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

A series of chemical transport simulations in saturated porous media a re conducted to examine the coupled impacts on chemical mobility induc ed by nonuniform sorption reactions and heterogeneous flow fields. The simulations involve the calculation of fluid flow and chemical migrat ion within highly resolved, three-dimensional cubic regions with synth etically derived material properties. Nonuniformities in subsurface ma terials 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 tre at equilibrium sorption reactions. Current experiments focus on four h ypothetical constituents, one being inert, and the other three indepen dently obeying linear, Freundlich, and Langmuir partitioning relations hips. Results show distinct effects of the nonuniform flow and sorptio n processes on the overall displacement, dispersion, and partitioning/ retardation and the breakthrough behavior of the constituent plumes, a s well as on the sharpening fronts and skewed concentration profiles a ssociated with nonlinear partitioning models.