Organic nitrate aerosol formation via NO3 + biogenic volatile organic compounds in the southeastern United States
B. R. Ayres1,H. M. Allen1,2,D. C. Draper1,3,S. S. Brown4,R. J. Wild4,J. L. Jimenez5,6,D. A. Day5,6,P. Campuzano-Jost5,6,W. Hu5,6,J. de Gouw5,6,A. Koss5,6,R. C. Cohen7,K. C. Duffey7,P. Romer7,K. Baumann8,E. Edgerton8,S. Takahama9,J. A. Thornton10,B. H. Lee10,F. D. Lopez-Hilfiker10,C. Mohr10,11,P. O. Wennberg12,T. B. Nguyen12,A. Teng12,A. H. Goldstein13,K. Olson13,and J. L. Fry1B. R. Ayres et al.B. R. Ayres1,H. M. Allen1,2,D. C. Draper1,3,S. S. Brown4,R. J. Wild4,J. L. Jimenez5,6,D. A. Day5,6,P. Campuzano-Jost5,6,W. Hu5,6,J. de Gouw5,6,A. Koss5,6,R. C. Cohen7,K. C. Duffey7,P. Romer7,K. Baumann8,E. Edgerton8,S. Takahama9,J. A. Thornton10,B. H. Lee10,F. D. Lopez-Hilfiker10,C. Mohr10,11,P. O. Wennberg12,T. B. Nguyen12,A. Teng12,A. H. Goldstein13,K. Olson13,and J. L. Fry1
Received: 12 May 2015 – Discussion started: 16 Jun 2015 – Revised: 26 Oct 2015 – Accepted: 14 Nov 2015 – Published: 03 Dec 2015
Abstract. Gas- and aerosol-phase measurements of oxidants, biogenic volatile organic compounds (BVOCs) and organic nitrates made during the Southern Oxidant and Aerosol Study (SOAS campaign, Summer 2013) in central Alabama show that a nitrate radical (NO3) reaction with monoterpenes leads to significant secondary aerosol formation. Cumulative losses of NO3 to terpenes are correlated with increase in gas- and aerosol-organic nitrate concentrations made during the campaign. Correlation of NO3 radical consumption to organic nitrate aerosol formation as measured by aerosol mass spectrometry and thermal dissociation laser-induced fluorescence suggests a molar yield of aerosol-phase monoterpene nitrates of 23–44 %. Compounds observed via chemical ionization mass spectrometry (CIMS) are correlated to predicted nitrate loss to BVOCs and show C10H17NO5, likely a hydroperoxy nitrate, is a major nitrate-oxidized terpene product being incorporated into aerosols. The comparable isoprene product C5H9NO5 was observed to contribute less than 1 % of the total organic nitrate in the aerosol phase and correlations show that it is principally a gas-phase product from nitrate oxidation of isoprene. Organic nitrates comprise between 30 and 45 % of the NOy budget during SOAS. Inorganic nitrates were also monitored and showed that during incidents of increased coarse-mode mineral dust, HNO3 uptake produced nitrate aerosol mass loading at a rate comparable to that of organic nitrate produced via NO3 + BVOCs.
This paper reports atmospheric gas- and aerosol-phase field measurements from the southeastern United States in summer 2013 to demonstrate that the oxidation of biogenic volatile organic compounds by nitrate radical produces a substantial amount of secondary organic aerosol in this region. This process, driven largely by monoterpenes, results in a comparable aerosol nitrate production rate to inorganic nitrate formation by heterogeneous uptake of HNO3 onto dust particles.
This paper reports atmospheric gas- and aerosol-phase field measurements from the southeastern...