ИСТИНА

137Cs and 90Sr are one of the main fission products that can enter the environment, soil and water as a result of nuclear accidents or leaks from radioactive waste storage facilities. This isotops have relatively short half-life (30.1 and 28.9 years), can accumulate in soil and be transported through the food chain. However, long-lived 135Cs (a component of spent nuclear fuel) may also become important with time. The mobility of radionuclides in soils depends on various parameters, such as mineral composition, chemical properties of soils, acid-base conditions presence of organic matter and other. The method of sequential removal of organic matter and non-silicate iron compounds from the soil before the sorption experiment was applied to understand the interaction mechanisms with individual soil components. The investigation results of sorption regularities and the strength of Cs(I) and Sr(II) fixation by various soil horizons are presented in the work. Experiments were carried out on 4 horizons of peaty-podzolic-gleyic and 4 horizons of floodplain soddy-gleyic soils from the Central Forest State Natural Biosphere Reserve (Nelidovsky district of the Tver region). The sorption experiments were performed by 2 scenarios –with 100 g/L soil suspensions in 0.01 M NaClO4 at room temperature, and 1.7g/L of soil in distilled water at a constant temperature of 8°C to simulate incubation conditions. To evaluate the strength of Cs(I) and Sr(II) binding the sequential extraction were carried out according to the Tessier procedure. It was shown, that peaty-podzolic-gleyic soils effectively sorb Cs(I). The experiments with a Cs(I) concentration of 10-6 M and trace concentrations showed similar sorption regularities for the samples from different soil horizons. Based on results of sequential extraction we can suggest that Cs(I) sorbed on the functional groups of organic matter is fixed less strongly than Cs(I) attached to the specific sites of illites and vermiculites. The strength of Cs(I) fixation is affected by the type of sorption site and the time of interaction. Contrary to Cs(I), Sr(II) sorbes unquantitatively on studied soils, and sorption reduces with organic matter removal. The sorption of Sr(II) varies strongly with pH. The results of sequential extraction revealed that Sr(II) binds tightly with soils, but the strength of the binding increases when the organic matter is removed. This research was supported by MSU Program of Development, project № 23-SCH07-04.