The effect of aging on the stability of microbially-reduced uranium in natural sediments.
The effect of aging on the stability of microbially-reduced uranium in natural sediments.
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DOI：
10.1021/acs.est.8b07023
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发表时间：
2019-11
影响因子：
11.4
通讯作者：
L. Loreggian;A. Novotny;S. Bretagne;B. Bártová;Yuheng Wang;R. Bernier-Latmani
中科院分区：
文献类型：
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作者：
L. Loreggian;A. Novotny;S. Bretagne;B. Bártová;Yuheng Wang;R. Bernier-Latmani
还原固定铀已被探索作为一种修复策略的U污染的地下。通过微生物过程的原位生物刺激，六价铀被还原为固定在沉积物中的溶解度较低的四价物质。虽然矿物晶质铀矿（UO 2）最初被认为是生物还原的主要产物，但非晶态U（IV）物种（NCU（IV））在环境中被发现是丰富的，尽管它们对氧化和再活化更敏感。然而，最近有人提出，通过老化，NCU（IV）可能转化为二氧化铀，这可能会提高还原铀库的稳定性。在这项研究中，我们进行了柱实验，以产生NCU（IV）物种在自然沉积物模仿生物修复过程中的环境条件。生物还原沉积物检索从列和窝藏NCU（IV），在缺氧条件下的静态微观世界中孵育，允许系统监测的U协调的X-射线吸收光谱（XAS）超过12个月。XAS表明，在调查的条件下，U（IV）的形态不随时间而变化。因此，由于NCU（IV）是沉积物中的主要物种，即使经过12个月的老化期，生物还原的U（IV）物种仍然容易在水相中氧化和再活化。
Reductive immobilization of uranium has been explored as a remediation strategy for the U-contaminated subsurface. Via the in-situ biostimulation of microbial processes, hexavalent U is reduced to less soluble tetravalent species which are immobilized within the sediments. Although the mineral uraninite (UO2) was initially considered the dominant product of biological reduction, non-crystalline U(IV) species (NCU(IV)) are found to be abundant in the environment, despite their greater susceptibility to oxidation and remobilization. However, it has been recently proposed that, through aging, NCU(IV) might transform into UO2, which would potentially enhance the stability of the reduced U pool. In this study, we performed column experiments to produce NCU(IV) species in a natural sediment mimicking the environmental conditions during bioremediation. Bioreduced sediments retrieved from the columns and harboring NCU(IV), were incubated in static microcosms under anoxic conditions, to allow the systematic monitoring of U coordination by X-ray absorption spectroscopy (XAS) over 12 months. XAS revealed that, under the investigated conditions, the speciation of U(IV) does not change over time. Thus, because NCU(IV) is the dominant species in the sediments, bioreduced U(IV) species remain vulnerable to oxidation and remobilization in the aqueous phase even after a 12-month aging period.