Research ArticleDetermination of Spatial Chromium Contamination ofthe Environment around Industrial Zones
Dereje Homa Ermias Haile and Alemayehu P Washe
Department of Chemistry Hawassa University 05 Hawassa Ethiopia
Correspondence should be addressed to Alemayehu P Washe alemayehupyahoocom
Received 4 August 2016 Accepted 13 November 2016
Academic Editor Frantisek Foret
Copyright copy 2016 Dereje Homa et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
This studywas conducted to determine the spatial levels of chromium contamination of water agricultural soil and vegetables in theleather tanning industrial areas using spectrophotometric methods The results showed elevated accumulation of total Cr rangingfrom 1085 plusmn 0885mgL to 39696 plusmn 0326mgL 16225 plusmn 012mgKg to 1581667 plusmn 0122mgKg and 10758 plusmn 005348mgKgto 1175 plusmn 0206mgKg in water agricultural soil and vegetable samples respectively The highest levels of chromium (VI) foundfrom the speciation study were 223 plusmn 0032mgKg and 0322 plusmn 007mgL in soil and water samples respectively which decreasedwith distance from the tannery Among the vegetables the highest load of Cr(VI) was detected in onion root (0048plusmn0065mgKg)and the lowest (0004 plusmn 0007mgKg) in fruit of green pepper The detected levels of Cr in all of the suggested samples were abovethe WHO permissible limits The variations of the levels Cr(III) and Cr(VI) contamination of the environment with distance fromthe tannery were statistically significant (119901 = 005) Similarly significant difference in the levels of Cr among the tested vegetableswas recorded The levels increased with decreasing distance from the effluent channel
1 Introduction
Chromium is an environmentally important heavy metalcommonly used in various industries including tanneriestextile chromium plating steel production and refractories[1] Hazards due to chromium environmental contaminationdepend critically on its oxidation state and solubility [2 3]Chromium exhibits several oxidation states ranging from 0to +6 which dictate its chemical reactivity and thereforeits environmental and biological significanceThemost com-mon oxidation states of chromium are +3 and +6 or equiva-lently trivalent (Cr(III)) and hexavalent (Cr(VI)) chromium[4]TheCr(III) is themost stable form of the element becauseof its strong tendency to form kinetically inert hexacoordi-nate complexes with water ammonia organic acids sulfatehalides and urea [5] serves as an essential nutrient in plants[6] and exhibits a significant number of health benefitsin animals and humans [7] Cr(VI) on the other hand isacidic and is the most environmentally important state ofchromium In this form chromium is highly soluble inwater and therefore mobile whereas the reduced Cr(III)form is almost insoluble in water and thus immobile [8]
Previous researchers have demonstrated that Cr(VI) is stablein oxidizing environment with pH above 60 [9] Underconditions of pH 3 to 6 compounds of Cr(VI) tend to reduceto more thermodynamically stable Cr(OH)
3[10] All Cr(VI)
compounds are strong oxidizing agents corrosive to fleshand considered toxic and potentially carcinogenic [11] Intakeof large amounts of Cr(VI) can cause kidney and liver damageand skin contact is known to lead to skin ulcers
Of the various sources of Cr in the environment tanningindustries play amajor role One of themajor emerging prob-lems of the tanning industry is the disposal of chromium-contaminated sludge [12 13] Tannery waste contains a com-plex mixture of both organic and inorganic pollutants result-ing from such operations as cleaning fleshing splittingtanning shaving and buffing of animal residues [13 14]Chromium compounds are ubiquitous among the inorganicpollutants as a result of its use as tanning agents in the formof Cr2(SO4)3and the lack of proper wastewater treatment
strategy [15] From the total Cr used in the tanning processonly 60 to 70 is utilized and the remaining 30 to 40is released into the environment in the tannery effluent[16] This inefficient use of chromium results in wastewater
Hindawi Publishing CorporationInternational Journal of Analytical ChemistryVolume 2016 Article ID 7214932 7 pageshttpdxdoiorg10115520167214932
2 International Journal of Analytical Chemistry
containing as high as 1500ndash3000 ppm (parts per million) and500ndash1000 ppm of chromium by the conventional and thepresent day high-exhaust chrome tanning methods respec-tively [17] A wide range of physicochemical and biologicalmethods or combination of both [18] is available for theremoval of Cr from effluents but often does not completelyremove the contaminants [19] The conventional wastewatertreatment modules rely on the fact that Cr salts precipitatewith NaOH followed by the dissolution of Cr(OH)3 insulfuric acid However the quality of the recovered solution isnot always optimal due to the presence of the toxic stateof the metal lipidic substances and other impurities [20]New techniques for improving the recycling of chromiumto reduce its impacts to the environment are availablebut these technologies are limited to developed countriesdue to the high operational cost and some of them arecomplicated for management [21] Although Cr(III) is themost expected form in the tannery effluents an increase inthe hexavalent form can occur as a result of redox reactionsoccurring in the sludge for instance in water by manganeseoxides and in soils by mobile ligands such as citric aciddiethylene triamine pentaacetic acid (DTPA) and fulvicacid mediated oxidation [22] The amount of chromium atany particular time depends on the intensity of industrialprocesses proximity to the sources the amount of chromiumreleased and meteorological factors [23] Chromium fromsources releasing the element in lager particles (particlediameter varies witin 02ndash50mm) is deposited locally andcan migrate through individual particular environmentalmedia The distance covered by a deposited metal in theenvironment depends onmeteorological factors topographyand vegetation [1] Transport within the terrestrial and watersystems is greatly affected by chemical speciation chemicalforms of chromium and their affinity to chemical and pho-tochemical redox transformations precipitationdissolutionand adsorptiondesorption process for example occurringin individual compartments of the biogeochemical cycle ofchromium [4] Redox conversion of Cr(III) to Cr(VI) canincrease Cr(VI) dislocation from the soil into the watersystems [23]
In the current study the speciation ofCr in soil water andvegetable samples collected at different places in the vicinityof Ethiopia Tannery Share Company was carried out and theimplications were investigated Several analytical techniquesincluding inductively coupled plasma-mass spectrometryinductively coupled plasma-atomic emission spectrometryelectrochemical analysis spectrophotometry neutron acti-vation analysis and atomic absorption spectrophotometry(AAS) are available for the determination and speciation ofCr(III) and Cr(VI) either in off-line or on-line methods [24]In the off-line methods separation and preconcentration ofa particular chromium species are carried out using samplepretreatment technique such as color complex formation sol-uble membrane filter techniques chromatographic methodscoprecipitation ion-exchange and solvent extraction beforethe sample introduction in to the detection instrument In theon-line methods the separation system is coupled with thedetection system which is difficult to simulate at laboratoryconditions In this study off-line procedures are employed
in the spectrophotometric determination and speciationof Cr(III) and Cr(VI) Complexation of Cr(VI) with 15-diphenylcarbazide and determination of its concentrationspectrophotometrically were used as a quicker and easiermethod [25] Thus AAS was used for the determination oftotal Cr and UV-VIS for Cr(VI) Speciation was carried outbased on the difference of results from the two methods
2 Materials and Methods
21 Apparatus and Chemicals Atomic absorption spectro-photometer (Buck Scientific Model 210 VGP AAS USA)equipped with deuterium background corrector and air-acetylene flame atomizer was used for determination of totalCr in the environmental samples Spectrophotometer (modelUNICAM UV-300 England) was used for determinationof Cr(VI) All the reagents including 15-diphenylcarbazideH2O2 HNO3 Cr2(SO4)3 and K2Cr2O7 were of analyticalgrade and used as received from the supplier (Aldrich ACSReagent Germany) Serial dilutions of standard solutions forAAS analysis were prepared from standard stock solutions(Buck Scientific Calibration Standards USA) containing1000mgL of total Cr Milli-Q water was used for all solutionpreparations
22 Study Design and Description of the Study Area Theresearch was conducted at places in the vicinity of the Ethi-opia Tannery Share Company (ETSC) in Ejersa area which islocated 85 km Southeast of Addis Ababa with a grid referenceof 8∘271541015840 latitude and 39∘03894 longitudes This area ischaracterized by a semiarid climate having an altitude of1630m an average annual rainfall of 800mm and minimumand maximum temperature of 175∘C and 26∘C respectivelyThe target area selected for collection of effluent soil andvegetables samples is within three-kilometer radius of effluentdischarge site As the Koka Lake (destination of the tanneryeffluent) is 25 km far away from the outlet of tannery effluentthe effluent soil and vegetables sampling areas were selectedat the downstream section of the effluent drainage canal
23 Sample Collection Sampling sites were chosen based onproximity to expected anthropogenic emission sources Ad-ditional sites away from the potential emission sources wereselected for control samples Wastewater soil and vegetablessamples were taken at the selected sampling sites in thevicinity of the Ethiopia Tannery Share Company and 15 kmfarther for control samples The sampling took place from 5to 9 March 2016
Surfacewater sampleswere collectedwith plastic contain-ers from five representative sampling points at 200m with2 hr interval from the effluent outlet to the entry point at theLake Koka The collected effluent samples were preservedstored in icebox and transported to laboratory and stored at4∘C until further analysis
The vegetables (cabbage green pepper tomatoes andonions) samples were collected at tannery effluent irrigatedcultivation sites Two groups of vegetable samples were col-lectedThefirst group consisted of 16 samples (four samples ofeach vegetable at different sampling sites) collected at tannery
International Journal of Analytical Chemistry 3
effluent irrigated cultivation sites and the second groupconsisted of 16 samples (four samples of each vegetable atdifferent sampling sites) collected at cultivation sites that usenormal (no tannery effluent) river water at remote areas(15 km out of tannery factory) as control samples Eachsample from a sampling site was taken from 10m distanceinterval
Soil samples at the surface level (0ndash20 cm in depth) werecollected at the spot during vegetables sampling by usingwood shovels andwere brought to the laboratory in polyethy-lene plastic bags for analysis Composite soil samples werecollected from each sampling point and each sampling posi-tion had a dimension of 20 cm width by 20 cm depth Fromtwo sampling sites a total of eight soil samples (four aroundtannery and four out of tannery area as control) werecollected
24 Preparation of Samples for Analysis Digestion of wastew-ater and soil samples for total Cr determination using AASwas performed as previously described [15] The preparationof vegetable samples for AAS analysis was also performedas previously reported but with slight modifications [26]The vegetable samples were weighed to determine the freshweight and dried in an oven at 80∘C for 24 hours to determinetheir dry weight The dried samples were ground into finepowder using pestle and mortar and passed through 1mmsieve Finally 10 g of each of the vegetable samples wastransferred into an acid-washed porcelain crucible andplacedin a muffle furnace for four hours at 500∘C The crucibleswere removed from the furnace and cooled 10mL of 6MHCl was added covered and heated on a steam bath for 15minutes Another 1mL of HNO3 was added and evaporatedto dryness by continuous heating for one hour to completelydigest organic compounds Finally 5mL of 6M HCl and10mL of deionized water were added and the mixture washeated on a steam bath to complete dissolution The mixturewas cooled and filtered through a Whatman No 41 filterpaper into a 50mL volumetric flask and made up to markwith distilled water For UV-Vis analysis a 03 g sampleof ground vegetable was weighed into a glass beaker and250mL of 01M Na
2CO3was added and the mixture was
boiled on a hot plate for 15min After filtration throughWhatman No 45 filter paper the precipitates were washedseveral times with 01M Na
2CO3 The final volumes of the
sample solutions were diluted to 250mL with distilled waterprior to analysis by the 15-diphenylcarbazide method at540 nm The same procedure was also applied to 1 g of soilsamples For the determination of Cr(VI) in wastewater thewastewater samples were filtered through a Whatman No 45filter paper An aliquot of 50mL was taken from each sampleand then acidified with 5mL of 02M sulfuric acid up to amark of 50mL The samples were analyzed for chromium(VI) by the a UV-VIS spectrophotometer method using 15-diphenylcarbazide reagent (025 g 15-diphenylcarbazide in50mL of acetone) as complexing agent which reacts withCr(VI) forming a colored complex that absorbs at 540 nm
25 Statistical Analysis Statistical significance of the differ-ences in the levels of Cr detected in samples of different types
1 2 3 4 5
66
68
70
72
74
76
78
pH
Distance from effluent discharge point (times200 m)
Figure 1 pH of water samples with distance from the source (efflu-ent outlet)
(soil andwater different vegetables) or sites (with reference totannery effluent outlet point) were evaluated using one-wayANOVA at 119901 = 005 All statistical analyses were performedusing SAS Version 91
3 Results and Discussion
31 pH Characterization of Effluent Water Speciation ofCr in the environment depends inter alia on pH of thesample Therefore the pH of effluent water was measuredprior to spectrophotometric speciation of Cr Values of pHin the water samples taken from different points from thetannery outlet are presented in Figure 1 Generally the pHlevel showed a slight variation with distance from the sourcewhich gets more acidic as distance increases The increase inpH with distance might be due to exposure of the water tothe atmosphere which can lead to dissolution of SO2 in theatmosphere The pH values did not fall below 6 which meansthe dominant form of Cr in the environment should be thetrivalent form
32 Levels of Cr in Tannery Effluent The wastewater dis-charged from the Ethiopia Tannery Share Company is usedfor irrigation and fishing purposes by the rural communityliving in the vicinity of the wastewater channel downstreamTherefore it was important to determine the level of Crspecies in the tannery wastewater to comment on its suit-ability andor predict the threats from its presence Thusthe wastewater was analyzed for its total Cr concentrationand speciation was carried out using the UV-Vis methodTotal concentrations of Cr in wastewater samples takenat different distances along the wastewater channel werepresented in Figure 2 The results indicated a decrease in thetotal concentration along distance from the effluent dischargepoint with maximum of 39696 plusmn 0326mgL close to thedischarge point and minimum of 19126 plusmn 0864mgL atfarther (downstream) distance from the discharge point
