Influence of colloid and adsorption parameters on contaminant transport in fractured rocks - A triple continuum model

Contaminant transport in fractured formations is strongly affected by the presence of fracture skin in the rock matrix. A triple continuum solute transport model is developed, incorporating the fracture skin as the third continuum, besides the fracture and the rock matrix, to describe the colloid facilitated contaminant transport in fractured formations. Sorption of the contaminant onto suspended and deposited colloids is assumed to follow a modified Freundlich reversible equilibrium isotherm. The resulting set of governing partial differential equations is solved using a fully implicit finite difference method. The distribution coefficient for contaminant sorption onto the deposited colloids and isotherm fitting parameter for contaminant sorption onto the deposited colloids are shown to be the most critical colloid related parameter affecting the contaminant transport in fractured media in presence of colloids. Furthermore, it is demonstrated that contaminant migration in fractured media is greatly affected by the presence of previously deposited colloids on fracture surfaces.