进入河水中的重金属离子,在一定的条件下,由于吸附、络合、絮凝、离子交换和共沉淀等作用,最终绝大部分将进入河流沉积物中。当水环境理化条件变化时,一部分重金属又可通过扩散、解吸、溶解、氧化还原和络合等作用从沉积物重返水相。

In this article the metal forms of Xiangjiang aquatic sediment are discussed.The wet and hot climate of subtropical zone as well as the carbonate environment inupper and middle reaches of Xiangjiang rebuilt in some specific regional factors for themetal forms.1. The proportion of the exchangeable trace metal concentration in the sediments is low, generally not over 2%. The proportion of the major metals in the sediments is 10-30% for Ca, 2-6% for Mn and iron the lowest.2. Beside Cu, there is a higher proportion of content of the trace metals of carbonate forms than the hydrous Fe/Mn oxides forms metal, they amount to 30-81% for the total content.The two processes mentioned above suggest that the major mechanism of self-purifica-tion in the water for trace metals is effected by the human activities pollution.3. These processes might exist simultaneously as the proportion and distribution of the trace metals for hydrous Fe/Mn oxides-form, carbonate and organic substances forms, however the major trend is different, Cd and Zn were associated by carbonate and hydrous Fe/Mn oxides and carbonate for Pb, and organic substances for Cu.4. Except the content of Fe which is more than 90%, the normal concentration of other metals is about 35-50% in residual fraction.