Study of Coal Tar Sealant Application in Toronto

RECONNAISANCE STUDY OF COAL TAR SEALCOAT APPLICATION IN TORONTO AND AN ESTIMATE OF RELATED PAH EMISSIONS

DIAMOND ENVIRONMENTAL GROUP, UNIVERSITY OF TORONTO

August 2011

Diamond Environmental Group 2 | P a g e

RECONNAISANCE STUDY OF COAL TAR SEALCOAT APPLICATION IN TORONTO AND AN ESTIMATE OF RELATED PAH EMISSIONS

Prepared by

Diamond Environmental Group, Department of Geography and Department of Chemical Engineering 45 St George Street, Physical Geography Building University of Toronto M5S 3G3 Phone: (+1) 416-978-1749 http://faculty.geog.utoronto.ca/mdiamond/index.html

Project Leader

Prof. Miriam Diamond, PhD.

Project Team

Emma Goosey, PhD - postdoctoral researcher Susan Csiszar, MSc - PhD candidate (modelling applications) Stefanie Verkoeyon, MSc, research assistant Clayton Catching- research assistant

Prepared For Environment Canada, Ontario, Environmental Protection Operations Division


CONTENTS

EXECUTIVE SUMMARY 5

BACKGROUND 6

METHODS 7

SURFACE SAMPLING METHOD 7

SEALANT EMULSIONS 9

EXTRACTION METHOD 9

GC-MS ANALYSIS 10

QA/QC 10

RESULTS 11

CATEGORIZING CTS SAMPLES 11

COMMERCIAL SEALCOAT EMULSIONS 17

QUINOLINE 19

COAL TAR SEALANT ACROSS TORONTO 20

ESTIMATING WASH-OFF 23

CONCLUSION 25

REFERENCES 26

APPENDIX 28


Abbreviations <DL < Detection Limit Ace Acenaphthene Acy Acennaphthylene Antr Anthracene AS Asphalt sealcoat B[a]A Benz[a]anthracene B[a]P Benzo[a]pyrene B[b]F&B[j]F Benzo[b]fluoranthene & Benzo[j]fluoranthene B[ghi]P Benzo[ghi]perylene Chry Chrysene CTS Coal Tar Sealcoat DBA Dibenz[a,h]anthracene DCM Dichloromethane Fla Fluoranthene Flu Fluorene GC-MS Gas chromatography- mass spectrometry GTA Greater Toronto Area HMW High molecular weight Ip Indeno[1,2,3-cd]pyrene LMW Low molecular weight MSDS Material safety data sheet Naph Naphthalene NIST National Institute of Standards and Technology OS Other surfaces PAH Polyacyclic aromatic hydrocarbons Phe Phenanthrene Py Pyrene QA/QC Quality assurance /quality control Quin Quinoline RDS Recovery determination standard RSD Relative Standard Deviation SD Standard Deviation SRM Standard Reference Material UAS Uncoated asphalt USGS United States Geological Survey


Executive Summary

Coal tar sealcoats have been found to be a source of polycyclic aromatic hydrocarbons (PAH) to urban

surface water and sediments in several US cities (e.g., Van Metre et al. 2000, Mahler et al. 2005). The

goal of this study was to establish the frequency and spatial extent of paved surface coverage with coal tar

sealcoats (CTS) in the City of Toronto, and to estimate CTS as a source of PAH to storm water. This was

accomplished by (1) collecting surface samples from commercial parking lots and private driveways

across Toronto, (2) analyzing the PAH and quinoline concentrations of all samples, (3) estimating the

area of paved surfaces across Toronto using data from the field study combined with GIS land coverage

data, and (4) using the data collected to estimate PAH releases from CTS to Toronto.

Surface samples (n = 92) were taken across Toronto. All samples were analyzed for 16 PAH and

quinoline by GC-MS. Twenty-one samples or 23 % of total samples were identified as CTS based on total

PAH content and compound profiles, as well as isomer ratios. About 90 % of CTS use was in private

residential areas (n = 20) with about 10 % use in commercial parking lots (n = 1). ΣPAH concentrations

(n = 21 samples) of 54 – 24 000 mg kg-1 in samples containing CTS were an order of magnitude greater

than asphalt sealcoat but considerably lower than those reported by Mahler et al. (2005). Quinoline

concentrations varied from <detection limit (<DL) to 2400 mg kg-1, and were significantly higher

(p<0.05) in CTS than asphalt sealcoat and non-sealcoat surfaces. The area of driveways and parking lots

covered with CTS was approximated at 24 km2 of the Toronto area (630 km2) by means of analysis of

high resolution GIS imagery.

The estimated contribution of Σ17PAH from CTS entering Toronto’s storm water runoff ranged from 8 –

22000 kg y-1 with a median and mean of 96 and 1400 kg y-1, respectively. The wide range estimated

resulted from the wide range of PAH concentrations measured in CTS samples. To put this estimated

runoff contribution into perspective, the measured mean value of Σ18PAH discharged from Toronto’s

tributaries to Lake Ontario is 2200 kg y-1 (Helm et al. 2011).


Background

Several years ago Barbara Mahler and Peter Van Metre of the United States Geological Survey (USGS)

found that coal tar sealcoat (CTS) could be adding as much as 50 % of PAH in urban runoff and urban

surface waters and sediments (Mahler et al. 2005, Yang et al. 2010). They discovered this when studying

the dramatic rise in PAH concentrations in urban lake sediments, that they first correlated with the rise in

vehicle miles travelled (Van Metre et al. 2000). They found that CTS was mainly used to coat urban

residential driveways and small commercial and residential parking lots (EHS 2010). Additionally, they

found that CTS was the main sealcoat used in US cities east of the continental divide due to the

availability of coal tar residues from coking sources (Van Metre et al. 2009). Cities west of the divide

tended to use asphalt-based seal coats where the asphalt originates as an end-product from oil production.

