Japan Geoscience Union Meeting 2016

Presentation information

Poster

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 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

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)

5:15 PM - 6:30 PM

[MAG24-P02] Long-term prediction models of atmospheric concentration of Cs-137 and their comparison with AIC

*Shoki Konishi1, Yuko Hatano1 (1.University of Tukuba)

Keywords: activity concentration, aerosol, resuspention

In the Fukushima Daiichi nuclear power plant accident, a large amount of radioactive nuclides were released. Ceasium-137 is one of the most significant radionuclides which were released in large amount to the atmospheric and has a half-life of thirty years; the Cs-137 pollutes the atmosphere for a long term. Some models which can predict the concentration of Cs-137 for long term have been proposed.
In this study, first, I evaluate the seasonal variation in the concentration change of Cs-137. Analyzing the residuals between the measured data and the models, we reveal periodic fluctuations with the period of one year. We found that the changes of the concentration is in the form the sine curve of the one year period, which reaches at the maximum value in the summer and minimum in the winter. Adding such a sine curve in long-term models, we propose a new model considering seasonal variation. Second, we compare the accuracy of the models. Some models to reproduce the atmospheric concentration of Cs-137 have been proposed, but they are not evaluated quantitatively with regard to which model is the best. We evaluate some models using Akaike’s Information Criterion(AIC). AIC evaluate some models on consistency and number of free parameters. At first, we evaluate which is good, considering seasonal variation or not. As a result, model considering seasonal variation is better. Second, I evaluate some proposed models. As a result, the best model is C(t)=Aexp(-λdecayt)t-α (then C(t) is concentration of Cs-137, λdecay is decay constant of Cs-137, A and α are free parameter). This is conclusion that C(t)=Aexp(-λdecayt)t-α and considering seasonal variation is the best model.