assessment of heavy metal contamination in soil and groundwater at leather industrial area of kasur,...

Muhammad AfzalGhulam ShabirSamina IqbalTanveer MustafaQaiser Mahmood KhanZafar Mahmood Khalid

Environmental Biotechnology Division,National Institute for Biotechnologyand Genetic Engineering (NIBGE),Faisalabad, Pakistan

Research Article

Assessment of Heavy Metal Contamination in Soiland Groundwater at Leather Industrial Area ofKasur, Pakistan

Heavy metal contamination of soil and water caused by industrialization has become amajor environmental issue in Pakistan. Therefore, it is important to determine the levelof contamination of soil and water close to industrial areas. In the current study, wehave assessed the heavy metal contamination of soil and groundwater at the leatherindustrial area of Kasur, Pakistan. Soil and groundwater samples were collected from thestudy area and analyzed for Cr, Fe, Ni, Cd, Pb, Zn, Co, and Mn by atomic absorptionspectrophotometric method. The data revealed that soil and groundwater in the studyarea are highly contaminated with all tested heavy metals. In particular, chromiumconcentrations varied from 1970 to 2980mgkg�1 and 0.82 to 2.25mg L�1 in soil andgroundwater, respectively. Correlation analysis has identified that the heavy metals inthe groundwater and soil of the study area having a common source/origin, believed tobe the leather industry of Kasur.

Keywords: Environmental monitoring; Industry; Soil; Tannery effluent

Received: December 21, 2011; revised: July 5, 2012; accepted: August 22, 2012

DOI: 10.1002/clen.201100715

1 IntroductionHeavy metals pose a threat to the environment due to their toxicity [1].The accumulation of heavy metals in soil adversely affects its physico-chemical properties leading to infertility and low yield of crops [2].Furthermore, heavymetals present in the soil can enter into food chainby passing from soil to plants and via herbivorous animals intomeat ormilk [3, 4]. In addition, the groundwater can also be contaminated dueto the continuous leaching of heavy metals. Contamination ofgroundwater by heavy metals may pose a more serious and continuinghealth risk to humans and the environment [5].Heavy metal contamination of soil due to tannery waste is a

worldwide problem [6–8]. Many chemicals, such as NaCl, H2SO4,Ca(OH)2, and Cr2(SO4)3, are extensively used during leather process-ing. As a result, wastewater from leather industry is enriched withchromium and sodium. Extensive discharges of chromium enrichedeffluent from leather industries has resulted in chromium-contami-

nated soil and groundwater at production sites, which are a severethreat to human health [9, 10].Leather processing is an important industrial activity in Pakistan,

wheremore than 600 tanneries are concentrated in threemajor cities(Kasur, Karachi, and Sialkot). Waste discharge from leather industriespollutes the air, soil, and water, causing serious health problems. The

most severely affected area is around Kasur, which has the highestnumber of tanneries in the country. These are discharging about ninemillion liter of highly contaminated wastewater daily, however,required working health principles, safety from exposure todamaging chemicals and protection at the work place are notconsidered. Currently, enhanced environmental pollution due toleather industry is adversely affecting local population healthconditions. Different diseases such as respiratory disorders, lunginfection, diarrhea/dysentery, and typhoid are frequently reported inthe local population of Kasur [9, 11].A large number of small-scale leather industries located in Pakistan

have no access to wastewater treatment facilities and thus dischargetheir waste into open fields or ditches [12, 13]. Large areas of land inthe vicinity of Kasur have become unusable for cultivation due tocontamination with heavy metals [14, 15]. Groundwater pollutionwith heavymetals is one of themajor threats to public health in theseareas [10, 16].It is very important to examine and remedy the current level of

heavy metals in the leather industry effluent contaminated soil andgroundwater at Kasur. The levels of heavy metals in soil adverselyaffect soil quality and sustainable production of crops. Themonitoring of heavy metal pollution in soil and relevant groundwa-ter is of high importance in the areas surrounding the industries [8,17]. Recently, Shakir et al. [10] characterized tannery effluent andgroundwater samples to determine the source of water pollution inKasur. Similarly, Tariq et al. [18] monitored the heavy metalcontamination levels in soil and relevant groundwater samples inPeshawar, Pakistan. These studies suggest that tannery effluent is themain contributory source of soil and groundwater pollution in theseareas.The aim of the current study was the assessment of heavy metals

(Cr, Fe, Ni, Cd, Pb, Zn, Co, and Mn) in tannery effluent affected land

Correspondence: Dr. Zafar Mahmood Khalid, EnvironmentalBiotechnology Division, National Institute for Biotechnology andGenetic Engineering (NIBGE), P. O. Box 577, Jhang Road, Faisalabad,PakistanE-mail: [email protected]

