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Regional Modeling of The Atmospheric Fate and Transport of Benzene and Diesel Particles with CMAQ

Regional Modeling of The Atmospheric Fate and Transport of Benzene and Diesel Particles with CMAQ. Christian Seigneur, Betty Pun Kristen Lohman, and Shiang-Yuh Wu AER San Ramon, CA. Acknowledgments.

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Regional Modeling of The Atmospheric Fate and Transport of Benzene and Diesel Particles with CMAQ

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  1. Regional Modeling of The Atmospheric Fate and Transport of Benzene and Diesel Particles with CMAQ Christian Seigneur, Betty Pun Kristen Lohman, and Shiang-Yuh Wu AER San Ramon, CA

  2. Acknowledgments • Project A-42-1 funded by the Coordinating Research Council (CRC) and the U.S. DOE Office of FreedomCAR and Vehicle Technologies through the National Renewable Energy Laboratory (NREL)

  3. Air Toxics Regional Model • CMAQ • with benzene chemistry • with “diesel particles” species

  4. Benzene Chemistry • C6H6 + OH Products • k = 1.3 x 10-12 cm3 molec-1 s -1 at 298 K • Benzene half-life of about 1 week • OH concentrations from CMAQ chemistry (CBM-IV)

  5. Diesel Particles • A fixed bimodal distribution of diesel particles was assumed for the emitted and ambient diesel particles, with modes centering around 0.055 and 0.5 m. • Dry deposition is simulated using the algorithm of Venkatram and Pleim (1999)

  6. Application to the Northeast • Domain: Northeastern United States • Period: July 11-15, 1995 • Models: 3-D nested regional model (modified CMAQ) with 12 and 4 km horizontal resolution

  7. Nested Modeling Domains 47

  8. Emission Inventories • Benzene: National Toxics Inventory (1996) with spatial resolution by county and annual resolution • Diesel particles: National Emission Inventory (1996) with spatial resolution by county and annual resolution • SMOKE emission processing • surrogate files for spatial distribution (e.g., major highways, population) • temporal profiles (seasonal, weekday/weekend, diurnal) according to SCC

  9. Emissions of Benzene (moles/hr)

  10. Benzene Concentrations (ppm)15 July 1995, 6 a.m., 12 km resolution

  11. Benzene Concentrations (ppm)15 July 1995, 6 a.m., 4 km resolution

  12. Comparison of Simulated Urban and Rural Benzene Concentrations (ppm)

  13. Benzene (ppb)Simulation vs. Measurements Location Simulation Measurements(1) Urban 1 - 5 0.9 - 26 Suburban - 0.1 – 0.6 0.1 - 0.5 Rural Remote < 0.1 0.008 – 0.2 (1) Finlayson-Pitts & Pitts, 1999

  14. Model Performance forBenzene Concentrations

  15. Emissions of Diesel Particles (kg/hr)

  16. Diesel Concentrations (mg/m3)15 July 1995, 6 a.m., 12 km resolution

  17. Diesel Concentrations (mg/m3)15 July 1995, 6 a.m., 4 km resolution

  18. Comparison of Simulated Urban and Rural Diesel Concentrations (mg/m3)

  19. Elemental Carbon(1) (mg/m3)Simulation vs. Measurements Location Simulation(2) Measurements(3) Urban 1 - 21 0.8 – 20 Suburban - 0.2 – 2 0.5 - 2 Rural Remote 0.05 - 0.2 0.005 – 0.5 (1) Elemental carbon (EC) is an operational definition of the analytical measurement technique (2) assuming 50% EC in diesel particles (3) Seinfeld and Pandis, 1998

  20. Elemental Carbon(1) (mg/m3)Simulation vs. Measurements on July 15 Location Simulation(2) Measurements(3) E. Forsythe, NJ 0.53 1.16 Washington, D.C. 1.51 1.89 (1) Elemental carbon (EC) is an operational definition of the analytical measurement technique (2) assuming 50% EC in diesel particles (3) IMPROVE

  21. Conclusion • CMAQ was modified to simulate two air toxics: • Benzene • Diesel particles • Regional model gives realistic atmospheric concentrations for benzene and diesel particles • Regional background can have a significant impact on peak urban concentrations • Elemental carbon (EC) is not a good surrogate for diesel particles because of other EC sources

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