Volatile organic compound diffusion and sorption coefficients for a needle-punched GCL

Test apparatus designed to examine volatile organic compound (VOC) diffusion through geosynthetic clay liners (GCLs) are described, together with procedures for evaluating the relevant diffusion and sorption parameters. Test results show that the rate of contaminant migration proceeded through the hydrated GCL in the decreasing order of DCM and DCA > benzene > TCE and toluene. This was attributed to varying degrees of sorption of DCA, benzene, TCE and toluene to the geotextile component of the GCL as well as to the bentonite present in the GCL. Diffusion coefficients deduced from VOC diffusion testing conducted on the GCLs at confining pressures lower than approximately 10 kPa range from 2 × 10^–10 m²/s to 3 × 10^–10 m²/s. This is generally lower than those reported in the literature for compacted clay liner materials. Assessments of the environmental protection afforded by a landfill liner require that all underlying soil and geosynthetics components be considered in landfill contaminant migration assessments. The results in this paper provide some of the first published data for laboratory GCL diffusion and sorption coefficients, required to perform contaminant migration assessments for five VOC contaminants commonly found in municipal solid waste leachate.