Transcript Chapter 12: Air

Chapter 12: Air
Section 1: What Causes Air Pollution
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Clean air consists mostly of
nitrogen and oxygen gas as well
as very small amounts of argon,
carbon dioxide, and water vapor.
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When harmful substances build up
in the air to unhealthy levels, the
result is air pollution.
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Most air pollution is the result of
human activity.
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Some does come from natural
sources such as volcanic
eruptions.
Primary and Secondary Pollutants
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A pollutant that is put directly into
the air by human activity is called
a primary pollutant. Soot from
smoke is an example.
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Secondary pollutants form when
primary pollutants react with other
primary pollutants or with
naturally occurring substances
such as water vapor. Ground
level ozone is an example. This
happens when UV rays cause
emissions from vehicles to react
with oxygen in the atmosphere.
Sources of Primary Air Pollution
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Household products, power plants, and
motor vehicles are sources of primary air
pollutants such as carbon monoxide,
nitrogen oxide, sulfur dioxide, and chemicals
called volatile organic compounds (VOCs).
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Carbon monoxide is an important
component in the exhaust from vehicles.
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Nitrogen oxides come from vehicles and
coal burning power plants.
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Sulfur dioxide forms when coal and oil are
burned. Power plants, refineries, and metal
smelting are contributors as well.
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Most VOCs are from vehicles and gas
station spillage
The History of Air Pollution
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The problem is not new :(
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2,000 years ago, Seneca, a
Roman philosopher, complained
about the foul air in Rome.
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In 1273, King Edward I ordered
the burning of sea coal illegal.
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Air quality is worse today because
of industrial societies burn large
amounts of fossil fuels.
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Most air pollution comes from
motor vehicles and industry.
Motor Vehicle Emissions
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Almost 1/3 of our air pollution
from gasoline burned by vehicles.
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In 1998 Americans drove over 2.6
trillion miles and 90% of that was
passenger vehicles.
Controlling Vehicle Emissions
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The Clean Air Act, passed in 1970,
gives the EPA the authority to
regulate vehicle emissions in the U.S.
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The EPA called for the gradual
elimination of lead in gasoline. As a
result, lead pollution has been
reduced by more than 90%.
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Catalytic converters, which are now
required, clean exhaust gases of
pollutants before the pollutants are
able to escape the tailpipe.
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Cars today burn fuel 35% more
efficiently and with 95% fewer
emissions.
California Zero Emission Vehicle Program
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In California, vehicle emissions account for
more than half of the ozone and particulate
matter that pollutes the air.
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In 1990, the state's Air Resource Board
established the Zero Emission Vehicle
(ZEV) program.
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Battery powered vehicles are the only true
ZEVs at the moment.
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There are two types of partial ZEVs.
Hybrids which are powered by both battery
and gasoline and methanol fuel cell cars
(which are still developmental prototypes).
Industrial Air Pollution
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Many industries and power plants
burn fossil fuels to produce energy.
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Burning fossil fuels releases sulfur
dioxide and nitrogen oxides into the
air.
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Power plants emit at least 2/3 of all
sulfur dioxide and more than 1/3 of all
nitrogen oxides that pollute the air.
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Dry cleaning also produces VOCs as
do oil refineries, chemical
manufacturing plants, furniture
refinished, and automobile repair
shops.
Regulating Air Pollution from Industry
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The Clean Air Act requires many industries to use
scrubbers to remove some of the more harmful
substances that would otherwise pollute the air.
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A scrubber is a machine that moves gases through
a spray of water to dissolve many pollutants.
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Electrostatic precipitators are used in cement
factories and coal burning power plants. Gas
containing dust particles are blown through an
electrically charged chamber causing the particles
to stick together and the sides of the chamber.
Clean gas is released and particle can be collected
and removed.
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Electrostatic precipitators remove 22 million metric
tons of ash every year.
Smog
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When air pollution hangs over
urban areas and reduces
visibility, it is called smog.
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Smog results from chemical
reactions that involve sunlight,
air, automobile exhaust, and
ozone.
Temperature Inversions
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The circulation of air in the atmosphere
usually keeps air pollution from reaching
dangerous levels.
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During the day, the sun heats the surface of
the Earth and air near the surface. Warm air
rises through the cooler air above it carrying
pollutants away from the ground.
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Sometimes pollution is trapped near the
Earth's surface. Usually air temperature
decreases with altitude, but sometimes a
temperature inversion occurs. When this
happens, the warmer air keeps the cooler
air at the surface from moving upward
trapping pollutants in the cooler air closer to
the surface.
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Cities in valleys have a greater chance of
this occurring.
Copy now, answer later :)
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Name five primary air pollutants, and give important
sources for each.
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Name the two major sources of air pollution in urban
areas.
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Describe the way in which smog forms.
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Define temperature inversion. Explain how temperature
inversion traps pollutants near Earth's surface.
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Should automobile manufacturers be made to adhere to
quotas of zero-emission vehicles set by states, even if
the quota causes automakers to lose revenue?