Sesquiterpene Emissions and Their Impact on Aerosol Formation in the United States

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This project will establish a database of seasonal sesquiterpene (SQT) emission rates from the dominant natural United States shrubs and trees. Experiments will be conducted at a tree nursery in Boulder, Colorado, supplemented by field trips to other selected sites. Speciated emission rates will be monitored with a field-deployable gas chromatography (GC)/mass spectrometry (MS) instrument, and the use of a proton transfer reaction mass spectrometer (PTRMS) will also be explored. A capillary diffusion system for generation of SQT standards will be used for calibration and characterization of the experimental procedures. In order to reduce uncertainties in SQT emission rates, several approaches will be taken: a high number of replicate measurements will be performed on species of important biomass genera; trees and shrubs from the same species but from different populations will be compared; seasonal changes in emission rates will be investigated with year-round measurements; and parameters that may affect SQT emission rates, such as temperature, light, mechanical stress, drought, pests, and ozone exposure will be examined. Data will be incorporated into the Model of the Emissions of Gases and Aerosol from Nature (MEGAN) for an assessment of SQT emissions on atmospheric concentrations and biogenic aerosol formation. SQT emission rates, and emission algorithms will be made available to the scientific community for use in air quality modeling.Graduate and undergraduate students will participate in the field studies and modeling efforts. The results will be incorporated into lectures and other presentations, and an educational website will present this research for use in classroom teaching. Several local outreach efforts are planned, including a poster presentation, flyers, and a talk at a local forestry council meeting.