Measurement and Modelling of Motor Vehicle Related Air Toxics
Along Urban Streets
Health Canada
Toxic Substances Research Initiative
Project #55, Final Report
May 2001
(Revised November 2002)
Principal Investigator
Deniz Karman
Department of Civil and Environmental Engineering
Carleton University
Collaborating Partner
Lisa Graham
Emissions Research and Measurement Division
Environment Canada
EXECUTIVE SUMMARY
This is the revised final report for Project # 55 of the Toxic Substances Research
Initiative (TSRI) of Health Canada. The project is a collaborative effort between Carleton
University and Environment Canada’s Emissions Research and Measurement Division
(ERMD). The original final report was submitted in May 2001. The revised version has
been prepared in response to comments received from the TSRI secretariat in March
2002.
The objectives of the project, in summary, are:
i)
ii)
iii)
iv)
To establish a database of motor vehicle related toxic substance
concentrations and PM2.5 mass concentrations at nose-level along a busy
downtown street by measurements in the two extremes of weather
(Summer and Winter) in a typical Canadian city.
To compare and correlate the short term (2 hour periods of peak traffic
volume) concentrations of toxic substances and fine particulate matter
measured at nose-level with the regional air quality monitoring data of
longer duration (24 hours) measured at other urban sites.
To compare and correlate the short-term concentrations of toxic
substances measured at nose-level with the in-vehicle concentrations on
typical commuting trips.
To determine the contribution of motor vehicle traffic to the measured
toxic substance concentrations and fine particulate matter by comparisons
with motor vehicle emission data.
An ambient sampling program was carried out on Slater Street in Ottawa, and in vehicles
on long commuting trips, using equipment designed and built ERMD. Carleton
University graduate students and research assistants were employed in sampling and data
processing while most of the sample analyses were carried out at ERMD's laboratories.
Two periods of fieldwork were completed: 17 January – 25 February 2000, and, 17 July –
11 August 2000. Volatile organic compound (VOC), semi-volatile organic compound
(SVOC), carbonyl compound, and particulate matter (PM2.5) samples were collected.
A source emission study was also undertaken at ERMD laboratories using two transit
buses and two light duty vehicles to characterize emissions from these vehicles under
simulated driving conditions.
The main findings for the gas-phase measurements among the micro-environments
studied, can be summarized as:
-
The temporal variation from day to day of pollutant concentrations observed in
micro-environments is much higher than the spatial variation observed among
diverse micro-environments such as the roadside on a busy downtown street, the
rooftop on a parking structure, the inside of a commuter car, and the inside of a
Measurement and Modelling of Motor Vehicle Related Air Toxics 2
-
-
-
transit bus. The in-vehicle concentrations are generally the highest among these
micro-environments
Despite the large temporal variations, the median values of 24 hr average
concentrations recorded at the National Air Pollution Surveillance (NAPS)
ambient monitoring station on Slater street at a height of 4 m are in general
agreement with the median values of 2 hour average concentrations recorded at
nose-level along the same street.
There are noticeable differences between 2-hour average concentrations recorded
at nose level and 24-hour average concentrations recorded at a height of 10 m, on
the roof of an adjacent parking structure. Nearly all of the difference is due to the
sample averaging time since the comparison of 24 hr average concentrations at
these two locations shows reasonably close agreement.
The in-vehicle concentrations observed during this study in Ottawa are of the
same magnitude as those reported by studies in other cities but in the lower half of
the range of values reported.
PM2.5 measurements were attempted only at the roadside station with the cyclone-filter
combination used in this study. Therefore, particulate phase measurements do not offer
the same opportunity for comparison as the gas-phase measurements. However, the
chemical speciation data for particulate matter can be used in comparisons with NAPS
stations with PM2.5 sampling capability. The speciation is also being used in source
apportionment studies for fine particulate matter in urban air.
The database of 2-hour VOC and PM2.5 concentrations in microenvironments is an
important asset to complement the database from ambient monitoring stations that
generally comprise daily concentrations for the same compounds. While ambient
monitoring data capture the long term trends and provide a basis for quantifying human
exposure, the short-term, microenvironment data collected during this study can give an
indication of the range of exposure values and hence the uncertainties associated with
health risk assessment. The database generated during this study, as well as comparable
data from a similar study at this location in 1994 are being made available electronically
through a web site: http://www.carleton.ca/~dkarman/OMDB.
The measured concentrations of hydrocarbons on Slater Street in 2000 (in the range ~70200 micrograms per cubic meter) are explained dominantly by light duty gasoline vehicle
exhaust in the cold start and hot start modes of operation. These source contributions are
determined by using locally measured light duty gasoline vehicle exhaust profiles.
Locally derived evaporative emission profiles and the extension of ambient data to
heavier hydrocarbons may enable finer resolution between exhaust vs. evaporative
emissions for gasoline vehicles, and gasoline vs. diesel exhaust emissions.
Measurement and Modelling of Motor Vehicle Related Air Toxics 3
CONTENTS
1. INTRODUCTION, 5
2. METHODOLOGY, 6
3. SUMMARY OF FINDINGS, 7
3.1 Gas phase samples at the roadside and in-vehicle microenvironments, 7
3.2 Particulate matter samples at the roadside microenvironment, 18
3.3 Vehicle Emissions sampling, 24
3.4 Chemical Mass Balance Receptor Modelling, 28
4. DISSEMINATION OF RESULTS, 36
OMDB, The Ottawa Microenvironment Database
5. REFERENCES, 37
FIGURES
1. Distribution of gas phase concentrations at the roadside, winter, 8
2. Distribution of gas phase concentrations at the roadside, summer, 9
3. Comparison of 24 hour and 2 hour VOC concentrations, 10
4. Distribution of summer VOC concentrations in 1994 and 2000, 11
5. Comparison of 1994 and 2000 summer VOC median concentrations, 12
6. Comparison of 24 hr roadside and rooftop VOC concentrations, 13
7. Comparison of 2 hr roadside and 24 hr rooftop VOC concentrations, 15
8. Distribution of gas phase concentrations in commuter vehicles, winter, 16
9. Distribution of gas phase concentrations in commuter vehicles, summer, 17
10. Comparison of benzene concentrations with other studies, 21
11. Distribution of PM2.5 concentrations, winter and summer, 22
12. Comparison of PM measurements from 1994 and 2000, 23
13. Elemental and organic carbon in PM2.5 samples, 23
14. Metals in PM2.5 samples, 24
15. Mass emission rates of C2-C26 compounds from buses, 26
16. Normalized C2-C12 emission profiles of light duty vehicles, 28
17. Source contribution estimates during sampling sessions, 32
18. Uncertainties in source contribution estimates, 35
19. Goodness of fit for individual compounds, 35
TABLES
1. Comparison of select compounds in different micro-environments, 19
2. In-vehicle concentrations of select compounds from other studies, 20
3. Mass emission rates of selected compounds from buses, 27
4. Source HC profiles used in CMB modelling, 30
5. Summary output from CMB8 Modelling, 31
Measurement and Modelling of Motor Vehicle Related Air Toxics 4
1. INTRODUCTION
An accurate assessment of the effects of motor vehicle related toxic emissions on urban
populations is a relatively complex task, involving the quantitative characterization of the
traffic, the emissions from that traffic, the exposure of individuals, and the health risks
associated with that exposure. Toxic compound concentrations can show high variability
over time and location, particularly in specific microenvironments such as sidewalks
along busy streets, within vehicles, parking garages, near major point sources etc. The
different health effects of various emissions is particularly important in view of the tradeoffs that may be involved among different types of emissions associated with alternative
or reformulated fuels or transportation technologies. For particulate matter, respirable
particles (those less than 2.5 m diameter), and the changes in chemical composition of
the different size ranges are becoming the focus rather than the mass concentration of
particles.
The Emissions Research and Measurement Division (ERMD) of Environment Canada
and the Department of Civil and Environmental Engineering at Carleton University have
collaborated in field studies aimed at detailed characterization and quantification of
motor vehicle related air pollutants in urban micro-environments, starting with a study
partially funded by Health Canada in 1994. The present study, carried out in the winter
and summer of 2000 complemented and expanded the 1994 study, and was funded by the
Toxic Substances Research Initiative (TSRI) as Project #55.
