Isotopic and Geochemical Tracers for U(VI) Reduction and U Mobility at an in Situ Recovery U Mine
Isotopic and Geochemical Tracers for U(VI) Reduction and U Mobility at an in Situ Recovery U Mine
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DOI：
10.1021/acs.est.5b00701
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发表时间：
2015-05-19
影响因子：
11.4
通讯作者：
Maher, Kate
中科院分区：
文献类型：
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作者：
Basu, Anirban;Brown, Shaun T.;Maher, Kate
原地回收（ISR）铀（U）开采通过氧化溶解滚前铀矿床中的U，使U以其氧化的六价形式（U（VI））流动。ISR矿山开采后残留U（VI）的自然衰减是一种潜在的修复策略。检测和监测自然发生的还原性地下环境对于成功实施这一补救计划是重要的。我们使用同位素示踪剂U-238/U-235（Δ U-238）、U-234/U-238活度比和S-34/S-32（Δ S-34），以及从位于卷前铀存款内、内梯度和下梯度的32口威尔斯井中收集的铀矿和地下水的地球化学测量，来检测美国德克萨斯州罗西塔ISR矿区的U（VI）还原和U迁移率。Rosita地下水中的U-238三角洲从+0.61 ‰变化到-2.49 ‰，在下坡威尔斯井中有降低U-238三角洲的趋势。铀（六价）浓度和铀-238增量的同时下降，其中δ为0.48千分之+/- 0.08千分之，这表明自然发生的还原环境有利于铀（六价）的减少。此外，特征U-234/U-238活度比和S-34值也可用于追踪采矿结束后矿区地下水的流动性。这些结果支持在Rosita和其他类似ISR采矿场使用基于U同位素的U（VI）自然衰减检测。
In situ recovery (ISR) uranium (U) mining mobilizes U in its oxidized hexavalent form (U(VI)) by oxidative dissolution of U from the roll-front U deposits. Postmining natural attenuation of residual U(VI) at ISR mines is a potential remediation strategy. Detection and monitoring of naturally occurring reducing subsurface environments are important for successful implementation of this remediation scheme. We used the isotopic tracers U-238/U-235 (delta U-238), U-234/U-238 activity ratio, and S-34/S-32 (delta S-34), and geochemical measurements of U ore and groundwater collected from 32 wells located within, upgradient, and downgradient of a roll-front U deposit to detect U(VI) reduction and U mobility at an ISR mining site at Rosita, TX, USA. The delta U-238 in Rosita groundwater varies from +0.61 parts per thousand to -2.49 parts per thousand, with a trend toward lower delta U-238 in downgradient wells. The concurrent decrease in U(VI) concentration and delta U-238 with an epsilon of 0.48 parts per thousand +/- 0.08 parts per thousand is indicative of naturally occurring reducing environments conducive to U(VI) reduction. Additionally, characteristic U-234/U-238 activity ratio and delta S-34 values may also be used to trace the mobility of the ore zone groundwater after mining has ended. These results support the use of U isotope-based detection of natural attenuation of U(VI) at Rosita and other similar ISR mining sites.