Spatial Distribution Characteristics and Ecological Risk Assessment of Heavy Metals in Sediments of Zhanghe Reservoir
In order to explore the pollution level and potential ecological risk of surface sediments of heavy metals in Zhanghe Reservoir,Hubei Province,20 sediment samples were collected from the surface sediments of Zhanghe Reservoir and its outlet.The content and distribution characteristics of eight heavy metals,including As,Hg,Cr,Ni,Cd,Cu,Pb,and Zn,were analyzed.The potential ecological risk index method and the geo-cumulative index method were used to analyze and evaluate the pollution of surface sediments in Zhanghe Reservoir.The results showed that the average enrichment coefficient of surface sediments of heavy metals in Zhanghe Reservoir was Cd(3.37)＞Pb(1.29)＞Ni(1.21)＞Zn(1.11)＞As(0.99)＞Cu(0.98)＞Cr(0.95)＞Hg(0.88).The elements that exceeded the background value were Cd,Pb,Ni,and Zn.The accumulation of Cd content exceeded the standard value seriously.The high value area was located along the line from Guanyinsi Dam to Mahe Town and from Jigongjian Dam to Zhanghe Town.The potential ecological risk index of surface sediments of heavy metals in Zhanghe Reservoir was 91.85-233.88,and 45％of the sampling points were classified as slight and 55％as medium.The results of the geo-cumulative index evaluation showed that the main cause of sediment pollution in Zhanghe Reservoir was excessive Cd.The average geo-cumulative index of Cd was 1.09,and 11 sampling points were classified as mild and medium pollution,and 9 sampling points were classified as mild pollution.It was concluded that the main cause of Cd pollution in sediments of the northern reservoir area of Zhanghe Reservoir was coal mining and combustion,while the Cd pollution in sediments of the southern reservoir area was more closely related to the combustion of petroleum products.
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