Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States.
Environ Sci Technol. 2011 Feb 1;45(3):951-7. doi: 10.1021/es1027647. Epub 2011 Jan 6.
The fate of pertechnetate ((99)Tc(VII)O(4)(-)) during bioreduction was investigated in the presence of 2-line ferrihydrite (Fh) and various dissimilatory metal reducing bacteria (DMRB) (Geobacter, Anaeromyxobacter, Shewanella) in comparison with TcO(4)(-) bioreduction in the absence of Fh. In the presence of Fh, Tc was present primarily as a fine-grained Tc(IV)/Fe precipitate that was distinct from the Tc(IV)O(2)·nH(2)O solids produced by direct biological Tc(VII) reduction. Aqueous Tc concentrations (<0.2 μm) in the bioreduced Fh suspensions (1.7 to 3.2 × 10(-9) mol L(-1)) were over 1 order of magnitude lower than when TcO(4)(-) was biologically reduced in the absence of Fh (4.0 × 10(-8) to 1.0 × 10(-7) mol L(-1)). EXAFS analyses of the bioreduced Fh-Tc products were consistent with variable chain length Tc-O octahedra bonded to Fe-O octahedra associated with the surface of the residual or secondary Fe(III) oxide. In contrast, biogenic TcO(2)·nH(2)O had significantly more Tc-Tc second neighbors and a distinct long-range order consistent with small particle polymers of TcO(2). In Fe-rich subsurface sediments, the reduction of Tc(VII) by Fe(II) may predominate over direct microbial pathways, potentially leading to lower concentrations of aqueous (99)Tc(IV).
在存在 2 线水铁矿 (Fh) 和各种异化金属还原菌 (DMRB)（地杆菌、厌氧粘细菌、希瓦氏菌）的情况下，研究了高锝酸盐 ((99)Tc(VII)O(4)(-)) 在生物还原过程中的命运，并与不存在 Fh 时的 TcO(4)(-) 生物还原进行了比较。在 Fh 的存在下，Tc 主要以细颗粒 Tc(IV)/Fe 沉淀物的形式存在，与直接生物 Tc(VII)还原产生的 Tc(IV)O(2)·nH(2)O 固体明显不同。在生物还原的 Fh 悬浮液中（1.7 至 3.2×10(-9)mol L(-1))，Tc 的水相浓度（<0.2μm）比在不存在 Fh 时 TcO(4)(-) 的生物还原低 1 个数量级（4.0×10(-8)至 1.0×10(-7)mol L(-1))。对生物还原的 Fh-Tc 产物的 EXAFS 分析表明，Tc-O 八面体与与残余或次生 Fe(III)氧化物表面相关的 Fe-O 八面体之间存在可变链长 Tc-O 八面体。相比之下，生物生成的 TcO(2)·nH(2)O 具有更多的 Tc-Tc 第二近邻和明显的长程有序性，与 TcO(2)的小颗粒聚合物一致。在富铁的地下沉积物中，Tc(VII)的还原可能由 Fe(II)主导，而不是直接的微生物途径，这可能导致水相 (99)Tc(IV)的浓度降低。
