Mass Balance of Gaseous and Particulate Products from β-Pinene/O3/Air in the Absence of Light and β-Pinene/NOx/Air in the Presence of Natural Sunlight

Abstract

The gas and particle phase products from the reaction of β-pinene with the atmospheric oxidants O3 and OH radicals in the presence of NOx were investigated using both gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC) for identification and quantification of reaction products. The nighttime oxidation of β-pinene in the presence of O3/air and the daytime oxidation of β-pinene in the presence of NOx/air and natural sunlight were carried out in the University of North Carolina large outdoor smog chamber (190 m3) located in Chatham County, North Carolina. A Scanning Mobility Particle Sizer system (3936, TSI) and a Condensation Particle Counter (3025A, TSI) were used to study the secondary organic aerosol (SOA) formation, and a filter pack/denuder sampling system was used for simultaneously collecting gas and particle phase products for analysis. A gas chromatograph coupled to a mass spectrometer (GC-EIMS or GC-CIMS) was used for the identification and quantification of gas and aerosol products. A HPLC method was used for the measurement of small carbonyl compounds (aldehydes and ketones) as their 2,4-dinitrophenylhydrazones (DNPH) derivatives. Mass balances for gaseous and aerosol reaction products were reported over the course of the reaction. More than sixteen products were identified and/or quantified in this study. On average, measured gas and particle phase products accounted for ∼57 to ∼71% of the reacted β-pinene carbon. Measurements showed that a number of reaction products were found in both O3 and NOx systems (pinic acid, pinalic-3-acid, 4-hydroxypinalic-3-acid, 4-oxonopinone, 1-hydroxynopinone, 3-hydroxynopinone, and nopinone). Pinic acid, pinalic-3-acid, and 4-hydroxypinalic-3-acid were observed in the early stage in the aerosol phase and may play an important role in the early formation of secondary aerosols. Detailed reaction schemes are presented to account for most of the observed reaction products.