Comparison of Heterogeneous Transport Processes Observed with Electrical Resistivity Tomography in Two Soils

Garre, S. Koestel, J. Guenther, T. Javaux, Mathieu [UCL] Vanderborght, J. Vereecken, H.

Preferential flow in soils can manifest itself in several ways. To illustrate this, we analyzed solute transport during a step tracer experiment in two soils expected to differ in their governing transport processes: a loamy sand and a silty soil. By combining electrical resistivity tomography (ERT), time domain reflectometry, and effluent measurements, we observed different preferential flow phenomena. The transport process was characterized using voxel- and column-scale effective convective-dispersive equation (CDE) parameters, local velocities, and leaching surfaces. At the column scale, transport in the loamy sand was dominated by a homogenous convective-dispersive transport behavior, but at the scale of the voxel, preferential transport was observed. Transport in the silty soil was considerably more heterogeneous. Preferential flow was identified using ERT, voxel- and column-scale effective CDE parameters, local velocities, and leaching surfaces. In these soils, a clear influence of soil layering on solute transport was observed.