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Peter Van Metre and Barbara Mahler U.S. Geological Survey

PAH sources to 40 U.S. urban lakes. Peter Van Metre and Barbara Mahler U.S. Geological Survey. NAWQA – National Water Quality Assessment Program. Contaminant Trends in Lake Sediments. CTLS: http://tx.usgs.gov/coring/index.html. PAHs. Large group of organic compounds

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Peter Van Metre and Barbara Mahler U.S. Geological Survey

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  1. PAH sources to 40 U.S. urban lakes Peter Van Metre and Barbara Mahler U.S. Geological Survey

  2. NAWQA – National Water Quality Assessment Program Contaminant Trends in Lake Sediments CTLS: http://tx.usgs.gov/coring/index.html

  3. PAHs Large group of organic compounds Produced by combustion of organic matter Many are carcinogenic, mutagenic, teratogenic, or toxic (polycyclic aromatic hydrocarbons) Phenanthrene Pyrene Benzo(a)pyrene

  4. How do sources compare? 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 Coal-tar-based pavement sealant 92,000 ~1 to 50 mg/kg in urban lake sediment All concentrations in mg/kg

  5. Upward trends in PAHs 1970 to present Increasing concentrations No trend Decreasing concentrations Van Metre and Mahler, 2005, Environmental Sci. & Tech.

  6. What is sealcoat? Used to protect asphalt and improve appearance

  7. What is sealcoat? Used to protect asphalt and improve appearance • First recognized as PAH source in 2005 • Coal-tar based and asphalt based products • CT sealcoat is 5-10% PAH; 1,000x ASP sealcoat • CT use greater east of Continental Divide; ASP in west Mahler et al., 2005, Environmental Sci. & Tech.

  8. PAH in pavement dust Van Metre et al., 2009, Environmental Sci. & Tech. Coal tar Asphalt

  9. Modeling Approach • Used CMB to determine recent (post-1990) sources for 40 lakes; long-term trends in 8 lakes • Over 200 modeling runs; many combinations of sources, PAHs, and lakes • Identified the 4 best performing models • Summarized results for five source categories

  10. How CMB works • Uses proportional PAH profiles (12 PAH) in many sources • Adds source contributions to get best match of receptor profile (lake sediment) by minimizing Chi-squared (X2) • Provides estimated mass loading and uncertainty for each source PAH, low to high molecular weight

  11. Sources Considered • Coal combustion • Power plant emissions • Residential heating • Coke oven • Vehicle related • Diesel vehicle emissions • Gasoline vehicle emissions • Traffic tunnel air • Used motor oil • Tire particles • Asphalt • Fuel-oil combustion • 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

  12. PAH Sources to 40 U.S. Lakes

  13. PAH concentrations and sealcoat 6.9–81 mg/kg PEC 0.09–1.4 mg/kg

  14. PAH Trends in New Urban Lakes

  15. All urban is not equal Palmer Lake 939 people/km SPAH 34.1 mg/kg Tanasbrook Pond 844 people/km SPAH 1.34 mg/kg Lake Anne 2,095 people/km SPAH 17.0 mg/kg Decker Lake 2,090 people/km SPAH 0.76 mg/kg

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