Japan Geoscience Union Meeting 2016

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Symbol M (Multidisciplinary and Interdisciplinary) » M-AG Applied Geosciences

[M-AG24] Dynamics of radionuclides emitted from Fukuchima Dai-ichi Nuclear Power Plant in the environment

Mon. May 23, 2016 9:00 AM - 10:30 AM A03 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Kazuyuki Kita(Faculty of Science, Ibaraki University), Yuichi Onda(Center for Research on Isotopes and Environmental Dynamics, University of Tsukuba), Teruyuki Nakajima(Japan Aerospace Exploration Agency), Yasuhito Igarashi(Atmospheric Environment and Applied Meteorology Research Department, Meteorological Research Institute), Masatoshi Yamada(Institute of Radiation Emergency Medicine, Hirosaki University), Chisato Takenaka(Graduate School of Bioagricultural Sciences, Nagoya University), masayoshi yamamoto(Low Level Radioactivity Laboratory, Kanazawa University), Jota Kanda(Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology), Atsushi Shinohara(Osaka university), Chair:Yukihiko Satou(Graduate School of Pure and Applied Sciences, University of Tsukuba)

9:30 AM - 9:45 AM

[MAG24-03] Long-term assessment of airborne radio-cesium after the Fukushima nuclear accident: re-suspension from soil and vegetation

*Mizuo Kajino1,2, Masahide Ishizuka3, Yasuhito Igarashi3, Kazuyuki Kita4, Chisato Yoshikawa5, Masaru Inatsu6 (1.Meteorological Research Institute, 2.RIKEN Advanced Institute for Computational Science, 3.Kagawa University, 4.Ibaraki University, 5.Japan Agency for Marine-Earth Science and Technology, 6.Hokkaido University)

Keywords:Dust deflation module, Three dimensional numerical model, Atmospheric measurement, Budget analysis

Long-term assessment of 137Cs re-suspension from contaminated soil and vegetation due to the Fukushima nuclear accident in March 2011 and the on-going emission from the premises of the power plant has been conducted using a numerical simulation, a field experiment on the dust deflation at Namie in the restricted habitation area, and air concentration measurements in and out of the area, Namie and Tsukuba, respectively. The analysis period is one year from December 2012, about one and a half years from the accident, up to December 2013. The surface concentration of Cs-137 at Namie was high in the summer (~1 mBq/m3) and low in the winter (0.1-1 mBq/m3). The 137Cs concentration was about one order smaller in Tsukuba (0.01-0.1 mBq/m3). The differences in the two sites are consistent between the observation and the simulation. Ishizuka et al. (2016) developed a numerical module of 137Cs re-suspension associated with dust deflation based on the flux measurement in Namie. Using the module, the simulated 137Cs from soil had a potential to account for the observed surface concentration in Namie in the winter, but underestimated by 1-2 orders of magnitude in the summer. The Tokyo Electric Power Company assessed the 137Cs emission from the reactor buildings in 2013 as approximately 106 Bq/h. By using the emission rate, the simulation substantially underestimated the observation by 2-3 orders of magnitude in Namie. We simulated the re-suspension from vegetation applying a seasonal variation as a function of the green fraction map. With the constant re-suspension rate of 10-7 [/h], the simulated vegetation re-suspension quantitatively accounted for the observed surface concentration together with its seasonal variation. Still, so far, the re-suspension mechanism has not been fully understood and thus further investigations for the understanding of the mechanisms and its long-term effects on the environment are needed.