Research progress on the impact and mechanisms of different passivators on soil organic carbon transformation.

Passivators can reduce the bioavailability and mobility of heavy metals by forming stable complexes or precipitates, and achieve the remediation of heavy metal-polluted soil. Organic carbon is an important parameter reflecting soil quality and health. Organic carbon transformation process plays a decisive role in atmospheric chemistry and global carbon cycling, and is affected by land use ways, agronomic measures, and restoration activities. On the one hand, the application of passivators will change soil physical and chemical properties, such as soil structure, aggregate composition, pH, CEC, which in turn will affect the structure and diversity of soil microbial communities, the activities of organic carbon conversion enzymes, and the transformation of soil organic carbon. The above effects are regulated by various factors such as the type, application amount, and application time of passivators. We discussed the composition of soil organic carbon and its changes under different passivator application conditions, and explored the mechanism underlying the effect of passivators on soil organic carbon transformation. In the future, new types of passivator with both carbon sequestration and heavy metal passivation functions should be developed. The temporal and spatial distribution patterns of soil organic carbon turnover and stable organic carbon after the application of passivators should be examined.