Temporal change of 236U/238U and 235U/238U isotopic ratios in atmospheric deposition in Tokyo and Akita from 1963 to 1979
Temporal change of 236U/238U and 235U/238U isotopic ratios in atmospheric deposition in Tokyo and Akita from 1963 to 1979
复制标题
1963年至1979年东京和秋田大气沉降中236U/238U和235U/238U同位素比的时间变化
DOI：
10.1016/j.scitotenv.2021.151292
复制
发表时间：
2022
影响因子：
9.8
通讯作者：
Igarashi Yasuhito
中科院分区：
文献类型：
--
作者：
Ohno Takeshi;Sato Naoki;Shikimori Junko;Ijichi Yuta;Fukami Yusuke;Igarashi Yasuhito
本文分析了1963 ~ 1979年东京和秋田地区大气沉积物中236u /238U和235u /238U的时间变化，阐明了日本人为铀源的空间分布和历史变化。东京地区大气沉降236u /238U比值在1963年和20世纪70年代达到峰值，而第二次峰值期间对应的大气沉降235u /238U比值低于天然铀。秋田样品大气沉积的236u /238U比值在1963年达到峰值。秋田样品中的235u /238U比率几乎与天然铀比率相同。这些结果表明，1963年236u /238U的峰值对应于被认为是全球沉降的代表。1970年代同时观察到的236u /238U的增加和235u /238U的减少表明贫铀后来被释放到东京周围的环境中。1968 - 1979年在东京收集的大气沉降物样品中，236u的累积沉降密度比全球沉降物的累积沉降密度大一个数量级，表明20世纪70年代的贫化铀是东京236u的主要成分，在工业城市使用236u作为环境示踪剂时，应将其视为端元。这些知识可以促进未来使用236u作为有效的环境示踪剂的研究。
We examine the temporal changes of236U/238U and235U/238U in atmospheric deposition from samples collected in Tokyo and Akita from 1963 to 1979 and elucidate the spatial distribution and historical changes of the anthropogenic sources of uranium in Japan. The236U/238U ratio of atmospheric deposition in Tokyo peaked in 1963 and again during the 1970s, while the corresponding235U/238U ratios of atmospheric deposition during the second peak period were lower than that of natural uranium. The236U/238U ratios of atmospheric deposition in Akita samples peaked in 1963. The235U/238U ratios in Akita samples were almost identical to that of the natural uranium ratios. These results suggest that the peak of236U/238U in 1963 corresponds to what is recognized as representative for global fallout. The increase of236U/238U and the decrease of235U/238U observed simultaneously in the 1970s indicate that depleted uranium has subsequently been released into the environment around Tokyo. The cumulative deposition density of236U for atmospheric fallout samples collected in Tokyo from 1968 to 1979 is an order of magnitude larger than that of the global fallout, suggesting that the depleted uranium in the 1970s is a major component of236U in Tokyo and should be considered as an end-member when using236U as an environmental tracer in the industrial city. This knowledge can facilitate future research using236U as an effective environmental tracer.