A modeling approach to estimate H discharge from rivers: Comparison of discharge from the Fukushima Dai-ichi and inventory in seawater in the Fukushima coastal region.

Estimation of H discharge from river catchments is important to evaluate the effect of Fukushima Dai-ichi discharge and future planned H release to the ocean on the coastal environment. Using a previously developed model based on the tank model and observed H concentration in river water, the H discharge from the Abukuma River and 13 other rivers in the Fukushima coastal region were estimated from June 2013 to March 2020. The H discharge from catchments of the Abukuma River and 13 other rivers in the Fukushima coastal region during 2014-2019 were estimated to be 1.2-4.0 TBq/y. These values were approximately 2-22 times larger than the annual H discharge from the Fukushima Dai-ichi after 2016, indicating the significance of H discharge from the catchments through the rivers. This estimation is expected to be useful to evaluate and predict H concentrations and inventories in the Fukushima coastal region for consideration of planned H release to the ocean.