pavement sealcoat, pahs, and the environment: an introduction barbara j. mahler and peter c. van...
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Pavement Sealcoat, PAHs, and the Environment: An Introduction
Barbara J. Mahler and Peter C. Van Metre U.S. Geological SurveySETAC, 9 November 2010
USGS NAWQA Program: PAHs in lake sediment are
increasing
Van Metre et al., 2000, ES&T; Van Metre and Mahler, 2005, ES&T
Increasing concentrationsNo trendDecreasing concentrations
Carcinogenic, teratogenic, mutagenic, and toxic
Produced by combustion of organic matter
Ubiquitous in the urban environment:
Used motor oilExhaust Industrial emissionsAsphaltTiresCoal-tar-based pavement
sealant
What Are PAHs?What Are PAHs?(polycyclic aromatic hydrocarbons)
The first clue: high PAH in Austin stream-bed sedimentThe first clue: high PAH in
Austin stream-bed sediment
Extremely high (>1,500 mg/kg) PAHs in some small drainages
Compare to Probable Effect Concentration (PEC) of 23 mg/kg
So … what’s upstream?
What is sealcoat?
• Asphalt-based product• West of the Continental Divide
• Coal-tar based product contains coal-tar pitch
• East of the Continental Divide
How do urban sources of PAHs stack up?
• Tire wear particles– 175 (mean of 3 studies)
• Road dust– 59
• Brake-lining particles– 9
• Air particles, major roadway– 104
• Fresh asphalt– 2
• Weathered asphalt– 9
• Fresh motor oil– 7
• Used motor oil– 726
• Diesel engine– 304 (mean of 2 studies)
• Gasoline engine– 35
• Pavement sealcoat– Asphalt based ~ 50– Coal-tar-based ~
92,000 (mean of 4 products)
All concentrations in mg/kg
Environmental relevance
• Is use extensive?• Is the contaminant mobile?• Are concentrations elevated?
How extensive is sealcoat use?
• 200,000 gallons applied annually in Springfield, MO, area (applicator estimate)
• 1,400,000 gallons applied annually to New York Harbor watershed (New York Academy of Science estimate)
• 4,800,000 gallons (20,000 tons) of CT-based sealcoat applied in Texas annually (sealcoat industry estimate)
• Within watersheds:
– 4 watersheds in Texas: 1-2% area
– 1 watershed in Illinois: 4% of area• 42% of parking lot
area• 89% of driveway
area
Sealed570
3,800
3,400
1,3002.1
24
21
4730
0.8
Unsealed
Coal tarAsphalt
9 U.S. Cities: Pavement Dust PAH (mg/kg)
1,200
54
<13
5.2
8.5
<8.5
3,200
Van Metre et al., ES&T, 2009
23 ground-floor apartments
Ancillary Information Gathered
• Smoking• Incense/candles• Fireplace use• Type of stove/heat• Shoe wear in house• Indoor/outdoor pets• Distance to major
roadway• Intensity of urbanization
including
Out-CT = 530 x Out-NCTIn-CT = 25 x In-NCT
5.15.1
9.09.0
129129
4,7604,760
Median total PAH [mg/g]
n=12 n=11
Mahler et al., 2010, ES&T
Increasing trends in PAHs
What are the principal sources of PAHs to urban lakes?
Source-Apportionment Modeling
• Start with source profiles• receptor profiles• CMB model combines
sources to best match the receptor profile
• Results are the contribution of each source to each sediment sample
PhA-C
An-CFlA
-CPy-
C
BaA-C
Chy-C
BbF-C
BkF-C
BeP-C
BaP-C
IP-C
BgP-C
00.020.040.060.08
0.10.120.140.160.18
0.2
Lake in the Hills sediment
Example source
Example receptor
Phe FluBaA BbF BeP
IndP
y0.000.020.040.060.080.100.120.14
Traffic tunnel air
PA
H,
pro
po
rtio
nal
Sources Considered• Coal combustion
– Power plant emissions– Residential heating– Coke oven
• Fuel-oil combustion• Vehicle related
– Diesel vehicle emissions– Gasoline vehicle emissions– Traffic tunnel air– Used motor oil– Tire particles– Asphalt
• Wood burning– Pine-wood soot particles
• Coal-tar-sealcoat related– NIST coal tar standard– Sealcoat products– Sealcoat scrapings– Sealcoat dust (average, 6 cities)– Sealcoat dust, Austin
PAH Source Apportionment to 40 U.S. Lakes
Mass PAH contribution from coal-tar-based sealcoat
Van Metre and Mahler, STOTEN, in press
PAH Trends in New Urban Lakes
All urban is not equal
Decker Lake2,090 people/km
SPAH 0.76 mg/kg
Tanasbrook Pond844 people/km
SPAH 1.34 mg/kg
Lake Anne2,095 people/km
SPAH 17.0 mg/kg
Palmer Lake939 people/km
SPAH 34.1 mg/kg