滇池表层沉积物中重金属污染特征及评价

对1995~2011年滇池表层沉积物中As、Pb、Cd、Cr、Cu、Zn和Hg等7种重金属的含量及其分布特征进行了分析研究,结果表明,7种重金属元素的平均含量均明显高于云南省土壤背景值,10个沉积物采样点S1~S10均已受到不同程度的重金属污染,其中,草海的污染程度高于外海;相关性和主成份分析结果显示,滇池沉积物中As、Hg、Pb、Cd、Cu、Zn可能具有相同的污染来源。采用地质累积指数法和潜在生态风险指数法对1995~2011年滇池表层沉积物重金属污染状况进行了评价,结果表明,草海表层沉积物中重金属Igeo年均值在0.41~4.44之间,按污染等级划分,除Cr属"轻度"外,其它重金属元素均处于"中度"到"偏重度"污染;同期外海表层沉积物中重金属的Igeo年均值在0.41~2.59之间,Cd和Pb分别属于"中度"和"偏中度"污染,其它5种金属属于"轻度"污染,草海沉积物重金属的污染程度高于外海。草海7种重金属元素的RI均值为861.3,潜在生态危害达到了"严重"程度,各金属的生态危害程度顺序为Cd > Hg > As > Cu > Pb > Zn > Cr,Cd和Hg是主要的重金属生态危害因子;同期外海RI均值为236.4,达到"中等"生态危害程度,各金属的生态危害程度顺序为Cd > Hg > Pb > As > Cu > Cr > Zn,Cd是主要的重金属生态危害污染物。

Study on the Pollution Characteristics of Heavy Metals in Surface Sediments of Dianchi Lake

In this paper the total concentrations and distributions of seven metals, including As, Pb, Cd, Cr, Cu, Zn and Hg in surface sediments from 10 different sites of the Dianchi Lake during 1995~2011 were studied. The results showed that the concentrations of seven kinds of heavy metals in the sediments of the lake were higher than the background values of heavy metals in soil of Yunnan Province. The sites S1~S10 were polluted to varying degree and the pollution level of heavy metals in the Caohai section was higher than that in the Waihai section. Correlation analysis and principal component analysis indicated that the metals As, Hg, Pb, Cd, Cu and Zn may come from the same source. The pollution level of heavy metals in surface sediments of the Dianchi Lake was evaluated using the index of geo-accumulation (Igeo) and potential ecological risk index. The assessment results showed that the annual mean values of Igeo were within the range of 0.41 to 4.44 in the surface sediments of the Caohai section during 1995~2011, Cr was at the "slight" pollution level, while others were at the "moderate" or "severe" level as a whole. As for the Waihai section, the values of Igeo were within the range of 0.41 to 2.59, Cd and Pb were at the "moderate" and "severe" level, respectively, while others were at the "slight" level during the same period. The pollution degree of heavy metals was heavier in the Caohai section than that in the Waihai section. The results of potential ecological risk assessment showed that the ecological risk degree of heavy metals in the surface sediments of the Caohai section was at the "very high" level with the annual mean value of ecological risk index (RI) being 861.3 during 1995~2011. The order of ecological risk degrees for metals was Cd > Hg > As > Cu > Pb > Zn > Cr, and the metals of Cd and Hg were the dominant pollutants. For the Waihai section, the ecological risk degree reached the "moderate" level with the annual mean value of RI being 237.6, following the order of Cd > Hg > Pb > As > Cu > Cr > Zn, indicating Cd was the dominant pollutant.