One-dimensional transport of transient diffusion-advection of organic contaminant through composite liners

Using the fully transient diffusion-advection transport model for transport of organic contaminant in GMB/GCL/SL composite liner, a series of parameter sensitivity studies are conducted to analyze the influences of several important parameters on the barrier performance of the composite liner. The results show that: (1) When the leachate head is 10, 5, 3 and 0.3 m, the breakthrough time obtained by the full advection model is higher by 233%, 151%, 111% and 24% than that obtained by the local advection model, respectively. (2) It is appropriate to use h_w as an alternative for h_d for simplification. (3) The breakthrough time of the composite liner with f-HDPE geomembrane is 36%, 33% and 22% higher than that with PVC, LLDPE and HDPE, respectively. (4) When the leachate head is 10, 5 and 1 m, the breakthrough time will be overestimated due to ignoring the effects of advection by 68%, 34% and 6%, respectively. (5) When the frequency of holes increases from 2.5 to 50, 30, 10 and 5 ha^-1, the breakthrough time decreases by 54%, 41%, 16% and 6%, respectively. (6) The effective diffusion coefficient of SL decreases by 90%, and the breakthrough time of the liner increases by 2 ~ 6 times. The adsorption coefficient of SL increases from 1 mL/g to 5, 15, 30 and 50 mL/g, and the breakthrough time increases by 311%, 1086%, 2249% and 3798%, respectively. The above research results may provide some reference and suggestions for the use and improvement of the liner in practice.