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首页> 外文期刊>Environmental Science & Technology >Reduction of organically complexed ferric iron by superoxide in a simulated natural water
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Reduction of organically complexed ferric iron by superoxide in a simulated natural water

机译：在模拟的天然水中通过超氧化物还原有机络合的三价铁

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Superoxide (and potentially its conjugate acid hydroperoxyl) is unique among the reactive oxygen species in that its standard redox potential in circumneutral natural waters potentially allows it to reduce ferric iron to the more soluble ferrous state. Here we have observed the superoxide/hydroperoxyl-mediated reduction of ferric complexes with a variety of synthetic organic ligands and several complexes with natural organic matter (NOM), as well as freshly precipitated amorphous ferric oxyhydroxide, in bicarbonate buffered solutions at pH 8.1. From measurements of superoxide decay in the presence of the complexes, we calculated second-order rate constants for superoxide/hydroperoxyl-mediated reduction that vary from (9.3 0.2) x 10(3) M-1 s(-1) for the complex between Fe(III) and desferrioxamine B up to (1.9 +/- 0.2) x 10(5) M-1 s-1 for Fe(III)-salicylate and (2.3 +/- 0.1) x 10(5) M-1 s(-1) for one of the Fe(III)-NOM complexes. We also verified that ferrous iron was produced from superoxide/hydroperoxyl-mediated Fe(III) reduction using ferrozine to trap free Fe(II). Low yields of the ferrozine complex when compared to the measured rates of superoxide decay suggest that ferric complexes are reduced directly to corresponding ferrous complexes, with much of the ferrous complex reoxidizing before it is able to release free ferrous iron. This is an important consideration for microorganisms, as the kinetics of trace metal uptake is typically governed by free ion activity.
机译：超氧化物（及其潜在的共轭酸氢过氧化物）在活性氧中是独特的，因为其在周围自然水域中的标准氧化还原电势可能使其将三价铁还原为更易溶的亚铁态。在这里，我们观察到在pH值为8.1的碳酸氢盐缓冲溶液中，具有多种合成有机配体的三价铁配合物和具有天然有机物（NOM）的几种配合物以及新鲜沉淀的无定形三氧化二铁的铁配合物的还原。从在复合物存在下超氧化物衰变的测量结果，我们计算出超氧化物/氢过氧化物介导的还原反应的二阶速率常数，其介于（9.3 0.2）x 10（3）M-1 s（-1）之间Fe（III）-水杨酸盐和（2.3 +/- 0.1）x 10（5）M-1的Fe（III）和去铁胺B高达（1.9 +/- 0.2）x 10（5）M-1 s-1 Fe（III）-NOM配合物之一的s（-1）。我们还验证了亚铁是由过氧化氢/氢过氧化物介导的Fe（III）还原生成的，使用铁佐嗪捕获游离的Fe（II）。与测得的超氧化物衰变速率相比，铁二嗪配合物的收率低表明铁配合物直接还原为相应的亚铁配合物，其中许多亚铁配合物在释放游离亚铁之前就被再氧化。对于微生物来说，这是一个重要的考虑因素，因为痕量金属吸收的动力学通常受自由离子活性支配。

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