2024-03-28T22:27:35Z
https://tsukuba.repo.nii.ac.jp/oai
oai:tsukuba.repo.nii.ac.jp:00054083
2022-04-27T09:28:13Z
160:2163
160:7475
3:62:5592:1618
Impacts of direct release and river discharge on oceanic 137Cs derived from the Fukushima Dai-ichi Nuclear Power Plant accident
恩田, 裕一
オンダ, ユウイチ
ONDA, Yuichi
青山, 道夫
アオヤマ, ミチオ
AOYAMA, Michio
Tsumune, Daisuke
Tsubono, Takaki
Misumi, Kazuhiro
Tateda, Yutaka
Toyoda, Yasushi
© 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
A series of accidents at the Fukushima Dai-ichi Nuclear Power Plant (1F NPP) following the Great East Japan Earthquake and tsunami of 11 March 2011 resulted in the release of radioactive materials to the ocean. We used the Regional Ocean Model System (ROMS) to simulate the 137Cs activity in the oceanic area off Fukushima, with the sources of radioactivity being direct release, atmospheric deposition, river discharge, and inflow across the domain boundary. The direct release rate of 137Cs after the accident until the end of 2016 was estimated by comparing simulated results with measured 137Cs activities adjacent to the 1F NPP. River discharge rates of 137Cs were estimated by multiplying simulated river flow rates by the dissolved 137Cs activities, which were estimated by an empirical function. Inflow of 137Cs across the domain boundary was set according to the results of a North Pacific Ocean model. Because the spatiotemporal variability of 137Cs activity was large, the simulated results were compared with the annual averaged observed 137Cs activity distribution. Normalized annual averaged 137Cs activity distributions in the regional ocean were similar for each year from 2013 to 2016. This result suggests that the annual averaged distribution is predictable. Simulated 137Cs activity attributable to direct release was in good agreement with measurement data from the coastal zone adjacent to the 1F NPP. Comparison of the simulated results with measured activity in the offshore area indicated that the simulation slightly underestimated the activity attributable to inflow across the domain boundary. This result suggests that recirculation of subducted 137Cs to the surface layer was underestimated by the North Pacific model. During the study period, the effect of river discharge on oceanic 137Cs activity was small compared to the effect of directly released 137Cs.
Elsevier
2020-04
eng
journal article
http://hdl.handle.net/2241/00159500
https://tsukuba.repo.nii.ac.jp/records/54083
10.1016/j.jenvrad.2020.106173
0265931X
AA10458871
Journal of environmental radioactivity
214-215
106173
https://tsukuba.repo.nii.ac.jp/record/54083/files/JER_2014-2015.pdf
application/pdf
3.1 MB
2020-01-28