Abbreviations: AAS, atomic absorption spectrometry; BOD, biochemicaloxygen demand; COD, chemical oxygen demand; NSDWQ, NationalStandards for Drinking Water Quality; TDS, total dissolved solid; WHO,World Health Organization

1

© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com Clean – Soil, Air, Water 2013, 41 (9999), 1–7

and relevant groundwater by flame atomic absorption spectrophoto-metric method. The correlation between metals was carried outto identify possible sources of metal pollutants in the soil andgroundwater. We believe that the current study will contributeto future environmental monitoring, remediation, and planningfor tannery waste affected land and groundwater in Kasur,Pakistan.

2 Materials and methods

2.1 Site description

Kasur (31°.70N. 74°.270E) is an industrial city in central Punjabprovince, Pakistan. The population of this city is>3million while thearea is 3996 km2. Water from the Indus river and groundwater drawnfrom tube wells are used for the irrigation of the main crops –

sugarcane, cotton, wheat, and rice. For daily use and drinking mostinhabitants use groundwater extracted by tube wells. This city is well

known for its industrial activities and leather processing dominates.The other major industries produce sugar, woodwork, textile,embroidery, and glazed pottery [19, 20].

2.2 Effluent, soil, and groundwater sampling

Twelve tannery effluent samples were collected from the drainage ofrandomly selected tanneries located in Kasur. In total, 53 soil samplesand as many groundwater samples were collected in the vicinity ofthe tanneries (Fig. 1). A monolith of 30 cm� 30 cm� 30 cm was dugfor the collection of soil. Soil from each point was thoroughly mixedand about 2 kg of soil from each point was collected and placed in apolythene bag. The selection of soil sampling points was maderandomly on the basis of visual examination of the whole wastewateraffected site.Applying the standard sampling guidelines [21], the tannery

effluent and groundwater samples were collected and placed in 1-Lplastic bottles. The groundwater samples were collected either froman electric pump or hand pump installed in the area around thecontaminated site (Fig. 1). Bottles/containers containing sampleswere clearly labeled. The water samples were placed in an ice box andimmediately transported to the laboratory for analysis. To ensure thetrueness and precision, triplicate wastewater and groundwatersamples were drawn from each sampling point. Ten samples ofgroundwater and soil were collected from areas distant from thetanning units to establish background heavy metal levels (Fig. 1).

2.3 Digestion of soil and effluent for determinationof metal content

For the determination of heavy metal content in soil, acid digestionof soil was recommended as most of the heavy metals are stronglybound with themineral matrix [15, 22, 23]. It was reported that watersoluble and exchangeable fractions in soil never exceed 3% of thetotal metal concentration [24, 25]. According to the approachconsidered for the current study, soil was believed the most pollutedcompartment of the environment around tanneries in Pakistan. Inview of the loss of soil fertility and yield of crops, any investigationsuch as the present one, based on the determination of total amountof heavy metals in soil cannot be simply performed. It was, therefore,considered to investigate and analyze the acid digestion extract ofthe soil samples for the total amount of selected heavy metals in

soil [14, 22]. This was a more realistic approach and presents a truepicture of total amount of selected heavy metals in the soil.For the digestion of soil, 0.3 g air-dried soil sample was ground to

make it into fine dust, placed in a quick fit vessel and 2mL 70% nitricacid (HNO3), 6mL 35% hydrochloric acid (HCl), and 3mL 40%hydrofluoric acid (HF) were added. The mixture was refluxed on aheating plate until a transparent solution was obtained. Aftercooling, 15mL saturated boric acid was added to bind excess HF andthe volumewasmade up to 100mLwith double de-ionizedwater [22].The digestion mixture was filtered through Whatman1 no. 42 filterpaper and the filtrate was used for the determination of concentra-tion of selectedmetals in the soil. The effluent samples were digestedwith mixture of HNO3 and HCl as described earlier [22].

2.4 Analysis of soil and groundwater samples

Atomic absorption spectrometry (AAS), Varian SpectrAA.200(Varian Australia, Victoria, Australia), was used for the estimationof Cr, Fe, Ni, Cd, Pb, Zn, Co, and Mn in soil, effluent and groundwatersamples. The groundwater samples were directly analyzed withoutfiltration and addition of any stabilizer for pH adjustment.Groundwater, effluent, and soil filtrate (from digested effluent andsoil samples) were diluted, where necessary, with double de-ionizedwater.

