Effect of OH radicals, relative humidity, and time on the composition of the products formed in the ozonolysis of α-pinene

The gas-phase ozonolysis of alpha-pinene at ppb levels were studied and the effects of OH radicals formed in the reaction, the relative humidity (RH), and time on the products formed were investigated. Identified products were pinic acid, glyoxal, methyl glyoxal, norpinonic acid and a norpinonic acid isomer, pinonic acid, a C-4 dicarbonyl, a C-5 dicarbonyl, norpinon aldehyde, and pinon aldehyde. The different parameters effect on the formation of these products were evaluated using experimental design and multivariate modeling. Pinonic acid, norpinonic acid and its isomer, were not detected in the absence of OH radicals. The amounts of pinic acid, norpinon aldehyde, and pinon aldehyde all decreased in the absence of OH radicals. Glyoxal and methyl glyoxal were not affected. The formation of pinonic acid decreased when the RH was increased. The formation of pinic acid, glyoxal, methyl glyoxal, and pinon aldehyde increased with increasing RH, while norpinon aldehyde was not affected. The implications of these observations and additional interaction effects are discussed, and a novel route of the formation of pinic acid is presented. (C) 2003 Elsevier Ltd. All rights reserved.