三峡库区支流河口沉积物重金属分布特征及风险评价

Distribution Characteristics and Risk Assessment of Heavy Metals in the Sediments of the Estuary of the Tributaries in the Three Gorges Reservoir,SW China

为了解三峡库区一级支流河口沉积物污染物分布特征,在重庆忠县汝溪河和长江交界处采集了河口、中游以及左右两个断面春、夏、秋、冬这4个季节的沉积物,采用ICP-MS测定了沉积物中Cr、Zn、Mn、Ni、Cu、As、Cd和Pb等8种重金属元素的含量,运用地累积指数法、单因子重金属潜在生态风险指数法和沉积物质量基准法对研究区的重金属含量进行污染和生态风险评价.结果表明,Cr、Zn、Mn、Ni、Cu、As、Cd和Pb等8种重金属平均含量分别为:45.24、46.46、406.1、20.885、12.49、7.02、0.253和11.042 mg·kg^(-1),8种重金属含量均表现为河口处高于中游及左右两个断面,季节分布显示春季沉积物中重金属含量高于夏、秋、冬季,相关性分析表明8种重金属具有一定的同源特征,存在共同的外源输入,地累积指数法评价结果显示支流汝溪河河口属于Cd的轻度污染,单因子重金属潜在生态风险指数法显示Cd属于中等生态风险等级,沉积物质量基准表明该支流在与干流交界处Ni可能对底栖生物产生毒性效应.整体而言,该支流河口处于低生态危害等级,未受到严重的重金属污染.

To investigate the pollution status of sediments at the junction of the Three Gorges Reservoir area,sediment samples were collected over four seasons from the junction of the estuary located at a tributary of the Ruxi River and the Yangtze River.The content of eight heavy metals（HMs）,including Cr,Zn,Mn,Ni,Cu,As,Cd,and Pb,in sediments was determined by ICP-MS.The results showed the average levels of investigated HMs（in mg·kg（-1）） were Cr（45.24）,Zn（46.46）,Mn（406.14）,Ni（20.885）,Cu（12.49）,As（7.02）,Cd（0.253）,and Pb（11.042）.The distribution analysis indicated that the levels of HMs at the river mouth were higher than that of the tributaries of the middle reaches and the two sections nearby.The seasonal distribution shows that the heavy metal content in the spring sediment is higher than in summer,autumn and winter.In addition,the correlation analysis indicated that the eight HMs possessed similar homologous characteristics and had common exogenous inputs.The assessment of the Geo Accumulation Index showed slight Cd pollution in the estuary of Ruxi River,and the Potential Ecological Risk index showed that Cd presented moderate ecological risks.The toxic effect of benthonic organisms was possibly correlated to Ni contamination at the intersection of the tributary and main stream,which was supported by the evidence from the sediment quality criteria.In conclusion,the rating of ecological risk at the mouth of the Ruxi River tributary is slight.