Plume characteristics

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Dispersion from Point Sources• Pollutants emitted in plume form

www.epa.gov/.../muncpl/landfill/sw_combst.htm

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

Aerosol & Particulate Research Lab

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• Plume rise affects transport– Effects maximum ground level concentrations (MGLCs)

– Effects distance of MGLCs

Under what conditions can we have a higher Effective Stack Height?

www.atmos.ucla.edu/.../chimneyplumes/Note03.html

Aerosol & Particulate Research Lab

04/12/23 Aerosol & Particulate Research Lab 3

Stack Plume: Looping

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?

http://www.med.usf.edu/~npoor/3

Strong turbulence

http://www.uwm.edu/~kahl/CoVis/Plume/stable.gif



Strong wind, no turbulence

Stack Plume: Coning

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?



Q: What is the stability class? What is the top view of the plume? What is the ground level concentration as a function of


http://www.med.usf.edu/~npoor/4

Stack Plume: Fanning



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


Stack Plume: Fumigation



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


Stack Plume: Lofting



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/

Stack Plume: Trapping


Effect of Surface Discontinuity

Cold land Warm water

Warm land Cold water

Q: What is the ground level concentration as a function of distance from the stack?

(b)

(c)

Warm land Cold water

(a)



Effects of Terrain on the Plume Pattern

Q: Does the shape of the building matter? Is the wake bigger at stable or unstable condition?


Q: Is stack height an important parameter?

Backwash

Downwash

Impact of Building and Stack Location


Impact of Stack Height: Stack Upwind of Building


Impact of Stack Height: Building Supported Stack


Impact of Stack Height: Stack Downwind of Building

Conclusions?


Cases of Downwash


Plume Affected by Natural Terrain Irregularity


Unstable Stable

Plume Near Very Large Obstacle


Plume in a Valley


Heat Island Effect

Q: When does the effect break?


Plume Affected by Heat Island Effect

Toward a city Within a city

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Long-Range Transport• Transport of pollutants hundreds/thousands of miles;

resulting in air quality problems far away from the source

Examples?

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)

Why only long-lived?Aerosol & Particulate Research Lab


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Plume characteristics