Abstract：The mathematical model is developed for simulating the contaminant transport process of landfill in the compacted clay liner underlying a aquifer with a finite depth，in which effects of both waste bio-degradation and nonlinear sorption as well as first-order dynamic degradation of contaminants are considered. Through numerical computations，the effects of both physico-chemical reaction due to sorption of contaminants on soil skeletons and chemical reaction caused by first-order kinetic degradation of leachats on the contaminant migration processes are studied. A comparative study is made for different combinations of various parameters. It shows that nonlinear sorption and first-order kinetic bio-degradation of contaminants play significantly important roles in the transport of pollutants. Breakthrough curve of compacted clay liners tends to display the following features，(1) the front of the curve becomes sharper and narrower；(2) peak value is forward shifted with heavily unsymmetry with respect to the mass center；and (3) tailing gets longer. The maximum sorption capacity，which is given by factors K2 in Langmuir isothermal equation of sorption and mass density of soils，is used to represent the coupling effect of nonlinear sorption. It is demonstrated that this comprehensive parameter considerably affect the contaminant transport，and the hydraulic conductivity of compacted clay liner is a key factor for the governing migration of pollutants.
