Micro to macro-scale observation of radiocesium released from the Fukushima Daiichi Nuclear Power Plant

Tanaka, Kazuya  ; Fan, Q.*; Sakaguchi, Aya*; Takahashi, Yoshio*

Most of FDNPP-derived radiocesium in the aerosols was water-soluble. However, little amount of radiocesium in soils was leached with water. Such soluble fraction of radiocesium was strongly fixed on soil particles after deposition on the ground. This strong fixation of radiocesium can be explained by formation of inner-sphere complex in clay minerals, which was confirmed by EXAFS analysis. Many spots showing strong radioactivity were also found on the surface of soil. This indicates that the fallout radiocesium was heterogeneously distributed on the ground in a micro-scale. Most of radiocesium in river suspended particles was particulate form, and micro-scale distribution was not homogeneous, reflecting the heterogeneity of radiocesium in soil. Dissolution of radiocesium in the aerosols and subsequent strong adsorption onto soil particles are responsible for the preservation of the heterogeneous distribution of radiocesium in the environment.