2.5 Quality control and quality assurance

According to manufacturer’s instructions, standard optimumanalytical conditions were maintained and periodically checkedon the AAS system for each metal. Blank and sample solutions wereprepared in the same way in all determinations. An inter-laboratorycomparison of the completed data was performed at the NuclearInstitute for Agriculture and Biology (NIAB), Faisalabad. A regular

check on the accuracy of the results and the precision of theinstrument and other analytical methods was executed by usingstandard reference material (SR-96, OL). Normally, the sets of resultsmatched within �1.0 to �1.5%.

2.6 Statistical analysis

The basic statistical analysis of the data was conducted usingSTATISTICA software [26]. Some of basic statistics parameters(standard deviation, average absolute deviation, and skewness) wereused to process the analytical data in terms of selected metalsdistribution in soil and groundwater. Correlation between studiedmetals in soil and groundwater was also determined.

3 Results and discussion

3.1 Effluent characterization

Physico-chemical characterization of tannery effluent showed that itcontained higher values of biochemical oxygen demand (BOD),chemical oxygen demand (COD), total dissolved solids (TDS), chloride,sulfate, Cr, Fe, Cd, and Pb and did not comply with the permissiblelevels allowed under the National Environmental Quality Standards(NEQS), Pakistan (Tab. 1). Among heavy metals, Cr exhibited highermean concentration (128.77mgL�1) than other heavy metals.Similarly in a previous study, a highmean concentration (391mgL�1)of Cr was detected in tannery effluent samples of Kasur [9].

2 M. Afzal et al.


3.2 Heavy metal concentrations in soils

The data showing the distribution of selected heavy metals in termsof the concentration along with statistical parameters is presented inTab. 2. Chromium contents of the soil samples were alarmingly high,2443mgkg�1 (mean value). The high chromium concentration is aconsequence of the disposal of chromium-rich wastewater at this siteover a long period of time. The Kasur tanneries are well known for

chrome tanning, during which hides are treated with chromium(Cr3þ) in the presence of various salts to produce leather. Duringprocessing 50–70% of the added chromium is absorbed by collagen inthe hide and the remaining unused chromium is discarded inwastewater [9, 27]. Lower concentrations of other heavy metals (Fe,162.4; Ni, 34.2; Cd, 25.9; Pb, 18.21; Zn, 14.3; Co, 32.1; and Mn,9.42mgkg�1) were found in study area. However, these levels aresignificantly higher than those previously reported in tannery

Figure 1. Location of sampling points of tannery effluent contaminated soil (~) and relevant groundwater (D), uncontaminated background soil (*) andrelevant groundwater (�) and tanneries (&) in the study area of Kasur.

Heavy Metal Contamination in Soil and Groundwater 3


effluent contaminated soil [9, 13, 15, 19, 27]. This likely is due to ouruse of acid digestion of soil, whereas other studies used waterextraction. Acid digestion is more efficient in extracting inorganical-ly and organically bound metal from soil than water extraction.Water extraction does not fully release components that are notwater soluble, such as metal silicates, and thus underestimates theconcentrations of these [15, 21–23].Based on mean values, heavy metals in soil samples follow the

declining concentration order: Cr> Fe>Ni>Cd>Co> Pb>Zn>

Mn. Chromium and other heavy metals exhibited higher concentra-

tion than the generally expected level in soil giving rise to concernsover suitability of soil for agricultural use in the study area [6–8]. Theheavy metal distribution in the soil samples did not follow normal

distribution since the data have high degree of standard deviation,average absolute deviation, and skewness.To our knowledge, this is the first report where an extensive

analysis of tannery effluent contaminated soil of Kasur has beencarried out using acid digestion of the soil samples, which indicatesthe current levels of heavymetals in soil of the study area. Highmetalconcentrations in soil can adversely affect soil fertility and eventuallybe harmful to human beings through the food chain.

