Estimates of heterogeneous formation of secondary organic aerosol during a wood smoke episode in Houston, Texas

U. Nopmongcol, W. Khamwichit, M. P. Fraser, D. T. Allen

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Observational data, collected during a wood smoke episode in Houston, Texas, were used to assess the extent to which acid-catalyzed reactions of carbonyls might contribute to secondary organic aerosol (SOA) formation. The wood smoke episode was chosen for this analysis because of relatively high concentrations of acidic aerosol, coupled with high concentrations of SOA precursors during the episode. Photochemical modeling, coupled with ambient measurements, indicated that acid aerosol-mediated organic aerosol formation reactions, not accounted for in most current photochemical models, may have led to SOA formation of up to a few μg m-3. In photochemical simulations, acid-mediated organic aerosol formation was modeled by calculating the rate of impingement of aldehyde molecules on acidic particles, and then assuming that a fraction of the impingements resulted in reaction. For reaction probabilities on the order of 0.005-0.0005, the model predicted SOA concentrations were consistent with estimates of SOA based on observations. In addition, observed concentrations of particulate phase ammonium during the episode were consistent with high concentrations of the types of organic acids that would be formed through acid-catalyzed reactions of carbonyls. Although there are substantial uncertainties in the estimates of heterogeneous SOA formation, collectively, these data and modeling analyses provide evidence for the importance of acid-catalyzed SOA formation reactions.

Original languageEnglish (US)
Pages (from-to)3057-3070
Number of pages14
JournalAtmospheric Environment
Issue number14
StatePublished - May 2007
Externally publishedYes


  • Acid
  • Biomass combustion
  • Heterogeneous reactions
  • Secondary organic aerosol
  • Sulfate

ASJC Scopus subject areas

  • General Environmental Science
  • Atmospheric Science


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