Migration ability of plutonium and americium in the soils of Polessie State Radiation-Ecological Reserve

Abstract

The physicochemical forms of radionuclides in soils determine the processes of their entry into the soil solutions, redistribution in the soil profile, soil–plant and soil–ground or surface waters transfer as well as spreading outside the contaminated area. The vertical distribution of plutonium and americium and their physicochemical forms in soils of Polessie State Radiation-Ecological Reserve (PSRER) were studied with the aim of establishing the potential for radionuclide migration. Samples of alluvial soddy-podzolic and peaty soils with a low (1–3%) and relatively high (~80% of dry sample mass) content of organic matter have been selected for investigation. A method employing sequential selective extraction has been used for analysis of radionuclide physicochemical forms in the soils. Activity concentrations of 238Pu, 239,240Pu and 241Am in the samples were determined via radiochemical analysis with alpha-spectrometric identification of radionuclides. The results indicate that the main proportion of plutonium and americium remains in the 0–20 cm soil layer. The inventories of mobile and biologically available forms of plutonium and americium, expressed as a percentage of the total radionuclide content in soil, lie in the ranges of 1.1–9.4 and 2.7–29% respectively. Greater proportions of mobile and biologically available forms of radionuclides appear to be associated with mineral soil as compared to organic soil. In both mineral and organic soils, the portion of mobile americium is higher than plutonium. The inventories of mobile forms of plutonium and americium increase with the depth of soils.