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首页> 外文期刊>Environmental Science & Technology >Uranium Isotope Fractionation during the Anoxic Mobilization of Noncrystalline U(Ⅳ) by Ligand Complexation
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Uranium Isotope Fractionation during the Anoxic Mobilization of Noncrystalline U(Ⅳ) by Ligand Complexation

机译：通过配体络合的非折叠U（Ⅵ）的缺氧动员期间铀同位素分馏

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摘要

Uranium (U) isotopes are suggested as a tool to trace U reduction. However, noncrystalline U(Ⅳ), formed predominantly in near-surface environments, may be complexed and remobilized using ligands under anoxic conditions. This may cause additional U isotope fractionation and alter the signatures generated by U reduction. Here, we investigate the efficacy of noncrystalline U(Ⅳ) mobilization by ligand complexation and the associated U isotope fractionation. Noncrystalline U(Ⅳ) was produced via the reduction of U(Ⅵ) (400 μM) by Shewanella oneidensis MR-1 and was subsequently mobilized with EDTA (1 mM), citrate (1 mM), or bicarbonate (500 mM) in batch experiments. Complexation with all investigated ligands resulted in significant mobilization of U(Ⅳ) and led to an enrichment of ~(238)U in the mobilized fraction (δ~(238)U = 0.4-0.7 ‰ for EDTA; 0.3 ‰ for citrate; 0.2-0.3 ‰ for bicarbonate). For mobilization with bicarbonate, a Rayleigh approach was the most suitable isotope fractionation model, yielding a fractionation factor α of 1.00026-1.00036. Mobilization with EDTA could be modeled with equilibrium isotope fractionation (α: 1.00039-1.00049). The results show that U isotope fractionation associated with U(Ⅳ) mobilization under anoxic conditions is significant and needs to be considered when applying U isotopes in remediation monitoring or as a paleo-redox proxy.
机译：铀（U）同位素被建议作为追踪U降低的工具。然而，主要在近表面环境中形成的非折叠U（ⅳ）可以在缺氧条件下使用配体络合并重新繁成。这可能导致额外的U同位素分馏，并改变U降低产生的签名。在这里，我们研究了Noncrystalline U（Ⅳ）通过配体络合和相关的U同位素分馏的疗效。通过Shewanella Inidensis MR-1减少U（ⅵ）（400μm）而非晶体U（400μm），随后用EDTA（1mM），柠檬酸盐（1mM）或碳酸氢盐（500mm）的批量移动实验。所有研究的配体的络合导致U（Ⅵ）的显着动员，并导致〜（238）U中的浓缩（238）U中的动员级分（Δ〜（238）u = 0.4-0.7‰的EDTA; 0.3‰用于柠檬酸盐; 0.2 -0.3‰用于碳酸氢盐）。为了用碳酸氢盐调动，瑞利方法是最合适的同位素分级模型，产生1.00026-1.00036的分馏因子α。用EDTA的动员可以用平衡同位素分馏（α：1.00039-1.00049）进行建模。结果表明，在缺氧条件下与U（Ⅳ）动员相关的U同位素分馏是显着的，并且在将U同位素应用于修复监测或作为古氧化还原代理时需要考虑。

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