Measurement and Modelling of Motor Vehicle Related Air Toxics
Along Urban Streets
Health Canada
Toxic Substances Research Initiative
Project #55, Final Report
May 2001
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 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 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 field work 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
transit bus. The in-vehicle concentrations are generally the highest among these
micro-environments
Measurement and Modelling of Motor Vehicle Related Air Toxics
2
-
-
-
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 which
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.
Source apportionment modelling based on the micro-environment and source emission
data collected during this study is ongoing. Source profiles generated and results
obtained will be disseminated through literature as well as the above named web site.
Measurement and Modelling of Motor Vehicle Related Air Toxics
3
CONTENTS
1. INTRODUCTION, 5
2. METHODOLOGY, 6
3. SUMMARY OF FINDINGS, 7
Gas phase samples at the roadside and in-vehicle micro-environments
Particulate matter samples at the roadside micro-environment
Vehicle Emissions sampling
4. DISSEMINATION OF RESULTS, 26
5. REFERENCES, 27
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, 17
9. Distribution of gas phase concentrations in commuter vehicles, summer, 18
10. Comparison of benzene concentrations with other studies, 22
11. Distribution of PM2.5 concentrations, winter and summer, 23
12. Comparison of PM measurements from 1994 and 2000, 24
13. Elemental and organic carbon in PM2.5 samples, 24
14. Metals in PM2.5 samples, 25
TABLES
1. Comparison of select compounds in different micro-environments, 20
2. In-vehicle concentrations of select compounds from other studies, 21
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.
Gas phase samples at the roadside and in-vehicle micro-environments
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 cold-start
mode effect 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
micro-environment. 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
7:30
11:30
3:30
24Hr
30
20
10
0
9
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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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
afternoon session. There are a number of days for which this comparison can be made,
Measurement and Modelling of Motor Vehicle Related Air Toxics
12
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
2
4
6
8
ERMD Rooftop conc. (ng/L)
6
4
2
0
0
2
4
6
ERMD Rooftop conc. (ng/L)
Measurement and Modelling of Motor Vehicle Related Air Toxics
8
13
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
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4
2
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nose.01Feb7.30
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Measurement and Modelling of Motor Vehicle Related Air Toxics
15
8
Measurement and Modelling of Motor Vehicle Related Air Toxics
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Figure 8 (concentrations in ng/L0
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
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17
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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
Measurement and Modelling of Motor Vehicle Related Air Toxics
In-Car (PM)
In-Bus (PM)
In-Car (AM)
In-Bus (AM)
30
20
10
0
18
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 micro-environment, 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 which offer
comparisons among all the micro-environments 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
19
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 concentrations in different microenvironments for different seasons
Winter mean concentrations, g/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 (g/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
Particulate matter samples at the roadside micro-environment
Figure 11 presents the minimum, 25th percentile, 75th percentile, and maximum PM2.5
mass concentration for winter-time 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
20
Table 2. Mean in-vehicle concentrations (g/m3) of VOCs and carbonyl compounds for comparable studies.
o-xylene
1,3-butadiene
formaldehyde
acetaldehyde
8.8  4.9
m&pxylene
30.5  17.2
11.4  6.2
3.3  2.4
NA
NA
181  158
24.8  18.9
71.8  75.7
53  41.9
NA
NA
NA
21.3  19.2
84.1  41.6
12.5  11.3
28.8  16.1
NA
NA
NA
20.10
40.60
14.10
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
ethylbenzene
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
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
21
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
r1
te
st
o
n,
w
in
am
,U
gh
rm
in
Bi
9
6
99
K,
1
er
um
m
,s
To
r
on
to
to
on
To
r
Bo
99
r1
te
,w
in
,N
gh
ei
22
19
94
4
8
98
C
,1
20
s,
s
O
tta
w
a,
in
-
bu
R
al
um
m
er
te
r
in
in
-b
us
,w
w
a,
tta
O
Measurement and Modelling of Motor Vehicle Related Air Toxics
00
20
00
00
20
er
um
m
in
-c
ar
,s
w
a,
tta
O
O
tta
w
a,
in
-
ca
r
,w
in
te
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 PM2.5
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
23
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
24
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
Zn
Fe
Mn
Sc
Ca
K
Cl
S
P
Si
Al
Mg
Na
0.0
Metal
Vehicle emissions sampling
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.
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.
Measurement and Modelling of Motor Vehicle Related Air Toxics
25
Mass emission rates of CO, CO2, NOX, THC, PM2.5 were determined. Samples were also
collected for determining mass emission rates of methane and non-methane
hydrocarbons, carbonyl compounds, particle phase organic and inorganic ions, SO2, NH3,
vapour phase organic acids and for detailed organic compound analysis.
The speciated emission data from these tests will assist the source apportionment studies
for ambient measurements on Slater street and in commuter vehicles.
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.
Three presentations have been made so far in conferences targeted for their specific
focus:
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.
The last paper, although focusing on the motorcycle emissions, includes data from one of
the transit buses collected with the same dilution tunnel facility and makes comparisons
between these two very different vehicles. Colin Welburn has defended an M.Eng. thesis
with the title of Characterization of Particulate Matter Emissions from Motor
Vehicles at the Department of Civil and Environmental Engineering at Carleton
University and is in the process of finalizing recommended revisions to his thesis.
The following four papers are planned for submission to Atmospheric Environment:
Measurement and Modelling of Motor Vehicle Related Air Toxics
26
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.
USEPA, US Environmental Protection Agency, 1993. “Motor Vehicle Related
Air Toxics Study”, Office of mobile sources, Office of Air and Radiation: Ann Arbor,
MI, USA.
4.
USEPA, US 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.
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.
Measurement and Modelling of Motor Vehicle Related Air Toxics
27
Measurement and Modelling of Motor Vehicle Related Air Toxics
28