MODELING CONTAMINANT MIGRATION WITH LINEAR SORPTION IN STRONGLY HETEROGENEOUS MEDIA

A triple-porosity model is presented to evaluate transport behavior in porous media with a structure comprising a spectrum of pore sizes, re presented discretely as macro-, meso-, and micropores. Characterizatio ns are completed to provide adequate semianalytical solutions for the validation of codes representing discrete distributions of pore geomet ry and to adequately describe extended tailing and multicomponent solu te front breakthroughs apparent in field and laboratory data. Semianal ytical solutions are derived for a one dimensional flow geometry by us ing Laplace transforms under the assumption that solute transport in t he two interactive mobile-transport regions (i.e., macro- and mesopore s) is affected by exchange with immobile solutes in the micropore regi on. Sensitivity analyses are conducted to identify the propensity for extensive tailing in the breakthrough response, over single-porosity a pproaches, and the development of multiple breakthrough fronts with re verse diffusion. Both behaviors result from the strongly heterogeneous nature of the transport processes, accommodated in the multiporosity model, and are well suited to the representation of ''real'' porous an d porous-fractured disordered media.