved in the process that upon release adversely affect to humans or to the environment. It also includes hazard due to severity of operating conditions like temperature and pressure. The chemical hazards are not limited to process chemistry, rather they include cleaning solvents, heating and cooling agents, and all other chemicals involved in any part of the process. Generally, environmental impact and risk assessment (EIRA) examines the potential and actual environmental and human health effects from the use of resources (energy and materials) and environmental releases. An EIRA includes as main steps the followings: classification, characterization, and valuation. 3. Procedures for risk assessment 3.1. General considerations

The environmental risk is the result of the

interactions between the human activities and the environment. The ecologic risk management that refers to the problematic of the risks generated by the past, present and future human activities on flora, fauna and ecosystems constitutes only a part of the environmental risk management.

The environmental risk management is framed within two categories (Barrow, 1997):

Environmental risk: this type of risk admits the fact that the activities of an organization may generate certain environmental changes. The environmental risk refers to the:

• Flora and fauna • Human health and economic wealth; • Human social and cultural wealth; • Water, air and soil resources; • Energy and climate.

Risk for organization, from the point of view of environmental problematic: this category includes the risk of non-conformation with the legislation and current or future criteria. In this category are also enclosed the casualties in organization business registered from an inadequate management, deterioration of the company credit, costs of lawsuits and difficulties to ensure or least to maintain the possibility to continue the operation and development activities. The problems concerning the work safety and health as well as the risk management in emergency situation may be significant from the environmental risk point of view.


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The environmental risk management provides a formal set of processes that constitutes the fundament for environmental decision making and support the decision factor in the steps of incertitude level minimization. 3.2. Qualitative risk assessment 3.2.1. Control list

Control list, generally, identifies known, predictable risks and refer to standards. The following techniques are used: • DSF – “Diagnosis Safety Form” is based on a

questionnaire containing 50 questions concerning problems related to technical equipment, environment, production planning etc.

• DCT – “Diagnostique et Conditions du Travail” contains a questionnaire similar to the above described one, but in this case the evaluation is performed in three stages: good, average and poor;

• SQD – “Safety Diagnosis Questionnaire” has as purpose the identification of the critical situations concerning the incompatibilities between technical and organizational conditions, on a hand, and the safety requirements of the activities, on the other hand.

• MORT – “Management Oversight and Risk Three” uses a questionnaire containing around 300 questions with optional answers. It is focused on human activities and was conceived with the aim at significantly enhance the performances regarding the system safety.

3.2.2. Integral inspections of the industrial units Within current interpretation, the integral inspections emerged as a necessity to develop the measurable characteristics of the safety systems performances. These inspections give useful information on the activities concerning design, construction, starting-up, operation, closing in, disassembly and storage of the plant components. The integral inspections take places on three levels, the operators, experts and authorities having specific tasks (Gavrilescu, 2003): • constant inspection of the plant and its

components operation by the process managers and inspectors entrusted with special tasks;

• initial and periodic inspections at pre-established intervals by independent experts, eventually from the exterior of the system;

• announced inspection of the local authorities in order to issue the working license, as well as not announced inspections.

In close relation with plant inspections is the audit that represents, in broad sense, an independent investigation of the activities in field and constitutes a part of the management system of plant safety. This involves a program containing systematic questions (clearly formulated and addressed to the person

responsible for plant units), answers evaluation and action plan defining. 3.2.3. Ranking Ranking refers to identification of danger sources in designing phase or comparison of the plants situated on a working industrial platform. There are thus, quantified the potential risk sources by conferring corresponding levels of importance and establishing prevention measures. 3.2.4. Preliminary Hazard Analysis (PHA)

PHA focuses on the regions were hazardous materials are concentrated, as well as on the main units, monitoring the places where it is possible to result uncontrolled hazardous substances leakages or energy losses. The main considered points are:

• used substances in the process and potential danger;

• system units; • interfaces between system components; • environment; • system operations; • endowments; • safety equipments.

3.2.5. “What if” Method This method is based on iteration of some series of questions that lead to identification of the unexpected events with eventual unfavorable consequences and is applied on specific activity fields (Gavrilescu, 2003). A. Analysis of the faults, effects and critical states

This analysis may be done at both qualitative and quantitative levels and focuses on plant/system components. It is based mainly on elaboration of a table, which contains:

• equipment position, name and description; • faulting ways; • consequences; • assignment of critical coefficients on a

conventional scale previously established. The algorithm of the method involves the

following steps: • defining of the system; • identification of the faulting way; • analysis of the faulting causes; • analysis of the faulting effects; • analysis of the compensation possibilities; • assessment of the risk associated to each

faulting way; • proposals for remediation and prevention

measures. In the first stage, the main and secondary

functions, the role of the components, the working related interdictions and the acceptable working limits are established; there are also elaborated the flow sheets for clarifying the interconnections between the components.


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In the second stage, the framing within one of the following 5 faulting ways is foreseen: • blocked at zero – breaking of a connection,

short-circuit; • degradation – pipe cracking, plant mechanical

weakening; • intermittent switching-out –electronic elements

working accidentally; • undesired secondary effect.

The third stage is developed concomitant to the identification of faulting ways. The material components (technological equipments- wear and deformation) and energetic fluxes inserted by the respective component are studied. The effects analyzed in the forth stage are classified in local (at the level of the component that is damaged) and general (at the level of the whole system).

The analysis of the effect compensation possibilities consists in: • reduction of the fault occurrence possibility

(safety devices, preventive maintenance); • diminution of the propagation effects in the

system (components doubling, signaling devices); • reduction of the consequences (use of the

protective means). In the sixth stage, the assessment of the risk

associated to each fault way is done in relation to the severity (G) and probability (P). The qualitative analysis assigns scores on the scale 1 - 6: For severity level:

Ignorable – does not involve working accidents or material damages; Marginal – admits corrective measure for preventing the working accidents or material damages Serious – needs urgent measures Major – serious working accidents or system damages Major - serious working accidents or system damages at the company level Major – serious working accidents or system damages exceeding the company level.

For the probability level:

Extremely rare - p<10-9; Very rare – 10-9 < p < 10-7; Rare10-7 < p < 10-5; Low frequent - 10-5 < p < 10-3; Frequent - 10-3 < p < 10-2; High frequent - p > 10-2.

In the case when combination (G – P) has the following values: 4 – 5; 4 – 6; 5 – 4; 5 – 5; 5 – 6; 6 – 3; 6 – 4; 6 – 5; 6 – 6, the risk is considered as being unacceptable. Finally, remediation measures are proposed with the aim at minimizing the risk (risk management). For unacceptable risks primary, secondary and tertiary measures are proposed (referring to the la possibilities to control the accident consequences).

B. Analysis of human errors

The human errors defined as mistakes, lack of concordance between perception and objective reality confirmed by the practice are inevitable and not predictable. For this reason, it is very expensive to ensure the safety due to the difficulty to anticipate the multitude of the possibilities to affect the process/plant/system safety through negligence or fatigue. However, one may apply elaborated packages of prevention measures for diminishing the human contribution to the major accidents if the type of possible error is known.

A classification of the human errors could be the following:

• Errors appeared due to a moment of lack of attention;

• Errors owed to an improper instruction/training;

• Errors owed to weak mental and physic abilities of the operator;

• Errors appeared due to wrong decisions; • Errors committed by managers.

3.2.6. HAZOP method

The objectives of the HAZOP (hazard operability) methods are (Crawley, 2000): • Identification of the hazard locations, • Ascertainment of the project particularities

that lead to identification of the probabilities of some undesired events occurrence,

• Establishment of the necessary information for design from the perspective of ensuring the plant reliability,

• Initiation and development of quantitative studies related to hazard and risk.

Traditionally, the safety in chemical plant design is based on designing and exploitation codes, as well as on control lists achieved by using experience and knowledge of the experts and specialists from industry. Unfortunately, such approaching may solve only existing problems. Once the complexity of modern plants increased, these traditional methods lost their importance, being considered that their application in design phase is the most recommendable (Crawley, 2000).

HAZOP was elaborated as an applied technique for systematic identification of the potential hazards and operation problems in the new plants. Through HAZOP, a critical examination of the plants or processes by an experimented team is done in order to identify all the possible deviation from a certain project alongside the undesired effects on safety, operation and environment that would appear. The possible deviations are found by using rigorous questionnaires, containing key-words, applied to the analyzed project.

The success or the failure of the study depends on: accuracy of the project or of other data used for the study; technical skills or experience of the team; ability of the team to use the method as


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support for prediction of the possible deviation, cause and consequences. HAZOP will be beneficial during design or assembly of new a plants/process or during major modifications of the existing one; when hazard for environment/quality or problems of costs associated with operation appear; after a major incident that implies burning, explosions, toxic substances leakage; when must be explained why an industrial or practice code cannot be followed (AICE, 1992; Gavrilescu, 2003). 3.3. Quantitative risk assessment 3.3.1. Analysis

HAZOP studies are able to identify the hazard but do not provide quantitative information on the values referring to the probabilities to occur events that lead to undesired consequences. Many events are needed to join for resulting in the occurrence of an incident as damage of the process units and equipments or systems of control, improper operation etc. Thus, sequences of chain events that would results in appearance of hazardous incidents in the shape of logic trees may be defined, such as events tree (ET), and fault tree (FT), respectively.