The objectives of these studies are:
i) To establish a database of motor vehicle related toxic substance concentrations and
PM2.5 mass concentrations at nose-level along a busy downtown street by
measurements in the two extremes of weather (summer and winter) in a typical
Canadian city. Such a database will be an important element for analyzing the
total exposure of urban populations to toxic substances and fine particulate matter.
ii) To compare and correlate the short term (2 hour periods of peak traffic volume)
concentrations of toxic substances and fine particulate matter measured at noselevel with the regional air quality monitoring data of longer duration (24 hours)
measured at other urban sites. Direct comparisons of nose-level concentrations
with data available from the National Air Pollution Surveillance (NAPS) network
will enhance the utility of NAPS data for exposure analysis.
iii) To compare and correlate the short-term concentrations of toxic substances measured
at nose-level with the in-vehicle concentrations on typical commuting trips. Such
measurements and comparisons will provide useful data for estimating the
components of total exposure for individuals who commute to the downtown area
for work-related trips.
iv) To determine the contribution of motor vehicle traffic to the measured toxic substance
concentrations and fine particulate matter by comparisons with motor vehicle
emission data. Motor vehicle emission regulations have accomplished very
significant reductions in CO, NOx, and HC emissions but the effect of these
reductions on the individual species of interest from a human health perspective is
Measurement and Modelling of Motor Vehicle Related Air Toxics 5
relatively complex. Source apportionment for the substances of most interest
would enable the assessment of effectiveness for emission control measures.
Ottawa is an appropriate choice of location for the measurement of motor vehicle related
toxic and reactive compounds, as it has virtually no heavy industry that could be
contributing to the ambient loadings. The extremes of Canadian climate also provide
some special challenges in the assessment of traffic related emission impacts under
different conditions.
2. METHODOLOGY
An ambient sampling program was carried out on Slater Street in Ottawa, and in vehicles
on long commuting trips, using equipment designed and built by Emissions Research and
Measurement Division (ERMD), Environment Canada. Carleton University graduate
students and research assistants were employed in sampling and data processing while
most of the sample analyses were carried out at ERMD's laboratories. A source emission
study was also undertaken at ERMD laboratories using samples of heavy-duty buses and
light duty vehicles to characterize emissions from these vehicles under simulated driving
conditions.
The ambient sampling stations were located beside a major public transit bus stop on a
one-way artery. The primary roadside sampling station was set-up at pedestrian noselevel, approximately 1.5 m above the sidewalk, 60 cm from the curbside, on the south
sidewalk of Slater Street. A second sampling station was set-up on the rooftop of a threestorey parking structure adjacent to the nose-level sampler. A permanent National Air
Pollution Surveillance (NAPS) network station sampler was located at 88 Slater Street,
within two blocks of the nose-level sampling station. The rooftop sampler was installed
to enable correlation with the data acquired at the NAPS sampling station and nose-level
station. The NAPS and rooftop stations provided observations at different heights (4 m
and 10 m) and sampling periods (24 h) relative to the nose-level.
During periods of high traffic and pedestrian volumes, two-hour, nose-level ambient
samples were obtained for VOCs, SVOCs, carbonyl compounds, and fine particulate
matter (PM2.5). In-vehicle VOC and carbonyl samples were collected for typical long
commuting trips in the region during the same 2-hour periods. On selected days, 24-hour
samples were simultaneously obtained with the 2-hour samples during the day to enable
cross correlation with the NAPS ambient monitoring station at 88 Slater Street. Some
cumulative, 6-hour samples were also collected to obtain sufficient mass on PM2.5 filters.
For the source emission characterization study, two light duty vehicles and two buses
were operated on chassis dynamometers at ERMD laboratories, using commercial fuel
and standard driving cycles and test procedures at two different temperatures (-10 C and
24 C), with 2-3 repeats for each set of conditions. Mass emission rates of regulated and
non-regulated gaseous emissions and PM emissions were determined. The particulate
matter emissions measurements were conducted as part of the PERD funded project
“Determination of the concentration, composition and sources of atmospheric
Measurement and Modelling of Motor Vehicle Related Air Toxics 6
carbonaceous particles in Canada”. The detailed gaseous emissions measurements were
conducted as part of the TSRI project.
3. SUMMARY OF FINDINGS
Over 100 compounds were quantified in the gas phase samples obtained at the roadside
and in-vehicle micro-environments and 40 elemental species quantified in the PM2.5
samples obtained at the roadside micro-environment. These compounds were also
quantified in the source emission samples from vehicles operated at the ERMD
laboratories. The discussion here will focus on the most abundant subset of these species.
The full data set is available on a dedicated web page as detailed in Section 4 below.
3.1 Gas phase samples at the roadside and in-vehicle microenvironments
Gas phase concentrations show significant variation from day to day and between
sessions as demonstrated in Figures 1 and 2. The closed boxes in these figures show the
25th and 75th percentile of the data observed during the sampling session of 20 days, with
the horizontal line in the box showing the median value. The caps on the vertical bars
show the 10th and 90th percentile of the data while free standing horizontal bars represent
outliers.
In the winter, the afternoon sampling session shows noticeably higher concentrations.
This can be attributed to the large number of vehicle which enter the traffic in the coldstart mode after having been parked in downtown locations during the day, whereas for
the morning and noon sessions it may be expected that most vehicles arrive at the
downtown location in a hot stabilized mode of operation.
In the summer, the concentrations are generally lower compared to winter and the relative
rise in the afternoon is not particularly noticeable. It might be expected that the effect of
the cold-start mode is less pronounced under summer conditions.
The 24 hr samples in Figures 1 and 2 were obtained at roadside, nose-level stations and
serve to distinguish the effects of sampling time. Ambient VOC concentrations are also
monitored regularly at the NAPS station on Slater Street, two blocks away from the
roadside station, on the basis of one 24 hr sample every six days, collected at a height of
4 m from the street. Comparison with this ambient monitoring station data is informative
because it gives an indication of the representativeness of routine air quality monitoring
data for the actual exposure of pedestrians during the commuting rush periods in this
microenvironment. Figure 3 compares the median concentrations of the most abundant
species averaged over 24 hours at the NAPS station and the roadside samples analyzed by
ERMD. Measurements at the two stations show remarkable agreement, with minor
scatter. This is somewhat surprising since the analysis of 1994 data at these same
locations had shown marked differences both quantitatively and qualitatively: 2 hour
samples at the roadside stations had shown higher total non-methane hydrocarbons by a
factor of 2-5 and noticeably different hydrocarbon speciation fingerprints explained by
different source contributions.
Measurement and Modelling of Motor Vehicle Related Air Toxics 7
Figure 1 (concentrations in ng/L)
Measurement and Modelling of Motor Vehicle Related Air Toxics 8
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Figure 2 (concentrations in ng/L)
Box Plots Top 15 NMHC Species & 3 Most Abundant Carbonyls
(SLATER STREET - SUMMER )
40
30
20
10
0
40
Measurement and Modelling of Motor Vehicle Related Air Toxics 9
7:30
11:30
3:30
24Hr
30
20
10
0
Figure 3
NAPS winter median conc. (ng/L)
NAPS summer median conc. (ng/L)
Comparison of NAPS 24-Hr (4m) VOC Measurements
with ERMD 24-Hr Nose-level (1.5 m) VOC Mesurements
6
4
2
0
0
2
4
6
ERMD winter median conc. (ng/L)
6
4
2
0
0
2
4
6
ERMD summer median conc. (ng/L)
Measurement and Modelling of Motor Vehicle Related Air Toxics 10
(n g /L )
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B o x P lo ts o f T o p 2 0 C o m p o u n d s fo r 1 9 9 4 C u r b s id e
a n d 2 0 0 0 S la te r 1 5 :3 0 m e a s u r e m e n ts
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60
40
20
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1 9 9 4 C u r b s id e 1 5 : 3 0
60
40
20
Measurement and Modelling of Motor Vehicle Related Air Toxics 11
The distribution, shown in Figure 4, of concentrations observed for a group of
compounds in the afternoon sampling sessions during the Summer 1994 and Summer
2000 studies demonstrates that the Summer 2000 concentrations are indeed noticeably
lower than those in 1994. However, one should be careful not to interpret this as a
general decline as the number of observation days in 2000 is only four, while it was over
15 in 1994. The fewer number of days in 2000 may therefore be contributing to the
narrower spread. Comparison, in Figure 5, of the median concentrations observed for all
three sampling sessions in 1994 and 2000 shows more difference for the morning
sessions than the afternoon sessions shown in Figure 4.
