Vertical distribution of 90 Sr and 137 Cs in soils near the Fukushima Daiichi nuclear power station

The radioactivity concentrations for 90Sr and 137Cs in soil samples collected near Fukushima Daiichi nuclear power station were investigated. The depth profile of 137Cs from the surface soil to 20 cm showed a typical decreasing tendency, that is, high radioactivity from the surface down to 5 cm due to the strong sorption of specific minerals. After deposition of 90Sr, 90Sr has migrated to deeper soil layers in the past 5 years compared to 137Cs. This tendency was supported by the results of sequential extraction to identify the predominant sorption species, and by the sorption coefficients determined by batch-wise sorption experiments.