chapter 12: air pollution a brief history of air pollution a brief history of air pollution types...

Chapter 12: Air Chapter 12: Air PollutionPollution

A brief history of air pollutionA brief history of air pollution Types and sources of air pollutantsTypes and sources of air pollutants Factors that affect air pollutionFactors that affect air pollution Air pollution and the urban environmentAir pollution and the urban environment Acid depositionAcid deposition

A Brief History of Air A Brief History of Air PollutionPollution

London’s historical problemsLondon’s historical problems King Edward I forbid sea coal in 1273King Edward I forbid sea coal in 1273 London known for “pea-soup” (dangerous)London known for “pea-soup” (dangerous) One “pea-soup” incident caused 700 deathsOne “pea-soup” incident caused 700 deaths Term “smog” created around 1911Term “smog” created around 1911

Disastrous London smog event of 1952Disastrous London smog event of 1952 Winds died, smog settled over LondonWinds died, smog settled over London People could see where they were walking for 5 People could see where they were walking for 5

daysdays Killed 5,000 livesKilled 5,000 lives Caused Parliament to pass Clean Air Act of 1956Caused Parliament to pass Clean Air Act of 1956

A Brief History of Air A Brief History of Air PollutionPollution

Donora, Pennsylvania pollution Donora, Pennsylvania pollution episode, 1948episode, 1948 Pollution trapped in Monongahela River Pollution trapped in Monongahela River

Valley by inversion (20 people died)Valley by inversion (20 people died) U.S. Clean air act, 1970, 1990U.S. Clean air act, 1970, 1990

Due to high pollution, Congress passed Due to high pollution, Congress passed Clear Air Act (revised in 1977, 1990)Clear Air Act (revised in 1977, 1990)

Sets emission standardsSets emission standards Incentives for companies to lower Incentives for companies to lower

emissionemission

Principal Air PollutantsPrincipal Air Pollutants

Primary pollutantsPrimary pollutants Enter atmosphere directlyEnter atmosphere directly

Secondary pollutantsSecondary pollutants Enter atmosphere from chemical Enter atmosphere from chemical

reactionsreactions

• Globally, a large percentage of air pollution sources are Globally, a large percentage of air pollution sources are natural. Within localized areas, however, human-natural. Within localized areas, however, human-caused sources are often the largest contributors.caused sources are often the largest contributors.

Principal Air PollutantsPrincipal Air Pollutants Particulate matterParticulate matter – solid particles and – solid particles and

liquid droplets small enough to remain liquid droplets small enough to remain suspended (aerosols). suspended (aerosols). Not poisonous - soot, smoke, dust, pollenNot poisonous - soot, smoke, dust, pollen More dangerous – asbestos, arsenic, oil, sulfuric More dangerous – asbestos, arsenic, oil, sulfuric

acidacid PM10PM10 – Particulates with diameters < 10 – Particulates with diameters < 10

micrometersmicrometers Small enough to penetrate into lungsSmall enough to penetrate into lungs Can remain in air for long timeCan remain in air for long time Wind can carry great distancesWind can carry great distances Asian dust can transport dust long distances Asian dust can transport dust long distances


PM2.5PM2.5 – Particulates with diameters – Particulates with diameters < 2.5 micrometers< 2.5 micrometers Penetrate farther into lungsPenetrate farther into lungs Found in diesel soot and are Found in diesel soot and are

carcinogenic (school buses, traffic carcinogenic (school buses, traffic corridors)corridors)

Removed by rain, snow, ice crystalsRemoved by rain, snow, ice crystals


Carbon MonoxideCarbon Monoxide – major pollutant – major pollutant in cities. Colorless, odorless, in cities. Colorless, odorless, poisonous gaspoisonous gas 60 million metric tons enter U.S. air 60 million metric tons enter U.S. air

annually. Half from highway vehicles.annually. Half from highway vehicles. Extremely dangerous and can kill Extremely dangerous and can kill

quickly in poorly ventilated areas.quickly in poorly ventilated areas.