4 International Journal of Analytical Chemistry
1 2 3 4 50
5
10
15
20
25
30
35
40
45
Distance from effluent discharge point (times500 m)
Tota
l Cr (
mgL
minus1)
Figure 2 Mean values and standard deviations of total Cr con-centrations recorded in wastewater samples collected at differentdistances from the tannery effluent discharge point
Moreover the decreasing concentration of both forms of Cralong the wastewater channel was recorded which indicatedthe dependence of the level of environmental contaminationon the intensity of industrial processes and proximity to thesources [4] Because as the wastewater flows farther fromthe discharge point adsorption of the metal within the wallsof the wastewater channel soil can occur Besides since theCr in the wastewater can exist either in particulate form orassociated with particulates or in solution precipitation ofthe particulates can result in a decrease in the Cr concen-tration downstream [3] The concentrations of Cr recordeddownstream (near the final discharge point 15 km fromthe tannery) were also significantly higher as compared tothe 1998 WHO standards for the limits of Cr in effluentdischarges (Geneva) which is 1mgLminus1 The high value ofCr detected in the water samples above is attributed to thefact that Cr is commonly used as tanning agent and thelow efficiency of the current wastewater treatment processemployed by the tannery The above findings indicated theunfortunate use of the tannery wastewater for irrigation aswell as fishing might lead to health problems and otherenvironmental implications in humans and animals
33 Levels of Cr in Downstream Agricultural Soil The ele-vated level of Cr detected in the wastewater that decreaseswith distance from the effluent source indicated the possibleabsorption of some forms of Cr into soils This can leadto an increase in local chromium concentration in soilsTherefore knowledge of the level of chromium in soils inthe tannery waste catchment area is important to commenton the agricultural and environmental suitability of the soilsand predict the potential hazards due to the Cr presenceThe average concentrations of total Cr in the agricultural soilsamples collected 10m away from the wastewater channeland at different distances from the tannery effluent dischargepoint were presented in Figure 3 The maximum average
10 15 20 25 30 35 40
200
400
600
800
1000
1200
1400
1600
Distance from effluent discharge point (times200 m)
Tota
l Cr (
mgmiddot
Kgminus1)
Figure 3 Mean values and standard deviations of total Cr con-centrations recorded in soil samples collected 10m away from thewastewater channel and at different distances from the tanneryeffluent discharge point
concentration was 1581667 plusmn 0122mgKg correspondingto a sample collected at closest distance (200m) to theeffluent discharge point and the lowest concentration was16225 plusmn 012mgkg which corresponded to sample at 1 kmfarther from the effluent discharge point The levels of Crrecorded in the agricultural soil samples collected up to1 km distance farther from the tannery effluent were higherthan the mean concentration of total Cr recorded in controlagricultural soil collected from remote (20 km) areas Theelevated concentration of Cr in the agricultural soil in thevicinity of tanning industry might thus be attributed to thedisposal of Cr contaminated sludge to the environment by theindustry All the recorded values were above the values givenin the National Environmental Quality Standards (NEQS) ofsoil which is 20mgkg Interestingly the levels of Cr in soilsamples are higher than that of water samples as expectedfrom the continuous accumulation of the contaminant in thesoil ANOVA also showed that mean concentrations of Crin soil and water samples were statistically significant (119901 =005) In addition the mean concentrations of soil as wellas water samples varied significantly with distances from theeffluent source In addition to this the levels of Cr in the agri-cultural soil in the vicinity of the tannery were significantlydifferent from the value recorded with control soil sampleswhich is collected from the remote areas of the tannery Thewide distribution of the contaminant along the agriculturalsoil might be partly due to the migration and partly becauseof the use of the wastewater for irrigation purpose Theabove findings point to the importance of demarcation ofagricultural areas with reference to the industrial areas toensure good practice and welfare of human beings
34 Speciation of Cr(III) and Cr(VI) in Downstream Effluentand Soil The extent of environmental impact of Cr dependsinter alia on its mobility which in turn depends on its
International Journal of Analytical Chemistry 5
Table 1 Speciation of Cr(III) and Cr(VI) in water agricultural soil and vegetables (mgsdotKgminus1)
119882119899119882 = water sample and 119899 = distance from effluent source 119878119898 119878 = soil sample and119898 = distance from the effluent source
speciation [5] The trivalent and hexavalent forms of Cr havedifferent mobility and environmental impact Thus it wasimportant to conduct speciation of the different forms ofthe element in the investigated environmental samples Theresults of speciation study were summarized in Table 1 whereit can be seen that the trivalent form is the dominant formAlthough the trivalent form is the most expected form inthe tannery effluents the incidence of the hexavalent formrecorded in water (max 0322 plusmn 007mgL and min 012 plusmn0014mgL) might be attributed to redox reactions occurringin the sludge mediated by other inorganic and organiccomponents [22] The average concentration of chromium(VI) in soil samples ranged from 223plusmn0032mgkg to 117plusmn002mgKg with the extreme values corresponding to 200mand 800m sampling sites Interestingly concentration ofCr(VI) detected in soil samples was higher than that of watersamples This indicated accumulation of Cr(VI) in the soilsamples over years of exposure to the tannery effluent Theresults also showed the fact that the extent of environmentalcontamination or impact of both forms of the elementdepends on the intensity of production and proximity to thetanning industry [4]Thus the unfortunate use of the tanneryeffluents for irrigation by the rural population living in thevicinity of the wastewater channel means their exposureto the potential hazards of the hexavalent Cr including itscorrosive effect to flesh toxicity and carcinogenicity [11]Children are more exposed to these effects as they used playwith soils andmud while guarding cattle in the contaminatedareas
35 Levels of Cr in Downstream Effluent Irrigated VegetablesThe tannery effluent irrigated cultivation of vegetables mightlead to appreciable concentration of themetal accumulated intheir tissueThis not only can have impact on the productivitybut also make the vegetables unsuitable for consumptionWhen we know that the wastewater that is used for irrigationof vegetables contains elevated concentration of Cr we shouldbe curious about its level in the plants Indeed the level ofCr that can be accumulated in plant tissues not only depends
0
2
4
6
8
10
Tannery areaControl
Green pepperCabbageTomatoOnion
Tota
l Cr (
mgmiddot
Kgminus1)
Figure 4 Mean values and standard deviations of total Cr con-centrations recorded in tannery effluent irrigated vegetable samplescultivated around (1 km radius) tannery location
on its presence in the soil but varies among plants In thecurrent study four major vegetables grown in the study areaincluding cabbage onion green pepper and tomato weretested for the level of Cr accumulated in the edible part of theplantsThe average chromium concentrations (mgkg) foundin the vegetable samples collected near the Ethiopia TanneryShare Company and control areas are presented in Figure 4The highest level of Cr was recorded in onion root (1175 plusmn0206mgKg) and the lowest level was recorded in greenpepper fruit (575 plusmn 018mgKg) The highest and the lowestlevels of Cr detected in control samples were 3341667 plusmn0075mgKg in onion root and 1075833plusmn0053482mgKg ingreen pepper fruits respectively The levels of Cr in the fourvegetables follow the increasing order green pepper fruittomato fruit cabbage and onion root Onions were found
6 International Journal of Analytical Chemistry
to contain highest load of Cr This is consistent with thefact that plants accumulate the highest level of Cr in roots[27] The highest level of Cr recorded in onion root (1175 plusmn0206mgKg) was also comparable to the previous report(11mgkg) [28] The highest level of Cr(VI) was detected inthe root of onion (0048plusmn0065mgKg) and the lowest in fruitof green pepper (0004 plusmn 0007mgKg) Other authors havereported a range of Cr load in plants irrigated with tannerywastewater [8 29] But in the context of 167mgsdotkgminus1 of Crdetected in the plants taken from a rural area exposed tocement factory emissions [29] the levels of Cr in the testedvegetable samples in the current study were not as highlycontaminated as reported before However the levels of Crdetected in all the investigated vegetable samples were stillabove the permissible limit set by WHO (1988) which is019mgsdotkgminus1
4 Conclusions
The speciation of Cr(III) and Cr(VI) was successfully carriedout in soil water and vegetables samples collected at thetanning industry area using spectrophotometric methodsThe study showed that all the investigated environmentalsamples including agricultural soil and vegetables containhigh load of Cr(III) The levels of both forms of Cr (trivalentand hexavalent) in soil and water samples were above theWHO standards and showed decreasing trend with distancefrom the tannery effluent discharge point Soil samples in thevicinity of the tanning industry contained elevated load ofCr indicating the unsuitability for agricultural purposes andpotential hazards to human beings and animals if appropriateclean up strategy is implemented All the tested vegetables(cabbage onion tomato and green pepper) contained abovepermissible levels of Cr(III) in their tissue with the highestconcentration found in the edible root parts of onion Cr(VI)is not detected in the vegetable samples probably due tolack of absorption ANOVA showed that variations of thelevel of Cr among the tested vegetables were statisticallysignificant This confirmed that the chromium absorptionfrom the soil by vegetables depends on the plant specieswith highest accumulation in roots In the agricultural soilin the vicinity of the tannery the levels of Cr(III) andCr(VI) were much greater compared to control soil samplescollected at remote areas In conclusion the discharge of Crrich sludge to the environment and the unfortunate use foragricultural purposes by the community living in the vicinityof the effluent channel can lead to potential hazards of Crparticularly the hexavalent form on humans and affect thequality of the natural resources around the tanning industryTherefore appropriate reclamation methods are crucial toreducing Cr contamination
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors are very grateful to Hawassa University (HU)for providing laboratory facility for the conduct of the
experiments Dereje Homa is also grateful to the Office ofResearch and Technology Transfer of HU for partial financialsupport during the study
References
[1] J O Nriagu ldquoProduction and uses of chromiumrdquo in Chromiumin Natural and Human Environments J O Nriagu and ENieboer Eds pp 81ndash104 Wiley Interscience New York NYUSA 1988
[2] S Mishra V Singh S Srivastava et al ldquoStudies on uptake oftrivalent and hexavalent chromium by maize (Zea mays)rdquo Foodand Chemical Toxicology vol 33 no 5 pp 393ndash397 1995
[3] R Shrivastava R K Upreti P K Seth and U C ChaturvedildquoEffects of chromium on the immune systemrdquo FEMS Immunol-ogy and Medical Microbiology vol 34 no 1 pp 1ndash7 2002
[4] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[5] A D Apte S Verma V Tare and P Bose ldquoOxidation of Cr(III)in tannery sludge to Cr(VI) field observations and theoreticalassessmentrdquo Journal of HazardousMaterials vol 121 no 1ndash3 pp215ndash222 2005
[6] Z Stępniewska and A Wolinska ldquoSoil dehydrogenase activityin the presence of chromium (III) and (VI)rdquo InternationalAgrophysics vol 19 no 1 pp 79ndash83 2005
[7] R A Anderson ldquoChromium in the prevention and control ofdiabetesrdquoDiabetes ampMetabolism vol 26 no 1 pp 22ndash27 2000
[8] C Bini L Maleci and A Romanin ldquoThe chromium issue insoils of the leather tannery district in Italyrdquo Journal of Geochem-ical Exploration vol 96 no 2-3 pp 194ndash202 2008
[9] B R James J C Petura R J Vitale and G R MussolineldquoOxidation-reduction chemistry of chromium relevance to theregulation and remediation of chromate-contaminated soilsrdquoJournal of Soil Contamination vol 6 no 6 pp 569ndash580 1997
[10] P H Masscheleyn J H Pardue R D DeLaune and W HPatrick Jr ldquoChromium redox chemistry in a Lower MississippiValley bottomland hardwood wetlandrdquo Environmental Scienceand Technology vol 26 no 6 pp 1217ndash1226 1992
[11] A P Das and S Mishra ldquoHexavalent chromium (VI) environ-ment pollutant and health hazardrdquo Journal of EnvironmentalResearch and Development vol 2 no 3 pp 386ndash392 2008
[12] MMwinyihija Ecotoxicological Diagnosis in the Tanning Indus-try Springer Berlin Germany 2010
[13] M Mwinyihija A Meharg J Dawson N J C Strachan andK Killham ldquoAn ecotoxicological approach to assessing theimpact of tanning industry effluent on river healthrdquo Archives ofEnvironmental Contamination and Toxicology vol 50 no 3 pp316ndash324 2006
[14] M Mwinyihija N J C Strachan A Meharg and K KillhamldquoBiosensor based toxicity dissection of tannery and associ-ated environmental samplesrdquo Journal of the American LeatherChemists Association vol 100 no 12 pp 481ndash490 2005
[15] A H Reda ldquoStudy on the pollution levels of trace metals frommodjo tannery effluent in the surrounding river water and soilrdquoScience Journal of Analytical Chemistry vol 3 no 5 pp 56ndash602015
[16] A Cassano L Della Pietra and E Drioli ldquoIntegrated mem-brane process for the recovery of chromium salts from tanneryeffluentsrdquo Industrial amp Engineering Chemistry Research vol 46no 21 pp 6825ndash6830 2007
International Journal of Analytical Chemistry 7
[17] R Aravindhan B Madhan J R Rao B U Nair and T Ramas-ami ldquoBioaccumulation of chromium from tannery wastewateran approach for chrome recovery and reuserdquo EnvironmentalScience and Technology vol 38 no 1 pp 300ndash306 2004
[18] T Reemtsma and M Jekel ldquoDissolved organics in tannerywastewaters and their alteration by a combined anaerobic andaerobic treatmentrdquoWater Research vol 31 no 5 pp 1035ndash10461997
[19] E Bouwer N Durant L Wilson W Zhang and A Cunning-ham ldquoDegradation of xenobiotic compounds in situ capabili-ties and limitsrdquo FEMSMicrobiology Reviews vol 15 no 2-3 pp307ndash317 1994
[20] A Cassano R Molinari M Romano and E Drioli ldquoTreatmentof aqueous effluents of the leather industry by membraneprocesses a reviewrdquo Journal of Membrane Science vol 181 no 1pp 111ndash126 2001
[21] V J Sundar J R Rao and C Muralidharan ldquoCleaner chrometanningmdashemerging optionsrdquo Journal of Cleaner Production vol10 no 1 pp 69ndash74 2002
[22] Z Stepniewska K Bucior and R P Bennicelli ldquoThe effects ofMnO
2on sorption and oxidation of Cr(III) by soilsrdquoGeoderma
vol 122 no 2ndash4 pp 291ndash296 2004[23] R J Bartlett and J M Kimble ldquoBehavior of chromium in soils
oxidationrdquo Journal of Environmental Quality vol 8 pp 31ndash351976
