Climate-Driven Sink-to-Source Transitions for Microplastics in Terrestrial Systems

Abstract Microplastics (MPs) are increasingly recognized as pervasive contaminants in terrestrial environments, where soils act as major dynamic reservoirs that retain particles but can also release them through hydrological, erosional, and atmospheric pathways. Climate change is altering the physical, hydrological, and biogeochemical controls that govern the MP retention-release balance. This review develops a climate-driven sink-to-source transition framework in which terrestrial systems shift episodically from retention-dominated to export-active states. We synthesize evidence that changes in freeze–thaw regimes and drought-rewetting reorganize pore networks and preferential flow; extreme rainfall and runoff can exceed hydrological retention and redistribute MPs vertically and laterally; and warming and salinization reconfigure interfacial interactions, polymer aging, aggregation behavior, and microbially mediated transport processes. Atmospheric entrainment and snowpack-snowmelt pathways further connect terrestrial MP reservoirs with other environmental compartments. Across these climate drivers, MP mobility depends on the coupled evolution of pore architecture, water flux, particle properties, and biogeochemical conditions rather than on any single forcing factor. By integrating laboratory studies, field observations, and emerging modeling perspectives, this review provides a mechanistic foundation for predicting terrestrial MP redistribution and associated environmental risks under ongoing climate change.