Among the common stages of the risk quantitative analysis, assessment of frequency (probability) refers to three main components: acquiring of information from similar situations previously occurred, elaboration and analysis of the logic tree, analysis of the damages resulted in common situations. ET and FT are logic schemes, which describe the course of the possible events as well as their combination. The former starts from certain undesired events and goes further by upward exhibiting the evolution of all identifiable and possible situations in the shape of a tree. The fault tree starts from a damage and follows the cause-effect system up to exhaust of all foreseen events. The previous experience inserted in data bases with a multitude of possible scenarios and values of the probabilities calculated considering the nature of hazard, is used in this stage. Briefing, any HAZAN (hazard analysis) consists in three stages:

1. Assessment of the frequency of the accident recurrence;

2. Assessment of the consequences upon the employees, local community and environments or equipment and profit;

3. Comparison of the first two stages with a target or criteria in order to decide if the hazards are severe and what measure should be taken for reducing the possibility of accident occurrence.

The methods used in the first stage are probabilistic. It should be assessed how often the incident may take place, as well as when it may not happen. The methods used in the second stage are partially probabilistic and partially deterministic. For example, in the case of flammable gas loss, only the

probability of its ignition can be estimated. If this happen, the radiant heat as well as its loss with the distance may be assessed (deterministic).

The damage of the equipments or the errors in operation of a process emerges as a result of the complex interaction between the components. The general probability of faults within a process is strongly dependent by the nature of the error. • Hazard Frequency (H) – number of events per

year that determine the hazards occurrence. For example, the frequency of pressure increasing toward the value established when the reactor was designed.

• Protection systems – systems that are specially installed for hazards prevention (for example, safety valves).

• Testing Interval (T) – the protection systems should be tested for establishment of the response capacity concordant to technical recommendation. T is the interval of time between two successive tests.

• Demand frequency (requests of use) (D) – frequency (occasions/year) of demanding a protection system. For example, frequency of reaching the level of safety valve loading by the pressure.

• Fault frequency (f) – frequency (occasions/year) of working faults appearance in the case of a protection system. For example, a safety valve may break down at the normal operation pressure.

• Dead-time fraction (fdt) – fraction of time when the protection system is not active. Probability not to function when a need exists. If the protection system is continuously operated, the hazard frequency H is zero. The hazard occurs when the demand of use of the protection system appears in a dead-time: H = D x fdt.

3.3.2. Fault Tree Analysis

The damages or the faults may be classified in: • primary damages, which emerge in the designed

working conditions of the equipment; • secondary damages that appear in situations for

which the system was not designed; • command damages for the case when the system

works properly but in the wrong place and moment.

The stages of elaboration of the fault tree are:

• defining a top event, as for example, loss of gas

ammonia form the storage tank: no…warehouse….plant…during normal working conditions;

• defining the limits of the system subjected to analysis;

• elaboration of the tree taking into account the following rules:


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o inside the contour of the events signs, their description is inserted without directly linking two connections (the events will be described after each connection);

o the tree is elaborated on levels, downward from the top;

o a level is constituted by an array of connections situated at the same distance by the top event and the prior events of the respective connections;

o it is not allowed to go to the next level until the current event is exhausted.

• solving of the free tree involves finding of minimal sequences. A sequence represents an array of events that results in an accident. The minimal sequences are successions of this type that contain a minimum number of events.

Before properly accomplishment of the tree,

the following steps should be done: • Defining of the top event (e.g. high

temperature from the reactor). • Defining of the determinant event: conditions

of occurrence. • Defining of the not-allowed events: damages

at the system for power supply, faulting of the switches etc.

• Defining of the physical conditions of the process: the limits should not be taken into account. For example, in elaboration of FT, the units situated upstream and downstream of the reactor will not be considered.

• Defining of the configuration of the equipments from the system.

• Establishment of the detailing level. After completion of these steps, one may

proceed to the properly elaboration of the fault tree. First, the top event is drawn in the upper part of the scheme. This will be labeled precisely for avoiding the further confusions. Then, the major events that contribute to achievement of the top events should be identified. If these occur in parallel, will be linked through an AND connection. If they occurs in series, will be connected through OR.

3.3.3. Event Tree Analysis (ETA)

ETA is an inductive logic model that identifies the possible results of a given initiating event. An initiating event will commonly result in an accident or an incident.

ETA considers the responses of the operators and safety systems to an initiating event. This technique is the most suitable for analysis of complex processes that involve few safety systems or emergency procedures.

The first stage in conceiving an event tree is the defining of an initiating event that may lead to the damage of the system: equipment or utilities faulting, human error, natural disasters. The next step is the identification of the intermediate actions for removal or reduction of the initiating events effects.

The event tree contains two branches for every intermediate event, one for a successful exploitation and other for a faulty exploitation of the system. The upper part represents the success, while the bottom part represents the failure. Within a simplified model, the initiating events become the damage of P2. There are some response stages at the initiating event that include the warning alarm for the minimum flow rate, the response of the operator and damage of P1.

The assessment using the event tree analysis

contains the following steps (an example): 1. equipment is damaged and becomes the

initiating events. Probability of this event was defined as being 1.

2. The warning alarm for minimum flow at the vessel may work or fail. If it works, the upper branch is covered. If it doesn’t wok the bottom branch is covered. The warning has a success probability of 0.998.

3. The operator either respond or not to the warning alarm. Probability of responding is 0.952.

4. The last response is the fact that the operator put the equipment into operation. Probability of this event is 0.995. The event tree analysis is the best analysis

for the initiating event that may lead to the final effect of the event. Each branch of the tree constitutes a separate sequence of the relationships between the safety functions of the initiating event. Considering the same system and the same hypothesis concerning the probabilities, identical results may results through the both methods.

The fault tree is larger then the events tree owing to the fact that the latter is based on a single effect related to the damage. Many people are tempted to think in a logic manner about the safety systems using the events tree approaching. Risk assessment throughout the tree event may be summarized as follows (Gavrilescu, 2003):

• identification of the initiating events that may be

materialized in accidents; • identification of the safety functions for

diminishing the initiating events; • elaboration of the event tree; • description of the results of an accident and its

probability. 3.4. Environmental risk assessment in accordance to MAPPM Order no. 184/1997

The environmental risk assessment

(concordant to Ministerial Order no. 184/1997) examines the probability and the severity of the main components of an environmental impact. The necessity of additional information regarding the risks related to the identified pollution or to the pollutant activities developed on a site may determine the


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environmental competent authority to request a risk assessment with the aim at evaluating the probability of harm and at finding the possible prejudiced entities. Not every site affected by a certain pollutant will exhibit the same risk or will need the same level of remediation. The risk assessment is defined by the World Bank as being a process for identification, analysis and control of the danger appeared due to the presence of a hazardous substance into a plant. The Report from 1992 of the British Royal Society explains the sense of the definition given in the Directive European Commission 93/67/EEC, enlightening the components of risk assessment, meaning the risk estimation and calculus.

In consequence, the risk assessment involves an estimation (including the identification of the hazards, the magnitude of the effects and the probability of occurrence) and a calculus of the risk (including the quantification of the danger importance and consequences for humans and/or environment).

Risk assessment aims at controlling the risks produced on a site by identification of:

• Pollutant agents or the most important hazards;

• Resources and receptors exposed to the risk; • Mechanisms of risk accomplishment; • Important risks that emerge on the site; • General measures needed for reduction of

the risk to an accepted level. The risk depends on the nature of impact

upon the receptors but also on the probability of the occurrence of this impact. Identification of the critical factors that influence the relationship source-path-receptor involves the detailed characterization of the site from physical and chemical point of views.

Generally, the quantitative risk assessment encloses five stages:

• description of the aim; • identification of the hazard; • identification of the consequences; • estimation of the magnitude of the

consequences; • estimation of the probabilities of the

consequences. Concordant to Order to 184/1997, the risk is the probability that a negative effect to occur in a specified period of time and is often described by the relation:

Risk = Danger x Exposure

The risk assessment implies the identification of the hazard and of consequences that may appear as a result of occurrence of the events considered as risk sources. In function of the importance of the consequences one may decide if there is necessary or not to take remediation measures. Concordant to the Order no. 184/1997, the risk quantification is based on a simple system of classification, where the probability and severity of an

event are descendent distributed, being assigned with an arbitrary score:

Simplified model

Probability Severity 3 = high 3 = major 2 = medium 2 = medium 1 = low 1 = insignificant

This model is used not only for qualitative, but also for quantitative risk assessment. Thus, the risk may be calculated by multiplying the two factors (probability, severity) in order to obtain a comparative number, for example 3 (high probability) x 2 (medium severity) = 6 (high risk). This allows the comparison of different risks.

