The Program supports research on the sources, sinks, transport, and transformation of gases and aerosols in the atmosphere through models, observations, and experiments, including homogeneous and heterogeneous chemical reactions, emissions, deposition, atmospheric oxidation and photochemistry, aqueous-phase chemistry and aerosol processes; the formation of new particles and secondary organic aerosols, the modeling of atmospheric chemical processes, the study of chemical mechanisms in the atmosphere, optical properties of gases an...