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Otosaka, Shigeyoshi; Suzuki, Takashi; Nakanishi, Takahiro; Kuwabara, Jun; Sato, Yuhi
no journal, ,
From August to November 2011, seabed sediments were collected from off Fukushima and Ibaraki prefectures and 
I concentration in the sediments was measured with accelerator mass spectrometry. I concentration in the surface sediment (0-1 cm layer) ranged between 0.045 and 0.48 mBq/kg-dry, and was several times higher than that in 2009. The activity ratio of I, considered to originates from the accident of Fukushima Daiichi NPP, over 
Cs in seabed sediment was higher than those in surface seawater. These results indicate that radioiodine was selectively adsorbed onto particles in the surface seawater or in the sediment-water interface, and accumulated in the seabed sediments.
Cs concentration due to the Fukushima Daiichi Nuclear Power Plant accidentKawamura, Hideyuki; Kobayashi, Takuya; Furuno, Akiko; Usui, Norihisa*; Kamachi, Masafumi*
no journal, ,
In this study, we conducted numerical experiments on oceanic dispersion of Cs discharged from the Fukushima Daiichi Nuclear Power Plant (FNPP1) in the North Pacific. A oceanic dispersion model (SEA-GEARN) based on difference equations was used in order to clarify surface dispersion as well as intermediate dispersion of Cs. We used reanalysis data calculated by a three-dimensional variational data assimilation system (MOVE) developed at Meteorological Research Institute, Japan Meteorological Agency. It was suggested that highly polluted water discharged from the FNPP1 was efficiently diluted by meso-scale eddies in the Kuroshio extension region. Simultaneously, these meso-scale eddies played an important role to carry Cs into the intermediate layer in the Kuroshio extension region. The directly discharged Cs was fundamentally carried eastward and it attained at approximately 165
W in August, 2012.