Long-term prediction of environmental fate of Cs in ocean considering migration process of Cs in a lower trophic level ecosystem

Ikenoue, Tsubasa  ; Nakanishi, Takahiro   ; Kawamura, Hideyuki  

The accident at the Fukushima Daiichi Nuclear Power Plant in March 2011 resulted in the release of radionuclides in the marine environment. Among the radionuclides released, since large quantities of Cs were released and Cs has a long half-life, there is concern about the impacts of Cs on marine environment. Most of Cs is dissolved in seawater, but some Cs is taken in and adsorbed on biogenic particles (phytoplankton, zooplankton, and detritus). In this study, we aim to predict the long-term fate of Cs in ocean considering migration process of Cs in a lower trophic level ecosystem. We improved an oceanic dispersion model by coupling with a lower trophic level ecosystem model and conducted the long-term simulation of Cs in ocean. This improvement enabled the long-term prediction of Cs concentrations in biogenic particles and organic seabed sediment as well as in seawater. The calculation results suggested that the adsorption process from seawater to organic sediment had a much greater impact on Cs concentration in organic seabed sediment than the sedimentation process of biogenic particles.