Articles | Volume 9, issue 14
Atmos. Chem. Phys., 9, 4945–4956, 2009
Atmos. Chem. Phys., 9, 4945–4956, 2009

  24 Jul 2009

24 Jul 2009

A product study of the isoprene+NO3 reaction

A. E. Perring1,*, A. Wisthaler2,*, M. Graus2, P. J. Wooldridge1, A. L. Lockwood4, L. H. Mielke4, P. B. Shepson3,4, A. Hansel2, and R. C. Cohen1,5 A. E. Perring et al.
  • 1Department of Chemistry, University of California Berkeley, Berkeley, CA, USA
  • 2Institut fuer Ionenphysik und Angewandte Physik, University of Innsbruck, Innsbruck, Austria
  • 3Purdue Climate Change Research Center, Purdue University, West Lafayette, IN, USA
  • 4Department of Chemistry, Purdue University, West Lafayette, IN, USA
  • 5Department of Earth and Planetary Sciences, University of California Berkeley, Berkeley, CA, USA
  • *equally contributing first authors

Abstract. Oxidation of isoprene through reaction with NO3 radicals is a significant sink for isoprene that persists after dark. The main products of the reaction are multifunctional nitrates. These nitrates constitute a significant NOx sink in the nocturnal boundary layer and they likely play an important role in formation of secondary organic aerosol. Products of the isoprene+NO3 reaction will, in many locations, be abundant enough to affect nighttime radical chemistry and to persist into daytime where they may represent a source of NOx. Product formation in the isoprene + NO3 reaction was studied in a smog chamber at Purdue University. Isoprene nitrates and other hydrocarbon products were observed using Proton Transfer Reaction-Mass Spectrometry (PTR-MS) and reactive nitrogen products were observed using Thermal Dissociation–Laser Induced Fluorescence (TD-LIF). The organic nitrate yield is found to be 65±12% of which the majority was nitrooxy carbonyls and the combined yield of methacrolein and methyl vinyl ketone (MACR+MVK) is found to be ∼10%. PTR-MS measurements of nitrooxy carbonyls and TD-LIF measurements of total organic nitrates agreed well. The PTR-MS also observed a series of minor oxidation products which were tentatively identified and their yields quantified These other oxidation products are used as additional constraints on the reaction mechanism.

Final-revised paper