Soil Heavy Metal Contamination and Risk Assessment Around the Fenhe Reservoir, China
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Soil Heavy Metal Contamination and Risk Assessment Aroundthe Fenhe Reservoir, ChinaHong Zhang Guanglei Liu Wei Shi Jinchang LiReceived: 21 November 2013 / Accepted: 21 May 2014 Springer Science+Business Media New York 2014Abstract Heavy metal contamination in the soil around awater source is a particularly serious issue, because theseheavy metals can be transferred into the water source andcan pose significant human health risks through the con-tamination of drinking water or farmland irrigation water.In this paper, we collected surface soil samples from thearea surrounding the Fenhe Reservoir. The concentrationsof As, Cd, Cr, Cu, Hg, Ni, and Zn were determined and thepotential ecological risks posed by the heavy metals werequantitatively evaluated. The primary inputs for As, Ni,and Zn were natural sources, whereas the other elementswere derived from mainly anthropogenic sources. Hg dis-plays more serious environmental impacts than the otherheavy metals. The upper reaches of the reservoir, located inthe northwest, display a higher potential ecological risk.Keywords Heavy metals Sources identification Ecological risk Spatial distributionThe contamination of urban and peri-urban soils by heavymetals has received increasing public attention and cor-relative surveys have been carried out in several munici-palities (Birke and Rauch 2000; Rizo et al. 2013).However, the contamination pattern in soils of water sourceareas, especially in developing countries, remains inade-quate, which is a particular problem because these heavymetals can be transferred from the soil into reservoirs,rivers, or underground water, which will pose a severethreat to human health if it contaminates drinking water orfarmland irrigation water (Zahra et al. 2014; Suresh et al.2012). Therefore, fully understanding (quantifying andmapping) the spatial characteristics of soil contaminationby heavy metals in water source areas will facilitateaccurate risk assessment and planning of mitigation and/orremediation (Lin 2002).The Fenhe River, which is the second-largest tributaryof the Yellow River, possesses a length of 716 km and awatershed area of 39, 000 km2, and flows through thecentral and southern areas of the Shanxi Province of China.The Fenhe Reservoir, located in the upper reaches of theFenhe River, is the largest reservoir and drinking watersource area in Shanxi Province. We conducted the presentstudy to survey soil heavy metal contamination around theFenhe Reservoir. The aims of this study are: (1) to deter-mine and compare the concentrations of heavy metals insoils surrounding the Fenhe Reservoir with those of otherareas; (2) to identify their possible sources; and (3) toassess the potential ecological risks posed by these heavymetals.Materials and MethodsAbout 50 soil samples were collected around the FenheReservoir during April 2011. The detailed sampling loca-tions are shown in Fig. 1. Each sample was a composite ofsoil subsamples taken from the top 20 cm of 10 sites. Ateach site, we obtained about 1 kg of soil using a stainless-steel spade, and stored the samples in sealed polyethylenebags. Site descriptions were registered at the time ofsampling to record the sample locations, elevations, landuse types and major environmental features.H. Zhang (&)College of Environmental Science and Resources, ShanxiUniversity, Taiyuan 030006, Chinae-mail: email@example.comH. Zhang G. Liu W. Shi J. LiInstitute of Loess Plateau, Shanxi University, Taiyuan 030006,China123Bull Environ Contam ToxicolDOI 10.1007/s00128-014-1304-8Each sample was air-dried, ground with agate mortar andsieved to 200 mesh size and homogenized with cut sizes of0.075 mm. All procedures of handling were carried outwithout contacting any metals in order to avoid potentialcross-contamination of the samples. For analysis of Cr, Cu,Zn, Ni, and Pb, samples were pressed into pellets having adiameter of 3.1 cm under the pressure of 20 ton per cm2 andthen exposed to X-rays from a rhodium tube. The mea-surements were carried out using a Rigaku