Research ArticleDetermination of Total Chromium and ChromiumSpecies in Kombolcha Tannery Wastewater Surrounding Soiland Lettuce Plant Samples South Wollo Ethiopia
Tilahun Belayneh Asfaw Tewodros Mulugeta Tadesse and Alamir Mihertu Ewnetie
Department of Chemistry College of Natural and Computational Sciences Gondar University PO Box 196 Gondar Ethiopia
Correspondence should be addressed to Tilahun Belayneh Asfaw tilahunbelaynehuogeduet
Received 10 April 2017 Accepted 14 August 2017 Published 25 September 2017
Academic Editor Maria Carmen Yebra-Biurrun
Copyright copy 2017 Tilahun Belayneh Asfaw et alThis is an open access article distributed under the Creative CommonsAttributionLicense which permits unrestricted use distribution and reproduction in anymedium provided the originalwork is properly cited
This research paper deals with the determination of total chromium (total Cr) Cr(III) and Cr(VI) in Kombolcha leather industrialwastewater and the surrounding (soil and lettuce plant) samples where the wastewater flows The levels of total Cr Cr(VI) andCr(III) in wastewater soil and lettuce plant samples were determined by FAAS UVVis spectrophotometer and difference (Cr(VI)from total Cr) respectively Among all samples taken the maximum amounts of total Cr Cr(III) and Cr(VI) were obtained atthe discharging point and the minimum amounts of total Cr and Cr(III) were found downstream (400 m from the junction)of Kombolcha leather industrial wastewater On the other hand the minimum concentration of Cr(VI) was obtained in lettuceplant sample The amounts of total Cr in all samples except soil sample were above the permissible limit as set by WHOFAOThe concentrations of Cr(III) in all wastewater samples were above the permissible level whereas the concentration of Cr(VI) inwastewater was above the permissible level except 400 m from the junction The result showed that a remarkable elimination oftotal Cr and Cr species has not been achieved by this leather industry as its level was not much decreased when entered into thewater systems Therefore effective treatment methods should be applied to the wastewater for the wellbeing of the surroundings
1 Introduction
The release of huge amount of industrial toxic waste productsto the environment has detrimental effects on humans andanimals [1] Waste toxicity and postdisposal behavior poorplanning poor treatment processes improper disposal andpoor management of disposal sites are the main reasons ofserious contamination problems at industrial and hazardouswaste disposal areas [2 3] Electroplating and leather indus-tries are the major cause for high amount of chromium in thebiosphere This huge quantity of chromium salts dischargedas tannery waste has raised several ecological concerns [4]
Chromium occurs in the environment in different formsunder various chemical physical and morphological condi-tions Under these conditions Cr shows oxidation states from0 to 6 in the environment Among those oxidation states onlyCr(III) andCr(VI) are stable [5ndash7]The totalmean concentra-tion of chromium ranges from 7 to 150 ppm [8] However itscontent and distribution in the soilmainly depend on the type
of the soilrsquos mother rockThe presence of additional amountsof Cr in the soil is caused by human activity Chromiumtakes place as Cr(III) cation only in a strongly acidic andreducingmediumwhileCr(VI) occurs in a strongly basic andoxidizing medium as CrO4
2minus anion [9ndash12]Because of the tendency of Cr(III) to bind to cell walls
of plants it is mainly concentrated in roots [13] Cr(VI)is the most available form of Cr species and very unstableform under normal soil conditions However its availabilitydepends on soils properties and especially on soil texture andpH Contents of Cr in plants have recently received muchattention due to the knowledge of this essentialmicronutrientin human metabolic processes and its carcinogenic effectsThus an adequate rate of nutritional Cr has become animportant issue [14]
Kombolcha is located 252 km from the capital of AddisAbaba Ethiopia Kombolcha tannery was built in 1967 inKombolcha town South Wollo Administrative Zone Amha-ra regional state The town has a latitude and longitude of
HindawiAdvances in ChemistryVolume 2017 Article ID 6191050 7 pageshttpsdoiorg10115520176191050
2 Advances in Chemistry
Figure 1 Wastewater at the discharging point
Figure 2 The place where the plant and soil samples were taken
11∘51015840N 39∘441015840E with an elevation between 1842 and 1915meters above sea levelThe tannery is a private share companyand processes hides and skins to semifinished and finishedleather and leather products for local and export purposesIt has a tanning capacity of about 15 million skins per yearTheprocessingwastes are treatedwith only a classicalmethodof waste treatment mechanism before being discharged tothe surroundings The classical methods are adsorption ofwaste by plants as it passes on the watersheds No work hasbeen done ever before on this leather industrial waste Thisindustry is located at the riverside of Luyelye and dischargesits waste to this river This river water also enters into a bigriver Borkena This may potentially risk the lives of humansand animals that are directly or indirectly dependent onthese river waters Therefore the purpose of this researchis to determine the concentrations of total Cr and Cr(VI)in wastewater soil and lettuce plant samples using FAASandUVVis spectrophotometer whereas the concentration ofCr(III) was done by difference (concentration of Cr(VI) fromtotal Cr)
2 Materials and Methods
21 Sampling Site The study was carried out at Kombolchatown which is found in Amhara region of SouthWollo ZoneEthiopia The required wastewater soil and plant sampleswere collected from the areas closer to the leather industry
22 Sample Collection and Preparation
221 Water Sampling The wastewater samples were col-lected from four different places at discharging point (KW1Figure 1) at junction (KW2) and after the junction at adistance of 200m (KW3) and 400m from the junction or
downstream (KW4) where KW is Kombolcha wastewaterSampling time was based on the discharging time of thetannery wastes from the industry Then the samples werecollected at 6 30 AM in the morning using 500mL highdensity polyethylene bottles and preserved with 2mL ofHNO3 Then the samples were immediately transported toUniversity of Gondar chemistry laboratory by using an icebag and finally thewastewater sampleswere filtered and readyfor digestion
222 Plant Sampling Fresh lettuce plant samples were col-lected from the farmland of the areas nearly 25 km farfrom Kombolcha leather industry To make the samplesrepresentative three subsamples (1 kg) from each samplingsite were taken from the irrigated farmland This farmlandwas randomly chosen from the three triangular corners ofthe area One kilogram of fresh plant samples was collectedfrom the farmland and put in labeled clean polyethyleneplastic bags and brought to the laboratory by an ice bag Thesampling sites of plants and soils are represented in Figure 2
223 Soil Sampling The soil samples were collected exactlyat the same place as the plant samples were grown (15ndash20 cmdepth) Sampling was done similar to the plant Half-kilogram soil samples were collected from the farmland andput in labeled clean polyethylene plastic bags and brought tothe laboratory by an ice bag The soil samples were mixedtogether and homogenized to form one composite sampleThen the composite sample was air dried for three days andsieved through a 2ndashmm sieve to remove large debris stonesand gravels Finally the sieved samples were ground usinga mortar and pestle to pass a 500120583m sieve and ready fordigestion
Advances in Chemistry 3
Table 1 Recovery test of total Cr by FAAS for tannery wastewater soil and plant samples
Industry Site Amount added (ppm) Amount recorded (ppm) Recovery ()
K = Kombolcha W = wastewater sample S = soil sample PLS = plant leaf sample and PRS = plant root sample
23 Validation of the Method The metal concentration andspeciation were determined at optimum conditions of ratioof acids mixtures time of digestion and temperature byvarying one condition and keeping others constantThen thedetermination of the concentration of total Cr Cr(III) andCr(VI) was done using the optimized parameters The spik-ing experiments were analyzed by using standard referencematerialsThe validations of themethodwere done by adding1mLof reference standardmaterial towastewater lettuce andsoil samples The digestion was carried out side by side withthe sample digestion For the case of Cr(VI) on the abovespiked samples 1mL of prepared diphenyl carbazide solutionwas added and a red violet color was immediately developedFrom the absorbance reading the amount of Cr(VI) wasobtained using calibration curve
24 Digestion of Lettuce Plant and Soil Samples Applyingthe optimized condition 05 g of air dried and homogenizedlettuce plant and soil samples were transferred into 250mLdifferent round bottom flasks separately Then 7mL of amixture of HNO3 (69ndash72) HClO4 (70) and H2O2 (30)with a volume ratio of 4 2 1 (vv) was added to the lettuceplant sample whereas 6mL of modified aqua-regia (3 1 05)ratio of HCl (36) HNO3 and H2O2 was added to thesoil sample Then the mixture was digested on a Kjeldahldigestion apparatus fitting the flask to a reflux condenserTheoptimum temperature and digestion time for lettuce samplewere 270∘C and 2 hr and for soil sample were 270∘C and3 hr The digested samples were allowed to cool to roomtemperature for 10min To these cooled solutions 15mL ofdistilled water was added to dilute the acid concentrationThen the solutions were filtered with Whatman filter paper(110mm diameter) into 50mL volumetric flask The roundbottom flask was rinsed subsequently with 5mL distilledwater until the total volume reached around 45mL To thisfinal solution 2 HNO3 was added and filled to the markThe digested solutions were carried out in triplicate for bothsamples Digestions of reagent blanks for both samples werealso performed in parallel with the samples The digestedsamples were kept in a refrigerator for 12 hrThen the amountof total Cr in the sample solutions was determined [15]
25 Digestion of Wastewater Samples 50mL of each of thefiltered water samples was transferred into different 250mLround bottomflasks To this sample 10mL of aqua-regia (3 1)ratio of 37HCl to (69ndash72)HNO3 and 2mLofH2O2 (30)were added and the mixture was digested on a Kjeldahl blockdigestion apparatus fitting the flask to a reflux condenser atthe optimized conditions (with programmed temperature at300∘C for 2 hr until 10mL of the water sample remains) Thenext steps were similar to the steps applied in plant and soilsamples The digested samples were kept in a refrigeratorfor 12 hr until the levels of the total Cr and Cr(VI) weredetermined [16]
26 Analysis of Wastewater Plant and Soil Samples forTotal Cr and Cr(VI) Levels The instruments were calibratedusing four series of working standards for FAAS (BUCKSCIENTIFIC MODEL 210 VGP USA) and five for UVVisspectrophotometer (Intech-Model-I-290 USA) The work-ing standard solutions of Cr were prepared freshly from1000 ppm stock solution (Buck Scientific 9999) by dilutingthe intermediated standard solution (25mgL) The instru-ment was calibrated using five series of working standards forUVVis spectrophotometer A solution of 1mL of diphenylcarbazide was added to each sample and working standardsolution Similarly the pH of the spiked sample solution wasadjusted to the desired value (pH = 1) at which the recoveryof Cr(VI) is the highest Then the equilibrium concentrationof Cr(VI) in the organic phase was determined spectropho-tometrically by measuring the absorbance of Cr(VI)-DPC(diphenyl carbazide) complex at 540 nm [17]
27 Statistical Analysis Statistical analyses were carried outby one-way ANOVA of Tamhane and LSD comparison posthoc tests Significant differences were accepted at 119901 lt 005The analyses were performed using SPSS Statistics software(version 160 for Windows 7)
3 Results and Discussion
31 Recovery of the Method As shown in Tables 1 and 2the results of percentage recoveries of total Cr and Cr(VI)
4 Advances in Chemistry
Table 2 Recovery test of Cr(VI) using UV analysis for tannery wastewater soil and plant samples
Industry Site Amount added (ppm) Amount recorded (ppm) Recovery ()
Table 3 Distribution of total Cr Cr(VI) and Cr(III) concentration (mean plusmn SD mgL for wastewater samples and 120583gg for soil and plantsamples) in different sites of Kombolcha leather industry
Industry Site [Cr] [Cr(VI)] [Cr(III)] through difference
a = mgL for wastewater samples b = 120583gkg for soil and plant samples
for wastewater lettuce plant and soil samples were withinthe acceptable range [18] The average percent recoverieswere 981 plusmn 63 for wastewater 941 plusmn 281 for lettuce plantand 946 plusmn 41 for soil samples using FAAS Therefore thisverifies that the optimized digestion procedure was valid forwastewater lettuce plant and soil sample analysis
The average percent recoveries of Cr(VI) for wastewaterlettuce plant and soil samples were 9464plusmn334 9100plusmn281and 9240plusmn763 respectivelyThis verifies that the procedureswere valid for wastewater lettuce plant and soil samplesanalysis