Sulfur dioxideSulfur dioxide – comes from sulfur- – comes from sulfur-containing fossil fuels. Colorless. containing fossil fuels. Colorless. Comes from power plants, heating Comes from power plants, heating devices, paper mills, volcanoesdevices, paper mills, volcanoes Can form into secondary pollutants Can form into secondary pollutants

(sulfur trioxide, sulfuric acid(sulfur trioxide, sulfuric acid Hurt breathing and certain plantsHurt breathing and certain plants

Principal Air PollutantsPrincipal Air Pollutants Volatile organic compoundsVolatile organic compounds – organic – organic

compounds mainly made of hydrogen and compounds mainly made of hydrogen and carboncarbon Methane, benzene, formaldehyde, Methane, benzene, formaldehyde,

chlorofluorocarbanschlorofluorocarbans Nitrogen oxidesNitrogen oxides – formed when nitrogen – formed when nitrogen

combines with oxygen during fuel combines with oxygen during fuel combustioncombustion Nitrogen dioxide, nitric oxide (NOx)Nitrogen dioxide, nitric oxide (NOx) Vehicles, power plants, garbage dumpsVehicles, power plants, garbage dumps

• Along with ozone, VOCs and NOx are major Along with ozone, VOCs and NOx are major components of photochemical smog.components of photochemical smog.

Ozone in the Ozone in the TroposphereTroposphere

Photochemical smogPhotochemical smog – formed when – formed when chemical reaction takes place with chemical reaction takes place with sunlightsunlight

OzoneOzone – Dangerous at surface. Irritates – Dangerous at surface. Irritates eyes, lungs. Can cause asthma and eyes, lungs. Can cause asthma and bronchitisbronchitis Causes several billions of dollars in loss from Causes several billions of dollars in loss from

crop yield crop yield

• Photochemical smog is a problem on most major Photochemical smog is a problem on most major cities of the world.cities of the world.

Ozone in the Ozone in the TroposphereTroposphere

Ozone in the Ozone in the StratosphereStratosphere

Relationship to Relationship to ultraviolet radiationultraviolet radiation Ozone layer shields Ozone layer shields

surface from UV surface from UV radiationradiation

UV can cause skin UV can cause skin cancercancer

Eye cataractsEye cataracts Hurt immune systemHurt immune system


Ozone broken down Ozone broken down into O2 and O when UV into O2 and O when UV hits ithits it

Chloroflucarbons Chloroflucarbons (CFCs) where used in (CFCs) where used in hairsprays, deodorants, hairsprays, deodorants, propellants until 1987 propellants until 1987 (Montreal Protocol)(Montreal Protocol)

Stable at surface, enter Stable at surface, enter stratosphere from t-stratosphere from t-storms, near jet storms, near jet streamsstreams


Sunlight breaks off Sunlight breaks off the Chlorine and it the Chlorine and it breaks up ozonebreaks up ozone

CFCs are very long-CFCs are very long-lastinglasting

One CFC can One CFC can destroy 100,000 destroy 100,000 Ozone moleculesOzone molecules

Air Pollution: Trends and Air Pollution: Trends and PatternsPatterns

Primary air quality standardsPrimary air quality standards – – standards set up to protect human standards set up to protect human healthhealth

secondary air quality standardssecondary air quality standards- - standards set up to protect visibility, standards set up to protect visibility, crops, and buildingscrops, and buildings

Nonattainment areasNonattainment areas – areas that do – areas that do no meet air quality standardsno meet air quality standards• Secondary air pollutants are particularly difficult to Secondary air pollutants are particularly difficult to

control, because they are not emitted directly into the control, because they are not emitted directly into the atmosphere.atmosphere.

