Interactions of Nitrate Aerosols With Biogenic and Anthropogenic Organic Compounds

While a variety of recent studies have highlighted the interactions of gas phase organic compounds with sulfuric acid seed particles, there is far less known about their interactions with nitrate-containing particles. In the studies reported here, a variety of techniques have been used to examine the impact of organics on the chemistry, photochemistry and light-scattering properties of deliquesced nitrate aerosol particles. Alpha-pinene and naphthalene were chosen as representative of important biogenic and anthropogenic organics found in urban air. Nephelometer measurements combined with Mie scattering calculations have been used to examine the effects of these organics on the light-scattering properties of the aerosols in the dark as well as after irradiation. In addition, the morphology of the particles was examined using atomic force microscopy and the chemical composition of the particles analyzed using GC-MS. Mechanisms of interaction of the parent organics with the nitrate particles, including the potential for reactions at interfaces, and the atmospheric implications will be presented.