Interpretative analysis of data for solute transport in the unsaturated zone

In this report, the movement of iodide, bromide, and lithium under unsaturated flow conditions is modeled using the computer code CFITIM. This code is a solution of the one-dimensional convective-dispersive equation when steady-state flow exists and when interactions between the solute and Bandelier tuff can be described by the linear isotherm. The model predicts well the transport of the solutes iodide, bromide, and lithium when flow conditions are near steady-state. When assuming average steady-state flow conditions, the model predicts dispersion factors for unsteady flow within one to two orders of magnitude of the predictions at steady-state flow; retardation factors, on the other hand, are predicted much better than the dispersion factors. Differences in the estimated dispersion coefficients for solutes of two steady-state pulses indicate that the intended replication of those steady-state flow pulses was not achieved during experimentation. A comparison of breakthrough curves of solutes from one depth to another in the 3-m x 6-m field experimental caisson indicates poor conservation of solute mass during transport