AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Chemistry and Partitioning Behavior of Inorganic and Organic Particulate Matter Measured in Real-time from Light-duty Vehicles under Varying Conditions
SONYA COLLIER, Toshihiro Kuwayama, Sara Forestieri, Michael Kleeman, Christopher Cappa, Qi Zhang, University of California, Davis
Abstract Number: 200 Working Group: Combustion
Abstract We investigated the chemistry and partitioning behavior of inorganic and organic particulate species in the exhaust of 11 in-use vehicles, which included 8 gasoline light-emission vehicles with years ranging from 1997 to 2003 and 3 alternative vehicles consisting of an ultra-low emission vehicle, a passenger diesel vehicle, and a gas direct-inject vehicle. In this study, vehicle emissions were sampled into a custom-built secondary dilution system (SDS) while running on a chassis dynamometer under the California Unified Cycle (UC), where emissions were diluted to atmospherically relevant concentrations (5-30 micro-grams per meter cubed) under varying relative humidity. Here we present the results for the non-refractory submicron particles sampled by an Aerodyne High Resolution Time-of-Flight Mass Spectrometer (HR-ToF-MS) at high time-resolution (0.1 Hz). High relative humidity (>70%) tests resulted in high yields of ammonium sulfate during certain portions of the UC. The chemically resolved size-distribution derived from the HR-ToF-MS indicates that the ammonium sulfate particles were externally mixed with the organics, suggesting rapid particle growth in the SDS. One case-study shows that a high burst of ammonium sulfate particles affected the partitioning behavior of the organic species to the particle phase. Data from complimentary, collocated instruments are consistent with the results obtained by the HR-ToF-MS. The results of this study offer the vehicle emissions community a closer look at the chemistry of PM from gasoline LDV and how it is affected by the conditions it is emitted into. These results may have large impacts on future vehicle emission control standards and source apportionment modeling.