Biosciences Division, Argonne National Laboratory, Argonne, Illinois 60439-4843, USA.
Environ Sci Technol. 2010 Jun 15;44(12):4570-6. doi: 10.1021/es100294w.
Microbial reduction of Fe(III) oxides results in the production of Fe(II) and may lead to the subsequent formation of Fe(II)-bearing secondary mineralization products including magnetite, siderite, vivianite, chukanovite (ferrous hydroxy carbonate (FHC)), and green rust; however, the factors controlling the formation of specific Fe(II) phases are often not well-defined. This study examined effects of (i) a range of inorganic oxyanions (arsenate, borate, molybdate, phosphate, silicate, and tungstate), (ii) natural organic matter (citrate, oxalate, microbial extracellular polymeric substances [EPS], and humic substances), and (iii) the type and number of dissimilatory iron-reducing bacteria on the bioreduction of lepidocrocite and formation of Fe(II)-bearing secondary mineralization products. The bioreduction kinetics clustered into two distinct Fe(II) production profiles. "Fast" Fe(II) production kinetics [19-24 mM Fe(II) d(-1)] were accompanied by formation of magnetite and FHC in the unamended control and in systems amended with borate, oxalate, gellan EPS, or Pony Lake fulvic acid or having "low" cell numbers. Systems amended with arsenate, citrate, molybdate, phosphate, silicate, tungstate, EPS from Shewanella putrefaciens CN32, or humic substances derived from terrestrial plant material or with "high" cell numbers exhibited comparatively slow Fe(II) production kinetics [1.8-4.0 mM Fe(II) d(-1)] and the formation of green rust. The results are consistent with a conceptual model whereby competitive sorption of more strongly bound anions blocks access of bacterial cells and reduced electron-shuttling compounds to sites on the iron oxide surface, thereby limiting the rate of bioreduction.
微生物还原三价铁氧化物会产生二价铁，并可能导致随后形成含二价铁的次生矿物化产物，包括磁铁矿、菱铁矿、蓝铁矿、水羟铁碳酸盐（FHC）和绿锈；然而，控制特定二价铁相形成的因素通常不明确。本研究考察了（i）一系列无机含氧阴离子（砷酸盐、硼酸盐、钼酸盐、磷酸盐、硅酸盐和钨酸盐）、（ii）天然有机物（柠檬酸盐、草酸盐、微生物胞外聚合物（EPS）和腐殖质）以及（iii）异化铁还原细菌的类型和数量对针铁矿生物还原和含二价铁次生矿物化产物形成的影响。生物还原动力学分为两种截然不同的二价铁生成曲线。“快速”二价铁生成动力学[19-24 mM Fe(II) d(-1)]伴随着磁铁矿和 FHC 的形成，在未添加试剂的对照和硼酸盐、草酸盐、结冷胶 EPS 或庞尼湖富里酸添加的系统中，或者细胞数量“低”时，会出现这种情况。添加砷酸盐、柠檬酸盐、钼酸盐、磷酸盐、硅酸盐、钨酸盐、腐殖质来源于 Shewanella putrefaciens CN32 的 EPS 或来自陆地植物材料的腐殖质，或细胞数量“高”的系统表现出相对较慢的二价铁生成动力学[1.8-4.0 mM Fe(II) d(-1)]和绿锈的形成。结果与一个概念模型一致，即更强结合阴离子的竞争吸附阻止了细菌细胞和还原电子穿梭化合物到达氧化铁表面的位点，从而限制了生物还原的速度。
