Shiroma Y, Kina S, Fujitani T, Hosoda M, Sorimachi A, Ishikawa T, Sahoo S K, Tokonami S, Furukawa M
Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.
Radiat Prot Dosimetry. 2012 Nov;152(1-3):184-8. doi: 10.1093/rpd/ncs220. Epub 2012 Aug 29.
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.
在日本亚热带地区冲绳县的三个岛屿上，估算了地表的氡和钍射气率。使用ZnS(Ag)闪烁探测器的累积技术，在总共88个点进行了射气率的现场测量。计算得出氡和钍的射气率分别为1 - 137（算术平均值：21）mBq m(-2) s(-1)和32 - 6244（1801）mBq m(-2) s(-1)。在53个测量点采集的表层土壤样本中，(238)U和(232)Th系列浓度估计分别为17.9 - 254.0（64.0）Bq kg(-1)干重和17.8 - 136.1（58.8）Bq kg(-1)干重。在深红色土壤区域观测到了最高的射气率和浓度。近期研究有力地表明，土壤的基底物质可能是来自中国东南部高本底辐射地区的风尘。因此，风尘被认为是冲绳县氡和钍射气的增强因素。
