Shao Yang, Yang Guosheng, Xu Diandou, Yamada Masatoshi, Tazoe Hirofumi, Luo Min, Cheng Hangxin, Yang Ke, Ma Lingling
Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China; Department of Radiation Chemistry, Institute of Radiation Emergency Medicine, Hirosaki University, 66-1 Hon-cho, Hirosaki, Aomori, 036-8564, Japan; School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, 100049, China.
Department of Radiation Chemistry, Institute of Radiation Emergency Medicine, Hirosaki University, 66-1 Hon-cho, Hirosaki, Aomori, 036-8564, Japan.
J Environ Radioact. 2019 Feb;197:1-8. doi: 10.1016/j.jenvrad.2018.11.009. Epub 2018 Nov 18.
More nuclear power plants continue to be built in China. Due to its long half-life, radiotoxicity and potential application as an environmental tracer, U is one of the most important artificial radionuclides deserving more study since activity data are important for risk assessment. However, the ultra-trace activity of U and its dilution by natural uranium isotopes make it difficult to distinguish its sources and there are only limited global fallout U data for present in Chinese environmental samples. In order to understand the background levels for uranium isotopes, especially U, and clarify their sources, inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) was applied to analyze uranium isotopes in 48 soil samples from Hunan Province, China. The U, U, U and U concentrations were measured as 9.91-33.7, 0.312-1.43, 6.63-28.7 Bq kg and (1.61-21.3) × 10 atoms g, while, the U/U, U/U and U/U atom ratios were (0.470-4.91) × 10, (5.10-9.31) × 10, and (7.11-7.82) × 10, respectively. The uranium isotopic fractionation may be due to irrigation of the agricultural lands where the samples were collected. Considering the facts that neither previous nuclear tests nor nuclear accidents had occurred in Hunan Province and the present U/U atom ratios were included in the range of global fallout values in other areas, it may be concluded that U in soils from Hunan Province is mainly from global fallout. To the best of the authors' knowledge, the presence of global fallout U in soil samples from China has been confirmed for the first time, and these values may be useful as background data for risk assessment in the future.
中国继续建造更多的核电站。由于其半衰期长、放射性毒性以及作为环境示踪剂的潜在应用，铀是最重要的人造放射性核素之一，值得更多研究，因为活度数据对于风险评估很重要。然而，铀的超痕量活度及其被天然铀同位素稀释，使得难以区分其来源，并且中国环境样品中目前仅有有限的全球沉降铀数据。为了了解铀同位素的背景水平，特别是铀-236，并阐明其来源，采用电感耦合等离子体质谱联用仪（ICP-MS/MS）对中国湖南省48个土壤样品中的铀同位素进行了分析。铀-234、铀-235、铀-236和铀-238的浓度分别测定为9.91 - 33.7、0.312 - 1.43、6.63 - 28.7 Bq/kg和(1.61 - 21.3)×10⁻⁶原子/g，而铀-236/铀-238、铀-235/铀-238和铀-234/铀-238原子比分别为(0.470 - 4.91)×10⁻⁶、(5.10 - 9.31)×10⁻⁶和(7.11 - 7.82)×10⁻²。铀同位素分馏可能是由于采集样品的农田进行了灌溉。考虑到湖南省既未发生过核试验也未发生过核事故，且目前的铀-236/铀-238原子比在其他地区全球沉降值范围内，可得出结论，湖南省土壤中的铀-236主要来自全球沉降。据作者所知，首次在中国土壤样品中证实了全球沉降铀-236的存在，这些值可能在未来作为风险评估的背景数据有用。
