AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Contribution of Tailpipe Emissions of Gas Phase Precursors to Secondary Aerosol Formation
BEHDAD YAZDANI BOROUJENI, Chance Spencer, Don Collins, Texas A&M University
Abstract Number: 290 Working Group: Urban Aerosols
Abstract On-road vehicle emissions are a significant source of ambient air pollution. Laboratory and real-world based emission measurements of heavy duty diesel vehicles (HDDV) show that they are important sources of primary aerosols. However, emitted gaseous species, especially those from light duty gasoline vehicles (LDGV), can undergo photochemical reactions and act as precursors for secondary aerosol formation. Recent studies suggest that the contribution of gasoline vehicles to transportation-related aerosol mass in the atmosphere may dominate over that from diesel vehicles.
This study used near-roadway portable captive aerosol chambers to assess the contribution of gas phase vehicle emissions in formation of secondary aerosol. Two identical cylindrical chambers, each 1 m3 in volume, were used along with integrated scanning mobility particle sizers (SMPS). The cylindrical wall and top portion of each chamber is made of 0.025 mm transparent fluorinated ethylene propylene (FEP) film. The bottom portion of each chamber is a permeable membrane of expanded polytetrafluoroethylene (ePTFE), which allows gases to diffuse into the chamber and react inside it while preventing penetration of particles. The experiments were performed near a major arterial road in College Station, TX. One of the chambers was located upwind and the other downwind of the roadway. In both chambers, monodisperse seed particles were injected and their growth rate evaluated using the SMPS systems. The difference between measured upwind and downwind captive aerosol growth rates is interpreted as the contribution of gaseous vehicle emissions in formation of secondary aerosol mass. Complementary measurements of the primary emissions size distributions were made by sampling ambient air with both SMPS systems. Preliminary results based on 10 days of experiments conducted under varying meteorological conditions will be presented.