Soils and sediments are major reservoirs of organic matter (OM), whose dynamic turnover has a major impact on carbon cycling and global climate. OM in soils and sediments is predominantly associated with minerals, which decelerate OM decomposition and could help store carbon. However, iron (Fe) minerals could also degrade OM and release a fraction of OM to the atmosphere as CO₂ and CH₄, but the coupling of these processes is only partly understood. In this Review, we describe the mechanisms and importance of coupled iron–carbon (Fe–C) cycles. Oxygenation of structural Fe(II) in minerals generates reactive oxygen species, which either degrades or synthesizes OM. Reactive oxygen species can also either decrease or increase extracellular enzyme activity and microbial activity, thus indirectly transforming OM. In addition, Fe(III) reduction contributes to OM oxidation through anaerobic respiration. By contrast, OM affects the redox properties of Fe minerals by serving as electron donor, acceptor, shuttle, buffer or conductor and by co-precipitation and complexation with Fe minerals. These feedback mechanisms can result in complex interconnected Fe–C cycling processes; hence, future work must focus on attaining the net impact of combined Fe–C cycles.

土壤和沉积物是有机质（OM）的主要储存库，其动态周转对碳循环和全球气候产生重大影响。土壤和沉积物中的有机质主要与矿物质有关，矿物质可以减缓有机质的分解并有助于储存碳。_{然而，铁 (Fe) 矿物也会降解 OM，并将一小部分 OM 以 CO 2}和 CH ₄的形式释放到大气中，但这些过程的耦合仅被部分理解。在这篇综述中，我们描述了耦合铁碳（Fe-C）循环的机制和重要性。矿物中结构 Fe(II) 的氧化会产生活性氧，从而降解或合成 OM。活性氧还可以降低或增加细胞外酶活性和微生物活性，从而间接转化 OM。此外，Fe(III) 还原有助于通过无氧呼吸氧化 OM。相比之下，OM 通过充当电子供体、受体、穿梭、缓冲剂或导体以及通过与 Fe 矿物共沉淀和络合来影响 Fe 矿物的氧化还原性质。这些反馈机制可能导致复杂的相互关联的 Fe-C 循环过程；因此，