Variations of ¹²⁹I in the atmospheric fallout of Tokyo, Japan: 1963-2003

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• 作者：Chiaki Toyama ; Yasuyuki Muramatsu ; Yuka Uchida ; Yasuhito Igarashi ; Michio Aoyama ; Hiroyuki Matsuzaki
• 关键词：Iodine-129 ; Atmospheric deposition ; 129I/127I ratio ; Tokai Reprocessing plant
• 刊名：Journal of Environmental Radioactivity
• 出版年：2012
• 出版时间：November, 2012
• 年：2012
• 卷：113
• 期：Complete
• 页码：116-122
• 全文大小：494 K

文摘

Atmospheric fallout samples collected from Tokyo between 1963 and 2003 were analyzed using accelerator mass spectrometry (AMS) in order to determine ¹²⁹I/¹²⁷I ratios and to examine the deposition rate of ¹²⁹I and its secular variation in Tokyo. The ¹²⁹I/¹²⁷I ratios in the atmosphere during 1963-1977 ranged from 1?¡Á?10^?8 to 2?¡Á?10^?8. This is roughly 4 orders of magnitude higher than pre-atomic levels, possibly due to atmospheric nuclear weapons tests. The calculated monthly atmospheric deposition rates of ¹²⁹I differed from those produced by nuclear fallout of ⁹⁰Sr and ¹³⁷Cs, indicating that the variations in ¹²⁹I deposition are not influenced exclusively by either nuclear bomb testing or by the Chernobyl accident. After 1978, high ¹²⁹I depositions (up to 0.13?mBq/m²/month) were observed. The ¹²⁹I depositions started to increase markedly at the latter half of the 1970s. The secular variation of the estimated annual ¹²⁹I deposition in Tokyo showed a close relationship between the annual atmospheric discharge of ¹²⁹I from the Tokai Reprocessing plant. Therefore, the atmospheric fallout collected from Tokyo after the late 1970s is influenced primary by the ¹²⁹I discharge from the Tokai Reprocessing plant.