Two‐Dimensional Modeling of Colloid‐Facilitated Contaminant Transport in Groundwater Flow Systems With Stagnant Zones

Abstract

AbstractA mathematical model has been developed for the contaminant transport with colloids in groundwater flow systems with stagnant zones to investigate the effect of stagnant zones on the transport of contaminants with colloids. In the present study, colloids and contaminants are supposed to drift via two coexisting homogeneous regions. The critical limitation of the mobile‐immobile (MIM) model is to deal with the number of parameters used upon application to larger scales for both mobile and immobile regions when a series of transport mechanisms are involved. Therefore, the present model is the first attempt model of the equilibrium approach for mobile‐immobile regions to avoid complexities in the model. The present study includes the effect of the stagnant zone on the plume movement in mobile regions for steady‐state flow conditions, and it is discerned that the plume moves faster in the presence of immobile regions. However, when dispersion, velocity, and pulse duration are decreased, tailing is noticed in the breakthrough profiles. Stagnant regions enhance the transport of contaminants in the porous media and produce augmented breakthrough curves by increasing the velocity in the mobile regions where colloids and contaminants migrate simultaneously. The transport of contaminants can be enhanced in the presence of colloids. However, sensitivity analyses indicate that the combination of different distribution coefficients controls the mobility of contaminants even in the presence of colloids. The proposed model has been validated using experimental data of the single‐porosity model in the presence of colloids and the MIM model in the absence of colloids.