The greater the results, the bigger the priority should be given to risk control. This basic technique may be developed for allowing more serious analysis by increasing the range of the scores for classification and by considering a bigger number of improved definitions for major severity, increased probability etc. When a big number of important pollutants are considered for assessment, an increased attention should be paid to a clearer manner of presentation. It is often necessary to summarize the information as a control list or matrix. 4. Quantitative risk analysis for port hydrocarbon logistics

4.1. Brief review

Over the last few decades much experience

has been gained in the field of risk analysis of standard chemical or petrochemical plants. Nowadays, this knowledge is being applied to a wide range of industrial activities involving hazardous materials handling, including ports (Crowl, 2002, Gavrilescu, 2003; Robu, 2005). Nevertheless, few works approached the application of QRA to navigational aspects and terminal operations are available, and this is to the role played by SEVESO II Directive. This method allows quantitative risk analysis (QRA) to be performed on marine hydrocarbon terminals sited in ports. A significant gap is identified in the technical literature on QRA for the handling of hazardous materials in harbors published prior to this work Ports are environments often overloaded with hazardous materials, both in bulk and containerized.

The method described here is proposed within a Spanish project called FLEXRIS and applied to the premises of the port of Barcelona, one of the largest ports on the Mediterranean Sea (Ronza et.al., 2006). Several risk assessment reports, made available to the public, proved to be a valuable source of information. What these works lack is an attempt at standardizing the process of risk assessment of navigation and loading operations for a generic port/terminal.


581

4.2. QRA – method description Only liquid hydrocarbons are considered in

this method. Moreover, only bulk transportation and handling are included within the scope of the research project mentioned above. The analysis covers port waters (from port entrance to berths) plus (un) loading terminals. Accidents occurring during the external approach of the tankers to the port are not take into account, nor are land accidents, such as those that can take place during storage and land transportation (within and outside the confines of the port). Finally, possible sabotage related scenarios and accidents likely to occur during tanker maintenance operations are excluded from this analysis. Instead, navigation through port waters and discharge are specifically addressed (Ronza et.al, 2006).

4.2.1. Data collection

The first step is to gather the relevant data that are used further during the analysis (Fig.1). This is a very important phase and ensuring that it is carried out properly can save great deal of time and avoid rough approximations. The data needed to be collected are (Ronza et.al., 2006):

• The geographical location of the port; • A detailed map of the port; • Climate data; • Technical data on berths and (un)loading

locations; • Physical and chemical data for the

hydrocarbon products taken into account; • Traffic data (critical for the calculation of the

frequency of accidents); • Duration of (un)loading operations; • Tanker hulls; • Data about the past accidents that above

occurred in the port involving hydrocarbons.

4.2.2. Scenario From a general point of view, only two basic events can cause a loss of containment during aforementioned operations: hull failure and loading arm/hose failure. For every loss of containment, two fold possibilities are considered:

• In the case of hull failure, a minor as well as a massive spill;

• For loading arms, partial and total rupture. In a general application, the number of

scenarios is as follows: Number of scenarios = 4n+2m

n being the number of hydrocarbons products traded and m the number of products bunkered (usually m=2, diesel oil and fuel oil being the bunkered fuels). 4.2.3. Frequency estimation

The approach was to estimate accident frequencies on the basis of both traffic data and general frequencies from literature. This method considered that the arm scenarios are of purely punctual natures, and hull ruptures are both punctual

and linear. The authors (Ronza et.al., 2006) made remark that in fact the latter nay be caused be any of the following: • An external impact (ship – ship or ship – land)

while the tanker is moving towards the berth or from the berth to the port entrance (linear option);

• By an external impact (ship – land) during maneuvers near the (un)loading berth or a ship – ship collision while the tanker is (dis)charging (punctual operations).

The dual nature must be taken into account because while the physical effects of the accident are practically the same, their consequences on people and installations may be different. Also, it is important to calculate separate the frequencies for punctual and linear scenarios. 4.2.4. Event tree analysis The next step is to draw proper event trees and assign numerical probabilities to each of their branches. It was drown only n event trees, n being the number of hydrocarbon products analyzed. The event tree from Fig. 2 was used by authors (Ronza et.al., 2006) in the application of the method to the Port of Barcelona. 4.2.5. Consequences analysis The phenomena or quantities used by authors in the consequences analysis, needed to be modeled are:

• Liquid release; • Evaporation rates • Burning rates • Pool fire radiation • Jet fire radiation • Cloud dispersion • Oil spill evaluation.

Individual risk was assessed using the

vulnerability correlations ((Ronza et.al., 2006). An additional criterion was adopted that is currently widely accepted: in the case of flash fires, 100% lethality was assumed for the area occupied by the portion of gas cloud in which the concentration is greater that the lower flammability limit, while outside that zone, lethality is assumed to be zero. 4.2.6. Estimation of the individual risk

The societal risk was estimated by building on the general procedures. The individual risk at a point (x, y) is expressed by the following equation:

∫ ∑= =

=π

θθ θθ

2

0

6

1)(),(),(

kkk dppyxfRFyxR (1)

where θ represents the wind direction, k stands for stability class, f is the accident frequency, RFkθ(x,y) the lethality function estimated on the basis of the vulnerability criteria, p(θ) the probability that the wind will blow in the direction θ and pk is the probability of the class of stability k.


582

Fig.1. Diagram of the QRA method (n = number of hydrocarbons products handled; m = number of hydrocarbon products bunkered) (Ronza et al., 2006)


583

Fig. 2. Event tree diagram

4.2.7. Estimation of overall risk for population By integrated the product of R by the local population density over spatial coordinates, the global risk for a given accident scenario is obtained. By adding up the several R functions (one of each scenario), a global risk function is obtained. In order to estimate the number of injuries and evacuated people, historical data were used. The average ratios of injured people/evacuees to fatalities have been estimated to the followings:

• 2.21 injured people for each fatality, • 220 evacuees for each fatality.

This data were obtained from processing of 1033 port area accidents from which only 428 occurred during bulk hydrocarbon (un)loading and tanker movement/maneuvers were retained.

The general ration should be used whenever the present QRA conceptual approach is applied to a port, because the scenarios, as they have been designed and structured, entail both (un)loading and ship maneuver/ approach operations. Nevertheless, the operation specific values can be used for studies that focus on a particular stage in port hydrocarbon logistics. 5. Mathematic models for environmental analysis and assessment

The modeling of the environmental systems is a very difficult problem owing to their complexity, as well to the complexity of their interaction with different other systems, interaction that is sometimes hard to be defined. In this paper, two environmental mathematic models are described.

The first is a probabilistic model for risk evaluation that uses a repartition function for a random vector that describes the concentrations of the atmospheric pollutant factors. The latter is an optimization model based on multiple criteria, to appropriate financial funds for pollution reduction. For the second model, the solving modality consists in reduction to an optimization problem with a single objective function.

Environmental protection against pollution is a priority not only for the European Union but also for the countries that wish to joint to EU, countries that make efforts for harmonization of the specific legislation. The community environmental policy is based on its integration within the EU sequential policies, paying a special attention to the measures for pollution prevention.

There are numerous concerns related to air, water and soil pollution generated by exceeding the limit concentrations of different pollutants, around the whole world. For pollution reduction there were conceived mathematic models by different complexities. Most of them refer to air, soil, water, air-water, air-soil, soil-water pollution. The main types of models are based on differential deterministic and stochastic equations (ordinary differential equations, equations with partial derivates), algebraic static equations, Petri networks, mathematic or stochastic programming, optimal control theory, Markov chains, Markov processes, Monte Carlo simulation and models based on mathematic equations (Radulescu, 2002). Environmental risk management is a relative new term in literature. This refers both to the risk and its effects diminishing measures.

Initiating event

Upward release

Immediate ignition

Delayed ignition

Flame front acceleration

Final events

Overall probabilities


584

It is very important to identify the risk and to estimate it in order to be analyzed. The risk analyzing process tries to identify all the results of an action. The risk estimation is done using the analytic methods or simulation. There are estimated thus the occurrence probability of every disaster, as well as the associated magnitude (dimension). The risk analysis process uses technical information related to estimations and other additional available information, for assessing diverse variants of possible actions. An original model based on multiple criteria optimization to appropriate financial funds for atmospheric pollution reduction is presented. For this model, the solving manner is specified by reduction to an optimization problem with a single objective function (Radulescu, 2002).

5.1. Measures for calculus of the risk value

The probability theory offers many adequate

tools for modeling the risk phenomenon. Any activity exhibits an incertitude element. From mathematical point of view, the incertitude will be modeled using random variables or, more generally, using the stochastic processes. The risk that appears within an activity may be described with adequate measures. One of the most used measures is the dispersion of the random variable, which describes the incertitude of the respective activity. Another measure of the risk is given by the repartition function of the random variable. More precisely, if X is a random variable that describes the risk associated to a decision, Fx is the repartition function associated to variable X, and fx is the probability density of the random variable X, then using Eq. (2):

== )(XEµ ( )∫+∞

∞−

xxdF , (2)

the risk measures result from Eqs. (3, 4):

∫+∞

∞−

−== )()()var( 22 xdFxX xµσ (3)

2/1

2 )()( ⎥⎦

⎤⎢⎣

⎡−= ∫

+∞

∞−

xdFx xµσ (4)

A measure of the risk may be considered also:

∫+∞

∞−

− )(|| xdFx xµ (first order central moment) (5)

Stone has shown that all the measures of the

risks above presented are special cases of some families of risks measures. The first measure of the risk within the Stone risk measures family that has three parameters is defined as (Eqs.2-6):

RS1(X) = ( )( )

∫∞−

−xFq

xk

x xdFFpx |)(| (k>0 (6)

where p\Fx) defines a level of the profit (success) that is used for measuring the abatement.