Sealcoats are marketed to provide protection and aesthetic appeal to older asphalt and concrete driveways

and parking lots. The sealcoat emulsions are purported to prevent damage to the original material, reduce

surface erosion, and prevent surfaces from cracking which in turn would prevent water infiltration and

exposure to ultra-violet rays. The low cost and availability of CTS through major retail outlets has made

this product an easy choice for consumers. Manufacturers and companies that apply sealcoats recommend

resurfacing about every 5 years. Currently there are four main categories for sealcoats based on the

primary material: coal tar, asphalt emulsion, acrylic and asphalt cutbacks (Environment Canada, 2010).

The PAH content of these materials ranges between 2700 ppm in asphalt to a percentage of the solid

weight in CTS (>26 000 ppm).

CTS wears off through abrasion and wash off, where it could add significantly to PAH loadings in storm

water (Mahler et al. 2005, Van Metre et al. 2010a). Coal tar can add to runoff 65 times the PAH

concentration of uncoated driveway; asphalt based sealcoats can add 10 times the total PAHs (Minnesota

Pollution Control Agency, 2009). Abrasion also allows CTS to enter the indoor environment as it is

tracked in from coated surfaces (Mahler et al. 2010, Van Metre et al. 2010b SETAC presentation).

Recent work by Diamond, Helm and co-workers has yielded loading estimates of roughly 2200 kg y-1

(Figure 1) of total PAH (sum of 18 compounds) to nearshore Lake Ontario from Toronto tributaries

(Helm et al. 2011, Diamond et al. 2010). Tributaries were estimated to be the largest contribution to the

total of 3640 kg y-1 originating also from atmospheric deposition and waste water treatment plant

discharges. Sealcoat material would be a logical contributor to these tributary loadings.


The aim of this reconnaissance study was to identify the use of CTS in Toronto and to assess whether

CTS could be contributing significantly to PAH loadings from Toronto to the surrounding environment.

Figure 1: Summary of chemical loadings to near shore Lake Ontario (Diamond et al. 2010).

Methods

Surface Sampling Method Samples were collected from parking lots and driveways across Toronto at locations chosen according to

25 km2 grids. The locations were selected according to ease of access, as well as their position relative to

past PAH passive air sampling locations (Melymuk et al. in prep). The locality of the samples in relation

to Toronto and the model grids are displayed in Figure 2.

0

10

20

30

40

PBDEs PCBs

Wet Dep Dry Dep Gas Absorp Rivers WWTP

0

1000

2000

3000

4000

PAHs PCMs

Kg y-1


Figure 2: Sampling locations within Toronto (grey highlighted area); red dots are sampling

locations, blue dots are passive air sampling locations.

Pavement surface samples were collected in February and March 2011. Samples were obtained by

scraping an area of 0.25 m2 using a stainless steel blade (mounted in a holder) from driveways and

parking lots (Figure 3). The scrapings were transferred a glass jar, sealed and returned to the laboratory,

where they were placed in a -18°C freezer, until extraction (Figure 4).

Figure 3: Sample Collection. Figure 4: Example of collected scrapings.


Sealant Emulsions “Fresh” commercial sealant emulsions were also sampled for the presence of PAHs and quinoline. These

commercial samples were purchased from public stores. Unfortunately only two sealants were available

as purchasing was done during winter (these sealants are denoted as Emulsion 1 and Emulsion 2). The

sealants were analysed for PAH content in the fresh emulsion (~20 g) and then dried under vacuum

conditions in a desiccator at room temperature.

Extraction Method

Scrapings

Samples were weighed and extracted in dichloromethane (DCM) (15 mL) via shaking (10 sec), and

followed by ultra-sonication (20 min). The eluent was removed to a DCM cleaned (200 mL) bottle. This

process was repeated until the eluent remained clear (a sign of the removal of all binder present). The

samples were then stored at -18°C until analysis. The residual sample contents were allowed to air dry

and were re-weighed. This was done to establish the actual weight of the extracted binder, and to allow

for later comparison of binder vs. total sample concentration and the presence of PAH.

The extract was applied to preconditioned columns containing alumina (8 g), anhydrous silica gel (4 g),

and sodium sulphate (1 g). An aliquot (1 mL) of the extract was eluted with DCM (30 mL) into a round

bottom flask. Samples were then solvent exchanged into hexane via rotary evaporator, reduced under a

stream of nitrogen (99.99 %) to near dryness and re-eluted with nonane (200 µL). At this time 5 µL of the

recovery determination standard (RDS) was added.

Emulsions

Samples taken from the raw commercial emulsion were analysed for the content of PAHs in the wet

emulsion and after it had been allowed to dry. The wet emulsion (~1.5 g) was dissolved in acetone (140

mL), after which an aliquot (1 mL) was removed and diluted with DCM (9 mL). An aliquot (1 mL) of the

DCM:acetone solution was taken and applied to conditioning columns, continuing with the same method

as the scraped samples. Dried emulsion (~0.2 g) was extracted using the same method as for the

scrapings; DCM extracted until eluent remained clear. The pre (wet emulsion) and post (dried material)

weight measurements were acquired and indicated that emulsion contained ~53 % solid materials, whilst

the second emulsion contained ~50 % solid materials.


GC-MS Analysis Sample analysis was conducted on a 158 Agilent 6890N gas chromatograph coupled to an Agilent 5975

Inert Mass Selective Detector, using a 60 m HP-5 MS column for the detection of the PAH and quinoline

compounds (the method is described in the Appendix).

