Organo-mineral interactions are widely distributed in soils, these interactions could stable and immobilize soil organic matter. SOM interacts physiochemically with mineral matrices to be selectively preserved and occluded by growing minerals and/or pore spaces of mineral aggregates, which are potentially inaccessible to plant root cells and soil microorganisms via the limitation of their movement. Among these processes, calcite crystals grow via growing hillocks in calcareous soils in proper supersaturated conditions. Our results have shown that following adsorption, SOMs are gradually occluded by the advancing steps of spirals on the calcite (104) face grown in relatively high supersaturated solutions, through the embedment, compression and closure of organic particles into cavities observed by time-resolved in situ atomic force microscopy (AFM). This occlusion progress is mediated by various factors such as the surface charge, surface functional groups and molecular weight of organic substances. Moreover, organic substances combine with clay minerals to formation of organo-clay complexes, then the complexes are subsequently occluded within calcite minerals. These <i>in situ</i> observations may provide new insights into the organo-mineral interaction, resulting in incorporation of SOM into minerals with a longer storage time to delay degradation in soils. This will improve our understanding of carbon cycling and immobilization in soil ecological systems.

Molecular mechanisms of occlusion of soil organic matters within calcite by growing hillocks

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