30 May 2022
30 May 2022
Status: this preprint is currently under review for the journal ACP.

Aerosol size distribution changes in FIREX-AQ biomass burning plumes: the impact of plume concentration on coagulation and OA condensation/evaporation

Nicole A. June1, Anna L. Hodshire2, Elizabeth B. Wiggins3, Edward L. Winstead3,4, Claire E. Robinson3,4, K. Lee Thornhill3,4, Kevin J. Sanchez3, Richard H. Moore3, Demetrios Pagonis5,6,a, Hongyu Guo5, Pedro Campuzano-Jost5, Jose L. Jimenez5,6, Matthew M. Coggon5,9, Jonathan M. Dean-Day7, T. Paul Bui8, Jeff Peischl5,9, Robert J. Yokelson10, Matthew J. Alvarado11, Sonia M. Kreidenweis1, Shantanu H. Jathar12, and Jeffrey R. Pierce1 Nicole A. June et al.
  • 1Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA
  • 2Handix Scientific, Fort Collins, CO, USA
  • 3NASA Langley Research Center, Hampton, VA, USA
  • 4Science Systems and Applications, Hampton, VA, USA
  • 5Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA
  • 6Department of Chemistry, University of Colorado, Boulder, CO, USA
  • 7Bay Area Environmental Research Institute, Moffett Field, CA, USA
  • 8Atmospheric Science Branch, NASA Ames Research Center, Moffett Field, CA, USA
  • 9NOAA Chemical Science Laboratory (CSL), Boulder, CO, USA
  • 10Department of Chemistry, University of Montana, Missoula, MT, USA
  • 11Verisk Atmospheric and Environmental Research, Lexington, MA, USA
  • 12Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, USA
  • anow at: Department of Chemistry, Weber State University, Ogden, UT, USA

Abstract. The evolution of organic aerosol (OA) and aerosol size distributions within smoke plumes are uncertain due to the variability in rates of coagulation and OA condensation/evaporation between different smoke plumes and at different locations within a single plume. We use aircraft data from the FIREX-AQ campaign to evaluate differences in evolving aerosol size distributions, OA, and oxygen to carbon ratios (O:C) between and within smoke plumes during the first several hours of aging as a function of smoke concentration. The observations show that the median particle diameter increases faster in smoke of a higher initial OA concentration (>1000 μg m-3) with diameter growth of over 100 nm in 8 hours–despite generally having a net decrease in OA enhancement ratios–than smoke of a lower initial OA concentration (<100 μg m-3), which had net increases in OA. Observations of OA and O:C suggest that evaporation and/or secondary OA formation was greater in less concentrated smoke prior to the first measurement (5–57 minutes after emission). We simulate the size changes due to coagulation and dilution and adjust for OA condensation/evaporation based on the observed changes in OA. We found that coagulation explains the majority of the diameter growth with OA evaporation/condensation having a relatively minor impact. We found that mixing between the core and edges of the plume generally occurred on timescales of hours, slow enough to maintain differences in aging between core-edge, but too fast to ignore the role of mixing for most of our cases.

Nicole A. June et al.

Status: open (until 11 Jul 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-349', Anonymous Referee #1, 20 Jun 2022 reply
  • RC2: 'Comment on acp-2022-349', Anonymous Referee #2, 23 Jun 2022 reply

Nicole A. June et al.

Nicole A. June et al.


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Short summary
The evolution of organic aerosol composition and size is uncertain due to variability within and between smoke plumes. We examine the impact of plume concentration on smoke evolution from smoke plumes sampled by the NASA DC-8 during FIREX-AQ. We find that observed organic aerosol and size distribution changes are correlated to plume aerosol mass concentrations. Additionally, coagulation explains the majority of the observed growth.