Anantha Valsalan, Greg Evans, Cheol-Heon Jeong Southern Ontario Centre For Atmospheric Aerosol Research, University Of Toronto Fine particulate matter (PM 2.5 ) refers to small particles of solids or liquids suspended in the air which have a diameter < 2.5 μm. PM2.5 is responsible for many harmful health effects such as asthma and cardiopulmonary disease. 1 The WHO claims safe PM 2.5 levels to be below a daily average of 25 μg/m 3 . 2 Figure 1: Diesel and gasoline vehicles are known sources of PM 2.5 • To quantify the contribution of vehicles to the PM 2.5 concentration on College Street • To identify diurnal and seasonal trends in the vehicular PM2.5 on College Street • Two OPS were used for sampling: one at rooftop elevation ( ~ 30 m), one at road level from January to June 2013 • Rooftop OPS sampled for ‘Background’ concentration while the road level OPS sampled ‘Vehicular + Background’ concentration. (Both OPS were corrected with each other) • Difference between ground and rooftop concentrations gives vehicular PM 2.5 only Figure 4: The variation in diurnal trend of emissions due to vehicles on weekends and weekdays. The average daily concentration from vehicles on weekdays is 0.81 μg/m3 and on weekends it is 0.73 μg/m3. Combined, this is ~ 10% of total PM 2.5 emissions for the 6 month period. Figure 3: A comparison between total road level and rooftop level PM 2.5 concentrations. It can be seen that road level concentrations are consistently higher than roof level – this consistent difference is assumed to be the vehicular contribution to PM 2.5 . The large spikes at road level are due to high-emitting vehicles. 0.5 0.6 0.7 0.8 0.9 1 1.1 0 1 2 3 4 5 6 7 8 9 1011121314151617181920212223 Concentration (μg/m 3 ) Hour of Day Diurnal Trend Of Weekend and Weekday Emissions Of Vehicular Fine Particulate Matter Weekdays Weekends Figure 5: The PM 2.5 contribution from vehicles varies seasonally. It can be seen that summer contributions are lower than winter and spring. 11% (0.85 μg/cm 3 ) 11% (0.72 μg/cm 3 ) 7.6% (0.76 μg/cm 3 ) 0 2 4 6 8 10 12 14 winter spring summer % Contribution From Vehicles Bar Chart Showing Variation In Seasonal Contribution Of PM 2.5 From Vehicles • Vehicles contribute approximately 10% of the total PM 2.5 emissions on College Street. • PM 2.5 from vehicles is highest in the winter with little significant difference between spring and summer • Measures taken to reduce emissions from cars are working • PM 2.5 concentration due to vehicles is well within the levels considered safe by the WHO • Funding was generously provided by the Centre For Global Change Science • Technical guidance and data provided by Cheol-Heon Jeong and many other members of SOCAAR. 1 National PEP Weighing Laboratory US-EPA, Region 4, “PM2.5 Objectives and History” [Online] Accessed August 19 2013. Available: http://www.epa.gov/region4/sesd/pm25/p2.html#2 2 World Health Organization (2006), “WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxide” [Online] Accessed August 19 2013. Available: http://whqlibdoc.who.int/hq/2006/WHO_SDE_PHE_OEH_06.02_eng.pdf Figure 2: Optical Particle Sizer (OPS, TSI Inc.) used to obtain particle concentrations at 1 minute time resolution 0 5 10 15 20 25 30 Concentration (μg/cm 3 ) Time Graph Showing Variation of Rooftop And Road Level PM 2.5 On A Time Scale Road Level PM2.5 Roof Level PM2.5 • Vehicles contribute approximately 10% of the total PM 2.5 emissions on College Street. • PM 2.5 from vehicles is significantly lower in the summer than in winter and spring • Measures taken to reduce emissions from cars are working • Vehicles are not a significant contributor to the PM 2.5 levels in the atmosphere.