[3M09-15] Environmental Dynamics

[3M10] Dynamics of radiocesium in Lake Pnuma on Mt.Akagi

(1)Seasonal variation on dissolved and particulate radiocesium in lake water

*YUKIKO OKADA¹, Naoto Kumagai¹, Haruaki Matsuura¹, Shun Watanabe², Seiichi Nohara³, Yoshikazu Kikawada⁴, Masanobu Mori⁵, Yoshitaka Minai⁶, Seiya Nagao⁷ (1. Tokyo City University, 2. Gunma Prefectural Fisheries Experiment Station, 3. National Institute for Environmental Studies, 4. Sophia University, 5. Kochi University, 6. Musashi University, 7. Kanazawa University)

Keywords:Lake Onuma on Mt. Akagi, Lake water, Radiocesium(Cs-137), Dissolved and Particulate, Re-elution

The decay of radioactive cesium in the lake water of Akagi Onuma has stopped declining since 2015. Based on the data from 2012 to 2016, we analyzed the seasonal variation of radioactive cesium contained in the dissolved state and particle state in lake water at depths of 0 m, 8 m, and 15 m. As a result, it was confirmed that more radioactive cesium was present in the suspended state than in the dissolved state at the surface layer 0 m. In addition, in the lake water at a depth of 15 m, an increase in dissolved cesium was observed around October before the full circulation period. This suggested the possibility of re-elution from the sediment.