[M-AG44] 福島原発事故により放出された放射性核種の環境動態

[MAG44-08] 河川水中の懸濁態Cs-137と溶存Cs-137の間の分配係数の化学的意味について

*廣瀬 勝己¹、恩田 裕一¹ (1.筑波大学アイソトープ環境動態研究センター)

キーワード：放射性セシウム、河川水、分配係数

After the Fukushima Daiichi Nuclear Power Plant accident, terrestrial environment has been seriously contaminated by radiocesium. As a result, higher levels of radiocesium concentrations in river water have continued in Fukushima area, although they exhibit gradual decline trends. Partition coefficient between suspended and dissolved ¹³⁷Cs, Kd, has been introduced as a tool to have better understanding of dynamic behavior of ¹³⁷Cs in river system. However, the partition coefficient showed larger spatiotemporal variability. It is important to elucidate factors controlling the partition coefficient of ¹³⁷Cs in river system. We, here, introduce a chemical model to explain variability of the partition coefficient of ¹³⁷Cs in river system. The chemical model reveals that the partition coefficient of ¹³⁷Cs in river is inversely related to electro-conductivity and the suspended sediment (SS) concentration in river, respectively. Especially, to explain the effect of SS for Kd, presence of colloidal ¹³⁷Cs, passing through filter, is significant as dominant dissolved species of ¹³⁷Cs in river water. The result suggests that chemical speciation study of ¹³⁷Cs dissolved in river water is important to know chemical and ecological roles of dissolved ¹³⁷Cs in river water.