NUMERICAL-SIMULATION OF CHEMICAL MIGRATION IN PHYSICALLY AND CHEMICALLY HETEROGENEOUS POROUS-MEDIA

A series of chemical transport simulations in saturated porous media are conducted to examine the coupled impacts on chemical mobility induced by nonuniform sorption reactions and heterogeneous flow fields. The simulations involve the calculation of fluid flow and chemical migration within highly resolved, three-dimensional cubic regions with synthetically derived material properties. Nonuniformities in subsurface materials are represented as randomly correlated hydraulic conductivity and sorption partition coefficient fields. Transport computations are based upon a random walk particle model, appropriately modified to treat equilibrium sorption reactions. Current experiments focus on four hypothetical constituents, one being inert, and the other three independently obeying linear, Freundlich, and Langmuir partitioning relationships. Results show distinct effects of the nonuniform flow and sorption processes on the overall displacement, dispersion, and partitioning/retardation and the breakthrough behavior of the constituent plumes, as well as on the sharpening fronts and skewed concentration profiles associated with nonlinear partitioning models.