AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, 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, Tashana Detwiler, Zhenfa Zhang, Avram Gold, Jason Surratt, University of North Carolina at Chapel Hill, Chapel Hill, NC
Abstract Number: 619 Working Group: Aerosol Chemistry
Abstract Atmospheric aerosols are critical in many environmental processes and can adversely affect the global climate and human health. It is now recognized that the largest mass fraction (20–90%) of atmospheric fine particles (PM2.5) is generally organic, and is 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. Prior studies have demonstrated the formation of SOA arising from its photooxidation. Most of these studies have been 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. Isoprene ozonolysis is less documented and only partial mechanisms are currently proposed. Recently, one study demonstrated the presence of oligomer products in the particle phase but the mechanism to explain the formation of these compounds remains unclear. Moreover, the explanation of the SOA formation from nucleation arising from isoprene ozonolysis remains unknown.
Therefore, in this work we explored SOA formation from isoprene ozonolysis. Experiments were conducted in an indoor smog chamber facility at room temperature. Gas phase characterization was performed using high-resolution time-of-flight chemical ionization mass spectrometry (HRToF-CIMS) equipped with acetate reagent ions. SOA chemical characterization was investigated using ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-ToFMS) and gas chromatography interfaced with electron ionization mass spectrometry (GC/EI-MS) with prior trimethylsilylation. Impact of environmental conditions (OH radicals, aerosol acidity, seed particle composition) on SOA formation arising from isoprene ozonolysis have been investigated and new insights on the chemical mechanism are proposed.