洞庭湖沉积物中重金属污染特征与评价

Character and assessment of heavy metals in the sediments from Lake Dongting

于2003-2004年在洞庭湖湖区采集沉积物样品700个,测定了沉积物中As、Cd、Cr、Cu、Hg、Ni、Pb、Zn的含量,并用地积累指数方法和主成分分析法对沉积物中的重金属污染状况进行了评价和分析.结果显示,洞庭湖各子湖区沉积物中Cd、Cr、Cu、Pb、Zn的平均含量都属于国家土壤二级标准,As、Hg、Ni属于国家土壤一级至二级土壤标准;在南洞庭湖与东洞庭湖入湖河流的三角洲的前缘是沉积物重金属积累最高的地点,而在西洞庭湖入湖河流三角洲的后缘沉积物重金属含量比前缘高.采用综合地积累指数法对洞庭湖各子湖区沉积物进行评价,结果表明:南洞庭湖(重污染)>东洞庭湖(偏重污染)>西洞庭湖(中度污染)>大通湖(中度污染)>城陵矶(轻度污染).采用主成分分析法对洞庭湖各子湖区沉积物进行分析,结果表明:南洞庭湖与东洞庭湖第一主成分贡献率分别为55.22%、56.86%,主要支配As、Cd、Hg、Pb、Zn的载荷,而第二主成分贡献率分别为30.04%、33.11%,主要支配Cu、Cr、Ni的载荷;西洞庭湖、大通湖和城陵矶因沉积物重金属来源不同,主成分分析结果相差较大.

700 sediment samples were collected from Lake Dongting during 2003-2004, and concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, Zn in the sediments were measuremed. The results showed that the average concentrations ofCd, Cr, Cu, Pb, Zn did not exceed the standards of Class II of environmental quality standard for soils in China; the average concentrations of As, Hg and Ni were between the standards of Class I and the standards of Class II of the standard. The heavy metals in east Lake Dongting and south Lake Dongting were mostly accumulated in the front of the delta where rivers ran into the lake, however the heavy metals in west Lake Dongting were mostly accumulated in the rear part of the delta. Results with integrative index of geoaccumulation showed that the decreasing order of the degree of heavy metal pollution in Lake Dongting was as follows： south Lake Dongting 〉 east Lake Dongting 〉 west Lake Dongting 〉 Lake Datong 〉 Changlingji. Principal component analysis （PCA） was applied to study the heavy metals in the sediments from Lake Dongting. Results showed that the first principal component （PCI） in south Lake Dongting accounts for 55.22% of total data variance, and the second principal （PC2） accounts for 30.04%. As, Cd, Hg, Pb, and Zn have greater loadings in the PCI, and Cu, Cr and Ni have greater loadings in PC2, in south Lake Dongting and east Lake Dongting. For the west Lake Dongting, Lake Datong and Chenglingji, due to the fact that they have different sources of heavy metals, the principal component analyses have shown different results.