The positive number k is a measure of the relative impact of the small and big abatements. q(Fx) is a level a parameter that specifies the abatements will be included in the risk measurement. The second measure of the risk within Stone family with three parameters is defined as k order root from RS1 (X) (Eq. 7):

RS2(X) = kFq

xk

x

x

xdFFpx

1)(

)(|)(|⎥⎥⎦

⎤

⎢⎢⎣

⎡⋅−∫

∞−

(7)

One may observe that through proper

selection of the parameters p(FX), qFx) and k, the above presented risk measurement are special cases of those from the Stone family of risk measurements.

For example, if in (l) k = 2 and p(Fx ) = (Fx ) = µ are inserted, the semi-dispersion is obtained as a measure of the risk. A more interesting case related to risk measures Stone family is the generalized risk measure Eq. (8):

RF1(X) = ∫∞−

t

(t - x)α dFx (x) (α > 0), (8)

proposed by Fishburn, where t is a superior scope-level that is fixed. This measure results from (l) if one choose p(Fx)=q(FX ) = t. The parameter “a” of Fishburn risk measurement RF1 may be interpreted as “k” parameter from the measures Stone family (l) in this way: it is a risk parameter, which characterizes the attitude toward risk. The values α > l describe a sensitive risk, while the values α ∈ (0. l) describe an insensitive risk. Another known measure of the risk is Shannon entropy (Eq. 9):

∫+∞

∞−

dxxfxfx x ))(ln()( (9)

5.2. Probabilistic modeling of pollution

Mathematic modeling of air pollution is

done using the theory of stochastic processes. Thus, over long periods of time, the pollution degree may be described by a multidimensional stochastic process: X = (Xt)t 0≥ . For t≥ 0 attached to the components of the random vector: Xt = (Xl,t ; X2,t...Xm,t) represents the concentrations of the atmospheric pollutant factors. Repartition function of the stochastic multidimensional process X, F(t,x) =


585

Fxt(x) = P(X1,t<x1 X2t < x2,...,Xm,t <xm = P(ω ЄΩ:X1,t (ω) < x1, X2,t (ω) < x2,.......,Xm,1 (ω) < xm ), t∈R, x = (x1, x2,...,xm) ∈Rm, is essential for describing the pollution risks.

In practice, one may use the construction of the empiric repartition function of the studied stochastic process. This can be done on the basis of the historical data concerning the concentration in atmosphere of the pollutants factors. With the empiric repartition function, one may estimate the possible risk of being exceeded different limits of the levels of atmospheric concentrations of the pollutants factors. Are particularly interesting the warning levels, as well the admissible ones. 5.4. Advantages and disadvantages

The researches presented are framed within

the international efforts for meeting and removal of the facts related to environmental risk with negative effects on socio-economic activities and on environment, as well. In this paper, some original models for air pollution prevention were described (Radulescu, 2002). These follow to be integrated in software that will constitute a support system for the environmental decisions and encloses a library with environmental risk models. The support system for environmental risk analysis and assessment will combine the information originated from different sources, such as one to be able to take decisions on the basis of its processing. Considering as models some scenarios concerning the possible risk degrees of disasters occurrence, the resulted damages, as well as their costs would be calculated. This decision support system underlies the basis of policy implementation suggesting actions that may be performed or establishing the priorities of some fields where measures can be taken. There are information concerning the history of the environmental data in environmental institutes and research centers from our country. The necessary current and historical data will be gathered through collaboration with specialized entities, being constituted a necessary data basis for the environmental risk analysis and assessment software. There are also foreseen some simulations that will contribute to enforcement of the environmental decisions (Radulescu, 2002).

6. Probabilistic modeling methods applied in risk assessment 6.1. General expressions for probability of fault occurrence

The reliability of an engineering system may be defined as its ability to comply with the purpose it was designed for a period of time, hence, as the probability to achieve a utilization function in specific conditions of use for a well defined period. Two main categories of methods (techniques) for estimation of the probability of fault occurrence exits, such as: methods random and analytic methods. The

first includes a large class of information random sampling methods characterized by random selection and control of each parameter of the system. This category is dominated by the Monte Carlo traditional methods, but also by other derived methods as Latin Hypercube Sampling (LHS), Iterative Monte Carlo Simulation (IMCS), Important Data Sampling (IS), Adaptive Important Data Sampling (AIS) and Robust Important Data Sampling Method (RISM).

The Monte Carlo methods have a long history in reliability and incertitude analysis as integrator of functions. These methods often need processing through difficult and sometimes prohibitive calculus especially, for the reduced fault probabilities although the number of simulations is independent by the number of basic variables. The last methods are characterized by using some analytic techniques in order to find a particular point in the design space that may be related, least approximately, to the system probability. This point is often considered as being the most probable point (MPP) or design point.

The First Order Reliability Method (FORM) is widely used in reliability analysis due to its simplicity and reduced time for application. The Second Order Reliability Method (SORM) may enhance the estimation of the reliability for linear problems. Moreover, for problems with a big number of random and implicit state limits, each of the FORM or SORM procedures will need more functions, hence methods based on computer simulation or Advanced Second Moment (ASM) type methods were developed. The goals of estimation of the fault occurrence probability are: development of the concept of state function limit, characterization of a system response incertitude caused by the existent incertitude in system internal parameters and response sensitivity analysis for a system to the incertitude of the system variables.

6.2. Advantages and disadvantages

The paper presents some selection and probabilistic methods for risk assessment, particularly for risks related to the emissions of the pollutants gas originated from a source. The sensitive analysis is also presented as a key factor that may have a significant impact in risk assessment. This example is not a very critical one, but in industrial processes critical situations exist. The study can offer an increased reliability and confidence in prediction of the safety states.

The enhanced values of the safety factor lead to lower values of the risk, some approaches as the current one, resulting in minimizing the need of excessive safety borders in design and in reducing the expensive analytic and experimental approaches.

The method can be used for prediction of the limit state in risk or for estimation of fault occurrence probability in reliability analysis. These types of studies that lead to consistent conclusions regarding the functioning of the technological plants are not


586

only recommended but also necessary for engineers, particularly for the chemical engineers that analysis and manage the risk for taking the optimum decisions on safety.

7. Integrated environmental impact and risk assessment 7.1. Short introduction

Environmental impacts and risks can be

assessed applying different method as diagrams, check lists, matrix or combined methods (Gavrilescu, 2003; Macoveanu, 2005). The method to evaluate the environmental impact and risk described herein is a combination between tow methods: global pollution index, matrix of importance scale (Robu, 2005; Robu and Macoveanu, 2005b). An algorithm developed as software designated as SAB was applied to automatically quantify the environmental impacts and risks that arise from an evaluated activity, considering the measured concentration, levels of quality indicators. Also, the new method considered the principles of environmental impact from method of importance matrix, from which the term importance of environmental component and the way of its quantification were assumed.

The environmental evaluation system is divided into estimation and quantification of environmental impacts in terms of measurable units, in this case as environmental importance units (IU). The environmental scores obtained in environmental impact assessments are basely composed from two parameters: the magnitude of environmental impacts and the importance.

The quality (Q) of environmental component is quantified as the ration between the maximal allowed concentration concordant to national legislation and the measured concentration of pollutants. If this parameter Q has values close or higher than 1, then the environmental component has a good quality, if this parameter has values close to 0, then the quality of environmental component is very poor. The values of quality indicators that are considered representative for characterization of environmental components in evaluation process have to be according with national standards, under the maximal allowed concentration.

When the measured values of quality indicators are equal or about with values of alert level (70% from maximal allowed concentration), then there is certain stress, that could be a possible impact, a hazard on quality of environmental component, hazard that can become a risk, if no pollution prevention measures are taken. 7.2. Method description

The fact that the environmental impact

assessments have a great subjectivity, the environmental specialists (Callow, 1998; Macoveanu, 2005; Robu, 2005) considered that is an acute need to

use various methods, statistical techniques in order to minimize this subjectivity. The method SAB is settled up to evaluate the environmental impact and risk, considering the main environmental components: surface water, ground water, air and soil. To characterize the quality of environment, the specific quality indicators for each environmental components considered in evaluation process, were taken into account. It was also considered the specific of activity, installation, equipment assessed.

This new method for integrated environmental impact and risk assessment (EIRA) can be applied for different activities, various industrial installation, processes, industrial sites and other related activities which are performed on. Considering the following environmental components: ground and surface water, soil and air, the evaluation of environmental impacts is done using a matrix in order to calculate the importance of each environmental component, potentially affected by the industrial activities.

