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ii Chemical interactions that occur at the interface between two bulk isotropic media are vital to understand as these interactions dictate many fundamentally important phenomena influencing life on Earth as we know it. This dissertation presents investigations focused on elucidating behavior for the simple inorganic anion sulfate at a variety of environmentally relevant interfacial regimes, primarily mineral/solution interfaces. Sulfate is a ubiquitous anion in the environment that plays a key role in various physical and chemical phenomena. With perspective toward atmospheric chemistry, sulfate is a large component of aqueous acidic aerosols and has been shown to influence the reactivity and growth of these aerosols. Sulfate coatings have also been linked to the retardation of ice nucleation by mineral dust aerosols. Sulfate is also highly relevant to geochemical systems where it can inhibit, or encourage, aqueous contaminant uptake onto soil adsorption sites. This may lead to added complications when attempting to predict the spatial and temporal transport of aqueous contaminants within the environment. Work presented in this dissertation utilizes two different vibrational spectroscopic methods to probe sulfate behavior at the interfaces of interest. Chapter 2 presents studies harnessing vibrational sum frequency generation spectroscopy, an inherently interface specific spectroscopic technique, to investigate sulfate at the vapor/solution and the buried fluorite/solution interfaces. Results for the vapor/solution interface indicate that iii protonated sulfate, bisulfate (HSO4), features perturbed hydration compared to bulk solvated bisulfate. The presence of sodium (Na) and magnesium (M