长江沉积物环境地球化学特征及生态风险评价

Environmental Geochemical Characteristics of the Sediments in the Yangtze River and Its Ecological Risk Assessment

为了进行长江流域沉积物生态风险评价,对长江流域干流以及主要支流的沉积物统一进行采样分析。首先对其元素的组成特征及重金属元素的富集特征进行分析。常量元素含量在流域空间上的变化主要受其携带矿物含量变化的影响;Cu、Pb、Cd、As、Hg 5种微量元素富集程度较大,存在异常。同时采用潜在生态风险指数法对长江沉积物Cr、Mn、Co、Ni、Cu、Zn、Pb、Cd、As、Hg 10种元素进行了评价研究。结果表明,潜在生态风险指数较大的地区分布在湖南湘江、安徽铜陵等地区,中等的地区分布在四川、重庆及江西等地区,这些潜在污染指数与矿产的开采冶炼以及工业的布局有一定的关系,很大程度上是由人为因素造成的。从元素的潜在污染程度看,长江流域Cd、As、Hg污染程度较重,Cu、Zn、Pb次之,而Cr、Mn、Co、Ni基本没有污染。本研究为探讨长江流域沉积地球化学过程和环境保护提供了科学依据。

In order to study and discuss the ecological risk of the sediments in the Yangtze River,sediment samples were collected at 62 sites along the Yangtze River from the main stream and main tributaries.First the characteristics of element composition and heavy metal accumulation were analyzed and the results showed that the differences of macro-element content in space were caused by the content change of mineral elements carried by the river.We also found the enrichment degrees of the five elements（Cu,Pb,Cd,As,Hg） were relatively high and abnormal.Ecological risk assessment for Cr,Mn,Co,Ni,Cu,Zn,Pb,Cd,As and Hg was also given by means of potential ecological risk index.The evaluation results showed,according to the potential pollution level by heavy metals along the Yangtze River basin,that it is most serious in Xiang River region of Hunan Pro-vince and Tongling region of Anhui Province.The second most seriously contaminated zones consist of Sichuan,Chongqing and Jiangxi.Pollutions have certain relations with mining explorations and distribution of industry,largely caused by human factors.According to the pollution levels of different elements,Cd,As,and Hg turned out to be the worst,followed by Cu,Zn,Pb,while Cr,Mn,Co and Ni were basically not contaminated in the Yangtze River basin.Our research on sediments in the Yangtze River provides a scientific basis and theoretical reference for further studying about sediments＇ geochemistry process and environmental protection.