Forms of heavy metal compounds in soils of the steppe zone

A parallel scheme of extractions was used for determining heavy metal compounds in uncontaminated and artificially contaminated soils of Rostov oblast. A method for calculating the contents of complex and specifically adsorbed metal compounds from the difference in their concentrations in different extracts was suggested. It was found that the portion of firmly fixed metal compounds decreases and the portion of potentially mobile (exchangeable, complex, and specifically adsorbed) metal compounds increases with an increase in the degree of contamination of chernozems and chestnut soils with lead, copper, and zinc over a one-to two-year-long observation period. This was due to the capacity of heavy metal ions to substitute for the exchangeable cations in the exchange complex of the studied soils, to form complexes with the soil organic matter, and to participate in the specific adsorption. Some differences in the behavior of different metals were found.