Chemical states of fallout radioactive Cs in the soils deposited at Fukushima Daiichi Nuclear Power Plant accident

The chemical states of radioactive Cs (caused by Fukushima Daiichi Nuclear Power Plant accident) in the contaminated soils have been characterized by the desorption experiments using appropriate reagent solutions and size fractionation of the contaminated soils. More than 65% of radioactive Cs remained in the residual fraction of the soil samples after treatment of 1 mole L-1 NH4Cl solution and 1 mole L-1 CH3COOH solution. Approximately 70% of radioactive Cs in the residual fraction were associated with the size fractions larger than the elutriated one, even though mica-like minerals were present in the elutriated one. These results strongly suggest that radioactive Cs was irreversibly associated with soil components other than mica-like minerals in the contaminated soil.