The approach that we take in these studies is quite broad. In some cases, we make use of the pristine environment of an ultrahigh vacuum chamber to have complete control of the surface composition. In other cases, high surface area powdered samples and gas phase pressures on the order of atmospheric pressures are used. The different pressure regimes and techniques used depends upon the types of questions that we are trying to address and the techniques we use to answer these questions. Below lists the techniques that we use to probe the chemistry of environmental surfaces including those of atmospheric particles (e.g. mineral dust, sea salt and soot) as well as nanoparticles (e.g. nanocrystalline zeolites 15 nm in diameter, TiO₂ particles that are 5nm). A brief description of these techniques is provided.