Figure 5.
2000 Slater Street Median Conc. (ng/L)
Comparison of 1994 and 2000 Summer Median Concentrations
40
7:30
11:30
15:30
30
20
10
0
0
10
20
30
40
1994 Curbside Median Conc. (ng/L)
The "rooftop" station used during the 2000 study also provides some opportunity for
comparing the temporal and spatial variation of concentrations observed on Slater Street.
This "station was initially located at the top level of the parking structure adjacent to the
roadside station, about 10 m above the road, to obtain SVOC samples for comparison
with roadside data as the NAPS station did not have SVOC data. During the course of
sampling, VOC canisters were also deployed at this station. 24 hr average samples were
obtained, enabling comparison with both the NAPS station and the roadside station.
Figure 6 compares 24 hr average concentrations for the most abundant species between
the rooftop and the nose level stations for two days, one in the winter, and one in the
summer. There is some scatter in the winter comparison, while the summer comparison
shows somewhat higher concentrations at the nose level station. When 2 hr average
concentrations at nose level are compared with 24 hr average rooftop concentrations
measured during the same day (Figure 7), differences do arise, most notably in the
Measurement and Modelling of Motor Vehicle Related Air Toxics 12
afternoon session. There are a number of days for which this comparison can be made,
but they do not all show the trend in Figure 7. While differences are more likely to arise
for the afternoon or noon samples there are a few days when 2-hour average
concentrations correlate well with the 24 hr average concentrations. Although dispersion
modelling in this complex environment is not among the objectives of the study it is to be
expected that atmospheric mixing conditions play the dominant role in the observed
differences or agreements between these measurements.
Figure 6
Comparison of ERMD 24-Hr Nose-level (1.5 m) VOC Measurements
with ERMD 24-Hr Rooftop (10 m) VOC Mesurements
Summer (29 Jul)
8
ERMD Nose-level conc. (ng/L)
ERMD Nose-level conc. (ng/L)
Winter (6 Feb)
8
6
4
2
0
0
8
6
4
2
ERMD Rooftop conc. (ng/L)
6
4
2
0
6
4
2
0
ERMD Rooftop conc. (ng/L)
Measurement and Modelling of Motor Vehicle Related Air Toxics 13
8
Figure 7
8
8
6
6
roof.01Feb.24hr
roof.01Feb.24hr
2-hr Nose-level Measurements vs 24-hr Rooftop
Measurements for same Days (Concentrations in ng/L).
4
2
0
4
2
0
0
2
4
6
8
0
2
nose.01Feb7.30
4
6
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20
roof.01Feb.24hr
15
10
5
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10
.nose.01Feb.3.30
Measurement and Modelling of Motor Vehicle Related Air Toxics 15
15
20
8
Measurement and Modelling of Motor Vehicle Related Air Toxics 16
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Figure 8. (concentrations in ng/L)
Box Plots Top 15 NMHC Species & 3 Most Abundant Carbonyls
(IN-CAR & IN-BUS - WINTER) )
60
40
20
0
In-Car (PM)
In-Bus (PM)
In-Car (AM)
In-Bus (AM)
60
40
20
0
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Figure 9 (concentrations in ng/L)
Box Plots Top 15 NMHC Species & 3 Most Abundant Carbonyls
(IN-CAR & IN-BUS - SUMMER)
30
20
10
0
In-Car (PM)
In-Bus (PM)
In-Car (AM)
In-Bus (AM)
30
20
10
0
Measurement and Modelling of Motor Vehicle Related Air Toxics 17
Concentrations measured in commuter vehicles also show significant variation from day
to day (Figures 8 & 9) but no discernible pattern between sampling sessions comparable
to that observed for the winter roadside station samples. It should be remembered that the
commuter vehicles travel over a fairly long distance that encompasses a variety of traffic
patterns, in contrast to the pattern of "arrival in the morning, departure in the afternoon"
experienced on a downtown location like Slater Street. They are therefore less likely to
be influenced by the cold-start effect mentioned above for the roadside station in the
winter.
For the middle 50% of the in-vehicle data, the variation between winter and summer is
less pronounced relative to the variation observed at the roadside, but the in-vehicle
winter concentrations are again generally higher. There are very large maxima observed
during the winter session for the in-car data, which can be caused by the car 's relative
position in traffic, e.g. following a high emitting vehicle for a considerable period of
time. The ambient inside a small car is quite responsive to changes in the ambient ahead
of the car due to the positioning of the fresh air intake on the car. In contrast, the ambient
inside a bus is relatively isolated from such changes and the winter data for the bus show
much less variation than the car. The summer session shows more variation when bus
windows may be expected to be at least partially open. When in-vehicle concentrations
are compared to those at the roadside, the median in-vehicle concentrations are
noticeably higher than the roadside concentrations.
Table 1 presents a more detailed comparison of in-vehicle and roadside concentrations
for a select group of compounds important from a human health perspective. For these
compounds the in-vehicle concentrations are quite comparable to roadside concentrations
during winter. During the summer they are higher for the in-vehicle concentrations by a
factor of around two. This spatial variation among micro-environments, while noticeable,
is much less than the temporal variation observed (in Figures 1, 2, 8, and 9) for any one
of these micro-environments over the period of the sampling study.
The in-vehicle microenvironment, which generally shows the highest concentrations for
gas-phase compounds, has been studied by others with whom comparisons are possible.
Table 2 presents in-vehicle concentrations of selected compounds observed in seven
other studies and Figure 10 presents a graphical comparison for Benzene. One of the
studies (Jo and Park 1999) with very high concentrations and variability has been left out
to avoid distorting the scale too much. The in-vehicle benzene concentrations observed
during this study in Ottawa are of the same magnitude as those reported by studies in
other cities but in the lower half of the range of values reported.
To summarize the main findings for the gas-phase measurements that offer comparisons
among all the microenvironments studied, the following can be said.
-
The temporal variation from day to day of pollutant concentrations observed in
micro-environments is much higher than the spatial variation observed among
diverse micro-environments such as the roadside on a busy downtown street, the
rooftop on a parking structure, the inside of a commuter car, and the inside of a
transit bus. Despite the large temporal variations, the median values of 24 hr
Measurement and Modelling of Motor Vehicle Related Air Toxics 18
average concentrations recorded at the ambient monitoring station on Slater street
at a height of 4 m are in general agreement with the median values of 2 hour
average concentrations recorded at nose-level along the same street.
-
There are noticeable differences between 2-hour average concentrations recorded
at nose level and 24-hour average concentrations recorded at a height of 10 m, on
the roof of an adjacent parking structure. Nearly all of the difference is due to the
sample averaging time since the comparison of 24 hr average concentrations at
these two locations shows reasonably close agreement.
Table 1.
Comparison of select compound
microenvironments for different seasons
concentrations
in
different
Winter mean concentrations, (micrograms/m3)
Compound
In-car
In-bus
Roadside
Car/Road Bus/Road
Benzene
5.06 ± 2.69
3.38 ± 1.38
4.24 ± 3.17
1.2
0.8
Toluene
18.05 ± 14.48
9.62 ± 5.15 14.41 ± 13.74
1.3
0.7
Ethylbenzene
3.09 ± 3.24
2.58 ± 1.23
2.49 ± 2.62
1.2
1.0
m,p-xylene
9.25 ± 9.97
6.93 ± 3.29
7.33 ± 7.41
1.3
0.9
o-xylene
3.93 ± 4.15
3.04 ± 1.29
2.87 ± 2.88
1.4
1.1
1,3-butadiene
BDL
BDL
0.38 ± 0.64
NA
NA
Formaldehyde
7.00 ± 2.60
3.50 ± 3.36
3.89 ± 1.59
1.8
0.9
Acetaldehyde
2.00 ± 2.04
2.50 ± 2.46
2.80 ± 1.17
0.7
0.9
Summer mean concentrations (micrograms/m3)
Compound
In-car
In-bus
Roadside
Car/Road Bus/Road
Benzene
5.33 ± 1.50
3.46 ± 1.00
2.16 ± 0.86
2.5
1.6
Toluene
15.66 ± 7.45 11.53 ± 3.58
7.75 ± 3.04
2.0
1.5
Ethylbenzene
2.90 ± 1.30
3.57 ± 1.77
1.36 ± 0.78
2.1
2.6
m,p-xylene
6.00 ± 2.32
7.06 ± 2.77
3.17 ± 1.84
1.9
2.2
o-xylene
2.23 ± 0.81
2.85 ± 1.01
1.20 ± 0.73
1.9
2.4
1,3-butadiene
1.13 ± 0.81
1.08 ± 0.58
0.81 ± 0.48
1.4
1.3
Formaldehyde
10.40 ± 2.39 10.50 ± 2.97 8.19 ± 11.55
1.3
1.3
Acetaldehyde
6.01 ± 1.97
5.93 ± 2.05
2.39 ± 0.61
2.5
2.5
3.2 Particulate matter samples at the roadside microenvironment
Figure 11 presents the minimum, 25th percentile, 75th percentile, and maximum PM2.5
mass concentration for wintertime and summer-time sampling sessions. Median mass
concentrations for the morning and evening sessions are similar and somewhat higher
than the midday sessions. The summer median mass concentrations for morning and
evening sessions were approximately 50% higher than in winter. Weekend 6-hr samples
were collected by accumulating the sample over the three 2-hr sampling periods used
during weekdays in an effort to obtain sufficient mass on the filter for metals analysis.
