135Cs/137Cs Isotopic Ratio as a New Tracer of Radiocesium Released from the Fukushima Nuclear Accident

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• 作者：Jian Zheng ; Keiko Tagami ; Wenting Bu ; Shigeo Uchida ; Yoshito Watanabe ; Yoshihisa Kubota ; Shoichi Fuma ; Sadao Ihara
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：May 20, 2014
• 年：2014
• 卷：48
• 期：10
• 页码：5433-5438
• 全文大小：266K
• 年卷期：v.48,no.10(May 20, 2014)
• ISSN：1520-5851

文摘

Since the Fukushima Daiichi nuclear power plant (FDNPP) accident in 2011, intensive studies of the distribution of released fission products, in particular ¹³⁴Cs and ¹³⁷Cs, in the environment have been conducted. However, the release sources, that is, the damaged reactors or the spent fuel pools, have not been identified, which resulted in great variation in the estimated amounts of ¹³⁷Cs released. Here, we investigated heavily contaminated environmental samples (litter, lichen, and soil) collected from Fukushima forests for the long-lived ¹³⁵Cs (half-life of 2 脳 10⁶ years), which is usually difficult to measure using decay-counting techniques. Using a newly developed triple-quadrupole inductively coupled plasma tandem mass spectrometry method, we analyzed the ¹³⁵Cs/¹³⁷Cs isotopic ratio of the FDNPP-released radiocesium in environmental samples. We demonstrated that radiocesium was mainly released from the Unit 2 reactor. Considering the fact that the widely used tracer for the released Fukushima accident-sourced radiocesium in the environment, the ¹³⁴Cs/¹³⁷Cs activity ratio, will become unavailable in the near future because of the short half-life of ¹³⁴Cs (2.06 years), the ¹³⁵Cs/¹³⁷Cs isotopic ratio can be considered as a new tracer for source identification and long-term estimation of the mobility of released radiocesium in the environment.