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首页> 外文期刊>Environmental Science & Technology >Influences Of Organic Carbon Supply Rate On Uranium Bioreduction In Initially Oxidizing, Contaminated Sediment
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Influences Of Organic Carbon Supply Rate On Uranium Bioreduction In Initially Oxidizing, Contaminated Sediment

机译：有机碳供应速率对初始氧化，污染沉积物中铀生物还原的影响

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Remediation of uranium-contaminated sediments through in situ stimulation of bioreduction to insoluble UO_2 is a potential treatment strategy under active investigation. Previously, we found that newly reduced U(IV) can be reoxidized under reducing conditions sustained by a continuous supply of organic carbon (OC) because of residual reactive Fe(lll) and enhanced U(VI) solubility through complexation with carbonate generated through OC oxidation. That finding motivated this investigation directed at identifying a range of OC supply rates that is optimal for establishing U bioreduction and immobilization in initially oxidizing sediments. The effects of OC supply rate, from 0 to 580 mmol of OC (kg of sediment)~(-1) year~(-1), and OC form (lactate and acetate) on U bioreduction were tested in flow-through columns containing U-contaminated sediments. An intermediate supply rate on the order of 150 mmol of OC (kg of sediment)~(-1) year~(-1) was determined to be most effective at immobilizing U. At lower OC supply rates, U bioreduction was not achieved, and U(VI) solubility was enhanced by complexation with carbonate (from OC oxidation). At the highest OC supply rate, the resulting highly carbonate-enriched solutions also supported elevated levels of U(VI), even though strongly reducing conditions were established. Lactate and acetate were found to have very similar geochemical impacts on effluent U concentrations (and other measured chemical species), when compared at equivalent OC supply rates. While the catalysts of U(VI) reduction to U(IV) are presumably bacteria, the composition of the bacterial community, the Fe-reducing community, and the sulfate-reducing community had no direct relationship with effluent U concentrations. The OC supply rate has competing effects of driving reduction of U(VI) to low-solubility U(IV) solids, as well as causing formation of highly soluble U(VI)-carbonato complexes. These offsetting influences will require careful control of OC supply rates in order to optimize bioreduction-based U stabilization.
机译：通过原位刺激生物还原成不溶性UO_2来修复铀污染的沉积物是一项积极研究的潜在处理策略。以前，我们发现新还原的U（IV）在还原条件下可通过连续供应有机碳（OC）持续还原，这是因为残留的反应性Fe（III）和通过与OC生成的碳酸盐络合而提高的U（VI）溶解度氧化。这一发现激励了这项研究，旨在确定最适合于在初始氧化沉积物中建立U生物还原和固定作用的OC供应速率范围。在流通池中测试了OC供给速率，0至580 mmol OC（kg沉淀物）〜（-1）年〜（-1）和OC形态（乳酸和乙酸盐）对U生物还原的影响。受U污染的沉积物。确定了以150 mmol OC（kg沉积物）〜（-1）年〜（-1）为量级的中间供应速率最有效地固定了U。在较低的OC供应速率下，未实现U生物还原， U（VI）的溶解度通过与碳酸盐（来自OC氧化）的络合而增强。以最高的OC供应速率，即使建立了强烈的还原条件，所得到的高度富含碳酸盐的溶液也支持提高U（VI）的水平。当以等效的超临界进给量进行比较时，发现乳酸和乙酸盐对废水中的铀浓度（和其他测得的化学物质）具有非常相似的地球化学影响。虽然U（VI）还原为U（IV）的催化剂可能是细菌，但细菌群落，Fe还原群落和硫酸盐还原群落的组成与污水中的U浓度没有直接关系。 OC的供应速率具有相互竞争的作用，促使U（VI）还原为低溶解度的U（IV）固体，并导致形成高溶解度的U（VI）-碳酸盐络合物。这些抵消性影响将需要仔细控制OC的供应速率，以优化基于生物还原的U稳定性。

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