10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Effects of Criegee Intermediate Scavenger on Secondary Organic Aerosol Formation during α-pinene Ozonolysis
KEI SATO, Shinichi Enami, Sathiyamurthi Ramasamy, Satoshi Inomata, Takashi Imamura, National Institute for Environmental Studies, Japan
Abstract Number: 429 Working Group: Aerosol Chemistry
Abstract Criegee intermediates (CI) might contribute to formation of low-volatility organic compounds such as dimers in the atmosphere. We used a laboratory environmental chamber to investigate the effects of CI scavengers on secondary organic aerosol (SOA) formation from α-pinene ozonolysis in the presence of OH radical scavenger. We used formic acid and heptanoic acid as the CI scavengers, and used carbon monoxide as the OH radical scavenger. Experiments were conducted under dry conditions (RH < 0.1%). Gaseous compounds were measured by FT-IR, and the chemical composition of SOA was measured by AMS. The SOA mass concentrations measured after the consumption of 0.1-ppm α-pinene in the experiments with heptanoic acid (262–275 μg m-3) were higher than those measured with formic acid (189–196 μg m-3) and without a CI scavenger (202–216 μg m-3). The O:C ratios measured for SOA in experiments with heptanoic acid (0.27–0.29) were lower than those measured with formic acid (0.31–0.36) and without CI scavenger (0.30–0.35). We also studied the addition effect of ammonium sulfate seed particles. Similar results were obtained in the presence of seed particles, but the SOA concentrations measured with seed particles are slightly higher than those measured without seed particles. The CIs formed from α-pinene ozonolysis react not only with α-pinene oxidation products but also heptanoic acid. The reactions of the CIs with heptanoic acid would result in formation of the SOA with O:C ratios lower than those formed during α-pinene ozonolysis.