中文摘要：

湘江是我国重金属污染最严重的河流之一.本次工作利用Tessier连续提取法及原子吸收法（AAS）,对湘江下游河床沉积物中Cu、Zn、Pb、Cd等重金属的赋存形态进行分析.结果表明,重金属Zn、Pb主要赋存于铁-锰氧化物矿物相中、其次是以碳酸盐矿物的形式存在.二者加起来所占比例平均在70%以上.重金属Cd除赋存在碳酸盐矿物和铁-锰氧化物矿物相中之外,较高活性的可交换态比例也大.重金属Cu除赋存在碳酸盐矿物、铁-锰氧化物矿物相中之外,还以较高的比例赋存于有机质中.环境条件如发生变化,赋存于有机质中的Cu可释放转入水体.运用风险评价编码法（RAC）发现Cd处于极高风险级,并且4种重金属元素中Cd的毒性最大,由此可见,湘江下游Cd污染问题需引起高度重视.

英文摘要：

The Xiangjiang River watershed is one of the rivers that are most seriously contaminated by heavy metals in China. This study performed a detailed analysis on the forms of metals Cu, Zn, Pb and Cd in bed sediments from the lowermost River using the Tessier five-step extraction methods and atomic absorption spectrophotometry （AAS） technique. The results show that Zn and Pb were mainly in the forms of Fe-Mn oxides and carbonates, more than 70% of the total concentrations in the sediments. Cd existed mostly in the exchangeable form in addition to the carbonate and Fe-Mn oxide minerals froms in sediments. Cu was mainly in organic matter-bound form, as well as in the forms of carbonate and Fe-Mn oxide mineral phases. All these four heavy metals are toxic, and their exchangeable and carbonate-hosted forms are not stable, especially for Cd in the sediments. If the condition of the water system is changed, they may become mobile and enter the water that can cause very serious environmental problems for human-beings. Thus, the present study suggests that a great attention should be paid to the pollution caused by these four heavy metals in the sediments.