Factors affecting 137Cs concentrations in river water under base-flow conditions near the Fukushima Dai-ichi Nuclear Power Plant

To confirm factors affecting Cs-137 concentration in river water after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, this study conducted monthly observations of nine rivers near the FDNPP from April 2017 to March 2018 under base-flow conditions. The annual mean dissolved and particulate Cs-137 concentrations correlated well with the mean Cs-137 deposition in the catchment. The normalized Cs-137 concentrations in both phases by dividing by the mean Cs-137 deposition in the catchment showed significant negative correlations with the Cs-137 deposition ratio for forests. The inflow from the downstream plain areas increased the Cs-137 concentrations near the FDNPP.

Automated summary

The study found that the Cs-137 concentration in river water after the Fukushima Dai-ichi Nuclear Power Plant accident was closely related to the mean Cs-137 deposition in the catchment and the Cs-137 deposition ratio for forests. Additionally, Cs-137 concentrations near the FDNPP increased due to inflow from downstream plain areas.