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The average valueof Igeo(Cd) is 0.91 and Cif(Cd) is 3.07, showingthat there is almost moderately contaminated ofCd in sediments from western Chaohu Lake ex-cept at sampling station 203# (Igeo(Cd) is −0.24,practically uncontaminated of Cd), but the valueof Eir (Cd) is high to 92, applying the classificationby Hakanson (1980), the potential ecological riskof Cd in Chaohu Lake is heavy.RI is index of potential ecological risk of totalselected potential hazardous trace elements. HereRI value is 142.72, indicating that the total poten-tial ecological risk of Cu, Ni, Cr, As, Pb, Cd, andHg in sediments of Chaohu Lake is moderate. Possible sources of pollutant inputsCluster analysis of the selected potential haz-ardous trace elements and sampling stations canbe employed to quantitatively identify specific ar-eas of contamination. As it is shown in Fig. 3,twomajor clusters (X and Y) can be seen. Cluster Xis the sampling station 203# (entrance of NanfeiRiver into Chaohu Lake), the selected hazardoustrace elements levels in this station are less thanothers except Pb. It is noteworthy that the valueof Pb is high to 112 mg/kg (Table 3), suggestingthat the site is the main source of Pb pollution intoChaohu Lake. Numerous studies have indicatedthat Pb contamination was mainly from industrialactivity and traffic sources such as automobileexhausts (Audry et al. 2004; Jin et al. 2005; Hanet al. 2006a, b;Szeferetal. 2006).
The HefeiCity, as the capital of Anhui Province, China, isthe centre of its traffic and economy, which mayled to the high Pb level on station 203# throughNanfei River. It also can be seen that cluster Yhas two sub-clusters (Y1 and Y2), Y1 includessampling stations 204#, 205#, and 206#, whichhave the same contamination inputs of Pb andCd (moderately contaminated, Table 5), and Y2includes 207# and 208# (Pb contamination is mod-erate and Cd contamination is uncontaminated tomoderately contaminated). Cd contamination onstations 204#, 205#, and 206# may be from usingof electroplating, many factories lies in the districtbetween Hefei City and Feixi town which may bethe sources of high Cd levels on these stationsthrough Shiwuli and Paihe Rivers.Table 6 is the results of Pearson’s correla-tion coefficient on selected potential hazardoustrace elements at each sampling station; it can beused to evaluate possible co-contamination fromsimilar sources among the data set. As can beseen, significant correlations occur among Cu, Ni,Cr, and Cd, indicating that these potential haz-ardous trace elements may have led to possibleco-contamination.Hg and Pbmay be the same po-tential contamination source and the correlationcoefficient is 0.812.No correlations were noted be-tween As and other selected potential hazardoustrace elements, suggesting that As might be ofdifferent origin (e.g., background of the soil, etc.)from other trace elements.
ConclusionSome potential hazardous trace element levelsof Cu, Ni, Cr, As, Pb, Cd, and Hg in sedimentsfrom western Chaohu Lake were determined inthis study, the results show that the levels var-ied widely among sampling stations and Pb andCd are higher than baseline values, respectively.Applying the evaluation of the geoaccumulationindex and potential ecological risk index, Pb andCd contamination in sediments are moderate andPb has a light potential ecological risk in ChaohuLake, but the potential ecological risk of Cd isheavy. RI value indicates that the total potentialecological risk of Cu, Ni, Cr, As, Pb, Cd, and Hg insediments of Chaohu Lake is moderate. Althoughthere is no complete inventory of the selected po-tential hazardous trace elements (Cu, Ni, Cr, As,Pb, Cd, and Hg) pollutant inputs, major potentialhazardous trace element pollutant sources intothe Chaohu Lake have been identified by clusteranalysis and some co-contamination (Cu, Ni, Crand Cd; Pb and Hg) also occur in the sediments.Acknowledgments We wish to thank Prof. MinghungWong at the Croucher Institute for Environmental Science,andDepartment of Biology,Hong Kong BaptistUniversityfor his constructive suggestions. This work was supportedby Anhui Natural Science excellent youth Foundation(08040106909).