洞庭湖表层底泥重金属污染及其生态风险评价

Ecological Risk Assessment of Heavy Metals in Superficial Sediment of Dongting Lake

对洞庭湖表层底泥样进行了Cd、Pb、Cu、Zn、As、Hg和Cr等7种元素含量分析,并采用潜在生态风险指数法和土壤环境质量标准首次对各河流入湖口和各子湖区(段)表层底泥重金属的污染状况进行了评价。结果显示,洞庭湖各子湖区(段)表层底泥中以Cd污染最为严重,所有样点Cd含量均超过国家土壤质量三级标准限值;其次为Pb、Cu和Zn,各子湖区该三种金属含量均属于国家土壤质量二级标准;再次为As和Hg,东洞庭湖和西洞庭湖等湖区As、Hg均属于国家土壤质量二级标准;而Cr对洞庭湖表层底泥的污染最轻。主要河流入湖口中,湘江和资江入湖口表层底泥的Cd、Pb、Zn和As污染最为严重,沅江入湖口表层底泥的Hg污染最为严重,资江和汨罗江表层底泥的Cu和Cr污染最为严重。潜在生态风险指数法评价结果表明:西洞庭湖表层底泥重金属污染对生态潜在危害极高,南洞庭湖、东洞庭湖、城陵矶和大通湖的重金属污染潜在生态风险指数分级为高。根据潜在生态风险综合指数(RI)值大小,洞庭湖各子湖区(段)重金属复合污染程度由重到轻次序为:西洞庭湖>大通湖>城陵矶>东洞庭湖>南洞庭湖。

Heavy metal concentrations of Hg, As, Cd, Cr, Cu, Pb and Zn in the superficial sediment of Dongting Lake were quantitatively analyzed in this paper, and referencing the national environmental quality- standard for soils, the pollution degree of heavy- metals in the sediment of stream inlet section and sub - lake areas were analyzed by the potential ecological risk index （RI） method . The results show that Cd pollution was most serious in the superficial sediment of Dongting Lake, the average concentration of Cd in all sampling sites exceed the standards of Class III of environmental quality- standard for soils in China. The second serious pollutants were Pb, Cu and Zn, which belong to Class II of environmental quality- standard for soils in China, followed by As and Hg, the average concentrations of As and Hg in east and west Dongting lake areas belong to Class II of the standard, and Cr pollution was slightest in the sediment of Dongting Lake. Among the main inlet rivers, Cd, Pb, Zn, and As pollution were most serious in Xiangjiang and Zijiang river inlet sediment, Hg pollution was most serious in Yuanjiang river inlet superficial sediment, Cu and Cr pollution were most serious in Zijiang and Miluo river inlet superficial sediment. Potential ecological risk index evaluation results indicate that the potential ecological risk of West Dongting Lake by heavy metals pollution is extremely high, and that of South Dongting Lake, East Dongting Lake, Chenglingji and Datong Lake are in high - grade. According to RI values, the degree of heavy metal integrative pollution of superficial sediments in Lake Dongting is arranged in the following order, West Dongting Lake 〉 Datong Lake 〉 Chenglingji 〉 East Dongting Lake 〉 South Dongting Lake.