Ecological and Toxicological Assessment of the Soil-Plant Cover of Unmown Streletskaya Steppe in the V.V. Alekhin Central Chernozem Reserve

The ecological and toxicological assessment of the soil and plant cover of a key site in the Streletskaya Steppe in the V.V. Alekhin Central Chernozem Reserve is presented. The content of heavy metals (HMs) and radionuclides in typical chernozem is determined. The clarkes of concentration of HMs (C_c); geoaccumulation lithogeochemical indices (I_geo) for As, Cd, Co, Cs, Cu, K, Pb, Sr, Zn, ²³²Th, and ²³⁸U; and pollution indices (PI) for individual HMs in chernozem have been calculated. It is shown that the pedogeochemical background is higher in comparison with the lithosphere clarkes only for Cd and As. In may be concluded that soils are not polluted with the studied HMs, namely, As, Cd, Cu, Pb, and Zn. The content of radionuclides (⁴⁰K, ¹³⁷Cs, ²³²Th, and ²³⁸U), HMs, and potassium in various types of natural steppe vegetation has been determined. Based on the plant accumulation coefficients of HMs and radionuclides, the biophilicity of radionuclides and HMs was estimated. The transfer factors (TFs) of ¹³⁷Cs and ⁴⁰K from soil to plants have been calculated, and a comparative analysis of the bioavailability of cesium and potassium during root uptake is performed. The vertical distribution of ¹³⁷Cs and ⁴⁰K radionuclides in the root-inhabited soil layer from 0- to 20-cm-thick is studied. It is shown that ⁴⁰K is evenly distributed in the root-inhabited layer. The vertical distribution of ¹³⁷Cs in the soil profile is characterized by the shift of the maximum from a depth of 0–5 to that of 5–10-cm. Based on the data obtained, the migration coefficient of ¹³⁷Cs is calculated, taking into account the convective and diffusion components of the radionuclide translocation in typical chernozem.