The importance parameter can take values between 0 and 1; value 1 represents the most important environmental component (Goyal and Deshpande, 2001). These values are assigned by the evaluator to each environmental component. Then, the matrix calculates the importance units (IU) for ground and surface water, soil and air (Table 1). An example is given in Table 2.

The impact on environmental component (EI) directly depends on measured concentration of pollutants, and it is expressed as the ratio between importance units (IU) and quality of environmental component (EQ), defined as follows (Eq. 10):

MACCIU

QIUEI measured⋅

== (10)

Table 1. The calculation of importance units for environmental components

Environmental component

Surface water (l)

Ground water (m)

Soil (n)

Air (o)

Surface water (l)

0.90 1.13 = (1/m)

0.95 = (l/n)

0.90 = (l/o)

Ground water (m)

0.80 1.00 = (m/m)

0.84 = (m/l)

0.80 = (m/o)

Soil (n) 0.95 1.19 = (n/m)

1.00 = (n/n)

0.95 = (n/o)

Air (o) 1.00 1.25 = (o/m)

1.05 = (o/n)

1.00 = (o/o)

l – importance value for surface water, m – importance value for ground water, n – importance value for soil, o – importance value for air

The parameter quality of environmental

component (Q) is defined as follows (Eq.11):

measuredCMACQ = (11)


587

where: MAC – maximal allowed concentration of quality indicators; Cmeasured – measured concentration of quality indicators.

Table 2. Importance units obtained by solving the matrix from Table 1


Normalized weights Importance units (IU = NWx1000)

Surface water (l)

0.27 = 1/(0.9+0.8+0.95+1.0)

273.97

Ground water (m)

0.22 = 1/(1.13+1.0+1.19+1.25)

219.18

Soil (n) 0.26 = 1/(0.95+0.84+1.0+1.05)

260.27

Air (o) 0.27 = 1/(0.9+0.8+0.95+1.0)

273.97

After the calculation of importance units, the

next step was to calculate the quality of each environmental component defined above. If the quality parameter of environmental component is equal with 0, it results that the environmental quality is very poor (this means that the measured concentration of pollutant is very high); if EQ value is close to 1, or higher than 1, then the quality of environmental component is very good (Goyal and Deshpande, 2001). The impact on surface water (EIsw) is given by the following equations (Eqs.12-14):

sw

swsw Q

IUEI = (12)

n

EIEI

n

iisw

sw

∑== 1

)( (13)

imeasured

iisw C

MACQ =)( (14)

EI(sw)i – environmental impact on surface water, considering quality indicator i; i – quality indicators (e.g. COD-Cr, BOD etc.); EQ(sw)i – quality of surface water, considering the quality indicator i; IUsw – importance units obtained by surface water; MACi – maximal allowed concentration for quality indicator i; Cmeasured i – measured concentration for quality indicator i.

It can be observed that the global impact on environmental component j is the average of the impacts considering the quality indicators i. Thus, the impact on ground water (EIgw), air (EIa) and soil (EIs) are quantified in the same way (Eqs.15-20).

n

EIEI

n

iigw

gw

∑== 1

)( (15)

gw

gwgw Q

IUEI = (16)

EQ(gw)i – quality of environmental component ground water, considering the quality indicator i; IUgw – importance units obtained by ground water.

n

EIEI

n

iia

a

∑== 1

)( (17)

a

aa Q

IUEI = (18)

EQ(a)i – quality of environmental component air, considering the quality indicator i; IUa – importance units obtained by air.

n

EIEI

n

iis

s

∑== 1

)( (19)

s

ss Q

IUEI = (20)

EQ(s)i – quality of environmental component soil, considering the quality indicator i; IUs – importance units obtained by soil.

Table 3. The calculation of probability

Environm comp.

Surface water (l)

Ground water (m)

Soil (n) Air (o)

Surface water (l)

0.90 1.13 = (1/m) 0.95 = (l/n)

0.90 = (l/o)

Ground water (m)

0.80 1.00 = (m/m) 0.84 = (m/l)

0.80 = (m/o)

Soil (n) 0.95 1.19 = (n/m) 1.00 = (n/n)

0.95 = (n/o)

Air (o) 1.00 1.25 = (o/m) 1.05 = (o/n)

1.00 = (o/o)

Table 4. The probability units


Probability units

Surface water (l) 0.27 = 1/(0.9+0.8+0.95+1.0) Ground water (m) 0.22 = 1/(1.13+1.0+1.19+1.25) Soil (n) 0.26 = 1/(0.95+0.84+1.0+1.05) Air (o) 0.27 = 1/(0.9+0.8+0.95+1.0)

This way the impacts for each environmental

component considered representative for the evaluated situation were calculated. The next step was


588

to quantify the risks that arise from the activities considered, in the view of the results for environmental impacts. The risks are calculated follows (Eq.21):

j j jRM IM P= ⋅ (21) ERj – environmental risk for environmental component j; EIj – environmental impact on environmental component j; Pj – probability of occurrence of impact on environmental component j.

The probability of impact occurrence was calculated using the same matrix as described above (Table 1) to calculate the importance units. The normalized weights are presented in Table 4. The evaluator has to give values between 0 and 1 for probability (Table 3), which is detailed in Table 5 (Pearce, 1999).

7.3. Advantages and disadvantages

The data automatically performed by the SAB soft are presented in Table 6, and Fig. 3 present environmental impacts and risks.

It has to be emphasized that if the impact

and risk have very high values, then the impact induced by the considered activities on the environment is great and the environmental risks are at an unacceptable level (major/catastrophic risks).

High values for environmental impacts and risks underlay the presence of pollutants in environment in very high concentrations, because impact directly depends on the measured concentration of pollutants. Considering the impact classification from method of global pollution index, a classification of impacts and risks is proposed (Table 7).

This new method has the advantages that it is very easy to be used by non environmental experts; it calculates the impacts and risks, correlated with measured concentrations of quality indicators for environmental component, considered representative in assessment process; it is not a subjective method because the subjectivity is removed applying mathematical steps (the developed soft - SAB).

Also, the lack of experience of evaluator doesn’t influence the evaluation results that will reflect the real situation from the evaluated site, where the industrial activities are performed.

Table 5. Description of probability

Probability Description Probability units Almost certain Is expected to occur in most circumstances (99%) 0.91-1.0 Likely Will probably occur in most circumstances (90%) 0.61-0.9 Possible Might occur at some times (50%) 0.31-0.6 Unlikely Could occur at some times (10%) 0.05-0.3 Rare May occur only in exceptional circumstances (1%) <0.05

Table 6. The calculation of environmental quality, impact and risk

Environmental component Quality indicator MAC1 C2measured EQ3 EI4 ER5

COD-Mn, mg O2/l 10 14.11 0.71 386.58 115.40 BOD5, mg/L 5 3.20 1.56 175.34 52.34 Surface water Ammonium, mg/L 0.3 0.8 0.38 730.59 218.09 COD-Mn, mgO2/L 5.00 2.20 2.27 96.44 18.71 COD-Cr, mgO2/L 10.00 6.00 1.67 131.51 25.52 NO3

-,mg/L 50.00 81.60 0.61 357.70 69.40 Ammonium, mg/L 0.50 0.06 8.33 26.30 5.10 NO2

-, mg/L 0.50 1.14 0.44 499.73 96.96 P, mg/L 0.10 0.010 10.00 21.92 4.25 SO4

-2, mg/L 250.00 58.00 4.31 50.85 9.87 Cl-, mg/L 250.00 78.00 3.21 68.38 13.27

Ground water

Residues, mg/L 500 789.00 0.63 345.86 67.11 NOx mg/mc 0.2 0.07 2.86 95.89 27.19 VOCs mg/mc 50 780 0.06 4273.97 1212.02 SOx, mg/mc 0.35 0.08 4.38 62.62 17.76 Air

Dust (d>10 µm), mg/mc 0.05 0.28 0.18 1534.25 435.08 Soil Extractable compounds, mg/kg 2000 10480 0.19 1363.84 407.12 1 - maximal allowed concentration according to Romanian legislation; 2 – measured concentrations of quality indicators, 3 – environmental quality; 4 – environmental impact, 5 – environmental risk.


