Interactions between microbial iron reduction and metal geochemistry: Effect of redox cycling on transition metal speciation in iron bearing sediments
Interactions between microbial iron reduction and metal geochemistry: Effect of redox cycling on transition metal speciation in iron bearing sediments
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DOI：
10.1021/es051778t
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发表时间：
2006-03-15
影响因子：
11.4
通讯作者：
Coby, AJ
中科院分区：
文献类型：
--
作者：
Cooper, DC;Picardal, FF;Coby, AJ
微生物铁还原是一个重要的生物地球化学过程，通过直接和间接的机制影响沉积物中的金属地球化学。对于含有吸附二价金属的Fe(III)（氢）氧化物，最近的报道表明：(1)针铁矿/水合铁混合物的微生物还原优先去除水合铁，(2)该过程可以将先前吸附的Zn（II）合并成不溶于0.5 M HCl的自生结晶相，(3)这个新相可能是针铁矿，(4)不可还原矿物的存在可以抑制这种转变。该研究表明，一系列被吸附的过渡金属可以选择性地隔离到0.5 M HCl不溶相中，并且该过程可以通过微生物铁还原和空气氧化的顺序步骤来刺激。二价Cd、Co、Mn、Ni、Pb和Zn的微生物还原实验表明，除Mn外，所有金属都有一定的固存，金属在0.5 M HCl不溶相中的固存程度与配位数= 6时的晶体离子半径呈正相关。在合成针铁矿/水合铁或含铁天然沉积物中吸附Zn的氧化还原循环实验表明，从铁还原到铁氧化的氧化还原循环比单独的微生物铁还原在自生矿物中吸附更多的Zn。此外，该过程在针铁矿/水合铁混合物中比在含铁天然沉积物中更有效。单独的微生物还原作用导致0.5 M HCl不溶性Zn增加3倍，针铁矿/水合铁中水锌（Zn-aq）增加，但对自然沉积物中Zn的形态没有显著影响。氧化还原循环使针铁矿/水合铁和自然沉积物中Zn的固存能力提高了约12%，并使针铁矿/水合铁中Zn-aq降至与未接种对照相同的水平，低于未接种对照的水平。这些数据表明，原位氧化还原循环可能是减轻地下环境中二价金属污染的有效方法。
Microbial iron reduction is an important biogeochemical process that can affect metal geochemistry in sediments through direct and indirect mechanisms. With respect to Fe(III) (hydr)oxides bearing sorbed divalent metals, recent reports have indicated that (1) microbial reduction of goethite/ferrihydrite mixtures preferentially removes ferrihydrite, (2) this process can incorporate previously sorbed Zn(II) into an authigenic crystalline phase that is insoluble in 0.5 M HCl, (3) this new phase is probably goethite, and (4) the presence of nonreducible minerals can inhibit this transformation. This study demonstrates that a range of sorbed transition metals can be selectively sequestered into a 0.5 M HCl insoluble phase and that the process can be stimulated through sequential steps of microbial iron reduction and air oxidation. Microbial reduction experiments with divalent Cd, Co, Mn, Ni, Pb, and Zn indicate that all metals save Mn experienced some sequestration, with the degree of metal incorporation into the 0.5 M HCl insoluble phase correlating positively with crystalline ionic radius at coordination number = 6. Redox cycling experiments with Zn adsorbed to synthetic goethite/ferrihydrite or iron-bearing natural sediments indicate that redox cycling from iron reducing to iron oxidizing conditions sequesters more Zn within authigenic minerals than microbial iron reduction alone. In addition, the process is more effective in goethite/ferrihydrite mixtures than in iron-bearing natural sediments. Microbial reduction alone resulted in a similar to 3x increase in 0.5 M HCl insoluble Zn and increased aqueous Zn (Zn-aq) in goethite/ferrihydrite, but did not significantly affect Zn speciation in natural sediments. Redox cycling enhanced the Zn sequestration by similar to 12% in both goethite/ferrihydrite and natural sediments and reduced Zn-aq to levels equal to the uninoculated control in goethite/ferrihydrite and less than the uninoculated control in natural sediments. These data suggest that in situ redox cycling may serve as an effective method for mitigating divalent metal contamination in subsurface environments.