The median concentrations for these samples are lower than the 2-hour average samples.
Measurement and Modelling of Motor Vehicle Related Air Toxics 19
Table 2. Mean in-vehicle concentrations (g/m3) of VOCs and carbonyl compounds for comparable studies.
m&pxylene
30.5  17.2
71.8  75.7
40.60
Ethyl
benzene
8.8  4.9
24.8 
18.9
12.5 
11.3
14.10
11.4  6.2
1,3butadiene
3.3  2.4
Form
aldehyde
NA
Acet
aldehyde
NA
53  41.9
NA
NA
NA
NA
NA
NA
34.60
25.6 
13.1
17.00
BDL
6
3.9
5.80  4.70
23.2  12.8
3.50  3.0
9.30  6.4
3.90  3.6
BDL
24.3  10.1
91.5  75.8
7.7
31.0
NA
2.7
2.5
NA
NA
NA
5.1
8.8
NA
4.8
1.7
NA
NA
NA
3.6
NA
NA
5.5
2.1
NA
NA
NA
15.6  1.6
NA
NA
NA
NA
5.2  0.5
NA
NA
20.3  3.5
NA
NA
NA
NA
6.3  0.8
NA
NA
Reference
Study
Benzene
toluene
Chan et al., 1991a
Raleigh, NC, 1988
South Korea, in-car,
winter 1996-1997
South Korea, in-bus,
winter 1996-1997
Toronto, winter 1994
Toronto,
summer
1994
Birmingham,
UK,
1996
Boston, winter 1989
New Jersey, winter
1991
Sydney,
Australia,
1996
(morning
commute)
Sydney,
Australia,
1996
(evening
commute)
11.6  6.9
46.5  27.3
60.2  50.9
181  158
21.3  19.2
84.1  41.6
20.10
Jo and Park, 1999
Novamann, 1994
Leung
and
Harrison, 1999
Chan et al., 1991b
Weisel et al., 1992
Duffy and Nelson,
1997
Measurement and Modelling of Motor Vehicle Related Air Toxics 20
28.8  16.1
o-xylene
Figure 10. Mean concentrations of benzene (g/m3)  standard deviation for the present study and previous studies in the
literature
80
70
Concentration (ug/m3)
60
50
40
30
20
10
98
9
96
r1
te
,w
in
to
n
Bo
s
in
rm
Bi
19
94
gh
am
,U
K,
m
m
su
ro
nt
o,
To
nt
o,
ro
To
er
r1
te
w
in
,N
ei
gh
19
99
4
98
8
C
,1
20
-b
in
w
a,
tta
O
Measurement and Modelling of Motor Vehicle Related Air Toxics 21
R
al
us
,
-b
us
,
su
m
w
in
te
m
er
r2
00
00
0
00
20
O
tta
w
a,
in
O
tta
w
a,
w
a,
tta
O
in
-c
in
ar
-c
,s
um
ar
,w
in
te
m
er
r2
00
0
0
Figure 11. PM2.5 mass concentration for a) 2000 wintertime sampling sessions and b)
2000 summertime sampling sessions. (Minimum, 25th percentile, 75th percentile, and
maximum values indicated)
50
Concentration, ng/L
45
40
35
30
25
20
15
10
5
0
7:30 to 9:30 a.m.
11:30 a.m. to 1:30 p.m.
3:30 to 5:30 p.m.
weekend 6 hr
3:30 to 5:30 p.m.
weekend 6 hr
Weekday 24 hr
50
Concentration , ng/L
45
3)
40
35
30
25
20
15
10
5
0
Weekday 24 hr
7:30 to 9:30 a.m.
11:30 a.m. to 1:30 p.m.
The 24-hr samples were collected to compare the effects of averaging times on observed
concentrations and coincided with 24 hour VOC samples collected on NAPS sampling
days. The 24 hour median concentration was lower in the summer at 10.3 g/m3
compared to 18.3 g/m3 observed in the winter but there were only two samples in the
summer. The median PM2.5 mass concentrations for the winter and summer 2000 are
compared with TSP mass concentration measurements from the summer of 1994 in
Figure 12. While TSP concentration is an order of magnitude higher than the PM 2.5
concentration, there is also a different pattern between TSP sessions and PM 2.5 sessions.
The TSP mass concentration declines as the day progresses, whereas PM2.5 mass
concentrations are higher during the morning and afternoon sessions when there was a
higher volume of traffic than the midday session.
Measurement and Modelling of Motor Vehicle Related Air Toxics 22
Figure 12. Mass concentration for winter 2000 PM2.5, summer 2000 PM2.5 and
summer 1994 TSP.
160
Winter 2000
140
Summer 2000
Summer 1994 TSP
Concentration, ng/L
120
100
80
60
40
20
0
7:30 to 9:30 a.m.
11:30 a.m. to 1:30 p.m.
3:30 to 5:30 p.m.
weekend 6 hr
NAPS 24 hr
The elemental carbon and organic carbon content of PM2.5 for winter and summer 2000
sessions are presented in Figure 13. The median OC concentrations for the morning and
evening sessions were higher than the noon and 6 hr sessions for both winter and
summer, similar to the trends observed for total PM2.5 mass.
Figure 13: OC and EC concentrations for winter and summer 2000 roadside PM2.5
samples (minimum, median and maximum values indicated)
30
EC
OC
Median Concentration (ug/m 3)
25
20
15
10
5
0
7:30 -9:30
Winter
7:30 -9:30
Summer
11:30 - 1:30
Winter
11:30 - 1:30
Summer
3:30 -5:30
Winter
3:30 -5:30
Summer
w eekend 6 hr w eekend 6 hr
Winter
Summer
NAPS 24 hr
Winter
NAPS 24 hr
Summer
The OC content comprised 70 to 90 % of the total carbon content for the winter samples
and 45 to 75% for the summer samples. Elemental carbon on the other hand showed
different trends between summer and winter with noticeably higher absolute values and
shares in the summer.
Measurement and Modelling of Motor Vehicle Related Air Toxics 23
Figure 14 presents concentrations of the 13 most abundant metals in PM2.5 samples for
each wintertime sampling session. The predominant elements observed were silicon,
sulphur and chlorine. The chlorine is likely from road salt, which is in abundant use in
Ottawa during the winter months.
Figure 14. Minimum, median and maximum PM2.5 metals concentration (g/m3)
during each wintertime sampling session.
4.5
7:30 to 9:30 a.m.
11:30 a.m. to 1:30 p.m.
4.0
3:30 to 5:30 p.m.
weekend 6 hr
24 hr
3
Min, Median and Max Concentration (ug/m )
3.5
3.0
2.5
2.0
1.5
1.0
0.5
Metal
Measurement and Modelling of Motor Vehicle Related Air Toxics 24
Zn
Fe
Mn
Sc
Ca
K
Cl
S
P
Si
Al
Mg
Na
0.0
3.3 Vehicle emissions sampling
The emissions from two diesel city transit buses and two gasoline light duty vehicles
were measured and characterized, primarily with a view to developing source emission
profiles that were later used in source apportionment by Chemical Mass Balance receptor
modelling.
