Solute transport in porous media is essential for understanding processes such as contaminant transport and chemical reactions in subsurface hydrology. In groundwater systems, solute transport characteristics are highly controlled by water content and pore heterogeneity resulting in distinct patterns in unsaturated conditions, where miscible and non-miscible phases coexist in the pore space, compared to saturated conditions.
Under unsaturated conditions, characterizing solute transport is challenging due to the spatial distribution of the two phases. This spatial arrangement of the phases lead to unpredictable transport behavior that requires capturing the spatiotemporal flow dynamics for accurate predictions.

In this work, our aim is to quantify the impact of saturation and heterogeneity on solute transport. We performed 3D transport experiments by injecting a potassium iodide (KI) tracer solution into a glass-bead-packed column. The experiments were conducted with different degrees of saturation under steady-state conditions. We used X-ray synchrotron microcomputed tomography and image processing techniques to visualize and assess KI transport behavior through the porous medium. Preliminary results from the 3D data, show that under both saturated and unsaturated conditions, solute transport characteristics exhibit anomalous (non-fickian) behavior. As expected, under unsaturated conditions, the results reveal a greater degree of flow heterogeneity and increased solute dispersion.