AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Chemical Characterization of Gas- and Aerosol-Phase Products from Isoprene Ozonolysis in Presence of Acidic Aerosol: Re-examination of Secondary Organic Aerosol Formation
MATTHIEU RIVA, Sri Hapsari Budisulistiorini, Zhenfa Zhang, Avram Gold, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 110 Working Group: The Role of Water in Aerosol Chemistry
Abstract Atmospheric fine aerosols (PM2.5) are critical in many environmental processes. It is now recognized that the largest mass fraction of PM2.5 is generally organic, mostly dominated by secondary organic aerosol (SOA) formed from the oxidation of volatile organic compounds (VOCs). Isoprene is the most abundant non-methane hydrocarbon emitted into the Earth’s atmosphere and is derived from terrestrial vegetation. Most studies have focused on the hydroxyl radical (OH)-initiated oxidation of isoprene and have demonstrated that certain highly oxidized compounds, such as isoprene-derived epoxides, enhance the formation of SOA by heterogeneous reactions in a presence of acidified sulfate aerosol. Although less well documented, the contribution of isoprene ozonolysis to the SOA budget has been concluded to be negligible. However, the potential importance of isoprene ozonolysis as a pathway for SOA formation is supported by recent studies documenting the formation of highly oxidized products, including oligomers, in both gas and particulate phases.
In this work we explored SOA formation in an indoor smog chamber from isoprene ozonolysis under various conditions. Characterization of gas-phase components was performed using high-resolution time-of-flight chemical ionization mass spectrometry. Chemical characterization of SOA was investigated using ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry and gas chromatography interfaced with electron ionization mass spectrometry with prior trimethylsilylation. Insights have been gained from investigation of the influence of environmental conditions (OH radicals, aerosol acidity, seed particle composition, relative humidity) on SOA formation and composition and chemical mechanisms are proposed. Finally, organosulfates that have been identified as tracers in chamber experiments were also observed and quantified in summertime PM2.5 collected from two rural locations in the southeastern United States during the 2013 Southern Oxidant and Aerosol Study (SOAS).