Influence of temperature decrease and soil drought on the geochemical fractionation of ~(60)Co and ~(137)Cs in fluvisol and cambisol soils

摘要

Consideration of the impact of substantial changes in soil temperature or moisture regime on the geochemical forms of radionuclides is important for more accurate assessment of the environmental risk posed by radionuclide migration and potential biological availability, especially in the first months after their release into the environment. This paper presents the results from a study of the influence of cooling, freezing and soil drought on the migration and potential bioavailability of ~(60)Co and ~(137)Cs in two soils (a fluvisol and a cambisol, according to the World Reference Base for Soil Resources/FAO) from Bulgaria. The changes in the geochemical fractionation of ~(60)Co, the exchangeable ~(137)Cs and water-soluble forms of both radionuclides were examined under different storage conditions up to 5 months after their introduction into the soils in solution form. Freezing or soil drought resulted in a significant increase of the water-soluble forms of ~(60)Co in the fluvisol soil, defining higher mobility and potential bioavailability. No influence of the storing conditions on the water-solubility of ~(60)Co in the cambisol soil was established. The cooling, freezing and soil drought caused an increase of the exchangeable ~(137)Cs in both soils.