Radionuclides in the liquid phase of the forest soils at the Chernobyl accident zone

The relative content (α) of 137Cs (1987–1991), 106Ru, 134Cs, 144Ce (1987) and the chemical speciation of radionuclides in the liquid phase of forest soils at different plots in the 30-km Chernobyl zone were studied. One year after the accident, substantial variations in the α-value between the different plots and a variation in α along the soil profile were observed due to unequal physico-chemical properties of nuclear fallout and soils. The α-value calculated for the total contaminated layer (αav) at different plots varied within relatively narrow limits. Between 77 and 97% of 137Cs in soil solution was shown to be included in organic compounds (MMw, 102–104 Da), the latter making a major contribution to the radionuclide transport from soil to plant. The α-value for 137Cs for all plots in the Chernobyl 30-km zone and the differences in α value between plots had a tendency to decrease with time. These data indicate that the process of 137Cs fixation by the soil solid phase was prevalent. Now, the ‘soil-soil solution’ system is approaching equilibrium for the radionuclide distribution between solid and liquid phases.