Specific Features of the Accumulation and Distribution of Heavy Metals in Soils of the Floodplain and Deltaic Landscapes of the Don River

The purpose of this work was to study specific features of the accumulation and distribution of the total content and mobile forms of Heavy Metals (HM) in soils of the estuarine ecosystems of the floodplain and deltaic landscapes of the Don River. The results allowed us to detect regional specific features in the formation of HM compounds in floodplain soils of the Don River estuarine region and the changes that occur with soil pollution and to detect the influence of different factors on the transformation of metal compounds in the soils and estimate them ecologically. It was shown that the distribution of total HM content in the investigated soils is determined primarily by their content in pedogenic species of the Don river floodplain, as well as by soil factors: The organic matter content and particle-size fractions. The system of chemical element compounds forms a relationship of different compound groups, with strongly bound metal forms predominating. The soils can be ordered by their ability to strongly retain Cd, Pb, Mn, Zn, Cu, Ni: Alluvial-meadow heavy-loam > alluvial meadow light-loam > meadow alluvial-deposited > alluvial-meadow sandy and sandy-loam > alluvial-stratified sandy. This series completely corresponds to the decrease in their HM buffering capacity. Regional characteristics of HM behavior in Lower Don floodplain and delta soils include the weakly bound compounds Cd, Pb, Mn, Cu, Ni, which are represented mainly by specifically absorbed forms on carbonates and Fe-Mn (hydr) oxides.