[1I01-07] Environmental Dynamics 1

[1I06] Investigation on distribution of radioactive substances in Fukushima

(6) Dynamics of dissolved Cs-137 in streams and rivers in the Yamakiya district, Fukushima Prefecture, Japan

*Taichi Kawano¹, Yuichi Onda¹, Hiroaki Kato¹, Fumiaki Makino¹ (1. Univ. of Tsukuba)

Keywords:Fukushima Daiichi Nuclear Power Plant accident, Cs-137, decontamination, Kd

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident occurred on March 11, 2011, and a large amount of Cs-137 was released into the environment. It is important to clarify the behavior of radioactive Cs-137 in forested headwaters because most of the Cs-137 is deposited in forested areas and transported into the environment through river systems. In this study, we aimed to clarify the dynamics of Cs-137 in river water based on long-term monitoring conducted since 2011 in a stream in the Yamakiya district, Fukushima Prefecture, and the Kuchibuto River and the Mizusakai River located downstream of the Yamakiya district. SS samplers and organic nets were used to collect SS and coarse organic matter, and water samples were sampled to measure Cs-137 concentrations using germanium semiconductor detectors in the laboratory. In addition, the concentrations of DOC, EC, and potassium ion in the stream and river water were also measured. As a result, dissolved Cs-137 concentrations in stream water were 1.5 to 2.0 times higher in summer than in other seasons, regardless of potassium ion concentrations.