32 Determination of Total Cr Cr(VI) and Cr(III) In thisstudy the total Cr concentrations in wastewater soil andplant samples at different sites of the industry were deter-mined by FAAS Significant amount of total Cr was releasedat the discharging point The main source of total Cr in thenearby water system comes from the tanning effluent Thisis because even after the wastewater joins the river water theconcentration of total Cr was decreasing slightlyThe effluentwas much concentrated with total Cr at the discharging pointand decreased as it flows down from the discharging point
In the analysis of Cr(VI) using UVVis a sharp peak wasobserved at wavelength of 540 nm due to absorption of lightby Cr(VI)-DPC complexThe influences of pH on the signalsof Cr(VI) in all samples were obtained in the range of pH1 to pH 4 The results showed that the highest absorbancewas obtained at pH 1 Therefore pH 1 was chosen as the
optimum pH value for all measurements The high load ofgreen coloration of the sample was due to the presence ofhigh Cr(III) aqua complex The concentration of Cr(III) wascalculated by the difference of Cr(VI) concentration fromthe total Cr content The distribution of total Cr Cr(VI)and Cr(III) concentrations in the wastewater soil and lettuceplant samples at different sites and different distances ispresented in Table 3
The maximum and minimum concentrations of total CrCr(III) and Cr(VI) were 82387 plusmn 1362 and 124 plusmn 0482182186 plusmn 13569 and 1207 plusmn 04772 and 2014 plusmn 0051 and0033 plusmn 00049 respectively The maximum concentrationswere obtained at the discharging point of wastewater samplewhile the minimum was found at the downstream waterThe reason for the maximum value at the discharging pointwas due to the use of high amount of chrome salt Besidesthe concentrations of total Cr Cr(VI) and Cr(III) weredramatically decreased from the discharging point to thejunction point These might be due to adsorption of wastesby various plants in the watershed and dilution of the wastewith river water [19]
From the total Cr concentration it was found thatCr(VI) accounts for 024ndash266 while Cr(III) accountsfor 9734ndash9976 of the pollution status of the wastewaterThe reason for the increased Cr(VI) concentration in thewastewater compared to its total Cr concentration might bedue to the pH (acidity) of the wasteThe pH of the wastewatersamples measured was found to be 36 to 47 before junction
Advances in Chemistry 5
KW1 KW2 KW3
Average concentration in ppm
Average concentration in ppm
0
200
400
600
800
1000
KW4
(a)
Average concentration in ppm
Average concentration in ppmKW2 KW3 KW4
0
5
10
15
20
25
(b)Figure 3 Total Cr concentration in wastewater ((a) = average concentration of all wastewater samples (b) = average concentration fromjunction to downstream wastewater samples)
and 5 to 58 after junction This showed that the wastewaterwas acidic which contributes to the increased accumulationof Cr(VI) in the study areas It is because Cr(VI) is morestable and exists in much proportion in the acidic mediumas HCrO4
minus (1 lt pH lt 7) Similarly the concentration ofCr(VI) was found to be 0075 in soil and 073ndash122 inplant samples As a result Cr(III) is widespread in all samplescompared with Cr(VI) which is consistent with the onedescribed by Onchoke and Sasu [16]
33 The Potential Pollution Effect of the Kombolcha TanneryWastewater The determinations of the levels of total CrCr(VI) and Cr(III) in the wastewater soil and plant samplesaround the area of the leather industry were performed toassess the influence of the tannery effluent on the surround-ing environment The levels of both Cr(III) and Cr(VI) weredecreased from discharge point to downstream wastewatersamples as shown in Figures 3 and 4 The distribution ofboth Cr(III) and Cr(VI) in the wastewaters follows the orderKW1gtKW2gtKW3gtKW4 The concentrations of Cr(VI) inplant and soil samples were much lower than Cr(III) Thisis due to the fact that chrome (Cr(III) salts) is used whichcontains about 25 Cr2O3 with 33 basicity [20ndash22] Basicchrome sulphate liquor is also used which is prepared byreducing the NaK dichromate in the presence of H2SO4 [23]and also in addition to this in the soil Cr(VI) interactedwith organic matters and reduced into Cr(III) As a resultthe concentration of Cr(III) is extremely higher than that ofCr(VI)
ANOVA also showed that mean concentrations of totalCr and chromium species at the discharging point in wastew-ater sample were statistically significant (119901 = 005) when
compared with other samples (from junction to downstreamwastewater soil and plant)However the post hoc descriptiveanalysis showed that the mean concentrations of total Cr andchromium species had no significant differences among allsamples except KW1
The results obtained in this research were comparedwith other reported values The amounts of total Cr atthe discharging point of Kombolcha tannery wastewaterwere higher than the values described by Homa et al(19126ndash39696mgL) [15] The concentration of Cr(III) isalso extremely higher than the reported value by Homaet al (19126ndash39374mgL) [15] Moreover the amount ofCr(VI) obtained in this study at the discharging point washigher than that of Homa et al (0ndash0322mgL) [15] In thedownstream case all chromium species were lower thanother reported values The results of this study were alsocompared with themaximumpermissible limit (01mgL) setby WHO The total Cr values in all wastewater samples werehigher than the maximum permissible limit (01mgL) set byWHOFAO
Thevalue of total Cr (226mgkg) in the soil sample of thisstudy wasmuch lower than the values reported inHoma et al(25425ndash158166mgkg) [15] as well as the permissible limit(100mgkg) by WHO and FAO The total Cr Cr(III) andCr(VI) which were obtained in the lettuce plant samples werealso lower than those reported by Homa et al (74163ndash1047373913ndash1036 and 0025ndash0113mgkg resp) [15] but total Crwas higher than the permissible level (13mgkg) by WHOand FAO
Generally chromium and chromium species released tothe environment have detrimental effects on human and ani-mal hygiene and also are not easily degraded or removed from
6 Advances in Chemistry
200
0
400
600
800
1000
0
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
KW2KW1 KW3 KW4
(a)
KW2 KW3 KW4
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
0
5
10
15
20
25
(b)Figure 4 Comparison of the concentration of Cr(VI) and Cr(III) in the wastewaters ((a) = average concentration of all wastewater samples(b) = average concentration from junction to downstream wastewater samples)
the environment Some of them are gastric cancer disabilitygenetic modification and kidney and liver problems [24ndash26] This study shows that huge amounts of chromium andchromium species were released to the surrounding riverwater irrigated land and plants Even if the river water dilutesthe waste it does not mean that it is harmlessThis is becauseit is accumulated in the environment which is due to itsinteraction with different substances and found either as aprecipitate or in the food chain
4 Conclusions
The levels of total Cr Cr(VI) and Cr(III) in tannery wastew-ater soil and lettuce plant samples were determined by FAASand UVVis and through difference respectively The totalCr and Cr species determined in the sample collected fromthe discharging point were muchmore concentrated than thedownstream sample (at a distance of 400m from the junctionpoint) The concentration of Cr decreases from dischargepoint to downstream sample The decrease in concentrationwas due to adsorption by various plants in the watershedclassical treatment method and dilution as the wastewaterjoins the river The amounts of total Cr and Cr species werebeyond the permissible limit set by WHO and FAO
The amount of total Cr Cr(VI) and Cr(III) whichwas entering into the river was actually not too much as
compared to its level in the discharge point of the specifiedsite But the result showed that a remarkable eliminationof total Cr Cr(VI) and Cr(III) has not been achieved bythis leather industry as its level was not much decreasedwhen entered into the water systems Since the dischargedchromium wastes entered to the nearby Kete River this inturn caused the contamination of the big river Borkena Asa result this contamination can increase the accumulationof chromium in the river water and the surroundings andbring a potential adverse impact to the population around itTherefore effective treatment methods should be applied tothe wastewater to protect the ecosystem
Conflicts of Interest
The authors declare that there are no conflicts of interest
Acknowledgments
Theauthors take this opportunity to express their gratitude toall those whomotivated encouraged and helped them in thisresearch work Again their deepest thanks go to Departmentof Chemistry University of Gondar for providing them withthe necessarymaterials and facilities to conduct this researchAbove all they would like to give hearty thanks to theirfamilies for their care and moral support for continuous loveand support which strengthen them
Advances in Chemistry 7
References
[1] N Unlu and M Ersoz ldquoAdsorption characteristics of heavymetal ions onto a low cost biopolymeric sorbent from aqueoussolutionsrdquo Journal of Hazardous Materials vol 136 no 2 pp272ndash280 2006
[2] T Watanabe and T Hirayama ldquoGenotoxicity of soilrdquo Journal ofHealth Science vol 47 no 5 pp 433ndash438 2001
[3] PAWhite andLDClaxton ldquoMutagens in contaminated soil areviewrdquoMutation ResearchmdashReviews in Mutation Research vol567 no 2-3 pp 227ndash345 2004
[4] PQuevauviller E AMaier andBGriepink ldquoQuality assurancefor environmental analysisrdquo Techniques and Instrumentation inAnalytical Chemistry vol 17 no C pp 1ndash25 1995
[5] W EMotzer SM Testa J Guertin and F T StaninChromium(VI) Hand Book CRC Press New York NY USA 1st edition2005
[6] D Mohan U Charles and J Pittman ldquoActivated carbons andlow cost adsorbents for remediation of tri and hexavalentchromium fromwaterrdquo Journal of HazardousMaterials vol 137no 2 pp 762ndash811 2006
[7] J Barnhart ldquoOccurrences uses and properties of chromiumrdquoRegulatory Toxicology and Pharmacology vol 26 no 1 pp S3ndashS7 1997
[8] B Jankiewicz and B Ptaszynski ldquoDetermination of chromiumin soil of lody gardens polishrdquo Journal of Environmental Studiesvol 14 no 6 pp 869ndash875 2005
[9] V Gomez and M P Callao ldquoChromium determination andspeciation since 2000rdquo TrACmdashTrends in Analytical Chemistryvol 25 no 10 pp 1006ndash1015 2006
[10] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[11] P Venkateswarlu and M V Ratnam ldquoRemoval of chromiumfrom an aqueous solution using Azadirachta indica (Neem)leaf powder as an adsorbentrdquo International Journal of PhysicalSciences vol 2 no 8 pp 188ndash195 2007
[12] J Mwamburi ldquoChromium distribution and spatial variations inthe finer sediment grain size fraction and unfractioned surficialsediments on Nyanza Gulf of Lake Victoria (East Africa)rdquoJournal of Waste Management vol 2016 pp 1ndash15 2016
[13] J Lopez-LunaM C Gonzalez-Chavez F J Esparza-Garca andR Rodrıguez-Vazquez ldquoFractionation and availability of heavymetals in tannery sludge-amended soil and toxicity assessmenton the fully-grown Phaseolus vulgaris cultivarsrdquo Journal ofEnvironmental Science and Health - Part A ToxicHazardousSubstances and Environmental Engineering vol 47 no 3 pp405ndash419 2012
[14] A M Zayed and N Terry ldquoChromium in the environmentfactors affecting biological remediationrdquoPlant and Soil vol 249no 1 pp 139ndash156 2003
[15] D Homa E Haile and A P Washe ldquoDetermination of spatialchromiumcontamination of the environment around industrialzonesrdquo International Journal of Analytical Chemistry vol 2016Article ID 7214932 7 pages 2016
[16] K K Onchoke and S A Sasu ldquoDetermination of HexavalentChromium (Cr(VI)) concentrations via ion chromatographyand UV-Vis spectrophotometry in samples collected fromnacogdoches wastewater treatment plant East Texas (USA)rdquoAdvances in Environmental Chemistry vol 2016 pp 1ndash10 2016
[17] A K Shanker C Cervantes H Loza-Tavera and S Avu-dainayagam ldquoChromium toxicity in plantsrdquo Environment Inter-national vol 31 no 5 pp 739ndash753 2005
[18] Massachusetts Department of Environmental Protection Bu-reau of Waste Site Cleanup Quality Control Requirementsand Performance Standards for the Analysis of HexavalentChromium Cr(VI) by UVVisible Spectrophotometry in Sup-port of ResponseActions under theMassachusetts ContingencyPlan (MCP)WSC-CAM Section VI B RevisionNo 1 pp 1-262010
[19] N T Joutey H Sayel W Bahafid and N E Ghachtouli ldquoMech-anisms of hexavalent chromium resistance and removal bymicroorganismsrdquoReviews of Environmental Contamination andToxicology vol 233 pp 45ndash69 2015
[20] F X Han Y Su B B Maruthi Sridhar and D L Monts ldquoDis-tribution transformation and bioavailability of trivalent andhexavalent chromium in contaminated soilrdquo Plant and Soil vol265 no 1-2 pp 243ndash252 2004
[21] APHA AWWA and WEF Standard Methods for the Exami-nation of Water and Wastewater 21st edition APHA AWWAWEF Washington DC (2005) and (2011)
[22] N J Miller and C J Miller ldquoStatistics and chemometrics foranalytical chemistry sixth editionrdquo Pearson Education Limitedpp 110ndash150 2010
[23] M E Mahmoud M M Osman O F Hafez and E Elmel-egy ldquoRemoval and preconcentration of lead (II) copper (II)chromium (III) and iron (III) from wastewaters by surfacedeveloped alumina adsorbents with immobilized 1-nitroso-2-naphtholrdquo Journal of Hazardous Materials vol 173 no 1-3 pp349ndash357 2010
[24] H I Abdel-Shafy W Hegemann and E Genschow ldquoFate ofheavy metals in the leather tanning industrial wastewater usingan anaerobic processrdquo Environmental Management and Healthvol 6 no 2 pp 28ndash33 1995
