Gaseous and Particulate Oxidation Products Analysis of a Mixture of α-pinene + β-pinene/O3/Air in the Absence of Light and α-pinene + β-pinene/NOx/Air in the Presence of Natural Sunlight

Abstract

The gas and particle phase reaction products of a mixture of the atmospherically important terpenes α-pinene and β-pinene with the atmospheric oxidants O3 and OH/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 a mixture of α-pinene and β-pinene in the presence of O3/air, and the daytime oxidation of a mixture of α-pinene + β-pinene with NOx air in the presence of natural sunlight were carried out in the University of North Carolina's large outdoor smog chamber (190 m3) located in Chatham County, North Carolina. Mass balances for gaseous and aerosol reaction products are reported over the course of the reaction. More than twenty-nine products were identified and/or quantified in this study. On average, measured gas and particle phase products accounted for ∼74 to ∼80% of the reacted α-pinen/β-pinene mixture carbon. Measurements show that a number of reaction products were found in both O3 and NOx system [pinonaldehyde, pinic acid, pinonic acid, pinalic-3-acid, 4-hydroxypinalic-3-acid, 4-oxonopinone, 1-hydroxy-nopinone, 3-hydroxy-nopinone, and nopinone]. Pinonic acid, pinic acid, pinalic-3-acid, 4-hydroxypinalic-3-acid, and 10-hydroxypinonic acid were observed in the early stage in the aerosol phase and may play an important role in the early formation of secondary aerosols.