The Atmospheric Chemistry Laboratory investigates the origins of atmospheric pollution and evaluates its environmental impacts. Since many pollutants, such as ground-level ozone, are formed directly in the atmosphere through a sequence of complex chemical and physical processes, an understanding of these processes is required to develop appropriate control measures for pollution prevention. The two ongoing research projects in our lab focus on atmospheric aerosols and atmospheric mercury. Atmospheric aerosols originate from direct particle emissions and also from gas-to-particle conversion. We study how atmospheric aerosols form and evolve, and also assess the impacts of aerosols on the climate and human health. We conduct experiments to investigate the atmospheric processing of combustion-generated soot particles and the relationship between particle morphology and optics. Additionally, we develop hyphenated mass-spectrometry instrumentation for chemical analysis of aerosol particles and their gas-phase precursors. The goal of our mercury project is to understand the chemistry and speciation of this persistent, bioaccumulative pollutant emitted to the atmosphere in large quantities by coal- fired power plants. We study gas-phase oxidation of mercury and its interactions with atmospheric surfaces, and we also develop new detection techniques for atmospheric oxidized mercury based on chemical ionization mass spectrometry.