Seasonal and spatial variations of enhanced gamma ray dose rates derived from 222Rn progeny during precipitation in Japan |
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| Institution: | 1. Climate Research Department, Meteorological Research Institute, 1-1 Nagamine, Tsukuba, Ibaraki 305-0052, Japan;2. Geochemical Research Department, Meteorological Research Institute, 1-1 Nagamine, Tsukuba, Ibaraki 305-0052, Japan;1. Meme Media Laboratory, Hokkaido University, Japan;2. Yukawa Institute for Theoretical Physics, Kyoto University, Japan;1. Department of Materials Science, Osaka Prefecture University, 1-1, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan;2. Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980-8577, Japan;3. Japan Atomic Energy Agency (JAEA), Takasaki Advanced Radiation Research Institute, 1233, Watanuki-machi, Takasaki, Gunma 370-1292, Japan;4. Japan Atomic Energy Agency (JAEA), Tokai Research and Development Center, Naka-ku, Ibaraki 319-1195, Japan;5. Research Organization for the 21st Century, Osaka Prefecture University, 1-1, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan;1. Department of Life Science and Graduate School of Life Science, Rikkyo (St. Paul’s ) University, Toshima-ku, Tokyo 171-8501, Japan;2. Application Laboratory, Rigaku Corporation, 3-9-12 Matsubara-cho, Akishima-shi, Tokyo 196-8666, Japan;3. Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan;1. Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan;2. The Hakubi Center for Advanced Research, Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto 606-8302, Japan;3. Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan;4. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan;5. ISS Project Science Office, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2-1 Sengen, Tsukuba, Ibaraki 305-8505, Japan;6. Department of Applied Physics, University of Miyazaki, 1-1 Gakuen Kibana-dai Nishi, Miyazaki 889-2192, Japan;7. Physics Department, Kogakuin University, 2665-1, Nakano-cho, Hachioji, Tokyo 192-0015, Japan;8. The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan;9. Department of Information Science, Faculty of Liberal Arts, Tohoku Gakuin University, 2-1-1 Tenjinzawa, Izumi-ku, Sendai, Miyagi 981-3193, Japan;1. Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan;2. Unit of Elements Strategy Initiative for Catalysts & Batteries, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan |
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| Abstract: | Enhanced gamma (Δγ) ray dose rates due to 222Rn progeny wet deposited on the ground surface measured at six monitoring sites in Japan were statistically analyzed to investigate their temporal and spatial variations. Variations of Δγ ray dose rates indicated significant regional differences between the sites on the Sea of Japan coast and those located inland and on the Pacific coast in Japan. At the sites located on the Sea of Japan coast, significant seasonal variation was evident, with higher dose rates in autumn and winter, and lower dose rates in summer. In contrast, however, no significant seasonal variation was observed at the inland and Pacific coast sites in Japan. The variation of Δγ ray dose rates was characterized by three major factors: climatologically changed air masses arriving in Japan, variation of 222Rn and its progeny concentrations in the air column, and the regional characteristics of precipitation. It is evident that the contribution from local 222Rn to Δγ ray dose rates was smaller than those from continental 222Rn. Meso-scale atmospheric disturbance, however, was suggested as an important process for extremely high Δγ ray dose rates, possibly by the accumulation of additional local 222Rn with stronger convergence. It is therefore possible that the variation of Δγ ray dose rates reflects the chemical climatology of 222Rn and its progeny. |
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