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

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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

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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

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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?

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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?

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

Stack Plume: Fanning

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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?

Stack Plume: Fumigation

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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?

Stack Plume: Lofting

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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

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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)

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Effects of Terrain on the Plume Pattern

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

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Q: Is stack height an important parameter?

Backwash

Downwash

Impact of Building and Stack Location

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Impact of Stack Height: Stack Upwind of Building

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Impact of Stack Height: Building Supported Stack

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Impact of Stack Height: Stack Downwind of Building

Conclusions?

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Cases of Downwash

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Plume Affected by Natural Terrain Irregularity

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Unstable Stable

Plume Near Very Large Obstacle

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Plume in a Valley

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Heat Island Effect

Q: When does the effect break?

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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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SummaryTake 2 minutes to summarize here what you have learned from this section