[2C10-16] Fukushima 2

4:15 PM - 4:30 PM JST(7:15 AM - 7:30 AM UTC)

[2C16] Investigation on distribution of radioactive substances in Fukushima(11) Estimation of pathways based on the vertical distribution and temporal variation of 137Cs in the ocean derived from the Fukushima Daiichi Nuclear Power Plant accident

*Munehiro Asao¹, Tsumune Daisuke¹ (1. Univ. of Tsukuba)

Keywords:

Fukushima Daiichi Nuclear Power Plant accident,137Cs,Direct release,River discharge

After the accident at the Fukushima Daiichi Nuclear Power Plant (1F NPP), ¹³⁷Cs activity concentration near 1F NPP has not decreased to pre-accident levels because some pathways exist; direct release from 1F NPP, discharge from rivers, and recirculation from the North Pacific Ocean. The impact of each source is not fully understood. The purpose of this study was to estimate the major sources of ¹³⁷Cs at each station. We focused on the temporal variation and vertical distribution of ¹³⁷Cs. The trends of temporal variation differ between direct release and river discharge, and we estimated these contributions by analyzing the time-series changes at each station. We attempted to distinguish recirculation based on the vertical distribution. Direct release and river discharge, which are freshwater, are mainly distributed in the ocean surface layer, while the distribution of recirculation differs depending on ocean currents.