Solution and Microbial Controls on the Formation of Reduced U(IV) Species
Solution and Microbial Controls on the Formation of Reduced U(IV) Species
复制标题
DOI：
10.1021/es2014049
复制
发表时间：
2011-10-01
影响因子：
11.4
通讯作者：
Kemner, Kenneth M.
中科院分区：
文献类型：
--
作者：
Boyanov, Maxim I.;Fletcher, Kelly E.;Kemner, Kenneth M.
由于直接或间接的微生物活动，目前正在探索将U（VI）还原为U（IV），用于地下U羽流的原位修复，假设U（IV）溶解度由低溶解度矿物晶质铀矿（U（IV）-二氧化物）控制。然而，最近从生物刺激现场沉积物中的U的特征，以及实验室U（VI）生物还原研究，报告的U（IV）的形成缺乏铀晶质铀矿的U=O（2）=U配位，这表明，相以外的晶质铀矿可能是控制U（IV）在环境中的溶解度与复杂的表面和配位体。为了确定对这种非晶质铀石U（IV）物种形成的控制，目前的工作研究了（1）五种革兰氏阳性脱硫杆菌菌株，（2）革兰氏阴性细菌Anaeromyxamelladehalogenans 2CP-C和Shewanella putrefaciens CN 32，以及（3）化学还原的9，10-蒽氢醌-2，6-二磺酸盐（AH（2）QDS，可溶性还原剂）对碳酸盐络合的U（VI）的还原。此外，0.3 mM溶解的磷酸盐对U（IV）物种形成的影响进行了探讨。扩展的X射线吸收精细结构（EXAFS）光谱分析表明，除了磷酸盐导致形成nonuraninite，磷酸盐络合的U（IV）物种，独立的生物或非生物模式的U（VI）的还原。在无磷培养基中，U（VI）还原脱硫杆菌属。AH（2）QDS还原产生非晶质铀矿，碳酸盐络合的U（IV）物种，而Anaeromyxalidae或Shewanella还原产生纳米微粒晶质铀矿。这些发现表明，革兰氏阳性脱硫杆菌菌株和革兰氏阴性厌氧黏菌和希瓦氏菌属物种使用不同的机制，以减少U（VI）。
Reduction of U(VI) to U(IV) as the result of direct or indirect microbial activity is currently being explored for in situ remediation of subsurface U plumes, under the assumption that U(IV) solubility is controlled by the low-solubility mineral uraninite (U(IV)-dioxide). However, recent characterizations of U in sediments from biostimulated field sites, as well as laboratory U(VI) bioreduction studies, report on the formation of U(IV) species that lack the U=O(2)=U coordination of uraninite, suggesting that phases other than uraninite may be controlling U(IV) solubility in environments with complexing surfaces and ligands. To determine the controls on the formation of such nonuraninite U(IV) species, the current work studied the reduction of carbonate-complexed U(VI) by (1) five Gram-positive Desulfitobacterium strains, (2) the Gram-negative bacteria Anaeromyxobacter dehalogenans 2CP-C and Shewanella putrefaciens CN32, and (3) chemically reduced 9,10-anthrahydroquinone-2,6-disulfonate (AH(2)QDS, a soluble reductant). Further, the effects of 0.3 mM dissolved phosphate on U(IV) species formation were explored. Extended X-ray absorption fine structure (EXAFS) spectroscopy analysis demonstrated that the addition of phosphate causes the formation of a nonuraninite, phosphate-complexed U(IV) species, independent of the biological or abiotic mode of U(VI) reduction. In phosphate-free medium, U(VI) reduction by Desulfitobacterium spp. and by AH(2)QDS resulted in nonuraninite, carbonate-complexed U(IV) species, whereas reduction by Anaeromyxobacter or Shewanella yielded nanoparticulate uraninite. These findings suggest that the Gram-positive Desulfitobacterium strains and the Gram-negative Anaeromyxobacter and Shewanella species use distinct mechanisms to reduce U(VI).