The effect of iron on the preservation of organic carbon in marine sediments and its implications for carbon sequestration

Marine sediments are the most significant reservoir of organic carbon (OC) in Earth’s surface system. Iron, a crucial component of the marine biogeochemical cycle, has a considerable impact on marine ecology and carbon cycling. Understanding the effect of iron on the preservation of OC in marine sediments is essential for comprehending biogeochemical processes of carbon and climate change. This review summarizes the methods for characterizing the content and structure of iron-bound OC and explores the influencing mechanism of iron on OC preservation in marine sediments from two aspects: the selective preservation of OC by reactive iron minerals (iron oxides and iron sulfides) and iron redox processes. The selective preservation of sedimentary OC is influenced by different types of reactive iron minerals, OC reactivity, and functional groups. The iron redox process has dual effects on the preservation and degradation of OC. By considering sedimentary records of iron-bound OC across diverse marine environments, the role of iron in long-term preservation of OC and its significance for carbon sequestration are illustrated. Future research should focus on identifying effective methods for extracting reactive iron, the effect of diverse functional groups and marine sedimentary environments on the selective preservation of OC, and the mediation of micro-organisms. Such work will help elucidate the influencing mechanisms of iron on the long-term burial and preservation of OC and explore its potential application in marine carbon sequestration to maximize its role in achieving carbon neutrality.