Air Pollution: Trends and Air Pollution: Trends and PatternsPatterns

80 millions Americans breathing air 80 millions Americans breathing air not meeting one standardnot meeting one standard

Air Quality Index (AQI)Air Quality Index (AQI) – includes – includes carbon monoxide, sulfur dioxide, carbon monoxide, sulfur dioxide, nitrogen dioxide, particulate matter, nitrogen dioxide, particulate matter, ozoneozone Highest pollutant is one used in indexHighest pollutant is one used in index Anything higher than 100 is unhealthyAnything higher than 100 is unhealthy

Fig. 12-11, p. 338

The Role of the WindThe Role of the Wind

The Role of the WindThe Role of the Wind

DilutionDilution – mixing air pollution in a – mixing air pollution in a greater volume of air. Can create greater volume of air. Can create problems downwindproblems downwind

• ““Dilution is the solution to pollution” - in the 1950s this motto led to the Dilution is the solution to pollution” - in the 1950s this motto led to the construction of tall smokestacks for large factories. Pollution was released construction of tall smokestacks for large factories. Pollution was released higher in the atmosphere where winds were stronger. Air quality improved higher in the atmosphere where winds were stronger. Air quality improved locally but suffered downwind.locally but suffered downwind.

The Role of Stability and The Role of Stability and InversionsInversions

Temperature lapse Temperature lapse ratesrates

Inversions inhibit Inversions inhibit vertical movement. vertical movement. Keep pollutants in a Keep pollutants in a layerlayer

Mixing depth – the Mixing depth – the depth of the mixing depth of the mixing layer (the layer from layer (the layer from the surface to the top the surface to the top of the inversion)of the inversion)• The mixing layer can often be easily seen from an airplane.The mixing layer can often be easily seen from an airplane.

The Role of Stability and The Role of Stability and InversionsInversions

The Role of TopographyThe Role of Topography

Cold air drainageCold air drainage – air drains – air drains downhill over night, carrying downhill over night, carrying pollutantspollutants

Air blockage by mountain ranges. Air blockage by mountain ranges. Mountains block the progress of Mountains block the progress of flow. Blocks pollutants from moving flow. Blocks pollutants from moving out of the regionout of the region

The Role of TopographyThe Role of Topography

Severe Air Pollution Severe Air Pollution PotentialPotential

Many sources (clustered close Many sources (clustered close together)together)

High pressure (becomes stationary, High pressure (becomes stationary, light winds)light winds)

Inversions (inhibits vertical movement)Inversions (inhibits vertical movement) Stagnation (pollutants unable to Stagnation (pollutants unable to

disperse)disperse) Valley (pollutants accumulate)Valley (pollutants accumulate)

• Some locations, like Los Angeles and Mexico City, have an Some locations, like Los Angeles and Mexico City, have an unfortunate combination of surrounding topography, unfortunate combination of surrounding topography, frequent inversions, abundant emissions and plentiful frequent inversions, abundant emissions and plentiful sunlight - perfect conditions for photochemical smog.sunlight - perfect conditions for photochemical smog.

Air Pollution and the Air Pollution and the Urban EnvironmentUrban Environment

Urban heat island – cities are warmer Urban heat island – cities are warmer than rural areasthan rural areas

Country breezeCountry breeze – Return breeze in – Return breeze in circulationcirculation

Acid DepositionAcid Deposition Dry depositionDry deposition – when – when

pollutants slowly settle pollutants slowly settle to groundto ground

Wet depositionWet deposition – when – when pollutants are carried to pollutants are carried to ground by rain, snowground by rain, snow

Acid rain effectsAcid rain effects

• Strangely enough, an acidified lake looks crystal clear Strangely enough, an acidified lake looks crystal clear and beautiful. But the beauty is false; it’s only clear and beautiful. But the beauty is false; it’s only clear because nothing is alive in it.because nothing is alive in it.

chapter 12: air pollution a brief history of air pollution a brief history of air pollution types...

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