上海东风西沙水库表层沉积物重金属含量及生态风险评价

位于崇明岛西侧的东风西沙水库是上海第二大饮用水水源地,为了解其表层沉积物中重金属的污染状况,于2019年对该水库10个断面的表层沉积物样本作了粒径分析,对9种重金属元素含量及其潜在生态风险作了测定和评估。分析显示,该水库表层沉积物中砂粒、粉砂和黏土平均含量分别为46.29%、42.63%和11.08%,整体属于细砂质。Hg、Cd、As、Ni、Pb、Cu、Cr、Zn和Mn 9种元素的平均含量分别为0.02、0.68、11.30、13.07、18.51、27.73、62.18、82.29和488.66 mg/kg。仅有Cd和As的平均含量为上海市土壤背景值的5.23倍和1.24倍,其余7种则低于该背景值。地积累指数法评价显示,Cd为主要污染元素,总体处于偏中度污染水平,其他8种元素则为清洁水平。潜在生态风险指数法评价显示Cd为主要生态风险贡献因子,风险等级为强生态危害水平,其他8种元素则为轻微生态危害水平,水库总体处于中等生态风险水平。

Content characteristics and ecological risk assessment of heavy metals in surface sediment of Dongfeng Xisha Reservoir, Shanghai, China

Dongfeng Xisha Reservoir, located in the west side of Chongming Island, is the second largest source of drinking water in Shanghai. In order to understand the pollution of heavy metals in surface sediments, the particle size of surface sediment samples collected from 10 sections of the reservoir in 2019 was analyzed, the contents and potential ecological risk of nine heave metal elements were analyzed and evaluated. The results showed that the average content of sand, silt and clay were 46.29%,42.63% and 11.08%, and on the whole, the surface sediment of the reservoir is fine sand sediment. The average contents of Hg, Cd, As, Ni, Pb, Cu, Cr, Zn, Mn were 0.02,0.68,11.30,13.07,18.51,27.73,62.18,82.29,488.66 mg/kg. Only the average contents of Cd and As were 5.23 and 1.24 times the Shanghai soil background value, and the others were below this background value. Pearson correlation coefficient showed that the sources of heavy metals in surface sediments were similar and the particle sizes played an important role in the distribution of Hg, As, Cu, Zn, Cr and Pb; industrial wastewater, agricultural wastewater and domestic sewage were the probable sources by the method of principal component analysis (PCA). The result of Geo-accumulation index showed that Cd was the main pollution element, which was generally at a moderate pollution level, while the other 8 elements were at a clean pollution level. Potential ecological risk assessment showed Cd was the main ecological risk contribution factor, which is at a strong ecological hazard level, and the other 8 elements were at a slight ecological hazard level. The reservoir is generally at a moderate ecological risk level.