Spatiotemporal dynamics of leachate transport in compacted clay liners: Coupled effects of dynamic slip and microbial...

Landfill leachates containing hazardous heavy metals (e.g., Pb, Cd), persistent organic pollutants, and antibiotic residues pose severe contamination risks to groundwater and soil ecosystems. Compacted clay liners (CCLs) serve as critical components in landfill impermeable systems, where elucidating leachate migration mechanisms is fundamental for assessing pollutant diffusion risks and achieving long-term containment. This study employs mercury intrusion porosimetry to reveal micro-nano- dominated pore structures in CCLs, proposing a novel modeling framework integrating microscale mechanical constraints and spatiotemporal heterogeneity of clay pores. This framework unveils cascading feedback mechanisms linking community succession, interfacial dynamics, and seepage behavior, ultimately quantifying their coupled effects on leachate migration. Results demonstrate that microbial succession serves as the primary driver of leachate flux oscillations characterized by four distinct phases, peaking at the end of Phase II with flux oscillation amplitude increasing by 149.69 % under pore enlargement. Slip effects significantly enhance seepage dynamics, with average flow velocities under strong-slip conditions reaching 2.51-flod those of no-slip scenarios, accompanied by a flow regime transition from Poiseuille to pseudo-plug patterns. The nonlinear responses of leachate flux elucidate spatiotemporal dependencies: the time required to reach fully developed slip is prolonged by 38.71 % as biofilm stabilization gradually saturates slip intensity; 10 μm pores enter the decay phase at 52.23 %-time node, while 200 μm pores transition at 83.31 %; the multiphase interfacial coupling effects become dominant with pore enlargement, amplifying flux by 691-fold. This work provides theoretical foundations for durability evaluation of landfill barriers and parameterization of multiscale seepage models.