Distribution of uranium and thorium in dolomitic gravel fill and shale saprolite.
Distribution of uranium and thorium in dolomitic gravel fill and shale saprolite.
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DOI：
10.1016/j.jhazmat.2014.11.046
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发表时间：
2015-03
影响因子：
13.6
通讯作者：
D. Phillips;D. Watson
中科院分区：
文献类型：
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作者：
D. Phillips;D. Watson
本研究的目的是检查（1）铀和钍在长石砾石充填和页岩腐泥土中的分布，以及（2）在美国能源部橡树岭综合野外研究挑战（ORIFRC）现场，位于田纳西州东部橡树岭Y-12国家安全综合体以西，通过长石砾石与无定形基铝石沉淀，从酸性地下水中去除铀。介质反应性和可持续性是任何地下反应介质部署的技术问题。由于砾石被放置在地下，暴露于受污染的地下水超过20年，它提供了一个独特的机会，研究固体和水相的地球化学条件下的媒体后，这一长度的曝光。这项研究表明，白云岩砾石可以从高水平的Al 3+，Ca 2+，NO3-和SO 42-的酸性污染地下水中去除U。当地下水流过高pH值的碳酸盐砾石时，含U的无定形基铝石随着pH值的增加而沉淀。这是由于地下水与砾石接触时pH值从3.2增加到6.5。因此，碳酸盐砾石可以被认为是一种可能的处理介质，从酸性污染的地下水中去除和封存U和其他pH敏感的金属。碳酸盐砾石中钍的浓度也很高。钍一般表现出与U从表面向下到更深的腐泥土的反比关系。重晶石沉淀在浅腐岩直接下面的钙长石砾石从钡存在于酸性污染的地下水。
The objectives of this study were to examine (1) the distribution of U and Th in dolomitic gravel fill and shale saprolite, and (2) the removal of uranium from acidic groundwater by dolomitic gravel through precipitation with amorphous basaluminite at the U.S. DOE Oak Ridge Integrated Field Research Challenge (ORIFRC) field site west of the Oak Ridge Y-12 National Security Complex in East Tennessee. Media reactivity and sustainability are a technical concern with the deployment of any subsurface reactive media. Because the gravel was placed in the subsurface and exposed to contaminated groundwater for over 20 years, it provided a unique opportunity to study the solid and water phase geochemical conditions within the media after this length of exposure. This study illustrates that dolomite gravel can remove U from acidic contaminated groundwater with high levels of Al3+, Ca2+, NO3−, and SO42−over the long term. As the groundwater flows through high pH carbonate gravel, U containing amorphous basaluminite precipitates as the pH increases. This is due to an increase in groundwater pH from 3.2 to ∼6.5 as it comes in contact with the gravel. Therefore, carbonate gravel could be considered as a possible treatment medium for removal and sequestration of U and other pH sensitive metals from acidic contaminated groundwater. Thorium concentrations are also high in the carbonate gravel. Thorium generally shows an inverse relationship with U from the surface down into the deeper saprolite. Barite precipitated in the shallow saprolite directly below the dolomitic gravel from barium present in the acidic contaminated groundwater.