[24] N R Jyothi NAM FarookMCho and J Shim ldquoAnalysis andspeciation of chromium in environmental matrices by variousanalytical techniquesrdquoAsian Journal of Chemistry vol 25 no 8pp 4125ndash4136 2013
[25] M Noroozifar and M Khorasani-Motlagh ldquoSpecific extractionof chromium as tetrabutylammonium-chromate and spec-trophotometric determination by diphenylcarbazide specia-tion of chromium in effluent streamsrdquo Analytical Sciences vol19 no 5 pp 705ndash708 2003
[26] J C Akan B G Kolo B S Yikala andV O Ogugbuaja ldquoDeter-minations of some heavy metals in vegetable samples from BiuLocal Government Area Borno State North Eastern NigeriardquoInternational Journal of EnvironmentalMonitoring andAnalysisvol 1 no 2 pp 40ndash46 2013
[27] R S Bai and T E Abraham ldquoBiosorption of Cr (VI) from aque-ous solution byRhizopus nigricansrdquo Bioresource Technology vol79 no 1 pp 73ndash81 2001
[28] A Wolinska Z Stępniewska and R Włosek ldquoThe influenceof old leather tannery district on chromium contamination ofsoils water and plantsrdquoNatural Science vol 05 no 02 pp 253ndash258 2013
[29] B Isikli T A Demir SM Urer A Berber T Akar andC Kaly-oncu ldquoEffects of chromium exposure from a cement factoryrdquoEnvironmental Research vol 91 no 2 pp 113ndash118 2003
containing as high as 1500ndash3000 ppm (parts per million) and500ndash1000 ppm of chromium by the conventional and thepresent day high-exhaust chrome tanning methods respec-tively [17] A wide range of physicochemical and biologicalmethods or combination of both [18] is available for theremoval of Cr from effluents but often does not completelyremove the contaminants [19] The conventional wastewatertreatment modules rely on the fact that Cr salts precipitatewith NaOH followed by the dissolution of Cr(OH)3 insulfuric acid However the quality of the recovered solution isnot always optimal due to the presence of the toxic stateof the metal lipidic substances and other impurities [20]New techniques for improving the recycling of chromiumto reduce its impacts to the environment are availablebut these technologies are limited to developed countriesdue to the high operational cost and some of them arecomplicated for management [21] Although Cr(III) is themost expected form in the tannery effluents an increase inthe hexavalent form can occur as a result of redox reactionsoccurring in the sludge for instance in water by manganeseoxides and in soils by mobile ligands such as citric aciddiethylene triamine pentaacetic acid (DTPA) and fulvicacid mediated oxidation [22] The amount of chromium atany particular time depends on the intensity of industrialprocesses proximity to the sources the amount of chromiumreleased and meteorological factors [23] Chromium fromsources releasing the element in lager particles (particlediameter varies witin 02ndash50mm) is deposited locally andcan migrate through individual particular environmentalmedia The distance covered by a deposited metal in theenvironment depends onmeteorological factors topographyand vegetation [1] Transport within the terrestrial and watersystems is greatly affected by chemical speciation chemicalforms of chromium and their affinity to chemical and pho-tochemical redox transformations precipitationdissolutionand adsorptiondesorption process for example occurringin individual compartments of the biogeochemical cycle ofchromium [4] Redox conversion of Cr(III) to Cr(VI) canincrease Cr(VI) dislocation from the soil into the watersystems [23]
In the current study the speciation ofCr in soil water andvegetable samples collected at different places in the vicinityof Ethiopia Tannery Share Company was carried out and theimplications were investigated Several analytical techniquesincluding inductively coupled plasma-mass spectrometryinductively coupled plasma-atomic emission spectrometryelectrochemical analysis spectrophotometry neutron acti-vation analysis and atomic absorption spectrophotometry(AAS) are available for the determination and speciation ofCr(III) and Cr(VI) either in off-line or on-line methods [24]In the off-line methods separation and preconcentration ofa particular chromium species are carried out using samplepretreatment technique such as color complex formation sol-uble membrane filter techniques chromatographic methodscoprecipitation ion-exchange and solvent extraction beforethe sample introduction in to the detection instrument In theon-line methods the separation system is coupled with thedetection system which is difficult to simulate at laboratoryconditions In this study off-line procedures are employed
in the spectrophotometric determination and speciationof Cr(III) and Cr(VI) Complexation of Cr(VI) with 15-diphenylcarbazide and determination of its concentrationspectrophotometrically were used as a quicker and easiermethod [25] Thus AAS was used for the determination oftotal Cr and UV-VIS for Cr(VI) Speciation was carried outbased on the difference of results from the two methods
2 Materials and Methods
21 Apparatus and Chemicals Atomic absorption spectro-photometer (Buck Scientific Model 210 VGP AAS USA)equipped with deuterium background corrector and air-acetylene flame atomizer was used for determination of totalCr in the environmental samples Spectrophotometer (modelUNICAM UV-300 England) was used for determinationof Cr(VI) All the reagents including 15-diphenylcarbazideH2O2 HNO3 Cr2(SO4)3 and K2Cr2O7 were of analyticalgrade and used as received from the supplier (Aldrich ACSReagent Germany) Serial dilutions of standard solutions forAAS analysis were prepared from standard stock solutions(Buck Scientific Calibration Standards USA) containing1000mgL of total Cr Milli-Q water was used for all solutionpreparations
22 Study Design and Description of the Study Area Theresearch was conducted at places in the vicinity of the Ethi-opia Tannery Share Company (ETSC) in Ejersa area which islocated 85 km Southeast of Addis Ababa with a grid referenceof 8∘271541015840 latitude and 39∘03894 longitudes This area ischaracterized by a semiarid climate having an altitude of1630m an average annual rainfall of 800mm and minimumand maximum temperature of 175∘C and 26∘C respectivelyThe target area selected for collection of effluent soil andvegetables samples is within three-kilometer radius of effluentdischarge site As the Koka Lake (destination of the tanneryeffluent) is 25 km far away from the outlet of tannery effluentthe effluent soil and vegetables sampling areas were selectedat the downstream section of the effluent drainage canal
23 Sample Collection Sampling sites were chosen based onproximity to expected anthropogenic emission sources Ad-ditional sites away from the potential emission sources wereselected for control samples Wastewater soil and vegetablessamples were taken at the selected sampling sites in thevicinity of the Ethiopia Tannery Share Company and 15 kmfarther for control samples The sampling took place from 5to 9 March 2016
Surfacewater sampleswere collectedwith plastic contain-ers from five representative sampling points at 200m with2 hr interval from the effluent outlet to the entry point at theLake Koka The collected effluent samples were preservedstored in icebox and transported to laboratory and stored at4∘C until further analysis
The vegetables (cabbage green pepper tomatoes andonions) samples were collected at tannery effluent irrigatedcultivation sites Two groups of vegetable samples were col-lectedThefirst group consisted of 16 samples (four samples ofeach vegetable at different sampling sites) collected at tannery
International Journal of Analytical Chemistry 3
effluent irrigated cultivation sites and the second groupconsisted of 16 samples (four samples of each vegetable atdifferent sampling sites) collected at cultivation sites that usenormal (no tannery effluent) river water at remote areas(15 km out of tannery factory) as control samples Eachsample from a sampling site was taken from 10m distanceinterval
Soil samples at the surface level (0ndash20 cm in depth) werecollected at the spot during vegetables sampling by usingwood shovels andwere brought to the laboratory in polyethy-lene plastic bags for analysis Composite soil samples werecollected from each sampling point and each sampling posi-tion had a dimension of 20 cm width by 20 cm depth Fromtwo sampling sites a total of eight soil samples (four aroundtannery and four out of tannery area as control) werecollected
24 Preparation of Samples for Analysis Digestion of wastew-ater and soil samples for total Cr determination using AASwas performed as previously described [15] The preparationof vegetable samples for AAS analysis was also performedas previously reported but with slight modifications [26]The vegetable samples were weighed to determine the freshweight and dried in an oven at 80∘C for 24 hours to determinetheir dry weight The dried samples were ground into finepowder using pestle and mortar and passed through 1mmsieve Finally 10 g of each of the vegetable samples wastransferred into an acid-washed porcelain crucible andplacedin a muffle furnace for four hours at 500∘C The crucibleswere removed from the furnace and cooled 10mL of 6MHCl was added covered and heated on a steam bath for 15minutes Another 1mL of HNO3 was added and evaporatedto dryness by continuous heating for one hour to completelydigest organic compounds Finally 5mL of 6M HCl and10mL of deionized water were added and the mixture washeated on a steam bath to complete dissolution The mixturewas cooled and filtered through a Whatman No 41 filterpaper into a 50mL volumetric flask and made up to markwith distilled water For UV-Vis analysis a 03 g sampleof ground vegetable was weighed into a glass beaker and250mL of 01M Na
2CO3was added and the mixture was
boiled on a hot plate for 15min After filtration throughWhatman No 45 filter paper the precipitates were washedseveral times with 01M Na
2CO3 The final volumes of the
sample solutions were diluted to 250mL with distilled waterprior to analysis by the 15-diphenylcarbazide method at540 nm The same procedure was also applied to 1 g of soilsamples For the determination of Cr(VI) in wastewater thewastewater samples were filtered through a Whatman No 45filter paper An aliquot of 50mL was taken from each sampleand then acidified with 5mL of 02M sulfuric acid up to amark of 50mL The samples were analyzed for chromium(VI) by the a UV-VIS spectrophotometer method using 15-diphenylcarbazide reagent (025 g 15-diphenylcarbazide in50mL of acetone) as complexing agent which reacts withCr(VI) forming a colored complex that absorbs at 540 nm
25 Statistical Analysis Statistical significance of the differ-ences in the levels of Cr detected in samples of different types
1 2 3 4 5
66
68
70
72
74
76
78
pH
Distance from effluent discharge point (times200 m)
Figure 1 pH of water samples with distance from the source (efflu-ent outlet)
(soil andwater different vegetables) or sites (with reference totannery effluent outlet point) were evaluated using one-wayANOVA at 119901 = 005 All statistical analyses were performedusing SAS Version 91
3 Results and Discussion
31 pH Characterization of Effluent Water Speciation ofCr in the environment depends inter alia on pH of thesample Therefore the pH of effluent water was measuredprior to spectrophotometric speciation of Cr Values of pHin the water samples taken from different points from thetannery outlet are presented in Figure 1 Generally the pHlevel showed a slight variation with distance from the sourcewhich gets more acidic as distance increases The increase inpH with distance might be due to exposure of the water tothe atmosphere which can lead to dissolution of SO2 in theatmosphere The pH values did not fall below 6 which meansthe dominant form of Cr in the environment should be thetrivalent form
32 Levels of Cr in Tannery Effluent The wastewater dis-charged from the Ethiopia Tannery Share Company is usedfor irrigation and fishing purposes by the rural communityliving in the vicinity of the wastewater channel downstreamTherefore it was important to determine the level of Crspecies in the tannery wastewater to comment on its suit-ability andor predict the threats from its presence Thusthe wastewater was analyzed for its total Cr concentrationand speciation was carried out using the UV-Vis methodTotal concentrations of Cr in wastewater samples takenat different distances along the wastewater channel werepresented in Figure 2 The results indicated a decrease in thetotal concentration along distance from the effluent dischargepoint with maximum of 39696 plusmn 0326mgL close to thedischarge point and minimum of 19126 plusmn 0864mgL atfarther (downstream) distance from the discharge point
4 International Journal of Analytical Chemistry
1 2 3 4 50
5
10
15
20
25
30
35
40
45
Distance from effluent discharge point (times500 m)
Tota
l Cr (
mgL
minus1)
Figure 2 Mean values and standard deviations of total Cr con-centrations recorded in wastewater samples collected at differentdistances from the tannery effluent discharge point
Moreover the decreasing concentration of both forms of Cralong the wastewater channel was recorded which indicatedthe dependence of the level of environmental contaminationon the intensity of industrial processes and proximity to thesources [4] Because as the wastewater flows farther fromthe discharge point adsorption of the metal within the wallsof the wastewater channel soil can occur Besides since theCr in the wastewater can exist either in particulate form orassociated with particulates or in solution precipitation ofthe particulates can result in a decrease in the Cr concen-tration downstream [3] The concentrations of Cr recordeddownstream (near the final discharge point 15 km fromthe tannery) were also significantly higher as compared tothe 1998 WHO standards for the limits of Cr in effluentdischarges (Geneva) which is 1mgLminus1 The high value ofCr detected in the water samples above is attributed to thefact that Cr is commonly used as tanning agent and thelow efficiency of the current wastewater treatment processemployed by the tannery The above findings indicated theunfortunate use of the tannery wastewater for irrigation aswell as fishing might lead to health problems and otherenvironmental implications in humans and animals
33 Levels of Cr in Downstream Agricultural Soil The ele-vated level of Cr detected in the wastewater that decreaseswith distance from the effluent source indicated the possibleabsorption of some forms of Cr into soils This can leadto an increase in local chromium concentration in soilsTherefore knowledge of the level of chromium in soils inthe tannery waste catchment area is important to commenton the agricultural and environmental suitability of the soilsand predict the potential hazards due to the Cr presenceThe average concentrations of total Cr in the agricultural soilsamples collected 10m away from the wastewater channeland at different distances from the tannery effluent dischargepoint were presented in Figure 3 The maximum average
10 15 20 25 30 35 40
200
400
600
800
1000
1200
1400
1600
Distance from effluent discharge point (times200 m)
Tota
l Cr (
mgmiddot
Kgminus1)
Figure 3 Mean values and standard deviations of total Cr con-centrations recorded in soil samples collected 10m away from thewastewater channel and at different distances from the tanneryeffluent discharge point
