Understanding the mechanisms controlling colloid transport and deposition in partially saturated natural and engineered systems is an important step in protecting water resources and the environment, as well as optimizing engineered processes. Not only may these particles themselves be undesirable contaminants or clogging agents, but they can also aid in the transport of smaller, molecular-scale contaminants by chemical attachment. In this research, we examined the influence that air-water interfaces (AWI) and air-water-solid contact lines (AWS) have on colloid deposition and mobilization in three-dimensional systems. We used x-ray microtomography to visualize the transport of hydrophobic colloids as they move through a partially saturated glass bead pack.