The distribution characteristics and evaluation of ecological risk of heavy metals in the surface sediment of Taihu Lake
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Abstract:
Research on the contents of heavy metals, such as Cd, Pb, Cu, Cr and their distribution characteristics in the surface sediments of 29 sampling sites in Taihu Lake, are conducted. Meanwhile, the distribution characters of the specific chemical forms of these heavy metals are analyzed with the method of BCR. Results show that the content of Cr has the highest values, while Cd has the lowest values, and contents of the four metals are different in different parts of Taihu Lake. The content of Cu and Cr in Meiliang Bay, Zhushan Bay and Gonghu Bay is high；while, the content of Cu in southern coast of the lake is the lowest；and the middle lake has the lowest content of Cr. Among the specific chemical forms of these heavy metals, the proportion of the extractable form of Cd is the highest, and Pb, Cu and Cr mainly exist in the residual form. This suggests Cd has the highest mobility among the four kinds of heavy metals. Furthermore, the potential ecological risk of these four kinds of heavy metals is evaluated by using the ratio of minor phase and progenetic phase(RSP). It shows that Pb, Cu and Cr are at pollution-free level in all parts of the lake. However, Cd is at moderate-polluted level in the sampling sites of river inlets of Zhushang Bay and western coastal lake, and at light-polluted level in parts of sites of Eastern Taihu Lake, Xuhu Bay, and Gonghu Bay. It indicates that Cd is the more serious pollutant in the whole lake of Taihu. And the descending order of the potential ecological risks of these heavy metals is Cd>Pb>Cu>Cr. Meanwhile, in terms of the different parts of the lake, southern coastal, middle lake and Gonghu Bay are at non-polluted level, and the others are at light-polluted level. However, the pollution level of Gonghu Bay is close to light-polluted level.
