Study on Form Distribution and Correlation of Heavy Metals in the Sediment of Urban Water

With the Tessier Five-step Continuous Extracting Method, the thesis studied the form distribution of heavy metals in the sediment samples collected from Mochou Lake, Xuanwu Lake and Qinhuai River in Nanjing, analyzed the correlation between leaching contents of heavy metals and various forms and between content of organic matter and leachability of heavy metals and between organic matter and organic fraction, and primarily investigated the mechanism of the combination of organic matter and heavy metal through the infrared spectrum. The results indicate that, in the sediment, Pb, Cu, Zn, Ni and Cr are mainly existing in the forms of organic and residual fractions, which take up over 70% of all; the exchangeable and carbonate fractions in Zn and Cd occupy comparatively larger proportion, about 20% for Zn and 30% for Cd; the leaching content of Pb, Cu, Zn, Ni and Cr are all shown highly correlated with their exchangeable fraction, therefore the risk of heavy metal pollution in the sediment could be controlled by decreasing the content of exchangeable fraction of heavy metals; the study also shows that, there is obvious positive correlation between organic matter and organic fraction, therefore, increasing the content of organic matter in the sediment could accelerate the transformation of heavy metals to organic fraction. The combination of organic matter and heavy metals is mainly due to formation of stable complex by some functional groups and heavy metals.