Investigation of Radiocesium Migration from Land to Waterbody using Radiocesium Distribution and Soil to Sediment Ratio: A Case of the Steep Slope Catchment Area of Ogi Reservoir, Kawauchi Village, Fukushima

In the present study, we reported the investigation of radiocesium migration from steep slope surrounding catchment to water body based on the radiocesium distribution and soil to sediment ratio. It was confirmed that the radiocesium was derived from the Fukushima accident by considering the 134 Cs to 137 Cs ratio corrected to the released day which is about 1. We found the higher radiocesium inventory in higher elevation area and steep slope forest catchment, revealing the atmospheric dry initial deposition-derived radiocesium and high retention of the forest zone. The radiocesium distribution data revealed that the radiocesium migrated more from the transition zone to the water body than from forest catchment, and accumulated in the deeper layer of sediment. The lower value of 137 Cs soil to sediment ratio provided an evidence of radiocesium migration from the catchment and its accumulation in the sediment. The physicochemical property of surface soil was revealed as one of the possible factors of radiocesium high retention in forest catchment.