湖南省主要水系底泥重金属污染特征及其生态风险评价

为全面了解湖南省主要水系底泥中重金属含量及其潜在生态风险，在湖南省内的湘、资、沅、澧以及洞庭湖5个主要水系共采集了75个位点的底泥样品，分析了重金属元素含量和来源分布特征，并采用地累积指数法、内梅罗指数法和潜在生态风险指数法对其污染程度和潜在生态风险进行评价。结果表明，As、Cd、Cr、Cu、Mn、Pb和Zn的平均含量分别为32.87、7.59、78.09、70.69、1182.60、85.64 mg/kg和482.44 mg/kg。湘江和洞庭湖的污染相对严重，底泥中重金属含量明显高于资江、沅江和澧水；相关性分析表明多种重金属具有相同污染来源；地累积指数评价结果显示，湖南省主要水系底泥中Cd为重污染水平，Zn为中度污染，Cu、Mn和Pb均为轻度污染，而As和Cr污染程度为清洁；内梅罗指数法评价结果表明，除Cr为轻度污染外，湖南省主要水系底泥中其他6种重金属污染均为重污染级别；潜在生态风险评价结果显示，湖南省总体潜在生态风险属于中等级别，各水系潜在生态风险大小顺序为洞庭湖>资江>湘江>澧水>沅江，重金属Cd的潜在生态风险级别为很强，其他重金属元素都属于轻微级别。

Pollution characteristics and ecological risk assessment of heavy metals in sediments of main water systems in Hunan Province

In order to fully understand the content of heavy metals in the sediments of the main water systems in Hunan Province and their potential ecological risks, 75 sediment samples were collected from five major water systems and analyzed. The correlation of the contents of various heavy metals in the sediments of the main water systems in Hunan Province was analyzed. Based on the sampling test results, the along the river distribution of heavy metals in the sediments of four rivers in Hunan Province was also analyzed. Through the content analysis of the Cd and Mn along the river, it was found that the change of Mn content along the river was similar to that of Cd, and the peak value of heavy metal content had an important relationship with the drainage enterprises, heavy pollution industrial parks and estuary siltation. The pollution degree and potential ecological risk were evaluated by the geo-accumulation index method, Nemerow index method and potential ecological risk index method. The results showed that the average contents of As, Cd, Cr, Cu, Mn, Pb and Zn were 32.87, 7.59, 78.09, 70.69, 1182.60, 85.64 and 482.44 mg/kg, respectively. The pollution of Xiangjiang River and Dongting Lake was relatively serious, and the content of heavy metals in the sediments was significantly higher than that of Zijiang, Yuanjiang and Lishui River. Correlation analysis showed that multiple heavy metals had the same pollution source. The evaluation results of the geoaccumulation index showed that the pollution level of Cd wss severe, level of Zn was moderate, level of Cu, Mn, and Pb were all mild, while the pollution levels of As and Cr were clean in the sediments of the main water systems in Hunan Province. The Nemero index evaluation results showed that, except for the light pollution of Cr, the other six heavy metal pollution in the sediments of the main water systems in Hunan Province were the severe levels. The potential ecological risk assessment results showed that the overall potential ecological risk of Hunan Province belonged to the medium level. The order of the potential ecological risk of each water system was Dongting Lake > Zijiang River > Xiangjiang River > Lishui River > Yuanjiang River. The potential ecological risk level of Cd was very severe and the level of other heavy metal elements were mild.