Everett S E, Tims S G, Hancock G J, Bartley R, Fifield L K
Department of Nuclear Physics, Research School of Physical Sciences and Engineering, The Australian National University, Building 57, Canberra, 0200 ACT, Australia.
J Environ Radioact. 2008 Feb;99(2):383-93. doi: 10.1016/j.jenvrad.2007.10.019. Epub 2007 Dec 11.
Following atmospheric nuclear weapons testing in the 1950s and 1960s significant quantities of (137)Cs and (239+240)Pu were deposited worldwide. In recent decades, (137)Cs has been commonly used as a tracer of soil erosion and sedimentation, particularly in the Northern Hemisphere where atomic deposition was three times as great as in the Southern Hemisphere. The relatively short 30-year half-life of this isotope means that its sensitivity as a tracer is rapidly decreasing. In contrast, with half-lives of 24,110 and 6561 years, the sensitivity of the two plutonium isotopes remains essentially the same as when it was deposited. Here we use the technique of Accelerator Mass Spectrometry to demonstrate the potential of anthropogenic Pu as an alternative to (137)Cs as a tracer of soil transport in Australia. We measure an average (137)Cs/(239+240)Pu activity ratio of 27.3+/-1.5 and an average (240)Pu/(239)Pu atom ratio of 0.149+/-0.003, both slightly lower than the global average.
在20世纪50年代和60年代进行大气层核武器试验之后，大量的铯-137（¹³⁷Cs）和钚-239及钚-240（²³⁹⁺²⁴⁰Pu）沉积于全球各地。近几十年来，铯-137一直被广泛用作土壤侵蚀和沉积的示踪剂，尤其是在北半球，那里的核沉降量是南半球的三倍。这种同位素相对较短的30年半衰期意味着其作为示踪剂的灵敏度正在迅速下降。相比之下，钚的这两种同位素的半衰期分别为24110年和6561年，其灵敏度基本保持在沉降时的水平。在此，我们运用加速器质谱技术来证明，人为来源的钚在澳大利亚作为土壤运移示踪剂替代铯-137的潜力。我们测得铯-137与钚-239及钚-240的活度比平均为27.3±1.5，钚-240与钚-239的原子比平均为0.149±0.003，两者均略低于全球平均水平。
