Presentation on theme: "Pavement Sealcoat, PAHs, and the Environment: An Introduction Barbara J. Mahler and Peter C. Van Metre U.S. Geological Survey SETAC, 9 November 2010."— Presentation transcript:
Pavement Sealcoat, PAHs, and the Environment: An Introduction Barbara J. Mahler and Peter C. Van Metre U.S. Geological Survey SETAC, 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 concentrations No trend Decreasing concentrations
Carcinogenic, teratogenic, mutagenic, and toxic Produced by combustion of organic matter Ubiquitous in the urban environment: Used motor oil Exhaust Industrial emissions Asphalt Tires Coal-tar-based pavement sealant What Are PAHs? (polycyclic aromatic hydrocarbons)
The 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 … whats 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 –9–9 Air particles, major roadway –104 Fresh asphalt –2–2 Weathered asphalt –9–9 Fresh motor oil –7–7 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 sealcoatuse? 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
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 Example source Example receptor
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