Concentrations of
222
Rn, Its Short-Lived Daughters And
212
Pb And Their Ratios Under Complex Atmospheric Conditions And Topography |
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Authors: | Toshio Kataoka Eiji Yunoki Mitsuo Shimizu Tadashige Mori Osamu Tsukamoto Satoshi Takahashi Hironori Fudeyasu Yukitaka Ohashi Ken Sahashi Toshihiko Maitani Koh'ichi Miyashita Toru Iwata Takayuki Sasaki Yoko Fujikawa Akira Kudo Roger H Shaw |
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Institution: | (1) Okayama Prefectural Institute for Environmental Science and Public Health, 739-1, Uchio, Okayama, 701-0298, Japan;(2) Faculty of Science, Okayama University, 3-1-1, Tsushimanaka, Okayama, 700-0082, Japan;(3) Department of Geophysics, Kyoto University, Kitashirakawaoiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan;(4) Okayama University, 3-1-1 Tsushimanaka, Okayama 700-0082, Japan;(5) Environmental Science and Technology Department, Okayama University, 2-1-1, Tsushimanaka, Okayama, 700-0082, Japan;(6) Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-Gun, Osaka, 590-0451, Japan;(7) Land, Air and Water Resources, University of California, One Shields Avenue, Davis, California, 95616-8627, U.S.A |
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Abstract: | Atmospheric activity concentrations of 212Pb and short-lived 222Rndaughters, together with meteorological elements, have been observed continuously atthree sites at Kamisaibara Village in Japan. In addition, atmospheric activity concentrationof 222Rn, equilibrium-equivalent concentration of 222Rn and conditionsof the lower atmosphere were observed for three intensive observation periods at Akawase,one of the three sites in Kamisaibara Village. The equilibrium-equivalent concentration of222Rn is almost the same as the atmospheric activity concentration of short-lived222Rn daughters.The activity concentrations of 212Pb and the short-lived 222Rn daughtersand their ratio were low in the daytime owing to convective mixing, and high at nightowing to the surface-based inversion during periods of no precipitation. Their variationshave several patterns corresponding to the scale of the drainage wind or weak mixing.Mechanical mixing due to strong winds through both day and night during the first andsecond observation periods made the atmospheric activity concentrations of 212Pb and the short-lived 222Rn daughters continuously low. However, their ratios werecontinuously high during the first period yet continuously low during the second period.This difference can be explained by the effect ofextraction of 220Rn and 222Rndue to strong winds and snow cover. There were also cases in which the ratio of theatmospheric activity concentration of 212Pb to that of the short-lived 222Rndaughters at night was equal to or less than the ratio in the daytime. Thisinverse trend, asin the periods of no precipitation mentioned above, is considered to be due to near-neutralconditions on these nights.We find a difference in the ratio of the equilibrium-equivalent concentration of222Rn (the activity concentration of short-lived 222Rn daughters) tothe activity concentration of 222Rn during the first observation period and thatduring the second. The difference can be explained by snow cover on the ground. Wealso find differences among the ratios of the activity concentration of the short-lived222Rn daughters to that of 222Rn during the three observation periods.These differences can be explained by the submergence of paddy fields. |
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Keywords: | Concentration of 212Pb Concentration of 222Rn Concentration of short-lived 222Rn daughters Snow depth Submergence of paddy fields |
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