Quality Assurance/Quality Control Three procedures were used to continuously monitor for quality assurance and quality control (QA/QC)

throughout the analysis: (1) monitoring of recoveries via deuterated internal standards (recoveries were

56-120 %), (2) monitoring attribution of the source of analyte via laboratory and field blanks (blanks

contributed < 5 %), and (3) monitoring precision by analysis of a coal tar standard reference material

(SRM) (NIST SRM 1597A) (reproducibility test results are reported in Table 1). The SRM is a complex

mixture of PAH from coal tar that was isolated from coal tar and dissolved in toluene (NIST 2006). The

recovery of the SRM throughout the analysis did not deviate more than 20 % from the certified values

(certified values are available from the National Institute of Standards and Technology (NIST)). Recovery

determination standard (RDS), para-terphenyl, was measured within the QA/QC protocol of 70 – 100 %.

Table 1: NIST SRM 1597a reproducibility results (mg kg-1), *standard deviation (SD), + relative standard deviation (RSD).

Sample 1 2 3 4 5 Mean Certified Results

SD RSD (%)

Naph 1041 1024 1023 1017 1034 1028 1030 9.6 0.9

Acy 270 254 260 233 261 256 263 14 5

Ace 8.9 6.6 7.1 7.5 7.1 7.4 7.63 0.9 12

Flu 111 141 124 132 148 131 145 14 11

Phe 468 410 430 447 449 441 454 22 5

Ant 101 107 103 110 102 105 107 4 4

Fla 312 321 310 331 324 320 327 9 3

Py 213 230 2335 246 243 233 240 13 6

B[a]A 99 91 95 94 90 94 98.1 4 4

Chry 62 69 58 62 55 61 66.2 5 9

B[b]F&B[j]F 89 92 102 109 104 99 107.3 8 8

B[k]F 46 42 30 37 33 38 41.2 7 17

B[a]P 95 82 92 90 89 89 93.5 5 5

Ip 46 44 51 37 43 44 50.5 5 11

B[ghi]P 59 46 44 43 41 47 55.5 7 15

DBA 6.2 6.0 6.7 6.3 5.7 6.1 6.93 0.4 6


Results Concentrations of total PAH and individual compounds varied over six orders of magnitude (ΣPAH 0.02

– 24 000 mg kg-1, Table 2). The most abundant compounds according to mean values were

benzo[b]fluroanthene and benzo[j]fluroanthene, pyrene, benzo[a]pyrene, chrysene and

benz[k]fluoranthene. In contrast, the most abundant PAH in urban air (gas and particle phases) are

phenanthrene and fluorine in the gas phase, and fluoranthene, pyrene and benzo[b]fluroanthene and

benzo[j]fluroanthene in the particulate phase, (Melymuk et al. in prep). Observations made during

sampling suggested that the variability in surface samples was primarily due to differencing in surfacing

materials, as well as the age of material, intensity of area use, wear rate, etc.

Table 2: Summarized PAH compound concentrations (mg kg-1) from 92 sampling locations in Toronto, *standard deviation (SD), + relative standard deviation (RSD).

PAH Minimum 5th Percentile

Median Mean 95th Percentile

Maximum SD RSD (%)

Naphthalene N.D. 0.0003 0.029 0.13 0.55 2.4 0.33 250 Quinoline 0.0002 0.0035 0.063 0.13 0.41 1.7 0.21 170 Acenaphthylene N.D. 0.0002 0.006 0.70 3.6 28 3.1 450 Acenaphthene N.D. 0.0005 0.006 2.4 12 78 11 450 Fluorene N.D. 0.0007 0.011 2.4 8.7 101 11 470 Phenanthrene 0.0007 0.006 0.059 26 190 630 83 310 Anthracene 0.0035 0.0081 0.14 30 170 1300 150 490 Fluoranthene 0.0028 0.015 0.16 87 440 2300 300 340 Pyrene 0.0047 0.023 0.65 710 1400 35 000 4000 570 Benz[a]anthracene 0.0013 0.005 0.24 270 720 11 000 1400 540 Chrysene 0.0026 0.007 0.38 430 880 20 000 2400 560 Benzo[b]fluroanthene & benzo[j]fluroanthene

0.0022 0.01 0.72 790 4100 29 000 3700 470

Benz[k]-fluoranthene 0.0027 0.013 0.41 410 1200 13 000 2000 500 Benzo[a]pyrene 0.0024 0.01 0.35 570 760 21 000 2800 490 Indeno(1,2,3-cd)pyrene N.D. 0.0053 0.33 83 260 2700 370 450 Benzo[ghi]perylene N.D. 0.0042 0.25 200 320 8000 1000 510 Dibenz[a,h]anthracene N.D. 0.0017 0.047 5.9 4.7 190 29 490

Categorizing CTS samples

Each sample from the 92 taken from driveways and parking lots was placed into one of four categories of

surface types CTS, asphalt sealcoat (AS), uncoated asphalt (UAS), and other impervious surfaces (OS).

This assignment was based on three criteria: (1) the PAH concentration of samples, (2) PAH compound

profiles, and (3) isomer ratios calculated for various molecular weight compounds (Mahler et al. 2005,

Austin Report 2005, Ahrens and Depree 2010). The result of the categorization processes was the

assignment of 21 of 92 samples as CTS, 35 samples were AS, 28 were UAS samples, and 8 samples were


other materials. This translated into CTS coverage of ~23 % of parking lots and drive ways sampled, and

38, 30, and 9 % coverage of AS, UAS and “other”.

Sample Concentrations

Total PAH concentrations in those samples identified as CTS had PAH concentrations up to three orders

of magnitude higher than other samples (Table 3). Such high concentrations are indicative of coal tar as

no other materials have been noted to be so enriched in PAH (Ahrens and Depree 2010). The PAH

content of other source materials such as rubber tire particles, diesel, and used engine oil are in the range

of 10 - 2000 mg kg-1 (Takada et al. 1991, Wang et al. 1999, Intron 2007). Several samples categorized as

CTS had PAH concentrations that overlap with this lower range, and hence identification of those

samples as CTS was based on the two other criteria listed. For example, one ambiguous sample had a

low total PAH concentration but high concentrations of benz[a]anthracene and chrysene. In this case, the

categorization of CTS was aided by the analysis of isomer ratios 228 and 278 as discussed below.

