Atmosphere and PollutionCh. 18

Indoor air pollution can pose serious health risks, but they are risks that the individual can do much to

minimize their exposure; outdoor air pollution on the other hand can only be addressed by government

and regulation.

Guiding Questions• What is the composition,

structure, and function of the atmosphere?

• What are the major indoor and outdoor air pollutants?

• What is ozone depletion and what are the steps being taken to address it?

• How do weather and climate affect atmospheric conditions?

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The atmosphere

• Atmosphere = the thin layer of gases around Earth - Provides oxygen- Absorbs radiation and moderates climate- Transports and recycles water and nutrients

- 78% N2, 21% O2

• Human activity is changing the amount of some gases

- CO2, methane (CH4), ozone (O3)

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The first two layers of the atmosphere

• Troposphere = bottommost layer (11 km [7 miles])- Air for breathing, weather- The air gets colder with altitude- Tropopause = limits mixing between troposphere

and the layer above it• Stratosphere = 11–50 km (7–31 mi) above sea level

- Drier and less dense, with little vertical mixing- Becomes warmer with altitude- Contains UV radiation-blocking ozone, 17–30 km

(10–19 mi) above sea level

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Atmospheric properties

• Atmospheric pressure = the force per unit area produced by a column of air

• Relative humidity = the ratio of water vapor air contains to the amount it could contain at a given temperature - High humidity makes it

feel hotter than it really is• Temperature = varies with

location and time

Atmospheric pressure decreases with altitude

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Natural sources pollute: volcanoes

• Release particulate matter, sulfur dioxide, and other gases - Can remain for months or

years• Aerosols = fine droplets of

sulfur dioxide, water, oxygen- Reflect sunlight back to

space - Cool the atmosphere and

surface

Volcanoes are one source of natural air pollution, as shown by the Mount Saint Helens eruption in 1980

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Natural sources pollute: fires• Fires pollute the atmosphere with soot and gases• Over 60 million ha (150 million acres) of forests and

grasslands burn per year• Human influence makes fires worse

- Fuel buildup from fire suppression, development in fire-prone areas, “slash-and-burn” agriculture

- Climate change will increase drought and fires

In 1997, unprecedented forest fires sickened 20 million and caused a plane to crash

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We create outdoor air pollution• Air pollution comes from mobile or stationary sources• Point sources = specific spots where large quantities of

pollutants are discharged (power plants and factories)

• Non-point sources = more diffuse, consisting of many small sources (automobiles)

• Primary pollutants = directly harmful and can react to form harmful substances (soot and carbon monoxide)

• Secondary pollutants = form when primary pollutants interact or react with components of the atmosphere - Tropospheric ozone and sulfuric acid

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The EPA sets standards

• The EPA sets nationwide standards for emissions and concentrations of toxic pollutants

• States monitor air quality- They develop, implement, and enforce regulations- They submit plans to the EPA for approval

• The EPA takes over enforcement if plans are inadequate• Criteria pollutants = pollutants that pose especially

great threats to human health- Carbon monoxide, sulfur dioxide, nitrogen dioxide,

tropospheric ozone, particulate matter, lead

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Criteria pollutants: CO and SO2

• Carbon monoxide (CO) = colorless, odorless gas- Produced primarily by incomplete combustion of fuel- From vehicles and engines, industry, waste

combustion, residential wood burning- Poses risk to humans and animals, even in small

concentrations

• Sulfur dioxide (SO2) = colorless gas with a strong odor

- Coal emissions from electricity generation, industry- Can form acid precipitation

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Criteria pollutants: NO2

• Nitrogen dioxide (NO2) = a highly reactive, foul-smelling reddish brown gas

- Nitrogen oxides (NOx) = formed when nitrogen and oxygen react at high temperatures in engines

- Vehicles, industrial combustion, electrical utilities- Contribute to smog and acid precipitation

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Criteria pollutants: tropospheric ozone

• Tropospheric ozone (O3) = a colorless gas with a strong odor- Results from interactions of sunlight, heat, nitrogen

oxides, and volatile carbon-containing chemicals- A secondary pollutant- A major component of smog - Participates in reactions that harm tissues and cause

respiratory problems- The pollutant that most frequently exceeds EPA

standards

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Areas in the U.S. fail air quality standards

Many Americans live in areas with unhealthy levels of criteria pollutants

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U.S. air pollution

In 2008, the U.S. emitted 123 million tons of the six monitored pollutants

The average U.S. driver emits 6 metric tons of CO2/yr as well as other pollutants!

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We have reduced air pollution

• Total emissions of the six monitored pollutants have declined 60% since the Clean Air Act of 1970- Despite increased population, energy consumption,

miles traveled, and gross domestic product

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We reduced emissions and improved theeconomy• Technology and federal

policies• Cleaner-burning engines and

catalytic converters• Permit-trading programs and

clean coal technologies reduce SO2 emissions

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

• Phaseout of leaded gasoline

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Industrializing nations suffer increasing pollution

• Outdoor pollution is getting worse in developing nations• Factories and power plants pollute

- Governments emphasize economic growth, not pollution control

• People burn traditional fuels (wood and charcoal)- And more own cars

• China has the world’s worst air pollution- Coal burning, more cars, power plants, factories- Causing over 300,000 premature deaths/year

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Pollution in developing nations is high

More people own cars Smog in Beijing surrounds an Olympic stadium

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Smog: our most common air quality problem

• Smog = an unhealthy mixture of air pollutants over urban areas

• Sulfur in burned coal combines with oxygen to form sulfuric acid

• Industrial (gray air) smog = industries burn coal or oil- Regulations in developed

countries reduced smog• Coal-burning industrializing

countries face health risks- Coal and lax pollution control

Smog in Donora killed 21 people and sickened 6,000

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Photochemical (brown air) smog• Produced by a series of reactions

- Formed in hot, sunny cities surrounded by mountains• Light-driven reactions of primary pollutants and

atmospheric compounds- Morning traffic releases NO and VOCs- Irritates eyes, noses, and throats

• Los Angeles smog kills 3,900/year and costs $28 billion/year

High levels of NO2 cause photochemical smog to form a brown haze over cities

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Industrial smog Photochemical smog

Creation of industrial and photochemical smog