The fate of Cs-137 in forest soils of Russian Federation and Ukraine contaminated due to the Chernobyl accident

摘要

The paper is based on a 25-year monitoring study of the Chernobyl-born fallout fate in forest ecosystems of Russian Federation and Ukraine severely contaminated due to the Chernobyl accident (1986). It was found that the intensity of ~(137)Cs transport in the soil profile depends primarily on type of ecosystem and soil properties, with a particular role of forest litter structure and depth. In general, retarding capacity of forest litters and ~(137)Cs half-stay period (effective half-life) in the forest litters can be expressed by the following rank order: destructive, shallow forest litters (O1 only) < fermentative, incomplete profile forest litters (O1 and O2) < humus, full profile forest litters (O1, O2, O3). The retarding capacity of individual forest litter layers for ~(137)Cs is ranked as O1 < O2 < O3. In the first five years after the fallout, ~(137)Cs release from the forest litters to mineral layers and its further migration down the soil profile was not uniform and did not exhibit a front-like character, which is likely due to a combination of local intrasoil flows and mechanical soil mixing processes. Currently, spatial pattern of ~(137)Cs within the forest litters and 0-15 cm mineral profile looks more uniform. The influence of initial fallout properties is only manifested in the topmost (0-5 cm) mineral layer.