Abstract Fe(II) oxidation by O2 is an important process generating Fe (oxyhydr)oxides, which play sorptive, structural and electron-transfer roles in soils. Here we explored how native minerals and organic matter (OM) affect the rate of Fe(II) oxidation and resulting de novo Fe(III) minerals in soil slurries. A topsoil was collected from the Luquillo Experimental Forest, and a topsoil and subsoil were collected from a cultivated site at the Calhoun Experimental Forest. We oxidized 57Fe(II) in these soils either untreated or with OM and/or Fe (oxyhydr)oxides removed. We measured Fe oxidation kinetics by tracking the loss of Fe(II) and characterized the de novo Fe(III) solids using 57Fe Mossbauer spectroscopy. We find that OM retarded Fe(II) oxidation, while pre-existing Fe (oxyhydr)oxides played a significant role in catalyzing Fe(II) oxidation. The non-extractable (residual) soil minerals (i.e. phyllosilicates and quartz) after removing Fe (oxyhydr)oxides, had only a minor effect on oxidation rates. In the topsoils, OM resulted in lower-crystallinity Fe(III) minerals, including nanogoethite and highly-disordered Fe phases, relative to soils with OM-removed. Goethite of varying crystallinity was promoted by the pre-existing Fe (oxyhydr)oxides in all soils, in contrast to homogenous oxidation treatments in which lepidocrocite was formed. Fe(II) oxidation in the Calhoun subsoil, which was enriched in native crystalline Fe phases and depleted in OM, resulted in large-particle goethite with the highest crystallinity of all treatments. Crystalline hematite was also formed in the Calhoun subsoil most likely due to a templating effect of pre-existing hematite. These findings suggest that the nature of de novo formed Fe minerals in soils and sediments may depend strongly on resident existing soil OM and Fe phases. This study extends similar results from previous model mineral and organic experiments to whole, complex soils and thus constitutes a significant step forward in understanding Fe transformation in natural environments.

中文翻译：

---

原生土壤有机质和矿物质对亚铁氧化的影响

摘要 O2氧化Fe(II)是生成Fe(羟基)氧化物的重要过程，在土壤中具有吸附作用、结构作用和电子转移作用。在这里，我们探讨了天然矿物质和有机质 (OM) 如何影响 Fe(II) 氧化速率以及土壤浆中产生的从头 Fe(III) 矿物质。从 Luquillo 试验林收集表土，从 Calhoun 试验林的耕地收集表土和底土。我们氧化了这些土壤中的 57Fe(II)，要么未经处理，要么去除 OM 和/或 Fe（羟基）氧化物。我们通过跟踪 Fe(II) 的损失来测量 Fe 氧化动力学，并使用 57Fe Mossbauer 光谱表征从头 Fe(III) 固体。我们发现 OM 延缓了 Fe(II) 氧化，而预先存在的 Fe(羟基) 氧化物在催化 Fe(II) 氧化中发挥了重要作用。去除铁（羟基）氧化物后的不可提取（残留）土壤矿物质（即页硅酸盐和石英）对氧化速率的影响很小。在表土中，相对于去除 OM 的土壤，OM 导致较低结晶度的 Fe(III) 矿物，包括纳米针铁矿和高度无序的 Fe 相。与形成纤铁矿的均相氧化处理相反，所有土壤中预先存在的 Fe（羟基）氧化物促进了不同结晶度的针铁矿。Calhoun 底土中的 Fe(II) 氧化富含天然结晶 Fe 相并耗尽 OM，导致大颗粒针铁矿在所有处理中结晶度最高。结晶赤铁矿也在卡尔霍恩底土中形成，很可能是由于预先存在的赤铁矿的模板效应。这些发现表明，土壤和沉积物中从头形成的 Fe 矿物的性质可能在很大程度上取决于驻留的现有土壤 OM 和 Fe 相。这项研究将先前模型矿物和有机实验的类似结果扩展到完整、复杂的土壤，从而在理解自然环境中的铁转化方面向前迈出了重要一步。