Distribution of caesium in soil and its uptake by plants

Abstract

The speciation of radiocaesium forms in the soil horizons that determine its further behaviour in the environment was considered. The present-day equilibrium in radiocaesium migration processes demonstrates that 70-90 % of the radionuclide was retained in the fixed form in upper 5-20 cm soil layer regardless of the type of soil and nature of contamination. In the forest ecosystems the litter layer continues to be a major accumulator of radiocaesium and contains 40-80 % of 137Cs being the main biochemical barrier to its vertical and horizontal migration. It was shown that radiocaesium can be easily absorbed by plant roots from soil solution and translocated to the above-ground plant biomass. The main environmental factors responsible for the variability in radiocaesium uptake by higher plants from soil are described. The uptake of radiocaesuim by plant species of herbal-shrubby storey in forest ecosystems was considered. It was shown that various plant species reveal the differences in 137Cs uptake via significantly different rates of the radionuclide accumulation during their vegetation period.