Advances in Earth Science ›› 2022, Vol. 37 ›› Issue (2): 202-211. doi: 10.11867/j.issn.1001-8166.2021.114
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Xun DUAN 1 , 2 , 3( ), Zhe LI 2 , 3, Miao LIU 1 , 3, Yuanchun ZOU 1( )
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Xun DUAN, Zhe LI, Miao LIU, Yuanchun ZOU. Progress of the Iron-mediated Soil Organic Carbon Preservation and Mineralization[J]. Advances in Earth Science, 2022, 37(2): 202-211.
As one of the core mineral elements for the preservation of organic carbon, iron (Fe) not only has an important influence on the structure of Soil Organic Carbon (SOC) pools and stability, but its redox dynamic changes also drive the SOC turnover processes. According to recent research progress at home and abroad, this paper analyzes the Fe-C coupling relationships from three aspects: Fe-mediated OC preservation mechanisms, factors affecting the stability of Fe-bound OC, and OC mineralization mechanisms driven by the Fe redox processes. Firstly, Fe-mediated OC preservation mechanisms mainly depend on its own mineralogical characteristics. The direct roles include forming Fe-bound OC through adsorption, complexation, co-precipitation and interlayer composites. In addition, the indirect roles include acting as a cementing agent to promote the formation of aggregates, and changing the environmental pH. Secondly, the stability of Fe-bound OC is mainly determined by its own properties (e.g. the mineralogical characteristics of Fe, C∶Fe and the combination with OC), the type of iron-reducing bacteria and the influence of low molecular weight organics. Thirdly, Fe-mediated mineralization processes of OC mainly include the mineralization processes mediated by Fe dissimilatory reduction, and the non-selective OC mineralization processes caused by the hydroxyl radicals generated by the Fenton/Fenton-like reactions driven by Fe(Ⅱ) chemical oxidation. However, iron oxide can also inhibit the excitation effect by forming iron-bound organic carbon with external input carbon, and slow down the mineralization rate of organic carbon by reducing the activity of phenol oxidase. Therefore, the mineralogical properties and redox sensitivity of Fe oxides have an important influence on the accumulation of SOC. Future research directions of Fe-C coupling relationships that should be strengthened are proposed, aiming to deeply analyze the internal mechanisms of Fe-mediated OC dynamic changes, and provide a theoretical basis for SOC sequestration and emission reduction facilitating the realization of "Carbon Neutralization".