Comparison of the vertical distributions of Fukushima nuclear accident radiocesium in soil before and after the first rainy season, with physicochemical and mineralogical interpretations

Matsunaga, Takeshi; Koarashi, Jun   ; Atarashi-Andoh, Mariko  ; Nagao, Seiya*; Sato, Tsutomu*; Nagai, Haruyasu  

The effect of intensive rainfall in the on distribution of Fukushima accident-derived Cs in soil was examined in Fukushima-city in post-rainy season and were compared with those in pre-rainy season. It is concluded that rainfall during the rainy season had a limited effect on Cs distribution in soil, indicating its overall immobility. Chemical extraction of Cs from selected soil samples indicated that Cs in soil was hardly water-soluble and extractable with 1M ammonium acetate. This supports the overall immobility of Cs in our soils. No direct relationship was obtained between the mineral composition and the Cs retention in upper soil layer. In contrast, positive correlations were found between the Cs extractability and soil properties such as pH, organic matter content, and finer-sized particle contents in the soils. These results suggest that the mineralogical effect may be masked by non-specific adsorption offered by physicochemical properties of the soils.