Concentration Profiles and Spatial Moments for Reactive Transport through Porous Media

Abstract

We use an advection-dispersion-reaction equation, which accounts for both physical and chemical nonequilibrium, to study the effect of heterogeneity of the porous media on a spatial concentration profile. Distance-dependent and time-dependent dispersivity is used to account for the heterogeneity. A sensitivity analysis has been performed to illustrate the effect of various factors on breakthrough curves for reactive transport through homogeneous porous media. An exponential function for the dispersion coefficient is used to simulate experimental data for spatial moments of nonreactive and reactive chemicals. An implicit finite-difference method has been used for the numerical solution of the governing equations. The distance-dependent dispersion coefficient resulted in higher peak value of concentration than the equivalent time-dependent dispersion coefficient. With an increase in time, the spatial concentration profile is steeper for the distance-dependent dispersion coefficient. Experimental data of spatial moments for two-dimensional reactive and nonreactive transport through heterogeneous porous media are simulated well with the exponential dispersivity function. The present model is simpler than the stochastic analytical method and more efficient than the numerical solution using the Monte-Carlo method multiple realizations need not be simulated.