The role of thermodiffusion in organic pollutant transport in landfill composite liner system

This paper presents a new analytical model for forecasting one-dimensional transient transport of organic pollutant in a typical landfill composite liner including a geomembrane (GMB), a geosynthetic clay liner (GCL) and a soil liner (SL). The model can consider the coupling effect of molecular diffusion, thermodiffusion, advection and linear adsorption processes. Zero concentration gradient condition is adopted at the bottom boundary. The separation of variables method and superposition principle are utilized to derive the solution. The solution is first validated against the results of experimental test and a numerical model. Then, the influence of thermodiffusion is investigated on pollutant migration in typical composite liner. The results reveal that ther-modiffusion may significantly influence the pollutant migration. If the Soret coefficient exceeds 0.01 K-1, regardless of the combination conditions in terms of molecular diffusion, advection and adsorption, the influence of thermodiffusion generally cannot be ignored. The analytical model also can be utilized to design composite liner systems and to verify other numerical models.