title: Spatial variations of 226Ra, 228Ra, 137Cs, and 228Th activities in the southwestern Okhotsk Sea.
abstract: We collected 14 water column seawater samples in the southwestern Okhotsk Sea and 7 surface samples around the northern area of Hokkaido Island, Northern Japan, and employed low-background γ-spectrometry with convenient minimal radiochemical processing to determine the activities of (226)Ra (half-life t(1/2)=1600 y), (228)Ra (5.75 y), (137)Cs (30.2 y), and (228)Th (1.91 y) in the samples. Activities of (226)Ra (~2.3 mBq/L), (228)Ra (~0.7 mBq/L), and (137)Cs (~1 mBq/L) of surface waters on the Okhotsk Sea side show notable differences from those on the Japan Sea side (Soya Warm Current Water; SWCW) (~1.5 mBq/L; 1.5-2 mBq/L; 1.4-1.6 mBq/L), indicating their different origins and lateral mixing patterns. All of these nuclides exhibit unique vertical profiles; activities of soluble (226)Ra, (228)Ra, (137)Cs, and reactive (228)Th exhibit small variations from 50 to 500 m depth ((226)Ra, ~2.2 mBq/L; (228)Ra, ~0.4 mBq/L; (137)Cs, ~1 mBq/L; (228)Th, ~0.13 mBq/L). These profiles can be explained by the convective mixing of surface water such as the East Sakhalin Current Water (ESCW) to this layer.
authors: Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Nomi, Ishikawa 923-1224, Japan. mutsuo@llrl.ku-unet.ocn.ne.jp
authors: Mutsuo
authors: M
authors: Inoue
authors: Keisuke
authors: K
authors: Yoshida
authors: Masayuki
authors: M
authors: Minakawa
authors: Hisaki
authors: H
authors: Kofuji
authors: Seiya
authors: S
authors: Nagao
authors: Yasunori
authors: Y
authors: Hamajima
authors: Masayoshi
authors: M
authors: Yamamoto
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis*; D007564:Japan; D009792:Oceans and Seas; D011834:Radiation Monitoring; D011883:Radium / Q000032:analysis*; D013910:Thorium / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive; D013910:Thorium; D011883:Radium