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Complexation by Organic Matter Controls Uranium Mobility in Anoxic Sediments.
Environmental Science & Technology ( IF 11.4 ) Pub Date : 2020-01-15 , DOI: 10.1021/acs.est.9b04741
Sharon E Bone 1 , John Cliff 2 , Karrie Weaver 3 , Christopher J Takacs 1 , Scott Roycroft 3 , Scott Fendorf 3 , John R Bargar 1
Affiliation  

Uranium contamination threatens the availability of safe and clean drinking water globally. This toxic element occurs both naturally and as a result of mining and ore-processing in alluvial sediments, where it accumulates as tetravalent U [U(IV)], a form once considered largely immobile. Changing hydrologic and geochemical conditions cause U to be released into groundwater. Knowledge of the chemical form(s) of U(IV) is essential to understand the release mechanism, yet the relevant U(IV) species are poorly characterized. There is growing belief that natural organic matter (OM) binds U(IV) and mediates its fate in the subsurface. In this work, we combined nanoscale imaging (nano secondary ion mass spectrometry and scanning transmission X-ray microscopy) with a density-based fractionation approach to physically and microscopically isolate organic and mineral matter from alluvial sediments contaminated with uranium. We identified two populations of U (dominantly +IV) in anoxic sediments. Uranium was retained on OM and adsorbed to particulate organic carbon, comprising both microbial and plant material. Surprisingly, U was also adsorbed to clay minerals and OM-coated clay minerals. The dominance of OM-associated U provides a framework to understand U mobility in the shallow subsurface, and, in particular, emphasizes roles for desorption and colloid formation in its mobilization.

中文翻译:

有机物络合可控制缺氧沉积物中的铀迁移率。

铀污染威胁着全球安全和清洁饮用水的供应。这种有毒元素既天然存在,又是冲积沉积物中采矿和矿石加工的结果,它以四价U [U(IV)]的形式积累,这种形式曾经被认为是不可移动的。变化的水文和地球化学条件导致U释放到地下水中。了解U(IV)的化学形式对于了解释放机理至关重要,但是相关的U(IV)种类的特征不明确。人们越来越相信天然有机物(OM)会结合U(IV)并介导其在地下的命运。在这项工作中,我们将纳米级成像(纳米次级离子质谱和扫描透射X射线显微镜)与基于密度的分馏方法相结合,以物理方式和显微镜方式从被铀污染的冲积沉积物中分离出有机物和矿物质。我们在缺氧沉积物中确定了两个种群的U(主要为+ IV)。铀保留在OM上并吸附到包括微生物和植物材料的颗粒有机碳上。出乎意料的是,U也被吸附到粘土矿物和OM涂覆的粘土矿物上。与OM相关的U的主导地位为理解U在浅层地下的流动性提供了框架,特别是强调了在其动员中解吸和胶体形成的作用。我们在缺氧沉积物中确定了两个种群的U(主要为+ IV)。铀保留在OM上并吸附到包括微生物和植物材料的颗粒有机碳上。出乎意料的是,U也被吸附到粘土矿物和OM涂覆的粘土矿物上。与OM相关的U的主导地位为理解U在浅层地下的流动性提供了框架,特别是强调了在其动员中解吸和胶体形成的作用。我们在缺氧沉积物中确定了两个种群的U(主要为+ IV)。铀保留在OM上并吸附到包括微生物和植物材料的颗粒有机碳上。出乎意料的是,U也被吸附到粘土矿物和OM涂覆的粘土矿物上。与OM相关的U的主导地位为理解U在浅层地下的流动性提供了框架,特别是强调了在其动员中解吸和胶体形成的作用。
更新日期:2020-01-16
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