Leaching Characteristics and risk evaluation of heavy metals from recyle materials and contaminated soil with sequential extraction test

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Leaching amounts of heavy metals in the leachates are closely related to the forms of heavy metals in the wastes. Several kinds of sequential leaching tests have been used as a tool to clarify the extractable forms of trace elements like heavy metals in solid samples. These procedures for the determination of the extractable trace metals in soil and sediments were harmonized as the BCR method by the Standards, Measurements and Testing Programs in Europe in 1992. But we cannot apply the BCR method to alkali samples because this method is only for neutral samples.In this study, we improved the condition of the BCR sequential extraction method in order to apply to alkali samples. Moreover, this modified BCR sequential extraction method was applied to the recycle materials and contaminated soils in order to evaluate the extractable forms of recycle materials and contaminated soils.As the results, we could obtain the adequate amounts of heavy metals for each fraction from alkali samples by the modified BCR method, which had the distilled water extraction and neutralization procedures as pre-treatment steps. Judging from the results of the reagents, the oxides of Pb, Cd, Cu and Zn were mainly extracted in the acid soluble fraction, and sulfides were mainly extracted in the oxidisable fraction. From these results, the feature of each fraction obtained by the modified BCR method was able to be clarified. However, the extractable forms of Cr could not be evaluated. Furthermore, the modified BCR method was applied to the recycle materials and contaminated soils, and the heavy metals contained in each sample could be classified from a viewpoint of elution characteristics. These results showed that elution risk of heavy metal was low.