针铁矿
鳞片岩
铁质
化学
氧化铁
结晶度
矿物
斯沃特曼矿
氧化物
无机化学
氧气
有机质
铁酸盐
铁
环境化学
氧化还原
矿物学
赤铁矿
磁铁矿
结晶学
有机化学
吸附
作者
Chunmei Chen,Aaron Thompson
标识
DOI:10.1021/acs.est.7b05102
摘要
Abiotic Fe(II) oxidation by O2 commonly occurs in the presence of mineral sorbents and organic matter (OM) in soils and sediments; however, this tertiary system has rarely been studied. Therefore, we examined the impacts of mineral surfaces (goethite and γ-Al2O3) and organic matter [Suwannee River fulvic acid (SRFA)] on Fe(II) oxidation rates and the resulting Fe(III) (oxyhydr)oxides under 21 and 1% pO2 at pH 6. We tracked Fe dynamics by adding 57Fe(II) to 56Fe-labeled goethite and γ-Al2O3 and characterized the resulting solids using 57Fe Mössbauer spectroscopy. We found Fe(II) oxidation was slower at low pO2 and resulted in higher-crystallinity Fe(III) phases. Relative to oxidation of Fe(II)(aq) alone, both goethite and γ-Al2O3 surfaces increased Fe(II) oxidation rates regardless of pO2 levels, with goethite being the stronger catalyst. Goethite surfaces promoted the formation of crystalline goethite, while γ-Al2O3 favored nano/small particle or disordered goethite and some lepidocrocite; oxidation of Fe(II)aq alone favored lepidocrocite. SRFA reduced oxidation rates in all treatments except the mineral-free systems at 21% pO2, and SRFA decreased Fe(III) phase crystallinity, facilitating low-crystalline ferrihydrite in the absence of mineral sorbents, low-crystalline lepidocrocite in the presence of γ-Al2O3, but either crystalline goethite or ferrihydrite when goethite was present. This work highlights that the oxidation rate, the types of mineral surfaces, and OM control Fe(III) precipitate composition.
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