[25] H Egli et al ldquoSampling and handling of samplesrdquo IUPAC vol75 pp 1097ndash1106 2003
Figure 2 The place where the plant and soil samples were taken
11∘51015840N 39∘441015840E with an elevation between 1842 and 1915meters above sea levelThe tannery is a private share companyand processes hides and skins to semifinished and finishedleather and leather products for local and export purposesIt has a tanning capacity of about 15 million skins per yearTheprocessingwastes are treatedwith only a classicalmethodof waste treatment mechanism before being discharged tothe surroundings The classical methods are adsorption ofwaste by plants as it passes on the watersheds No work hasbeen done ever before on this leather industrial waste Thisindustry is located at the riverside of Luyelye and dischargesits waste to this river This river water also enters into a bigriver Borkena This may potentially risk the lives of humansand animals that are directly or indirectly dependent onthese river waters Therefore the purpose of this researchis to determine the concentrations of total Cr and Cr(VI)in wastewater soil and lettuce plant samples using FAASandUVVis spectrophotometer whereas the concentration ofCr(III) was done by difference (concentration of Cr(VI) fromtotal Cr)
2 Materials and Methods
21 Sampling Site The study was carried out at Kombolchatown which is found in Amhara region of SouthWollo ZoneEthiopia The required wastewater soil and plant sampleswere collected from the areas closer to the leather industry
22 Sample Collection and Preparation
221 Water Sampling The wastewater samples were col-lected from four different places at discharging point (KW1Figure 1) at junction (KW2) and after the junction at adistance of 200m (KW3) and 400m from the junction or
downstream (KW4) where KW is Kombolcha wastewaterSampling time was based on the discharging time of thetannery wastes from the industry Then the samples werecollected at 6 30 AM in the morning using 500mL highdensity polyethylene bottles and preserved with 2mL ofHNO3 Then the samples were immediately transported toUniversity of Gondar chemistry laboratory by using an icebag and finally thewastewater sampleswere filtered and readyfor digestion
222 Plant Sampling Fresh lettuce plant samples were col-lected from the farmland of the areas nearly 25 km farfrom Kombolcha leather industry To make the samplesrepresentative three subsamples (1 kg) from each samplingsite were taken from the irrigated farmland This farmlandwas randomly chosen from the three triangular corners ofthe area One kilogram of fresh plant samples was collectedfrom the farmland and put in labeled clean polyethyleneplastic bags and brought to the laboratory by an ice bag Thesampling sites of plants and soils are represented in Figure 2
223 Soil Sampling The soil samples were collected exactlyat the same place as the plant samples were grown (15ndash20 cmdepth) Sampling was done similar to the plant Half-kilogram soil samples were collected from the farmland andput in labeled clean polyethylene plastic bags and brought tothe laboratory by an ice bag The soil samples were mixedtogether and homogenized to form one composite sampleThen the composite sample was air dried for three days andsieved through a 2ndashmm sieve to remove large debris stonesand gravels Finally the sieved samples were ground usinga mortar and pestle to pass a 500120583m sieve and ready fordigestion
Advances in Chemistry 3
Table 1 Recovery test of total Cr by FAAS for tannery wastewater soil and plant samples
Industry Site Amount added (ppm) Amount recorded (ppm) Recovery ()
K = Kombolcha W = wastewater sample S = soil sample PLS = plant leaf sample and PRS = plant root sample
23 Validation of the Method The metal concentration andspeciation were determined at optimum conditions of ratioof acids mixtures time of digestion and temperature byvarying one condition and keeping others constantThen thedetermination of the concentration of total Cr Cr(III) andCr(VI) was done using the optimized parameters The spik-ing experiments were analyzed by using standard referencematerialsThe validations of themethodwere done by adding1mLof reference standardmaterial towastewater lettuce andsoil samples The digestion was carried out side by side withthe sample digestion For the case of Cr(VI) on the abovespiked samples 1mL of prepared diphenyl carbazide solutionwas added and a red violet color was immediately developedFrom the absorbance reading the amount of Cr(VI) wasobtained using calibration curve
24 Digestion of Lettuce Plant and Soil Samples Applyingthe optimized condition 05 g of air dried and homogenizedlettuce plant and soil samples were transferred into 250mLdifferent round bottom flasks separately Then 7mL of amixture of HNO3 (69ndash72) HClO4 (70) and H2O2 (30)with a volume ratio of 4 2 1 (vv) was added to the lettuceplant sample whereas 6mL of modified aqua-regia (3 1 05)ratio of HCl (36) HNO3 and H2O2 was added to thesoil sample Then the mixture was digested on a Kjeldahldigestion apparatus fitting the flask to a reflux condenserTheoptimum temperature and digestion time for lettuce samplewere 270∘C and 2 hr and for soil sample were 270∘C and3 hr The digested samples were allowed to cool to roomtemperature for 10min To these cooled solutions 15mL ofdistilled water was added to dilute the acid concentrationThen the solutions were filtered with Whatman filter paper(110mm diameter) into 50mL volumetric flask The roundbottom flask was rinsed subsequently with 5mL distilledwater until the total volume reached around 45mL To thisfinal solution 2 HNO3 was added and filled to the markThe digested solutions were carried out in triplicate for bothsamples Digestions of reagent blanks for both samples werealso performed in parallel with the samples The digestedsamples were kept in a refrigerator for 12 hrThen the amountof total Cr in the sample solutions was determined [15]
25 Digestion of Wastewater Samples 50mL of each of thefiltered water samples was transferred into different 250mLround bottomflasks To this sample 10mL of aqua-regia (3 1)ratio of 37HCl to (69ndash72)HNO3 and 2mLofH2O2 (30)were added and the mixture was digested on a Kjeldahl blockdigestion apparatus fitting the flask to a reflux condenser atthe optimized conditions (with programmed temperature at300∘C for 2 hr until 10mL of the water sample remains) Thenext steps were similar to the steps applied in plant and soilsamples The digested samples were kept in a refrigeratorfor 12 hr until the levels of the total Cr and Cr(VI) weredetermined [16]
26 Analysis of Wastewater Plant and Soil Samples forTotal Cr and Cr(VI) Levels The instruments were calibratedusing four series of working standards for FAAS (BUCKSCIENTIFIC MODEL 210 VGP USA) and five for UVVisspectrophotometer (Intech-Model-I-290 USA) The work-ing standard solutions of Cr were prepared freshly from1000 ppm stock solution (Buck Scientific 9999) by dilutingthe intermediated standard solution (25mgL) The instru-ment was calibrated using five series of working standards forUVVis spectrophotometer A solution of 1mL of diphenylcarbazide was added to each sample and working standardsolution Similarly the pH of the spiked sample solution wasadjusted to the desired value (pH = 1) at which the recoveryof Cr(VI) is the highest Then the equilibrium concentrationof Cr(VI) in the organic phase was determined spectropho-tometrically by measuring the absorbance of Cr(VI)-DPC(diphenyl carbazide) complex at 540 nm [17]
27 Statistical Analysis Statistical analyses were carried outby one-way ANOVA of Tamhane and LSD comparison posthoc tests Significant differences were accepted at 119901 lt 005The analyses were performed using SPSS Statistics software(version 160 for Windows 7)
3 Results and Discussion
31 Recovery of the Method As shown in Tables 1 and 2the results of percentage recoveries of total Cr and Cr(VI)
4 Advances in Chemistry
Table 2 Recovery test of Cr(VI) using UV analysis for tannery wastewater soil and plant samples
Industry Site Amount added (ppm) Amount recorded (ppm) Recovery ()
Table 3 Distribution of total Cr Cr(VI) and Cr(III) concentration (mean plusmn SD mgL for wastewater samples and 120583gg for soil and plantsamples) in different sites of Kombolcha leather industry
Industry Site [Cr] [Cr(VI)] [Cr(III)] through difference
a = mgL for wastewater samples b = 120583gkg for soil and plant samples
for wastewater lettuce plant and soil samples were withinthe acceptable range [18] The average percent recoverieswere 981 plusmn 63 for wastewater 941 plusmn 281 for lettuce plantand 946 plusmn 41 for soil samples using FAAS Therefore thisverifies that the optimized digestion procedure was valid forwastewater lettuce plant and soil sample analysis
The average percent recoveries of Cr(VI) for wastewaterlettuce plant and soil samples were 9464plusmn334 9100plusmn281and 9240plusmn763 respectivelyThis verifies that the procedureswere valid for wastewater lettuce plant and soil samplesanalysis
32 Determination of Total Cr Cr(VI) and Cr(III) In thisstudy the total Cr concentrations in wastewater soil andplant samples at different sites of the industry were deter-mined by FAAS Significant amount of total Cr was releasedat the discharging point The main source of total Cr in thenearby water system comes from the tanning effluent Thisis because even after the wastewater joins the river water theconcentration of total Cr was decreasing slightlyThe effluentwas much concentrated with total Cr at the discharging pointand decreased as it flows down from the discharging point
In the analysis of Cr(VI) using UVVis a sharp peak wasobserved at wavelength of 540 nm due to absorption of lightby Cr(VI)-DPC complexThe influences of pH on the signalsof Cr(VI) in all samples were obtained in the range of pH1 to pH 4 The results showed that the highest absorbancewas obtained at pH 1 Therefore pH 1 was chosen as the
optimum pH value for all measurements The high load ofgreen coloration of the sample was due to the presence ofhigh Cr(III) aqua complex The concentration of Cr(III) wascalculated by the difference of Cr(VI) concentration fromthe total Cr content The distribution of total Cr Cr(VI)and Cr(III) concentrations in the wastewater soil and lettuceplant samples at different sites and different distances ispresented in Table 3
The maximum and minimum concentrations of total CrCr(III) and Cr(VI) were 82387 plusmn 1362 and 124 plusmn 0482182186 plusmn 13569 and 1207 plusmn 04772 and 2014 plusmn 0051 and0033 plusmn 00049 respectively The maximum concentrationswere obtained at the discharging point of wastewater samplewhile the minimum was found at the downstream waterThe reason for the maximum value at the discharging pointwas due to the use of high amount of chrome salt Besidesthe concentrations of total Cr Cr(VI) and Cr(III) weredramatically decreased from the discharging point to thejunction point These might be due to adsorption of wastesby various plants in the watershed and dilution of the wastewith river water [19]
From the total Cr concentration it was found thatCr(VI) accounts for 024ndash266 while Cr(III) accountsfor 9734ndash9976 of the pollution status of the wastewaterThe reason for the increased Cr(VI) concentration in thewastewater compared to its total Cr concentration might bedue to the pH (acidity) of the wasteThe pH of the wastewatersamples measured was found to be 36 to 47 before junction
Advances in Chemistry 5
KW1 KW2 KW3
Average concentration in ppm
Average concentration in ppm
0
200
400
600
800
1000
KW4
(a)
Average concentration in ppm
Average concentration in ppmKW2 KW3 KW4
0
5
10
15
20
25
(b)Figure 3 Total Cr concentration in wastewater ((a) = average concentration of all wastewater samples (b) = average concentration fromjunction to downstream wastewater samples)
and 5 to 58 after junction This showed that the wastewaterwas acidic which contributes to the increased accumulationof Cr(VI) in the study areas It is because Cr(VI) is morestable and exists in much proportion in the acidic mediumas HCrO4
minus (1 lt pH lt 7) Similarly the concentration ofCr(VI) was found to be 0075 in soil and 073ndash122 inplant samples As a result Cr(III) is widespread in all samplescompared with Cr(VI) which is consistent with the onedescribed by Onchoke and Sasu [16]
33 The Potential Pollution Effect of the Kombolcha TanneryWastewater The determinations of the levels of total CrCr(VI) and Cr(III) in the wastewater soil and plant samplesaround the area of the leather industry were performed toassess the influence of the tannery effluent on the surround-ing environment The levels of both Cr(III) and Cr(VI) weredecreased from discharge point to downstream wastewatersamples as shown in Figures 3 and 4 The distribution ofboth Cr(III) and Cr(VI) in the wastewaters follows the orderKW1gtKW2gtKW3gtKW4 The concentrations of Cr(VI) inplant and soil samples were much lower than Cr(III) Thisis due to the fact that chrome (Cr(III) salts) is used whichcontains about 25 Cr2O3 with 33 basicity [20ndash22] Basicchrome sulphate liquor is also used which is prepared byreducing the NaK dichromate in the presence of H2SO4 [23]and also in addition to this in the soil Cr(VI) interactedwith organic matters and reduced into Cr(III) As a resultthe concentration of Cr(III) is extremely higher than that ofCr(VI)
