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Abstract

Five products from beta-caryophyllene oxidation (beta-caryophyllonic acid (I), 3,3-dimethyl-2-(3-oxobutyl) cyclobutanecarboxylic acid (beta CA198) (II), beta-nocaryophyllonic acid (III), beta-caryophyllinic acid (IV), and 2-(2-carboxyethyl)-3,3-dimethylcyclobutanecarboxylic acid (beta CA200) (V)) were synthesized and their structures confirmed by nuclear magnetic resonance spectroscopy. Reaction chamber experiments with P-caryophyllene at two different ozone mixing ratios were performed and the carboxylic acid oxidation products in the particle phase were characterized by APCI-MS and HPLC-ESI-MS. All five synthesized acids were found as beta-caryophyllene oxidation products in the reaction chamber aerosol. The main oxidation products of the reaction chamber experiments were beta-14-hydroxynocaryophyllonic acid, beta-nocaryophyllonic acid (III) and beta CA198 (II). Product yields of the acids were estimated based on the chamber experiments and the application of the atmospheric chemistry box model CAABA/MECCA. Finally, ambient aerosol samples taken during the HUMPPA campaign in Hyytiala, Finland in summer 2010 were analysed for the carboxylic acid beta-caryophyllene oxidation products. All five synthesized compounds were detected and were quantified in the ambient aerosol samples. The major beta-caryophyllene carboxylic acid oxidation products in the ambient air samples were beta-nocaryophyllonic acid (III) and beta CA198 (II) with concentrations in the range of about 0.2-14 ng m(-3) and 0.8-6.8 ng m(-3). The fact that the concentrations of these two acids in ambient aerosol are generally higher than the concentration of beta-caryophyllinic acid (IV) (often used in previous studies as oxidation tracer) with a concentration of about 0.16 ng m(-3) leads to the conclusion that these two acids are better suited as tracer compounds for beta-caryophyllene secondary organic aerosol formation. (C) 2013 Elsevier Ltd. All rights reserved.