UC Irvine

Sesquiterpene (SQT) and montoterpene (MT) emissions from loblolly pine (Pinus taeda L.) were studied by branch enclosure experiments at Duke Forest in Chapel Hill, NC. Four SQT (β-caryophyllene, α-bergamotene, α-humulene, β-farnesene), five MT (α-pinene, β-pinene, β-myrcene, β-phellandrene, limonene), and the oxygenated MT linalool were identified. Emission rates of both compound classes increased exponentially with temperature, albeit SQT temperature coefficients (0.12–0.18K−1) were higher than for MT (0.068–0.15K−1), resulting in an increased contribution of SQT to the overall biogenic volatile organic compound (BVOC) flux during warm temperature conditions. The highly correlated variables of light and temperature conditions preclude a rigorous characterization of their individual roles in driving these emissions. However, the observations indicate that there may be both temperature-only and temperature/light-dependent components contributing to SQT emission variations. When normalized to 30°C using the best-fit temperature algorithm, total SQT basal emission rate was 450ngg−1h−1. The potential contribution of SQT from all pine trees (based on the loblolly pine emission factors) to secondary, biogenic organic aerosol in 12 southeastern US states was estimated to be 7×106kg for the month of September which constitutes an appreciable portion of the overall PM 2.5 emission budget.