HOCs bioavailability response to soil aging: Focusing on the indirect effects of aging conditions, environmental factors, and carrier-mediated changes in soil properties - A review

The accumulation of hydrophobic organic contaminants (HOCs) in soil is a global problem, and the time-dependent interface behavior after entering the soil directly determines the HOCs bioavailability, which has attracted much attention. Despite a significant volume of reviews on the relationship between aging and HOCs residues in soil have been published in the past few decades, whereas a set of descriptive about the effects of aging on HOCs bioavailability are still lacking. We summarizes the occurrence concentration of typical HOCs in global soil and its aging mechanism in soil. Considering the importance of bioavailability, the influence of various factors (aging conditions, environmental factors, carriers, soil characteristics and pollutant properties) on the HOCs bioavailability and risk assessment were further analyzed. Among them, linking the alternations in soil properties mediated by external factors with the changes in the bioavailability of HOCs in soil over time is the main highlight. We suggest that future research should focus on: (1) the dynamic response of soil micro-interfaces to aging processes and their relationship with the variations of HOCs bioavailability during aging. (2) the differences in adsorption, desorption behavior and bioavailability of HOCs in soils between enhanced aging (freeze-thaw cycles and dry-wet cycles) and constant temperature and humidity aging, and between natural and artificial aging. (3) the effects of aging on the environmental behavior and bioavailability of HOCs in soils in the presence of multiple contaminants and environmental carriers (biochar and microplastics), especially the synchronous aging (carriers aging within the soil) rather than the pre-aging.