Isoprene, Monoterpene, and Sesquiterpene Oxidation Products in the High Arctic Aerosols during Late Winter to Early Summer
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Oxidation products of biogenic volatile organic compounds (BVOCs) (isoprene, monoterpenes, and sesquiterpene) were investigated in the Canadian High Arctic aerosols using gas chromatography-mass spectrometry. Twelve specific secondary organic aerosol (SOA) tracers and two hydroxyacids (glycolic and salicylic acids) were determined. The total concentrations of alpha-/beta-pinene oxidation products (e.g., pinic and 3-hydroxyglutaric acids, 138-5303 pg m(-3), average 1646 pg m(-3)) were much higher than those of isoprene oxidation products (e.g., 2-methyltetrols and 2-methylglyceric acid, 80-567 pg m(-3), 300 pg m(-3)) and sesquiterpene (beta-caryophyllene) oxidation product (beta-caryophyllinic acid, 9-372 pg m(-3), 120 pg m(-3)). Although the mean contribution of isoprene oxidation products to organic carbon (OC) is very low (0.059%) compared to monoterpene oxidation products (0.29%), they increase significantly up to 0.20% in early summer when photochemical activity and atmospheric transport from North America are enhanced. Temporal variations of SOA tracers of monoterpenes and beta-caryophyllene are characterized by a winter/spring maximum and a summer minimum, being similar to those of OC and EC. In contrast, the isoprene oxidation tracers such as 2-methyltetrols showed a peak in early summer. By using a tracer-based method, we found that monoterpenes and beta-caryophyllene are the major contributors to secondary OC from dark winter to late May. However in early June, isoprene was found to be the largest contributor among the three precursors. This study demonstrates that photochemical oxidation of BVOCs also contributes to the formation of OC and WSOC in the Arctic atmosphere during late winter to early summer.
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