Engineered nanoparticles (e.g., TiO₂) have been widely used in various industrial applications. However, due to their reported toxic effects to the environment, the release of nanoparticles into soils and groundwater has become a potential environmental risk.  Transport of nanoparticles in saturated porous media has been well documented in the literature but the effect of solution chemistry (e.g., pH, ionic strength, and organic matter) on their mobility has been overlooked. Therefore, this study focuses on the transport and mobility of a model metal oxide nanoparticle (nano-TiO2), prepared with different solution pH or ionic strengths, in porous media. The nanoparticle suspensions were applied to laboratory columns packed with quartz sand to compare their motilities. In addition, the effect of natural organic matter on nano-TiO2 transport in porous media was investigated. Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and a colloid transport model were used to aid in the data interpretation.