Preprints
https://doi.org/10.5194/acp-2020-501
https://doi.org/10.5194/acp-2020-501

  21 Jul 2020

21 Jul 2020

Review status: this preprint was under review for the journal ACP. A revision for further review has not been submitted.

Fine particle pH and sensitivity to NH3 and HNO3 over summertime South Korea during KORUS-AQ

Ifayoyinsola Ibikunle1, Andreas Beyersdorf2, Pedro Campuzano-Jost3,4, Chelsea Corr2,a, John D. Crounse5, Jack Dibb6, Glenn Diskin7, Greg Huey8, Jose-Luis Jimenez3,4, Michelle J. Kim5, Benjamin A. Nault3,4, Eric Scheuer6, Alex Teng5, Paul O. Wennberg5, Bruce Anderson2, James Crawford2, Rodney Weber8, and Athanasios Nenes8,9,10 Ifayoyinsola Ibikunle et al.
  • 1School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
  • 2NASA Langley Research Center, Hampton, VA 23681, USA
  • 3Department of Chemistry, University of Colorado, Boulder, CO 80309, USA
  • 4Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA
  • 5California Institute of Technology, Pasadena, CA 91125
  • 6Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA
  • 7NASA Ames Research Center, Moffett Field, CA 94035, USA
  • 8School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
  • 9School of Architecture, Civil & Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland
  • 10Center for the Study of Air Quality and Climate Change, Institute for Chemical Engineering Sciences, Foundation for Research and Technology Hellas, Patras, GR-26504, Greece
  • acurrently at: Colorado State University

Abstract. Using a new approach that constrains thermodynamic modeling of aerosol composition with measured gas-to-particle partitioning of inorganic nitrate, we estimate the acidity levels for aerosol sampled in the South Korean planetary boundary layer during the NASA/NIER KORUS-AQ field campaign. The pH (mean ± 1σ = 2.43 ± 0.68) and aerosol liquid water content determined were then used to determine the chemical regime of the inorganic fraction of particulate matter (PM) sensitivity to ammonia and nitrate availability. We found that the aerosol formation is always sensitive to HNO3 levels, especially in highly polluted regions, while it is only exclusively sensitive to NH3 in some rural/remote regions. Nitrate levels are further promoted because dry deposition velocity is low and allows its accumulation in the boundary layer. Because of this, HNO3 reductions achieved by NOx controls prove to be the most effective approach for all conditions examined, and that NH3 emissions can only partially affect PM reduction for the specific season and region. Despite the benefits of controlling PM formation to reduce ammonium-nitrate aerosol and PM mass, changes in the acidity domain can significantly affect other processes and sources of aerosol toxicity (such as e.g., solubilization of Fe, Cu and other metals) as well as the deposition patterns of these trace species and reactive nitrate.

Ifayoyinsola Ibikunle et al.

 
Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Ifayoyinsola Ibikunle et al.

Ifayoyinsola Ibikunle et al.

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Short summary
Analysis of observations over South Korea during the NASA/NIER KORUS-AQ field campaign show that aerosol is fairly acidic (mean pH 2.43 ± 0.68). Aerosol formation is always sensitive to HNO3 levels, especially in highly polluted regions, while it is only exclusively sensitive to NH3 in some rural/remote regions. Nitrate levels accumulate because dry deposition velocity is low. HNO3 reductions achieved by NOx controls can be the most effective PM reduction strategy for all conditions observed.
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