AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Formation and Aerosol Uptake of the Oxidation Products of Isoprene Nitrooxyhydroperoxide (a Product of Isoprene Nighttime Chemistry)
REBECCA SCHWANTES, Tran Nguyen, Matthew Coggon, Katherine Schilling, Xuan Zhang, Paul Wennberg, John Seinfeld, Caltech
Abstract Number: 472 Working Group: Aerosol Chemistry
Abstract Isoprene (C5H8) reacts with the nitrate radical (NO3) during the night to produce a peroxy nitrate radical. This peroxy nitrate radical can react with nitrogen oxides (NO and NO2) and other peroxy radicals to form isoprene nitrates or with the hydroperoxyl radical (HO2) to form nitrooxyhydroperoxide. Both model [1] and field [2] studies have found that much of the peroxy nitrate radical reacts with HO2. However, chamber studies so far have been run in conditions that optimize the formation of isoprene nitrates rather than the formation of nitrooxyhydroperoxide. In this work, chamber studies designed specifically to study the nighttime HO2 pathway were conducted. The gas phase formation of the isoprene nitrooxyhydroperoxide and subsequent oxidation products were monitored using a chemical ionization mass spectrometer (CIMS). The gas phase oxidation products of the nitrooxyhydroperoxide will be discussed and compared to the products formed during the daytime oxidation of isoprene peroxide. Additionally, the aerosol uptake of the oxidation products of nitrooxyhydroperoxide onto both acidic and neutral seed under dry (RH <3%) and moderate relative humidity (RH ~ 50%) conditions was measured using a time-of-flight aerosol mass spectrometer (ToF-AMS). Off-line analyses of the aerosol produced were also conducted by electrospray ionization mass spectrometry (ESI-MS). The composition of the aerosol produced from the nighttime HO2 pathway will be discussed.
[1] Xie, Y., et al., Understanding the impact of recent advances in isoprene photooxidation on simulations of regional air quality, Atmos. Chem. Phys. Discuss., (In review)
[2] Beaver, M.R., et al., Importance of biogenic precursors to the budget of organic nitrates: observations of multifunctional organic nitrates by CIMS and TD-LIF during Bearpex 2009, Atmos. Chem. Phys., 12, 5773–5785, 2012.