A simple analytical solution for organic contaminant diffusion through a geomembrane to unsaturated soil liner: Considering the sorption effect and Robin-type boundary

Abstract

Landfill leachate often contains soluble hazardous substances. Geomembrane (GM) liner is commonly used to protect the subsurface water. The leachate however may diffuse through the GM and enter the underlying natural soil liner. Analytical or numerical modeling for the leachate transport in the soils helps assess the associated risk to groundwater resources. The analytical model has the advantages of simplicity and easy to implement over the numerical model. Yet there is only an analytical model developed for describing the leachate migration through the GM to the unsaturated soil liner. Its solution however is difficult to evaluate. We herein develop a new analytical model to include the sorption effect and simplify the leachate transport through the GM as a Robin-type boundary condition in the model. The solution of the model is in a simple form and very easy to evaluate. The present solution is then compared with a finite-difference solution and the existing solution. The effect of the retardation factor on the leachate migration is investigated. A sensitivity analysis is also performed to assess the effects of model parameters on the leachate distribution. Finally, the present solution is adopted to estimate the transport parameters based on the data from bench-scale composite liner experiments. Landfill leachate often contains soluble hazardous substances. Geomembrane (GM) liner is commonly used to protect the subsurface water. The leachate however may diffuse through the GM and enter the underlying natural soil liner. Analytical or numerical modeling for the leachate transport in the soils helps assess the associated risk to groundwater resources. The analytical model has the advantages of simplicity and easy to implement over the numerical model. Yet there is only an analytical model developed for describing the leachate migration through the GM to the unsaturated soil liner. Its solution however is difficult to evaluate. We herein develop a new analytical model to include the sorption effect and simplify the leachate transport through the GM as a Robin-type boundary condition in the model. The solution of the model is in a simple form and very easy to evaluate. The present solution is then compared with a finite-difference solution and the existing solution. The effect of the retardation factor on the leachate migration is investigated. A sensitivity analysis is also performed to assess the effects of model parameters on the leachate distribution. Finally, the present solution is adopted to estimate the transport parameters based on the data from bench-scale composite liner experiments.