A two-dimensional analytical model for organic contaminants transport in a transition layer-cutoff wall-aquifer system

Cutoff walls are widely used as in-situ vertical barriers to control pollution plumes migration in aquifer. A twodimensional analytical model for the transport of organic contaminants through a layered subsurface system with a cutoff wall is developed. The model considers a coupled advection-dispersion-adsorption-degradation process in the whole system and a non-uniform concentration distribution of a contaminant source with respect to depth. The solution was effectively validated against a one-dimensional analytical solution and a two-dimensional numerical solution. The migration behavior of contaminants in the triple-layer system and the service performance of a cutoff wall are investigated. It is demonstrated that the previous one-dimensional contaminant migration solution would underestimate the polluted ranges but overestimate the migration distance. The consideration of a non-uniformly distributed contamination source is of great importance, especially for narrowly contaminated aquifer. The biodegradation in a cutoff wall has a significant influence on the transport of an organic contaminant through the layered system when its half-life in the cutoff wall is less than 5 years, and this effect would be enhanced when the biodegradation in natural soil is also considered. The proposed model is a practical tool for performing a comprehensive design of the location and thickness of a cutoff wall.