[2M01-08] Environmental Radioactivity 2

[2M08] Investigation on distribution of radioactive substances in Fukushima

(14)Impact of decontamination using observational data on sediment runoff from mountain streams to rivers and cesium dynamics in Yamakiya

*Fumiaki Makino¹, Yuichi Onda¹, Slim Mtibaa², Syo Iwagami², Kesuke Taniguchi³ (1. Univ. of Tsukuba, 2. Forest Research & Management Org., 3. NIT Tsuyama College)

Keywords:Radiocesium, Fukushima Daiichi Nuclear Power Station accident, Arcgis, decontamination

It has been reported that decontamination activities have stripped the topsoil of agricultural land and removed debris from forest floors in forests, causing a large amount of sediment to flow into rivers. In this study, based on long-term monitoring from 2013 to 2019, we focused on the effect of decontamination activities in the upstream area on the 137Cs concentration in rivers in the Yamakiya district of Kawamata Town, Fukushima Prefecture. As a survey method, the amount of flowing water, the amount of sediment runoff, and the cesium concentration were measured using a partial flume, a water level gauge, and a turbidity meter SS sampler. A decontamination map was created using ArcGIS from information on decontamination obtained from the Ministry of the Environment. The normalized cesium concentration decreased rapidly in 2014 at Mt. Iwaishi, which was decontaminated, and the concentration of cesium did not decrease at Mt. Setohachi and Mt. Ishihira, which were not decontaminated. It was also found that the river has a cesium concentration in the middle of the headwater area.