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Abstract

Fe (hydr)oxides have a significant impact on the structure and stability of soil organic carbon (SOC) pools, and also drive organic carbon turnover processes via reduction-oxidation reactions. Currently, many studies have paid much attention to organic matter-Fe mineral-microbial interactions on SOC turnover, while there is few research on how exogenous carbon addition abiotically regulates the intrinsic mechanisms of Fe-mediated organic carbon conversion. The study investigated the coupling process of artificial humic acid (A-HA) and Fe(hydr)oxide, the mechanism of inner-sphere ligands, and the capacity for carbon sequestration using TEM, TG, XPS, and wet-chemical disposal. Furthermore, Cs-STEM-EELS and Mössbauer spectra have been carried out to demonstrate the spatial heterogeneity of A-HA/Fe (hydr)oxides and reveal the relationship between the increase in Fe-phase crystallinity and redox sensitivity and the accumulation of organic carbon. Additionally, the dynamics of soil structures on a micro-scale, distribution of carbon-iron microdomains, and the cementing-gluing effect can be observed in the constructing non-living anthropogenic soils,confirming that the formation of stable aggregates is an effective approach to achieving organic carbon indirect protection. We propose that exogenous organic carbon inputs, specifically A-HA, could exert a substantial but hitherto unexplored effect on the geochemistry of iron - carbon turnover and sequestration in anoxic water/solid soils and sediments.