[2A08-12] Environmental Radioactivity and Monitoring 2

[2A11] Investigation on distribution of radioactive substances in Fukushima

(11)Changes in dissolved radioactive cesium concentrations in stream water at the headwater catchment in Namie town, Fukushima Prefecture

*Satoru Akaiwa¹, Hiroaki Kato¹, Tomoki Shinozuka¹, Hikaru Iida¹, Yuichi Onda¹ (1. University of Tsukuba)

Keywords:dissolved Cs-137, stream water, soil water, headwater catchment

This study aims to elucidate the formation mechanism of dissolved radiocesium concentrations in surface water in the forest head watershed in Namie. The survey was conducted from June 2018 and December 2019. The flow, temperature, and water temperature in the watershed, disCs-137 concentration in the spring, stream water, and near-stream soil water and suspended cesium-137 concentration in coarse organic matter and suspended sediment was observed. The results showed a positive correlation between surface water and soil water. The spring water decreased with increasing flow rate. Furthermore, the disCs-137 concentrations increase from the upstream to the downstream direction. The results showed that the concentration of disCs--137 in surface water fluctuated with temperature . From these results, it was found that the factors of variation in the concentration of disCs-137 in surface water were the changes in temperature and the expansion and contraction of the saturated soil zone at the head of the source due to changes in flow and groundwater flow, resulting in the dissolved state in surface water.