三峡库区蓄水运用期表层沉积物重金属污染及其潜在生态风险评价

为全面了解蓄水运用期三峡库区表层沉积物中重金属含量及其潜在生态危害程度,在三峡库区干流及支流共采集了24个沉积物样品,测定了Cu、Pb、Zn、Cd、Ni、Cr、As和Hg的含量,并采用地积累指数法和潜在生态风险指数法对沉积物中的重金属污染进行了评价.结果表明,三峡库区重金属元素Cu、Pb、Zn、Cd、Ni、Cr、As和Hg的平均含量分别为:76.03、59.40、137.63、0.75、46.81、86.31、18.07和0.109 mg.kg-1,均高于长江沉积物背景值.地积累指数法评价结果显示:重金属元素污染程度顺序为:Cd>Pb>Cu>As>Zn>Ni>Hg>Cr.潜在生态风险指数法评价结果表明,各重金属污染对三峡库区构成的潜在生态危害由强至弱依次为:Cd>Hg>Cu>As>Pb>Cr>Zn,其中Cd的贡献因子最大.总体上讲,三峡库区蓄水运用期处于轻微生态危害等级,并未受到明显的重金属污染.

Heavy Metals Pollution and Its Potential Ecological Risk of the Sediments in Three Gorges Reservoir During Its Impounding Period

In order to investigate the heavy metals concentrations and their potential ecological risks of sediments in Three Gorges Reservoir during its impounding period,24 sediment samples were collected from both the mainstream and tributaries for analyzing Cu,Pb,Zn,Cd,Ni,Cr,As and Hg.The index of geoaccumulation and the potential ecological risk index were then employed to evaluate the pollution degree of heavy metals in the sediments.The results indicate that the average contents of heavy metals in Three Gorges Reservoir: Cr is 86.31 mg·kg-1,Ni is 46.81 mg·kg-1,Cu is 76.03 mg·kg-1,Zn is 137.63 mg·kg-1,Cd is 0.75 mg·kg-1,Pb is 59.40 mg·kg-1,As is 18.07 mg·kg-1,Hg is 0.109 mg·kg-1,respectively.Average concentrations of heavy metals in sediments of Three Gorges Reservoir are relatively higher than those in sediment background of Yangtze River.The assessment by geoaccumulation index indicates that the pollution degree of heavy metals is: Cd>Pb>Cu>As>Zn>Ni>Hg>Cr.The assessment by potential ecological risk index show that the potential ecological risk intensity caused by heavy metals is: Cd>Hg>Cu>As>Pb>Cr>Zn,and Cd is the predominant element among them.In general,it is not significantly polluted during the impounding of Three Gorges Reservoir.