Analysis of Colloid Enhanced Contaminant Transport in Sets of Parallel Fractures with Fracture Skin

Groundwater often contains significant populations of natural colloids as well as waste- and repository-derived colloids that may interact with pollutants and influence their transport. A triple continuum one-dimensional transport model is developed to analyze radioactive contaminant transport in the presence of colloids in fractured geological formations. The model accounts for contaminant transport in the fracture, reversible deposition onto fracture surfaces and onto the colloids, diffusion into the rock formation, and irreversible deposition of colloids onto the fracture surfaces. Sorption of the contaminant onto the fracture surfaces and onto suspended and deposited colloids are assumed to follow the linear equilibrium assumption (LEA), whereas the irreversible deposition of colloids onto the fracture skin surface is assumed to be governed by the linear kinetic sorption isotherms. The model also accounts for penetration of colloids into the rock formation. A fully implicit finite difference method-based formulation is employed for solving the numerical model. The impact of different colloid parameters on contaminant transport is investigated. Results clearly demonstrate that the distribution coefficient for contaminant sorption onto the suspended colloids is found to be the most significant colloid-related parameter influencing radioactive contaminant migration in fractured formation with fracture skin.