title: Characteristics of radon and thoron exhalation rates in Okinawa, subtropical region of Japan.
abstract: Radon and thoron exhalation rates from the ground surface were estimated in three islands of Okinawa Prefecture, a subtropical region of Japan. In situ measurements of the exhalation rates were conducted at a total of 88 points using an accumulation technique with a ZnS(Ag) scintillation detector. The radon and thoron exhalation rates were calculated to be 1-137 (arithmetic mean: 21) mBq m(-2) s(-1) and 32-6244 (1801) mBq m(-2) s(-1), respectively. In the surface soil samples collected at 53 measurement points, (238)U and (232)Th series concentrations were estimated to be 17.9-254.0 (64.0) Bq kg(-1) dry and 17.8-136.1 (58.8) Bq kg(-1) dry, respectively. The maximum rates and concentrations were observed in the dark red soil area. Recent studies strongly suggest that the base material of the soils may be the eolian dust derived from the southeastern part of China, a high background radiation area. The eolian dust is, therefore, considered to be an enhancer for the radon and thoron exhalations in Okinawa.
authors.affiliation: Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan. k128606@eve.u-ryukyu.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Shiroma
authors.forename: S
authors.initials: S
authors.lastname: Kina
authors.forename: T
authors.initials: T
authors.lastname: Fujitani
authors.forename: M
authors.initials: M
authors.lastname: Hosoda
authors.forename: A
authors.initials: A
authors.lastname: Sorimachi
authors.forename: T
authors.initials: T
authors.lastname: Ishikawa
authors.forename: S K
authors.initials: SK
authors.lastname: Sahoo
authors.forename: S
authors.initials: S
authors.lastname: Tokonami
authors.forename: M
authors.initials: M
authors.lastname: Furukawa
mesh_terms: D000396:Air Pollutants, Radioactive / Q000032:analysis*; D001417:Background Radiation; D002681:China; D004781:Environmental Exposure; D007564:Japan; D011834:Radiation Monitoring / Q000379:methods*; D011886:Radon / Q000032:analysis*; D017687:Radon Daughters / Q000032:analysis; D012588:Scintillation Counting; D012987:Soil; D012990:Soil Pollutants, Radioactive / Q000032:analysis*
chemical_list: D000396:Air Pollutants, Radioactive; D017687:Radon Daughters; D012987:Soil; D012990:Soil Pollutants, Radioactive; D011886:Radon