Seasonality of Cs-137 concentration of sediments eroded from a slope in Fukushima

Wakiyama, Yoshifumi*; Manome, Ryo*; Onda, Yuichi*; Yoshimura, Kazuya  

This study presents a three years' Cs-137 wash-off observation and morphological surveys on a soil erosion in area affected by the accident of Fukushima nuclear power plant to describe detailed processes of Cs-137 wash-off. Cs-137 concentration varied enormously and it appeared to decrease gradually from spring to autumn and increased again after winter. Based on the photos and scan data of soil surface, the expansions of a rill from spring to summer and elevations of soil surface from winter to spring were found. Our analysis suggests that freezing and thawing cycles resulted in high Cs-137 concentration of sediments during winter, whereas expansion of rill makes decrease in Cs-137 concentration in warm seasons.