Atmospheric Chemistry and Physics (Mar 2018)

Multi-generation chemical aging of <i>α</i>-pinene ozonolysis products by reactions with OH

  • N. Wang,
  • E. Kostenidou,
  • E. Kostenidou,
  • N. M. Donahue,
  • S. N. Pandis,
  • S. N. Pandis,
  • S. N. Pandis

DOI
https://doi.org/10.5194/acp-18-3589-2018
Journal volume & issue
Vol. 18
pp. 3589 – 3601

Abstract

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Secondary organic aerosol (SOA) formation from volatile organic compounds (VOCs) in the atmosphere can be thought of as a succession of oxidation steps. The production of later-generation SOA via continued oxidation of the first-generation products is defined as chemical aging. This study investigates aging in the α-pinene ozonolysis system with hydroxyl radicals (OH) through smog chamber experiments. The first-generation α-pinene ozonolysis products were allowed to react further with OH formed via HONO photolysis. After an equivalent of 2–4 days of typical atmospheric oxidation conditions, homogeneous OH oxidation of the α-pinene ozonolysis products resulted in a 20–40 % net increase in the SOA for the experimental conditions used in this work. A more oxygenated product distribution was observed after aging based on the increase in aerosol atomic oxygen-to-carbon ratio (O : C) by up to 0.04. Experiments performed at intermediate relative humidity (RH) of 50 % showed no significant difference in additional SOA formation during aging compared to those performed at a low RH of less than 20 %.