3.3 Heavy metal concentrations in groundwater

Both surface and groundwater are contaminated with heavy metalsthrough various human activities including the use of chemicals inagriculture and disposal of industrial and municipal waste intowater bodies. Many of these metals are important, in trace amounts,for human health. However, in higher amounts they cause waterpollution and can be toxic, causing serious health issues. In Pakistan,toxic metals in groundwater frequently go beyond the maximumpermissible concentrations suggested by the World Health Organi-zation (WHO) for drinking water [16]. The concentrations of heavymetals in groundwater samples collected around Kasur are shown inTab. 3. The amount of chromium (1.32mg L�1) detected is quite highin comparison to the limit (0.05mgL�1) recommended by the WHOfor drinking water and National Standards for Drinking WaterQuality (NSDWQ), Pakistan. Apparently the elevated metal levels insoil influenced the groundwater. The lower levels in groundwatermight be due to the limited flow of heavymetals through the 20–30mdeep soil bed to eventually reach the water table.A very high concentration of Pb (0.143mgL�1) was detected in

groundwater; significantly higher than the safe limit set by the WHO(0.01mgL�1) and NSDWQ (0.05mgL�1) for drinking water. Uptake ofhigh concentration of Pb over a long period of time has manydetrimental effects on human health [28]. Similarly, Fe (0.556mgL�1)

was found at higher concentration than the WHO limit (0.3mg L�1)for drinking water. The concentrations of other heavy metals are alsohigher in groundwater in the study area than the limits set by the

Table 2. Basic statistical parameters for the distribution of selected heavy metals (mg kg�1) in contaminated soil

Cr Fe Ni Cd Pb Zn Co Mn

Minimum 1970 75.2 18.3 15.0 7.18 1.98 14.25 2.15Maximum 2980 198.6 52.2 36.7 29.92 36.41 43.56 17.56Mean 2443 136.9 34.2 26.3 18.21 14.3 22.5 9.42Median 2289 162.4 33.5 25.9 16.0 6.65 32.1 8.50SD 1315 33.9 11.1 7.49 6.61 12.8 6.27 5.29AAD 1266 31.3 9.47 6.64 5.54 10.7 5.51 4.65Skewness 0.37 �0.59 0.29 0.13 0.28 0.64 �0.12 0.22

SD, standard deviation, AAD, average absolute deviation.

Table 1. Physico-chemical characteristics of tannery effluent

Parameter (unit) Value NEQS

pH 7.62 (2.4) 6–10COD (mg L�1) 2017 (308) 150BOD (mg L�1) 569 (106) 80TDS (g L�1) 15.02 (1.43) 3.50Chloride (g L�1) 12.31 (1.30) 1.00Sulfate (g L�1) 4.58 (0.46) 0.60Na (g L�1) 11.89 (2.45) NGCr (mg L�1) 128.77 (37.54) 1.0Fe (mg L�1) 5.86 (1.56). 2.0Ni (mg L�1) 0.98 (0.31) 1.0Cd (mgL�1) 0.16 (0.08) 0.1Pb (mg L�1) 1.09 (0.34) 0.5Zn (mg L�1) 1.03 (0.27) 5.0Co (mgL�1) 0.47 (0.17) NGMn (mg L�1) 0.62 (0.22) 1.5

NEQS, National Environmental Quality Standards for irrigation; NG,not given in NEQS list.Each value is a mean of 12 different wastewater samples (collectedfrommain outlet of 12 industries) and values in parentheses indicatestandard deviation among the samples.

Table 3. Basic statistical parameters for the distribution of selected heavy metals (mg L�1) in groundwater

Cr Fe Ni Cd Pb Zn Co Mn

Minimum 0.82 0.416 0.080 0.012 0.036 0.016 0.038 0.047Maximum 2.25 1.372 0.217 0.113 0.261 0.259 0.183 0.138Mean 1.32 0.556 0.108 0.040 0.143 0.135 0.150 0.073Median 1.41 0.453 0.151 0.079 0.149 0.184 0.162 0.086SD 0.51 0.474 0.024 0.023 0.065 0.072 0.031 0.026AAD 0.39 0.430 0.029 0.027 0.048 0.037 0.019 0.023Skewness �0.389 1.219 0.149 �0.082 0.042 0.251 0.037 �0.035

SD, standard deviation, AAD, average absolute deviation.

4 M. Afzal et al.


WHO for drinking water. This may be due to the leaching/seepage ofcontaminants from tannery effluent polluted soil to groundwaterover a long time period. Contamination of groundwater due to thedischarge of tannery effluents into natural water bodies or open landwas also reported in earlier studies [16, 20]. The data of groundwateranalysis also reflects non-normal distribution of heavy metals in thegroundwater, as evidenced by high values of standard deviation,average absolute deviation, and skewness.A comparison between the heavy metal concentrations found in

groundwater in present study and their permissible levels indrinking water, recommended by WHO, USA-EPA, Japan, EU, andPakistan, is shown in Tab. 4. The concentrations of Cr, Fe, Ni, Cd, andPb are higher than the recommended maximum levels. However, Znwas found at a level lower than the maximum levels recommendedbyWHO, USA-EPA and Pakistan, but higher than those recommendedby the EU. The concentration of Cr, Cd, and Pb were 13–26, 4–13, and3–14 times higher than the recommended values, respectively.A strong positive correlation was observed for Fe–Cr, Pb–Cr, Pb–Fe,

