Atmospheric Chemical Reactions of Aerosols with Biogenic Derived Epoxides

Science Center, Bent Corridor

Due to industrial emissions of sulfur-containing compounds, atmospheric aerosols have become more enriched in sulfuric acid, and their corresponding influence on their atmospheric chemical reactions with natural oxidized biogenic compounds is not fully understood. Using nuclear magnetic resonance (NMR) techniques, aqueous phase reactions of the epoxide beta pinene oxide (β-PO) on different aerosols were studied, with a focus on the rates of the reactions and on identification of the products formed. Different aerosol environments were mimicked: 1.) pure water, the simplest potential form of an aerosol, 2.) 1 M sulfuric acid (representing an aerosol with a higher acid concentration). Similarly to alpha pinene oxide (α-PO), the rate constant was too fast to measure in both aerosol environments and thus the atmospheric lifetime is estimated to be less than 5 minutes. However, an increase in acidity changes the proportions of the products formed, and thus it is assumed that as human induced pollutants increase, the products formed will deviate from a “natural” distribution, forming such “unnatural” products as organosulfates. Lastly, organosulfate formation and their hydrolysis kinetics were studied in detail. Like α-PO, β-PO forms the potentially toxic organosulfate compound, which then hydrolyzes quickly into the main product formed when no sulfuric acid is present. Four experiments with varying sulfate concentrations were performed. As the sulfate concentration was increased, the organosulfate hydrolyzed faster.