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Kawamura, Hideyuki; Furuno, Akiko; Kobayashi, Takuya; In, Teiji*; Nakayama, Tomoharu*; Ishikawa, Yoichi*; Miyazawa, Yasumasa*; Usui, Norihisa*
no journal, ,
This study simulates the oceanic dispersion of Fukushima-derived Cs-137 by an oceanic dispersion model SEA-GEARN-FDM and multiple oceanic general circulation models. The oceanic dispersion simulations relatively well reproduced the measured Cs-137 concentrations in the coastal and offshore oceans during the first few months after the Fukushima disaster, and in the open ocean during the first year post-disaster. It was suggested that Cs-137 dispersed along the coast in the north-south direction during the first few months post-disaster, and were subsequently dispersed offshore by the Kuroshio Current and Kuroshio Extension. The Cs-137 amounts were quantified in the coastal, offshore, and open oceans during the first year post-disaster. It was demonstrated that Cs-137 actively dispersed from the coastal and offshore oceans to the open ocean, and from the surface layer to the deeper layer in the North Pacific.
Kadowaki, Masanao; Katata, Genki*; Terada, Hiroaki; Suzuki, Takashi; Hasegawa, Hidenao*; Akata, Naofumi*; Kakiuchi, Hideki*
no journal, ,
Iodine-129 (
I) has been shown as a useful isotope for dating of water, tracing of marine sediments and investigating the geochemical cycle of iodine. Main sources of atmospheric I are volatilization from ocean and discharge from nuclear fuel reprocessing facilities. Although released I is globally transported in the atmosphere and deposited to the Earth's surface, spatial and temporal distributions of atmospheric I are still not well understood. In this study, we developed an atmospheric global transport model of I which includes the processes such as advection and turbulent diffusion, dry and wet deposition, discharge from nuclear fuel reprocessing facility, volatilization from ocean and atmospheric chemical reactions (atmospheric photolysis and gas-particle conversion). Input meteorological fields of three-dimensional components of wind, air temperature, atmospheric pressure, and turbulent diffusion coefficient were calculated using WRF (Weather Research and Forecasting) with ERA-Interim dataset. The simulation period was set to be from 1 Jan 2006 to 31 Dec 2010. For model validation, we used air concentration and deposition of gaseous and particulate forms of I measured at Rokkasho in Japan from 2006 to 2010 and past measurements of I concentration in rain water in Europe, Asia, and North America. The model successfully reproduced the seasonal variations of measured air concentration and deposition of I at Rokkasho as maximum and minimum values during the wintertime and summertime, respectively. Furthermore, spatial patterns of simulated I concentration in globe were similar to those of measurements. In the presentation, key factors in controlling the spatiotemporal distribution of airborne I and its cycle in the atmosphere suggested by model results will be discussed.
Shimizu, Mayuko; Sano, Naomi; Ueki, Tadamasa; Yonaga, Yusuke; Yasue, Kenichi*; Niwa, Masakazu
no journal, ,
Aoki, Kazuhiro; Seshimo, Kazuyoshi; Sakai, Toru*; Komine, Yusuke*; Kametaka, Masao*; Watanabe, Takahiro; Nussbaum, C.*; Guqlielmi, Y.*
no journal, ,