Technetium reduction in sediments of a shallow aquifer exhibiting dissimilatory iron reduction potential.
Technetium reduction in sediments of a shallow aquifer exhibiting dissimilatory iron reduction potential.
复制标题
浅层含水层沉积物中的锝还原表现出异化铁还原潜力。
DOI：
10.1016/j.femsec.2003.08.016
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发表时间：
2004
影响因子：
4.2
通讯作者：
E. Roden
中科院分区：
文献类型：
--
作者：
R. Wildung;S. W. Li;Christopher J. Murray;K. Krupka;YuLong Xie;Nancy J. Hess;E. Roden
高锝酸根离子[Tc（VII）O 4 −]的还原率是在美国大西洋沿岸平原一个浅桑迪含水层的岩芯样品中测定的。含水层的溶解氧含量一般较低（<1 mg L−1），由物理化学性质明显不同的晚更新世沉积物组成。热力学计算，X-射线吸收光谱和统计分析被用来建立主导的还原机制，限制Tc的溶解度，和氧化态，和沉积物还原产物的形态。沉积物之间的Tc（VII）减少的程度显着不同（平衡10天后从0%到100%不等），与低溶解度Tc（IV）水合氧化物的主要固相还原产物。沉积物中的主要电子供体被证明是（0.5 M HCl可提取）Fe（II）。沉积物Fe（II）/Tc（VII）浓度>4.3通常足以完全还原添加的Tc（VII）[1-2.5 μmol（干重）]。沉积物）g-1]。在这些Fe（II）的浓度，Tc（VII）的还原率超过了以前观察到的Fe（II）介导的减少孤立的固体地质或生物起源，这表明沉积物Fe（II）是更具反应性和/或电子穿梭发挥了作用，在沉积物Tc（VII）的还原过程。在掩埋的泥炭，过量的Fe（II）没有导致从溶液中完全除去Tc，也许是因为有机络合的Tc（IV）限制形成的Tc（IV）水合氧化物。在Fe（II）/Tc（VII）浓度<1.1的一些砂中，存在直接酶促还原Tc（VII）的推定证据。此外，有机电子供体（乙酸，乳酸）导致微生物减少（高达35%）的Fe（III）和相应的增加，可提取的Fe（II）在砂，表现出最低的初始Tc（VII）的减少和最高的水力传导率，这表明加速微生物减少Fe（III）可以提供一个可行的手段衰减移动的Tc（VII）在这种类型的沉积物系统。
Pertechnetate ion [Tc(VII)O4−] reduction rate was determined in core samples from a shallow sandy aquifer located on the US Atlantic Coastal Plain. The aquifer is generally low in dissolved O2(<1 mg L−1) and composed of weakly indurated late Pleistocene sediments differing markedly in physicochemical properties. Thermodynamic calculations, X-ray absorption spectroscopy and statistical analyses were used to establish the dominant reduction mechanisms, constraints on Tc solubility, and the oxidation state, and speciation of sediment reduction products. The extent of Tc(VII) reduction differed markedly between sediments (ranging from 0% to 100% after 10 days of equilibration), with low solubility Tc(IV) hydrous oxide the major solid phase reduction product. The dominant electron donor in the sediments proved to be (0.5 M HCl extractable) Fe(II). Sediment Fe(II)/Tc(VII) concentrations >4.3 were generally sufficient for complete reduction of Tc(VII) added [1–2.5 μmol (dry wt. sediment) g−1]. At these Fe(II) concentrations, the Tc (VII) reduction rate exceeded that observed previously for Fe(II)-mediated reduction on isolated solids of geologic or biogenic origin, suggesting that sediment Fe(II) was either more reactive and/or that electron shuttles played a role in sediment Tc(VII) reduction processes. In buried peats, Fe(II) in excess did not result in complete removal of Tc from solution, perhaps because organic complexation of Tc(IV) limited formation of the Tc(IV) hydrous oxide. In some sands exhibiting Fe(II)/Tc(VII) concentrations <1.1, there was presumptive evidence for direct enzymatic reduction of Tc(VII). Addition of organic electron donors (acetate, lactate) resulted in microbial reduction of (up to 35%) Fe(III) and corresponding increases in extractable Fe(II) in sands that exhibited lowest initial Tc(VII) reduction and highest hydraulic conductivities, suggesting that accelerated microbial reduction of Fe(III) could offer a viable means of attenuating mobile Tc(VII) in this type of sediment system.