ANOVA also showed that mean concentrations of totalCr and chromium species at the discharging point in wastew-ater sample were statistically significant (119901 = 005) when
compared with other samples (from junction to downstreamwastewater soil and plant)However the post hoc descriptiveanalysis showed that the mean concentrations of total Cr andchromium species had no significant differences among allsamples except KW1
The results obtained in this research were comparedwith other reported values The amounts of total Cr atthe discharging point of Kombolcha tannery wastewaterwere higher than the values described by Homa et al(19126ndash39696mgL) [15] The concentration of Cr(III) isalso extremely higher than the reported value by Homaet al (19126ndash39374mgL) [15] Moreover the amount ofCr(VI) obtained in this study at the discharging point washigher than that of Homa et al (0ndash0322mgL) [15] In thedownstream case all chromium species were lower thanother reported values The results of this study were alsocompared with themaximumpermissible limit (01mgL) setby WHO The total Cr values in all wastewater samples werehigher than the maximum permissible limit (01mgL) set byWHOFAO
Thevalue of total Cr (226mgkg) in the soil sample of thisstudy wasmuch lower than the values reported inHoma et al(25425ndash158166mgkg) [15] as well as the permissible limit(100mgkg) by WHO and FAO The total Cr Cr(III) andCr(VI) which were obtained in the lettuce plant samples werealso lower than those reported by Homa et al (74163ndash1047373913ndash1036 and 0025ndash0113mgkg resp) [15] but total Crwas higher than the permissible level (13mgkg) by WHOand FAO
Generally chromium and chromium species released tothe environment have detrimental effects on human and ani-mal hygiene and also are not easily degraded or removed from
6 Advances in Chemistry
200
0
400
600
800
1000
0
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
KW2KW1 KW3 KW4
(a)
KW2 KW3 KW4
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
0
5
10
15
20
25
(b)Figure 4 Comparison of the concentration of Cr(VI) and Cr(III) in the wastewaters ((a) = average concentration of all wastewater samples(b) = average concentration from junction to downstream wastewater samples)
the environment Some of them are gastric cancer disabilitygenetic modification and kidney and liver problems [24ndash26] This study shows that huge amounts of chromium andchromium species were released to the surrounding riverwater irrigated land and plants Even if the river water dilutesthe waste it does not mean that it is harmlessThis is becauseit is accumulated in the environment which is due to itsinteraction with different substances and found either as aprecipitate or in the food chain
4 Conclusions
The levels of total Cr Cr(VI) and Cr(III) in tannery wastew-ater soil and lettuce plant samples were determined by FAASand UVVis and through difference respectively The totalCr and Cr species determined in the sample collected fromthe discharging point were muchmore concentrated than thedownstream sample (at a distance of 400m from the junctionpoint) The concentration of Cr decreases from dischargepoint to downstream sample The decrease in concentrationwas due to adsorption by various plants in the watershedclassical treatment method and dilution as the wastewaterjoins the river The amounts of total Cr and Cr species werebeyond the permissible limit set by WHO and FAO
The amount of total Cr Cr(VI) and Cr(III) whichwas entering into the river was actually not too much as
compared to its level in the discharge point of the specifiedsite But the result showed that a remarkable eliminationof total Cr Cr(VI) and Cr(III) has not been achieved bythis leather industry as its level was not much decreasedwhen entered into the water systems Since the dischargedchromium wastes entered to the nearby Kete River this inturn caused the contamination of the big river Borkena Asa result this contamination can increase the accumulationof chromium in the river water and the surroundings andbring a potential adverse impact to the population around itTherefore effective treatment methods should be applied tothe wastewater to protect the ecosystem
Conflicts of Interest
The authors declare that there are no conflicts of interest
Acknowledgments
Theauthors take this opportunity to express their gratitude toall those whomotivated encouraged and helped them in thisresearch work Again their deepest thanks go to Departmentof Chemistry University of Gondar for providing them withthe necessarymaterials and facilities to conduct this researchAbove all they would like to give hearty thanks to theirfamilies for their care and moral support for continuous loveand support which strengthen them
Advances in Chemistry 7
References
[1] N Unlu and M Ersoz ldquoAdsorption characteristics of heavymetal ions onto a low cost biopolymeric sorbent from aqueoussolutionsrdquo Journal of Hazardous Materials vol 136 no 2 pp272ndash280 2006
[2] T Watanabe and T Hirayama ldquoGenotoxicity of soilrdquo Journal ofHealth Science vol 47 no 5 pp 433ndash438 2001
[3] PAWhite andLDClaxton ldquoMutagens in contaminated soil areviewrdquoMutation ResearchmdashReviews in Mutation Research vol567 no 2-3 pp 227ndash345 2004
[4] PQuevauviller E AMaier andBGriepink ldquoQuality assurancefor environmental analysisrdquo Techniques and Instrumentation inAnalytical Chemistry vol 17 no C pp 1ndash25 1995
[5] W EMotzer SM Testa J Guertin and F T StaninChromium(VI) Hand Book CRC Press New York NY USA 1st edition2005
[6] D Mohan U Charles and J Pittman ldquoActivated carbons andlow cost adsorbents for remediation of tri and hexavalentchromium fromwaterrdquo Journal of HazardousMaterials vol 137no 2 pp 762ndash811 2006
[7] J Barnhart ldquoOccurrences uses and properties of chromiumrdquoRegulatory Toxicology and Pharmacology vol 26 no 1 pp S3ndashS7 1997
[8] B Jankiewicz and B Ptaszynski ldquoDetermination of chromiumin soil of lody gardens polishrdquo Journal of Environmental Studiesvol 14 no 6 pp 869ndash875 2005
[9] V Gomez and M P Callao ldquoChromium determination andspeciation since 2000rdquo TrACmdashTrends in Analytical Chemistryvol 25 no 10 pp 1006ndash1015 2006
[10] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[11] P Venkateswarlu and M V Ratnam ldquoRemoval of chromiumfrom an aqueous solution using Azadirachta indica (Neem)leaf powder as an adsorbentrdquo International Journal of PhysicalSciences vol 2 no 8 pp 188ndash195 2007
[12] J Mwamburi ldquoChromium distribution and spatial variations inthe finer sediment grain size fraction and unfractioned surficialsediments on Nyanza Gulf of Lake Victoria (East Africa)rdquoJournal of Waste Management vol 2016 pp 1ndash15 2016
[13] J Lopez-LunaM C Gonzalez-Chavez F J Esparza-Garca andR Rodrıguez-Vazquez ldquoFractionation and availability of heavymetals in tannery sludge-amended soil and toxicity assessmenton the fully-grown Phaseolus vulgaris cultivarsrdquo Journal ofEnvironmental Science and Health - Part A ToxicHazardousSubstances and Environmental Engineering vol 47 no 3 pp405ndash419 2012
[14] A M Zayed and N Terry ldquoChromium in the environmentfactors affecting biological remediationrdquoPlant and Soil vol 249no 1 pp 139ndash156 2003
[15] D Homa E Haile and A P Washe ldquoDetermination of spatialchromiumcontamination of the environment around industrialzonesrdquo International Journal of Analytical Chemistry vol 2016Article ID 7214932 7 pages 2016
[16] K K Onchoke and S A Sasu ldquoDetermination of HexavalentChromium (Cr(VI)) concentrations via ion chromatographyand UV-Vis spectrophotometry in samples collected fromnacogdoches wastewater treatment plant East Texas (USA)rdquoAdvances in Environmental Chemistry vol 2016 pp 1ndash10 2016
[17] A K Shanker C Cervantes H Loza-Tavera and S Avu-dainayagam ldquoChromium toxicity in plantsrdquo Environment Inter-national vol 31 no 5 pp 739ndash753 2005
[18] Massachusetts Department of Environmental Protection Bu-reau of Waste Site Cleanup Quality Control Requirementsand Performance Standards for the Analysis of HexavalentChromium Cr(VI) by UVVisible Spectrophotometry in Sup-port of ResponseActions under theMassachusetts ContingencyPlan (MCP)WSC-CAM Section VI B RevisionNo 1 pp 1-262010
[19] N T Joutey H Sayel W Bahafid and N E Ghachtouli ldquoMech-anisms of hexavalent chromium resistance and removal bymicroorganismsrdquoReviews of Environmental Contamination andToxicology vol 233 pp 45ndash69 2015
[20] F X Han Y Su B B Maruthi Sridhar and D L Monts ldquoDis-tribution transformation and bioavailability of trivalent andhexavalent chromium in contaminated soilrdquo Plant and Soil vol265 no 1-2 pp 243ndash252 2004
[21] APHA AWWA and WEF Standard Methods for the Exami-nation of Water and Wastewater 21st edition APHA AWWAWEF Washington DC (2005) and (2011)
[22] N J Miller and C J Miller ldquoStatistics and chemometrics foranalytical chemistry sixth editionrdquo Pearson Education Limitedpp 110ndash150 2010
[23] M E Mahmoud M M Osman O F Hafez and E Elmel-egy ldquoRemoval and preconcentration of lead (II) copper (II)chromium (III) and iron (III) from wastewaters by surfacedeveloped alumina adsorbents with immobilized 1-nitroso-2-naphtholrdquo Journal of Hazardous Materials vol 173 no 1-3 pp349ndash357 2010
[24] H I Abdel-Shafy W Hegemann and E Genschow ldquoFate ofheavy metals in the leather tanning industrial wastewater usingan anaerobic processrdquo Environmental Management and Healthvol 6 no 2 pp 28ndash33 1995
[25] H Egli et al ldquoSampling and handling of samplesrdquo IUPAC vol75 pp 1097ndash1106 2003
K = Kombolcha W = wastewater sample S = soil sample PLS = plant leaf sample and PRS = plant root sample
23 Validation of the Method The metal concentration andspeciation were determined at optimum conditions of ratioof acids mixtures time of digestion and temperature byvarying one condition and keeping others constantThen thedetermination of the concentration of total Cr Cr(III) andCr(VI) was done using the optimized parameters The spik-ing experiments were analyzed by using standard referencematerialsThe validations of themethodwere done by adding1mLof reference standardmaterial towastewater lettuce andsoil samples The digestion was carried out side by side withthe sample digestion For the case of Cr(VI) on the abovespiked samples 1mL of prepared diphenyl carbazide solutionwas added and a red violet color was immediately developedFrom the absorbance reading the amount of Cr(VI) wasobtained using calibration curve
24 Digestion of Lettuce Plant and Soil Samples Applyingthe optimized condition 05 g of air dried and homogenizedlettuce plant and soil samples were transferred into 250mLdifferent round bottom flasks separately Then 7mL of amixture of HNO3 (69ndash72) HClO4 (70) and H2O2 (30)with a volume ratio of 4 2 1 (vv) was added to the lettuceplant sample whereas 6mL of modified aqua-regia (3 1 05)ratio of HCl (36) HNO3 and H2O2 was added to thesoil sample Then the mixture was digested on a Kjeldahldigestion apparatus fitting the flask to a reflux condenserTheoptimum temperature and digestion time for lettuce samplewere 270∘C and 2 hr and for soil sample were 270∘C and3 hr The digested samples were allowed to cool to roomtemperature for 10min To these cooled solutions 15mL ofdistilled water was added to dilute the acid concentrationThen the solutions were filtered with Whatman filter paper(110mm diameter) into 50mL volumetric flask The roundbottom flask was rinsed subsequently with 5mL distilledwater until the total volume reached around 45mL To thisfinal solution 2 HNO3 was added and filled to the markThe digested solutions were carried out in triplicate for bothsamples Digestions of reagent blanks for both samples werealso performed in parallel with the samples The digestedsamples were kept in a refrigerator for 12 hrThen the amountof total Cr in the sample solutions was determined [15]
25 Digestion of Wastewater Samples 50mL of each of thefiltered water samples was transferred into different 250mLround bottomflasks To this sample 10mL of aqua-regia (3 1)ratio of 37HCl to (69ndash72)HNO3 and 2mLofH2O2 (30)were added and the mixture was digested on a Kjeldahl blockdigestion apparatus fitting the flask to a reflux condenser atthe optimized conditions (with programmed temperature at300∘C for 2 hr until 10mL of the water sample remains) Thenext steps were similar to the steps applied in plant and soilsamples The digested samples were kept in a refrigeratorfor 12 hr until the levels of the total Cr and Cr(VI) weredetermined [16]
26 Analysis of Wastewater Plant and Soil Samples forTotal Cr and Cr(VI) Levels The instruments were calibratedusing four series of working standards for FAAS (BUCKSCIENTIFIC MODEL 210 VGP USA) and five for UVVisspectrophotometer (Intech-Model-I-290 USA) The work-ing standard solutions of Cr were prepared freshly from1000 ppm stock solution (Buck Scientific 9999) by dilutingthe intermediated standard solution (25mgL) The instru-ment was calibrated using five series of working standards forUVVis spectrophotometer A solution of 1mL of diphenylcarbazide was added to each sample and working standardsolution Similarly the pH of the spiked sample solution wasadjusted to the desired value (pH = 1) at which the recoveryof Cr(VI) is the highest Then the equilibrium concentrationof Cr(VI) in the organic phase was determined spectropho-tometrically by measuring the absorbance of Cr(VI)-DPC(diphenyl carbazide) complex at 540 nm [17]
