Numerical modeling of contaminant transport in a stratified heterogeneous aquifer with dipping anisotropy

Abstract

The combined influence of dip angle and adsorption heterogeneity on solute transport mechanisms in heterogeneous media can be understood by performing simulations of steady-state flow and transient transport in a heterogeneous aquifer with dipping anisotropy. Reactive and non-reactive contaminant transport in various types of heterogeneous aquifer is studied by simulations. The hydraulic conductivity (K) of the heterogeneous aquifer is generated by HYDRO_GEN with a Gaussian correla- tion spectrum. By considering the heterogeneity of the adsorption distribution coefficient (Kd), a perfect negative correlation between lnK and lnKd is obtained by using the spherical grains model. The generated K and Kd are used as input to groundwater flow and transport models to investigate the effects of dipping sedimentary heterogene- ity on contaminant plume evolution. Simulation results showed that the magnitude of the dip angle strongly controls the plume evolution in the studied anisotropic and heterogeneous aquifer. The retarded average pore-water velocity (v/R) of the adsorption model significantly controls the horizontal spreading of the plume. The bottom plume is intensively retarded in the zones between the dipping lenses of lower hydraulic conductivity and the no-flow bottom boundary. The implications of these findings are very important for the management of contaminated heterogeneous aquifers.