| Bioavailability and mobility of heavy metals accumulated in soil are not only related to total contents of heavy metals, but also to their forms. Therefore the main methods for prevention and remediation of heavy metal contaminated soils are reduction of total contents and bioavailability of heavy metals.. The main results in this study are as follows:1. Enrichment of heavy metals in particulate organic matter in a lead/zinc mining tailings contaminated soilThis study investigated the distribution of heavy metals (Lead, Zine, Copper and Cadmium, i.e.) among different size particulate organic matter (POM) fractions in polluted soils around a lead zinc mine in Shaoxing, Zhejing Province. According to soil POM's size and density, physical fractionations were carried out to separate POM. It was suggested that all of the four heavy metals (Pb,Zn,Cu,Cd) were significantly enriched in the POM fractions. Enrichment of heavy metals in POMs increased with a decrease in POM size. Most heavy metals were enriched in 0.05-0.25mm POM. In the finest POM fraction (0.05-0.25mm), Zn and Pb concentration is three to four times as those in POM (>1mm). Among four heavy metals, Cu was enriched to the greatest extent. The enrichment coefficient of Cu reached 14.67, about 6 times as that of Pb in the studied soil..2. Form distribution of heavy metals in soil profiles in a lead/zinc mining tailings contaminated soilAccording to Tessier method, heavy metals in different profiles were divided into several forms. With the increase of the depth of soil profiles, the total heavy metals decreased. It was suggested that the residual form was the main form of heavy metals in soil profiles and was positively correlated with concentrations of heavy metals insoil profiles. Residual Zn in the uncontaminated soil was about half of total Zn. Residual Zn in the most heavily contaminated soil reached 62.0-75.7%.The Carbonate-bound heavy metals decreased with reduction of soil pH.
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