589

430.84

128.61177.63

34.47

1363.84

407.12

1491.68

423.01

0.00

200.00

400.00

600.00

800.00

1000.00

1200.00

1400.00

1600.00

Surface water Ground water Soil Air

Environmental impact Environmental risk Fig.3. Environmental impacts and risks

Table 7. Classification of environmental impact and risk

Impact Scale

Description Risk Scale

Description

<100 Natural environment, not affected by industrial/human activities

<100

Negligible/insignificant risks

100-350 Environment modified by industrial activities within admissible limits

100-200

Minor risks, monitoring actions are required

350-500 Environment modified by industrial activities causing discomfort conditions

200-350

Moderate risk at an acceptable level, monitoring and prevention actions are required

500-700 Environment modified by industrial activities causing distress to life forms

350-700

Moderate risks at an unacceptable level, control and prevention measures are needed

700-1000 Environment modified by industrial activities, dangerous for life forms

700-1000

Major risks, remediation, control and prevention measures are needed

>1000 Degraded environment, not proper for life forms

>1000 Catastrophic risks, all activities should be stopped

8. Conclusions

The aim of this work was to present the main

procedures, methods, models and approaches, generally used in environmental risk assessment. Thus, the common notion of risk is associated with

actions or decisions that may have undesired to outcome. This implies that the risk-based approaches focus on the negative impacts and their prevention. Risk assessment places the emphasis on the potential negative environmental impacts of an organization’s activities and allows the identification of indicators that directly reflect its efforts, efficiency and effectiveness in reducing or even preventing them. The environmental risk is the result of the interactions between the human activities and the environment. The ecologic risk management that refers to the problematic of the risks generated by the past, present and future human activities on flora, fauna and ecosystems constitutes only a part of the environmental risk management. Risk assessment is one of the steps of the general risk management procedure.

Risk management is a technique used to identify, characterize, quantify, evaluate and reduce losses from actions or decisions that may have undesired outcomes. The first step of the generic procedure involves the risk identification that is the systematic identification of all potential actions or decisions with undesired consequences that may result from the operation of an organization. The next step involves the risk assessment, while further steps address issues like the evaluation of risks in order to determine the organizations ability or willingness to tolerate their consequences in view of the associated benefits, and the selection and implementation of the most preferable approach for the reduction of unacceptable risks.

The problems concerning the work safety and health as well as the risk management in emergency situation may be significant from the environmental risk point of view. The environmental risk management provides a formal set of processes that constitutes the fundament for environmental decision making and support the decision factor in the steps of incertitude level minimization.

Qualitative risk analyses consist in: control lists, integral inspections of the industrial units, ranking, preliminary hazard analysis (PHA), what if method and HAZOP method (hazard operation), while quantitative risk analyses, usually are done using: hazard analysis (HAZAN), event tree analysis, fault tree analysis. In Romania the qualitative and quantitative environmental risk assessment is made concordant to Ministerial Order no. 184/1997, and examines the probability and the severity of the main components of an environmental impact. The necessity of additional information regarding the risks related to the identified pollution or to the pollutant activities developed on a site may determine the environmental competent authority to request a risk assessment with the aim of evaluating the probability of harm and of finding the possible prejudiced entities. Not every site affected by a certain pollutant will exhibit the same risk or will need the same level of remediation.


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In consequence, the risk assessment involves an estimation (including the identification of the hazards, the magnitude of the effects and the probability of occurrence) and a calculus of the risk (including the quantification of the danger importance and consequences for humans and/or environment). Risk assessment aims at controlling the risks produced on a site by identification of: pollutant agents or the most important hazards; resources and receptors exposed to the risk; mechanisms of risk accomplishment; important risks that emerge on the site; general measures needed for reduction of the risk to an accepted level. The risk depends on the nature of impact upon the receptors but also on the probability of the occurrence of this impact. Identification of the critical factors that influence the relationship source-path-receptor involves the detailed characterization of the site from physical and chemical point of views.

Also, this paper briefly described a quantitative risk analysis for port hydrocarbon logistics, proposed by Ronza A. et.al, 2006, which consists in the following steps: data collection, scenarios identification, frequency estimation, event tree analysis, consequences analysis, individual risk estimation and the estimation of global risk for population. Mathematic models for environmental analysis and assessment are described too. The modeling of the environmental systems is a very difficult problem owing to their complexity, as well to the complexity of their interaction with different other systems, interaction that is sometimes hard to be defined.

In this paper, two environmental mathematic models were described. The first, probabilistic model for risk evaluation uses a repartition function for a random vector that describes the concentrations of the atmospheric pollutant factors. The latter, an optimization model is based on multiple criteria, to appropriate financial funds for pollution reduction. For the second model, the solving modality consists in reduction to an optimization problem with a single objective function.

The paper presents some selection and probabilistic methods for risk assessment, particularly for risks related to the emissions of the pollutants gas originated from a source. The sensitive analysis is also presented as a key factor that may have a significant impact in risk assessment. This example is not a very critical one, but in industrial processes critical situations exist. The study can offer an increased reliability and confidence in prediction of the safety states. The enhanced values of the safety factor lead to lower values of the risk, some approaches as the current one, resulting in minimizing the need of excessive safety borders in design and in reducing the expensive analytic and experimental approaches.

The method can be used for prediction of the limit state in risk or for estimation of fault occurrence probability in reliability analysis. These types of studies that lead to consistent conclusions regarding

the functioning of the technological plants are not only recommended but also necessary for engineers, particularly for the chemical engineers that analysis and manage the risk for taking the optimum decisions on safety.

Lately, the trend is to integrate the environmental risk principle into impact assessment procedure, or to base risk assessment on life cycle assessment. Thus, the method SAB, described herein is settled up to evaluate the environmental impact and risk, considering the main environmental components: surface water, ground water, air and soil. To characterize the quality of environment, the specific quality indicators for each environmental components considered in evaluation process, were taken into account. It was also considered the specific of activity, installation, equipment assessed. This new method for integrated environmental impact and risk assessment (EIRA) can be applied for different activities, various industrial installation, processes, industrial sites and other related activities which are performed on. Considering the following environmental components: ground and surface water, soil and air, the evaluation of environmental impacts is done using a matrix in order to calculate the importance of each environmental component, potentially affected by the industrial activities.

Concordant to this new method, the impact on environmental component directly depends on pollutants concentration into environment. This way, the impacts for each environmental component considered representative for the evaluated situation were calculated. The next step is the quantification of risks that arise from the activities considered, in the view of the results for environmental impacts.

It has to be emphasized that if the impact and risk have very high values, then the impact induced by the considered activities on the environment is great and the environmental risks are at an unacceptable level (major/catastrophic risks). High values for environmental impacts and risks underlay the presence of pollutants in environment in very high concentrations, because impact directly depends on the measured concentration of pollutants. Considering the impact classification from method of global pollution index, a classification of impacts and risks is proposed.

This new method has the advantages that it is very easy to be used by non environmental experts; it calculates the impacts and risks, correlated with measured concentrations of quality indicators for environmental component, considered representative in assessment process; it is not a subjective method because the subjectivity is removed applying mathematical steps (the developed soft - SAB). Also, the lack of experience of evaluator doesn’t influence the evaluation results that will reflect the real situation from the evaluated site, where the industrial activities are performed.


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Acknowledgement

This work was supported by the Program IDEI, Grant ID_595, Contract No. 132/2007, in the frame of the National Program for Research, Development and Innovation II - Ministry of Education and Research, Romania. References Andrews R.N., (1988), Environmental risk assessment and

risk assessment: learning from each other. Environmental Impact Assessment: Theory and Practice, Routledge, NY, USA.

AICE, (1992), Guidelines for Hazard Evaluation Procedures, American Institute of Chemical Engineers 2nd edition, USA.

Aven T., Kristensen, V. (2005), Perspectives on risk: review and discussion of the basis for establishing an unified and holistic approach, Reliability Engineering and System Safety, 90, 1-14.

Barrow C., (1997), Environmental and social impact assessment. An Introduction, Oxford University Press, Oxford.

Calow P., (1998), Environmental Risk Assessment and Management: the What’s, Why’s and How’s?;’ In: Calow J. (ed.), Handbook of Environmental Risk Assessment and Management, Blackwell Science Ltd., Oxford, pp. 5.

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Crawley F., (2000), HAZOP: Guide to Best Practice for the Process and Chemical Industries, 1st Ed., London, UK.

Crowl D. A, (2002), Chemical Process Safety: Fundamentals with Applications, 2nd edition, London, UK.

Cooke, M.R.: 1991, Experts in Uncertainty. Opinion and Subjective Probability in Science, Oxford University Press, New York, 15– 50 pp.

Demidova O., (2002), Use of risk assessment in environmental impact assessment for projects with significant health implications: case studies of UK waste incineration developments, Master thesis, Environmental Sciences and Policy Dept., CEEC University, Budapest.

Den Haag U., Di Ale B., Uitgerers S., (1999), Guidelines for Quantitative Risk Assessment, Purple Book, Committee for the Prevention of Disasters (CPD), Bilthoven.

Gavrilescu M., (2003), Risk Assessment and Management, Ecozone Press, Iasi, Romania.

Goyal S.K., Deshpande V.A., (2001), Comparison of weight assignment procedures in evaluation of environmental impacts, Environmental Impact Assessment Review, 21, 553-563.

Jaeger C., (1998), Risk management and integrated assessment, Env. Modell. Assess., 3, 211-225.

Hokstad P., Steiro T., (2006), Overall strategy for risk evaluation and priority setting of risk regulations, Reliability Engineering and System Safety, 91, 3575-3586.

Karrer-Ruedi E., (1998), Environmental Management

Systems and Standards, Swiss Re America, New York, NY.

Khan F.I., Haddara M.M., (2003), Risk-based maintenance (RBM): a quantitative approach for maintenance/inspection scheduling and planning”, Journal of Loss Prevention in the Process Industries, 16, 561-73.

