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Dispersion from Point Sources

Why does plume expand downwind?. What are the factors that influence the history of plume?. Impact on air quality depends on dispersion, which depends on the height of plume. Dispersion from Point Sources. Pollutants emitted in plume form. www.epa.gov/.../muncpl/landfill/sw_combst.htm.

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Dispersion from Point Sources

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  1. Why does plume expand downwind? What are the factors that influence the history of plume? Impact on air quality depends on dispersion, which depends on the height of plume Dispersion from Point Sources • Pollutants emitted in plume form www.epa.gov/.../muncpl/landfill/sw_combst.htm Aerosol & Particulate Research Lab

  2. Under what conditions can we have a higher Effective Stack Height? • Plume rise affects transport • Effects maximum ground level concentrations (MGLCs) • Effects distance of MGLCs www.atmos.ucla.edu/.../chimneyplumes/Note03.html Aerosol & Particulate Research Lab

  3. Stack Plume: Looping Strong turbulence http://www.uwm.edu/~kahl/CoVis/Plume/stable.gif Q: Is it at stable or unstable condition? High or low wind speed? Does it happen during the day or night? Is it good for dispersing pollutants? Aerosol & Particulate Research Lab http://www.med.usf.edu/~npoor/3

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  5. Stack Plume: Coning Strong wind, no turbulence What is the stability class? Good vertical mixing? On sunny or cloudy days? Good for dispersing pollutants? What is the ground level concentration as a function of distance from the stack? Aerosol & Particulate Research Lab

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  7. Stack Plume: Fanning http://www.med.usf.edu/~npoor/4 Q: What is the stability class? What is the top view of the plume? What is the ground level concentration as a function of distance from the stack? Aerosol & Particulate Research Lab

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  9. Stack Plume: Fumigation Q: Why can’t the pollutants be dispersed upward? Does it happen during the day or night? What’s your opinion about requiring power plants to reduce their power output from 3 am to 3 hours after sunrise? What is the ground level concentration as a function of distance from the stack? Aerosol & Particulate Research Lab

  10. Aerosol & Particulate Research Lab

  11. Stack Plume: Lofting Q: Why can’t the pollutants be dispersed downward? When does it happen? Lofting is a transition stage. To which type of plume? What is the ground level concentration as a function of distance from the stack? Aerosol & Particulate Research Lab

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  13. Stack Plume: Trapping Q: What is the stability class? What is the ground level concentration as a function of distance from the stack? http://www.uwm.edu/~kahl/CoVis/Plume/ Aerosol & Particulate Research Lab

  14. Effect of Surface Discontinuity (a) (b) Cold water Warm land (c) Warm water Cold land Cold water Warm land Q: What is the ground level concentration as a function of distance from the stack? Aerosol & Particulate Research Lab

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  16. Effects of Terrain on the Plume Pattern Q: Does the shape of the building matter? Is the wake bigger at stable or unstable condition? Aerosol & Particulate Research Lab

  17. Impact of Building and Stack Location Backwash Downwash Q: Is stack height an important parameter? Aerosol & Particulate Research Lab

  18. Impact of Stack Height:Stack Upwind of Building Aerosol & Particulate Research Lab

  19. Impact of Stack Height:Building Supported Stack Aerosol & Particulate Research Lab

  20. Impact of Stack Height:Stack Downwind of Building Conclusions? Aerosol & Particulate Research Lab

  21. Cases of Downwash Aerosol & Particulate Research Lab

  22. Plume Affected by Natural Terrain Irregularity Aerosol & Particulate Research Lab

  23. Plume Near Very Large Obstacle Stable Unstable Aerosol & Particulate Research Lab

  24. Plume in a Valley Aerosol & Particulate Research Lab

  25. Heat Island Effect Q: When does the effect break? Aerosol & Particulate Research Lab

  26. Plume Affected by Heat Island Effect Toward a city Within a city Aerosol & Particulate Research Lab

  27. Examples? Why only long-lived? Long-Range Transport • Transport of pollutants hundreds/thousands of miles; resulting in air quality problems far away from the source Planetary Transport • Stable air above PBL retards vertical mixing • Transport out of PBL to free troposphere takes few hours to few days • Transport to top of troposphere with uniform mixing takes about a week (for long-lived pollutants, e.g. CO2, CH4, CFC) Aerosol & Particulate Research Lab

  28. Summary Take 2 minutes to summarize here what you have learned from this section Aerosol & Particulate Research Lab

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