27 Statistical Analysis Statistical analyses were carried outby one-way ANOVA of Tamhane and LSD comparison posthoc tests Significant differences were accepted at 119901 lt 005The analyses were performed using SPSS Statistics software(version 160 for Windows 7)
3 Results and Discussion
31 Recovery of the Method As shown in Tables 1 and 2the results of percentage recoveries of total Cr and Cr(VI)
4 Advances in Chemistry
Table 2 Recovery test of Cr(VI) using UV analysis for tannery wastewater soil and plant samples
Industry Site Amount added (ppm) Amount recorded (ppm) Recovery ()
Table 3 Distribution of total Cr Cr(VI) and Cr(III) concentration (mean plusmn SD mgL for wastewater samples and 120583gg for soil and plantsamples) in different sites of Kombolcha leather industry
Industry Site [Cr] [Cr(VI)] [Cr(III)] through difference
a = mgL for wastewater samples b = 120583gkg for soil and plant samples
for wastewater lettuce plant and soil samples were withinthe acceptable range [18] The average percent recoverieswere 981 plusmn 63 for wastewater 941 plusmn 281 for lettuce plantand 946 plusmn 41 for soil samples using FAAS Therefore thisverifies that the optimized digestion procedure was valid forwastewater lettuce plant and soil sample analysis
The average percent recoveries of Cr(VI) for wastewaterlettuce plant and soil samples were 9464plusmn334 9100plusmn281and 9240plusmn763 respectivelyThis verifies that the procedureswere valid for wastewater lettuce plant and soil samplesanalysis
32 Determination of Total Cr Cr(VI) and Cr(III) In thisstudy the total Cr concentrations in wastewater soil andplant samples at different sites of the industry were deter-mined by FAAS Significant amount of total Cr was releasedat the discharging point The main source of total Cr in thenearby water system comes from the tanning effluent Thisis because even after the wastewater joins the river water theconcentration of total Cr was decreasing slightlyThe effluentwas much concentrated with total Cr at the discharging pointand decreased as it flows down from the discharging point
In the analysis of Cr(VI) using UVVis a sharp peak wasobserved at wavelength of 540 nm due to absorption of lightby Cr(VI)-DPC complexThe influences of pH on the signalsof Cr(VI) in all samples were obtained in the range of pH1 to pH 4 The results showed that the highest absorbancewas obtained at pH 1 Therefore pH 1 was chosen as the
optimum pH value for all measurements The high load ofgreen coloration of the sample was due to the presence ofhigh Cr(III) aqua complex The concentration of Cr(III) wascalculated by the difference of Cr(VI) concentration fromthe total Cr content The distribution of total Cr Cr(VI)and Cr(III) concentrations in the wastewater soil and lettuceplant samples at different sites and different distances ispresented in Table 3
The maximum and minimum concentrations of total CrCr(III) and Cr(VI) were 82387 plusmn 1362 and 124 plusmn 0482182186 plusmn 13569 and 1207 plusmn 04772 and 2014 plusmn 0051 and0033 plusmn 00049 respectively The maximum concentrationswere obtained at the discharging point of wastewater samplewhile the minimum was found at the downstream waterThe reason for the maximum value at the discharging pointwas due to the use of high amount of chrome salt Besidesthe concentrations of total Cr Cr(VI) and Cr(III) weredramatically decreased from the discharging point to thejunction point These might be due to adsorption of wastesby various plants in the watershed and dilution of the wastewith river water [19]
From the total Cr concentration it was found thatCr(VI) accounts for 024ndash266 while Cr(III) accountsfor 9734ndash9976 of the pollution status of the wastewaterThe reason for the increased Cr(VI) concentration in thewastewater compared to its total Cr concentration might bedue to the pH (acidity) of the wasteThe pH of the wastewatersamples measured was found to be 36 to 47 before junction
Advances in Chemistry 5
KW1 KW2 KW3
Average concentration in ppm
Average concentration in ppm
0
200
400
600
800
1000
KW4
(a)
Average concentration in ppm
Average concentration in ppmKW2 KW3 KW4
0
5
10
15
20
25
(b)Figure 3 Total Cr concentration in wastewater ((a) = average concentration of all wastewater samples (b) = average concentration fromjunction to downstream wastewater samples)
and 5 to 58 after junction This showed that the wastewaterwas acidic which contributes to the increased accumulationof Cr(VI) in the study areas It is because Cr(VI) is morestable and exists in much proportion in the acidic mediumas HCrO4
minus (1 lt pH lt 7) Similarly the concentration ofCr(VI) was found to be 0075 in soil and 073ndash122 inplant samples As a result Cr(III) is widespread in all samplescompared with Cr(VI) which is consistent with the onedescribed by Onchoke and Sasu [16]
33 The Potential Pollution Effect of the Kombolcha TanneryWastewater The determinations of the levels of total CrCr(VI) and Cr(III) in the wastewater soil and plant samplesaround the area of the leather industry were performed toassess the influence of the tannery effluent on the surround-ing environment The levels of both Cr(III) and Cr(VI) weredecreased from discharge point to downstream wastewatersamples as shown in Figures 3 and 4 The distribution ofboth Cr(III) and Cr(VI) in the wastewaters follows the orderKW1gtKW2gtKW3gtKW4 The concentrations of Cr(VI) inplant and soil samples were much lower than Cr(III) Thisis due to the fact that chrome (Cr(III) salts) is used whichcontains about 25 Cr2O3 with 33 basicity [20ndash22] Basicchrome sulphate liquor is also used which is prepared byreducing the NaK dichromate in the presence of H2SO4 [23]and also in addition to this in the soil Cr(VI) interactedwith organic matters and reduced into Cr(III) As a resultthe concentration of Cr(III) is extremely higher than that ofCr(VI)
ANOVA also showed that mean concentrations of totalCr and chromium species at the discharging point in wastew-ater sample were statistically significant (119901 = 005) when
compared with other samples (from junction to downstreamwastewater soil and plant)However the post hoc descriptiveanalysis showed that the mean concentrations of total Cr andchromium species had no significant differences among allsamples except KW1
The results obtained in this research were comparedwith other reported values The amounts of total Cr atthe discharging point of Kombolcha tannery wastewaterwere higher than the values described by Homa et al(19126ndash39696mgL) [15] The concentration of Cr(III) isalso extremely higher than the reported value by Homaet al (19126ndash39374mgL) [15] Moreover the amount ofCr(VI) obtained in this study at the discharging point washigher than that of Homa et al (0ndash0322mgL) [15] In thedownstream case all chromium species were lower thanother reported values The results of this study were alsocompared with themaximumpermissible limit (01mgL) setby WHO The total Cr values in all wastewater samples werehigher than the maximum permissible limit (01mgL) set byWHOFAO
Thevalue of total Cr (226mgkg) in the soil sample of thisstudy wasmuch lower than the values reported inHoma et al(25425ndash158166mgkg) [15] as well as the permissible limit(100mgkg) by WHO and FAO The total Cr Cr(III) andCr(VI) which were obtained in the lettuce plant samples werealso lower than those reported by Homa et al (74163ndash1047373913ndash1036 and 0025ndash0113mgkg resp) [15] but total Crwas higher than the permissible level (13mgkg) by WHOand FAO
Generally chromium and chromium species released tothe environment have detrimental effects on human and ani-mal hygiene and also are not easily degraded or removed from
6 Advances in Chemistry
200
0
400
600
800
1000
0
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
KW2KW1 KW3 KW4
(a)
KW2 KW3 KW4
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
0
5
10
15
20
25
(b)Figure 4 Comparison of the concentration of Cr(VI) and Cr(III) in the wastewaters ((a) = average concentration of all wastewater samples(b) = average concentration from junction to downstream wastewater samples)
the environment Some of them are gastric cancer disabilitygenetic modification and kidney and liver problems [24ndash26] This study shows that huge amounts of chromium andchromium species were released to the surrounding riverwater irrigated land and plants Even if the river water dilutesthe waste it does not mean that it is harmlessThis is becauseit is accumulated in the environment which is due to itsinteraction with different substances and found either as aprecipitate or in the food chain
4 Conclusions
The levels of total Cr Cr(VI) and Cr(III) in tannery wastew-ater soil and lettuce plant samples were determined by FAASand UVVis and through difference respectively The totalCr and Cr species determined in the sample collected fromthe discharging point were muchmore concentrated than thedownstream sample (at a distance of 400m from the junctionpoint) The concentration of Cr decreases from dischargepoint to downstream sample The decrease in concentrationwas due to adsorption by various plants in the watershedclassical treatment method and dilution as the wastewaterjoins the river The amounts of total Cr and Cr species werebeyond the permissible limit set by WHO and FAO
The amount of total Cr Cr(VI) and Cr(III) whichwas entering into the river was actually not too much as
compared to its level in the discharge point of the specifiedsite But the result showed that a remarkable eliminationof total Cr Cr(VI) and Cr(III) has not been achieved bythis leather industry as its level was not much decreasedwhen entered into the water systems Since the dischargedchromium wastes entered to the nearby Kete River this inturn caused the contamination of the big river Borkena Asa result this contamination can increase the accumulationof chromium in the river water and the surroundings andbring a potential adverse impact to the population around itTherefore effective treatment methods should be applied tothe wastewater to protect the ecosystem
Conflicts of Interest
The authors declare that there are no conflicts of interest
Acknowledgments
Theauthors take this opportunity to express their gratitude toall those whomotivated encouraged and helped them in thisresearch work Again their deepest thanks go to Departmentof Chemistry University of Gondar for providing them withthe necessarymaterials and facilities to conduct this researchAbove all they would like to give hearty thanks to theirfamilies for their care and moral support for continuous loveand support which strengthen them
Advances in Chemistry 7
References
[1] N Unlu and M Ersoz ldquoAdsorption characteristics of heavymetal ions onto a low cost biopolymeric sorbent from aqueoussolutionsrdquo Journal of Hazardous Materials vol 136 no 2 pp272ndash280 2006
[2] T Watanabe and T Hirayama ldquoGenotoxicity of soilrdquo Journal ofHealth Science vol 47 no 5 pp 433ndash438 2001
[3] PAWhite andLDClaxton ldquoMutagens in contaminated soil areviewrdquoMutation ResearchmdashReviews in Mutation Research vol567 no 2-3 pp 227ndash345 2004
[4] PQuevauviller E AMaier andBGriepink ldquoQuality assurancefor environmental analysisrdquo Techniques and Instrumentation inAnalytical Chemistry vol 17 no C pp 1ndash25 1995
[5] W EMotzer SM Testa J Guertin and F T StaninChromium(VI) Hand Book CRC Press New York NY USA 1st edition2005
[6] D Mohan U Charles and J Pittman ldquoActivated carbons andlow cost adsorbents for remediation of tri and hexavalentchromium fromwaterrdquo Journal of HazardousMaterials vol 137no 2 pp 762ndash811 2006
[7] J Barnhart ldquoOccurrences uses and properties of chromiumrdquoRegulatory Toxicology and Pharmacology vol 26 no 1 pp S3ndashS7 1997
[8] B Jankiewicz and B Ptaszynski ldquoDetermination of chromiumin soil of lody gardens polishrdquo Journal of Environmental Studiesvol 14 no 6 pp 869ndash875 2005
[9] V Gomez and M P Callao ldquoChromium determination andspeciation since 2000rdquo TrACmdashTrends in Analytical Chemistryvol 25 no 10 pp 1006ndash1015 2006
[10] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[11] P Venkateswarlu and M V Ratnam ldquoRemoval of chromiumfrom an aqueous solution using Azadirachta indica (Neem)leaf powder as an adsorbentrdquo International Journal of PhysicalSciences vol 2 no 8 pp 188ndash195 2007
[12] J Mwamburi ldquoChromium distribution and spatial variations inthe finer sediment grain size fraction and unfractioned surficialsediments on Nyanza Gulf of Lake Victoria (East Africa)rdquoJournal of Waste Management vol 2016 pp 1ndash15 2016
[13] J Lopez-LunaM C Gonzalez-Chavez F J Esparza-Garca andR Rodrıguez-Vazquez ldquoFractionation and availability of heavymetals in tannery sludge-amended soil and toxicity assessmenton the fully-grown Phaseolus vulgaris cultivarsrdquo Journal ofEnvironmental Science and Health - Part A ToxicHazardousSubstances and Environmental Engineering vol 47 no 3 pp405ndash419 2012
[14] A M Zayed and N Terry ldquoChromium in the environmentfactors affecting biological remediationrdquoPlant and Soil vol 249no 1 pp 139ndash156 2003
[15] D Homa E Haile and A P Washe ldquoDetermination of spatialchromiumcontamination of the environment around industrialzonesrdquo International Journal of Analytical Chemistry vol 2016Article ID 7214932 7 pages 2016
[16] K K Onchoke and S A Sasu ldquoDetermination of HexavalentChromium (Cr(VI)) concentrations via ion chromatographyand UV-Vis spectrophotometry in samples collected fromnacogdoches wastewater treatment plant East Texas (USA)rdquoAdvances in Environmental Chemistry vol 2016 pp 1ndash10 2016
