Biogenic and Abiogenic Migration of 90Sr and 137Cs of Chernobyl Origin in Terrestrial and Aqueous Ecosystems

Fifteen years of observing radionuclide speciation in different landscapes within the Chernobyl Exclusion Zone (ChEZ) have allowed us to estimate a number of kinetic-rate constants for radionuclide speciation in soils. In this paper, we investigate the rate changes in radionuclide migration within the soil-vegetation system, the contamination level of freshwater ecosystems, and the parameters of speciation, which are the kinetic criteria for self-cleaning of the radiation-contaminated regions. Cesium-137 immobilization (fixation) in the soil-adsorbing complex is considered to be the mechanism for 137Cs removal from trophic chains. The geochemical transfer factor from soil to vegetation allows us to estimate the radioecological balance. We have found that the rate of environmental self-cleaning is an order of magnitude faster than 137Cs and 90Sr radioactive decay rates.