Samples in the other three categories had much lower PAH concentrations and inconsistent presence of

all compounds.

Table 3: Sample categorisation

Material

(Scraping)

This Study Mahler et al.

(2005)

CTS 53 - 24,000 9,500 – 83,000 AS 1 – 14 340 – 2000 UAS 0.1 – 0.9 7.1 - 20 Other 0.02 – 0.15

It is interesting to note that the PAH content reported in this study were considerably lower and span a

broader range in comparison to those listed by Mahler et al. (2005), the reason for which is unclear.

Precipitation rates of ~850 mm are similar in Toronto and Austin Texas where Mahler and co-workers

sampled. Austin has a humid subtropical climate with an annual mean temperature of 20.3oC which

suggests greater likelihood of losses of PAH due to volatilization. In comparison, Toronto has a humid

continental climate with an annual mean temperature of 7.8oC which offers less opportunity for PAH

volatilization. However, Toronto winter conditions of freeze-thaw cycles and especially prolonged

periods when pavement is partially thawed, lead to pavement wear which could explain greater losses of

PAH from all categories of surface types in Toronto versus Austin. Watts et al. (2010) commented that


wind abrasion and removal when snow ploughing were other mechanisms leading to the wear of CTS.

Mahler et al. (2005) suggested that abrasion by vehicle travel alone was a key factor in increasing the

removal of CTS from “used” versus test plots of CTS in Austin. In Toronto we suggest that the freeze-

thaw cycles plus extra abrasion caused by snow ploughing etc., accelerate CTS loss beyond that from

vehicle abrasion. If the commercial CTS products that are applied in Toronto have similar PAH

concentrations as those measured by Mahler et al. but pavement wear and abrasion is greater, then the

corollary is greater PAH removal from Toronto than Austin surfaces.

Sample Profiles

CTS samples had a distinct profile with significantly higher (t= 2.01 – 2.47, p< 0.05) concentrations of

the low molecular weight compounds (LMW), as well as phenanthrene, benz[a]anthracene and chrysene,

as illustrated in Figures 5 and 6. Concentrations of the lowest molecular weight compounds naphthalene

and quinoline varied ~10-fold amongst the four categories of surface covers. In contrast, concentrations of

phenanthrene, benz[a]anthracene and chrysene varied ~five orders of magnitude.

Figure 5: PAH profiles for median concentrations of the 4 sample subcategories


Figure 6: PAH concentrations (mg kg-1) of 21 surface samples identified as CTS (21 lines represent concentration profiles of individual samples).

Isomer Ratios

Isomer ratios have been used as a diagnostic tool in CTS studies by Mahler et al. (2005), Van Metre et al.

(2009) and Ahrens and Depree (2010). The isomer pairs used for diagnosis have been benz[a]anthracene

and chrysene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene, benzo[a]pyrene and benzo[e]pyrene,

fluoranthene and phenanthrene. The latter was not possible in this study as we did not quantify

benzo[e]pyrene.

Ahrens and Depree (2010) found that samples of pavement sampled in Auckland New Zealand fell along

a straight line in a plot of isomer ratios of benz[a]athracene:(benz[a]athracene + chrysene) vs.

indeno[1,2,3-cd]pyrene:(indeno[1,2,3-cd]pyrene + benzo[ghi]perylene). The end members along this line

were coal tar (pyrogenic hydrocarbons) in the upper right quadrant of the graph, and in the lower left,

were asphalt and bitumen which have a petrogenic source. As seen in Figure 7, samples from this study


also were spread between these two end members, but with considerably more scatter than that found by

Ahrens and Depree.

The second isomer ratio investigated was the sum of concentrations of isomer pairs of (benz[a]anthracene

+ chrysene) concentrations versus (fluoranthene + phenanthrene) concentrations (Figure 8). Samples with

elevated concentrations of fluoranthene and phenanthrene (within the circled) were identified as CTS.

These samples also displayed ΣPAH concentrations on orders of magnitude higher than other samples.

The third and final isomer ratio explored was that of the (benz[a]anthracene + chrysene) concentrations vs

the respective isomer ratio of benz[a]anthracene:chrysene. All categories were separated by their

concentrations of benz[a]anthracene + chrysene with CTS samples having the highest values (Figure 9).

Figure 7: Ratio profiles of benz[a]athracene: (benz[a]athracene + chrysene) vs. indeno[1,2,3-cd]pyrene: (indeno[1,2,3-cd]pyrene + benzo[ghi]perylene).


Figure 8: Sum of (benz[a]anthracene + chrysene) concentrations vs. sum of (fluoranthene + phenanthrene) concentrations. Circled area indicates samples with profiles indicative of CTS.

Figure 9: Sum of (benz[a]anthracene + chrysene) concentrations vs the respective isomer ratio of benz[a]anthracene:chrysene.


Commercial Sealcoat Emulsions

Concentrations of total PAH in the wet samples of commercial seal coat ranged from 90 000 to 120 000

mg kg-1 (see Table 4). The range of total PAH in the dried commercial samples fell to ~32 000 mg kg-1, a

loss of ~70 % of the PAH mass during the 48-hour drying process. Concentrations of the emulsions were

two and one orders of magnitude higher for the wet and dry samples, respectively, than the CTS samples

collected across Toronto.

