Iron (Fe) minerals constitute a major control on organic carbon (OC) storage in soils and sediments. While previous research has mainly targeted Fe (oxyhydr)oxides, the impact of Fe sulfides and their subsequent oxidation on OC dynamics remains unresolved in redox-fluctuating environments. Here, we investigated the impact of dissolved organic matter (DOM) on FeS oxidation and how FeS and its oxidation may alter the retention and nature of DOM. After the anoxic reaction of DOM with FeS, FeS preferentially removed high-molecular-weight and nitrogen-rich compounds and promoted the formation of aqueous sulfurized organic molecules, according to Fourier transform–ion cyclotron resonance–mass spectrometry (FT-ICR-MS) analysis. When exposed to O₂, FeS oxidized to nanocrystalline lepidocrocite and additional aqueous sulfurized organic compounds were generated. The presence of DOM decreased the particle size of the resulting nano-lepidocrocite based on Mössbauer spectroscopy. Following FeS oxidation, most solid-phase OC remained associated with the newly formed lepidocrocite via a monodentate chelating mechanism (based on FTIR analysis), and FeS oxidation caused only a slight increase in the solubilization of solid-phase OC. Collectively, this work highlights the under-appreciated role of Fe sulfides and their oxidation in driving OC transformation and preservation.

中文翻译：

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溶解有机物存在下 FeS 氧化过程中的次生矿物形成和碳动力学

铁 (Fe) 矿物质是土壤和沉积物中有机碳 (OC) 储存的主要控制因素。虽然以前的研究主要针对铁（羟基）氧化物，但在氧化还原波动的环境中，硫化铁及其随后的氧化对 OC 动力学的影响仍未得到解决。在这里，我们研究了溶解有机物 (DOM) 对 FeS 氧化的影响，以及 FeS 及其氧化如何改变 DOM 的保留和性质。傅里叶变换离子回旋共振质谱 (FT-ICR-MS) 表明，DOM 与 FeS 发生缺氧反应后，FeS 优先去除高分子量和富氮化合物，促进水性硫化有机分子的形成分析。当暴露于 O ₂, FeS 被氧化成纳米晶纤铁矿和额外的含水硫化有机化合物。基于穆斯堡尔光谱，DOM 的存在降低了所得纳米纤铁矿的粒度。在 FeS 氧化之后，大多数固相 OC 通过单齿螯合机制（基于 FTIR 分析）与新形成的纤铁矿保持联系，并且 FeS 氧化仅导致固相 OC 溶解的轻微增加。总的来说，这项工作突出了 Fe 硫化物及其氧化在驱动 OC 转化和保存中的被低估的作用。