Air Pollution and Dispersion Models

8/10/2019 Air Pollution and Dispersion Models

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Air Pollution and DispersionModels

Lecture OutlineIntroduction to Air Pollution

Air pollutants and their effectsIntensity of air pollution

Pollution dispersion modelsComputer modeling in air pollution


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Introduction to Air Pollution

Definition any atmospheric condition in whichsubstances are present at concentrations highenough above their normal ambient levels to

produce a measurable effect on man, animals,vegetation or materialsFact 1 90% of the respirable particle mass in the earths

atmosphere is natural Wind blown, sea spray

10% is anthropogenic The 10% is more concentrated Uneven distribution geographically Combustion industrial, traffic and incineration Anthropogenic particles in general are more harmful


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Fact 2 Air pollution kills eight thousand people everyday

world wide, according to a recent internationalCommonwealth Science Council conference Estimates about 2.8 million people die each year

due to indoor pollution (over 500,000 in Chinaalone)

About 200,000 deaths are due to outdoor airpollution

Chronic and acute effects


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Air Pollutants and their effects

Human health effectsImpacts the economy and the environment

cause greater employee absenteeism as well asincreased medical expenses. destruction of trees, plants and agricultural crops,

which can decrease property value and income. Livestock and aquatic life are also affectedDeterioration of property decays rubber, iron and nylon it makes paint peel and discolor it blocks natural sunlight Acid rain corrosive to buildings


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Effects of Ozone on Trees


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Effects of Global Warming


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Table 1 Major pollutants in our air

Pollutant Sources Health effects

Carbonmonoxide Car exhausts, burning of fossil fuels

Carbon monoxide is absorbed by the blood morereadily than oxygen, thus reducing the amount ofoxygen being carried through the body. It canproduce tiredness and headaches. People with heartproblems are particularly at risk.

Sulfurdioxide

Coal and oil burning power stations,mineral ore processing andchemical manufacture.

Attacks the throat and lungs. People with breathingproblems can suffer severe illness.

Nitrogendioxide Burning of fossil fuels Affects the throat and lungs.

Ozone Formed from nitrogen oxides andhydrocarbons in sunny conditions.These chemicals are released bymotor vehicles and industry.

Ozone attacks the tissue of the throat and lungs andirritates the eyes.

Lead Exhaust gases from motor vehicleswhich use leaded petrol, smelters.

Particles containing lead in the air can enter thelungs. The lead can then be absorbed into the bloodstream. Over a period lead can affect the nervoussystem and the body's ability to produce blood.

Particles Motor vehicles, burning of plantmaterials, bushfires. May cause breathing difficulties and worsenrespiratory diseases. Some particles contain cancer-producing materials.


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Intensity of Air Pollution

2 important parametersRate at which pollutants are emitted

Dependent on size and function of cityRate at which pollutants are dispersed and dilutedwithin the atmosphere dependent on weather,height of chimney stacks, and topography

High temperatures -> increased buoyancy of gases->increased dispersion Valleys or basins sandwiched amongst hills ->

temperature inversion conditions


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Weather elements Wind direction and speed

Higher wind speeds -> increased dispersion Pollution higher in leeward side compared with

windward sides Vertical temperature profile which determines

the stability or otherwise of the air, andtherefore the resulting behaviour of the

pollution plume


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6 geometrical forms of the pollution plume1. Looping

Occurs under strong lapse conditions withmoderate to high wind velocities and largeconvective mixing of air.

If stacks are low, looping can produce high

surface concentrations of pollutants2. Conning

Occurs under weak lapse conditions


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6 geometrical forms of the pollution plume3. Fanning

Occurs under temperature inversion conditionsresulting particularly from terrestrial radiation onclear, calm nights

4. Lofting Occurs under conditions of shallow radiation

inversion near the ground surface and slightunstable conditions aloft


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6 geometrical forms of the pollution plume

5. Trapping Associated with a subsidence inversion situation

in which there is a weak lapse near the ground but inversion aloft.

Regarded as one of the worst pollution situations

6. Fumigation Commonly occurs after sunrise when solar

heating produces an unstable layer which mixessurface air with pollutants accumulated belownight inversion


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Pollution Dispersion Models

See handout


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Computer modeling

Energy and Climate in the Urban BuiltEnvironment, Chapter 9

Visit EPA websitehttp://www.epa.gov/oar/oaqps/modeling.html

Air Pollution and Dispersion Models

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