Table 4 Commercial sealcoat PAH concentrations (mg kg-1)

PAH Emulsion 1 Wet

Emulsion 2 Wet

Emulsion 1 Dry

Emulsion 2 Dry

Napthalene 6500 4800 1900 1000 Quinoline 1400 800 200 90 Acenaphthylene 4800 1900 1200 1200 Acenaphthene 6700 1800 1700 1200 Fluorene 5800 3500 1600 1900 Phenanthrene 22 800 15 300 6400 7000 Anthracene 12 400 21 500 3400 5000 Fluoranthene 22 600 15 900 9100 900 Pyrene 19 000 10 200 5000 5200 Benz[a]anthracene 2000 600 1500 700 Chrysene 1000 300 700 300 Benzo[b]fluroanthene & benzo[j]fluroanthene

1900 400 2200 500

Benz[k]fluoranthene 3200 1700 2800 1100 Benzo[a]pyrene 4300 1100 2800 1100 Indeno(1,2,3-cd)pyrene 2900 700 1700 800 Benzo[ghi]perylene 2900 700 1500 600 Dibenz[a,h]anthracene 400 90 300 90 ΣPAH 120 000 89 000 36 000 28 000

The profiles of compounds varied between the two commercial mixtures, the wet and dried mixtures and

the weathered CTS samples Toronto (Figure 10). The wet commercial emulsions had the highest

concentrations of phenanthrene, anthracene, fluoranthene as well as pyrene. The dried commercial

emulsions were also high in phenanthrene, fluoranthene and pyrene, but not anthracene. In contrast, the

CTS samples collected across Toronto had the highest concentrations of the higher molecular weight, less

volatile compounds benzo[b]fluroanthene, benzo[j]fluroanthene, pyrene, benzo[a]pyrene, chrysene and

benz[k]fluoranthene. Thus, mostly the lower molecular weight PAHs were lost quickly as the wet

commercial mixture dried. Then subsequent weathering by wash-off results in the loss of a fraction of all

PAH compounds in CTS regardless of molecular weight (in contrast to volatilization losses that depend

on molecular weight).


Figure 10: Emulsion 1 and 2 commercial sealcoats PAH concentrations from the original solution and the resultant dried material, (mg kg-1).


Quinoline

Quinoline concentrations in wet sealcoat were in the order of 1000 mg kg-1 or 0.1 % w/w. Environment

Canada (2010) reported concentrations of quinoline of <0.01 % (w/w) in wet sealcoat. This concentration

decreased to, on average, 170 mg kg-1 in the dried commercial emulsions, 51 mg kg-1 in CTS samples,

and 50, 34 and 11 in asphalt sealcoat, uncoated asphalt and ‘other’(Figure 11). The volatility of quinoline

allowed for an 80-90 % loss of mass during the 48-hour drying process of the commercial sealcoat

samples and a further 30 % loss relative to CTS samples.

Figure 11: A, commercial sealcoat quinoline concentrations, and B, mean quinoline sample concentrations in coal tar sealcoats (CTS), asphalt sealcoats (AS), uncoated asphalt (UAS), and other samples (other) (mg kg-1).


Coal Tar Sealant Coverage across Toronto

Results of the sampling campaign and subsequent chemical analysis suggested that ~23 % of parking lots

and driveways sampled were covered by CTS. As can been seen in Figure 12, the CTS sites are located

mainly in the suburbs Etobicoke and Scarborough and less so in the centre of Toronto and North York.

The absence of CTS from the inner city is not surprising since there are fewer driveways and parking lots

than in the suburbs. Even so, anecdotal evidence suggests that driveway sealants tend to be more popular

outside of the central part of the city.

Figure 12: Map of the City of Toronto indicating all sampling locations and those identified as CTS.


Figure 13 Flow chart summarizing method followed to estimate land use cover and CTS coverage in Toronto.

We next extrapolated this percentage coverage of CTS to Toronto in order to arrive at the total area that

could be coated in CTS. The extrapolation procedure is illustrated in Figure 13. First, land cover across

for the City of Toronto (as of 2007) was estimated using high resolution GIS available from

www.toronto.ca/open (Figures 14 and 15). The high resolution data were discriminated into eight land

coverage categories of which we selected the land coverage category “parking lots and driveways” which

excluded roadways and buildings. Of a total area of 630 km2 in Toronto, the land coverage category

“parking lots and driveways” covered 112 km2 or 18 % of Toronto (Figure 15).

The data set was then further manipulated to eliminate small areas of imperviously covered land such as

side walks, which were less than the required space for an average vehicle parking space (15 m2). This

reduced total area most likely to be parking lots and driveways to 106 km2.

The final stage of the analysis was to estimate the area likely to have CTS. We did this by multiplying the

frequency of CTS occurrence of 23 % (21 out of 92 samples identified as CTS) by the area of parking lots

and driveways of 106 km2 to yield a value of 24 km2 or 4 % of the total Toronto area. This extrapolated

area of 24 km2 is not location-specific, but rather is an estimate of the aggregate area within Toronto

likely to be coated with CTS.


Figure 14: High resolution GIS land cover dataset for the City of Toronto, with 8 different classes, representing 630 km2 (www.toronto.ca/open, City of Toronto 2007).

Figure 15: GIS map of the City of Toronto showing “other paved surface” in red. Inset is a magnified version of a 1 km by 0.7 km grid.


Estimating Wash-Off

Finally, CTS-derived PAH mobilized via storm water wash-off was estimated from the data reported

herein. Mahler and co-workers (e.g., Mahler et al. 2005, Van Metre et al. 2009, 2010) and Watts et al.

(2010) found that wash-off is a major removal mechanism of CTS. Because of high wash-off rates, CTS

requires re-application every 3 to 5 years following application.

Several studies have reported that particle and chemical wash-off follows a so-called first flush effect

where most wash-off occurs during the initial rain event (Vaze and Chiew 2003, Egodawatta et al. 2009).

Using this information, Csiszar et al. inter alia (Submitted 2011) reported that ~60 % of atmospherically

derived surface films that coat all impervious surfaces are washed-off during a given rain event. In the

absence of a specific wash-off rate for CTS, we used this information to estimate the amount of PAH that

is washed-off CTS surfaces in the City of Toronto.