Diesel Buses
The two in-use urban buses of different vintages were tested at 20 C and -10 C on a
chassis dynamometer over the Central Business District (CBD) test cycle. The first bus
had an older technology engine and was part of an exhaust after-treatment demonstration
study conducted by ERMD. This bus was tested in two configurations, with the OEM
muffler installed and with the oxidation catalyst installed. This particular bus sees in-use
service with the local transit authority with the oxidation catalyst installed, but other
buses of the same type have no exhaust after-treatment device installed. The second bus
was a new, state-of-the-art urban bus just introduced into service by the local transit
authority.
Approximately 165 volatile organic compounds (non-methane hydrocarbons) in the range
of C1 to C26 were determined in the samples collected from buses. Figure 15 presents the
mass emission rate profiles over the entire range of compounds while Table 3 gives
details of emission rates for the sub-set of compounds selected for the receptor modelling
as outlined in Section 3.4. Complete data are available at the OMDB web site (7). The
oxidation catalyst used with the older bus achieves noticeable reductions for some
compounds while there seem to be increases in others. The new technology achieves
much lower emission rates than the older bus in either configuration. For example,
Benzene emissions are reduced by approximately 10% with the oxidation catalyst at 20 C
while the new technology bus reduces benzene emissions by more than 90%. Reductions
are less at the cold temperature but the new technology vehicle still achieves reductions
of around 90%.
Passenger Cars
Two light duty vehicles were also tested (a 1994 model year Neon and a 2000 model
year Intrepid) at 24 C and -10 C, using Cold Start and Hot Start LA-4 test cycles with
local summer grade commercial fuel. These tests enabled the determination of nonmethane hydrocarbon profiles in the C2 to C12 range that characterize the exhaust
emissions when the vehicles are operated in the cold transient, hot stabilized and hot
transient modes of the test procedure used to regulate emissions from light duty vehicles.
Figure 16 presents the normalized profiles for the sum of compounds selected for
receptor modelling. Complete data are available at the OMDB web site (7).
Measurement and Modelling of Motor Vehicle Related Air Toxics 25
180
Emission Rate (mg/mile)
160
20 oC
140
Muffler
120
OxyCat
100
New
80
60
40
20
0
1
11
21
31
41
51
61
71
81
91
101 111 121
131 141 151 161
Compound ID Number
180
160
o
Emission Rate (mg/mile)
-10 C
140
Muffler
120
OxyCat
New
100
80
60
40
20
0
1
11
21
31
41
51
61
71
81
91
101
111
121
131
141
151
161
Compound ID Number
Figure 15. Mass emission rates of C2-C26 compounds from buses operated at two
different temperatures.
Measurement and Modelling of Motor Vehicle Related Air Toxics 26
CMB
Species
#
2
5
8
9
6
13
7
27
26
4
42
30
12
40
31
28
29
37
24
11
15
17
21
34
14
38
23
33
18
22
25
39
32
3
36
41
35
19
10
20
16
ERMD
Analysis
Diesel #
1
2
3
4
5
6
9
11
12
15
18
21
22
23
24
25
27
28
31
32
34
35
38
46
47
50
52
53
54
57
61
63
67
71
72
75
77
83
94
97
102
122
methane
ethylene
acetylene
ethane
propylene
propane
isobutene/1-butene
n-butane
t2-butene
c2-butene
2m-butane
1-pentene
2m1-butene
n-pentane
2m-13-butadiene
t2-pentene
2m2-butene
22-dm-butane
cyclopentane
23-dm-butane
2m-pentane
3m-pentane
n-hexane
m-cyclopentane
24-dm-pentane
benzene
cyclohexane
2m-hexane
23-dm-pentane
3m-hexane
224-tm-pentane
n-heptane
m-cyclohexane/22-dm-hexane
234-tm-pentane
toluene/233-tm-pentane
2m-heptane
3m-heptane/…
n-octane/t12-dm-cyH
e-benzene
m&p-xylene/34-dm-heptane
o-xylene & 112-tm-cyH
124-tm-benz/tb-benz/1-decene
Emission data in mg/mile
Muffler
Muffler
OxyCat
20C
-10C
20C
3.23
5.21
163.82
145.90
125.21
30.52
28.34
0.86
2.25
72.55
64.33
51.38
0.59
0.15
1.87
OxyCat
-10C
4.62
129.83
5.36
2.27
53.41
0.27
New
20C
New
-10C
54.56
57.83
3.11
11.78
13.76
21.10
2.72
0.16
0.41
0.31
0.48
1.10
0.86
0.61
0.47
0.19
0.48
1.31
0.65
1.37
0.94
0.63
4.52
0.12
1.82
1.14
1.34
3.52
0.26
1.10
0.89
0.79
0.19
0.71
1.57
1.01
0.80
3.30
0.24
0.41
0.20
0.45
1.27
0.64
0.10
0.08
0.20
0.31
3.08
6.64
0.04
27.53
0.34
0.21
0.13
0.31
0.59
0.08
0.69
1.08
3.68
3.72
0.35
27.42
1.33
0.82
0.49
1.18
0.35
0.16
1.24
0.60
2.70
1.24
0.19
21.90
1.39
1.12
0.64
4.90
26.01
1.26
0.90
0.52
14.02
1.88
0.15
0.24
0.29
2.54
0.42
0.11
0.10
0.39
10.08
1.28
0.06
30.09
6.53
1.27
51.22
13.72
41.13
22.96
61.22
10.00
5.19
0.09
26.81
2.17
5.06
50.83
16.61
42.08
23.05
63.19
7.80
5.60
0.19
20.42
2.73
5.88
47.07
9.07
27.81
12.75
33.78
9.99
4.98
0.09
24.09
6.02
5.16
50.54
12.29
34.10
16.78
46.04
0.33
0.34
0.27
0.44
0.48
0.63
0.72
0.35
0.45
0.48
1.89
1.23
0.25
0.73
0.71
1.04
1.97
1.20
2.66
0.56
0.74
0.85
0.18
0.76
1.39
2.82
0.68
1.37
0.15
0.24
0.10
0.05
0.46
0.20
0.07
0.12
0.03
0.21
0.37
0.07
0.12
0.69
0.40
Table 3. Mass emission rates of selected compounds from buses operated at two
different temperatures.
Measurement and Modelling of Motor Vehicle Related Air Toxics 27
0.12
0.66
0.16
op
a
n-
ne
bu
ta
ne
c2
-b
ut
en
e
1pe
nt
en
e
npe
nt
an
e
t2
-p
en
te
22
ne
-d
m
-b
ut
23
an
-d
e
m
-b
ut
an
3m
e
-p
en
m
ta
-c
ne
yc
lo
pe
nt
an
e
be
nz
en
e
2m
-h
ex
an
e
3m
-h
ex
an
e
nhe
23
pt
an
4tm
e
-p
en
ta
ne
2m
n-h
oc
m
ep
ta
&
ne
ta
12
pne
xy
/t1
4le
tm
2ne
dm
-b
/
en
34
-c
ze
-d
yH
m
ne
-h
/tb
e
-b
pt
an
en
e
z/
1de
ce
ne
pr
e
ne
le
n
et
ha
et
hy
Fraction of named compounds
hy
le
ne
et
ha
ne
pr
op
an
e
nbu
ta
ne
c2
-b
ut
en
1pe e
nt
en
ne
pe
nt
a
ne
t2
-p
22 ent
e
-d
ne
m
23 but
a
-d
ne
m
-b
ut
an
3m
e
-p
m
en
-c
ta
yc
ne
lo
pe
nt
an
e
be
nz
e
2m
ne
-h
ex
3m ane
-h
ex
an
nhe e
23
p
4tm tan
e
-p
en
ta
n2
ne
m
oc
12 m &
-h
ta
p
ep
4ne
tm -xyl
t
/t1
an
en
-b
2e
en
e/
dm
34
ze
-d
cy
ne
m
H
/tb
-h
-b
ep
en
ta
z/
ne
1de
ce
ne
et
Fraction of named compounds
LDGV (Intrepid) Exhaust, FTP at 20 C
0.18
0.16
0.14
0.12
0.1
0.08
Bag 1
Bag 2
Bag 3
0.06
0.04
0.02
0
LDGV Exhaust (Neon), FTP at - 10 C
0.16
0.14
0.12
0.1
0.08
Bag 1
Bag 2
0.06
Bag 3
0.04
0.02
0
Figure 16. Normalized C2-C12 HC emission profiles of light duty vehicles under
different operating conditions
Measurement and Modelling of Motor Vehicle Related Air Toxics 28
3.4 Chemical Mass Balance Receptor Modelling
Source apportionment for the VOC concentrations measured on Slater Street was carried
out using the Chemical Mass Balance receptor model, CMB8. (8)
It can be expected that the total VOC concentrations measured in ambient samples on a
major downtown street will be dominated by the emission sources related to mobile
sources. Other emission sources such as architectural coatings, emissions related to graphic
arts, etc. can be considered, although at significantly lower strengths. Major source types
of interest for mobile source emissions are tailpipe emissions under different modes of
operation, resting evaporative emissions associated with "hot soak" and diurnal heat buildup situations, "running" emissions that combine tailpipe and evaporative emissions for
moving vehicles, and the emissions associated with the fuelling operations. A number of
source profiles have been published characterizing these source types and the SPECIATE
database provides access to a large compilation (9). These profiles can contain as many as
75 hydrocarbon species in the C2-C10 range, comprising saturated, unsaturated, cyclic and
aromatic species.
