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Ch. 17 Atmosphere and Air Pollution

Rules/Regulations

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New York City – Congestion pricing??

The atmosphere’s composition

Composition

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ThermosphereUp to 500km (300 mi)High temp – would feel cold

Mesosphere50-80km (31-56mi)Low pressure, temp. drops

Stratosphere 11-50 km (7-31 mi)Drier/less denseTemp. increases with altitude due to O3 (17-30kim or 10-19 mi)

TroposphereAvg. thickness 11km (7 mi)WeatherTemperature/density decline with altitude

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Atmospheric Pressure=force per unit area produced by a column of air

Sea Level = 1013 mb (14.7 lb/in2 )

29035 ft (Everest top)= 300mb

Atmospheric properties

• Relative humidity = the ratio of water vapor a given volume of air contains to the amount it could contain at a given temperature. Expressed as percent

• Temperature = average kinetic energy in molecules

• Thermometer = molecular speedometer

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• Equator – Angle of incident radiation perpendicular, greatest concentration of energy

• Poles – Angle of incident radiation obtuse, less concentrated

***The troposphere is warmed primarily by convection

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Seasons

Weather: local physical properties of the troposphere over short time periods: temp, pressure, cloud cover, wind , humidityClimate: patter of atmospheric conditions found across large geographic regions over long periods of time

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Convective Circulation

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• Air Pollutants removed by:– Precipitation– mixing

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Mixing removes pollutants

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Pollutants trapped

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Large scale convective cells determine global patterns of humidity and aridity

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Coriolis Effect – apparent deflection of air from straight path as globe moves beneath

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Outdoor Air Pollution(Ambient)

Natural Sources:

Dust StormsCarry fungal and bacterial spores

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Volcanoes:Particulates including ash, aerosols of SO2 can cool atmosphere

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Fires:Particulates and gases

Types of outdoor air pollution

• Point Sources = specific spots where large quantities of pollutants are discharged (power plants and factories)

• Nonpoint Sources = more diffuse, consisting of many small sources (automobiles)

• Primary Pollutants = directly harmful ,and can react to form other harmful substances

• Secondary Pollutants = form when primary pollutants interact with components of the atmosphere

Anthropogenic Sources

Primary PollutantsPrimary Pollutants

StationaryStationaryMobileMobile

SourcesSourcesNaturalNatural

Most Most hydrocarbonshydrocarbons

Most suspendedMost suspendedparticlesparticles

SOSO22 NONO NONO22

COCO COCO22 Secondary PollutantsSecondary Pollutants

SOSO33

HNOHNO33HH22SOSO44

HH22OO22OO33 PANsPANs

MostMost NONO33––

SOSO4422 –– saltssalts

Successful legislation• Clean Air Act of 1970– standards for air quality– limits on emissions– funds for pollution-control research – Allows citizens to sue parties violating the

standards

• The Clean Air Act of 1990– Strengthens standards for auto emissions, toxic

air pollutants, acidic deposition, stratospheric ozone depletion

– Introduced emissions trading for SO2

6 Criteria Pollutants

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What is the good news????

Air pollution has decreased since 1970

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Remove up to 90% particulates and SO2

Reasons for the decline in U.S. pollution

• Cleaner-burning vehicles and catalytic converters decrease carbon monoxide

• Permit-trading programs and clean coal technologies reduce SO2 emissions

• Scrubbers = technologies that chemically convert or physically remove pollutants before they leave the smokestacks

• Phaseout of leaded gasoline• Improved technologies and

federal policies

• 17.16

Industrial smog Photochemical smog

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Photochemical Smog

Photochemical (brown air) smog

• Produced by a series of reactions– Hot, sunny cities

surrounded by mountains– Light-driven reactions of

primary pollutants and normal atmospheric compounds

– Morning traffic exhaust releases pollutants

– Irritant – eyes, throat, nose– decreased due to emissions

testing

Photochemical Smog

1. 2NO+ O2 2NO2 2. NO2 + UV NO + O3. O2 + O O3

Typical Daily Patterns

Air Quality Guide for Ozone

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Stratospheric Ozone

The hole in the ozone

• Ozone hole = ozone levels over Antarctica had declined by 40-60% – Depletion also in the Arctic and globally– Causes skin cancer, harms crops and

decreases ocean productivity

The Montreal Protocol addressed ozone depletion• Montreal Protocol = 180 nations agreed to cut CFC production in half

– Follow-up agreements deepened cuts

– ozone-depleting chemicals has decreased 95%

– The ozone layer is beginning to recover

– Success story

• included industry

• adaptive management strategy

– Model for international cooperation

Sources of acid deposition

• Originates from burning fossil fuels that release sulfur dioxide and nitrogen oxides– These compounds react with water to form sulfuric

and nitric acids

Acid Deposition

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Acid deposition has not been greatly reduced

• Scrubbers have helped

• SO2 emissions are lower (cap and trade)

• But, NOx emissions are higher

Acid Deposition not Greatly Reduced

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Indoor Air Quality

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