Chemical partitioning of Zn in soil: application of two sequential extraction procedures

The data on the accumulation and distribution of heavy metal (HM) compounds in soils is necessary to assess and predict the ecological situation. The Zn fractional distribution in artificially contaminated soil by the most popular methods of sequential extraction (the well known Miller and Tessier methods) was studied. The sample studied was soil (Haplic Chernozem) artificially contaminated by Zn acetate (2000 mg kg(-1)), a priority pollutant in southern Russia. In order to estimate the role of different soil components in the Zn partitioning, the carbonates, Fe-Mn sesquioxides, and organic matter, were removed from the soil samples, prior to application of each sequential extraction scheme. Results showed a metal absence in the fraction bound to the removed soil component. The Miller method allows better tracing of the HM fractions loosely bound to the soil because of the use of weaker extractants with high complexing capacity, which hampers the reprecipitation of metals from the extract. The Tessier method is more suitable for the separation of the total anthropogenic component from contaminated soils. This is related to the higher extraction capacity of reagents. The differences in the fractional distribution of metal according to each method are most manifested in the contaminated soil.