Department of Environmental Geosciences , University of Vienna , Althanstrasse 14(UZA II) 1090 Vienna , Austria.
Eawag , Swiss Federal Institute of Aquatic Science and Technology , Ueberlandstr. 133 , CH-8600 , Dübendorf , Switzerland.
Environ Sci Technol. 2019 Jan 2;53(1):98-107. doi: 10.1021/acs.est.8b03909. Epub 2018 Dec 20.
Dissolution of Fe(III) (hydr)oxide minerals by siderophores (i.e., Fe-specific, biogenic ligands) is an important step in Fe acquisition in environments where Fe availability is low. The observed coexudation of reductants and ligands has raised the question of how redox reactions might affect ligand-controlled (hydr)oxide dissolution and Fe acquisition. We examined this effect in batch dissolution experiments using two structurally distinct ligands (desferrioxamine B (DFOB) and N, N'-di(2-hydroxybenzyl)ethylene-diamine- N, N'-diacetic acid (HBED)) and four Fe(III) (hydr)oxide minerals (lepidocrocite, 2-line ferrihydrite, goethite and hematite) over an environmentally relevant pH range (4-8.5). The experiments were conducted under anaerobic conditions with varying concentrations of (adsorbed) Fe(II) as the reductant. We observed a catalytic effect of Fe(II) on ligand-controlled dissolution even at submicromolar Fe(II) concentrations with up to a 13-fold increase in dissolution rate. The effect was larger for HBED than for DFOB. It was observed for all four Fe(III) (hydr)oxide minerals, but it was most pronounced for goethite in the presence of HBED. It was observed over the entire pH range with the largest effect at pH 7 and 8.5, where Fe deficiency typically occurs. The occurrence of this catalytic effect over a range of environmentally relevant conditions and at very low Fe(II) concentrations suggests that redox-catalyzed, ligand-controlled dissolution may be significant in biological Fe acquisition and in redox transition zones.
铁（III）（水合）氧化物矿物通过铁载体（即，特定于铁的生物配体）溶解是在铁供应不足的环境中获取铁的重要步骤。还原剂和配体的同时共分泌提出了一个问题，即氧化还原反应如何影响配体控制的（水合）氧化物溶解和铁获取。我们使用两种结构不同的配体（去铁胺 B（DFOB）和 N，N'-二（2-羟基苄基）乙二胺-N，N'-二乙酸（HBED））和四种铁（III）（水合）氧化物矿物（针铁矿、2 线水铁矿、针铁矿和赤铁矿）在环境相关的 pH 值范围内（4-8.5）进行了分批溶解实验，以检查这种影响。实验在厌氧条件下进行，还原剂为不同浓度的（吸附）Fe（II）。我们观察到 Fe（II）对配体控制的溶解具有催化作用，即使在亚毫摩尔 Fe（II）浓度下，溶解速率也增加了高达 13 倍。HBED 的效果大于 DFOB。该效果在所有四种铁（III）（水合）氧化物矿物中均观察到，但在 HBED 存在下，针铁矿的效果最为明显。该效果在整个 pH 值范围内均观察到，在 pH 值为 7 和 8.5 时效果最大，这是铁缺乏通常发生的地方。在一系列环境相关条件下和非常低的 Fe（II）浓度下都观察到这种催化作用，表明氧化还原催化的、配体控制的溶解在生物铁获取和氧化还原过渡带中可能非常重要。
