湘江衡阳段地表水体重金属污染及生态风险评价

The Pollution Characteristics and Ecological Risk Assessments for the Heavy Metals of Surface Water-bodies in Hengyang Section of Xiangjiang River

为研究湘江衡阳段地表水及表层沉积物中重金属分布特征及生态风险,文章采用电感耦合等离子体质谱法分析测定了湘江衡阳段21个采样点地表水及表层沉积物中6种重金属的含量,并运用单因子污染指数法、内梅罗综合污染指数法、地累积指数法和潜在生态风险指数法,评价了重金属污染现状及潜在生态风险。结果表明,湘江衡阳段地表水中6种重金属含量均未超标,单因子污染指数均<1,水质良好;内梅罗综合污染指数整体变化范围0.404~4.991,水质未受到严重污染。研究区表层沉积物中6种重金属元素均有不同程度超过背景值。地累积指数评价结果表明,湘江衡阳段已受到Cd和As偏中度污染和Cr、Cu、Pb和Zn的轻度污染;潜在生态风险指数评价该江段存在中等潜在生态风险,其中Cd为高潜在生态风险,对综合潜在生态风险贡献率为77.66%,单一重金属潜在生态风险指数大小依次为Cd>As>Cu>Pb>Cr>Zn。

In order to investigate the distribution characteristic and ecological risk of heavy metals in surface water and sediment of Hengyang section of Xiangjiang River,the content of six heavy metals in surface water and surface sediments of 21 sampling points in Hengyang section of Xiangjiang River was determined by inductively coupled plasma mass spectrometry(ICP-MS).The single factor pollution index,Nemerow comprehensive pollution index,geo-accumulation index and potential ecological risk index were used to evaluate the pollution degree and potential ecological risk of heavy metals.The research results indicated that the content of six heavy metals in the surface water is below the standard.The single factor pollution index of six heavy metals was<1 and the water quality was good,the Nemerow comprehensive pollution index was 0.404~4.991,and the water quality was not seriously polluted.The content of six heavy metals in the surface sediments of the study area all exceeded the background value to different degrees.The results by geo-accumulation index indicate that the Hengyang section of Xiangjiang River were moderately polluted by Cd and As and mildly polluted by Cr,Cu,Pb and Zn.The heavy metals in Hengyang section of Xiangjiang River had moderate comprehensive potential ecological risk.Cd contributed 77.66%rate of comprehensive potential ecological risk and was at high potential ecology risk.The potential ecological risk index of single heavy metal decreased in the following order:Cd>As>Cu>Pb>Cr>Zn.