My research focuses on resolving fundamental chemical and physical processes in the troposphere and differentiating anthropogenic and natural influences. I am specifically interested in multiphase chemistry involving gases, aerosols, cloud droplets, and precipitation; oxidation processes; the impact of aerosols on the earth’s radiation balance and climate; biogeochemical interactions between ecosystems and the atmosphere; and the development of associated measurement techniques. I currently participate in several multi-institutional field programs in which atmospheric chemical constituents are measured at surface sites over long periods (years) and from ships and aircraft during shorter term (weeks) intensive campaigns. Data are interpreted using air-mass trajectories, various statistical techniques, and photochemical models.