ZSX 100ewavelength dispersive X-ray fluorescence spectrometer. Foranalysis of As and Hg, the soil samples were digested withconcentrated HNO3 and HCL in a microwave-acceleratedreaction system and were quantified using Atomic Fluores-cence Spectrometer. For analysis of Cd, the soil sampleswere digested with concentrated HF and H2SO4 in amicrowave-accelerated reaction system and were quantifiedusing graphite atomic absorption spectrometer.Appropriate quality assurance procedures and precau-tions were carried out to ensure reliability of the results.Double distilled deionized water was used throughout thestudy. Reagents blank determinations were used to correctthe instrument readings. Standard reference soil (GSS-11\10\14) obtained from the China National Center forStandard Materials were used for validation of the analyt-ical procedure. Table 1 shows the analytical limits ofdetection and relative standard deviation (RSD) of eachheavy metal.Many factors can influence the concentrations of heavymetals in soil and their impacts upon ecosystems. Principalcomponents analysis (PCA) has been widely used toidentify the sources of soil pollutants (Mico et al. 2006;Gurhan and Semiha 2008). In the present study, we per-formed PCA using SPSS 13.0 for Windows.The potential ecological risks posed by the heavy metalswere quantitatively evaluated using Hakansons method(1980; Muge et al. 2013). These risk indices are calculatedas follows:Eir Tir CisCin1RI Xni1Eir 2where Eir is the potential ecological risk index of an indi-vidual metal i; Tir is the toxic-response index for heavymetals i, Hakanson (1980) suggested that appropriate Tirvalues for As, Cd, Cr, Cu, Hg, Ni, and Zn were 10, 30, 2, 5,40, 5, and 1, respectively. Cis is the measured concentrationof metal i at sampling sites s, Cin is the background value(BGV) of heavy metal i in the research area. RI is thepotential ecological risk index that results from the com-bination of multiple metals. The higher the E and RI are,the higher the risk is. Table 2 summarizes the potentialecological risk indices and corresponding risk grades.Results and DiscussionTable 3 summarizes the results of heavy metal concentra-tions in soils in the research area. The median was selectedas a representative of central tendency because the datadoes not require a normal distribution. We have providedFig. 1 Location of the studyarea and sampling sitesTable 1 The limits of detection and RSD of each heavy metalHeavy metal Limits of detection (mg kg-1) RSD (%)As 0.42 3.09Cd 0.029 6.64Cr 5 3.25Cu 1 5.54Hg 0.003 1.80Ni 2 3.73Zn 2 1.62Bull Environ Contam Toxicol123the Grade I and Grade II values in the Chinese Environ-mental Quality Standard for Soil as well as the soil BGVfor the Taiyuan Basin in Table 3. In the Chinese standard,Grade I levels represent the average natural backgroundlevels for uncontaminated soil of China, and Grade IIlevels represent the levels at which a pollutant is hazardousto agricultural production and human health.The concentrations of heavy metals in the research areaare lower than the Grade I and Grade II criteria, suggestingthat the soils of the research area has not been contami-nated related to the average natural background levels ofheavy metals in soils of China and were currently nothazardous to agricultural production and human health.However, Cr and Hg displayed relatively higher meanconcentrations than the corresponding background levelsfor soil in the Taiyuan Basin, suggesting that both elementswere more likely to be affected by anthropogenic sources.The coefficients of variation (CV) values were all relativelysmall for the seven elements, suggesting that theseelements were derived predominantly from natural sourcesor from dispersed anthropogenic sources.In this study, the concentrations of heavy metals of soilsin this research area were in the approximate order ofmagnitude when compared with those in other areas ofChina (Table 4). The concentrations of heavy metals indifferent research areas were various, which may beattributed to the different natural background and humanactivities.PCA was applied here to identify the sources of soilpollutants. The results of