Aircraft Measurement of Isoprene-derived Organic Aerosol during the Southeast Nexus (SENEX) Campaign Using an Aerosol Mass Spectrometer

Wednesday, 17 December 2014
Lu Xu1, Ann M Middlebrook2, Jin Liao2, Andre Welti3, Hongyu Guo4, Jack J Lin5, Aikaterini Bougiatioti6, Rodney J Weber7, Athanasios Nenes8, John S Holloway9, Jessica Gilman10, Brian M Lerner11, Martin Graus12, Carsten Warneke2, Michael Trainer13, Joost A De Gouw13 and Nga Lee Ng8, (1)Georgia Institute of Technology Main Campus, Atlanta, GA, United States, (2)NOAA Boulder, Boulder, CO, United States, (3)ETH Swiss Federal Institute of Technology Zurich, Zurich, Switzerland, (4)Georgia Institute of Technology Main Campus, Earth and Atmospheric Sciences, Atlanta, GA, United States, (5)Georgia Tech, Atlanta, GA, United States, (6)National Technical University of Athens (NTUA), Marousi Athens, Greece, (7)Georgia Inst Technology, Atlanta, GA, United States, (8)Georgia Institute of Technology, Atlanta, GA, United States, (9)CIRES, Boulder, CO, United States, (10)NOAA ESRL, Boulder, CO, United States, (11)NOAA, Earth System Research La, Boulder, CO, United States, (12)Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (13)NOAA Earth System Research Lab, Boulder, CO, United States
Isoprene is an important precursor for secondary organic aerosol (SOA) formation due to its large global emissions and high reactivity. Recent studies have found that isoprene SOA formation via the uptake of isoprene epoxydiol (IEPOX) under low NOx conditions appears to be largely affected by anthropogenic emissions and are not well understood. Here we investigate the effects of anthropogenic emissions on isoprene SOA formation through airborne measurements above the southeastern US, which is an ideal location for this study since this area is characterized by high emissions of both anthropogenic and isoprene sources. An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed aboard the NOAA WP-3D aircraft during the Southeast Nexus (SENEX) field campaign to characterize the non-refractory chemical composition of submicron aerosol. Positive Matrix Factorization (PMF) analysis was performed on the organic aerosol (OA) mass spectra to identify patterns of organic components and various OA factors were resolved. Low-volatility Oxygenated Organic Aerosol (LV-OOA) constituted a major fraction of OA. Isoprene-derived OA was also identified in certain flights and correlated well with sulfate. This result is consistent with our recent finding from ground-based measurements in Centreville during the Southern Oxidant and Aerosol Study (SOAS) field campaign that isoprene-derived OA is directly modulated by the abundance of sulfate. The vertical distribution of isoprene-derived OA will be discussed along with the timescale of the effect of sulfate on isoprene OA formation.