The mass of PAH washed-off a surface into storm water, MSW (g) can be calculated using equation 1

where R is the run-off ratio (defined as volume fraction of rain water that is converted to storm water),

WE is the wash-off efficiency (60 % as described above), and mPAH is the mass of PAH associated with

the surface dust. The run-off ratio can be related to the fraction impervious area surface and was assumed

to be 60 % for Toronto (Csiszar et al. submitted). The remaining 40 % of run-off was assumed to remain

as surface storage on impervious surfaces, infiltrate the impervious surface through cracks, or be

transferred to soil.

The mass of PAH associated with the surface dust can be calculated using equation 2 where CPAH (g m-2)

is the measured PAH concentration, and AS (m2) is the estimated CTS surface area in Toronto (24×106

m2) as described above. We applied the above formulation using the median of measured PAH

concentrations in CTS samples.

PAHEsw mRWm = (1)

SPAHPAH ACm = (2)

Using this simple calculation, we estimated that a median of ~2 kg (range of 0.2 to 500 kg) of Σ17PAH

would be washed-off from CTS-coated surfaces during one rain event. Another 1.5 kg of Σ17PAH would

be subject to surface storage, infiltration or transfer to soil, as mentioned above, although this division

between runoff and “other” is highly uncertain. Table 5 lists the medians, means, and ranges of transfer to


storm water from eight selected compounds resulting from one rain event. Pyrene accounted for the

largest contribution (30 %) to the median wash-off loadings out of the 17 congeners and quinoline

accounted for the smallest percentage (0.01 %).

Table 5: Estimated CTS wash-off per rain event for 8 PAH compounds per event and per year for Σ17PAH.

PAH Median (kg) Mean (kg) Range (kg) Quin 3×10-4 6×10-4 2×10-5 - 0.006 Flu 0.008 0.01 1×10-4 - 0.04 Phe 0.1 0.3 0.001 - 2 Py 0.7 3 0.1 - 15

B[a]A 0.08 1 0.02 - 7 Chry 0.2 1 0.03 - 9

Ip 0.07 1 5×10-5 - 24 B[ghi]P 0.07 3 0.002 - 44

Σ17PAH per event 2 33 0.2 - 500 Σ17PAH per year 96 1400 8 - 22000

In order to estimate yearly transfers, we assumed that this calculated amount would be transferred during

each rain event and multiplied by the number of rain events over 5mm per year. With 44 rain events

exceeding 5 mm in one year (Environment Canada, 2002), we estimated a median transfer of ~96 kg yr-1.

We also calculated a high and low estimate of PAH removed by wash-off using the high and low

measured CTS concentrations. The results span a very wide range of 8 to 22 000 kg yr-1 (Table 5)

transferred to storm water. The modeled range is so broad due to the large range in measured

concentrations; these calculations do not account for uncertainty in the coefficients used to parameterize

the wash-off process. Uncertainty in the wash-off efficiency WE would likely be subsumed within this

wide range of estimated values.

These estimates of 8 to 22 000 kg yr-1 compare to 2200 kg yr-1 of Σ17 PAH tributary loadings to Lake

Ontario from Toronto (Diamond et al. 2010). Over the 24 km2 area coated in CTS, the wash-off rates

equate to 0.04, 0.6, 0.003 and 9.2 kg yr-1 ha-1 (median, mean, low and high values, respectively). In

comparison, Watts et al. (2010) reported wash-off rates of Σ16 PAH measured from two parking lots

freshly coated with CTS of 9.8-10.8 kg ha-1 over a 2 year period. Whereas the range reported by Watts et

al. was determined from two freshly coated parking lots, our lower rates come from samples that were all

aged a minimum of several months to years. Thus, our calculated wash-off rates appear to be reasonable.


A next step would be measuring actual wash-off rates to better quantify the contribution of CTS to PAH

loadings in Toronto’s storm water.

Conclusion From the 92 samples of surface pavement collected from driveways and parking lots throughout Toronto,

21 were identified to be derived from CTS. This frequency represents approximately 23 % of the area of

land coverage classified as parking lots and driveways using high resolution GIS imagery of the City of

Toronto. These values translated into 24 km2 or 4 % estimated to be coated in CTS relative to the total

land area of 630 km2 of Toronto.

The concentration of total PAH in samples containing CTS ranged from 54 to 24 000 mg kg-1, which was

an order of magnitude higher than that in other surface samples, but lower than the range reported by

Mahler and co-workers in the U.S. PAH were also measured, but at lower concentrations, in the three

other categories of surface types – asphalt sealcoat (AS), uncoated asphalt (UAS) and other materials

(Other) which comprised 38, 30 and 9 % of all samples.

CTS samples were enriched in low molecular weight PAH as well as phenanthrene, benz[a]anthracene,

and chrysene. Concentrations of quinoline in CTS varied from 0.0014 to 0.29 mg kg-1, and were only

marginally elevated relative to its concentration in other surface samples. The low content of quinoline is

presumed to be partly present due to its low concentration in coal tar (natural product), as well as its

volatility and the loss of the compound during the drying of the material (recorded >80 % loss from the

tested commercial emulsions).

PAH wash-off from CTS was estimated to contribute 96 and 1400, 8 and 22 000 kg y-1 to storm water

(calculated from median, mean, low and high Σ17PAH concentrations measured in this study). The very

wide range was due to the wide range in concentrations measured in CTS samples. These values compare

with 2200 kg y-1 Σ17PAH that are discharged from Toronto’s streams (extrapolated from measured

concentrations). We suggest that CTS is worn off at greater rates in Toronto than in warmer climates due

to freeze-thaw cycles and abrasion by snow plowing (in addition to vehicle wear), which could explain

why we find relatively low concentrations of PAH in surface samples identified as CTS in Toronto

relative to Austin Texas. Further, we suggest that contributions of CTS to total PAH in storm water are

likely due to the low spatial frequency of 4 % CTS coverage of the total Toronto land area.