concentration was 1581667 plusmn 0122mgKg correspondingto a sample collected at closest distance (200m) to theeffluent discharge point and the lowest concentration was16225 plusmn 012mgkg which corresponded to sample at 1 kmfarther from the effluent discharge point The levels of Crrecorded in the agricultural soil samples collected up to1 km distance farther from the tannery effluent were higherthan the mean concentration of total Cr recorded in controlagricultural soil collected from remote (20 km) areas Theelevated concentration of Cr in the agricultural soil in thevicinity of tanning industry might thus be attributed to thedisposal of Cr contaminated sludge to the environment by theindustry All the recorded values were above the values givenin the National Environmental Quality Standards (NEQS) ofsoil which is 20mgkg Interestingly the levels of Cr in soilsamples are higher than that of water samples as expectedfrom the continuous accumulation of the contaminant in thesoil ANOVA also showed that mean concentrations of Crin soil and water samples were statistically significant (119901 =005) In addition the mean concentrations of soil as wellas water samples varied significantly with distances from theeffluent source In addition to this the levels of Cr in the agri-cultural soil in the vicinity of the tannery were significantlydifferent from the value recorded with control soil sampleswhich is collected from the remote areas of the tannery Thewide distribution of the contaminant along the agriculturalsoil might be partly due to the migration and partly becauseof the use of the wastewater for irrigation purpose Theabove findings point to the importance of demarcation ofagricultural areas with reference to the industrial areas toensure good practice and welfare of human beings
34 Speciation of Cr(III) and Cr(VI) in Downstream Effluentand Soil The extent of environmental impact of Cr dependsinter alia on its mobility which in turn depends on its
International Journal of Analytical Chemistry 5
Table 1 Speciation of Cr(III) and Cr(VI) in water agricultural soil and vegetables (mgsdotKgminus1)
119882119899119882 = water sample and 119899 = distance from effluent source 119878119898 119878 = soil sample and119898 = distance from the effluent source
speciation [5] The trivalent and hexavalent forms of Cr havedifferent mobility and environmental impact Thus it wasimportant to conduct speciation of the different forms ofthe element in the investigated environmental samples Theresults of speciation study were summarized in Table 1 whereit can be seen that the trivalent form is the dominant formAlthough the trivalent form is the most expected form inthe tannery effluents the incidence of the hexavalent formrecorded in water (max 0322 plusmn 007mgL and min 012 plusmn0014mgL) might be attributed to redox reactions occurringin the sludge mediated by other inorganic and organiccomponents [22] The average concentration of chromium(VI) in soil samples ranged from 223plusmn0032mgkg to 117plusmn002mgKg with the extreme values corresponding to 200mand 800m sampling sites Interestingly concentration ofCr(VI) detected in soil samples was higher than that of watersamples This indicated accumulation of Cr(VI) in the soilsamples over years of exposure to the tannery effluent Theresults also showed the fact that the extent of environmentalcontamination or impact of both forms of the elementdepends on the intensity of production and proximity to thetanning industry [4]Thus the unfortunate use of the tanneryeffluents for irrigation by the rural population living in thevicinity of the wastewater channel means their exposureto the potential hazards of the hexavalent Cr including itscorrosive effect to flesh toxicity and carcinogenicity [11]Children are more exposed to these effects as they used playwith soils andmud while guarding cattle in the contaminatedareas
35 Levels of Cr in Downstream Effluent Irrigated VegetablesThe tannery effluent irrigated cultivation of vegetables mightlead to appreciable concentration of themetal accumulated intheir tissueThis not only can have impact on the productivitybut also make the vegetables unsuitable for consumptionWhen we know that the wastewater that is used for irrigationof vegetables contains elevated concentration of Cr we shouldbe curious about its level in the plants Indeed the level ofCr that can be accumulated in plant tissues not only depends
0
2
4
6
8
10
Tannery areaControl
Green pepperCabbageTomatoOnion
Tota
l Cr (
mgmiddot
Kgminus1)
Figure 4 Mean values and standard deviations of total Cr con-centrations recorded in tannery effluent irrigated vegetable samplescultivated around (1 km radius) tannery location
on its presence in the soil but varies among plants In thecurrent study four major vegetables grown in the study areaincluding cabbage onion green pepper and tomato weretested for the level of Cr accumulated in the edible part of theplantsThe average chromium concentrations (mgkg) foundin the vegetable samples collected near the Ethiopia TanneryShare Company and control areas are presented in Figure 4The highest level of Cr was recorded in onion root (1175 plusmn0206mgKg) and the lowest level was recorded in greenpepper fruit (575 plusmn 018mgKg) The highest and the lowestlevels of Cr detected in control samples were 3341667 plusmn0075mgKg in onion root and 1075833plusmn0053482mgKg ingreen pepper fruits respectively The levels of Cr in the fourvegetables follow the increasing order green pepper fruittomato fruit cabbage and onion root Onions were found
6 International Journal of Analytical Chemistry
to contain highest load of Cr This is consistent with thefact that plants accumulate the highest level of Cr in roots[27] The highest level of Cr recorded in onion root (1175 plusmn0206mgKg) was also comparable to the previous report(11mgkg) [28] The highest level of Cr(VI) was detected inthe root of onion (0048plusmn0065mgKg) and the lowest in fruitof green pepper (0004 plusmn 0007mgKg) Other authors havereported a range of Cr load in plants irrigated with tannerywastewater [8 29] But in the context of 167mgsdotkgminus1 of Crdetected in the plants taken from a rural area exposed tocement factory emissions [29] the levels of Cr in the testedvegetable samples in the current study were not as highlycontaminated as reported before However the levels of Crdetected in all the investigated vegetable samples were stillabove the permissible limit set by WHO (1988) which is019mgsdotkgminus1
4 Conclusions
The speciation of Cr(III) and Cr(VI) was successfully carriedout in soil water and vegetables samples collected at thetanning industry area using spectrophotometric methodsThe study showed that all the investigated environmentalsamples including agricultural soil and vegetables containhigh load of Cr(III) The levels of both forms of Cr (trivalentand hexavalent) in soil and water samples were above theWHO standards and showed decreasing trend with distancefrom the tannery effluent discharge point Soil samples in thevicinity of the tanning industry contained elevated load ofCr indicating the unsuitability for agricultural purposes andpotential hazards to human beings and animals if appropriateclean up strategy is implemented All the tested vegetables(cabbage onion tomato and green pepper) contained abovepermissible levels of Cr(III) in their tissue with the highestconcentration found in the edible root parts of onion Cr(VI)is not detected in the vegetable samples probably due tolack of absorption ANOVA showed that variations of thelevel of Cr among the tested vegetables were statisticallysignificant This confirmed that the chromium absorptionfrom the soil by vegetables depends on the plant specieswith highest accumulation in roots In the agricultural soilin the vicinity of the tannery the levels of Cr(III) andCr(VI) were much greater compared to control soil samplescollected at remote areas In conclusion the discharge of Crrich sludge to the environment and the unfortunate use foragricultural purposes by the community living in the vicinityof the effluent channel can lead to potential hazards of Crparticularly the hexavalent form on humans and affect thequality of the natural resources around the tanning industryTherefore appropriate reclamation methods are crucial toreducing Cr contamination
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors are very grateful to Hawassa University (HU)for providing laboratory facility for the conduct of the
experiments Dereje Homa is also grateful to the Office ofResearch and Technology Transfer of HU for partial financialsupport during the study
References
[1] J O Nriagu ldquoProduction and uses of chromiumrdquo in Chromiumin Natural and Human Environments J O Nriagu and ENieboer Eds pp 81ndash104 Wiley Interscience New York NYUSA 1988
[2] S Mishra V Singh S Srivastava et al ldquoStudies on uptake oftrivalent and hexavalent chromium by maize (Zea mays)rdquo Foodand Chemical Toxicology vol 33 no 5 pp 393ndash397 1995
[3] R Shrivastava R K Upreti P K Seth and U C ChaturvedildquoEffects of chromium on the immune systemrdquo FEMS Immunol-ogy and Medical Microbiology vol 34 no 1 pp 1ndash7 2002
[4] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[5] A D Apte S Verma V Tare and P Bose ldquoOxidation of Cr(III)in tannery sludge to Cr(VI) field observations and theoreticalassessmentrdquo Journal of HazardousMaterials vol 121 no 1ndash3 pp215ndash222 2005
[6] Z Stępniewska and A Wolinska ldquoSoil dehydrogenase activityin the presence of chromium (III) and (VI)rdquo InternationalAgrophysics vol 19 no 1 pp 79ndash83 2005
[7] R A Anderson ldquoChromium in the prevention and control ofdiabetesrdquoDiabetes ampMetabolism vol 26 no 1 pp 22ndash27 2000
[8] C Bini L Maleci and A Romanin ldquoThe chromium issue insoils of the leather tannery district in Italyrdquo Journal of Geochem-ical Exploration vol 96 no 2-3 pp 194ndash202 2008
[9] B R James J C Petura R J Vitale and G R MussolineldquoOxidation-reduction chemistry of chromium relevance to theregulation and remediation of chromate-contaminated soilsrdquoJournal of Soil Contamination vol 6 no 6 pp 569ndash580 1997
[10] P H Masscheleyn J H Pardue R D DeLaune and W HPatrick Jr ldquoChromium redox chemistry in a Lower MississippiValley bottomland hardwood wetlandrdquo Environmental Scienceand Technology vol 26 no 6 pp 1217ndash1226 1992
[11] A P Das and S Mishra ldquoHexavalent chromium (VI) environ-ment pollutant and health hazardrdquo Journal of EnvironmentalResearch and Development vol 2 no 3 pp 386ndash392 2008
[12] MMwinyihija Ecotoxicological Diagnosis in the Tanning Indus-try Springer Berlin Germany 2010
[13] M Mwinyihija A Meharg J Dawson N J C Strachan andK Killham ldquoAn ecotoxicological approach to assessing theimpact of tanning industry effluent on river healthrdquo Archives ofEnvironmental Contamination and Toxicology vol 50 no 3 pp316ndash324 2006
[14] M Mwinyihija N J C Strachan A Meharg and K KillhamldquoBiosensor based toxicity dissection of tannery and associ-ated environmental samplesrdquo Journal of the American LeatherChemists Association vol 100 no 12 pp 481ndash490 2005
[15] A H Reda ldquoStudy on the pollution levels of trace metals frommodjo tannery effluent in the surrounding river water and soilrdquoScience Journal of Analytical Chemistry vol 3 no 5 pp 56ndash602015
[16] A Cassano L Della Pietra and E Drioli ldquoIntegrated mem-brane process for the recovery of chromium salts from tanneryeffluentsrdquo Industrial amp Engineering Chemistry Research vol 46no 21 pp 6825ndash6830 2007
International Journal of Analytical Chemistry 7
[17] R Aravindhan B Madhan J R Rao B U Nair and T Ramas-ami ldquoBioaccumulation of chromium from tannery wastewateran approach for chrome recovery and reuserdquo EnvironmentalScience and Technology vol 38 no 1 pp 300ndash306 2004
[18] T Reemtsma and M Jekel ldquoDissolved organics in tannerywastewaters and their alteration by a combined anaerobic andaerobic treatmentrdquoWater Research vol 31 no 5 pp 1035ndash10461997
[19] E Bouwer N Durant L Wilson W Zhang and A Cunning-ham ldquoDegradation of xenobiotic compounds in situ capabili-ties and limitsrdquo FEMSMicrobiology Reviews vol 15 no 2-3 pp307ndash317 1994
[20] A Cassano R Molinari M Romano and E Drioli ldquoTreatmentof aqueous effluents of the leather industry by membraneprocesses a reviewrdquo Journal of Membrane Science vol 181 no 1pp 111ndash126 2001
[21] V J Sundar J R Rao and C Muralidharan ldquoCleaner chrometanningmdashemerging optionsrdquo Journal of Cleaner Production vol10 no 1 pp 69ndash74 2002
[22] Z Stepniewska K Bucior and R P Bennicelli ldquoThe effects ofMnO
2on sorption and oxidation of Cr(III) by soilsrdquoGeoderma
vol 122 no 2ndash4 pp 291ndash296 2004[23] R J Bartlett and J M Kimble ldquoBehavior of chromium in soils
oxidationrdquo Journal of Environmental Quality vol 8 pp 31ndash351976
[24] N R Jyothi NAM FarookMCho and J Shim ldquoAnalysis andspeciation of chromium in environmental matrices by variousanalytical techniquesrdquoAsian Journal of Chemistry vol 25 no 8pp 4125ndash4136 2013
[25] M Noroozifar and M Khorasani-Motlagh ldquoSpecific extractionof chromium as tetrabutylammonium-chromate and spec-trophotometric determination by diphenylcarbazide specia-tion of chromium in effluent streamsrdquo Analytical Sciences vol19 no 5 pp 705ndash708 2003
[26] J C Akan B G Kolo B S Yikala andV O Ogugbuaja ldquoDeter-minations of some heavy metals in vegetable samples from BiuLocal Government Area Borno State North Eastern NigeriardquoInternational Journal of EnvironmentalMonitoring andAnalysisvol 1 no 2 pp 40ndash46 2013
[27] R S Bai and T E Abraham ldquoBiosorption of Cr (VI) from aque-ous solution byRhizopus nigricansrdquo Bioresource Technology vol79 no 1 pp 73ndash81 2001
[28] A Wolinska Z Stępniewska and R Włosek ldquoThe influenceof old leather tannery district on chromium contamination ofsoils water and plantsrdquoNatural Science vol 05 no 02 pp 253ndash258 2013
[29] B Isikli T A Demir SM Urer A Berber T Akar andC Kaly-oncu ldquoEffects of chromium exposure from a cement factoryrdquoEnvironmental Research vol 91 no 2 pp 113ndash118 2003
effluent irrigated cultivation sites and the second groupconsisted of 16 samples (four samples of each vegetable atdifferent sampling sites) collected at cultivation sites that usenormal (no tannery effluent) river water at remote areas(15 km out of tannery factory) as control samples Eachsample from a sampling site was taken from 10m distanceinterval
Soil samples at the surface level (0ndash20 cm in depth) werecollected at the spot during vegetables sampling by usingwood shovels andwere brought to the laboratory in polyethy-lene plastic bags for analysis Composite soil samples werecollected from each sampling point and each sampling posi-tion had a dimension of 20 cm width by 20 cm depth Fromtwo sampling sites a total of eight soil samples (four aroundtannery and four out of tannery area as control) werecollected
24 Preparation of Samples for Analysis Digestion of wastew-ater and soil samples for total Cr determination using AASwas performed as previously described [15] The preparationof vegetable samples for AAS analysis was also performedas previously reported but with slight modifications [26]The vegetable samples were weighed to determine the freshweight and dried in an oven at 80∘C for 24 hours to determinetheir dry weight The dried samples were ground into finepowder using pestle and mortar and passed through 1mmsieve Finally 10 g of each of the vegetable samples wastransferred into an acid-washed porcelain crucible andplacedin a muffle furnace for four hours at 500∘C The crucibleswere removed from the furnace and cooled 10mL of 6MHCl was added covered and heated on a steam bath for 15minutes Another 1mL of HNO3 was added and evaporatedto dryness by continuous heating for one hour to completelydigest organic compounds Finally 5mL of 6M HCl and10mL of deionized water were added and the mixture washeated on a steam bath to complete dissolution The mixturewas cooled and filtered through a Whatman No 41 filterpaper into a 50mL volumetric flask and made up to markwith distilled water For UV-Vis analysis a 03 g sampleof ground vegetable was weighed into a glass beaker and250mL of 01M Na