The profiles available in the SPECIATE database were augmented by the diesel and
gasoline exhaust profiles developed through vehicle emission testing completed as part of
the current study, as explained in Section 3.3 above. The complete list of profiles included
in the CMB8 modelling exercise is presented in Table 4.
The list of compounds to be used in receptor modelling was governed by the availability of
component data in the SPECIATE profiles and the relative importance of the compound in
terms of the total mass measured in the ambient samples. The CMB8 Application and
Validation document (10) focuses on the target list of compounds for the PAMS (11)
network in the U.S. and identifies the compounds used as fitting species in source
apportionment studies with this data set. The CMB8 Application and Validation document
is summarized in a review article (12). The list of chemical compounds used in the
modelling exercise was arrived at by reconciling the list of compounds from the above
sources with the list of compounds that were responsible for ~90% of the total measured
mass in our ambient samples. The complete list is presented in Table 3, previously
mentioned in connection with diesel bus source profiling.
CMB8 modelling results are presented below for the median profiles for each of the three
daily sampling sessions in the two seasons. Screening runs were first completed with
various source profiles from Table 4 to arrive at a set that included the types of sources
expected to contribute to ambient measurements and explain the observations. Table 5
presents CMB8 summary results with a profile set that includes some profiles from the
SPECIATE database and some profiles that were obtained from the vehicle emission
testing completed in this study. Figure 17 presents these data in graphical form.
Measurement and Modelling of Motor Vehicle Related Air Toxics 29
CODE
DIES1
DIES2
DIES3
DIES4
DIES5
DIES6
DIES7
DIES8
LPG01
GASL1
GASL2
GASV1
GASV2
GASV3
GASV4
GASV5
GASE1
GASE2
GASE3
GASE4
GASE5
GASE6
GASE7
GASE8
GASE9
HOSO1
HOSO2
HOSO3
HOSO4
HOSO5
HOST1
REFU1
COST1
COST2
COST3
COST4
COST5
COMB1
COMB2
DRYC1
PRNT1
PRNT2
ROAD
WGAS1
WGAS2
WGAS3
WGAS4
HESP1
HESP2
DM20
DM-10
DOC20
DOC-10
DN20
DN-10
BAG120C
BAG220C
BAG320C
BAG110C
BAG210C
BAG310C
SPECIATE profile # and description
#2530/Vehicle Exhaust - Van Nuys Tunnel, Diesel and Minimum Running Loss Subtracted - June 8-12, 1995
#2524/Vehicle Exhaust - Sepulveda Tunnel Diesel and Minimum Running Loss Subtracted - Oct. 3-4, 1995
#2525/Vehicle Exhaust - Sepulveda Tunnel Diesel and Maximum Running Loss Subtracted - Oct. 3-4, 1995
#2518/Vehicle Exhaust - Lincoln Tunnel Diesel and Minimum Running Loss Subtracted - Aug. 16-18, 1995
#2519/Vehicle Exhaust - Lincoln Tunnel Diesel and Maximum Running Loss Subtracted - Aug. 16-18, 1995
#2513/Vehicle Exhaust - Callahan Tunnel Diesel Exhaust Subtracted - Sept. 18-19, 1995
#2514/Vehicle Exhaust - Callahan Tunnel Diesel and Minimum Running Loss Subtracted - Sept. 18-19, 1995
#2015/Vehicle Exhaust - Callahan Tunnel Diesel and Maximum Running Loss Subtracted - Sept. 18-19, 1995
#2445/LPG from Servigas & Commercial de Juarez - 1996
#2448/Composite Gasoline Liquid, El Paso - 1996
#2447/Composite Gasoline Liquid from Los Angeles, Summer 1995 Fed Phase 1 RFG
#2452/Gasoline Vapor, Hot-Soak, Downwind-Upwind Sample from the Astrodome - 1996
#2451/Gasoline Vapor, Hot-Soak, Downwind Sample from the Astrodome - 1996
#2453/Composite of 14 Gasoline Headspace Vapor Samples - 1996
#2454/Composite Gasoline Vapor from Los Angeles, Summer 1995
#2450/Composite Gasoline Vapor from Boston, Summer 1995, Fed Phase 1 RFG
#2521/Vehicle Exhaust - Tuscarora Tunnel Light Duty Gasoline - 1995
#2527/Vehicle Exhaust - Fort McHenry Tunnel Light-Duty Gasoline - 1995
#1203/Light-Duty Gasoline Vehicles - Exhaust
#1204/Light-Duty Gasoline Vehicles - Evaporative
#1101/Light Duty Gasoline Vehicles - 46 Car Study
#1313/Industry Average (circa 1990) Gasoline Exhaust
#1186/Heavy Duty Gasoline Trucks
#1315/11% MTBE Exhaust
#1314/10% Ethanol Exhaust
#2502/Vehicle Exhaust - Older Fleet (1983-1985) Hot Soak Evaporative
#2495/Vehicle Exhaust - Current Fleet (1989) Hot Soak Evaporative
#2452/Gasoline Vapor, Hot-Soak, Downwind-Upwind Sample from the Astrodome - 1996
#2451/Gasoline Vapor, Hot-Soak, Downwind Sample from the Astrodome - 1996
#1311/11% MTBE Hot Soak
#2501/Vehicle Exhaust - Older Fleet (1983-1985) Hot Start
#1100/Refueling
#2505/Vehicle Exhaust - Tip O'Neill Garage (Boston) Cold Start - Sept.12-13, 1995
#2499/Vehicle Exhaust - Older Fleet (1983-1985) Cold Start
#2492/Vehicle Exhaust - Current Fleet (1989) Cold Start
#2506/Vehicle Exhaust - Cold-Start, Downwind Sample from the Astrodome - 1993
#2507/Vehicle Exhaust - Astrodome, Cold Start, Downwind-upwind.- 1993
#1001/Internal Combustion Engine - Natural Gas
#9002/Internal Combustion - Average
#9017/Drycleaning/Degreasing - Average
#9026/Printing/Publishing - Average
#2553/Offset Printing - Plant C, Room Composition
#2564 Atlanta roadway
#7003 Atlanta whole gas weighed average of all octanes
#7004 Atlanta whole gas 87 octane
#7005 Atlanta whole gas 89 octane
Atlanta whole gas 92/93 octane
Conner, T.L., Lonneman, W.A., Seila, R.L., 1995, AWMA Journal, Vol.45, pp. 383-394.
Atlanta headspace gas 24C
Conner, T.L., Lonneman, W.A., Seila, R.L., 1995, AWMA Journal, Vol.45, pp. 383-394.
Atlanta headspace gas 32 C
Conner, T.L., Lonneman, W.A., Seila, R.L., 1995, AWMA Journal, Vol.45, pp. 383-394.
