环巢湖流域表层沉积物重金属赋存特征及潜在生态风险评价

Occurrence characteristic and potential risk assessment of heavy metals in surface sediments of Circum-Chaohu Basin

以环巢湖流域表层沉积物为对象,对8种重金属(Cd、Cr、Cu、Zn、Ni、Pb、As和Hg)总量及形态进行分析并运用潜在风险指数法对重金属的生态风险进行了评价.结果表明,环巢湖流域表层沉积物中重金属元素Cd、Cr、Ni、Cu、Zn、Pb、As和Hg的总量总体呈现为南淝河-十五里河水系含量高,其次是裕溪河及支流,其他5条水系的重金属含量相对较低.BCR形态分析表明,重金属元素Hg、Cr、Ni和Cu主要以残渣态存在(分别占总量的77.56%、64.83%、56.52%和48.93%),Cd的可提取态含量比例最高(89.22%),其次为Zn、Pb和As(70.35%,69.50%和63.70%).潜在生态风险危害指数(RI)表明,Cu、Zn、Pb、Cr、Ni和As均为低污染等级,Cd为较重污染等级,Hg为重污染等级,7个水系的重金属潜在生态风险指数排序为:南淝河-十五里河>裕溪河>柘皋河>杭埠河-丰乐河>派河>白石山河>兆河,重潜在风险和严重潜在风险的区域主要分布在南淝河-十五里河水系以及裕溪河水系,因此,今后对巢湖流域进行重金属整治时可着重考虑针对这两条水系的Cd和Hg元素的重点治理.

Surface sediment samples were taken from Chaohu Basin, total and fractions of eight heavy metals （Cd, Cr, Cu, Zn, Ni and Pb） were studied. The pollution of heavy metals were evaluated by the potential ecological risk index （RI）. Heavy metal distribution of surface sediment indicated the highest degree of contamination in Nanfei-Shiwuli River, followed by Yuxi river and its tributaries, finally the other 5 rivers. Fractions of heavy metals analysis showed that Hg, Cr, Ni and Cu existed mainly in residual fractions （77.56%, 64.83%, 56.52% and 48.93%）, and extractable fraction was dominant for Cd （89.22%）, followed by Zn, Pb and As （70.35%, 69.50% and 63.70%）. Potential ecological risk assessment showed that Cu, Zn, Pb, Cr, Ni and As had low pollution level, Cd had a higher pollution level and Hg had heavily pollution level, the potential ecological risk of heavy metals was in the descending order of Nanfei-Shiwuli river〉Yuxi river〉Zhegao river〉Hangbu-Fengle river〉Pal river〉Baishishan river〉Zhao river. The risk assessment code showed that Cd had very high risk level, Zn had high risk level, Cu and Ti were between low risk and medium risk level, Pb was between no risk and low risk level, Cr posed no risk. Therefore, emergent management measures must be taken to control pollution of Cd and Hg in Nanfei River and Yuxi River.