Analytical solutions for diffusion of organic contaminant through GCL triple-layer composite liner considering degradation in liner

Analytical solutions are presented for analyzing diffusion of organic contaminant through a triple-layer composite liner consisting of a geomembrane, a geosynthetic clay liner (GCL) and an attenuation liner (AL). The degradation of organic contaminant in the GCL and AL is considered. Steady-state and full analytical solutions are obtained for two scenarios with zero-concentration or zero-mass-flux boundary conditions at the base of the triple-layer composite liner. The validity and accuracy of the solutions are verified by comparing with an existing analytical solution and a numerical method. Results show that the AL yields major effect to the barrier efficiency of triple-layer composite liner. The contaminant half-life in the GCL has little influence on the mass flux and concentration at the base of triple-layer composite liner. The mass flux and concentration at the base of the triple-layer composite liner decrease with the decrease in contaminant half-life in AL. The steady-state times of bottom mass flux and concentration decrease with the decrease in the contaminant half-life in AL. The mass flux at the base of the triple-layer composite liner decreases with the increase in the thickness or sorption capacity of AL. The steady-state time of bottom mass flux decreases with the decrease in the thickness or sorption capacity of AL. The equivalence between GCL triple-layer composite liner and standard CCL composite liner considering degradation of contaminant is investigated based on the steady-state and full solutions. The analytical solutions can be used for preliminary design of landfill composite liners, verification of complicated numerical methods and evaluation of experimental data.