Field and Laboratory Studies of Radiocesium Transfers in Soil-Water Environment at Fukushima Prefecture

Abstract:

The systematic monitoring studies of radiocesium concentrations in suspended sediments and water of the Abukuma River, the largest river of Fukushima prefecture, and its tributaries at the vicinity of Fukushima city have started in Fukushima University at the end of 2011. The scale of these field studies was extended after establishment in 2013 new Institute of Environmental Radioactivity at Fukushima University which posses the comprehensive laboratory base. The field measurements of hydrochemical water parameters and concentrations of radiocesium in water and sediments are provided in the rivers of northern coastal zone of Fukushima province with the most comprehensive program for Niida River basin. The radiocesium dynamics is studied in Sakashita Reservoir and heavily contaminated irrigation ponds of Okuma town in the vicinity of FDNPP, Takanokura Reservoir, Inawashiro Lake, Hibara Lake. Comparative analysis is provided for radiocaesium wash-off parameters and distribution coefficient in rivers and surface runoff on Fukushima and Chernobyl contaminated areas for the first years after the accidents. It is found that radiocaesium distribution coefficient in rivers of Fukushima is essentially higher (1-2 orders of magnitude) than correspondent values for rivers and surface runoff of the Chernobyl zone. Normalized dissolved wash-off coefficients for watersheds of Fukushima are at least 1 order of magnitude lower correspondent values for Chernobyl zone. Normalized particulate wash-off coefficients are comparable for Fukushima and Chernobyl. Presented are results of the investigation of radiocesium vertical distribution in soils of the close-in area of the FDNPP: Okuma town and Niida River basin. It is shown that radiocesium dispersion in undisturbed forest and grassland soils at Fukushima contaminated area is significantly faster as compared to the Chernobyl 30-km zone during the first three years after the accidents.