Anantha Valsalan, Greg Evans, Cheol-Heon Jeong Southern Ontario Centre For Atmospheric Aerosol Research, University Of Toronto

Fine particulate matter (PM2.5) 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.1The WHO claims safe PM2.5

levels to be below a daily average of 25 µg/m3.2

Figure 1: Diesel and gasoline vehicles are known sources of PM2.5

• To quantify the contribution of vehicles to the PM2.5 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 PM2.5 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 PM2.5 emissions for the 6 month period.

Figure 3: A comparison between total road level and rooftop level PM2.5 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 PM2.5. 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

Co

nce

ntr

atio

n (µ

g/m

3)

Hour of Day

Diurnal Trend Of Weekend and Weekday Emissions Of Vehicular Fine Particulate Matter

Weekdays

Weekends

Figure 5: The PM2.5 contribution from vehicles varies seasonally. It can be seen that summer contributions are lower than winter and spring.

11% (0.85 µg/cm3)

11% (0.72 µg/cm3)

7.6% (0.76 µg/cm3)

0

2

4

6

8

10

12

14

winter spring summer

% C

on

trib

uti

on

Fro

m

Ve

hic

les

Bar Chart Showing Variation In Seasonal Contribution Of PM2.5 From Vehicles

• Vehicles contribute approximately 10% of the total PM2.5 emissions on College Street.

• PM2.5 from vehicles is highest in the winter with little significant difference between spring and summer

• Measures taken to reduce emissions from cars are working

• PM2.5 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.

1National 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

2World 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

Co

nce

ntr

atio

n (µ

g/c

m3)

Time

Graph Showing Variation of Rooftop And Road Level PM2.5 On A Time Scale

Road Level PM2.5

Roof Level PM2.5

• Vehicles contribute approximately 10% of the total PM2.5 emissions on College Street.

• PM2.5 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 PM2.5 levels in the atmosphere.