Export of radioactive cesium from agricultural fields under simulated rainfall in FukushimaElectronic supplementary information (ESI) available. See DOI: 10.1039/c5em00063g

In this study, we investigated the impact of rainfall on runoff, soil erosion and consequently on the discharge of radioactive cesium in agricultural fields in Fukushima prefecture using a rainfall simulator. Simulated heavy rainfalls (50 mm h −1 ) generated significant runoff and soil erosion. The average concentration of radioactive cesium (the sum of 134 Cs and 137 Cs) in the runoff sediments was ∼3500 Bq kg −1 dry soil, more than double the concentrations measured in the field soils which should be considered in studies using the 137 Cs loss to estimate long-term soil erosion. However, the estimated mass of cesium discharged through one runoff event was less than 2% of the cesium inventory in the field. This suggested that cesium discharge via soil erosion is not a significant factor in reducing the radioactivity of contaminated soils in Fukushima prefecture. However, the eroded sediment carrying radioactive cesium will deposit into the river systems and potentially pose a radioactivity risk for aquatic living organisms. The first detailed investigation of the radioactive cesium export process from upland fields under simulated rainfall in Fukushima.