Abstract
Abstract. Pinonaldehyde oxidation by OH radicals under low-NOx conditions produces significant secondary organic aerosol (SOA) mass yields. Under concurrent UV illumination, mass yields are lower than high-NOx yields published earlier by our group. However, when OH radicals are produced via dark ozonolysis the SOA mass yields are comparable at high and low NOx. Because pinonaldehyde is a major first-generation gas-phase product of α-pinene oxidation by either ozone or OH radicals, its potential to form SOA serves as a molecular counterpoint to bulk SOA aging experiments involving SOA formed from α-pinene. Both the general tendency for aging reactions to produce more SOA and the sensitivity of the low-NOx products to UV photolysis observed in the bulk clearly occur for this single species as well. Photochemical oxidation of pinonaldehye and analogous first-generation terpene oxidation products are potentially a significant source of additional SOA in biogenically influenced air masses.
Highlights
Introduction the highest yield yet mosEtvaolratthileSpryodsutcetsmof α-pinene oxidation by ozone and OH radicals, with molar yields ranging from 20–25 % (HatakeyamaSect iael.,n1c9e89s, 1991)
In the Supplement, Fig. E, we show a sample experiment where different n-aldehyde vapors were injected to the smog chamber and their concentrations remained stable for roughly 1 hour to within the precision of the PTRMS signal; we did not observe dramatic losses for these aldehydes, though very rapid equilibration with the chamber walls cannot be ruled out
We see no evidence for significant vapor wall losses, especially considering that the conclusions of this work derive from relative Secondary organic aerosol (SOA) mass yields under different conditions
Summary
VaolratthileSpryodsutcetsmof α-pinene oxidation by ozone and OH radicals, with molar yields ranging from 20–25 % (HatakeyamaSect iael.,n1c9e89s, 1991). Secondary organic aerosol (SOA) constitutes a significant portion of particulate matter mass (PM2.5) (Kanakidou et al, 2005; Hallquist et al, 2009) and is a very dynamic part of the atmospheric aerosol system. SimOilacr estarunctuSrecs iceanncbeefound in other products of oxidation from different monoterpenes, such as caronaldehyde and limononaldehyde, among others (Larsen et al, 2001; Lee et al, 2006; Hakola et al, 1994). Pinonaldehyde can give us an understanding of SOA formation potential from other similar first-generation products of biogenic nature; ,SthoelriedarEe alimrtihted data on the erations of oxidation in the atmosphere.
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