MODELING THE TRANSPORT OF INORGANIC-IONS THROUGH UNDISTURBED SOIL COLUMNS FROM 2 CONTRASTING WATERSHEDS

The transport of several inorganic cations and anions via saturated flow, through large undisturbed soil columns from two contrasting watersheds was investigated. The mobility of nonreactive tracers was described well with the convection-dispersion (CD) equation using flux-averaged solute detection in the effluent. Reactive tracers were also modeled well using various linear and nonlinear, equilibrium and nonequilibrium, transport codes based on the CD equation. Appropriate independent estimates of model predicted chemical retardation were possible only through experimental development of 'dynamic isotherms' using a steady flow method on small undisturbed soil columns. The latter condition can accurately predict solute retardation on large soil columns, since tracer mmovement is largely controlled by the physical aspects of the soil (e.g., preferential flow zones).