AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Chemical Characterization of Secondary Organic Aerosol from Oxidation of Isoprene Hydroxyhydroperoxides
Matthieu Riva, Sri Hapsari Budisulistiorini, Yuzhi Chen, Zhenfa Zhang, Avram Gold, Joel A. Thornton, Manjula Canagaratna, JASON SURRATT, University of North Carolina at Chapel Hill
Abstract Number: 134 Working Group: Aerosol Chemistry
Abstract Atmospheric oxidation of isoprene under low-NOx conditions leads to the formation of isoprene hydroxyhydroperoxides (ISOPOOH). Subsequent oxidation of ISOPOOH produces largely isoprene epoxydiols (IEPOX), which are known secondary organic aerosol (SOA) precursors. Although SOA from IEPOX has been previously investigated, systematic studies of SOA formation through a non-IEPOX route from ISOPOOH oxidation are lacking.
In the present work, SOA formation from the oxidation of authentic 1,2-ISOPOOH under low-NOx conditions was systematically examined with varying seed aerosol compositions and relative humidity in an indoor smog chamber. Chemical characterization of SOA was investigated using ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-QTOFMS) and gas chromatography interfaced with electron ionization mass spectrometry (GC/EI-MS) with prior trimethylsilylation. High yields of highly oxidized compounds, including multifunctional organosulfates (OSs) and hydroperoxides, were chemically characterized in both laboratory-generated SOA and fine aerosol samples collected from the southeastern U.S. IEPOX-derived SOA constituents were observed in all experiments, but their concentrations were only enhanced in the presence of acidified sulfate aerosol, consistent with prior work. High-resolution aerosol mass spectrometry (HR-AMS) reveals that 1,2-ISOPOOH-derived SOA formed through non-IEPOX routes exhibits a unique mass spectrum with a characteristic fragment ion at m/z 91. This laboratory-generated mass spectrum is strongly correlated with the 91Fac recently resolved by positive matrix factorization (PMF) of Aerosol Chemical Speciation Monitor (ACSM) data collected in areas dominated by isoprene emissions, suggesting that ISOPOOH oxidation could contribute to ambient SOA measured in the southeastern United States.