2CO3was added and the mixture was
boiled on a hot plate for 15min After filtration throughWhatman No 45 filter paper the precipitates were washedseveral times with 01M Na
2CO3 The final volumes of the
sample solutions were diluted to 250mL with distilled waterprior to analysis by the 15-diphenylcarbazide method at540 nm The same procedure was also applied to 1 g of soilsamples For the determination of Cr(VI) in wastewater thewastewater samples were filtered through a Whatman No 45filter paper An aliquot of 50mL was taken from each sampleand then acidified with 5mL of 02M sulfuric acid up to amark of 50mL The samples were analyzed for chromium(VI) by the a UV-VIS spectrophotometer method using 15-diphenylcarbazide reagent (025 g 15-diphenylcarbazide in50mL of acetone) as complexing agent which reacts withCr(VI) forming a colored complex that absorbs at 540 nm
25 Statistical Analysis Statistical significance of the differ-ences in the levels of Cr detected in samples of different types
1 2 3 4 5
66
68
70
72
74
76
78
pH
Distance from effluent discharge point (times200 m)
Figure 1 pH of water samples with distance from the source (efflu-ent outlet)
(soil andwater different vegetables) or sites (with reference totannery effluent outlet point) were evaluated using one-wayANOVA at 119901 = 005 All statistical analyses were performedusing SAS Version 91
3 Results and Discussion
31 pH Characterization of Effluent Water Speciation ofCr in the environment depends inter alia on pH of thesample Therefore the pH of effluent water was measuredprior to spectrophotometric speciation of Cr Values of pHin the water samples taken from different points from thetannery outlet are presented in Figure 1 Generally the pHlevel showed a slight variation with distance from the sourcewhich gets more acidic as distance increases The increase inpH with distance might be due to exposure of the water tothe atmosphere which can lead to dissolution of SO2 in theatmosphere The pH values did not fall below 6 which meansthe dominant form of Cr in the environment should be thetrivalent form
32 Levels of Cr in Tannery Effluent The wastewater dis-charged from the Ethiopia Tannery Share Company is usedfor irrigation and fishing purposes by the rural communityliving in the vicinity of the wastewater channel downstreamTherefore it was important to determine the level of Crspecies in the tannery wastewater to comment on its suit-ability andor predict the threats from its presence Thusthe wastewater was analyzed for its total Cr concentrationand speciation was carried out using the UV-Vis methodTotal concentrations of Cr in wastewater samples takenat different distances along the wastewater channel werepresented in Figure 2 The results indicated a decrease in thetotal concentration along distance from the effluent dischargepoint with maximum of 39696 plusmn 0326mgL close to thedischarge point and minimum of 19126 plusmn 0864mgL atfarther (downstream) distance from the discharge point
4 International Journal of Analytical Chemistry
1 2 3 4 50
5
10
15
20
25
30
35
40
45
Distance from effluent discharge point (times500 m)
Tota
l Cr (
mgL
minus1)
Figure 2 Mean values and standard deviations of total Cr con-centrations recorded in wastewater samples collected at differentdistances from the tannery effluent discharge point
Moreover the decreasing concentration of both forms of Cralong the wastewater channel was recorded which indicatedthe dependence of the level of environmental contaminationon the intensity of industrial processes and proximity to thesources [4] Because as the wastewater flows farther fromthe discharge point adsorption of the metal within the wallsof the wastewater channel soil can occur Besides since theCr in the wastewater can exist either in particulate form orassociated with particulates or in solution precipitation ofthe particulates can result in a decrease in the Cr concen-tration downstream [3] The concentrations of Cr recordeddownstream (near the final discharge point 15 km fromthe tannery) were also significantly higher as compared tothe 1998 WHO standards for the limits of Cr in effluentdischarges (Geneva) which is 1mgLminus1 The high value ofCr detected in the water samples above is attributed to thefact that Cr is commonly used as tanning agent and thelow efficiency of the current wastewater treatment processemployed by the tannery The above findings indicated theunfortunate use of the tannery wastewater for irrigation aswell as fishing might lead to health problems and otherenvironmental implications in humans and animals
33 Levels of Cr in Downstream Agricultural Soil The ele-vated level of Cr detected in the wastewater that decreaseswith distance from the effluent source indicated the possibleabsorption of some forms of Cr into soils This can leadto an increase in local chromium concentration in soilsTherefore knowledge of the level of chromium in soils inthe tannery waste catchment area is important to commenton the agricultural and environmental suitability of the soilsand predict the potential hazards due to the Cr presenceThe average concentrations of total Cr in the agricultural soilsamples collected 10m away from the wastewater channeland at different distances from the tannery effluent dischargepoint were presented in Figure 3 The maximum average
10 15 20 25 30 35 40
200
400
600
800
1000
1200
1400
1600
Distance from effluent discharge point (times200 m)
Tota
l Cr (
mgmiddot
Kgminus1)
Figure 3 Mean values and standard deviations of total Cr con-centrations recorded in soil samples collected 10m away from thewastewater channel and at different distances from the tanneryeffluent discharge point
concentration was 1581667 plusmn 0122mgKg correspondingto a sample collected at closest distance (200m) to theeffluent discharge point and the lowest concentration was16225 plusmn 012mgkg which corresponded to sample at 1 kmfarther from the effluent discharge point The levels of Crrecorded in the agricultural soil samples collected up to1 km distance farther from the tannery effluent were higherthan the mean concentration of total Cr recorded in controlagricultural soil collected from remote (20 km) areas Theelevated concentration of Cr in the agricultural soil in thevicinity of tanning industry might thus be attributed to thedisposal of Cr contaminated sludge to the environment by theindustry All the recorded values were above the values givenin the National Environmental Quality Standards (NEQS) ofsoil which is 20mgkg Interestingly the levels of Cr in soilsamples are higher than that of water samples as expectedfrom the continuous accumulation of the contaminant in thesoil ANOVA also showed that mean concentrations of Crin soil and water samples were statistically significant (119901 =005) In addition the mean concentrations of soil as wellas water samples varied significantly with distances from theeffluent source In addition to this the levels of Cr in the agri-cultural soil in the vicinity of the tannery were significantlydifferent from the value recorded with control soil sampleswhich is collected from the remote areas of the tannery Thewide distribution of the contaminant along the agriculturalsoil might be partly due to the migration and partly becauseof the use of the wastewater for irrigation purpose Theabove findings point to the importance of demarcation ofagricultural areas with reference to the industrial areas toensure good practice and welfare of human beings
34 Speciation of Cr(III) and Cr(VI) in Downstream Effluentand Soil The extent of environmental impact of Cr dependsinter alia on its mobility which in turn depends on its
International Journal of Analytical Chemistry 5
Table 1 Speciation of Cr(III) and Cr(VI) in water agricultural soil and vegetables (mgsdotKgminus1)
119882119899119882 = water sample and 119899 = distance from effluent source 119878119898 119878 = soil sample and119898 = distance from the effluent source
speciation [5] The trivalent and hexavalent forms of Cr havedifferent mobility and environmental impact Thus it wasimportant to conduct speciation of the different forms ofthe element in the investigated environmental samples Theresults of speciation study were summarized in Table 1 whereit can be seen that the trivalent form is the dominant formAlthough the trivalent form is the most expected form inthe tannery effluents the incidence of the hexavalent formrecorded in water (max 0322 plusmn 007mgL and min 012 plusmn0014mgL) might be attributed to redox reactions occurringin the sludge mediated by other inorganic and organiccomponents [22] The average concentration of chromium(VI) in soil samples ranged from 223plusmn0032mgkg to 117plusmn002mgKg with the extreme values corresponding to 200mand 800m sampling sites Interestingly concentration ofCr(VI) detected in soil samples was higher than that of watersamples This indicated accumulation of Cr(VI) in the soilsamples over years of exposure to the tannery effluent Theresults also showed the fact that the extent of environmentalcontamination or impact of both forms of the elementdepends on the intensity of production and proximity to thetanning industry [4]Thus the unfortunate use of the tanneryeffluents for irrigation by the rural population living in thevicinity of the wastewater channel means their exposureto the potential hazards of the hexavalent Cr including itscorrosive effect to flesh toxicity and carcinogenicity [11]Children are more exposed to these effects as they used playwith soils andmud while guarding cattle in the contaminatedareas
35 Levels of Cr in Downstream Effluent Irrigated VegetablesThe tannery effluent irrigated cultivation of vegetables mightlead to appreciable concentration of themetal accumulated intheir tissueThis not only can have impact on the productivitybut also make the vegetables unsuitable for consumptionWhen we know that the wastewater that is used for irrigationof vegetables contains elevated concentration of Cr we shouldbe curious about its level in the plants Indeed the level ofCr that can be accumulated in plant tissues not only depends
0
2
4
6
8
10
Tannery areaControl
Green pepperCabbageTomatoOnion
Tota
l Cr (
mgmiddot
Kgminus1)
Figure 4 Mean values and standard deviations of total Cr con-centrations recorded in tannery effluent irrigated vegetable samplescultivated around (1 km radius) tannery location
on its presence in the soil but varies among plants In thecurrent study four major vegetables grown in the study areaincluding cabbage onion green pepper and tomato weretested for the level of Cr accumulated in the edible part of theplantsThe average chromium concentrations (mgkg) foundin the vegetable samples collected near the Ethiopia TanneryShare Company and control areas are presented in Figure 4The highest level of Cr was recorded in onion root (1175 plusmn0206mgKg) and the lowest level was recorded in greenpepper fruit (575 plusmn 018mgKg) The highest and the lowestlevels of Cr detected in control samples were 3341667 plusmn0075mgKg in onion root and 1075833plusmn0053482mgKg ingreen pepper fruits respectively The levels of Cr in the fourvegetables follow the increasing order green pepper fruittomato fruit cabbage and onion root Onions were found
6 International Journal of Analytical Chemistry
to contain highest load of Cr This is consistent with thefact that plants accumulate the highest level of Cr in roots[27] The highest level of Cr recorded in onion root (1175 plusmn0206mgKg) was also comparable to the previous report(11mgkg) [28] The highest level of Cr(VI) was detected inthe root of onion (0048plusmn0065mgKg) and the lowest in fruitof green pepper (0004 plusmn 0007mgKg) Other authors havereported a range of Cr load in plants irrigated with tannerywastewater [8 29] But in the context of 167mgsdotkgminus1 of Crdetected in the plants taken from a rural area exposed tocement factory emissions [29] the levels of Cr in the testedvegetable samples in the current study were not as highlycontaminated as reported before However the levels of Crdetected in all the investigated vegetable samples were stillabove the permissible limit set by WHO (1988) which is019mgsdotkgminus1
4 Conclusions
The speciation of Cr(III) and Cr(VI) was successfully carriedout in soil water and vegetables samples collected at thetanning industry area using spectrophotometric methodsThe study showed that all the investigated environmentalsamples including agricultural soil and vegetables containhigh load of Cr(III) The levels of both forms of Cr (trivalentand hexavalent) in soil and water samples were above theWHO standards and showed decreasing trend with distancefrom the tannery effluent discharge point Soil samples in thevicinity of the tanning industry contained elevated load ofCr indicating the unsuitability for agricultural purposes andpotential hazards to human beings and animals if appropriateclean up strategy is implemented All the tested vegetables(cabbage onion tomato and green pepper) contained abovepermissible levels of Cr(III) in their tissue with the highestconcentration found in the edible root parts of onion Cr(VI)is not detected in the vegetable samples probably due tolack of absorption ANOVA showed that variations of thelevel of Cr among the tested vegetables were statisticallysignificant This confirmed that the chromium absorptionfrom the soil by vegetables depends on the plant specieswith highest accumulation in roots In the agricultural soilin the vicinity of the tannery the levels of Cr(III) andCr(VI) were much greater compared to control soil samplescollected at remote areas In conclusion the discharge of Crrich sludge to the environment and the unfortunate use foragricultural purposes by the community living in the vicinityof the effluent channel can lead to potential hazards of Crparticularly the hexavalent form on humans and affect thequality of the natural resources around the tanning industryTherefore appropriate reclamation methods are crucial toreducing Cr contamination
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors are very grateful to Hawassa University (HU)for providing laboratory facility for the conduct of the
experiments Dereje Homa is also grateful to the Office ofResearch and Technology Transfer of HU for partial financialsupport during the study
References
[1] J O Nriagu ldquoProduction and uses of chromiumrdquo in Chromiumin Natural and Human Environments J O Nriagu and ENieboer Eds pp 81ndash104 Wiley Interscience New York NYUSA 1988
[2] S Mishra V Singh S Srivastava et al ldquoStudies on uptake oftrivalent and hexavalent chromium by maize (Zea mays)rdquo Foodand Chemical Toxicology vol 33 no 5 pp 393ndash397 1995
[3] R Shrivastava R K Upreti P K Seth and U C ChaturvedildquoEffects of chromium on the immune systemrdquo FEMS Immunol-ogy and Medical Microbiology vol 34 no 1 pp 1ndash7 2002
[4] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[5] A D Apte S Verma V Tare and P Bose ldquoOxidation of Cr(III)in tannery sludge to Cr(VI) field observations and theoreticalassessmentrdquo Journal of HazardousMaterials vol 121 no 1ndash3 pp215ndash222 2005
[6] Z Stępniewska and A Wolinska ldquoSoil dehydrogenase activityin the presence of chromium (III) and (VI)rdquo InternationalAgrophysics vol 19 no 1 pp 79ndash83 2005