ERMD Diesel bus (original muffler) at 20 C
ERMD Diesel bus (original muffler) at - 10 C
ERMD Diesel bus with oxidation catalyst at 20 C
ERMD Diesel bus with oxidation catalyst at - 10 C
ERMD New Technology diesel bus at 20 C
ERMD New Technology diesel bus at - 10 C
ERMD FTP Phase 1 (Cold transient) at 20 C from Intrepid
ERMD FTP Phase 2 (Hot stabilized) at 20 C from Intrepid
ERMD FTP Phase 3 (Hot transient) at 20 C from Intrepid
ERMD FTP Phase 1 (Cold transient) at - 10 C from Neon
ERMD FTP Phase 2 (Hot stabilized) at - 10 C from Neon
ERMD FTP Phase 3 (Hot transient) at -10 C from neon
Table 4. Source HC profiles used in CMB modelling
Measurement and Modelling of Motor Vehicle Related Air Toxics 30
SITEID
ROSUM7 ROSUM11 ROSUM15
DATE
Median
Median
Median
ST
7:30
11:30
15:30
DR
2
2
2
SIZE
VOC
VOC
VOC
CONC
75.98
68.52
89.08
UCONC
15.45
15.96
18.96
RSQUAR
0.88
0.87
0.88
CHISQUAR
1.72
2.11
2.03
PCMASS
94.79
97.49
99.13
9
6.82
5.15
4.64
LPG01
0.82
0.63
0.60
20
0.68
1.14
1.23
GASE4
1.03
0.88
0.88
SITEID
ROWIN7 ROWIN11 ROWIN15
DATE
Median
Median
Median
ST
7:30
11:30
15:30
DR
2
2
2
SIZE
VOC
VOC
VOC
CONC
72.86
92.36
195.33
UCONC
15.15
17.60
28.50
RSQUAR
0.98
0.97
0.97
CHISQUAR
0.52
0.57
0.71
PCMASS
103.12
102.32
100.92
9
7.01
7.68
4.65
LPG01
1.10
1.27
1.63
23
GASE7
41
PRNT1
54
DOC20
58
BAG120C
60
BAG320C
0.98
1.96
2.45
2.88
39.28
6.42
21.82
3.66
1.25
1.70
0.00
0.00
42.29
4.79
16.98
3.02
0.52
2.25
0.00
0.00
67.68
5.84
14.24
3.54
38
COMB1
41
PRNT1
55
DOC-10
61
BAG110C
63
BAG310C
2.46
2.37
4.74
1.44
1.93
1.97
4.37
2.58
38.50
5.05
16.13
6.04
3.59
2.96
4.58
1.67
1.12
2.19
7.15
3.77
48.82
6.12
21.56
7.28
1.20
5.66
0.54
2.72
2.46
3.04
2.57
4.02
142.93
12.26
42.77
13.98
Table 5. Summary output from CMB8 Modelling
CONC: Measured concentrations, micrograms per cubic meter
UCONC: Uncertainties in measured concentrations, micrograms per cubic meter
RSQUAR, CHISQUAR: CMB8 goodness of fit criteria
PCMASS: Modelled total concentration as % of measured total concentration
9, 20, 23, 38, 41, 54, 55, 58, 61, 63: Source profile numbers, the values in the rows containing these source
numbers are the contribution of the respective source to the total modelled concentration.
LPG01, GASE4, GASE7, COMB1, PRNT1, DOC20, DOC-10, BAG120C, BAG110C, BAG320C,
BAG310C: Source codes, the values in the rows containing these source codes are the uncertainties in the
contribution of the respective source, one line above.
Measurement and Modelling of Motor Vehicle Related Air Toxics 31
Winter HC Source Apportionment
250.00
micrograms per cubic meter
200.00
BAG310C
BAG110C
DOC-10
PRNT1
COMB1
GASE7
LPG01
150.00
100.00
50.00
0.00
7:30
11:30
15:30
Sessions
Summer HC Source Apportionment
100.00
90.00
micrograms per cubic meter
80.00
70.00
BAG320C
BAG120C
DOC20
PRNT1
GASE4
LPG01
60.00
50.00
40.00
30.00
20.00
10.00
0.00
7:30
11:30
15:30
Sessions
Figure 17. Source contribution estimates during sampling sessions
Measurement and Modelling of Motor Vehicle Related Air Toxics 32
Discussion of CMB8 Results
For the summer sessions, the sources with estimable contributions were:
LPG01
Liquefied petroleum gases
GASE4
Light Duty Gasoline Vehicle evaporative emissions
PRNT1
Printing/publishing emissions
DOC20
Heavy Duty Diesel Vehicle exhaust
BAG120C Light Duty Gasoline Vehicle Exhaust in the cold transient mode
BAG320C Light Duty Gasoline Vehicle Exhaust in the hot transient mode
For the winter sessions, the sources with estimable contributions were:
LPG01
Liquefied petroleum gases
GASE7
Heavy Duty Gasoline Vehicle Exhaust
COMB1
Natural Gas vehicle exhaust
PRNT1
Printing/publishing emissions
DOC-10
Heavy Duty Diesel Vehicle exhaust
BAG110C
Light Duty Gasoline Vehicle Exhaust in the cold transient mode
BAG310C
Light Duty Gasoline Vehicle Exhaust in the hot transient mode
In addition to the source profiles with estimable contributions listed above, the final set that
was tried included the following two profiles that were not found to have estimable
contributions:
for the summer sessions:
BAG220C
Light Duty Gasoline Vehicle Exhaust in the hot stabilized mode (20 C)
for the winter sessions:
BAG210C
Light Duty Gasoline Vehicle Exhaust in the hot stabilized mode (-10 C)
The immediate result from the above modelling is that the measured concentrations are
explained mostly by light duty gasoline vehicle exhaust. Contributions from other sources
such as heavy-duty diesel vehicle exhaust or light duty gasoline vehicle evaporative
emissions that may have been expected to be significant are at relatively low levels and
associated with high uncertainties. The dominance of light duty gasoline vehicle exhaust is
in contrast to source apportionment carried out earlier (13) on data collected in the Summer
of 1994 when evaporative sources and heavy duty diesel exhaust were found to be more
significant contributors.
The 1994 data are all in the summer season while the 2000 data are split approximately 3:1
in favour of winter samples. The evaporative GASE4 profile appears in the summer
sessions, albeit somewhat weaker than might be anticipated. Its absence from winter
sessions is understandable. Although locally derived exhaust profiles (from ERMD) were
Measurement and Modelling of Motor Vehicle Related Air Toxics 33
available for the modelling exercise, the evaporative profile used comes from a study in
Atlanta and may not be particularly representative of evaporative profiles in Ottawa. In the
absence of better resolution of evaporative type emissions from exhaust emissions it may
be reasonable to suspect that some of the LDGV exhaust contribution may in fact be a
surrogate for evaporative emissions.
It was notable that among the HDDV exhaust profiles derived in this study, the profile with
the oxidation catalyst gave the better fit. For the LDGV exhaust profiles, the cold start and
hot start modes were favoured, relative to the hot stabilized mode of operation. The more
distinctive features of HDDV exhaust relative to LDGV exhaust are manifested in the
higher hydrocarbons C12-C26. When the list of compounds used in the modelling does not
extend into this range due to lack of ambient data, it becomes more difficult to resolve the
two types of exhaust.
The absence of the GASE7 profile from the summer sessions is not easily explainable since
the presence of heavy-duty gasoline vehicles in the fleet should not be season related. On
the other hand, the contribution is a small one, associated with large relative uncertainty.
The difference should therefore not be given undue weight.
The presence of the COMB1 profile only in the winter is equally surprising from the
vehicle fleet perspective but may be explained by possible contributions from stationary
natural combustion sources in the winter. Its contribution is also small and associated with
a large relative uncertainty.
The overall statistical indicators of RSQUAR and CHISQUAR in Table 5 should be
considered good (8), although the winter sessions have somewhat better indicators. The
uncertainties in the source contribution estimates (t-statistics) should be considered good
for the major sources but not adequate for the minor sources (8). Figure 18 demonstrates
the relative importance of the uncertainties for the particular case of the winter 7:30
session. The goodness of fit in terms of individual components is demonstrated in Figure
19 for the same session. While most compounds show good agreement between
measured and modelled concentrations (thus resulting in the good overall statistics
mentioned above), some compounds have significant difference between measured and
modelled concentrations justifying further investigation into source and ambient profiles.
Conclusions of Source Apportionment from CMB8 Modelling
The measured concentrations of hydrocarbons on Slater Street in 2000 (in the range ~70200 micrograms per cubic meter) are explained dominantly by light duty gasoline vehicle
exhaust in the cold start and hot start modes of operation. These source contributions are
determined by using locally measured light duty gasoline vehicle exhaust profiles.