the efficiency of the method areindicated in Table 5. It can be seen that the first 4 factorsexplain over 86.61 % of the total variation. The first PC,which explained 37.15 % of the total variance, wasstrongly and positively related to As, Ni, and Zn. As, Ni,and Zn showed significant correlations and their meanconcentrations were comparable to the correspondingbackground levels in the research area. Therefore, it seemsreasonable to infer that PC1 is related to natural sources atTable 2 Indices and grades ofpotential ecological riskIndices Low Moderate High Very high Extremely highE E \ 40 40 B E \ 80 80 B E \ 160 160 B E \ 320 E C 320RI RI \ 150 150 B RI \ 300 300 B RI \ 600 RI C 600Table 3 Descriptive statistics of heavy metal concentrations in soils in the research areaHeavy metal Median Minimum Maximum SD CV Grade I Grade II BGVAs 10.7 4.1 12.8 1.3 12.50 15 25 10.2Cd 0.114 0.050 0.155 0.025 23.36 0.2 0.8 0.1Cr 75.4 52.2 87.7 5.7 7.57 90 250 65.1Cu 21.8 14.4 32.9 3.3 14.93 35 100 21.5Hg 0.041 0.022 0.095 0.017 36.96 0.15 1.5 0.03Ni 26.6 22.3 33.4 2.5 9.11 40 100 28.2Zn 60.6 41.0 84.4 6.5 10.64 100 300 61.6All concentrations were given in unit of mg kg-1 of dry weightSD standard deviation, CV coefficient of variation (%), Grade I the average BGV of soil heavy metals of China (SEPA 2008), Grade II the valueof soil heavy metals in China for protecting agricultural production and human health (SEPA 2008), BGV background value of soil heavy metalsin the Taiyuan Basin (Wang et al. 2008)Table 4 Heavy metalsconcentrations (mg kg-1) indifferent soil samples in China Means data not availableSample site Number As Cd Cr Cu Hg Ni Zn ReferencesAround the FenheReservoir, Taiyuan50 10.7 0.114 75.4 21.8 0.041 26.6 60.6 This studyRoadside, Beijing 80 8.1 0.215 61.9 29.7 26.7 92.1 Chen et al.(2010)Suburban areas, Tianjin 86 9.5 0.49 101 67 0.97 100.6 Shi et al.(2010)Industrial district,Shenyang93 17.56 0.54 65.1 71.1 0.33 182.0 Li et al.(2013)Bull Environ Contam Toxicol123the regional scale. The second PC, which explained24.59 % of the total variance, demonstrated high positivefactor loadings for Cu and Hg. Previous studies showedthat Cu and Hg are typically anthropogenically influenced(McMartin et al. 2002). PC3 and PC4 accounted for13.48 % and 11.39 % of the total variance, and showedstrong positive loadings for Cr and Cd, respectively, whichcan be identified as another tracer of anthropogenic pol-lution sources.The potential ecological risk factors E for each metaland the RI for all seven heavy metals combined of theresearch area were summarized in Table 6. The resultsshow that the highest concentrations of Hg present a con-siderably higher potential ecological risk than any otherelements, and that Cd poses a moderate potential ecologi-cal risk. In contrast, As, Cr, Cu, Ni, and Zn pose a lowpotential ecological risk. The differences result from thefact that the toxic-response factors for Cd and Hg arehigher than those for other elements. On the other hand, Hgconcentrations in soils in the study area are elevated, butnot dramatically; for example, the maximum concentrationof Hg is only 3.2 times the BGV for the study area (and theratios are even\1 when compared with the Grade I criteriain Table 3). Based on the potential ecological risk factorsfor all metals combined (RI), the minimum, mean, andmaximum potential ecological risk grades are low, low,and moderate, respectively, which can be mainly attributedto the fact that the study area is located far from anymetropolitan areas and does not support any heavy indus-trial operations.In order to indicate the spatial distribution of potentialecological risk of heavy metals in the research area, wemapped the distribution of RI by using of GIS-based Kri-ging interpolation methods. The results were shown inFig. 