Ch 15 - -1 Earth`s Atmosphere 1. Properties of the Atmosphere a

Ch 15 - -1 Earth’s Atmosphere
1. Properties of the Atmosphere
a. Atmosphere – thin layer of gases that surround Earth
b. We live at the bottom where we are protected from
i. Harmful rays
ii. Incoming Meteors
iii. Extreme climate changes
2. Composition of the Atmosphere
a. Nitrogen
i. Makes up78% of air
ii. All organisms contain nitrogen
iii. Bacteria use it in ‘nitrogen fixation’
b. Oxygen
i. Makes up 21% of air
ii. Needed for life of most organisms
iii. Needed for combustion
c. Water - as a solid, liquid or gas (vapor)
3. Relative Humidity
a. The ratio of water vapor in air to the maximum amount the same air could contain at the same
temperature
b. Is affected by temperature and location; in general, warm air holds more water.
c. 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.
d. During the formation of clouds, water vapor condenses on tiny particles in the air, such as slat , smoke,
and dust
4. Temperature - varies all over the earth depending on angle of sun’s rays, and location, and time of year.
5. Air Pressure
a. The force exerted by air on the area below it
b. In general, air pressure decreases with altitude; 1000 mb sea level, 300mb Mt Everest
c. It can be measured using a barometer.
i. Mercury barometer pushes a level of mercury up
ii. Aneroid barometer has a metal chamber whose walls bend with pressure
6. Layers of the Atmosphere
a. Troposphere:
i. 0–11 km;
ii. movement of air,
iii. weather
iv. clouds
v. ¾ of mass of atmosphere
vi. Cooler with height until top
b. Stratosphere:
i. 11–50 km;
ii. ozone layer,
iii. absorbs and scatters UV rays
iv. Gases do not mix, so pollutants just hang there
v. Warmer than lower layers, but still very cold
c. Mesosphere:
i. 50–80 km;
ii. meteoroids burn up
d. Thermosphere:
i. 80+ km;
ii. disturbances produce aurora borealis (northern lights)
7. The Troposphere and Weather
a. Heat Transfer in the Troposphere
i. Radiation: The transfer of energy through space, such as heat from the sun to Earth’s
atmosphere
ii. Conduction: The transfer of heat directly between two objects that are in contact
iii. Convection: The transfer of heat by the movement of currents within a fluid (liquid or gas)
1. Warm air is less dense than cool air.
2. When air near the surface heats up, it rises; as it rises, it cools and then sinks.
3. Rising and sinking fluids generate convection currents.
4. Cause wind and heat to move through the atmosphere
b. Air Masses and Fronts
i. Air masses: Large bodies of air with similar properties
ii. Fronts: Boundaries between air masses of different properties
1. Warm front
a. Boundary along which a mass of warmer, moister
air pushes against a mass of cooler, drier air
b. Can produce light precipitation
2. Cold front
a. Boundary along which a mass of cooler, drier air pushes against a mass of
warmer, moister air
b. Can produce heavy precipitation
Homework Questions to Answer:
1. Think of a swimming pool with a shallow end and deep end. The pressure of water on the floor at the shallow
end is less than the pressure of water on the floor at the deep end. How is this similar to the way air pressure
differs at different altitudes?
2. Why is the temperature in the upper stratosphere higher than the temperature in the lower stratosphere?
3. How is a warm front different from a cold front?
4. Winds occur because of convection currents in the troposphere. How do you think wind affects air pollution?
Environmental Science Notes
Ch. 15.2 – Pollution of the Atmosphere
Fact: “Air pollution is estimated to cause 2 million premature deaths worldwide every year.”
1. Air Pollution: The release of damaging materials into the atmosphere
2. Emissions: the substances released; dust, smoke, soot, or gases such as sulfur dioxide and carbon
monoxide.
A. Sources of Air Pollution
1. Natural processes: Windblown dust, particles in volcanic eruptions, smoke and soot from fire
2. Human sources: Most come directly or indirectly from the burning of fossil fuels (carbon containing
fuels that formed from once-living things).
B. Types of Air Pollutants
1. Primary air pollutants: Released directly into the atmosphere; example: soot
2. Secondary air pollutants: Formed when primary pollutants react chemically with other substances;
example: sulfuric acid
C. How Air Pollutants Affect Your Health
1. Lung irritation and respiratory illnesses, such as asthma
2. Carbon monoxide interferes with body’s ability to use oxygen.
3. Trace amounts of some air pollutants, such as benzene or soot, may contribute to cancer.
D. Smog
1. A mix of air pollutants that forms over cities
2. “Smog” is a combination of the words smoke and fog.
3. Industrial smog (soot, sulfur, and water vapor) comes from industrial sources.
4. Photochemical smog is mostly tropospheric ozone created when primary pollutants from vehicle
exhaust react to sunlight.
E. Temperature Inversions
1. Normally, air near Earth’s surface warms and rises, carrying pollutants with it.
2. When a layer of warmer air sits over a layer of cooler air, it traps pollution near Earth’s surface.
F. Acid Depositon
1. Sulfur dioxide and nitrogen oxides can react with water, oxygen, and other chemicals to form acids.
2. Acid falls as particles or dissolves in precipitation, lowering the pH of rain and snow.
3. Acid deposition harms forests and lakes and damages human structures.
15.3 – Controlling Air Pollution
A. The Clean Air Act
1. What is the goal?
a. First passed in 1963 to protect human and environmental health by improving air quality
2. What does it do?
a. Limits emissions of pollutants,
b. sets standards for air quality,
c. establishes a legal framework for suing industries that break the rules,
d. provides funding for pollution control
B. Major Accomplishments of the Clean Air Act
1. Catalytic converters, present in all cars since 1975, have reduced vehicle emissions.
2. Lead has been phased out of gasoline.
3. Industries and power plants have reduced releases of pollutants by using scrubbers, which remove
or alter chemicals before they leave factory smokestacks.
C. The Ozone Hole
1. Ozone is a pollutant in the troposphere, but in the stratosphere it creates a protective barrier
against UV radiation.
2. 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.
3. An ozone hole allows more UV radiation to reach Earth’s surface, potentially increasing cases of skin
cancer.
4. The Montreal Protocol is an international treaty signed in 1987 that has cut CFC production by 95%
since the 1980s.
5. Ozone levels in the stratosphere have begun to stabilize, and the ozone hole will likely start to
disappear.
1979
2009
very little ozone
lots more ozone