[7] R A Anderson ldquoChromium in the prevention and control ofdiabetesrdquoDiabetes ampMetabolism vol 26 no 1 pp 22ndash27 2000
[8] C Bini L Maleci and A Romanin ldquoThe chromium issue insoils of the leather tannery district in Italyrdquo Journal of Geochem-ical Exploration vol 96 no 2-3 pp 194ndash202 2008
[9] B R James J C Petura R J Vitale and G R MussolineldquoOxidation-reduction chemistry of chromium relevance to theregulation and remediation of chromate-contaminated soilsrdquoJournal of Soil Contamination vol 6 no 6 pp 569ndash580 1997
[10] P H Masscheleyn J H Pardue R D DeLaune and W HPatrick Jr ldquoChromium redox chemistry in a Lower MississippiValley bottomland hardwood wetlandrdquo Environmental Scienceand Technology vol 26 no 6 pp 1217ndash1226 1992
[11] A P Das and S Mishra ldquoHexavalent chromium (VI) environ-ment pollutant and health hazardrdquo Journal of EnvironmentalResearch and Development vol 2 no 3 pp 386ndash392 2008
[12] MMwinyihija Ecotoxicological Diagnosis in the Tanning Indus-try Springer Berlin Germany 2010
[13] M Mwinyihija A Meharg J Dawson N J C Strachan andK Killham ldquoAn ecotoxicological approach to assessing theimpact of tanning industry effluent on river healthrdquo Archives ofEnvironmental Contamination and Toxicology vol 50 no 3 pp316ndash324 2006
[14] M Mwinyihija N J C Strachan A Meharg and K KillhamldquoBiosensor based toxicity dissection of tannery and associ-ated environmental samplesrdquo Journal of the American LeatherChemists Association vol 100 no 12 pp 481ndash490 2005
[15] A H Reda ldquoStudy on the pollution levels of trace metals frommodjo tannery effluent in the surrounding river water and soilrdquoScience Journal of Analytical Chemistry vol 3 no 5 pp 56ndash602015
[16] A Cassano L Della Pietra and E Drioli ldquoIntegrated mem-brane process for the recovery of chromium salts from tanneryeffluentsrdquo Industrial amp Engineering Chemistry Research vol 46no 21 pp 6825ndash6830 2007
International Journal of Analytical Chemistry 7
[17] R Aravindhan B Madhan J R Rao B U Nair and T Ramas-ami ldquoBioaccumulation of chromium from tannery wastewateran approach for chrome recovery and reuserdquo EnvironmentalScience and Technology vol 38 no 1 pp 300ndash306 2004
[18] T Reemtsma and M Jekel ldquoDissolved organics in tannerywastewaters and their alteration by a combined anaerobic andaerobic treatmentrdquoWater Research vol 31 no 5 pp 1035ndash10461997
[19] E Bouwer N Durant L Wilson W Zhang and A Cunning-ham ldquoDegradation of xenobiotic compounds in situ capabili-ties and limitsrdquo FEMSMicrobiology Reviews vol 15 no 2-3 pp307ndash317 1994
[20] A Cassano R Molinari M Romano and E Drioli ldquoTreatmentof aqueous effluents of the leather industry by membraneprocesses a reviewrdquo Journal of Membrane Science vol 181 no 1pp 111ndash126 2001
[21] V J Sundar J R Rao and C Muralidharan ldquoCleaner chrometanningmdashemerging optionsrdquo Journal of Cleaner Production vol10 no 1 pp 69ndash74 2002
[22] Z Stepniewska K Bucior and R P Bennicelli ldquoThe effects ofMnO
2on sorption and oxidation of Cr(III) by soilsrdquoGeoderma
vol 122 no 2ndash4 pp 291ndash296 2004[23] R J Bartlett and J M Kimble ldquoBehavior of chromium in soils
oxidationrdquo Journal of Environmental Quality vol 8 pp 31ndash351976
[24] N R Jyothi NAM FarookMCho and J Shim ldquoAnalysis andspeciation of chromium in environmental matrices by variousanalytical techniquesrdquoAsian Journal of Chemistry vol 25 no 8pp 4125ndash4136 2013
[25] M Noroozifar and M Khorasani-Motlagh ldquoSpecific extractionof chromium as tetrabutylammonium-chromate and spec-trophotometric determination by diphenylcarbazide specia-tion of chromium in effluent streamsrdquo Analytical Sciences vol19 no 5 pp 705ndash708 2003
[26] J C Akan B G Kolo B S Yikala andV O Ogugbuaja ldquoDeter-minations of some heavy metals in vegetable samples from BiuLocal Government Area Borno State North Eastern NigeriardquoInternational Journal of EnvironmentalMonitoring andAnalysisvol 1 no 2 pp 40ndash46 2013
[27] R S Bai and T E Abraham ldquoBiosorption of Cr (VI) from aque-ous solution byRhizopus nigricansrdquo Bioresource Technology vol79 no 1 pp 73ndash81 2001
[28] A Wolinska Z Stępniewska and R Włosek ldquoThe influenceof old leather tannery district on chromium contamination ofsoils water and plantsrdquoNatural Science vol 05 no 02 pp 253ndash258 2013
[29] B Isikli T A Demir SM Urer A Berber T Akar andC Kaly-oncu ldquoEffects of chromium exposure from a cement factoryrdquoEnvironmental Research vol 91 no 2 pp 113ndash118 2003
Distance from effluent discharge point (times500 m)
Tota
l Cr (
mgL
minus1)
Figure 2 Mean values and standard deviations of total Cr con-centrations recorded in wastewater samples collected at differentdistances from the tannery effluent discharge point
Moreover the decreasing concentration of both forms of Cralong the wastewater channel was recorded which indicatedthe dependence of the level of environmental contaminationon the intensity of industrial processes and proximity to thesources [4] Because as the wastewater flows farther fromthe discharge point adsorption of the metal within the wallsof the wastewater channel soil can occur Besides since theCr in the wastewater can exist either in particulate form orassociated with particulates or in solution precipitation ofthe particulates can result in a decrease in the Cr concen-tration downstream [3] The concentrations of Cr recordeddownstream (near the final discharge point 15 km fromthe tannery) were also significantly higher as compared tothe 1998 WHO standards for the limits of Cr in effluentdischarges (Geneva) which is 1mgLminus1 The high value ofCr detected in the water samples above is attributed to thefact that Cr is commonly used as tanning agent and thelow efficiency of the current wastewater treatment processemployed by the tannery The above findings indicated theunfortunate use of the tannery wastewater for irrigation aswell as fishing might lead to health problems and otherenvironmental implications in humans and animals
33 Levels of Cr in Downstream Agricultural Soil The ele-vated level of Cr detected in the wastewater that decreaseswith distance from the effluent source indicated the possibleabsorption of some forms of Cr into soils This can leadto an increase in local chromium concentration in soilsTherefore knowledge of the level of chromium in soils inthe tannery waste catchment area is important to commenton the agricultural and environmental suitability of the soilsand predict the potential hazards due to the Cr presenceThe average concentrations of total Cr in the agricultural soilsamples collected 10m away from the wastewater channeland at different distances from the tannery effluent dischargepoint were presented in Figure 3 The maximum average
10 15 20 25 30 35 40
200
400
600
800
1000
1200
1400
1600
Distance from effluent discharge point (times200 m)
Tota
l Cr (
mgmiddot
Kgminus1)
Figure 3 Mean values and standard deviations of total Cr con-centrations recorded in soil samples collected 10m away from thewastewater channel and at different distances from the tanneryeffluent discharge point
concentration was 1581667 plusmn 0122mgKg correspondingto a sample collected at closest distance (200m) to theeffluent discharge point and the lowest concentration was16225 plusmn 012mgkg which corresponded to sample at 1 kmfarther from the effluent discharge point The levels of Crrecorded in the agricultural soil samples collected up to1 km distance farther from the tannery effluent were higherthan the mean concentration of total Cr recorded in controlagricultural soil collected from remote (20 km) areas Theelevated concentration of Cr in the agricultural soil in thevicinity of tanning industry might thus be attributed to thedisposal of Cr contaminated sludge to the environment by theindustry All the recorded values were above the values givenin the National Environmental Quality Standards (NEQS) ofsoil which is 20mgkg Interestingly the levels of Cr in soilsamples are higher than that of water samples as expectedfrom the continuous accumulation of the contaminant in thesoil ANOVA also showed that mean concentrations of Crin soil and water samples were statistically significant (119901 =005) In addition the mean concentrations of soil as wellas water samples varied significantly with distances from theeffluent source In addition to this the levels of Cr in the agri-cultural soil in the vicinity of the tannery were significantlydifferent from the value recorded with control soil sampleswhich is collected from the remote areas of the tannery Thewide distribution of the contaminant along the agriculturalsoil might be partly due to the migration and partly becauseof the use of the wastewater for irrigation purpose Theabove findings point to the importance of demarcation ofagricultural areas with reference to the industrial areas toensure good practice and welfare of human beings
34 Speciation of Cr(III) and Cr(VI) in Downstream Effluentand Soil The extent of environmental impact of Cr dependsinter alia on its mobility which in turn depends on its
International Journal of Analytical Chemistry 5
Table 1 Speciation of Cr(III) and Cr(VI) in water agricultural soil and vegetables (mgsdotKgminus1)
119882119899119882 = water sample and 119899 = distance from effluent source 119878119898 119878 = soil sample and119898 = distance from the effluent source
speciation [5] The trivalent and hexavalent forms of Cr havedifferent mobility and environmental impact Thus it wasimportant to conduct speciation of the different forms ofthe element in the investigated environmental samples Theresults of speciation study were summarized in Table 1 whereit can be seen that the trivalent form is the dominant formAlthough the trivalent form is the most expected form inthe tannery effluents the incidence of the hexavalent formrecorded in water (max 0322 plusmn 007mgL and min 012 plusmn0014mgL) might be attributed to redox reactions occurringin the sludge mediated by other inorganic and organiccomponents [22] The average concentration of chromium(VI) in soil samples ranged from 223plusmn0032mgkg to 117plusmn002mgKg with the extreme values corresponding to 200mand 800m sampling sites Interestingly concentration ofCr(VI) detected in soil samples was higher than that of watersamples This indicated accumulation of Cr(VI) in the soilsamples over years of exposure to the tannery effluent Theresults also showed the fact that the extent of environmentalcontamination or impact of both forms of the elementdepends on the intensity of production and proximity to thetanning industry [4]Thus the unfortunate use of the tanneryeffluents for irrigation by the rural population living in thevicinity of the wastewater channel means their exposureto the potential hazards of the hexavalent Cr including itscorrosive effect to flesh toxicity and carcinogenicity [11]Children are more exposed to these effects as they used playwith soils andmud while guarding cattle in the contaminatedareas
35 Levels of Cr in Downstream Effluent Irrigated VegetablesThe tannery effluent irrigated cultivation of vegetables mightlead to appreciable concentration of themetal accumulated intheir tissueThis not only can have impact on the productivitybut also make the vegetables unsuitable for consumptionWhen we know that the wastewater that is used for irrigationof vegetables contains elevated concentration of Cr we shouldbe curious about its level in the plants Indeed the level ofCr that can be accumulated in plant tissues not only depends
0
2
4
6
8
10
Tannery areaControl
Green pepperCabbageTomatoOnion
Tota
l Cr (
mgmiddot
Kgminus1)
Figure 4 Mean values and standard deviations of total Cr con-centrations recorded in tannery effluent irrigated vegetable samplescultivated around (1 km radius) tannery location
on its presence in the soil but varies among plants In thecurrent study four major vegetables grown in the study areaincluding cabbage onion green pepper and tomato weretested for the level of Cr accumulated in the edible part of theplantsThe average chromium concentrations (mgkg) foundin the vegetable samples collected near the Ethiopia TanneryShare Company and control areas are presented in Figure 4The highest level of Cr was recorded in onion root (1175 plusmn0206mgKg) and the lowest level was recorded in greenpepper fruit (575 plusmn 018mgKg) The highest and the lowestlevels of Cr detected in control samples were 3341667 plusmn0075mgKg in onion root and 1075833plusmn0053482mgKg ingreen pepper fruits respectively The levels of Cr in the fourvegetables follow the increasing order green pepper fruittomato fruit cabbage and onion root Onions were found
6 International Journal of Analytical Chemistry
to contain highest load of Cr This is consistent with thefact that plants accumulate the highest level of Cr in roots[27] The highest level of Cr recorded in onion root (1175 plusmn0206mgKg) was also comparable to the previous report(11mgkg) [28] The highest level of Cr(VI) was detected inthe root of onion (0048plusmn0065mgKg) and the lowest in fruitof green pepper (0004 plusmn 0007mgKg) Other authors havereported a range of Cr load in plants irrigated with tannerywastewater [8 29] But in the context of 167mgsdotkgminus1 of Crdetected in the plants taken from a rural area exposed tocement factory emissions [29] the levels of Cr in the testedvegetable samples in the current study were not as highlycontaminated as reported before However the levels of Crdetected in all the investigated vegetable samples were stillabove the permissible limit set by WHO (1988) which is019mgsdotkgminus1
4 Conclusions
The speciation of Cr(III) and Cr(VI) was successfully carriedout in soil water and vegetables samples collected at thetanning industry area using spectrophotometric methodsThe study showed that all the investigated environmentalsamples including agricultural soil and vegetables containhigh load of Cr(III) The levels of both forms of Cr (trivalentand hexavalent) in soil and water samples were above theWHO standards and showed decreasing trend with distancefrom the tannery effluent discharge point Soil samples in thevicinity of the tanning industry contained elevated load ofCr indicating the unsuitability for agricultural purposes andpotential hazards to human beings and animals if appropriateclean up strategy is implemented All the tested vegetables(cabbage onion tomato and green pepper) contained abovepermissible levels of Cr(III) in their tissue with the highestconcentration found in the edible root parts of onion Cr(VI)is not detected in the vegetable samples probably due tolack of absorption ANOVA showed that variations of thelevel of Cr among the tested vegetables were statisticallysignificant This confirmed that the chromium absorptionfrom the soil by vegetables depends on the plant specieswith highest accumulation in roots In the agricultural soilin the vicinity of the tannery the levels of Cr(III) andCr(VI) were much greater compared to control soil samplescollected at remote areas In conclusion the discharge of Crrich sludge to the environment and the unfortunate use foragricultural purposes by the community living in the vicinityof the effluent channel can lead to potential hazards of Crparticularly the hexavalent form on humans and affect thequality of the natural resources around the tanning industryTherefore appropriate reclamation methods are crucial toreducing Cr contamination
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors are very grateful to Hawassa University (HU)for providing laboratory facility for the conduct of the