[17] A K Shanker C Cervantes H Loza-Tavera and S Avu-dainayagam ldquoChromium toxicity in plantsrdquo Environment Inter-national vol 31 no 5 pp 739ndash753 2005
[18] Massachusetts Department of Environmental Protection Bu-reau of Waste Site Cleanup Quality Control Requirementsand Performance Standards for the Analysis of HexavalentChromium Cr(VI) by UVVisible Spectrophotometry in Sup-port of ResponseActions under theMassachusetts ContingencyPlan (MCP)WSC-CAM Section VI B RevisionNo 1 pp 1-262010
[19] N T Joutey H Sayel W Bahafid and N E Ghachtouli ldquoMech-anisms of hexavalent chromium resistance and removal bymicroorganismsrdquoReviews of Environmental Contamination andToxicology vol 233 pp 45ndash69 2015
[20] F X Han Y Su B B Maruthi Sridhar and D L Monts ldquoDis-tribution transformation and bioavailability of trivalent andhexavalent chromium in contaminated soilrdquo Plant and Soil vol265 no 1-2 pp 243ndash252 2004
[21] APHA AWWA and WEF Standard Methods for the Exami-nation of Water and Wastewater 21st edition APHA AWWAWEF Washington DC (2005) and (2011)
[22] N J Miller and C J Miller ldquoStatistics and chemometrics foranalytical chemistry sixth editionrdquo Pearson Education Limitedpp 110ndash150 2010
[23] M E Mahmoud M M Osman O F Hafez and E Elmel-egy ldquoRemoval and preconcentration of lead (II) copper (II)chromium (III) and iron (III) from wastewaters by surfacedeveloped alumina adsorbents with immobilized 1-nitroso-2-naphtholrdquo Journal of Hazardous Materials vol 173 no 1-3 pp349ndash357 2010
[24] H I Abdel-Shafy W Hegemann and E Genschow ldquoFate ofheavy metals in the leather tanning industrial wastewater usingan anaerobic processrdquo Environmental Management and Healthvol 6 no 2 pp 28ndash33 1995
[25] H Egli et al ldquoSampling and handling of samplesrdquo IUPAC vol75 pp 1097ndash1106 2003
Table 3 Distribution of total Cr Cr(VI) and Cr(III) concentration (mean plusmn SD mgL for wastewater samples and 120583gg for soil and plantsamples) in different sites of Kombolcha leather industry
Industry Site [Cr] [Cr(VI)] [Cr(III)] through difference
a = mgL for wastewater samples b = 120583gkg for soil and plant samples
for wastewater lettuce plant and soil samples were withinthe acceptable range [18] The average percent recoverieswere 981 plusmn 63 for wastewater 941 plusmn 281 for lettuce plantand 946 plusmn 41 for soil samples using FAAS Therefore thisverifies that the optimized digestion procedure was valid forwastewater lettuce plant and soil sample analysis
The average percent recoveries of Cr(VI) for wastewaterlettuce plant and soil samples were 9464plusmn334 9100plusmn281and 9240plusmn763 respectivelyThis verifies that the procedureswere valid for wastewater lettuce plant and soil samplesanalysis
32 Determination of Total Cr Cr(VI) and Cr(III) In thisstudy the total Cr concentrations in wastewater soil andplant samples at different sites of the industry were deter-mined by FAAS Significant amount of total Cr was releasedat the discharging point The main source of total Cr in thenearby water system comes from the tanning effluent Thisis because even after the wastewater joins the river water theconcentration of total Cr was decreasing slightlyThe effluentwas much concentrated with total Cr at the discharging pointand decreased as it flows down from the discharging point
In the analysis of Cr(VI) using UVVis a sharp peak wasobserved at wavelength of 540 nm due to absorption of lightby Cr(VI)-DPC complexThe influences of pH on the signalsof Cr(VI) in all samples were obtained in the range of pH1 to pH 4 The results showed that the highest absorbancewas obtained at pH 1 Therefore pH 1 was chosen as the
optimum pH value for all measurements The high load ofgreen coloration of the sample was due to the presence ofhigh Cr(III) aqua complex The concentration of Cr(III) wascalculated by the difference of Cr(VI) concentration fromthe total Cr content The distribution of total Cr Cr(VI)and Cr(III) concentrations in the wastewater soil and lettuceplant samples at different sites and different distances ispresented in Table 3
The maximum and minimum concentrations of total CrCr(III) and Cr(VI) were 82387 plusmn 1362 and 124 plusmn 0482182186 plusmn 13569 and 1207 plusmn 04772 and 2014 plusmn 0051 and0033 plusmn 00049 respectively The maximum concentrationswere obtained at the discharging point of wastewater samplewhile the minimum was found at the downstream waterThe reason for the maximum value at the discharging pointwas due to the use of high amount of chrome salt Besidesthe concentrations of total Cr Cr(VI) and Cr(III) weredramatically decreased from the discharging point to thejunction point These might be due to adsorption of wastesby various plants in the watershed and dilution of the wastewith river water [19]
From the total Cr concentration it was found thatCr(VI) accounts for 024ndash266 while Cr(III) accountsfor 9734ndash9976 of the pollution status of the wastewaterThe reason for the increased Cr(VI) concentration in thewastewater compared to its total Cr concentration might bedue to the pH (acidity) of the wasteThe pH of the wastewatersamples measured was found to be 36 to 47 before junction
Advances in Chemistry 5
KW1 KW2 KW3
Average concentration in ppm
Average concentration in ppm
0
200
400
600
800
1000
KW4
(a)
Average concentration in ppm
Average concentration in ppmKW2 KW3 KW4
0
5
10
15
20
25
(b)Figure 3 Total Cr concentration in wastewater ((a) = average concentration of all wastewater samples (b) = average concentration fromjunction to downstream wastewater samples)
and 5 to 58 after junction This showed that the wastewaterwas acidic which contributes to the increased accumulationof Cr(VI) in the study areas It is because Cr(VI) is morestable and exists in much proportion in the acidic mediumas HCrO4
minus (1 lt pH lt 7) Similarly the concentration ofCr(VI) was found to be 0075 in soil and 073ndash122 inplant samples As a result Cr(III) is widespread in all samplescompared with Cr(VI) which is consistent with the onedescribed by Onchoke and Sasu [16]
33 The Potential Pollution Effect of the Kombolcha TanneryWastewater The determinations of the levels of total CrCr(VI) and Cr(III) in the wastewater soil and plant samplesaround the area of the leather industry were performed toassess the influence of the tannery effluent on the surround-ing environment The levels of both Cr(III) and Cr(VI) weredecreased from discharge point to downstream wastewatersamples as shown in Figures 3 and 4 The distribution ofboth Cr(III) and Cr(VI) in the wastewaters follows the orderKW1gtKW2gtKW3gtKW4 The concentrations of Cr(VI) inplant and soil samples were much lower than Cr(III) Thisis due to the fact that chrome (Cr(III) salts) is used whichcontains about 25 Cr2O3 with 33 basicity [20ndash22] Basicchrome sulphate liquor is also used which is prepared byreducing the NaK dichromate in the presence of H2SO4 [23]and also in addition to this in the soil Cr(VI) interactedwith organic matters and reduced into Cr(III) As a resultthe concentration of Cr(III) is extremely higher than that ofCr(VI)
ANOVA also showed that mean concentrations of totalCr and chromium species at the discharging point in wastew-ater sample were statistically significant (119901 = 005) when
compared with other samples (from junction to downstreamwastewater soil and plant)However the post hoc descriptiveanalysis showed that the mean concentrations of total Cr andchromium species had no significant differences among allsamples except KW1
The results obtained in this research were comparedwith other reported values The amounts of total Cr atthe discharging point of Kombolcha tannery wastewaterwere higher than the values described by Homa et al(19126ndash39696mgL) [15] The concentration of Cr(III) isalso extremely higher than the reported value by Homaet al (19126ndash39374mgL) [15] Moreover the amount ofCr(VI) obtained in this study at the discharging point washigher than that of Homa et al (0ndash0322mgL) [15] In thedownstream case all chromium species were lower thanother reported values The results of this study were alsocompared with themaximumpermissible limit (01mgL) setby WHO The total Cr values in all wastewater samples werehigher than the maximum permissible limit (01mgL) set byWHOFAO
Thevalue of total Cr (226mgkg) in the soil sample of thisstudy wasmuch lower than the values reported inHoma et al(25425ndash158166mgkg) [15] as well as the permissible limit(100mgkg) by WHO and FAO The total Cr Cr(III) andCr(VI) which were obtained in the lettuce plant samples werealso lower than those reported by Homa et al (74163ndash1047373913ndash1036 and 0025ndash0113mgkg resp) [15] but total Crwas higher than the permissible level (13mgkg) by WHOand FAO
Generally chromium and chromium species released tothe environment have detrimental effects on human and ani-mal hygiene and also are not easily degraded or removed from
6 Advances in Chemistry
200
0
400
600
800
1000
0
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
KW2KW1 KW3 KW4
(a)
KW2 KW3 KW4
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
0
5
10
15
20
25
(b)Figure 4 Comparison of the concentration of Cr(VI) and Cr(III) in the wastewaters ((a) = average concentration of all wastewater samples(b) = average concentration from junction to downstream wastewater samples)
the environment Some of them are gastric cancer disabilitygenetic modification and kidney and liver problems [24ndash26] This study shows that huge amounts of chromium andchromium species were released to the surrounding riverwater irrigated land and plants Even if the river water dilutesthe waste it does not mean that it is harmlessThis is becauseit is accumulated in the environment which is due to itsinteraction with different substances and found either as aprecipitate or in the food chain
4 Conclusions
The levels of total Cr Cr(VI) and Cr(III) in tannery wastew-ater soil and lettuce plant samples were determined by FAASand UVVis and through difference respectively The totalCr and Cr species determined in the sample collected fromthe discharging point were muchmore concentrated than thedownstream sample (at a distance of 400m from the junctionpoint) The concentration of Cr decreases from dischargepoint to downstream sample The decrease in concentrationwas due to adsorption by various plants in the watershedclassical treatment method and dilution as the wastewaterjoins the river The amounts of total Cr and Cr species werebeyond the permissible limit set by WHO and FAO
The amount of total Cr Cr(VI) and Cr(III) whichwas entering into the river was actually not too much as
compared to its level in the discharge point of the specifiedsite But the result showed that a remarkable eliminationof total Cr Cr(VI) and Cr(III) has not been achieved bythis leather industry as its level was not much decreasedwhen entered into the water systems Since the dischargedchromium wastes entered to the nearby Kete River this inturn caused the contamination of the big river Borkena Asa result this contamination can increase the accumulationof chromium in the river water and the surroundings andbring a potential adverse impact to the population around itTherefore effective treatment methods should be applied tothe wastewater to protect the ecosystem
Conflicts of Interest
The authors declare that there are no conflicts of interest
Acknowledgments
Theauthors take this opportunity to express their gratitude toall those whomotivated encouraged and helped them in thisresearch work Again their deepest thanks go to Departmentof Chemistry University of Gondar for providing them withthe necessarymaterials and facilities to conduct this researchAbove all they would like to give hearty thanks to theirfamilies for their care and moral support for continuous loveand support which strengthen them
Advances in Chemistry 7
References
[1] N Unlu and M Ersoz ldquoAdsorption characteristics of heavymetal ions onto a low cost biopolymeric sorbent from aqueoussolutionsrdquo Journal of Hazardous Materials vol 136 no 2 pp272ndash280 2006
[2] T Watanabe and T Hirayama ldquoGenotoxicity of soilrdquo Journal ofHealth Science vol 47 no 5 pp 433ndash438 2001
[3] PAWhite andLDClaxton ldquoMutagens in contaminated soil areviewrdquoMutation ResearchmdashReviews in Mutation Research vol567 no 2-3 pp 227ndash345 2004
[4] PQuevauviller E AMaier andBGriepink ldquoQuality assurancefor environmental analysisrdquo Techniques and Instrumentation inAnalytical Chemistry vol 17 no C pp 1ndash25 1995
[5] W EMotzer SM Testa J Guertin and F T StaninChromium(VI) Hand Book CRC Press New York NY USA 1st edition2005
[6] D Mohan U Charles and J Pittman ldquoActivated carbons andlow cost adsorbents for remediation of tri and hexavalentchromium fromwaterrdquo Journal of HazardousMaterials vol 137no 2 pp 762ndash811 2006
[7] J Barnhart ldquoOccurrences uses and properties of chromiumrdquoRegulatory Toxicology and Pharmacology vol 26 no 1 pp S3ndashS7 1997
[8] B Jankiewicz and B Ptaszynski ldquoDetermination of chromiumin soil of lody gardens polishrdquo Journal of Environmental Studiesvol 14 no 6 pp 869ndash875 2005
[9] V Gomez and M P Callao ldquoChromium determination andspeciation since 2000rdquo TrACmdashTrends in Analytical Chemistryvol 25 no 10 pp 1006ndash1015 2006
[10] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[11] P Venkateswarlu and M V Ratnam ldquoRemoval of chromiumfrom an aqueous solution using Azadirachta indica (Neem)leaf powder as an adsorbentrdquo International Journal of PhysicalSciences vol 2 no 8 pp 188ndash195 2007