Locally derived evaporative emission profiles and the extension of ambient data to
heavier hydrocarbons may enable finer resolution between exhaust vs. evaporative
emissions for gasoline vehicles, and gasoline vs. diesel exhaust emissions.
Measurement and Modelling of Motor Vehicle Related Air Toxics 34
Uncertainties in source contribution estimates (Winter 7:30)
50.00
45.00
40.00
micrograms per cubic meter
35.00
30.00
25.00
20.00
15.00
10.00
5.00
0.00
LPG01
GASE7
COMB1
PRNT1
DOC-10
BAG110C
BAG310C
-5.00
Figure 18. Uncertainties in source contribution estimates
Measured and modelled profiles (Win 7:30)
9
Data
8
Model
7
micrograms per cubic meter
6
5
4
3
2
1
Measurement and Modelling of Motor Vehicle Related Air Toxics 35
TM
BE
MP
XY
HE
NO
CT
2M
TM
PN
HE
Figure 19. Goodness of fit for individual compounds
NH
EP
3M
HE
2M
BE
NZ
MC
PE
PE
3M
DM
BU
E
DM
BU
T2
P
NP
EN
1P
EN
C2
BU
PR
O
NB
UT
-1
ET
H
EH
Y
0
4. DISSEMINATION OF RESULTS
The microenvironment database that has been generated in this study, including the
earlier study in 1994, is being made available to interested researchers through a web
page:
http://www.carleton.ca/~dkarman/OMDB
The web site includes detailed descriptions of the experimental methodology and
pictorial orientation to the Slater street site, as well as complete data in electronic
spreadsheet format. Additional figures, too numerous to include in this report are also
available in PowerPoint format. It is hoped that in this way the data will be available to
wider scrutiny, analysis, and discussion.
The following conference presentations have been made:
1. Karman, D., Noseworthy, L., Graham, L. A., Oguz, O., Motor Vehicle Related Air
Toxic Measurements Along an Urban Street, International Symposium on the
Measurement of Toxic and Related Air Pollutants, Air & Waste Management
Association & U.S. EPA, Research Triangle Park, September 2000.
2. Karman, D., Oguz, O., Akay, G., and Graham, L. A., Measurement of Air Toxics in
the Cabins of Commuter Vehicles Under Summer and Winter Conditions in
Ottawa, Canada, 11TH CRC ON-ROAD VEHICLE EMISSIONS WORKSHOP,
San Diego, California, March 26-28, 2001.
3. Karman, D., Welburn, C., and Graham, L.A. Mass Emissions Rates and Chemical
Characterization of PM2.5 Emissions from Two motorcycles, 11TH CRC ONROAD VEHICLE EMISSIONS WORKSHOP, San Diego, California, March 26-28,
2001.
4. Oguz, O., Tuncel, G., Karman, D., Trafikten Kaynaklanan Uçucu ve Yarı Uçucu
Organik Bileşiklerin Belirlenmesi ve Mevsimsel Değişimlerinin İncelenmesi, IV.
National Conference of Turkish Chamber of Environmental Engineers, İçel, Turkey,
September 7-10, 2001.
5. Oguz, O., Tuncel, G., Karman, D., Measurement of Traffic Related Toxic Air
Pollutants in an Urban Atmosphere, 2nd International Symposium on Air Quality
Management at Urban, Regional and Global Scales, Istanbul, Turkey, September 2528, 2001.
6. Karman, D., Graham, L., Measurement and Modelling of Motor Vehicle Related
Air Toxics Along Urban Streets, TSRI Regional Conference – Urban Air,
Vancouver, November 2001.
7. Karman, D., Oguz, O., Akay, G., Graham, L., The Ottawa Microenvironment
Database for Motor Vehicle Related Air Pollutants, TSRI National Conference,
Ottawa, March 2002.
Measurement and Modelling of Motor Vehicle Related Air Toxics 36
8. Karman, D., Noseworthy, L., Graham, L., Measurement and Characterization of
PM2.5 in Urban Air, TSRI National Conference, Ottawa, March 2002.
9. Karman, D., Tuncel, G., Graham, L., Oguz, O., Spatial Variations in the
Concentrations of Motor Vehicle Related Organic Air Pollutants in Ottawa,
TSRI National Conference, Ottawa, March 2002.
10. Oguz, O., Tuncel, G., and Karman, Volatile Organics in an Urban Atmosphere,
Symposium 2002 EUROTRAC2, Transport and Chemical Transformation in the
Troposphere, Garmisch-Partenkirchen, Germany, 11-15 March, 2002.
The following four papers are planned for submission to Atmospheric Environment:
COMPARISON OF 2-HOUR AND 24-HOUR VOC MEASUREMENTS ALONG AN
URBAN STREET, Karman, D., Noseworthy, L., Graham, L., Oguz, O.
SEASONAL VARIATION OF PM2.5 CONCENTRATIONS AND
CHARACTERISTICS ALONG AN URBAN STREET, Karman, D., Noseworthy, L.,
Graham, L.
SOURCE APPORTIONMENT FOR MOTOR VEHICLE RELATED VOCs ALONG
AN URBAN STREET, Karman, D., Graham, L., Oguz, O.
SOURCE APPORTIONMENT FOR PM2.5 MEASUREMENTS ALONG AN URBAN
STREET, Karman, D., Noseworthy, L., Graham, L.
5. REFERENCES
1.
Lawryk, N.J., 1996. “Automobile commuter exposures to volatile organic
compounds: Emissions, malfunctions, and policy”, Transportation Research Part A:
Policy and Practice, Vol. 30, Iss. 1, pp. 55-56.
2.
Wallace, L.A., 1993. In “Chemistry and Analysis of Volatile Organic Compounds
in the Environment; Bloemen, H.J.TH.; Burn, J., Eds.; Blackie Academis and
Professional (Chapman&Hall): Galsgow, 1993; pp. 1-24.
3.
U.S. Environmental Protection Agency, 1993. “Motor Vehicle Related Air Toxics
Study”, Office of mobile sources, Office of Air and Radiation: Ann Arbor, MI, USA.
4.
U.S. Environmental Protection Agency, 1990. “Cancer Risk from Outdoor
Exposure to Air Toxics”, Vol. 1, Final Report, EPA, 450/1-90-004a. Office of Air
Quality Planning Standards, Research Triangle Park, NC, USA.
5.
Chan, C.C., Ozkaynak, H., Spengler, J.D., and Sheldon, L., 1991. “Driver
exposure to volatile organic compounds, CO, ozone, and NO2 under different driving
conditions”, Environmental Science and Technology, Vol. 25, pp.964-972.
Measurement and Modelling of Motor Vehicle Related Air Toxics 37
6.
Wan-Kuen, J., and Kun-Ho, P., 1999. “Commuter exposure to volatile organic
compounds under different driving conditions”, Atmospheric Environment, Vol. 33,
pp. 409-417.
7.
The Ottawa Micro-environment Database (OMDB)
www.carleton.ca/~dkarman/OMDB
8.
U.S. EPA 2001, CMB8 User's Manual, Office of Air Quality Planning and
Standards, Research Triangle Park.
9.
U.S. EPA 2000 & 2002, SPECIATE 3.1 and 3.2, EPA’s repository of Total
Organic Compound (TOC) and Particulate Matter (PM) speciated profiles for a
variety of sources for use in source apportionment studies. Available at:
http://www.epa.gov/ttn/chief/software/speciate/index.html
10.
CMB8 Applications and Validation Protocol for PM2.5 and VOCs, Desert
Research Institute, Reno, Nevada, September 1998.
11.
U.S. EPA, Enhanced Ozone Monitoring – PAMS, Photochemical Assessment
Monitoring Stations, http://www.epa.gov/oar/oaqps/pams/general.html
12.
Watson, J.G., Chow, J.C., Fujita, E.M., 2001, “Review of volatile organic
compound source apportionment by chemical mass balance”, Atmospheric
Environment, Vol.35, pp.1567-1584.
13.
Karman, D., Wong, K., O'Leary, K., Graham, L., 1997, “Source Apportionment
for VOCs in Micro-Environments using Chemical Mass Balance Receptor
Modelling”, Environmental Research Forum Vols.7-8, pp.158-163, Proceedings of
the 10th Regional IUAPPA Conference, Istanbul, 1997.
Measurement and Modelling of Motor Vehicle Related Air Toxics 38