Thermally Induced Coupled Effects on Contaminant Transport in Composite Landfill Liners: An Analytical Modeling Approach

ABSTRACT Landfill liners serve as crucial barriers against contaminant migration. However, temperature effects can induce thermal diffusion and may cause clay liners to crack, significantly reducing containment performance. This study presents an analytical model for evaluating coupled heat and mass transport in a composite liner system. The system contains an intact geomembrane over a fractured compacted clay layer, and the model works under both steady‐state and transient conditions. The model incorporates diffusion, degradation, and thermal diffusion processes within both the soil matrix and the fractures. The validity and robustness of the proposed approach were verified through comparisons with existing analytical models. Results demonstrate that high Soret coefficients accelerate contaminant transport and cause abnormal contaminant accumulation far from the source, raising pollution risks in low concentration areas. The width of the fracture plays a dominant role in the breakthrough time and steady state concentration of contaminants, while the effect of changes in fracture spacing is not significant. Temperature difference has the most significant effect on the transport of Dichlorodiphenyltrichloroethane (DDT) and is the most relatively significant factor. The proposed analytical model shows that thermal diffusion shortens the service time of barrier systems. Fractures caused by temperature gradients also reduce their service life. These effects are particularly strong in the early stage. To ensure the long‐term operation of the barrier systems, it is vital to reduce the temperature difference between landfills and the external environment. It is also crucial to improve the degradation rates of contaminants and to prevent the formation of fractures.