The Ecological half-life of radiocesium in surficial bottom sediments of five ponds in Fukushima based on measurements with Plastic Scintillation Fibers

Katengeza, E. W.*; Sanada, Yukihisa   ; Yoshimura, Kazuya  ; Ochi, Kotaro   ; Iimoto, Takeshi*

Plastic scintillation fibers (PSF) have been instrumental to in-situ surface surveys of radiocesium distribution post Fukushima Daiichi Nuclear Power Plant accident. Their deployment to monitoring bottom sediments in aquatic environments provides the spatial extent of radiocesium distribution over wide areas compared to discrete points as provided traditionally by sediment sampling. This study monitored five ponds in Fukushima using PSF between 2013 and 2018 and estimated ecological half-life of radiocesium in those ponds. A forest-catchment pond had a relatively long ecological half-life, while the other ponds showed shorter half-lives. The longer half-lives draw attention to possible catchment-derived radiocesium inputs, which for the forest-pond was partly evident from spatial-temporal trends of PSF-based radiation maps.