[12] J Mwamburi ldquoChromium distribution and spatial variations inthe finer sediment grain size fraction and unfractioned surficialsediments on Nyanza Gulf of Lake Victoria (East Africa)rdquoJournal of Waste Management vol 2016 pp 1ndash15 2016
[13] J Lopez-LunaM C Gonzalez-Chavez F J Esparza-Garca andR Rodrıguez-Vazquez ldquoFractionation and availability of heavymetals in tannery sludge-amended soil and toxicity assessmenton the fully-grown Phaseolus vulgaris cultivarsrdquo Journal ofEnvironmental Science and Health - Part A ToxicHazardousSubstances and Environmental Engineering vol 47 no 3 pp405ndash419 2012
[14] A M Zayed and N Terry ldquoChromium in the environmentfactors affecting biological remediationrdquoPlant and Soil vol 249no 1 pp 139ndash156 2003
[15] D Homa E Haile and A P Washe ldquoDetermination of spatialchromiumcontamination of the environment around industrialzonesrdquo International Journal of Analytical Chemistry vol 2016Article ID 7214932 7 pages 2016
[16] K K Onchoke and S A Sasu ldquoDetermination of HexavalentChromium (Cr(VI)) concentrations via ion chromatographyand UV-Vis spectrophotometry in samples collected fromnacogdoches wastewater treatment plant East Texas (USA)rdquoAdvances in Environmental Chemistry vol 2016 pp 1ndash10 2016
[17] A K Shanker C Cervantes H Loza-Tavera and S Avu-dainayagam ldquoChromium toxicity in plantsrdquo Environment Inter-national vol 31 no 5 pp 739ndash753 2005
[18] Massachusetts Department of Environmental Protection Bu-reau of Waste Site Cleanup Quality Control Requirementsand Performance Standards for the Analysis of HexavalentChromium Cr(VI) by UVVisible Spectrophotometry in Sup-port of ResponseActions under theMassachusetts ContingencyPlan (MCP)WSC-CAM Section VI B RevisionNo 1 pp 1-262010
[19] N T Joutey H Sayel W Bahafid and N E Ghachtouli ldquoMech-anisms of hexavalent chromium resistance and removal bymicroorganismsrdquoReviews of Environmental Contamination andToxicology vol 233 pp 45ndash69 2015
[20] F X Han Y Su B B Maruthi Sridhar and D L Monts ldquoDis-tribution transformation and bioavailability of trivalent andhexavalent chromium in contaminated soilrdquo Plant and Soil vol265 no 1-2 pp 243ndash252 2004
[21] APHA AWWA and WEF Standard Methods for the Exami-nation of Water and Wastewater 21st edition APHA AWWAWEF Washington DC (2005) and (2011)
[22] N J Miller and C J Miller ldquoStatistics and chemometrics foranalytical chemistry sixth editionrdquo Pearson Education Limitedpp 110ndash150 2010
[23] M E Mahmoud M M Osman O F Hafez and E Elmel-egy ldquoRemoval and preconcentration of lead (II) copper (II)chromium (III) and iron (III) from wastewaters by surfacedeveloped alumina adsorbents with immobilized 1-nitroso-2-naphtholrdquo Journal of Hazardous Materials vol 173 no 1-3 pp349ndash357 2010
[24] H I Abdel-Shafy W Hegemann and E Genschow ldquoFate ofheavy metals in the leather tanning industrial wastewater usingan anaerobic processrdquo Environmental Management and Healthvol 6 no 2 pp 28ndash33 1995
[25] H Egli et al ldquoSampling and handling of samplesrdquo IUPAC vol75 pp 1097ndash1106 2003
(b)Figure 3 Total Cr concentration in wastewater ((a) = average concentration of all wastewater samples (b) = average concentration fromjunction to downstream wastewater samples)
and 5 to 58 after junction This showed that the wastewaterwas acidic which contributes to the increased accumulationof Cr(VI) in the study areas It is because Cr(VI) is morestable and exists in much proportion in the acidic mediumas HCrO4
minus (1 lt pH lt 7) Similarly the concentration ofCr(VI) was found to be 0075 in soil and 073ndash122 inplant samples As a result Cr(III) is widespread in all samplescompared with Cr(VI) which is consistent with the onedescribed by Onchoke and Sasu [16]
33 The Potential Pollution Effect of the Kombolcha TanneryWastewater The determinations of the levels of total CrCr(VI) and Cr(III) in the wastewater soil and plant samplesaround the area of the leather industry were performed toassess the influence of the tannery effluent on the surround-ing environment The levels of both Cr(III) and Cr(VI) weredecreased from discharge point to downstream wastewatersamples as shown in Figures 3 and 4 The distribution ofboth Cr(III) and Cr(VI) in the wastewaters follows the orderKW1gtKW2gtKW3gtKW4 The concentrations of Cr(VI) inplant and soil samples were much lower than Cr(III) Thisis due to the fact that chrome (Cr(III) salts) is used whichcontains about 25 Cr2O3 with 33 basicity [20ndash22] Basicchrome sulphate liquor is also used which is prepared byreducing the NaK dichromate in the presence of H2SO4 [23]and also in addition to this in the soil Cr(VI) interactedwith organic matters and reduced into Cr(III) As a resultthe concentration of Cr(III) is extremely higher than that ofCr(VI)
ANOVA also showed that mean concentrations of totalCr and chromium species at the discharging point in wastew-ater sample were statistically significant (119901 = 005) when
compared with other samples (from junction to downstreamwastewater soil and plant)However the post hoc descriptiveanalysis showed that the mean concentrations of total Cr andchromium species had no significant differences among allsamples except KW1
The results obtained in this research were comparedwith other reported values The amounts of total Cr atthe discharging point of Kombolcha tannery wastewaterwere higher than the values described by Homa et al(19126ndash39696mgL) [15] The concentration of Cr(III) isalso extremely higher than the reported value by Homaet al (19126ndash39374mgL) [15] Moreover the amount ofCr(VI) obtained in this study at the discharging point washigher than that of Homa et al (0ndash0322mgL) [15] In thedownstream case all chromium species were lower thanother reported values The results of this study were alsocompared with themaximumpermissible limit (01mgL) setby WHO The total Cr values in all wastewater samples werehigher than the maximum permissible limit (01mgL) set byWHOFAO
Thevalue of total Cr (226mgkg) in the soil sample of thisstudy wasmuch lower than the values reported inHoma et al(25425ndash158166mgkg) [15] as well as the permissible limit(100mgkg) by WHO and FAO The total Cr Cr(III) andCr(VI) which were obtained in the lettuce plant samples werealso lower than those reported by Homa et al (74163ndash1047373913ndash1036 and 0025ndash0113mgkg resp) [15] but total Crwas higher than the permissible level (13mgkg) by WHOand FAO
Generally chromium and chromium species released tothe environment have detrimental effects on human and ani-mal hygiene and also are not easily degraded or removed from
6 Advances in Chemistry
200
0
400
600
800
1000
0
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
KW2KW1 KW3 KW4
(a)
KW2 KW3 KW4
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
0
5
10
15
20
25
(b)Figure 4 Comparison of the concentration of Cr(VI) and Cr(III) in the wastewaters ((a) = average concentration of all wastewater samples(b) = average concentration from junction to downstream wastewater samples)
the environment Some of them are gastric cancer disabilitygenetic modification and kidney and liver problems [24ndash26] This study shows that huge amounts of chromium andchromium species were released to the surrounding riverwater irrigated land and plants Even if the river water dilutesthe waste it does not mean that it is harmlessThis is becauseit is accumulated in the environment which is due to itsinteraction with different substances and found either as aprecipitate or in the food chain
4 Conclusions
The levels of total Cr Cr(VI) and Cr(III) in tannery wastew-ater soil and lettuce plant samples were determined by FAASand UVVis and through difference respectively The totalCr and Cr species determined in the sample collected fromthe discharging point were muchmore concentrated than thedownstream sample (at a distance of 400m from the junctionpoint) The concentration of Cr decreases from dischargepoint to downstream sample The decrease in concentrationwas due to adsorption by various plants in the watershedclassical treatment method and dilution as the wastewaterjoins the river The amounts of total Cr and Cr species werebeyond the permissible limit set by WHO and FAO
The amount of total Cr Cr(VI) and Cr(III) whichwas entering into the river was actually not too much as
compared to its level in the discharge point of the specifiedsite But the result showed that a remarkable eliminationof total Cr Cr(VI) and Cr(III) has not been achieved bythis leather industry as its level was not much decreasedwhen entered into the water systems Since the dischargedchromium wastes entered to the nearby Kete River this inturn caused the contamination of the big river Borkena Asa result this contamination can increase the accumulationof chromium in the river water and the surroundings andbring a potential adverse impact to the population around itTherefore effective treatment methods should be applied tothe wastewater to protect the ecosystem
Conflicts of Interest
The authors declare that there are no conflicts of interest
Acknowledgments
Theauthors take this opportunity to express their gratitude toall those whomotivated encouraged and helped them in thisresearch work Again their deepest thanks go to Departmentof Chemistry University of Gondar for providing them withthe necessarymaterials and facilities to conduct this researchAbove all they would like to give hearty thanks to theirfamilies for their care and moral support for continuous loveand support which strengthen them
Advances in Chemistry 7
References
[1] N Unlu and M Ersoz ldquoAdsorption characteristics of heavymetal ions onto a low cost biopolymeric sorbent from aqueoussolutionsrdquo Journal of Hazardous Materials vol 136 no 2 pp272ndash280 2006
[2] T Watanabe and T Hirayama ldquoGenotoxicity of soilrdquo Journal ofHealth Science vol 47 no 5 pp 433ndash438 2001
[3] PAWhite andLDClaxton ldquoMutagens in contaminated soil areviewrdquoMutation ResearchmdashReviews in Mutation Research vol567 no 2-3 pp 227ndash345 2004
[4] PQuevauviller E AMaier andBGriepink ldquoQuality assurancefor environmental analysisrdquo Techniques and Instrumentation inAnalytical Chemistry vol 17 no C pp 1ndash25 1995
[5] W EMotzer SM Testa J Guertin and F T StaninChromium(VI) Hand Book CRC Press New York NY USA 1st edition2005
[6] D Mohan U Charles and J Pittman ldquoActivated carbons andlow cost adsorbents for remediation of tri and hexavalentchromium fromwaterrdquo Journal of HazardousMaterials vol 137no 2 pp 762ndash811 2006
[7] J Barnhart ldquoOccurrences uses and properties of chromiumrdquoRegulatory Toxicology and Pharmacology vol 26 no 1 pp S3ndashS7 1997
[8] B Jankiewicz and B Ptaszynski ldquoDetermination of chromiumin soil of lody gardens polishrdquo Journal of Environmental Studiesvol 14 no 6 pp 869ndash875 2005
[9] V Gomez and M P Callao ldquoChromium determination andspeciation since 2000rdquo TrACmdashTrends in Analytical Chemistryvol 25 no 10 pp 1006ndash1015 2006
[10] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[11] P Venkateswarlu and M V Ratnam ldquoRemoval of chromiumfrom an aqueous solution using Azadirachta indica (Neem)leaf powder as an adsorbentrdquo International Journal of PhysicalSciences vol 2 no 8 pp 188ndash195 2007
[12] J Mwamburi ldquoChromium distribution and spatial variations inthe finer sediment grain size fraction and unfractioned surficialsediments on Nyanza Gulf of Lake Victoria (East Africa)rdquoJournal of Waste Management vol 2016 pp 1ndash15 2016
[13] J Lopez-LunaM C Gonzalez-Chavez F J Esparza-Garca andR Rodrıguez-Vazquez ldquoFractionation and availability of heavymetals in tannery sludge-amended soil and toxicity assessmenton the fully-grown Phaseolus vulgaris cultivarsrdquo Journal ofEnvironmental Science and Health - Part A ToxicHazardousSubstances and Environmental Engineering vol 47 no 3 pp405ndash419 2012
[14] A M Zayed and N Terry ldquoChromium in the environmentfactors affecting biological remediationrdquoPlant and Soil vol 249no 1 pp 139ndash156 2003
[15] D Homa E Haile and A P Washe ldquoDetermination of spatialchromiumcontamination of the environment around industrialzonesrdquo International Journal of Analytical Chemistry vol 2016Article ID 7214932 7 pages 2016
[16] K K Onchoke and S A Sasu ldquoDetermination of HexavalentChromium (Cr(VI)) concentrations via ion chromatographyand UV-Vis spectrophotometry in samples collected fromnacogdoches wastewater treatment plant East Texas (USA)rdquoAdvances in Environmental Chemistry vol 2016 pp 1ndash10 2016
[17] A K Shanker C Cervantes H Loza-Tavera and S Avu-dainayagam ldquoChromium toxicity in plantsrdquo Environment Inter-national vol 31 no 5 pp 739ndash753 2005
[18] Massachusetts Department of Environmental Protection Bu-reau of Waste Site Cleanup Quality Control Requirementsand Performance Standards for the Analysis of HexavalentChromium Cr(VI) by UVVisible Spectrophotometry in Sup-port of ResponseActions under theMassachusetts ContingencyPlan (MCP)WSC-CAM Section VI B RevisionNo 1 pp 1-262010
[19] N T Joutey H Sayel W Bahafid and N E Ghachtouli ldquoMech-anisms of hexavalent chromium resistance and removal bymicroorganismsrdquoReviews of Environmental Contamination andToxicology vol 233 pp 45ndash69 2015
[20] F X Han Y Su B B Maruthi Sridhar and D L Monts ldquoDis-tribution transformation and bioavailability of trivalent andhexavalent chromium in contaminated soilrdquo Plant and Soil vol265 no 1-2 pp 243ndash252 2004
