桃江河沉积物中重金属污染特征及风险评价

以赣江上游桃江河沉积物为研究对象,通过采集45个平水期表层沉积物样品,分析Cr、Cu、Zn、As、Cd、Pb和W 7种元素含量,查明沉积物中重金属污染特征,结合主成分分析和相关性分析方法探讨表层沉积物中重金属的来源,并采用地累积指数法和潜在生态风险指数法对沉积物中重金属进行了评价.结果表明,桃江河沉积物中Cu、Zn、As、Cd、Pb和W的平均含量均超过赣州市土壤环境背景值;主成分提取的两个主成分的累积贡献率为58.22%,结合Pearson相关性分析结果,表明Cu、Zn、As、Cd、Pb、W主要来源于矿业活动和城市生活排放等人为活动的影响,Cr主要来源于自然源的影响;地累积指数法评价结果表明,桃江河沉积物Cd为主要污染元素,表现为偏重污染程度,Cu呈偏中污染程度,Zn、As和W这3种元素则表现为轻度污染程度,而Cr和Pb则无污染;潜在生态指数评价结果表明,Cr、Cu、Zn、As、Pb、W均属于低生态风险等级;Cd为严重生态风险等级.潜在生态风险指数(RI)为53.60～7379.35,其中低级、中度、重度生态风险的样点分别占13.33%、17.78%、17.78%,而严重生态风险的样点占51.11%,中度生态风险及以上的点位占据85%以上,可见桃江河沉积物中重金属存在极为严重生态风险.

Heavy metal pollution characteristics and risk assessment in sediments of Taojiang River

In order to investigate the pollution characteristics of heavy metal in sediments of Taojiang River, the contents of Cr, Cu, Zn, As, Cd, Pb, and W from 45 samples of surface sediment were detected during the normal water period. The principal component analysis (PCA) and correlation analysis were used to analyze the sources of heavy metals in surface sediments, and the potential ecological risks of heavy metals were evaluated by the methods of land accumulation index and potential ecological risk index. The results show that the average concentrations of Cu, Zn, As, Cd, Pb and W in the sediments of Taojiang River exceeded the background value of soil environmental in Ganzhou City. Combining with Pearson correlation, the cumulative contribution rate of the two principal components extracted by PCA was 58.22%, and Cu, Zn, As, Cd, Pb and W were mainly derived from the mining activities and municipal emissions while Cr was mainly derived from the natural sources. The evaluation of the ground accumulation index method suggests that Cd was the main pollution factor for Taojiang River Sediment, which was characterized as heavy pollution; Cu presented moderate pollution; Zn, As and W presented mild pollution, while Cr and Pb presented non-polluting. The potential ecological index of Cr, Cu, Zn, As, Pb and W were both in low ecological risk grades, but Cd was in a serious ecological risk grade. The potential ecological risk index (RI) is ranged from 53.60 to 7379.35, and 51.11% of the sampling sites were in serious ecological risk while 85% of the sampling sites were in moderate ecological risk. It is proposed that heavy metals in the sediments of the Taojiang River have presented extremely serious ecological risks.