Abstract View
Chemical Composition and Mass Yield of Secondary Organic Aerosol Generated from the Oxidation of Biogenic and Anthropogenic Precursors by Hydroxyl Radicals, Chlorine Atoms, and Bromine Atoms
ANDREW LAMBE, Anita Avery, Harald Stark, Jordan Krechmer, Francesca Majluf, Manjula Canagaratna, Catherine Masoud, Nirvan Bhattacharyya, Mrinali Modi, Lea Hildebrandt Ruiz, William Brune, Aerodyne Research, Inc.
Abstract Number: 177
Working Group: Aerosol Chemistry
Abstract
The role of hydroxyl radicals (OH) as a daytime oxidant is well established on a global scale. In specific regions such as the marine boundary layer and polluted coastal cities, other daytime oxidants such as chlorine atoms (Cl) and even bromine atoms (Br) may compete with OH for the oxidation of volatile organic compounds. However, the number of chamber studies investigating halogen-initiated secondary organic aerosol (SOA) formation is extremely limited compared to the number of studies for OH, resulting in larger uncertainties in their oxidation mechanisms. To address these knowledge gaps, we characterized the chemical composition and yield of laboratory SOA generated in an oxidation flow reactor (OFR) from the OH and Cl oxidation of toluene and n-dodecane, and the OH, Cl, and Br oxidation of isoprene and α-pinene. In the OFR, precursors were oxidized using OH (5×108 to 2×1010 cm-3), Cl (5×107 to 2×109 cm-3), or Br (3×109 to 3×1010 cm-3) over exposure times of approximately 2 min. SOA mass spectra and yields obtained in the OFR studies were comparable to those obtained from OH and Cl oxidation of the same precursors in environmental chamber studies. Results suggest that specific precursor classes such as alkane, aromatic, and terpenoid SOA precursors are characterized by distinct OH- and halogen-initiated SOA yields.