Bioreduction Behavior of U(VI) Sorbed to Sediments
Bioreduction Behavior of U(VI) Sorbed to Sediments
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DOI：
10.1080/01490451003761137
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发表时间：
2011-01-01
影响因子：
2.3
通讯作者：
Morris, Katherine
中科院分区：
文献类型：
--
作者：
Begg, James D. C.;Burke, Ian T.;Morris, Katherine
众所周知，微生物介导的还原可以通过形成难溶的U（IV）氧化物导致U(VI)（aq）从溶液中去除；然而，已经与矿物表面相关联的U（VI）的命运就不太清楚了。在这里，我们描述了氧吸附和厌氧微生物实验的结果，以检查在微生物介导的生物还原过程中吸附的U（VI）的命运。微观实验中含有代表英国邓雷核设施的沉积物。在氧吸附实验中，当用0.2 mmol l-1乙二胺四乙酸（EDTA）对地下水进行修饰时，U（VI）在人工地下水中被快速而完全地吸收。EDTA是一种用于核燃料循环操作的络合配体。而在10 mmol l-1碳酸氢盐处理的地下水中，U（VI）的吸收不完全。x射线吸附光谱分析表明，在这些含氧样品中，U以U（VI）的形式存在。在U（VI）标记的沉积物厌氧培养120天后，微生物介导的Fe(III)-和SO42-还原条件已经形成，XAS数据显示铀被还原为U（IV）。对未修改的地下水系统的进一步研究表明，在氧系统以U（VI）吸附为主的情况下，吸附U（VI）的还原需要活跃的微生物种群，并且在形成了强大的铁和硫酸盐还原条件之后才会发生。生物还原沉积物的微生物群落分析显示，与氧化沉积物相比，生物还原沉积物的群落发生了变化，与促进U（VI）还原的Geobacter和Clostridium物种密切相关，占主导地位。总的来说，在氧化条件下通过吸附去除溶液中的U（VI）在未修饰和EDTA修饰的体系中占主导地位。在所有系统中，生物还原导致固体中U（IV）的形成。
It is well known that microbially mediated reduction can result in the removal of U(VI)(aq) from solution by forming poorly soluble U(IV) oxides; however, the fate of U(VI) already associated with mineral surfaces is less clear. Here we describe results from both oxic adsorption and anaerobic microcosm experiments to examine the fate of sorbed U(VI) during microbially mediated bioreduction. The microcosm experiments contained sediment representative of the nuclear facility at Dounreay, UK. In oxic adsorption experiments, uptake of U(VI) was rapid and complete from artificial groundwater and where groundwater was amended with 0.2 mmol l-1 ethylenediaminetetraacetic acid (EDTA) a complexing ligand used in nuclear fuel cycle operations. By contrast, uptake of U(VI) was incomplete in groundwaters amended with 10 mmol l-1 bicarbonate. Analysis of sediments using X-ray adsorption spectroscopy showed that in these oxic samples, U was present as U(VI). After anaerobic incubation of U(VI) labelled sediments for 120 days, microbially mediated Fe(III)- and SO42-- reducing conditions had developed and XAS data showed uranium was reduced to U(IV). Further investigation of the unamended groundwater systems, where oxic systems were dominated by U(VI) sorption, showed that reduction of sorbed U(VI) required an active microbial population and occurred after robust iron- and sulfate- reducing conditions had developed. Microbial community analysis of the bioreduced sediment showed a community shift compared to the oxic sediment with close relatives of Geobacter and Clostridium species, which are known to facilitate U(VI) reduction, dominating. Overall, efficient U(VI) removal from solution by adsorption under oxic conditions dominated in unamended and EDTA amended systems. In all systems bioreduction resulted in the formation of U(IV) in solids.