Dispersion parameters for undisturbed partially saturated soil.

The advection-dispersion equation (ADE) does not necessarily provide a good description of solute transport in undisturbed soil cores and field plots, as a result of heterogeneities in pore water velocities related to variability in soil hydraulic properties, and non-equilibrium preferential flow and ‘immobile’ pore water effects. However, it is often used as a functional description of solute transport and this paper reviews the results of applying the ADE to undisturbed soil core and field plot experiments. Very wide ranges of dispersion coefficients and dispersivities have been found. Information available on the spatial variability of the solute transport parameters is also reviewed and suggests that local dispersion parameters may commonly be log normally distributed