1. The Atmosphere 15
CHAPTER
Placeholder opening page, but maybe we can duplicate the look of the SE chapter opener page by using the same fonts and colors (and maybe that Ch 14 icon?)

2. Charging Toward Cleaner Air in London
More than 4000 people in London died during a “killer smog” event in 1952.
In 2003, London started charging a fee to people who drove into the city during the week.
Since the program began, traffic congestion in London has decreased by 30%, but there is not a lot of evidence that air quality has improved.
Talk About It What are the pros and cons of a congestion-charging program?

3. Lesson 15.1 Earth’s Atmosphere
The air we breathe and all the weather we see is contained in the lowest 1% of the Earth’s atmosphere.

4. Properties of the Atmosphere
Lesson 15.1 Earth’s Atmosphere
Properties of the Atmosphere
Composition: 78% nitrogen, 21% oxygen, and 1% other gases
Temperature: Varies and location
Pressure: In general, air pressure decreases with altitude; can be measured using a barometer.
Barometer

5. Lesson 15.1 Earth’s Atmosphere
Relative Humidity
The ratio of water vapor in air to the maximum amount the same air could contain at the same temperature
Is affected by temperature and location; in general, warm air holds more water.
When air cools, water vapor may condense to liquid or to ice. Water vapor can only condense on surfaces, such as a petal or a dust particle.
Hoarfrost on leaves

6. Layers of Atmosphere Troposphere: 0–11 km; movement of air, weather
Lesson 15.1 Earth’s Atmosphere
Did You Know? The stratosphere and mesosphere are cold, but the upper thermosphere can be hotter than 1500°C.
Layers of Atmosphere
Troposphere: 0–11 km; movement of air, weather
Stratosphere: 11–50 km; ozone layer, absorbs and scatters UV rays
Mesosphere: 50–80 km; meteoroids burn up
Thermosphere: 80+ km; disturbances produce aurora borealis

7. Heat Transfer in the Troposphere
Lesson 15.1 Earth’s Atmosphere
Heat Transfer in the Troposphere
Radiation: The transfer of energy through space, such as heat from the sun to Earth’s atmosphere
Conduction: The transfer of heat directly between two objects that are in contact
Convection: The transfer of heat by the movement of currents within a fluid (liquid or gas)

8. Convection Currents Warm air is less dense than cool air.
Lesson 15.1 Earth’s Atmosphere
Convection Currents
Warm air is less dense than cool air.
When air near the surface heats up, it rises; as it rises, it cools and then sinks.
Rising and sinking fluids generate convection currents.
Cause wind and heat to move through the atmosphere

9. Lesson 15.1 Earth’s Atmosphere
Air Masses and Fronts
Air masses: Large bodies of air with similar properties
Fronts: Boundaries between air masses of different properties
Warm front
Boundary along which a mass of warmer, moister air pushes against a mass of cooler, drier air
Can produce light precipitation
Cold front
Boundary along which a mass of cooler, drier air pushes against a mass of warmer, moister air
Can produce heavy precipitation

10. Lesson 15.2 Pollution of the Atmosphere
Air pollution is estimated to cause 2 million premature deaths worldwide every year.

11. Sources of Air Pollution
Lesson 15.2 Biomes
Sources of Air Pollution
Natural processes: Windblown dust, particles in volcanic eruptions, smoke and soot from fire
Human sources: Most come directly or indirectly from the burning of fossil fuels.
Did You Know? Humans can increase the hazards of natural air pollution. For example, by removing trees, humans expose soil, which can dry out and add to huge dust storms when picked up by wind.
Dust storm approaching a U.S. farm during the 1930s

12. Types of Air Pollutants
Lesson 15.2 Pollution of the Atmosphere
Types of Air Pollutants
Primary air pollutants: Released directly into the atmosphere; example: soot
Secondary air pollutants: Formed when primary pollutants react chemically with other substances; example: sulfuric acid

13. How Air Pollutants Affect Your Health
Lesson 15.2 Pollution of the Atmosphere
How Air Pollutants Affect Your Health
Lung irritation and respiratory illnesses, such as asthma
Carbon monoxide interferes with body’s ability to use oxygen.
Trace amounts of some air pollutants, such as benzene or soot, may contribute to cancer.

14. Smog A mix of air pollutants that forms over cities
Lesson 15.2 Pollution of the Atmosphere
Smog
A mix of air pollutants that forms over cities
“Smog” is a combination of the words smoke and fog.
Industrial smog (soot, sulfur, and water vapor) comes from industrial sources.
Photochemical smog is mostly tropospheric ozone created when primary pollutants from vehicle exhaust react to sunlight.

15. Temperature Inversions
Lesson 15.2 Pollution of the Atmosphere
Temperature Inversions
Did You Know? A thermal inversion caused London’s “killer smog.”
Normally, air near Earth’s surface warms and rises, carrying pollutants with it.
When a layer of warmer air sits over a layer of cooler air, it traps pollution near Earth’s surface.

16. Lesson 15.2 Pollution of the Atmosphere
Acid Deposition
Sulfur dioxide and nitrogen oxides can react with water, oxygen, and other chemicals to form acids.
Acid falls as particles or dissolves in precipitation, lowering the pH of rain and snow.
Acid deposition harms forest and lakes and damages human structures.
Did You Know? Rainwater is naturally acidic (pH 5.6), but acid precipitation in some parts of the U.S. has a pH as low as 4.

17. Lesson 15.3 Controlling Air Pollution
Since the Clean Air Act was first enacted in 1963, emissions of the worst pollutants in the U.S. have decreased by 57%.

18. Lesson 15.3 Controlling Air Pollution
The Clean Air Act
First passed in 1963 to protect human and environmental health by improving air quality; has been revised several times
Limits emissions of pollutants, sets standards for air quality, establishes a legal framework for suing industries that break the rules, and provides funding for pollution control

19. Major Accomplishments of the Clean Air Act
Lesson 15.3 Controlling Air Pollution
Major Accomplishments of the Clean Air Act
Catalytic converters, present in all cars since 1975, have reduced vehicle emissions.
Lead has been phased out of gasoline.
Industries and power plants have reduced releases of pollutants by using scrubbers, which remove or alter chemicals before they leave factory smokestacks.
Did You Know? The removal of lead from gasoline has led to a 99% reduction in lead emissions since 1973.

20. Lesson 15.3 Controlling Air Pollution
The Ozone Hole
Ozone is a pollutant in the troposphere, but in the stratosphere it creates a protective barrier against UV radiation.
Chemicals called chlorofluorocarbons, which used to be found in everything from aerosol cans to refrigerators, have destroyed ozone, causing an “ozone hole” to form over Antarctica.
An ozone hole allows more UV radiation to reach Earth’s surface, potentially increasing cases of skin cancer.
Aerosol spray can

21. Recovery of the Ozone Layer
Lesson 15.3 Controlling Air Pollution
Recovery of the Ozone Layer
The Montreal Protocol is an international treaty signed in 1987 that has cut CFC production by 95% since the 1980s.
Ozone levels in the stratosphere have begun to stabilize, and the ozone hole will likely start to disappear.
Ozone Hole 1979
Ozone Hole 2000