AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Seasonal and Temporal Variation in Real-world Vehicle Emission Factors in Toronto, Canada
JON M WANG, Naomi Zimmerman, Cheol-Heon Jeong, Robert Healy, Nathan Hilker, Greg J. Evans, SOCAAR, University of Toronto
Abstract Number: 479 Working Group: Urban Aerosols
Abstract Measurements were made at a near-road field sampling site located 15 m from a major roadway in downtown Toronto, Canada. Five seasonal measurement campaigns were made each lasting approximately four weeks; November 7 – December 7, 2013 (fall); February 14 – March 25, 2014 (winter); April 20 – May 27, 2014 (spring); July 22 – September 8, 2014 (summer); January 12 – February 6 (winter). These campaigns spanned a broad range of meteorological conditions with ambient temperature and relative humidity ranging from -18 to +31 °C and 20% to 94%, respectively. A suite of high time resolution instrumentation was utilized including a Fast Mobility Particle Sizer for particle number (PN) concentration and size distribution, a photoacoustic soot spectrometer for particle scattering and absorption, and a proton transfer reaction time-of-flight mass spectrometer for VOCs. Other pollutant measurements included black carbon (BC), CO, and NOx.
This study utilized an individual plume approach to estimate emission factors (EFs) from vehicles, which at higher time resolution were used to interpret diurnal, weekday vs. weekend, and seasonal trends. Results show diurnal variation in emission factors dependent on fleet composition and traffic density. Early morning NOx, PN, and BC mean EFs are nearly two times higher than EFs in the late evening. For PN EFs, a daytime noon increase is observed with mean EFs almost four times higher than at night, which has been linked more with effects of ambient conditions on vehicle exhaust post-tailpipe. Seasonal variation in emission factors was observed for several pollutants including PN, methanol, and toluene, but not for BC EFs. Results highlight the importance of including different EFs with higher resolution models that represent vehicle emissions.