Global distribution of Pu isotopes and 237Np
Global distribution of Pu isotopes and 237Np
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DOI：
10.1016/s0048-9697(99)00160-6
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发表时间：
1999-09-30
影响因子：
9.8
通讯作者：
Beasley, TM
中科院分区：
文献类型：
--
作者：
Kelley, JM;Bond, LA;Beasley, TM
确定了1970年代从世界各地54个地点收集的存档土壤样品中钚同位素和Np-237的清单和组成，以提供区域基线，用于确认非沉降物钚和Np未来可能的环境投入。由于这项工作中使用的样本量很小（通常为1克），钚和钚浓度的不均匀性很容易识别，因此，我们能够确定，法国在南太平洋进行的试验中发现的南美洲的非典型碎片比以前设想的分布更广泛和均匀。根据我们的结果，我们得出结论，沉降物Np-237/（239）pU原子比在南半球（类似于0.35）比在北方半球（类似于0.47）通常较低。此外，Np-237/（PU）-P-239原子比对应的Pu-240/ Pu-239原子比更依赖于装置，因此更易变。鉴于样品不均匀性造成的可预测趋势，只有两个例外，这项工作的钚结果是完全一致的（并在几种情况下改善）以前报告的结果，这些相同的样品。然而，与先前用于解释这些结果的解释不同，我们建议用混合线而不是平均值来表示沉降物同位素特征，以更好地反映平流层沉降物清单相对于对流层沉降物清单的区域变化，并为此提供理论基础。最后，这项工作的Np结果构成了迄今为止报道的此类数据的最大单一汇编之一。(C)1999 Elsevier Science B. V.保留所有权利。
Inventories and compositions of Pu isotopes and Np-237 in archived soil samples collected in the 1970s from 54 locations around the world were determined to provide regional baselines for recognizing possible future environmental inputs of non-fallout Pu and Np. As sample sizes used in this work were small (typically 1 g), inhomogeneities in Pu and Np concentrations were easily recognizable and, as a result, we were able to determine that atypical debris in South America, from French testing in the South Pacific, is more widely and uniformly distributed than previously supposed. From our results we conclude that fallout Np-237/ (239)pU atom ratios are generally lower in the Southern Hemisphere (similar to 0.35) than in the Northern Hemisphere (similar to 0.47.) Moreover, Np-237/(PU)-P-239 atom ratios are more device-dependent, hence more variable, than counterpart Pu-240/ Pu-239 atom ratios. Given predictable trends caused by sample inhomogeneities, with only two exceptions, the Pu results of this work are entirely consistent with (and in several instances improve on) results previously reported for these same samples. However, unlike earlier interpretations used to explain these results, we recommend that fallout isotopic signatures be represented by mixing lines, rather than averages, to better reflect regional variations of stratospheric fallout inventories relative to tropospheric fallout inventories, and provide the theoretical basis for doing so. Finally, the Np results of this work constitute one of the largest single compilations of such data reported to date. (C) 1999 Elsevier Science B.V. All rights reserved.