TRIPLE-POROSITY ANALYSIS OF SOLUTE TRANSPORT

As an extension to the traditional dual-porosity approach, a triple-po rosity model is presented to study the solute transport in heterogeneo us porous media where the transport processes are distinctly different between macropores, mesopores and micropores. The distinctions in ter ms of conductance and storage in the respective pore domain are charac terized by the fact that: (a) macropores are primary Bow paths where b oth dispersion and convection are prevalent; (b) mesopores are interme diate flow paths where convection becomes dominant and (c) micropores are supplemental flow paths and mass storage spaces where only diffusi ve flow is manifested. In cascading coupling, the solute interchange b etween micropores and mesopores is maintained by assuming micropore di ffusion as internal sources (sinks) attached to mesopore skins. A comp rehensive solute exchange between macropores and mesopores is preserve d. A mathematical model is constructed in accordance with the physical conceptualization. The coupled partial differential equations are sol ved in a one-dimensional geometry using Laplace transform, and the sub sequent coupled ordinary differential equations are circumvented via t he method of differential operators. Semi-analytical solutions are obt ained. (C) 1997 Elsevier Science B.V.