Fate of tetravalent uranium under reducing conditions

四价铀在还原条件下的归宿

• 批准号: 283167820
• 负责人: Professor Dr. Stefan Weyer, Ph.D.
• 金额: --
• 依托单位: Institut für Mineralogie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/283167820?language=en
• 关键词: Fate; tetravalent; uranium; under; reducing

The stimulation of microbial reduction of the soluble hexavalent U [U(VI)] to sparingly soluble tetravalent U [U(IV)] has been exploited as an in-situ strategy for the immobilization of uranium in contaminated aquifers. The success of this strategy rests on the low solubility of U(IV) phases that are formed as the product of microbial reduction. Recent research efforts have shown that these reduction products do not only consist of stable crystalline mineral phases such as uraninite, but are also associated with biomass such as non-crystalline U(IV) species. While the thermodynamic properties and the mechanisms and rates of mobilization of such biomass-associated U(IV) are unknown, experimental evidence seems to indicate that they are more mobile and may impact the efficacy of uranium bioremediation. Additionally, the identification of U(IV)-bearing colloids composed primarily of organic matter and iron in a wetland, suggests the importance of organic ligands in mobilizing U(IV). Finally, it was previously shown that biogenic ligands can accelerate the dissolution of crystalline uraninite and we suggest that they may also promote the mobilization of non-crystalline U(IV). In this context, the proposed work will address the kinetics and mechanisms of the mobilization of non-crystalline U(IV) by biogenic ligands and reduced humic substances and how they compare to those of uraninite. We will also probe the impact of ligands on the potential transformation of non-crystalline U(IV) to crystalline U(IV) species since this process is expected to impact the stability of U(IV). In order to establish tools to identify these processes in complex natural systems, we investigate the suitability of uranium isotope fractionation as a proxy for the mechanisms of U reduction, of mobilization of non-crystalline U(IV) induced e.g. by complexation with organic ligands, as well as of potential transformation of non-crystalline to crystalline U(IV). We propose that the quantification of isotope fractionation may also be used for the elucidation of the molecular mechanisms of these processes in field and microcosm studies. Finally, we will develop quantitative reactive transport models including kinetic processes and isotope fractionation that will be tested against column experiments that approximate the complexity of field scale uranium reduction and re-mobilization. This model will not only provide a useful tool for predicting uranium transport under reducing conditions, but also aide the interpretation of isotope fractionation along the flow path.The results of this research will deliver new insights into the mobility of U from underground sources of U contamination such as leaching from mine tailings or from unexploded depleted uranium ammunition in soil. We furthermore expect them, to provide valuable information that may be used to adjust the design of remediation strategies as well as to evaluate their sustainability.

刺激微生物还原的可溶性六价U [U（VI）]微溶四价U [U（IV）]已被开发作为一种原位战略的铀污染含水层中的固定。这种策略的成功依赖于作为微生物还原产物形成的U（IV）相的低溶解度。最近的研究工作表明，这些还原产物不仅包括稳定的结晶矿物相，如晶质铀矿，但也与生物质，如非结晶U（IV）物种。虽然这种生物质相关的U（IV）的热力学性质和机制和动员率是未知的，但实验证据似乎表明，它们更移动的，可能会影响铀生物修复的功效。此外，识别的U（IV）-轴承胶体主要由有机质和铁在湿地中，表明有机配体在动员U（IV）的重要性。最后，它以前表明，生物配体可以加速溶解的结晶晶质铀矿，我们认为，他们也可能促进非结晶U（IV）的动员。在这种情况下，拟议的工作将解决的动力学和机制的动员非结晶U（IV）的生物配体和还原腐殖物质，以及它们如何比较的晶质铀矿。我们还将探讨配体对非结晶U（IV）到结晶U（IV）物种的潜在转化的影响，因为这个过程预计会影响U（IV）的稳定性。为了建立工具，以确定这些过程在复杂的自然系统中，我们调查的铀同位素分馏作为一个代理的机制，U还原，动员的非结晶U（IV）诱导，例如，通过与有机配体络合，以及潜在的非结晶转化为结晶U（IV）的适用性。我们建议，同位素分馏的定量也可用于阐明这些过程的分子机制，在现场和微观研究。最后，我们将开发定量反应传输模型，包括动力学过程和同位素分馏，将测试对柱实验，近似的复杂性，现场规模的铀还原和再动员。该模型不仅为预测还原条件下铀的迁移提供了一个有用的工具，而且有助于解释铀同位素沿流路的沿着分馏，其研究结果将为地下铀污染源（如尾矿浸出或未爆炸的贫铀弹在土壤中的迁移）提供新的认识。我们还希望他们提供有价值的信息，可用于调整补救策略的设计，以及评估其可持续性。

项目成果

Uranium Isotope Fractionation during the Anoxic Mobilization of Noncrystalline U(IV) by Ligand Complexation.

配体络合非晶 U(IV) 缺氧迁移过程中的铀同位素分馏

• DOI: 10.1021/acs.est.0c08623
• 期刊: Environmental science & technology
• 影响因子: 11.4
• 作者: Roebbert;Yvonne;Rosendahl;Chris Daniel;Ashley;Schippers;Bernier- Latmani;Rizlan;Stefan
• 通讯作者: Stefan

The effect of aging on the stability of microbially-reduced uranium in natural sediments.

• DOI: 10.1021/acs.est.8b07023
• 发表时间: 2019-11
• 期刊: Environmental science & technology
• 影响因子: 11.4
• 作者: L. Loreggian;A. Novotny;S. Bretagne;B. Bártová;Yuheng Wang;R. Bernier-Latmani