Comparative Study on 2 Methods of Separation of Various Species of Heavy Metal Elements in Soil ——Using the Data of Cu and Mn Obtained by FAAS as Criterion

Virtues and defects of the direct method (sequential extraction procedure proposed by Tessier and etc.) and the indirect method for speciation of heavy metals in soil were studied comparatively using the data of Cu and Mn in soil found by FAAS as criterion. In both the 2 methods, species of heavy metals in exchangeable state, combined carbonate state, combined oxides of iron and manganese state and combined organic state were first separated by applying the sequential extraction produre with 4 different extraction solvents. It was found that due to high concentration of salt in the extraction solvents which led to matrix interference in FAAS analysis and due to remarkable blank values found in the reagents used, significant errors were found in the direct method. The indirect method was preferred to avoid the interferences mentioned above.