SIMILARITY AND DIFFERENCE BETWEEN CONTAMINANT TRANSPORT IN FRACTURE-ROCK MATRIX AND AQUIFER-AQUITARD SYSTEMS

Conceptual models of contaminant transport in an aquifer-aquitard system are often borrowed from those built for a fracture-rock matrix system. A primary assumption that is often adopted in the analytical approaches of such problems is to treat the mass transfer between the aquifer and aquitard as a thickness-averaged sink/source term in the governing equation of transport in the aquifer. This study analyzes the similarity and difference of contaminant transport in a fracture-rock matrix system and an aquifer-aquitard system and suggests that the thickness-averaged treatment may work for a fracture-rock matrix system, but usually fail for the aquifer-aquitard system in which the mass transfer should be specifically treated as a boundary effect between the aquifer and aquitard. This study also discusses the aquitard leakage effect on transport in an aquifer-aquitard system.