Contaminant transport through landfill composite liners due to geomembrane defects

Although a number of studies have been devoted to the assessment of the leachate flow rate through defects in geomembranes, which are routinely used in conjunction with low-permeability mineral layers for the lining of waste disposal facilities, relatively little attention has been paid to the mechanisms that control the transport of contaminants. A theoretical framework is here presented to model the advective-diffusive transport of inorganic contami-nants through defects of uniform width and infinite length (holed wrinkles, defective seams, etc.), whereby imperfect contact conditions between the geomembrane and the underlying min-eral layer are considered, and the mass conservation condition is imposed for both the solvent and the solute phases. Closed-form analytical solutions have been derived to assess the contam-inant mass flow rate for the cases of pure advection and pure diffusion, with a view to quantify-ing the error associated with the simplified calculation approaches that are currently adopted for the performance-based design of landfill composite liners.