12:00 PM - 12:15 PM
[MAG34-12] The rapid deline of Cs-137 concentration in Fukushima rivers
Keywords:Cs-137, Fukushima NPP accident, runoff from rivers
In the Chernobyl affected area, land use has been found to be affected the cleanup of the contaminated terrestrial environment , but precipitation and the land use is quite different affected by the radionuclides by FDNPP accident. Here we show the results by intensive field monitoring campaign, started in June, 2011, 3 months after the accident, monitoring 30 river stations for detailed monitoring of activity concentration of radiocesium in suspended sediment and their flux flown through the river.
Total 13 TBq of Cs have been transported to ocean from Abukuma river, this corresponds to 2.5 % of the total fallout from July 2011 to August 2015. Analysis of the riverine transport by upstream landuse reveals that higher percentage of Paddy field having largest rate of decline and also the highest flux, but the forest area showing lowest decline and smallest flux flowing downstream. The entrainment coefficient of dissolved water is quite low; due to high initial decrease by active landuses, combining with high flux, typically 1 order lower than the lower end by the report of Chernobyl affected area, suggesting the rapid recovery of Fukushima contamination. We also analyze the effect of decontamination works on the activity and flux of the suspended sediment in the rivers.