Preprints
https://doi.org/10.5194/acp-2021-247
https://doi.org/10.5194/acp-2021-247

  30 Mar 2021

30 Mar 2021

Review status: this preprint is currently under review for the journal ACP.

Diel Cycle Impacts on the Chemical and Light Absorption Properties of Organic Carbon Aerosol from Wildfires in the Western United States

Benjamin Sumlin1, Edward Fortner2, Andrew Lambe2, Nishit Shetty1, Conner Daube2, Pai Liu1, Francesca Majluf2, Scott Herndon2, and Rajan K. Chakrabarty1 Benjamin Sumlin et al.
  • 1Center for Aerosol Science and Engineering, Department of Energy, Environmental, and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri
  • 2Aerodyne Research, Inc., Billerica, Massachusetts

Abstract. Organic aerosol (OA) emissions from biomass burning have been the subject of intense research in recent years, involving a combination of field campaigns and laboratory studies. These efforts have aimed at improving our limited understanding of the diverse processes and pathways involved in the atmospheric processing and evolution of OA properties, culminating in their accurate parameterizations in climate and chemical transport models. To bring closure between laboratory and field studies, wildfire plumes in the western United States were sampled and characterized for their chemical and optical properties during the ground-based segment of the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) field campaign. Using a custom-developed multiwavelength integrated photoacoustic-nephelometer (MIPN) spectrometer in conjunction with a suite of instruments, including an oxidation flow reactor equipped to generate hydroxyl (OH∙) or nitrate (NO3∙) radicals to mimic daytime or nighttime oxidative aging processes, we investigated the effects of multiple equivalent days or nights of OH∙/NO3∙ exposure on the chemical composition and mass absorption cross-sections (MAC(λ)) at 488 and 561 nm of OA emitted from wildfires in Arizona and Oregon. We found that OH∙ exposure reduced the wavelength-dependent MAC(λ) by a factor of 0.72 ± 0.08, consistent with previous laboratory studies. On the other hand, NO3∙ exposure increased it by a factor of up to 1.69 ± 0.38. The MAC enhancement following NO3∙ exposure was correlated with an enhancement in CHO1N and CHOgt1N ion families measured with an aerosol mass spectrometer.

Benjamin Sumlin et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of Sumlin et al ACPD', Anonymous Referee #1, 27 Apr 2021
  • RC2: 'Comment on acp-2021-247', Anonymous Referee #2, 29 Apr 2021

Benjamin Sumlin et al.

Benjamin Sumlin et al.

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Short summary
We present a comparison of the changes to light absorption behavior and chemical composition of wildfire smoke particles from day- and night-time oxidation processes, and discuss the results within the context of previous laboratory findings.
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