长江口沉积物重金属赋存形态及风险特征

Speciation and Risk Characteristics of Heavy Metals in the Sediments of the Yangtze Estuary

基于长江口沉积物8种重金属(As、Cd、Cr、Cu、Hg、Ni、Pb、Zn)总量与形态在丰、平、枯水期以及14个典型点位的分布特征,通过平衡分配法建立了长江口沉积物质量基准(SQGs),并以此评价长江口沉积物重金属生态风险,揭示重金属生态风险与其形态特征间的相关关系.结果表明,除Cd之外,长江口沉积物重金属以残渣态为主导形态,尤其是As、Cr、Hg,其残渣态含量均为90%以上.长江口As、Cd、Cr、Cu、Hg、Ni、Pb、Zn的沉积物质量基准分别为43.29、0.672、79.65、19.08、0.569、339.09、30.87、411.36μg·g^(-1).Cu的生态风险程度最高,对水生生物具有较大的毒性影响,应当引起重视.河口上游受到长江径流影响大,在丰水期风险较高,在平水期和枯水期则风险偏低;而下游受上海等城市排污影响较大,风险较高(尤其在平水期和枯水期).8种重金属的生态风险与赋存形态之间表现出3种不同的相关关系.

Based on the investigation on the distribution of total contents and speciation of 8 heavy metals（ As,Cd,Cr,Cu,Hg,Ni,Pb,Zn） in the surface sediments at 14 typical sites of the Yangtze Estuary during three hydrological seasons（ wet,normal,and dry seasons）,this study applied equilibrium partitioning approach to build the sediment quality guidelines（ SQGs） of the Yangtze Estuary,and assessed ecological risks of the heavy metals. The relationship between ecological risk and speciation of heavy metals was also revealed. The results showed that,except for Cd,the residual fraction was the main speciation of heavy metals,especially for As,Cr and Hg,their residual fraction proportions were all over 90%. The sediment quality guidelines of the Yangtze Estuary for As,Cd,Cr,Cu,Hg,Ni,Pb,Zn were 43. 29,0. 672,79. 65,19. 08,0. 569,339. 09,30. 87,411. 36 μg·g^（-1）,respectively. Cu had the highest ecological risk to aquatic organisms. The upstream of Yangtze Estuary was mainly affected by Yangtze River runoff,where the risks were relatively high in wet season and relatively low in normal and dry seasons. However,the downstream of the estuary was mainly affected by municipal sewage of cities like Shanghai,where the risks were relatively high,especially in normal and dry seasons. There were three different relationships between the ecological risks and speciation of the eight heavy metals.