Air Quality Impacts of Vehicle Emissions on the Urban Environment: Real-World Emission Factors and Capturing the Fleet Signal

Human exposure to vehicle emissions and traffic-related air pollution is a major concern with the increasing population living near major roadways and in urban areas. Although there has been a growing interest in near-road measurements and deployment of near-road monitoring networks, isolating and quantifying vehicle emissions from these measurements have always been a challenge. Emission factors has proven to be a method that is invaluable in targeting vehicle emissions while normalizing for the effects of local dilution and dispersion. Algorithms were developed to automatically capture and calculate emission factors from exhaust plumes from vehicles. The individual plume emission factor method utilized high time resolution measurements and provided insight on inter-fleet emission dynamics and trends, providing mean emission factors for the downtown Toronto on-road fleet, co-emitted pollutants from various emitter groups, relative contributions from heavy emitters, and compared well with real-world emission factors from past studies. Additionally, discrepancies were observed between past laboratory and the measured real-world emission factors, with differences upwards of an order of magnitude for the more dynamic pollutants such as particle number concentration. Temporal variation in emission factors were also observed diurnally, weekday vs. weekend, and seasonally, where influences were found to be from changes in fleet make-up, fuel composition, and ambient conditions. A simplified daily-integrated emission factor method was subsequently applied to nearly two years of continuous measurements made at three near-road sites with varying site and fleet characteristics, as well as different meteorological conditions. Emission factors proved to be a useful metric in normalizing the site differences, and provided insight on inter- and intra- fleet emissions characteristics.Ph.D.2018-07-31 00:00:0