2 and suggested that the northwestern part of the studyarea exhibits a moderate potential ecological risk, whereasother areas except local spots present mainly a relativelylow potential ecological risk. This should be a cause forconcern for the local government because the soils in thearea, located in the upper reaches of the Fenhe Reservoir,can easily contaminate the reservoir through particulatedeposition by wind and precipitation.The soils surrounding the Fenhe Reservoir are mostlylightly polluted by heavy metals, since none of the sevenanalyzed elements in any of our samples exceeded theGrade I criteria that represent the natural background levelsfor uncontaminated soil in China or the Grade II criteriathat were established to protect agricultural production andhuman health. The concentrations of heavy metals in theresearch area were in the approximate order of magnitudecomparing with those in other areas of China. The con-centrations of As, Ni, and Zn were mainly affected bynatural sources and the concentrations of Cd, Cr, Cu, andFig. 2 Spatial distribution of RI in soils in the research areaTable 5 PCA results with first 4 factorsHeavymetalsPC 1(37.15 %)PC 2(24.59 %)PC 3(13.48 %)PC 4(11.39 %)As 0.760 -0.379 0.264 0.216Cd 0.108 -0.059 0.041 0.989Cr 0.216 -0.029 0.931 0.045Cu 0.512 0.635 -0.389 0.001Hg -0.060 0.937 0.047 -0.067Ni 0.913 0.014 0.027 0.105Zn 0.815 0.260 0.182 -0.025Table 6 Potential ecologicalrisk indices (E) for each metaland the risk index (RI) for soilheavy metals in the researchareaHeavymetalsToxic-response index(Tir)E RIMin. Mean Max. Min. Mean Max.As 10 4.07 10.18 12.57 82.69low116.35low180.51moderateCd 30 14.91 31.99 46.50Cr 2 1.50 2.17 2.52Cu 5 3.34 5.13 7.65Hg 40 29.33 61.09 126.67Ni 5 3.96 4.79 5.92Zn 1 0.67 0.99 1.37Bull Environ Contam Toxicol123Hg were mainly controlled by various anthropogenicsources. The potential ecological risks posed by Hg wereconsiderably higher than those for any other elements. Thenorthwestern parts of the study area are at a moderatepotential ecological risk, based on the multi-metal riskindex (RI). To conclude, the results of our study highlightthe influence of human activities, particularly agriculturalactivities, on heavy metal levels in soils surrounding theFenhe Reservoir and the potential ecological risks posed bythese pollutants. This may thereby provide a basis fordeveloping soil quality policies for the region.Acknowledgments This work was financially supported by theNational Natural Science Foundation of China under Grant 41271513.ReferencesBirke M, Rauch U (2000) Urban geochemistry: investigations in theBerlin metropolitan area. Environ Geochem Health 22(3):233248Chen X, Xia XH, Zhao Y, Zhang P (2010) Heavy metal concentra-tions in roadside soils and correlation with urban traffic inBeijing, China. 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Chemosphere 65(5):863872Muge A, Filiz K, Muhammet D, Tolga GL (2013) Heavy metalconcentrations in surficial and core sediments from Izmir bay: anassessment of contamination and comparison against sedimentquality benchmarks. Bull Environ Contam Toxicol 91(1):6975Rizo OD, Morell DF, Lopez JOA et al (2013) Spatial distribution andcontamination assessment of heavy metals in urban topsoils fromLas Tunas city, Cuba. Bull Environ Contam Toxicol 91(1):2935SEPA (State Environmental Protection Administration of China)(2008) Environmental quality standard for soils, GB15618-2008Shi RG, Lv JG, Cai YM et al (2010) Levels, spatial distribution andpossible sources of heavy metals contamination of suburban soilsin Tianjin, China. Bull Environ Contam Toxicol 85(3):287290Suresh G, Sutharsan P, Ramasamy V, Venkatachalapathy R (2012)Assessment of spatial distribution and potential ecological riskof the heavy metals in relation to granulometric contents ofVeeranam lake sediments, India. Ecotoxicol Environ Saf84:117124Wang XJ, Lai JQ, Kong H et al (2008) Analysis of the geochemicaldistribution characteristics of heavy metal elements in soil inTaiyuan basin and Taiyuan city (in Chinese). Earth Environ36(1):7280Zahra A, Hashmi MZ, Malik RN, Ahmed Z (2014) Enrichment andgeo-accumulation of heavy metals and risk assessment ofsediments of the Kurang Nallahfeeding tributary of the RawalLake reservoir, Pakistan. Sci Total Environ 470471:925933Bull Environ Contam Toxicol123Soil Heavy Metal Contamination and Risk Assessment Around the Fenhe Reservoir, ChinaAbstractMaterials and MethodsResults and DiscussionAcknowledgmentsReferences
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