AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Speciated Characterization of Primary Organic Aerosol Emissions from on Road Gasoline and Diesel Vehicles
DAVID WORTON, Gabriel Isaacman, Drew Gentner, Arthur Chan, Chris Ruehl, Timothy Dallmann, Thomas Kirchstetter, Kevin Wilson, Robert Harley, Allen H. Goldstein, University of California, Berkeley
Abstract Number: 610 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Emissions from on road gasoline and diesel vehicles are major sources of primary organic aerosol (POA) to the atmosphere. Characterizing the chemical composition of this POA source has implications for the rate of secondary organic aerosol (SOA) formation and its resultant composition when these compounds evaporate during atmospheric dilution. Samples of vehicle exhaust particulates were collected in the Caldecott Tunnel (California highway 24) in July 2010 and analyzed by gas chromatography with high resolution time of flight mass spectrometry and vacuum ultraviolet ionization (GC/VUV-HRTOFMS). This “soft” ionization technique allows for improved identification of hydrocarbons because they display a significant parent ion peak facilitating compound classification according to carbon number, degree of saturation and number of rings in their structure. Here, POA was broadly classified into straight and branched alkanes, straight and branched cycloalkanes and aromatics. The composition of POA was dominated by hydrocarbons with between 20 and 30 carbon atoms, consistent with being derived from motor oil with minimal influence from unburnt diesel fuel and no influence from unburnt gasoline. The calibrated sum of all speciated measurements agreed with the total measured organic carbon within analytical uncertainties indicating full mass speciation of POA. These results are important for improving the representation of POA in models and have implications for the formation rate and product composition of SOA produced from the semi-volatile organic vapors because of the different atmospheric oxidation trajectories of the identified functional groups.