References

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Appendix

GC-MS Method and Parameters

Column DB-5MS, J&W Injector Pulsed splitless Sample Volume 1 µL Solvent A and B isooctane Syringe wash 3 times both solvents Purge 1 minute Pulse Pressure 35 psi at 1.05 minutes Inlet Temperature 280°C GC Oven Temperature 0 min – 100°C

3 min – 100°C 44 min – 320°C 54 min - 320°C

Column Mode Constant Carrier Gas Helium

1.2 mL min-1 Interface Temperature 300°C MS Ion source EI

70 eV MS Mode SIM

m/z = 66, 82, 128, 136, 149, 152, 153, 162, 164, 166, 178, 188, 191, 202, 212, 217, 218, 228, 240, 252, 264, 276, 278, 418

Dwell 10 EM Absolute value


Sample PAH Concentrations (ng g-1)

Site Napth Quin Acy Ace Flu Phe Antr Fla Py B[a]A Chry

B[b]F&B[j]F B[k]F B[a]P Ip B[ghi]P DBA

1 193 176 4 33 9 43 12 320 330 9 15 20 17 19 85 175 8

1.D 547 313 3473 6279 11114 191922 17385 1118531 921568 34441 60059 58195 23899 33176 58427 28955 1988

2 21 26 8 3 10 45 499 189 2755 1607 1810 2763 1699 2504 841 567 53

2.D 119 175 2 3 8 163 30 809 674 16 34 24 18 16 32 40 4

3 963 454 10 8 52 355 174 4187 2906 48 93 35 15 16 26 34 11

3.D 311 75 9 4 36 415 19 2508 2129 87 143 91 48 71 114 97 4

4 3 29 7 12 7 20 1573 39 744 237 865 482 493 862 324 481 428

4.D 272 101 1000 1296 4473 16559 955 149497 45866 9636 51942 188857 72484 37382 13065 23258 257

5 42 334 8 27 14 142 9362 674 9252 2115 1966 943 3601 2484 2152 1948 1770

5.D 26 23 5 2 6 118 14 136 89 37 28 73 56 51 29 26 8

6 200 280 15 6 22 374 242 774 507 128 111 288 183 220 110 112 18

6.D 39 80 2 3 3 34 4 34 29 8 5 114 103 13 22 26 23

7 77 116 2 2 15 325 57 929 722 177 121 266 267 280 251 169 4

7.D 710 79 2462 4237 9021 164621 27847 177938 122312 37762 27232 60740 18684 69504 30366 27185 634

10 8 1744 8 17 16 43 2908 704 10797 5925 8031 9122 10465 8898 5192 3013 1170

10.D 74 41 8 6 21 413 225 250 111 65 27 55 102 28 42 24 2

12 14 8 832 1822 3188 18374 31639 140876 2139782 998852 1199653 4248731 350817 1555831 152608 457228 6301

12.D 1618 249 795 78236 101872 199712 198552 2277187 35040304 11365514 20092711 28996618 12937014 21381627 2635562 8042352 58729

