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首页> 外文期刊>Geochimica et Cosmochimica Acta: Journal of the Geochemical Society and the Meteoritical Society >Molecular-level modes of As binding to Fe(III) (oxyhydr)oxides precipitated by the anaerobic nitrate-reducing Fe(II)-oxidizing Acidovorax sp. strain BoFeN1
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Molecular-level modes of As binding to Fe(III) (oxyhydr)oxides precipitated by the anaerobic nitrate-reducing Fe(II)-oxidizing Acidovorax sp. strain BoFeN1

机译：厌氧硝酸盐还原Fe（II）-氧化Acidovorax sp沉淀的As与Fe（III）（羟基）氧化物结合的分子水平模式。 BoFeN1菌株

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Sorption of contaminants such as arsenic (As) to natural Fe(III) (oxyhydr)oxides is very common and has been demonstrated to occur during abiotic and biotic Fe(II) oxidation. The molecular mechanism of adsorption- and co-precipitation of As has been studied extensively for synthetic Fe(III) (oxyhydr)oxide minerals but is less documented for biogenic ones. In the present study, we used Fe and As K-edge X-ray Absorption Near Edge Structure (XANES), extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, M?ssbauer spectroscopy, XRD, and TEM in order to investigate the interactions of As(V) and As(III) with biogenic Fe(III) (oxyhydr)oxide minerals formed by the nitrate-reducing Fe(II)-oxidizing bacterium Acidovorax sp. strain BoFeN1. The present results show the As immobilization potential of strain BoFeN1 as well as the influence of As(III) and As(V) on biogenic Fe(III) (oxyhydr)oxide formation. In the absence of As, and at low As loading (As:Fe. ≤. 0.008. mol/mol), goethite (Gt) formed exclusively. In contrast, at higher As/Fe ratios (As:Fe = 0.020-0.067), a ferrihydrite (Fh) phase also formed, and its relative amount systematically increased with increasing As:Fe ratio, this effect being stronger for As(V) than for As(III). Therefore, we conclude that the presence of As influences the type of biogenic Fe(III) (oxyhydr)oxide minerals formed during microbial Fe(II) oxidation. Arsenic-K-edge EXAFS analysis of biogenic As-Fe-mineral co-precipitates indicates that both As(V) and As(III) form inner-sphere surface complexes at the surface of the biogenic Fe(III) (oxyhydr)oxides. Differences observed between As-surface complexes in BoFeN1-produced Fe(III) (oxyhydr)oxide samples and in abiotic model compounds suggest that associated organic exopolymers in our biogenic samples may compete with As oxoanions for sorption on Fe(III) (oxyhydr)oxides surfaces. In addition HRTEM-EDXS analysis suggests that As(V) preferentially binds to poorly crystalline phases, such as ferrihydrite, while As(III) did not show any preferential association regarding Fh or Gt.
机译：污染物（例如砷）对天然Fe（III）（羟基）氧化物的吸附非常普遍，并且已证明在非生物和生物Fe（II）氧化过程中发生。砷的吸附和共沉淀的分子机理已被广泛研究用于合成的Fe（III）（羟基）氧化物氧化物矿物，但是对于生物成因矿物则文献较少。在本研究中，我们使用铁和砷的K边缘X射线吸收近边缘结构（XANES），扩展X射线吸收精细结构（EXAFS）光谱，Msssbauer光谱，XRD和TEM来研究As（V）和As（III）与由硝酸盐还原的Fe（II）氧化细菌Acidovorax sp。形成的Fe（III）（羟基）氧化物生物成因的相互作用。 BoFeN1菌株。目前的结果表明菌株BoFeN1的As固定化潜力以及As（III）和As（V）对生物成因的Fe（III）（羟基）氧化物形成的影响。在不存在As的情况下，在As含量低的情况下（As：Fe。≤0.008。mol / mol），仅形成针铁矿（Gt）。相反，在较高的As / Fe比（As：Fe = 0.020-0.067）下，也形成了水铁矿（Fh）相，并且其相对量随着As：Fe比的增加而系统地增加，这种作用对于As（V）更为明显。比As（III）因此，我们得出结论，As的存在会影响微生物Fe（II）氧化过程中形成的生物型Fe（III）（羟基）氧化物矿物的类型。对成因的As-Fe矿物共沉淀物进行砷-K-边缘EXAFS分析表明，As（V）和As（III）都在成因的Fe（III）（羟基）氧化物表面形成内球表面复合物。 BoFeN1生产的Fe（III）（羟基）氧化物样品和非生物模型化合物中As-表面配合物之间的差异表明，我们的生物样品中相关的有机外聚合物可能与As含氧阴离子竞争吸附在Fe（III）（羟基）氧化物上。表面。另外，HRTEM-EDXS分析表明，As（V）优先结合弱结晶相，如三水铝石，而As（III）没有显示出任何有关Fh或Gt的优先结合。

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