Aerosol and product yields from NO3 radical-initiated oxidation of selected monoterpenes

Atmospheric transformation of monoterpenes gives products that may cause en vironmental consequences. In this work the NO3 radical-initiated oxidation of the monoterpenes alpha-pinene, beta-pinene, Delta(3)-carene, and limonen e has been investigated. All experiments were conducted in EUPHORE, the EUr opean PHOto REactor facility in Valencia, Spain. The aerosol and product yi elds were measured in experiments with a conversion of the terpenes in the interval from 7 to 400 ppb. The lower end of the concentrations used are cl ose to those measured in ambient pine forest air. Products were measured us ing long path in situ FTIR. Aerosol yields were obtained using a DMA-CPC sy stem. The aerosol mass yields measured at low concentrations (10 ppb terpen e reacted) were <1, 10, 15, and 17% for alpha-pinene, beta-pinene, Delta(3) -carene, and limonene, respectively. The total molar alkylnitrate yields we re calculated to he 19, 61, 66, and 48%, and molar carbonyl compound yields were estimated to be 71, 14, 29, and 69% for alpha-pinene, beta-pinene, De lta(3)-carene, and limonene, respectively. The aerosol yields were strongly dependent on the amounts of terpene reacted, whereas the nitrate and carbo nyl yields do not depend on the amount of terpene converted. The principal carbonyl compound from a-pinene oxidation was pinonaldehyde. In the case of limonene, endolim was tentatively identified and appears to be a major pro duct. The reactions with beta-pinene and Delta(3)-carene yielded 1-2% of no pinone and 2-3% caronaldehyde, respectively. The results show that it is no t possible to use generalized descriptions of terpene chemistry, e.g. in ma tematical models.