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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 16
Atmos. Chem. Phys., 18, 11663-11682, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Atmos. Chem. Phys., 18, 11663-11682, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 16 Aug 2018

Research article | 16 Aug 2018

Secondary organic aerosol (SOA) yields from NO3 radical + isoprene based on nighttime aircraft power plant plume transects

Juliane L. Fry1, Steven S. Brown2,5, Ann M. Middlebrook2, Peter M. Edwards2,3,4, Pedro Campuzano-Jost3,5, Douglas A. Day3,5, José L. Jimenez3,5, Hannah M. Allen6, Thomas B. Ryerson2, Ilana Pollack2,3,a, Martin Graus3,b, Carsten Warneke2,3, Joost A. de Gouw3,5, Charles A. Brock2, Jessica Gilman2,3, Brian M. Lerner2,3,c, William P. Dubé2,3, Jin Liao2,3,d, and André Welti2,3,e Juliane L. Fry et al.
  • 1Chemistry Department, Reed College, Portland, OR, USA
  • 2Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
  • 3Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
  • 4Department of Chemistry, Wolfson Atmospheric Chemistry Laboratories, University of York, York, UK
  • 5Department of Chemistry, University of Colorado, Boulder, CO, USA
  • 6Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
  • anow at: Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA
  • bnow at: Department of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria
  • cnow at: Aerodyne Research, Inc., Billerica, MA, USA
  • dnow at: Universities Space Research Association, Columbia, MD, USA and NASA Goddard Space Flight Center, Atmospheric Chemistry and Dynamic Laboratory, Greenbelt, MD, USA
  • enow at: Leibniz Institute for Tropospheric Research, Department of Physics, Leipzig, Germany

Abstract. Nighttime reaction of nitrate radicals (NO3) with biogenic volatile organic compounds (BVOC) has been proposed as a potentially important but also highly uncertain source of secondary organic aerosol (SOA). The southeastern United States has both high BVOC and nitrogen oxide (NOx) emissions, resulting in a large model-predicted NO3-BVOC source of SOA. Coal-fired power plants in this region constitute substantial NOx emissions point sources into a nighttime atmosphere characterized by high regionally widespread concentrations of isoprene. In this paper, we exploit nighttime aircraft observations of these power plant plumes, in which NO3 radicals rapidly remove isoprene, to obtain field-based estimates of the secondary organic aerosol yield from NO3+isoprene. Observed in-plume increases in nitrate aerosol are consistent with organic nitrate aerosol production from NO3+isoprene, and these are used to determine molar SOA yields, for which the average over nine plumes is 9% (±5%). Corresponding mass yields depend on the assumed molecular formula for isoprene-NO3-SOA, but the average over nine plumes is 27% (±14%), on average larger than those previously measured in chamber studies (12%–14% mass yield as ΔOAΔVOC after oxidation of both double bonds). Yields are larger for longer plume ages. This suggests that ambient aging processes lead more effectively to condensable material than typical chamber conditions allow. We discuss potential mechanistic explanations for this difference, including longer ambient peroxy radical lifetimes and heterogeneous reactions of NO3-isoprene gas phase products. More in-depth studies are needed to better understand the aerosol yield and oxidation mechanism of NO3 radical+isoprene, a coupled anthropogenic–biogenic source of SOA that may be regionally significant.

Publications Copernicus
Short summary
This paper uses measurements made during research aircraft flights through power plant smokestack emissions plumes as a natural laboratory in the field experiment. We investigated a specific source of airborne particulate matter from the combination of human-produced NOx pollutant emissions (the smokestack plumes) with isoprene emitted by naturally by trees in the southeastern United States. These field-based yields appear to be higher than those typically measured in chamber studies.
This paper uses measurements made during research aircraft flights through power plant...