Plutonium Desorption from Nuclear Melt Glass-Derived Colloids and Implications for Migration at the Nevada National Security Site, USA
Plutonium Desorption from Nuclear Melt Glass-Derived Colloids and Implications for Migration at the Nevada National Security Site, USA
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DOI：
10.1021/acs.est.9b03956
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发表时间：
2019-11-05
影响因子：
11.4
通讯作者：
Zavarin, Mavrik
中科院分区：
文献类型：
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作者：
Joseph, Claudia;Balboni, Enrica;Zavarin, Mavrik
在内华达州国家安全地点（NNSS）观察到低水平钚的迁移，并将其归因于胶体。为了更好地理解该地点胶体促进运输的机制，我们对NNSS核熔融玻璃的热液蚀变产生的矿物胶体悬浮液进行了流动池解吸实验，这些矿物胶体悬浮液是核试验留下的残留物质。使用了三种不同的胶体悬浮液：（1）在140 °C下来自核熔融玻璃的水热蚀变的胶体材料;（2）在200 °C下;和（3）在室温下吸附到SWy-1蒙脱石上的钚。140 °C的样品仅含有蒙脱石，而沸石和其他相存在于200 °C的样品中。总的来说，更多的钚从140 °C的胶体中解吸出来（约100克）。9-16%）比200 °C胶体（约。4-8%）。此外，在4.5天流动池实验结束时，140 °C胶体和PU-蒙脱石胶体的解吸速率相似，而200 °C胶体的解吸速率低达一个数量级。我们认为，在200 °C下水热改变的沸石和粘土的形成可能导致钚与胶体的更稳定的缔合，从而导致较低的解吸速率。这可能会引起更广泛的胶体促进运输，并有助于解释为什么在核爆炸数十年后，从其原始来源向下梯度发现痕量钚。有趣的是，在铯（钚的共污染物）的情况下，在140和200 °C的胶体之间没有观察到差异。这反映了铯和钚的吸附/解吸行为（电荷，阳离子大小）之间的内在差异，并表明Cs的吸附机制（阳离子交换）是没有类似的胶体形成温度的影响。
The migration of low levels of plutonium has been observed at the Nevada National Security Site (NNSS) and attributed to colloids. To better understand the mechanism(s) of colloid-facilitated transport at this site, we performed flow cell desorption experiments with mineral colloid suspensions produced by hydrothermal alteration of NNSS nuclear melt glass, residual material left behind from nuclear testing. Three different colloid suspensions were used: (1) colloidal material from hydrothermal alteration of nuclear melt glass at 140 °C; (2) at 200 °C; and (3) plutonium sorbed to SWy-1 montmorillonite at room temperature. The 140 °C sample contained only montmorillonite, while zeolite and other phases were present in the 200 °C sample. Overall, more plutonium was desorbed from the 140 °C colloids (ca. 9–16%) than from the 200 °C colloids (ca. 4–8%). Furthermore, at the end of the 4.5 day flow cell experiments, the desorption rates for the 140 °C colloids and the Pu–montmorillonite colloids were similar while the desorption rates from the 200 °C colloids were up to an order of magnitude lower. We posit that the formation of zeolites and clays hydrothermally altered at 200 °C may lead to a more stable association of plutonium with colloids, resulting in lower desorption rates. This may give rise to more extensive colloid-facilitated transport and help explain why trace levels of plutonium are found downgradient from their original source decades after a nuclear detonation. Interestingly, in the case of cesium (a co-contaminant of plutonium), no difference was observed between the 140 and 200 °C colloids. This reflects intrinsic differences between cesium and plutonium sorption/desorption behavior (charge, cation size) and suggests that the Cs sorption mechanism (cation exchange) is not similarly affected by colloid formation temperature.