太湖流域典型湖泊沉积物中重金属污染的分布特征

水体沉积物是重金属元素的重要载体,其含量高低能够反应水系环境质量状况.本文研究了太湖流域典型湖泊沉积物表层(0～20 cm)重金属元素的全量和有效量,并利用潜在污染生态危害指数法评价了湖泊沉积物中重金属污染的风险.根据国家海洋沉积物质量一类标准、生态危害临界值(TEL)和国家土壤质量一级标准,湖泊进水口底泥中重金属的复合污染较严重,其它区域沉积物中的重金属全量也有不同程度的超标现象,底泥中污染重金属主要为Cu、Cd、Ni、Zn.根据国家土壤质量一级标准计算的底泥重金属潜在生态风险性指数(RI)表明,进水口区域为中等污染风险,而湖泊的围网养殖区处于轻度污染风险.底泥中Cd、As、Cu、Ni之间相关性明显,Pb与其他重金属元素间的相关性不显著.这说明湖泊底泥中大多数重金属的污染来源相同,主要是工业污染及沿岸排污;而Pb可能易于沉积和被吸附,导致其在湖泊进水口迅速沉降,因此其空间分布与其他重金属不同.

Distribution Characterization of Heavy Metal Pollution in Typical Sediment from Lake Taihu Region

The sediment of water body is the main carrier of heavy metal elements,their contents reflect the environmental quality in the water system.The total and available heavy metal contents in the surface layer(0-20 cm) of sediment from a typical lake were investigated in the Lake Taihu region,and the risk of heavy metal pollution was evaluated using ecology risk harm index.According to the state standard of ocean sediment quality(first level),threshold effective level and state standard of soil quality(first level),the total contents of heavy metals in sediments from infall port were higher than those from the other parts of the lake which showed a combined pollution,the main pollutants being Cu,Cd, Ni and Zn.Ecological risk index of heavy metals in the sediment exhibited a medium pollution risk of combined heavy metals in infall port and low risk in the purse-net agricultural region.There was a remarkable correlation between the total contents of Cd,As,Cu and Ni,which suggested a same origin of pollutants.The weak correlation between Pb and other heavy metal elements might be related to its fast deposition and strong adsorption by the sediments.