[21] APHA AWWA and WEF Standard Methods for the Exami-nation of Water and Wastewater 21st edition APHA AWWAWEF Washington DC (2005) and (2011)
[22] N J Miller and C J Miller ldquoStatistics and chemometrics foranalytical chemistry sixth editionrdquo Pearson Education Limitedpp 110ndash150 2010
[23] M E Mahmoud M M Osman O F Hafez and E Elmel-egy ldquoRemoval and preconcentration of lead (II) copper (II)chromium (III) and iron (III) from wastewaters by surfacedeveloped alumina adsorbents with immobilized 1-nitroso-2-naphtholrdquo Journal of Hazardous Materials vol 173 no 1-3 pp349ndash357 2010
[24] H I Abdel-Shafy W Hegemann and E Genschow ldquoFate ofheavy metals in the leather tanning industrial wastewater usingan anaerobic processrdquo Environmental Management and Healthvol 6 no 2 pp 28ndash33 1995
[25] H Egli et al ldquoSampling and handling of samplesrdquo IUPAC vol75 pp 1097ndash1106 2003
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
KW2KW1 KW3 KW4
(a)
KW2 KW3 KW4
Average concentration in ppm Cr(VI)Average concentration in ppm Cr(III)
0
5
10
15
20
25
(b)Figure 4 Comparison of the concentration of Cr(VI) and Cr(III) in the wastewaters ((a) = average concentration of all wastewater samples(b) = average concentration from junction to downstream wastewater samples)
the environment Some of them are gastric cancer disabilitygenetic modification and kidney and liver problems [24ndash26] This study shows that huge amounts of chromium andchromium species were released to the surrounding riverwater irrigated land and plants Even if the river water dilutesthe waste it does not mean that it is harmlessThis is becauseit is accumulated in the environment which is due to itsinteraction with different substances and found either as aprecipitate or in the food chain
4 Conclusions
The levels of total Cr Cr(VI) and Cr(III) in tannery wastew-ater soil and lettuce plant samples were determined by FAASand UVVis and through difference respectively The totalCr and Cr species determined in the sample collected fromthe discharging point were muchmore concentrated than thedownstream sample (at a distance of 400m from the junctionpoint) The concentration of Cr decreases from dischargepoint to downstream sample The decrease in concentrationwas due to adsorption by various plants in the watershedclassical treatment method and dilution as the wastewaterjoins the river The amounts of total Cr and Cr species werebeyond the permissible limit set by WHO and FAO
The amount of total Cr Cr(VI) and Cr(III) whichwas entering into the river was actually not too much as
compared to its level in the discharge point of the specifiedsite But the result showed that a remarkable eliminationof total Cr Cr(VI) and Cr(III) has not been achieved bythis leather industry as its level was not much decreasedwhen entered into the water systems Since the dischargedchromium wastes entered to the nearby Kete River this inturn caused the contamination of the big river Borkena Asa result this contamination can increase the accumulationof chromium in the river water and the surroundings andbring a potential adverse impact to the population around itTherefore effective treatment methods should be applied tothe wastewater to protect the ecosystem
Conflicts of Interest
The authors declare that there are no conflicts of interest
Acknowledgments
Theauthors take this opportunity to express their gratitude toall those whomotivated encouraged and helped them in thisresearch work Again their deepest thanks go to Departmentof Chemistry University of Gondar for providing them withthe necessarymaterials and facilities to conduct this researchAbove all they would like to give hearty thanks to theirfamilies for their care and moral support for continuous loveand support which strengthen them
Advances in Chemistry 7
References
[1] N Unlu and M Ersoz ldquoAdsorption characteristics of heavymetal ions onto a low cost biopolymeric sorbent from aqueoussolutionsrdquo Journal of Hazardous Materials vol 136 no 2 pp272ndash280 2006
[2] T Watanabe and T Hirayama ldquoGenotoxicity of soilrdquo Journal ofHealth Science vol 47 no 5 pp 433ndash438 2001
[3] PAWhite andLDClaxton ldquoMutagens in contaminated soil areviewrdquoMutation ResearchmdashReviews in Mutation Research vol567 no 2-3 pp 227ndash345 2004
[4] PQuevauviller E AMaier andBGriepink ldquoQuality assurancefor environmental analysisrdquo Techniques and Instrumentation inAnalytical Chemistry vol 17 no C pp 1ndash25 1995
[5] W EMotzer SM Testa J Guertin and F T StaninChromium(VI) Hand Book CRC Press New York NY USA 1st edition2005
[6] D Mohan U Charles and J Pittman ldquoActivated carbons andlow cost adsorbents for remediation of tri and hexavalentchromium fromwaterrdquo Journal of HazardousMaterials vol 137no 2 pp 762ndash811 2006
[7] J Barnhart ldquoOccurrences uses and properties of chromiumrdquoRegulatory Toxicology and Pharmacology vol 26 no 1 pp S3ndashS7 1997
[8] B Jankiewicz and B Ptaszynski ldquoDetermination of chromiumin soil of lody gardens polishrdquo Journal of Environmental Studiesvol 14 no 6 pp 869ndash875 2005
[9] V Gomez and M P Callao ldquoChromium determination andspeciation since 2000rdquo TrACmdashTrends in Analytical Chemistryvol 25 no 10 pp 1006ndash1015 2006
[10] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[11] P Venkateswarlu and M V Ratnam ldquoRemoval of chromiumfrom an aqueous solution using Azadirachta indica (Neem)leaf powder as an adsorbentrdquo International Journal of PhysicalSciences vol 2 no 8 pp 188ndash195 2007
[12] J Mwamburi ldquoChromium distribution and spatial variations inthe finer sediment grain size fraction and unfractioned surficialsediments on Nyanza Gulf of Lake Victoria (East Africa)rdquoJournal of Waste Management vol 2016 pp 1ndash15 2016
[13] J Lopez-LunaM C Gonzalez-Chavez F J Esparza-Garca andR Rodrıguez-Vazquez ldquoFractionation and availability of heavymetals in tannery sludge-amended soil and toxicity assessmenton the fully-grown Phaseolus vulgaris cultivarsrdquo Journal ofEnvironmental Science and Health - Part A ToxicHazardousSubstances and Environmental Engineering vol 47 no 3 pp405ndash419 2012
[14] A M Zayed and N Terry ldquoChromium in the environmentfactors affecting biological remediationrdquoPlant and Soil vol 249no 1 pp 139ndash156 2003
[15] D Homa E Haile and A P Washe ldquoDetermination of spatialchromiumcontamination of the environment around industrialzonesrdquo International Journal of Analytical Chemistry vol 2016Article ID 7214932 7 pages 2016
[16] K K Onchoke and S A Sasu ldquoDetermination of HexavalentChromium (Cr(VI)) concentrations via ion chromatographyand UV-Vis spectrophotometry in samples collected fromnacogdoches wastewater treatment plant East Texas (USA)rdquoAdvances in Environmental Chemistry vol 2016 pp 1ndash10 2016
[17] A K Shanker C Cervantes H Loza-Tavera and S Avu-dainayagam ldquoChromium toxicity in plantsrdquo Environment Inter-national vol 31 no 5 pp 739ndash753 2005
[18] Massachusetts Department of Environmental Protection Bu-reau of Waste Site Cleanup Quality Control Requirementsand Performance Standards for the Analysis of HexavalentChromium Cr(VI) by UVVisible Spectrophotometry in Sup-port of ResponseActions under theMassachusetts ContingencyPlan (MCP)WSC-CAM Section VI B RevisionNo 1 pp 1-262010
[19] N T Joutey H Sayel W Bahafid and N E Ghachtouli ldquoMech-anisms of hexavalent chromium resistance and removal bymicroorganismsrdquoReviews of Environmental Contamination andToxicology vol 233 pp 45ndash69 2015
[20] F X Han Y Su B B Maruthi Sridhar and D L Monts ldquoDis-tribution transformation and bioavailability of trivalent andhexavalent chromium in contaminated soilrdquo Plant and Soil vol265 no 1-2 pp 243ndash252 2004
[21] APHA AWWA and WEF Standard Methods for the Exami-nation of Water and Wastewater 21st edition APHA AWWAWEF Washington DC (2005) and (2011)
[22] N J Miller and C J Miller ldquoStatistics and chemometrics foranalytical chemistry sixth editionrdquo Pearson Education Limitedpp 110ndash150 2010
[23] M E Mahmoud M M Osman O F Hafez and E Elmel-egy ldquoRemoval and preconcentration of lead (II) copper (II)chromium (III) and iron (III) from wastewaters by surfacedeveloped alumina adsorbents with immobilized 1-nitroso-2-naphtholrdquo Journal of Hazardous Materials vol 173 no 1-3 pp349ndash357 2010
[24] H I Abdel-Shafy W Hegemann and E Genschow ldquoFate ofheavy metals in the leather tanning industrial wastewater usingan anaerobic processrdquo Environmental Management and Healthvol 6 no 2 pp 28ndash33 1995
[25] H Egli et al ldquoSampling and handling of samplesrdquo IUPAC vol75 pp 1097ndash1106 2003
[1] N Unlu and M Ersoz ldquoAdsorption characteristics of heavymetal ions onto a low cost biopolymeric sorbent from aqueoussolutionsrdquo Journal of Hazardous Materials vol 136 no 2 pp272ndash280 2006
[2] T Watanabe and T Hirayama ldquoGenotoxicity of soilrdquo Journal ofHealth Science vol 47 no 5 pp 433ndash438 2001
[3] PAWhite andLDClaxton ldquoMutagens in contaminated soil areviewrdquoMutation ResearchmdashReviews in Mutation Research vol567 no 2-3 pp 227ndash345 2004
[4] PQuevauviller E AMaier andBGriepink ldquoQuality assurancefor environmental analysisrdquo Techniques and Instrumentation inAnalytical Chemistry vol 17 no C pp 1ndash25 1995
[5] W EMotzer SM Testa J Guertin and F T StaninChromium(VI) Hand Book CRC Press New York NY USA 1st edition2005
[6] D Mohan U Charles and J Pittman ldquoActivated carbons andlow cost adsorbents for remediation of tri and hexavalentchromium fromwaterrdquo Journal of HazardousMaterials vol 137no 2 pp 762ndash811 2006
[7] J Barnhart ldquoOccurrences uses and properties of chromiumrdquoRegulatory Toxicology and Pharmacology vol 26 no 1 pp S3ndashS7 1997
[8] B Jankiewicz and B Ptaszynski ldquoDetermination of chromiumin soil of lody gardens polishrdquo Journal of Environmental Studiesvol 14 no 6 pp 869ndash875 2005
[9] V Gomez and M P Callao ldquoChromium determination andspeciation since 2000rdquo TrACmdashTrends in Analytical Chemistryvol 25 no 10 pp 1006ndash1015 2006
[10] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[11] P Venkateswarlu and M V Ratnam ldquoRemoval of chromiumfrom an aqueous solution using Azadirachta indica (Neem)leaf powder as an adsorbentrdquo International Journal of PhysicalSciences vol 2 no 8 pp 188ndash195 2007
[12] J Mwamburi ldquoChromium distribution and spatial variations inthe finer sediment grain size fraction and unfractioned surficialsediments on Nyanza Gulf of Lake Victoria (East Africa)rdquoJournal of Waste Management vol 2016 pp 1ndash15 2016
[13] J Lopez-LunaM C Gonzalez-Chavez F J Esparza-Garca andR Rodrıguez-Vazquez ldquoFractionation and availability of heavymetals in tannery sludge-amended soil and toxicity assessmenton the fully-grown Phaseolus vulgaris cultivarsrdquo Journal ofEnvironmental Science and Health - Part A ToxicHazardousSubstances and Environmental Engineering vol 47 no 3 pp405ndash419 2012
[14] A M Zayed and N Terry ldquoChromium in the environmentfactors affecting biological remediationrdquoPlant and Soil vol 249no 1 pp 139ndash156 2003
[15] D Homa E Haile and A P Washe ldquoDetermination of spatialchromiumcontamination of the environment around industrialzonesrdquo International Journal of Analytical Chemistry vol 2016Article ID 7214932 7 pages 2016
[16] K K Onchoke and S A Sasu ldquoDetermination of HexavalentChromium (Cr(VI)) concentrations via ion chromatographyand UV-Vis spectrophotometry in samples collected fromnacogdoches wastewater treatment plant East Texas (USA)rdquoAdvances in Environmental Chemistry vol 2016 pp 1ndash10 2016
[17] A K Shanker C Cervantes H Loza-Tavera and S Avu-dainayagam ldquoChromium toxicity in plantsrdquo Environment Inter-national vol 31 no 5 pp 739ndash753 2005
[18] Massachusetts Department of Environmental Protection Bu-reau of Waste Site Cleanup Quality Control Requirementsand Performance Standards for the Analysis of HexavalentChromium Cr(VI) by UVVisible Spectrophotometry in Sup-port of ResponseActions under theMassachusetts ContingencyPlan (MCP)WSC-CAM Section VI B RevisionNo 1 pp 1-262010
[19] N T Joutey H Sayel W Bahafid and N E Ghachtouli ldquoMech-anisms of hexavalent chromium resistance and removal bymicroorganismsrdquoReviews of Environmental Contamination andToxicology vol 233 pp 45ndash69 2015
[20] F X Han Y Su B B Maruthi Sridhar and D L Monts ldquoDis-tribution transformation and bioavailability of trivalent andhexavalent chromium in contaminated soilrdquo Plant and Soil vol265 no 1-2 pp 243ndash252 2004
[21] APHA AWWA and WEF Standard Methods for the Exami-nation of Water and Wastewater 21st edition APHA AWWAWEF Washington DC (2005) and (2011)
[22] N J Miller and C J Miller ldquoStatistics and chemometrics foranalytical chemistry sixth editionrdquo Pearson Education Limitedpp 110ndash150 2010
[23] M E Mahmoud M M Osman O F Hafez and E Elmel-egy ldquoRemoval and preconcentration of lead (II) copper (II)chromium (III) and iron (III) from wastewaters by surfacedeveloped alumina adsorbents with immobilized 1-nitroso-2-naphtholrdquo Journal of Hazardous Materials vol 173 no 1-3 pp349ndash357 2010
[24] H I Abdel-Shafy W Hegemann and E Genschow ldquoFate ofheavy metals in the leather tanning industrial wastewater usingan anaerobic processrdquo Environmental Management and Healthvol 6 no 2 pp 28ndash33 1995
[25] H Egli et al ldquoSampling and handling of samplesrdquo IUPAC vol75 pp 1097ndash1106 2003
