Metal oxyhydroxide dissolution as promoted by structurally diverse siderophores and oxalate
Metal oxyhydroxide dissolution as promoted by structurally diverse siderophores and oxalate
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DOI：
10.1016/j.gca.2014.06.024
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发表时间：
2014-09-15
影响因子：
5
通讯作者：
Duckworth, Owen W.
中科院分区：
文献类型：
--
作者：
Akafia, Martin M.;Harrington, James M.;Duckworth, Owen W.
铁载体是一类对Fe(III)具有高亲和力的生物配位体，能促进稀溶矿物相中金属离子的溶解。然而，大多数地球化学研究都集中在对DFOB的反应性进行量化，DFOB是一种模型三氢氧磷酸盐铁载体。本研究利用三种不同的铁载体，去铁胺B、根铁蛋白和原络合蛋白，其结构包含最常观察到的微生物铁载体的结合部分，通过在pH=5-9下的批量溶解实验，研究了在没有和存在普遍存在的低分子有机酸草酸盐的情况下，铁载体促进的FeOOH、CoOOH和MnOOH的溶解速度。根据金属氢氧化物的特性和溶液的pH值，对金属-铁载体复合体和总溶解金属浓度进行了持续1小时至14天的监测。结果表明，在有铁载体存在的情况下，MnOOH和CoOOH的溶解速度一般比FeOOH快。在大多数实验条件下，FeOOH完全以配体促进的溶解机制溶解，而MnOOH和CoOOH主要以还原溶解机制溶解。对于FeOOH，铁载体促进的溶解速率与相应的水溶液中Fe(III)络合物的稳定常数呈趋势。在草酸盐存在下，测量到的铁载体促进的溶解速率与单配体体系中观察到的速率相比，被发现增加、降低或保持不变，这取决于体系的pH、铁载体的存在和金属氧氢氧化物的特性。在草酸盐存在下，观察到的溶解速率的增加通常FeOOH大于MnOOH或CoOOH。这些结果阐明了环境中铁载体对氢氧化铁矿物和非铁氢氧化物矿物的潜在溶解机制，并可能为通过低分子有机酸和铁载体的协调渗出促进金属获取的生物策略提供进一步的见解。(C)2014爱思唯尔有限公司。保留所有权利。
Siderophores, a class of biogenic ligands with high affinities for Fe(III), promote the dissolution of metal ions from sparingly soluble mineral phases. However, most geochemical studies have focused on quantifying the reactivity of DFOB, a model trishydroxamate siderophore. This study utilized three different siderophores, desferrioxamine B, rhizoferrin, and protochelin, with structures that contain the most commonly observed binding moieties of microbial siderophores to examine the siderophore-promoted dissolution rates of FeOOH, CoOOH, and MnOOH in the absence and presence of the ubiquitous low molecular mass organic acid oxalate by utilizing batch dissolution experiments at pH = 5-9. Metal-siderophore complex and total dissolved metal concentrations were monitored for durations of one hour to fourteen days, depending on the metal oxyhydroxide identity and solution pH. The results demonstrate that MnOOH and CoOOH generally dissolve more quickly in the presence of siderophores than FeOOH. Whereas FeOOH dissolved exclusively by a ligand-promoted dissolution mechanism, MnOOH and CoOOH dissolved predominantly by a reductive dissolution mechanism under most experimental conditions. For FeOOH, siderophore-promoted dissolution rates trended with the stability constant of the corresponding aqueous Fe(III) complex. In the presence of oxalate, measured siderophore-promoted dissolution rates were found to increase, decrease, or remain unchanged as compared to the observed rates in single-ligand systems, depending on the pH of the system, the siderophore present, and the identity of the metal oxyhydroxide. Increases in observed dissolution rates in the presence of oxalate were generally greater for FeOOH than for MnOOH or CoOOH. These results elucidate potential dissolution mechanisms of both ferric and non-ferric oxyhydroxide minerals by siderophores in the environment, and may provide further insights into the biological strategies of metal acquisition facilitated by coordinated exudation of low molecular weight organic acids and siderophores. (C) 2014 Elsevier Ltd. All rights reserved.