Abstract
Abstract. The secondary organic aerosol (SOA) yield of β-caryophyllene photooxidation is enhanced by aerosol acidity. In the present study, the influence of aerosol acidity on the chemical composition of β-caryophyllene SOA is investigated using ultra performance liquid chromatography/electrospray ionization-time-of-flight mass spectrometry (UPLC/ESI-TOFMS). A number of first-, second- and higher-generation gas-phase products having carbonyl and carboxylic acid functional groups are detected in the particle phase. Particle-phase reaction products formed via hydration and organosulfate formation processes are also detected. Increased acidity leads to different effects on the abundance of individual products; significantly, abundances of organosulfates are correlated with aerosol acidity. To our knowledge, this is the first detection of organosulfates and nitrated organosulfates derived from a sesquiterpene. The increase of certain particle-phase reaction products with increased acidity provides chemical evidence to support the acid-enhanced SOA yields. Based on the agreement between the chromatographic retention times and accurate mass measurements of chamber and field samples, three β-caryophyllene products (i.e., β-nocaryophyllon aldehyde, β-hydroxynocaryophyllon aldehyde, and β-dihydroxynocaryophyllon aldehyde) are suggested as chemical tracers for β-caryophyllene SOA. These compounds are detected in both day and night ambient samples collected in downtown Atlanta, GA and rural Yorkville, GA during the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS).
Highlights
Secondary organic aerosol (SOA) formation from the oxidation of biogenic precursors, such as isoprene (C5H8), monoterpenes (C10H16), sesquiterpenes (C15H24), and oxygenated terpenes, contributes significantly to atmospheric aerosol mass (Hallquist et al, 2009 and references therein). β-caryophyllene (C15H24) is one of the most reactive sesquiterpenes, with two double bonds, and has high reactivity towards ozone (O3), Published by Copernicus Publications on behalf of the European Geosciences Union.M
A range of aerosol yields has been reported (O3: 5– 46%; OH: 17–68%), depending on aerosol organic mass and experimental conditions
Nguyen et al (2009) predicted that the rate coefficient for O3 attack on the exocyclic double bond is less than 5% of that for O3 attack on the endocyclic double bond
Summary
Secondary organic aerosol (SOA) formation from the oxidation of biogenic precursors, such as isoprene (C5H8), monoterpenes (C10H16), sesquiterpenes (C15H24), and oxygenated terpenes, contributes significantly to atmospheric aerosol mass (Hallquist et al, 2009 and references therein). β-caryophyllene (C15H24) is one of the most reactive sesquiterpenes, with two double bonds (one endocyclic and one exocyclic), and has high reactivity towards ozone (O3), Published by Copernicus Publications on behalf of the European Geosciences Union. The influence of aerosol acidity on the chemical composition of βcaryophyllene SOA from β-caryophyllene photooxidation is investigated using ultra performance liquid chromatography/electrospray ionization-time-of-flight mass spectrometry (UPLC/ESI-TOFMS). 9.97 14.7 21.3 34.0 segregated PM2.5 (particulate matter with an aerodynamic diameter
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