The detection of low volatility organic compounds in the gas-phase from the OH-initiated oxidation of isoprene in chamber air and its relevance to organic aerosol production

Jordan Krechmer1, Matthew Mitchell Coggon2, John B Nowak3, Joel Kimmel4, Harald Stark5, Paola Massoli4, Lee Mauldin6, John Toulson Jayne7, John D Crounse8, Tran B Nguyen9, Paul O Wennberg10, John Seinfeld11, Douglas R Worsnop4, Jose L Jimenez12 and Manjula R Canagaratna13, (1)University of Colorado at Boulder, Boulder, United States, (2)National Oceanic and Atmospheric Administration/U.S. Department of Commerce operative Institute for Research in Environmental Sciences/Chemical Sciences Division Boulder 80309 (United States), Chemical Sciences Division, Boulder, United States, (3)NASA Langley Research Center, Hampton, VA, United States, (4)Aerodyne Research Inc., Billerica, MA, United States, (5)University of Colorado at Boulder, Cooperative Institute for Research in Environmental Sciences (CIRES) and Department of Chemistry, Boulder, United States, (6)University of Colorado at Boulder, Boulder, CO, United States, (7)Aerodyne Research Inc., Billerica, United States, (8)California Institute of Technology, Pasadena, CA, United States, (9)California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, United States, (10)California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, United States, (11)California Institute of Technology, Department of Chemical Engineering, Pasadena, United States, (12)Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder, Boulder, United States, (13)Aerodyne Research, Inc., Billerica, MA, United States
Abstract:
Low volatility organic compounds from the oxidation of isoprene have been observed under a variety of conditions during the FIXCIT atmospheric chamber study at Caltech in January of 2014. Data were obtained using a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) equipped with a nitrate-ion (NO3‑) source. The observed species, detected as clusters with the nitrate ion (m/z 62), range in elemental mass from approximately m/z 120-220 and span an elemental oxygen to elemental carbon ratio (O:C) range of 0.4 to 2.0. Using calibrations for simulant compounds obtained through subsequent laboratory studies, some of these highly oxidized isoprene products were quantified and their loadings and estimated production will be presented here. Ammonium sulfate aerosol seeds were injected into the chamber during several experiments, which enabled further investigation of the contribution of highly oxidized isoprene products to secondary organic aerosol (SOA) growth under a range of experimental conditions representative of the atmosphere where biogenic SOA has been shown to be an important contribution to submicron aerosol. Similar data were also obtained for oxidized species generated by the oxidation of semi-volatile isoprene products including isoprene hydroxyperoxide (ISOPOOH) and methacrolein (MACR) to further investigate mechanisms for isoprene oxidation and SOA formation. Measurements of these species’ uptake to chamber walls and seed aerosol will also be presented.
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