experiments Dereje Homa is also grateful to the Office ofResearch and Technology Transfer of HU for partial financialsupport during the study
References
[1] J O Nriagu ldquoProduction and uses of chromiumrdquo in Chromiumin Natural and Human Environments J O Nriagu and ENieboer Eds pp 81ndash104 Wiley Interscience New York NYUSA 1988
[2] S Mishra V Singh S Srivastava et al ldquoStudies on uptake oftrivalent and hexavalent chromium by maize (Zea mays)rdquo Foodand Chemical Toxicology vol 33 no 5 pp 393ndash397 1995
[3] R Shrivastava R K Upreti P K Seth and U C ChaturvedildquoEffects of chromium on the immune systemrdquo FEMS Immunol-ogy and Medical Microbiology vol 34 no 1 pp 1ndash7 2002
[4] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[5] A D Apte S Verma V Tare and P Bose ldquoOxidation of Cr(III)in tannery sludge to Cr(VI) field observations and theoreticalassessmentrdquo Journal of HazardousMaterials vol 121 no 1ndash3 pp215ndash222 2005
[6] Z Stępniewska and A Wolinska ldquoSoil dehydrogenase activityin the presence of chromium (III) and (VI)rdquo InternationalAgrophysics vol 19 no 1 pp 79ndash83 2005
[7] R A Anderson ldquoChromium in the prevention and control ofdiabetesrdquoDiabetes ampMetabolism vol 26 no 1 pp 22ndash27 2000
[8] C Bini L Maleci and A Romanin ldquoThe chromium issue insoils of the leather tannery district in Italyrdquo Journal of Geochem-ical Exploration vol 96 no 2-3 pp 194ndash202 2008
[9] B R James J C Petura R J Vitale and G R MussolineldquoOxidation-reduction chemistry of chromium relevance to theregulation and remediation of chromate-contaminated soilsrdquoJournal of Soil Contamination vol 6 no 6 pp 569ndash580 1997
[10] P H Masscheleyn J H Pardue R D DeLaune and W HPatrick Jr ldquoChromium redox chemistry in a Lower MississippiValley bottomland hardwood wetlandrdquo Environmental Scienceand Technology vol 26 no 6 pp 1217ndash1226 1992
[11] A P Das and S Mishra ldquoHexavalent chromium (VI) environ-ment pollutant and health hazardrdquo Journal of EnvironmentalResearch and Development vol 2 no 3 pp 386ndash392 2008
[12] MMwinyihija Ecotoxicological Diagnosis in the Tanning Indus-try Springer Berlin Germany 2010
[13] M Mwinyihija A Meharg J Dawson N J C Strachan andK Killham ldquoAn ecotoxicological approach to assessing theimpact of tanning industry effluent on river healthrdquo Archives ofEnvironmental Contamination and Toxicology vol 50 no 3 pp316ndash324 2006
[14] M Mwinyihija N J C Strachan A Meharg and K KillhamldquoBiosensor based toxicity dissection of tannery and associ-ated environmental samplesrdquo Journal of the American LeatherChemists Association vol 100 no 12 pp 481ndash490 2005
[15] A H Reda ldquoStudy on the pollution levels of trace metals frommodjo tannery effluent in the surrounding river water and soilrdquoScience Journal of Analytical Chemistry vol 3 no 5 pp 56ndash602015
[16] A Cassano L Della Pietra and E Drioli ldquoIntegrated mem-brane process for the recovery of chromium salts from tanneryeffluentsrdquo Industrial amp Engineering Chemistry Research vol 46no 21 pp 6825ndash6830 2007
International Journal of Analytical Chemistry 7
[17] R Aravindhan B Madhan J R Rao B U Nair and T Ramas-ami ldquoBioaccumulation of chromium from tannery wastewateran approach for chrome recovery and reuserdquo EnvironmentalScience and Technology vol 38 no 1 pp 300ndash306 2004
[18] T Reemtsma and M Jekel ldquoDissolved organics in tannerywastewaters and their alteration by a combined anaerobic andaerobic treatmentrdquoWater Research vol 31 no 5 pp 1035ndash10461997
[19] E Bouwer N Durant L Wilson W Zhang and A Cunning-ham ldquoDegradation of xenobiotic compounds in situ capabili-ties and limitsrdquo FEMSMicrobiology Reviews vol 15 no 2-3 pp307ndash317 1994
[20] A Cassano R Molinari M Romano and E Drioli ldquoTreatmentof aqueous effluents of the leather industry by membraneprocesses a reviewrdquo Journal of Membrane Science vol 181 no 1pp 111ndash126 2001
[21] V J Sundar J R Rao and C Muralidharan ldquoCleaner chrometanningmdashemerging optionsrdquo Journal of Cleaner Production vol10 no 1 pp 69ndash74 2002
[22] Z Stepniewska K Bucior and R P Bennicelli ldquoThe effects ofMnO
2on sorption and oxidation of Cr(III) by soilsrdquoGeoderma
vol 122 no 2ndash4 pp 291ndash296 2004[23] R J Bartlett and J M Kimble ldquoBehavior of chromium in soils
oxidationrdquo Journal of Environmental Quality vol 8 pp 31ndash351976
[24] N R Jyothi NAM FarookMCho and J Shim ldquoAnalysis andspeciation of chromium in environmental matrices by variousanalytical techniquesrdquoAsian Journal of Chemistry vol 25 no 8pp 4125ndash4136 2013
[25] M Noroozifar and M Khorasani-Motlagh ldquoSpecific extractionof chromium as tetrabutylammonium-chromate and spec-trophotometric determination by diphenylcarbazide specia-tion of chromium in effluent streamsrdquo Analytical Sciences vol19 no 5 pp 705ndash708 2003
[26] J C Akan B G Kolo B S Yikala andV O Ogugbuaja ldquoDeter-minations of some heavy metals in vegetable samples from BiuLocal Government Area Borno State North Eastern NigeriardquoInternational Journal of EnvironmentalMonitoring andAnalysisvol 1 no 2 pp 40ndash46 2013
[27] R S Bai and T E Abraham ldquoBiosorption of Cr (VI) from aque-ous solution byRhizopus nigricansrdquo Bioresource Technology vol79 no 1 pp 73ndash81 2001
[28] A Wolinska Z Stępniewska and R Włosek ldquoThe influenceof old leather tannery district on chromium contamination ofsoils water and plantsrdquoNatural Science vol 05 no 02 pp 253ndash258 2013
[29] B Isikli T A Demir SM Urer A Berber T Akar andC Kaly-oncu ldquoEffects of chromium exposure from a cement factoryrdquoEnvironmental Research vol 91 no 2 pp 113ndash118 2003
119882119899119882 = water sample and 119899 = distance from effluent source 119878119898 119878 = soil sample and119898 = distance from the effluent source
speciation [5] The trivalent and hexavalent forms of Cr havedifferent mobility and environmental impact Thus it wasimportant to conduct speciation of the different forms ofthe element in the investigated environmental samples Theresults of speciation study were summarized in Table 1 whereit can be seen that the trivalent form is the dominant formAlthough the trivalent form is the most expected form inthe tannery effluents the incidence of the hexavalent formrecorded in water (max 0322 plusmn 007mgL and min 012 plusmn0014mgL) might be attributed to redox reactions occurringin the sludge mediated by other inorganic and organiccomponents [22] The average concentration of chromium(VI) in soil samples ranged from 223plusmn0032mgkg to 117plusmn002mgKg with the extreme values corresponding to 200mand 800m sampling sites Interestingly concentration ofCr(VI) detected in soil samples was higher than that of watersamples This indicated accumulation of Cr(VI) in the soilsamples over years of exposure to the tannery effluent Theresults also showed the fact that the extent of environmentalcontamination or impact of both forms of the elementdepends on the intensity of production and proximity to thetanning industry [4]Thus the unfortunate use of the tanneryeffluents for irrigation by the rural population living in thevicinity of the wastewater channel means their exposureto the potential hazards of the hexavalent Cr including itscorrosive effect to flesh toxicity and carcinogenicity [11]Children are more exposed to these effects as they used playwith soils andmud while guarding cattle in the contaminatedareas
35 Levels of Cr in Downstream Effluent Irrigated VegetablesThe tannery effluent irrigated cultivation of vegetables mightlead to appreciable concentration of themetal accumulated intheir tissueThis not only can have impact on the productivitybut also make the vegetables unsuitable for consumptionWhen we know that the wastewater that is used for irrigationof vegetables contains elevated concentration of Cr we shouldbe curious about its level in the plants Indeed the level ofCr that can be accumulated in plant tissues not only depends
0
2
4
6
8
10
Tannery areaControl
Green pepperCabbageTomatoOnion
Tota
l Cr (
mgmiddot
Kgminus1)
Figure 4 Mean values and standard deviations of total Cr con-centrations recorded in tannery effluent irrigated vegetable samplescultivated around (1 km radius) tannery location
on its presence in the soil but varies among plants In thecurrent study four major vegetables grown in the study areaincluding cabbage onion green pepper and tomato weretested for the level of Cr accumulated in the edible part of theplantsThe average chromium concentrations (mgkg) foundin the vegetable samples collected near the Ethiopia TanneryShare Company and control areas are presented in Figure 4The highest level of Cr was recorded in onion root (1175 plusmn0206mgKg) and the lowest level was recorded in greenpepper fruit (575 plusmn 018mgKg) The highest and the lowestlevels of Cr detected in control samples were 3341667 plusmn0075mgKg in onion root and 1075833plusmn0053482mgKg ingreen pepper fruits respectively The levels of Cr in the fourvegetables follow the increasing order green pepper fruittomato fruit cabbage and onion root Onions were found
6 International Journal of Analytical Chemistry
to contain highest load of Cr This is consistent with thefact that plants accumulate the highest level of Cr in roots[27] The highest level of Cr recorded in onion root (1175 plusmn0206mgKg) was also comparable to the previous report(11mgkg) [28] The highest level of Cr(VI) was detected inthe root of onion (0048plusmn0065mgKg) and the lowest in fruitof green pepper (0004 plusmn 0007mgKg) Other authors havereported a range of Cr load in plants irrigated with tannerywastewater [8 29] But in the context of 167mgsdotkgminus1 of Crdetected in the plants taken from a rural area exposed tocement factory emissions [29] the levels of Cr in the testedvegetable samples in the current study were not as highlycontaminated as reported before However the levels of Crdetected in all the investigated vegetable samples were stillabove the permissible limit set by WHO (1988) which is019mgsdotkgminus1
4 Conclusions
The speciation of Cr(III) and Cr(VI) was successfully carriedout in soil water and vegetables samples collected at thetanning industry area using spectrophotometric methodsThe study showed that all the investigated environmentalsamples including agricultural soil and vegetables containhigh load of Cr(III) The levels of both forms of Cr (trivalentand hexavalent) in soil and water samples were above theWHO standards and showed decreasing trend with distancefrom the tannery effluent discharge point Soil samples in thevicinity of the tanning industry contained elevated load ofCr indicating the unsuitability for agricultural purposes andpotential hazards to human beings and animals if appropriateclean up strategy is implemented All the tested vegetables(cabbage onion tomato and green pepper) contained abovepermissible levels of Cr(III) in their tissue with the highestconcentration found in the edible root parts of onion Cr(VI)is not detected in the vegetable samples probably due tolack of absorption ANOVA showed that variations of thelevel of Cr among the tested vegetables were statisticallysignificant This confirmed that the chromium absorptionfrom the soil by vegetables depends on the plant specieswith highest accumulation in roots In the agricultural soilin the vicinity of the tannery the levels of Cr(III) andCr(VI) were much greater compared to control soil samplescollected at remote areas In conclusion the discharge of Crrich sludge to the environment and the unfortunate use foragricultural purposes by the community living in the vicinityof the effluent channel can lead to potential hazards of Crparticularly the hexavalent form on humans and affect thequality of the natural resources around the tanning industryTherefore appropriate reclamation methods are crucial toreducing Cr contamination
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors are very grateful to Hawassa University (HU)for providing laboratory facility for the conduct of the
experiments Dereje Homa is also grateful to the Office ofResearch and Technology Transfer of HU for partial financialsupport during the study
References
[1] J O Nriagu ldquoProduction and uses of chromiumrdquo in Chromiumin Natural and Human Environments J O Nriagu and ENieboer Eds pp 81ndash104 Wiley Interscience New York NYUSA 1988
[2] S Mishra V Singh S Srivastava et al ldquoStudies on uptake oftrivalent and hexavalent chromium by maize (Zea mays)rdquo Foodand Chemical Toxicology vol 33 no 5 pp 393ndash397 1995
[3] R Shrivastava R K Upreti P K Seth and U C ChaturvedildquoEffects of chromium on the immune systemrdquo FEMS Immunol-ogy and Medical Microbiology vol 34 no 1 pp 1ndash7 2002
[4] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[5] A D Apte S Verma V Tare and P Bose ldquoOxidation of Cr(III)in tannery sludge to Cr(VI) field observations and theoreticalassessmentrdquo Journal of HazardousMaterials vol 121 no 1ndash3 pp215ndash222 2005
[6] Z Stępniewska and A Wolinska ldquoSoil dehydrogenase activityin the presence of chromium (III) and (VI)rdquo InternationalAgrophysics vol 19 no 1 pp 79ndash83 2005
[7] R A Anderson ldquoChromium in the prevention and control ofdiabetesrdquoDiabetes ampMetabolism vol 26 no 1 pp 22ndash27 2000
[8] C Bini L Maleci and A Romanin ldquoThe chromium issue insoils of the leather tannery district in Italyrdquo Journal of Geochem-ical Exploration vol 96 no 2-3 pp 194ndash202 2008
[9] B R James J C Petura R J Vitale and G R MussolineldquoOxidation-reduction chemistry of chromium relevance to theregulation and remediation of chromate-contaminated soilsrdquoJournal of Soil Contamination vol 6 no 6 pp 569ndash580 1997
[10] P H Masscheleyn J H Pardue R D DeLaune and W HPatrick Jr ldquoChromium redox chemistry in a Lower MississippiValley bottomland hardwood wetlandrdquo Environmental Scienceand Technology vol 26 no 6 pp 1217ndash1226 1992
[11] A P Das and S Mishra ldquoHexavalent chromium (VI) environ-ment pollutant and health hazardrdquo Journal of EnvironmentalResearch and Development vol 2 no 3 pp 386ndash392 2008
[12] MMwinyihija Ecotoxicological Diagnosis in the Tanning Indus-try Springer Berlin Germany 2010
[13] M Mwinyihija A Meharg J Dawson N J C Strachan andK Killham ldquoAn ecotoxicological approach to assessing theimpact of tanning industry effluent on river healthrdquo Archives ofEnvironmental Contamination and Toxicology vol 50 no 3 pp316ndash324 2006
[14] M Mwinyihija N J C Strachan A Meharg and K KillhamldquoBiosensor based toxicity dissection of tannery and associ-ated environmental samplesrdquo Journal of the American LeatherChemists Association vol 100 no 12 pp 481ndash490 2005
[15] A H Reda ldquoStudy on the pollution levels of trace metals frommodjo tannery effluent in the surrounding river water and soilrdquoScience Journal of Analytical Chemistry vol 3 no 5 pp 56ndash602015
[16] A Cassano L Della Pietra and E Drioli ldquoIntegrated mem-brane process for the recovery of chromium salts from tanneryeffluentsrdquo Industrial amp Engineering Chemistry Research vol 46no 21 pp 6825ndash6830 2007
International Journal of Analytical Chemistry 7
[17] R Aravindhan B Madhan J R Rao B U Nair and T Ramas-ami ldquoBioaccumulation of chromium from tannery wastewateran approach for chrome recovery and reuserdquo EnvironmentalScience and Technology vol 38 no 1 pp 300ndash306 2004
[18] T Reemtsma and M Jekel ldquoDissolved organics in tannerywastewaters and their alteration by a combined anaerobic andaerobic treatmentrdquoWater Research vol 31 no 5 pp 1035ndash10461997
[19] E Bouwer N Durant L Wilson W Zhang and A Cunning-ham ldquoDegradation of xenobiotic compounds in situ capabili-ties and limitsrdquo FEMSMicrobiology Reviews vol 15 no 2-3 pp307ndash317 1994
