AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Hourly Measurement of the Concentration and Gas-Particle Partitioning of Oxygenated Organic Tracers in Ambient Aerosol: First Results from Berkeley, CA and Rural Alabama
GABRIEL ISAACMAN, Nathan Kreisberg, Lindsay Yee, Arthur Chan, David Worton, Susanne Hering, Allen H. Goldstein, University of California, Berkeley
Abstract Number: 358 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Hourly and bi-hourly time-resolved measurements of organic tracer compounds in ambient aerosols have been successfully used to elucidate sources and formation pathways of atmospheric particulate matter. Here we extend the Semi-Volatile Thermal desorption Aerosol Gas chromatograph (SVTAG), a custom in-situ instrument that collects, desorbs, and analyzes ambient aerosol and semi-volatile compounds with hourly time resolution, to include on-line derivatization and a second, parallel collection cell that provides simultaneous collection of both particle-phase and particle-plus-gas-phase organic compounds. By introducing a silylating agent upon desorption, SVTAG can measure highly oxygenated compounds that are not easily detected using traditional gas chromatography including most previously reported oxygenated tracers for biogenic and anthropogenic secondary organic aerosol. The use of a pair of matched collection cells with parallel sampling and serial analysis provides direct gas-particle partitioning information. One cell collects total organic fraction of compounds with a volatility lower than that of approximately a C$_(13) hydrocarbon, while the other cell samples through an activated carbon denuder to remove the gas-phase. Taken together these measurements provide a direct measurement of gas-particle partitioning to yield a direct check on classical absorption based partitioning theory while providing insights into important aerosol formation chemistry, such as oligomerization and salt formation. We present here the capabilities of the dual cell SVTAG with derivatization, including tests on ambient Berkeley air and the first results from the Southern Oxidant and Aerosol Study (SOAS). Correlations between oxygenated biogenic and anthropogenic tracers are explored. Tracers that have typically been available only from offline chemical analyses of filters with lower time-resolution (several hours to several days) are accessed using this instrument and presented here, including several tracers for isoprene oxidation under varying chemical regimes, i.e. 2-methyltetrols under low-NO$_x conditions, and 2-methyl glyceric acid under high-NO$_x conditions. The diurnal variation of tracers such as these elucidates the influence of anthropogenic emissions on biogenic aerosol formation.