Kolluru R., Bartell S., Pitblado R., Stricoff S., (1996), Risk Assessment and Management Handbook: for Environmental, Health and Safety Professionals, McGraw-Hill, New York, NY.

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Macoveanu M., (2005), Methods and Techniques for Environmental Impact Assessment, 2nd Edition, Ecozone Press, Iasi, Romania.

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Negrei C., (1999), Tools and methods for environmental engineering, Economic Press, Bucharest.

O’Connor M., Splash C.L., (1999), Introduction, In: O’Connor M., Splash C.L. (Eds.), Valuation and the Environment Theory, method and practice. Advances in Ecological Economics, Edward Elgar, Cheltenham, pp. 1–35.

Pearce F., (1999), Rivers of Doubt, New Scientist, London, UK.

Petruc V., Robu B., Macoveanu M., (2006), Prediction and quantification of environmental impact and risk for sand blasting and varnishing processes, Proc. of 6th International Congress Of Chemistry, Chemistry And Sustainable Development, Puerto de la Cruz, December 2006, Tenerife, Spain, vol. 2, pg.697, ISBN 84-690-2349-7

Radulescu C.Z., (2002), Mathematical models for environmental risk evaluation and analysis (in Romanian), Romanian Journal of Informatics and Automatics Bucharest, 12, 30-35.

Robu B., (2005), Environmental impact and risk assessment for industrial activities, PhD Thesis, Technical University of Iasi, Ecozone Press, Iasi, Romania.

Robu B., Macoveanu M., (2005a), Integration of risk assessment into environmental impact assessment procedure – case study for steel processing, Proc. of the 9th Int. Conf. on Environmental Science and Technology Rhodes, September 2005, Rhodes Greece.

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Robu B., Macoveanu M., (2005c), Integrated method for environmental impact and risk assessment – case study for a shipyard, Ecological Journal BENA, Greece.

Robu B., Petruc V., Macoveanu M., (2006a), Assessment of the impact induced on environment by oil distribution, Scientific Journal of „Al. I. Cuza” University from Iasi, Chemistry series, Tom XIV, No. 1, January-June 2006, p 117-128.

Robu B., Petruc V., Macoveanu M., (2006b), Comparative evaluation of impact induced in environment by a refinery, Environmental Engineering and Management Journal, Iasi, 5, 457-471.


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Robu B., Bulgariu L., Bulgariu D., Macoveanu M., (2007), Environmental impact and risk quantification of minerals and heavy metals presence in surface water: Case study – Bahlui River, Iasi, Proceedings of International Conference on Chemistry and Chemical Engineering (RICCCE), Bucharest, Revue Roumaine de Chimie, in press.

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***http://www.uneptie.org/pc/pc/tools/pdfs/EIA2-rpt.pdf



______________________________________________________________________________________________

COMPARATIVE STUDY OF SOME ESSENTIAL ELEMENTS IN

DIFFERENT TYPES OF VEGETABLES AND FRUITS

Alina Soceanu1∗, Simona Dobrinas1, Viorica Popescu1, Semaghiul Birghila1, Vasile Magearu2

1 Ovidius University of Constanta, Department of Chemistry, 124 Mamaia Blvd, 900527 Constanta, Romania

2 Bucharest University, Department of Analytical Chemistry, 4-12 Elisabeta Blvd., 030018, Bucharest, Romania

Abstract Some industry activities in the area of Constanta (Romania) contribute to the polluting of the environment with heavy metals. In order to estimate the pollution level and the danger created by this phenomenon, some analyses are required with regard to determining the concentration of the pollutant metals in plants samples. The investigated metals were determined by flame atomic absorbtion spectrometry in different types of vegetables and fruits, after the chemical mineralization of the sample with a Digesdahl device. These levels were compared with those from literature. Key words: metals Fe, Mn, Cd, Zn, Cu, FAAS, pollutants vegetables, fruits


1. Introduction

The concentration of heavy metals in the soil is an important issue with regards to human health. Ingestion of vegetables grown in contaminated soil may pose health issues. The accumulation of metals varies greatly both between species and cultivars. Heavy metals are not readily absorbed by plants. Generally, plants translocate larger quantities of metals to their leaves than to their fruits or seeds.

For the determinations of metals in plants various techniques were used, such as total reflection X-ray fluorescence spectrometry (TXRF) (Varga et al., 1999), X-ray fluorescence spectrometry (Psaras and Manetas, 2001; Belakova et al., 1998), flame atomic absorption spectrometry (Moraghan et al., 2002; Beebe et al, 2000), inductively coupled plasma atomic emission spectrometry (Perronnetk at al., 2003; Masson, 1999), inductively coupled plasma mass spectrometry (Ivanova et al., 2001; Li et al., 1998).

Flame atomic absorption spectrometry (FAAS) is probably the most widely used technique for analyzing a variety of metals in food due to its

relatively low cost and excellent analytical performances. In this study, samples of vegetables (bean, pea, carrot, cucumber) and fruits (peach and nectarine) produced in the area of Constanta (Romania) were analyzed to determine their content in Fe, Mn, Cd, Zn and Cu by flame atomic absorption spectrometry (FAAS) and compared with those obtained by other authors.

2. Experimental

2.1. Reagents and solutions

All metal stock solutions (1000 mg/L) were

prepared by dissolving the appropriate amounts of the metals or compounds in dilute acids (1:1) and then diluting them with deionised water. The working solutions were prepared by diluting the stock solutions to appropriate volumes. The nitric acid and hydrogen peroxide solutions used were of analytical grade, purchased from Merck.


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2.2. Sample preparation

The vegetables and fruits samples produced in the area of Constanta (Romania) were collected during one year. These samples were stored in Teflon vessels at the room temperature in a dark place for further analysis.

A mineralization step is necessary to obtain a finally solution suitable for introduction in the spectrometer. This step is recommended even for liquid or water-soluble foodstuffs, the destruction of the organic matter preventing both spectral interferences and the accumulation of the residues in the burner head and spray chamber. In this context analyzed samples were submitted to digestion with 8 mL HNO3 and 10 mL H2O2 at 150oC in a Digesdhal device provided by Hach Company. After the complete digestion, sample solutions were filtered made up to 50 mL with deionized water. Than Fe, Mn, Mg and Zn were determined by FAAS in air/acetylene flame using an aqueous standard calibration curve. Analyses were made in triplicates and the mean values are reported.

A flame atomic absorption spectrometer Shimadzu AA6500 was used for the determination of five essential elements (Fe, Mn, Cd, Zn and Cu). An air-acetylene flame was used for all elements. Monoelement hollow cathode lamps were employed to measure the elements. The acetylene was of 99.999% purity at a flow rate 1.8-2.0 L/min. The characteristics of metal calibration are presented in Table 1.

Table 1. Characteristics of metal calibration curves

Metal λ, nm Concentration range (ppm)

Correlation coefficient

Fe 248.3 0.020-4.000 0.9976 Mn 279.5 0.008-1.600 0.9984 Cd 228.8 0.008–1.600 0.9999 Zn 213.9 0.016-0.510 0.9932 Cu 324.7 0.010–1.200 0.9990

The accuracy (expressed as standard deviation

SD and coefficient of variance CV) of the results was determined from three replicates of homogenized samples, giving a good standard and precision for the analytical results of essential elements obtained by FAAS. 3. Result and discussion

In Tables 2 and 3 the average values of Fe,

Mn, Zn, Cd and Cu concentrations in vegetable samples (mg/kg) are presented. Concentrations of iron found in the bulb of carrot (825.51 mg/kg), in stem (506.03 mg/kg) and in leaves (1207.18 mg/kg) of cucumber were over the allowable maximum limit of iron in vegetables namely 425.5 mg/kg (Food Standards Programme, 2001).

It can be observed that iron concentrations are higher in the leaves of bean and pea plant comparative to the others parts of these plants. Also,

the content of iron is higher in the bean than in the pea. The plants absorb cadmium through their roots and leaves, which affect the plant metabolism and growth. The highest concentrations of cadmium in polluted plants are always reported for the leaves. The bean and pea leaves studied here indicate that levels of cadmium are lower than those measured by Angelova in bean, respectively pea leaves (6.4 mg/kg, respectively 1.13 mg/kg) (Angelova et al., 2003). They found that the movement and accumulation of the heavy metals (Cu, Cd and Zn) in the vegetative organs of different cultivated plants differed significantly. They also found that the content of heavy metals in the leaves was higher comparative to the root system.

This situation is confirmed by the studies of Cobb et al., (2000) about the accumulation of cadmium, lead, zinc and copper in different vegetables, which indicate that each plant can accumulate differently heavy metal. Moraghan studied the accumulation of iron in beans (Moraghan et al, 2002). He determined the influence of lime, Fe chelates and type of soil on accumulation of iron in bean. In this context, he observed that iron chelates could drastically reduce Mn concentration.