[20] A Cassano R Molinari M Romano and E Drioli ldquoTreatmentof aqueous effluents of the leather industry by membraneprocesses a reviewrdquo Journal of Membrane Science vol 181 no 1pp 111ndash126 2001
[21] V J Sundar J R Rao and C Muralidharan ldquoCleaner chrometanningmdashemerging optionsrdquo Journal of Cleaner Production vol10 no 1 pp 69ndash74 2002
[22] Z Stepniewska K Bucior and R P Bennicelli ldquoThe effects ofMnO
2on sorption and oxidation of Cr(III) by soilsrdquoGeoderma
vol 122 no 2ndash4 pp 291ndash296 2004[23] R J Bartlett and J M Kimble ldquoBehavior of chromium in soils
oxidationrdquo Journal of Environmental Quality vol 8 pp 31ndash351976
[24] N R Jyothi NAM FarookMCho and J Shim ldquoAnalysis andspeciation of chromium in environmental matrices by variousanalytical techniquesrdquoAsian Journal of Chemistry vol 25 no 8pp 4125ndash4136 2013
[25] M Noroozifar and M Khorasani-Motlagh ldquoSpecific extractionof chromium as tetrabutylammonium-chromate and spec-trophotometric determination by diphenylcarbazide specia-tion of chromium in effluent streamsrdquo Analytical Sciences vol19 no 5 pp 705ndash708 2003
[26] J C Akan B G Kolo B S Yikala andV O Ogugbuaja ldquoDeter-minations of some heavy metals in vegetable samples from BiuLocal Government Area Borno State North Eastern NigeriardquoInternational Journal of EnvironmentalMonitoring andAnalysisvol 1 no 2 pp 40ndash46 2013
[27] R S Bai and T E Abraham ldquoBiosorption of Cr (VI) from aque-ous solution byRhizopus nigricansrdquo Bioresource Technology vol79 no 1 pp 73ndash81 2001
[28] A Wolinska Z Stępniewska and R Włosek ldquoThe influenceof old leather tannery district on chromium contamination ofsoils water and plantsrdquoNatural Science vol 05 no 02 pp 253ndash258 2013
[29] B Isikli T A Demir SM Urer A Berber T Akar andC Kaly-oncu ldquoEffects of chromium exposure from a cement factoryrdquoEnvironmental Research vol 91 no 2 pp 113ndash118 2003
to contain highest load of Cr This is consistent with thefact that plants accumulate the highest level of Cr in roots[27] The highest level of Cr recorded in onion root (1175 plusmn0206mgKg) was also comparable to the previous report(11mgkg) [28] The highest level of Cr(VI) was detected inthe root of onion (0048plusmn0065mgKg) and the lowest in fruitof green pepper (0004 plusmn 0007mgKg) Other authors havereported a range of Cr load in plants irrigated with tannerywastewater [8 29] But in the context of 167mgsdotkgminus1 of Crdetected in the plants taken from a rural area exposed tocement factory emissions [29] the levels of Cr in the testedvegetable samples in the current study were not as highlycontaminated as reported before However the levels of Crdetected in all the investigated vegetable samples were stillabove the permissible limit set by WHO (1988) which is019mgsdotkgminus1
4 Conclusions
The speciation of Cr(III) and Cr(VI) was successfully carriedout in soil water and vegetables samples collected at thetanning industry area using spectrophotometric methodsThe study showed that all the investigated environmentalsamples including agricultural soil and vegetables containhigh load of Cr(III) The levels of both forms of Cr (trivalentand hexavalent) in soil and water samples were above theWHO standards and showed decreasing trend with distancefrom the tannery effluent discharge point Soil samples in thevicinity of the tanning industry contained elevated load ofCr indicating the unsuitability for agricultural purposes andpotential hazards to human beings and animals if appropriateclean up strategy is implemented All the tested vegetables(cabbage onion tomato and green pepper) contained abovepermissible levels of Cr(III) in their tissue with the highestconcentration found in the edible root parts of onion Cr(VI)is not detected in the vegetable samples probably due tolack of absorption ANOVA showed that variations of thelevel of Cr among the tested vegetables were statisticallysignificant This confirmed that the chromium absorptionfrom the soil by vegetables depends on the plant specieswith highest accumulation in roots In the agricultural soilin the vicinity of the tannery the levels of Cr(III) andCr(VI) were much greater compared to control soil samplescollected at remote areas In conclusion the discharge of Crrich sludge to the environment and the unfortunate use foragricultural purposes by the community living in the vicinityof the effluent channel can lead to potential hazards of Crparticularly the hexavalent form on humans and affect thequality of the natural resources around the tanning industryTherefore appropriate reclamation methods are crucial toreducing Cr contamination
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors are very grateful to Hawassa University (HU)for providing laboratory facility for the conduct of the
experiments Dereje Homa is also grateful to the Office ofResearch and Technology Transfer of HU for partial financialsupport during the study
References
[1] J O Nriagu ldquoProduction and uses of chromiumrdquo in Chromiumin Natural and Human Environments J O Nriagu and ENieboer Eds pp 81ndash104 Wiley Interscience New York NYUSA 1988
[2] S Mishra V Singh S Srivastava et al ldquoStudies on uptake oftrivalent and hexavalent chromium by maize (Zea mays)rdquo Foodand Chemical Toxicology vol 33 no 5 pp 393ndash397 1995
[3] R Shrivastava R K Upreti P K Seth and U C ChaturvedildquoEffects of chromium on the immune systemrdquo FEMS Immunol-ogy and Medical Microbiology vol 34 no 1 pp 1ndash7 2002
[4] J Kotas and Z Stasicka ldquoChromium occurrence in the environ-ment and methods of its speciationrdquo Environmental Pollutionvol 107 no 3 pp 263ndash283 2000
[5] A D Apte S Verma V Tare and P Bose ldquoOxidation of Cr(III)in tannery sludge to Cr(VI) field observations and theoreticalassessmentrdquo Journal of HazardousMaterials vol 121 no 1ndash3 pp215ndash222 2005
[6] Z Stępniewska and A Wolinska ldquoSoil dehydrogenase activityin the presence of chromium (III) and (VI)rdquo InternationalAgrophysics vol 19 no 1 pp 79ndash83 2005
[7] R A Anderson ldquoChromium in the prevention and control ofdiabetesrdquoDiabetes ampMetabolism vol 26 no 1 pp 22ndash27 2000
[8] C Bini L Maleci and A Romanin ldquoThe chromium issue insoils of the leather tannery district in Italyrdquo Journal of Geochem-ical Exploration vol 96 no 2-3 pp 194ndash202 2008
[9] B R James J C Petura R J Vitale and G R MussolineldquoOxidation-reduction chemistry of chromium relevance to theregulation and remediation of chromate-contaminated soilsrdquoJournal of Soil Contamination vol 6 no 6 pp 569ndash580 1997
[10] P H Masscheleyn J H Pardue R D DeLaune and W HPatrick Jr ldquoChromium redox chemistry in a Lower MississippiValley bottomland hardwood wetlandrdquo Environmental Scienceand Technology vol 26 no 6 pp 1217ndash1226 1992
[11] A P Das and S Mishra ldquoHexavalent chromium (VI) environ-ment pollutant and health hazardrdquo Journal of EnvironmentalResearch and Development vol 2 no 3 pp 386ndash392 2008
[12] MMwinyihija Ecotoxicological Diagnosis in the Tanning Indus-try Springer Berlin Germany 2010
[13] M Mwinyihija A Meharg J Dawson N J C Strachan andK Killham ldquoAn ecotoxicological approach to assessing theimpact of tanning industry effluent on river healthrdquo Archives ofEnvironmental Contamination and Toxicology vol 50 no 3 pp316ndash324 2006
[14] M Mwinyihija N J C Strachan A Meharg and K KillhamldquoBiosensor based toxicity dissection of tannery and associ-ated environmental samplesrdquo Journal of the American LeatherChemists Association vol 100 no 12 pp 481ndash490 2005
[15] A H Reda ldquoStudy on the pollution levels of trace metals frommodjo tannery effluent in the surrounding river water and soilrdquoScience Journal of Analytical Chemistry vol 3 no 5 pp 56ndash602015
[16] A Cassano L Della Pietra and E Drioli ldquoIntegrated mem-brane process for the recovery of chromium salts from tanneryeffluentsrdquo Industrial amp Engineering Chemistry Research vol 46no 21 pp 6825ndash6830 2007
International Journal of Analytical Chemistry 7
[17] R Aravindhan B Madhan J R Rao B U Nair and T Ramas-ami ldquoBioaccumulation of chromium from tannery wastewateran approach for chrome recovery and reuserdquo EnvironmentalScience and Technology vol 38 no 1 pp 300ndash306 2004
[18] T Reemtsma and M Jekel ldquoDissolved organics in tannerywastewaters and their alteration by a combined anaerobic andaerobic treatmentrdquoWater Research vol 31 no 5 pp 1035ndash10461997
[19] E Bouwer N Durant L Wilson W Zhang and A Cunning-ham ldquoDegradation of xenobiotic compounds in situ capabili-ties and limitsrdquo FEMSMicrobiology Reviews vol 15 no 2-3 pp307ndash317 1994
[20] A Cassano R Molinari M Romano and E Drioli ldquoTreatmentof aqueous effluents of the leather industry by membraneprocesses a reviewrdquo Journal of Membrane Science vol 181 no 1pp 111ndash126 2001
[21] V J Sundar J R Rao and C Muralidharan ldquoCleaner chrometanningmdashemerging optionsrdquo Journal of Cleaner Production vol10 no 1 pp 69ndash74 2002
[22] Z Stepniewska K Bucior and R P Bennicelli ldquoThe effects ofMnO
2on sorption and oxidation of Cr(III) by soilsrdquoGeoderma
vol 122 no 2ndash4 pp 291ndash296 2004[23] R J Bartlett and J M Kimble ldquoBehavior of chromium in soils
oxidationrdquo Journal of Environmental Quality vol 8 pp 31ndash351976
[24] N R Jyothi NAM FarookMCho and J Shim ldquoAnalysis andspeciation of chromium in environmental matrices by variousanalytical techniquesrdquoAsian Journal of Chemistry vol 25 no 8pp 4125ndash4136 2013
[25] M Noroozifar and M Khorasani-Motlagh ldquoSpecific extractionof chromium as tetrabutylammonium-chromate and spec-trophotometric determination by diphenylcarbazide specia-tion of chromium in effluent streamsrdquo Analytical Sciences vol19 no 5 pp 705ndash708 2003
[26] J C Akan B G Kolo B S Yikala andV O Ogugbuaja ldquoDeter-minations of some heavy metals in vegetable samples from BiuLocal Government Area Borno State North Eastern NigeriardquoInternational Journal of EnvironmentalMonitoring andAnalysisvol 1 no 2 pp 40ndash46 2013
[27] R S Bai and T E Abraham ldquoBiosorption of Cr (VI) from aque-ous solution byRhizopus nigricansrdquo Bioresource Technology vol79 no 1 pp 73ndash81 2001
[28] A Wolinska Z Stępniewska and R Włosek ldquoThe influenceof old leather tannery district on chromium contamination ofsoils water and plantsrdquoNatural Science vol 05 no 02 pp 253ndash258 2013
[29] B Isikli T A Demir SM Urer A Berber T Akar andC Kaly-oncu ldquoEffects of chromium exposure from a cement factoryrdquoEnvironmental Research vol 91 no 2 pp 113ndash118 2003
[17] R Aravindhan B Madhan J R Rao B U Nair and T Ramas-ami ldquoBioaccumulation of chromium from tannery wastewateran approach for chrome recovery and reuserdquo EnvironmentalScience and Technology vol 38 no 1 pp 300ndash306 2004
[18] T Reemtsma and M Jekel ldquoDissolved organics in tannerywastewaters and their alteration by a combined anaerobic andaerobic treatmentrdquoWater Research vol 31 no 5 pp 1035ndash10461997
[19] E Bouwer N Durant L Wilson W Zhang and A Cunning-ham ldquoDegradation of xenobiotic compounds in situ capabili-ties and limitsrdquo FEMSMicrobiology Reviews vol 15 no 2-3 pp307ndash317 1994
[20] A Cassano R Molinari M Romano and E Drioli ldquoTreatmentof aqueous effluents of the leather industry by membraneprocesses a reviewrdquo Journal of Membrane Science vol 181 no 1pp 111ndash126 2001
[21] V J Sundar J R Rao and C Muralidharan ldquoCleaner chrometanningmdashemerging optionsrdquo Journal of Cleaner Production vol10 no 1 pp 69ndash74 2002
[22] Z Stepniewska K Bucior and R P Bennicelli ldquoThe effects ofMnO
2on sorption and oxidation of Cr(III) by soilsrdquoGeoderma
vol 122 no 2ndash4 pp 291ndash296 2004[23] R J Bartlett and J M Kimble ldquoBehavior of chromium in soils
oxidationrdquo Journal of Environmental Quality vol 8 pp 31ndash351976
[24] N R Jyothi NAM FarookMCho and J Shim ldquoAnalysis andspeciation of chromium in environmental matrices by variousanalytical techniquesrdquoAsian Journal of Chemistry vol 25 no 8pp 4125ndash4136 2013
[25] M Noroozifar and M Khorasani-Motlagh ldquoSpecific extractionof chromium as tetrabutylammonium-chromate and spec-trophotometric determination by diphenylcarbazide specia-tion of chromium in effluent streamsrdquo Analytical Sciences vol19 no 5 pp 705ndash708 2003
[26] J C Akan B G Kolo B S Yikala andV O Ogugbuaja ldquoDeter-minations of some heavy metals in vegetable samples from BiuLocal Government Area Borno State North Eastern NigeriardquoInternational Journal of EnvironmentalMonitoring andAnalysisvol 1 no 2 pp 40ndash46 2013
[27] R S Bai and T E Abraham ldquoBiosorption of Cr (VI) from aque-ous solution byRhizopus nigricansrdquo Bioresource Technology vol79 no 1 pp 73ndash81 2001
[28] A Wolinska Z Stępniewska and R Włosek ldquoThe influenceof old leather tannery district on chromium contamination ofsoils water and plantsrdquoNatural Science vol 05 no 02 pp 253ndash258 2013
[29] B Isikli T A Demir SM Urer A Berber T Akar andC Kaly-oncu ldquoEffects of chromium exposure from a cement factoryrdquoEnvironmental Research vol 91 no 2 pp 113ndash118 2003
![Page 1: Research Article Determination of Spatial Chromium ...downloads.hindawi.com/journals/ijac/2016/7214932.pdfin individual compartments of the biogeochemical cycle of chromium []. Redox](https://reader036.documents.pub/reader036/viewer/2022071109/5fe3d0370854460c3a119d64/html5/thumbnails/1.jpg)
![Page 2: Research Article Determination of Spatial Chromium ...downloads.hindawi.com/journals/ijac/2016/7214932.pdfin individual compartments of the biogeochemical cycle of chromium []. Redox](https://reader036.documents.pub/reader036/viewer/2022071109/5fe3d0370854460c3a119d64/html5/thumbnails/2.jpg)
![Page 3: Research Article Determination of Spatial Chromium ...downloads.hindawi.com/journals/ijac/2016/7214932.pdfin individual compartments of the biogeochemical cycle of chromium []. Redox](https://reader036.documents.pub/reader036/viewer/2022071109/5fe3d0370854460c3a119d64/html5/thumbnails/3.jpg)
![Page 4: Research Article Determination of Spatial Chromium ...downloads.hindawi.com/journals/ijac/2016/7214932.pdfin individual compartments of the biogeochemical cycle of chromium []. Redox](https://reader036.documents.pub/reader036/viewer/2022071109/5fe3d0370854460c3a119d64/html5/thumbnails/4.jpg)
![Page 5: Research Article Determination of Spatial Chromium ...downloads.hindawi.com/journals/ijac/2016/7214932.pdfin individual compartments of the biogeochemical cycle of chromium []. Redox](https://reader036.documents.pub/reader036/viewer/2022071109/5fe3d0370854460c3a119d64/html5/thumbnails/5.jpg)
![Page 6: Research Article Determination of Spatial Chromium ...downloads.hindawi.com/journals/ijac/2016/7214932.pdfin individual compartments of the biogeochemical cycle of chromium []. Redox](https://reader036.documents.pub/reader036/viewer/2022071109/5fe3d0370854460c3a119d64/html5/thumbnails/6.jpg)
![Page 7: Research Article Determination of Spatial Chromium ...downloads.hindawi.com/journals/ijac/2016/7214932.pdfin individual compartments of the biogeochemical cycle of chromium []. Redox](https://reader036.documents.pub/reader036/viewer/2022071109/5fe3d0370854460c3a119d64/html5/thumbnails/7.jpg)
![Page 8: Research Article Determination of Spatial Chromium ...downloads.hindawi.com/journals/ijac/2016/7214932.pdfin individual compartments of the biogeochemical cycle of chromium []. Redox](https://reader036.documents.pub/reader036/viewer/2022071109/5fe3d0370854460c3a119d64/html5/thumbnails/8.jpg)
