ABSTRACT
The dispersion of contaminant also involves a mixing and spreading of the contaminant due to nonhomogeneity in the aquifer (Freeze and Cherry, 1979). Although this mechanism is totally different from the diffusion process, for most practical purposes, it can be mathematically modeled in the same way; hence the two processes are often lumped together as a composite parameter, D, called the coefficient of hydrodynamic dispersion:
D = De + Dmd (1.7) where De is the effective (molecular) diffusion coefficient for the contaminant species of interest [12T-1]; Dmd is the coefficient of mechanical dispersion [cri].
