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Distribution and source of Pu and 241Am in agricultural soils: re-estimation of global fallout 241Am/239+240Pu ratio
https://repo.qst.go.jp/records/85142
https://repo.qst.go.jp/records/8514202c3d4a2-4e00-4c5d-91b7-91dc9cd9cdfd
| Item type | 会議発表用資料 / Presentation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2022-02-22 | |||||
| タイトル | ||||||
| タイトル | Distribution and source of Pu and 241Am in agricultural soils: re-estimation of global fallout 241Am/239+240Pu ratio | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_c94f | |||||
| 資源タイプ | conference object | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
Zheng, Jian
× Zheng, Jian× Keiko, Tagami× Shigeo, Uchida× Wang, Zhongtang× Ni, Youyi× Zheng, Jian× Keiko, Tagami× Shigeo, Uchida |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | In this study the distribution of Pu isotopes and 241Am in Japanese upland agricultural fields were systematically investigated to understand the contamination level before the Fukushima nuclear accident. We analyzed 44 soil samples collected throughout Japan. The 239+240Pu and 241Am activity concentrations in these samples were 0.053-0.678 mBq/g and 0.022-0.255 mBq/g, respectively, which were comparable to those reported for different types of soils in the literature. The characteristic 240Pu/239Pu atom ratios (0.152-0.193, with an average of 0.175 ± 0.008) indicated the source of global fallout. However, the 241Am/239+240Pu activity ratios ranged from 0.338 to 0.689, with an average of 0.42 ± 0.07 (n =44), which is significantly higher than that of global fallout value of 0.35 in 2016 estimated by Livingston et al. (1975). 241Am in the environment was generated from the decay of fallout 241Pu that was released by the atmospheric nuclear tests concurrently with other Pu isotopes such as 239Pu and 240Pu. Two distinct time periods of atmospheric nuclear tests can be identified. The first period (1952-1958) was dominated by high-yield thermonuclear tests by the USA. After that, a series of large-scale atmospheric nuclear tests was carried out by the former Soviet Union (USSR). The widely used characteristic global fallout 241Am/239+240Pu activity ratios by Livingston et al. were based on the analysis of 241Pu mainly in marine sediments, and they ignored the contribution of 241Pu released in the environment from the 1950s nuclear tests period by assuming 241Am activity = 0 in 1962. Therefore, this global fallout 241Am/239+240Pu activity ratio was underestimated, and cannot be applied to the source identification of 241Am in terrestrial environment. In order to realize accurate source identification, we re-estimated the integrated 241Am/239+240Pu activity ratio for global fallout in Japanese soil environment by including the contribution of 241Pu released from both the tests in the 1950s and in the 1960s. Based on our new estimation, the global fallout 241Am/239+240Pu activity ratio should be 0.45 in 2016, the year of analysis of our upland soil samples.The integrated 241Am/239+240Pu activity ratio (0.42 ± 0.07) in Japanese upland soils corresponded well with our estimation of the characteristic global fallout value of 0.45, indicating that global fallout is the primary source of 241Am in the investigated upland soils. Thus, the distribution data of 239+240Pu and 241Am activity concentrations in upland agricultural soils in the root zone provided the basis for further study on the transfer of Pu isotopes and 241Am from soil to agricultural crops. |
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| 会議概要（会議名, 開催地, 会期, 主催者等） | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 第23回「環境放射能」研究会 | |||||
| 発表年月日 | ||||||
| 日付 | 2022-03-09 | |||||
| 日付タイプ | Issued | |||||