Table 2. Fe and Cd concentrations in vegetables

Concentrations (mg/kg) Sample

Fe Cd

Green pod 50.48±0.0032 1.97±0.0012 Leaves 217.77±0.0064 3.73±0.0012 Flower 188.93±0.004 10.71±0.0025

Bean (Phaseolus vulgaris L)

Bean 38.52±0.0025 3.3±0.0016 Pod 31.6±0.0011 2.81±0.0006

Leaves 153.55±0.0021 4.13±0.0025 Pea

(Pisum sativum L) Pea 41.93±0.003 1.09±0.043

Bulb 825.51±0.0278 3.391±0.0024 Carrot (Daucus carota L) Leaves 249.3±0.0025 5.73±0.0017

Root 351.23±0.0027 47.03±0.0215

Stem 506.03±0.0001 61.32±0.0025

Leaves 1207.18±0.0022 <LD

Cucumber (Cucumis sativus L)

Cucumber 91.41±0.0029 <LD

Table 3. Mn, Zn and Cu concentrations in vegetables


Mn Zn Cu

Green pod 16.52±0.001 3.24±0.0020 10.87 Leaves 10.65±0.0004 13.62±0.0008 21.83 Flower < LD 3.62±0.0035 < LD

Bean (Phaseolus vulgaris L)

Bean 6.98±0.0003 8.9±0.0037 9.81 Pod 5.43±0.0014 < LD 19.82

Leaves 29.62±0.0011 < LD 9.41 Pea

(Pisum sativum L) Pea 1.38±0.0014 12.47±0.0035 7.24

Bulb 24.85±0.0005 31.98±0,0214 ND Carrot (Daucus carota L)

Leaves 13.06±0.0029 26.54±0.0057 157.84±0.0005

Root 8.47±0.0359 220.19±0.0175 <LD Stem 10.11±0.0018 <LD 27.31±0.0002

Leaves 19.35±0.0001 416.25±0.0029 53.26±0.0004

Cucumber (Cucumis sativus L)

Cucumber 7.30±0.0022 2.94±0.002 0.281±0.0007

Comparative study of some essential elements in different types of vegetables and fruits

595

Tables 4 and 5 present the average values of Fe, Mn, Zn, Cd and Cu concentrations in fruit samples (mg/kg).

It can be notice that, while Cu concentration was under detection limit in bulb of carrot, in leaves of carrot a high concentration of Cu (157.84 mg/kg) was detected of which is over the recommendable maximum limit (73.3 mg/kg).

Table 4. Fe and Cd concentrations in fruits


Fe Cd

Stone 46.9565±0.0019 1.0543±0.0026 Green 49,28±0.0009 0.27±0.0042 Almost

ripe 73.94±0.0012 2.96±0.002

Ripe 92.02±0.0048 5.43±0.0003

Peach (Prunus persica)

Leaves 193.74±0.0004 31.3±0.0027 Stone 67.0723±0.0043 0.8336±0.0019 Green 19.14±0.0001 2.76±0.0001 Almost

ripe 21.09±0.0015 4.72±0.0016

Ripe 38.74±0.0003 5.98±0.0004

Nectarine (Prunus

persica var.nucipersica)

Leaves 180.32±0.0005 16.32±0.0009

Table 5. Mn, Zn and Cu concentrations in fruits

Concentrations (mg/kg) Sample Mn Zn Cu

Stone <LD 4.6304±0.0022 <LD Green 18.42±0.0007 4.27±0.0014 0.07±0.0002 Almost

ripe 22.93±0.0022 6.23±0.0008 <LD

Ripe 49.16±0.0031 11.05±0.0024 9.35±0.0017

Peach (Prunus persica)

Leaves 62.95±0.0005 18.42±0.0002 24.04±0.0009 Stone <LD 0.5918±0.003 <LD Green 2.47±0.0021 7.02±0.0004 <LD Almost

ripe <LD 5.91±0.0013 0.02±0.0001

Ripe 29.36±0.0054 19.46±0.0022 0.93±0.0021

Nectarine (Prunus persica

var.nucipersica)

Leaves 44.95±0.0015 35.92±0.0031 1.57±0.0007

This can happened maybe because the leaves (which were situated at the surface of the soil) were sprinkled with different insecticides. Iron was found in higher quantities than cadmium, manganese, zinc and copper in the both studied sample of carrot. Adhikari et al. (2004) have found in carrot root 80 mg/kg iron, 68 mg/kg manganese, 18.50 mg/kg zinc, 6.06 mg/kg copper while cadmium was not detected. It was also observed that the detected concentrations in this study were higher for iron, zinc, copper, cadmium and lower for manganese. Another work (Pless-Mulloli, 2001) shows that cadmium concentrations detected in carrot were between 0.01-0.03 mg/kg, copper concentrations ranged between 0.2-0.94 mg/kg and zinc concentrations between 1.6 and 4.4 mg/kg. It can be noticed that the detected concentrations of these metals in the present study were higher than those from literature.

For rape, cucumber, wheat, oats and tomato Pettersson (1976) found the nickel, and especially the cadmium, concentration in roots and shoots increases with the age of the plant. Cadmium concentrations for all vegetables studied were over the recommendable maximum limit in vegetables: 0.2 mg/kg (Food Standards Programme, 2001) (excepting leaves and

fruit of cucumber, which were under the detection limit). Lacatusu (2006) found direct proportionality relations between heavy metals contents in vegetables garden soils and the contents of the same chemical elements in some edible parts of vegetables (salad, carrot, onion, tomato, cucumber), that attest a certain plants contamination with heavy metals.

Tahvonen et al. (1991) studied the mean contents of Pb (µg/kg) and Cd (µg/kg) in various vegetables and found the values showed in Table 6. According to another another report (Byker ash vegetable report, 2001) the following levels: Cd (0.01-0.06); Cu (0.2- 0.06) and Zn (0.01 – 0.15) (µg/kg) were found in some vegetables (beetroot, cabbage, carrot, potato). The recommendable maximum limit for Zn in vegetables is 99.4 mgkg so only root and leaves of cucumber contain more zinc. All the studied sampled are under the recommendable maximum limit of Mn in vegetables (500 mg/kg).

Tables 6. Mean concentration of Pb and Cd in vegetables

(Tahoven et al., 1991)

Concentrations (µg/kg) Vegetables Pb Cd

Tomates 3.0 2.0 Carrot 8.0 10.0

Cucumber 2.0 <1 Onion 4.0 18.0

Cabbage 3.0 3.0 Lettuce 8.0 13.0

Iron concentrations found in fruits are in

higher quantities than other studied metals. Ivanova et al. (2001) found in leaves of peach the following levels: Cd-22 (µg/kg), Cr-920 (µg/kg), Cu-3200 (µg/kg), Ni-770 (µg/kg), Pb-790 (µg/kg), Zn-17200 (µg/kg). Excepting Cu concentration from leaves of peach that is higher (24.04 mg/kg) all the rest of metal concentrations are in concordance with those showed in literature. Dobra and Viman (2006) have studied the metals concentrations in fruits and vegetables and for peach have found: Pb: 55.5 ppm, Zn: 34.81 ppm and Cu: 40.8 ppm. These results are in the same range with those obtained experimental for peach in different stages of growing. Gergen et al. (2006) found following values of metal concentrations in peach (mg/kg): Fe: 4.15; Mn: 2.10; Zn: 1.08; Cu: 0.44; Co: 0.35; Ni: 0.72; Cr: 0.22; Pb: 0.10 and Cd: 0.02. Excepting iron, which is in higher quantity all the metals concentrations are in good corelation with those showed by Gergen et al. (2006). The results for peach obtained in this study, are also in concordance with the values of Secer et al. (2002) who found for peach the following concentrations (mg/kg): Fe-12.5; Co(1.16-2.51), Ni(0.23-2.16); Cr(0.06-1.11); Cu(0.2-1.1).

4. Conclusions

This study has investigated the content of

some essential elements (Fe, Mn, Mg and Zn) in various types of vegetables and fruits.

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Concentrations of iron found in the bulb of carrot (825.51 mg/kg), in stem (506.03 mg/kg) and in leaves (1207.18 mg/kg) of cucumber were over the allowable maximum limit of iron in vegetables; of 425.5 mg/kg. Iron concentrations are higher in leaves of bean and pea plant compared with the others parts of these plants.

While Cu concentration was under detection limit in bulb of carrot, a high concentration of Cu (157.84 mg/kg) was detected in carrot leaves, which is over the allowable maximum limit (73.3 mg/kg).

All the studied samples are under the recommendable maximum limit of Mn in vegetables (500 mg/kg).

Iron concentrations found in fruits are in higher quantities than the other studied metals.

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(Banat Country), Proc. of 7th Int. Symp. Of Romanian Academy-Branch Timisoara, Nov. 6-8, Timisoara, Romania.

Ivanova J., Korhammer S., Djingova R., Heidenreich H., Markert B., (2001), Determination of lanthanoids and some heavy and toxic elements in plant certified reference materials by inductively coupled plasma mass spectrometry, Spectro. Acta., 56, 3-12.

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Environmental Engineering and Management Journal, Vol. 6 Nr. 6

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