13 51 63 3 9 5 65 95 132 65 36 22 65 58 20 76 28 3

13.D 45 25 2 5 5 70 91 156 73 33 25 70 196 21 4 27 2

14 134 86 5 12 11 114 159 112 52 21 9 11 32 5 9 28 6

14.D 92 32 6 13 12 101 138 34 19 4 3 6 20 2 7 10 3

15 10 44 6 6 5 82 553 281 4346 3084 2769 4736 2739 3428 2048 1222 300

16 45 65 3 3 4 14 16 15 17 3 3 2 5 10 189 560 2

16.D 33 106 2 4 2 18 18 78 75 14 24 17 97 29 22 22 3

17 3 31 0 3 0 9 32 38 688 649 590 3277 733 783 550 298 139

17.D 40 380 6 31 0 80 6593 147 2740 3018 2642 6612 3113 2941 5442 5098 2432




18 7 11 0 2 2 7 411 19 415 246 183 530 177 212 2049 364 128

18.D 1 5 14 12 3 36 405 164 2545 2113 1172 5256 2239 2144 1598 539 124

19 96 239 0 37 14 50 23 115 107 297 62 65 81 129 0 0 8

19.D 149 120 6 7 11 41 26 40 35 2 7 6 11 16 7 8 4

23 0 3 2 1 16 1 19 4 95 48 23 2925 36039 894 3902 502 21

25 1 23 2 14 4 19 1379 37 602 209 379 380 282 243 227 151 155

25.D 0 1 6 1 1 7 32 30 460 262 259 1214 2584 326 1152 115 49

26 0 0 1 3 3 12 53 42 618 293 339 858 377 350 337 145 27

26.D 2 9 6 14 19 62 208 197 2679 690 1672 1741 4956 1653 1048 919 62

27 39 52 8 3 10 60 12 112 94 16 21 44 46 12 50 21 2

27.D 69 108 6036 11321 6995 31878 23522 129631 113201 14409 16043 12644 15938 10177 9651 11877 761

28 0 0 0 1 1 9 15 45 679 230 445 1162 376 423 407 207 52

28.D 6 57 1 1 1 10 29 44 609 98 466 1539 129 434 443 418 23

29 239 417 20 14 11 132 30 428 384 54 71 75 188 40 96 0 0

29.D 320 101 643 1227 1083 31398 2815 92263 85637 8894 17488 29161 8043 10837 14794 13058 809

30 13 54 1 4 8 21 207 27 580 4267 2291 2202 658 784 898 754 74

30.D 204 471 1025 1908 1991 50755 11032 172978 148089 20809 28210 51522 34053 19222 42683 20906 1003

31 13 51 55 16 36 213 236 356 483 45 79 109 118 92 40 39 20

31.D 137 218 1422 3890 7189 101852 148314 314033 451311 38454 70966 53444 156396 112537 8233 30565 589

32 1 188 2 3 16 134 406 490 7263 3381 3829 7032 5795 4330 2629 1715 562

32.D 12 56 76 204 493 14270 2122 43554 67471 9714 12201 17842 12569 16665 6907 5961 245

33 5 268 24 16 15 29 125 68 1411 374 526 1635 436 64 469 361 139

33.D 3 120 1 2 4 23 139 93 1645 671 1201 2610 837 1047 759 631 65

34 6 19 3 1 7 29 8 40 60 15 29 109 43 25 33 18 24

34.D 3 23 1 1 2 17 4 42 60 7 13 18 10 14 7 7 4

36 8 149 4 4 5 28 260 112 1990 864 956 2592 1311 1229 995 833 150

36.D 12 12 0 0 1 5 3 14 5 1 4 4 4 3 2 3 1

37 18 96 2 4 1 23 10 62 60 12 25 49 55 21 20 12 14

37.D 14 90 1 4 1 20 8 57 56 9 11 16 23 13 6 7 3

38 21 64 2 4 1 27 12 55 54 9 10 16 28 11 6 5 3




38.D 32 55 33 153 29 6120 1066 23656 21868 3571 4247 5536 2359 6038 1867 1925 145

39 22 403 1581 990 2398 91802 209346 57563 958299 492658 612684 12230777 5545207 8249799 1589093 2926222 178953

39.D 36 345 35 56 137 1069 6425 6386 100069 44135 59396 236347 88382 70097 40990 28131 3429

40 57 177 11 29 82 228 2049 573 8878 2034 895 3423 5631 4989 3971 3788 535

40.D 15 38 216 705 1799 23871 211289 98471 1928179 1058772 1248989 4012094 2298984 1540 701549 203025 289

41 24 96 27 5 4 39 43 104 95 19 19 22 22 10 6 3 26

41.D 2414 298 28293 63924 8400 236895 48648 734726 299357 69867 122295 92886 31218 86662 50361 45899 868

42 0 6 0 0 0 1 5 3 50 15 24 59 37 22 19 17 5

42.D 0 5 21 13 31 1192 2715 7476 124454 63982 79569 158869 72023 107140 20638 38003 2324

43 0 2 0 0 1 8 40 45 705 312 419 1708 634 494 289 198 24

43.D 10 19 2 2 1 39 33 250 103 23 44 37 29 30 20 18 15

44 2 6 0 1 3 7 47 17 268 63 27 23 205 152 84 115 16

44.D 8 14 2 1 4 21 249 130 2065 1158 1720 2839 2217 1598 1160 613 45

45 1 12 0 1 2 5 33 14 236 111 152 207 109 151 64 62 66

45.D 545 627 18 21 39 163 52 622 328 233 382 270 105 184 160 185 154

46 0 6 5 12 3 9 43 53 824 485 604 1111 1590 651 561 296 36

46.D 299 309 4704 13701 24198 164104 473062 424047 6440374 2904089 4372524 5505147 2410355 7707677 392185 1633585 89452

47 1 4 0 0 1 4 25 14 217 99 131 211 94 144 81 74 5

47.D 468 165 6129 15384 2728 189534 14705 466208 227695 56490 93031 78692 45188 70155 47017 37384 622

48 2 8 0 1 2 7 45 16 252 102 150 406 103 158 196 78 9

48.D 37 353 3767 12791 23393 213372 1301834 1016557 16067166 7033414 10898853 16663792 13436510 12980948 1798604 4427164 186359

49 1 12 0 1 1 7 22 29 442 199 294 528 494 307 247 138 12

49.D 79 47 6 14 4 646 111 4322 1732 630 822 587 1599 661 507 388 245

50 58 63 1 1 4 22 40 88 26 6 26 16 14 14 12 20 4

50.D 60 84 14 57 36 535 165 2532 633 276 1096 1306 1985 340 360 336 147

51 5 41 1 19 32 179 820 559 7987 3388 4318 8047 3737 5005 3202 1630 57

51.D 79 65 3 1 13 54 86 141 40 9 38 30 31 22 12 15 2

52 1 26 1 1 4 24 1006 163 2421 1071 1493 3719 2935 1721 1421 606 23

52.D 58 32 7 5 12 58 62 245 67 49 98 88 78 36 156 95 57

53 39 31 1 0 4 8 15 17 6 2 7 9 3 4 2 6 1




53.D 305 115 452 543 2435 51836 12743 236612 73144 25671 107853 104501 20492 33019 1354 7840 144

54 288 121 6 3 39 726 1496 491 122 109 256 151 30 364 30 18 6

54.D 41 55 714 763 4310 628321 11019 255923 73000 59835 96433 5451 1644 938 14 489 211

55 26 11 0 3 7 9 10 39 11 15 23 22 16 62 0 0 0

55.D 83 85 2 2 13 25 41 142 46 8 30 30 82 25 18 25 3

Minimum 0 0 0 0 0 1 3 3 5 1 3 2 3 2 0 0 0

5th Percentile 0 4 0 0 1 6 8 15 23 5 7 10 12 10 5 4 2

Median 29 63 6 6 11 59 138 159 654 241 381 723 406 345 330 252 47

Mean 132 129 697 2391 2370 26482 30331 86630 712378 265140 427379 792369 409618 571906 83297 196103 5910

95th Percentile 546 409 3605 11982 8679 190609 170921 443019 1394745 720445 876820 4118580 1227492 762019 260418 317417 4721

Maximum 2414 1744 28293 78236 101872 628321 1301834 2277187 35040304 11365514 20092711 28996618 13436510 21381627 2635562 8042352 186359

SD 331 214 3133 10733 11215 82946 147866 298005 4048167 1418074 2409367 3743020 2028607 2823619 374328 1006750 28721

RSD (%) 250 166 450 449 473 313 488 344 568 535 564 472 495 494 449 513 486

Documents

Study of Coal Tar Sealant Application in Toronto