Zn–Ni, Zn–Cd, and Co–Pb pairs (Tab. 5), suggesting that the heavymetals in the soil of the study area have a common source/origin. Thisproved a mutual concentration dependence of the metals in the soilsystem under investigation. For groundwater, the metal-to-metalcorrelations matrix (Tab. 6) highlights several significant positive

correlations, indicating the same source/origin of groundwatercontamination in the study area. This might be due to the fact thatgroundwater samples were collected frompoints located in very closevicinity to the tannery effluent affected area.

Table 4. Comparison of average metal concentration (mg L�1) with some international drinking water quality standards

Present study WHO USA-EPA EU Japan Pakistan

Cr 1.320 0.05 0.1 0.05 0.05 0.05Fe 0.556 0.3 0.3 0.2 0.3 –

Ni 0.108 0.02 0.1 0.05 0.01 0.02Cd 0.040 0.003 0.005 0.005 0.01 0.01Pb 0.143 0.01 0.015 0.05 0.05 0.05Zn 0.135 3.0 5.0 0.1 – 5.0Co 0.150 – – – – –

Mn 0.073 0.5 0.05 0.05 0.05 0.5

Table 5. Metal-to-metal correlation coefficient matrix for selected heavy metals in contaminated soil

Cr Fe Ni Cd Pb Zn Mn Co

Cr 1.00Fe 0.786 1.00Ni 0.492 0.458 1.00Cd �0.573 0.128 0.585 1.00Pb 0.737 0.781 0.560 0.648 1.00Zn 0.275 �0.538 0.748 0.736 0.668 1.00Mn 0.437 0.614 0.572 �0.429 �0.538 0.256 1.00Co 0.018 �0.247 0.530 0.416 0.735 0.180 0.518 1.00

Bold values are significant at p < 0.001.

Table 6. Metal-to-metal correlation coefficient matrix for selected heavy metals in groundwater samples from tannery premises

Cr Fe Ni Cd Pb Zn Mn Co

Cr 1.00Fe 0.250 1.00Ni 0.588 0.085 1.00Cd 0.327 �0.450 0.162 1.00Pb 0.285 0.569 0.661 �0.104 1.00Zn �0.687 0.384 �0.238 �0.273 0.164 1.00Mn 0.527 �0.654 0.649 0.537 0.472 0.265 1.00Co 0.374 0.360 �0.183 0.738 0.530 0.208 0.658 1.00

Bold values are significant at p < 0.001.

Figure 2. Comparison of heavy metal levels of soil samples withbackground samples. Bars indicate the 95% confidence interval for themean values.



The levels of the selected heavy metals in the soil and groundwatersamples were compared with their corresponding background levelsand are shown in Figs. 2 and 3, respectively. This indicated that all thetested heavy metals exhibited extremely high concentrations in thetannery effluent contaminated soil and water in comparison to theirbackground levels, thus confirming the pollution of soil andgroundwater by the wastewater released from the leather industry.

4 Concluding remarksIn the study area of Kasur, where untreated leather industry effluentshave been discharged for a long time, soil and groundwater werefound to be contaminated with alarmingly high concentrations ofvarious heavy metals. As expected, the concentration of Cr wasincredibly high in comparison to other heavy metals, owing to thefact that high concentrations of Cr salts have been used for leather

tanning in Kasur tanneries. The concentrations of heavy metals (Cr,Cd, and Pb) in groundwater samples not only exceeded therecommended safe limits, rather these were 4–26 times higher thanthe drinking water quality standards. Correlation analysis estab-lished that the heavymetals in soil and groundwater have a commonorigin. The contamination in the study area, particularly with Cr,requires an effective treatment strategy for remediation of the soiland groundwater. An appropriate remediation technology for suchcontaminants is phytoremediation [29, 30]. However, further issuesneed to be addressed in the study area are speciation and availabilityof metals, physiochemical parameters of soil, water, and effluent.

Acknowledgments

We are thankful to Pakistan Science Foundation for providing thefunds for this study under PSF project No. Biotech/P-NIBGE/Env(5) toDr. Zafar M. Khalid. The authors would like to thank RobW. Briddon,Foreign Faculty Professor at National Institute for Biotechnologyand Genetic Engineering (NIBGE), Faisalabad, Pakistan, for criticalreading of the manuscript.

The authors have declared no conflict of interest.

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