Download Types of Air Pollution Control

Chapter 9
Lecture
Outline
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Learning Outcomes
After studying this chapter, you should be able to answer the following
questions:
• What or where is the stratosphere, and why do we care?
• Explain the greenhouse effect and how it is changing our climate.
• What is the ENSO cycle, and how does it affect weather
patterns?
• Is it too late to do anything about global climate change?
• Why has the United States refused to ratify the Kyoto Protocol?
• Why has stratospheric ozone been disappearing? Should we
worry about it?
• What are the main sources and effects of air pollution?
• Has world air quality been getting better or worse?
• What is the “new source review”?
9-2
Climate is an angry beast, and we
are poking it with sticks.
–Wallace Broecker
9-3
9.1 The Atmosphere Is a Complex System
• Clean, dry air is
– 78 percent nitrogen
– Almost 21 percent oxygen,
– The remaining 1 percent composed of argon, carbon
dioxide (CO2), and a variety of trace gases.
– Water vapor concentrations vary from near 0 to 4
percent, depending on air temperature and available
moisture.
• Minute particles and liquid droplets—collectively
called aerosols —also are suspended in the air.
• Atmospheric aerosols play important roles in the
earth’s energy budget and in rain production.
9-4
The Atmosphere
• Within the troposphere,
air circulates in great
vertical and horizontal
convection currents.
• The stratosphere has
almost no water vapor and
nearly 1,000 times more
ozone (O3).
9-5
The sun warms our world
9-6
The greenhouse effect
• Following the second law of thermodynamics,
absorbed energy is gradually reemitted as lowerquality heat energy.
• A brick building, for example, absorbs energy in
the form of light and reemits that energy in the
form of heat.
• This phenomenon is called the greenhouse effect
because the atmosphere, loosely comparable to
the glass of a greenhouse, transmits sunlight
while trapping heat inside.
9-7
Water stores heat, and
winds redistribute it
• Much of the incoming solar energy is used to
evaporate water.
• Every gram of evaporating water absorbs 580
calories of energy as it transforms from liquid to
gas.
• Globally, water vapor contains a huge amount of
stored energy, known as latent heat.
• When water vapor condenses, returning from a
gas to a liquid form, the 580 calories of heat
energy are released.
9-8
Ocean currents also modify our climate
9-9
9.2 Climate Can Be an Angry Beast
9-10
What causes catastrophic climatic swings?
• Milankovitch cycles
– Named after
Serbian scientist
Milutin
Milankovitch, who
first described them
in the 1920s.
– are periodic shifts
in the earth’s orbit
and tilt
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The El Niño/Southern Oscillation
can have far-reaching effects
9-12
9.3 Global Warming Is Happening
9-13
Greenhouse gases
have many sources
• The lowest emissions in the
world are in Chad, where
per capita production is
only one-thousandth that of
the United States.
• Some countries with high
standards of living release
relatively little CO2.
Sweden, for example,
produces only 6.5 tons per
person per year.
9-14
Evidence of climate change is
overwhelming
• Over the last century the average global temperature has
climbed about 0.6°C (1°F).
• Permafrost is melting; houses, roads, pipelines, sewage
systems, and transmission lines are being damaged as the
ground sinks beneath them.
• Arctic sea ice is only half as thick now as it was 30 years ago.
• Alpine glaciers everywhere are retreating rapidly .
– Mount Kilimanjaro has lost 85 percent of its famous ice cap since
1915.
• The higher levels of CO 2 being absorbed are acidifying the
oceans, and could have adverse effects on sea life.
9-15
Evidence continued…
• Sea level has risen worldwide approximately 15–20 cm (6–8
in.) in the past century.
• Satellite images and surface measurements show that
growing seasons are now as much as three weeks longer in a
band across northern Eurasia and North America than they
were 30 years ago.
• Droughts are becoming more frequent and widespread.
• Biologists report that many animals are breeding earlier or
extending their range into new territory as the climate
changes.
• Coral reefs worldwide are “bleaching,” losing key algae and
resident organisms,
9-16
The Stern review recommends four key
elements for combating climate change.
• Emissions trading to promote
• cost-effective emissions reductions.
• Technology sharing that would double research
investment in clean energy technology and
accelerate spread of that technology to developing
countries.
• Reduce deforestation, which is a quick and highly
cost-effective way to reduce emissions.
• Help poorer countries by honoring pledges for
development assistance to adapt to climate change.
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9.4 The Kyoto Protocol Attempts to
Slow Climate Change
• the Kyoto Protocol , this treaty sets different
limits for individual nations, depending on
their output before 1990.
• At a Kyoto follow-up meeting held in Bali in
2007, the United States finally acquiesced to
global pressure and signed an action plan that
commits all developed countries to adopt
mitigation plans.
9-18
There are many ways we can
control greenhouse emissions
• Double the fuel economy for 2 billion cars from 30 to 60 mpg.
• Cut average annual travel per car from 10,000 to 5,000 miles.
• Improve efficiency in heating, cooling, lighting, and appliances
by 25 percent.
• Update all building insulation, windows, and weather
stripping to modern standards.
• Boost efficiency of all coal-fired power plants from 32 percent
today to 60 percent (through co-generation of steam and
electricity).
• Replace 800 large coal-fired power plants with an equal
amount of gas-fired power (four times current capacity).
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9.5 Air Pollution
9-20
Indoor air can be more dangerous
than outdoor air
9-21
9.6 Interactions Between Climate
Processes and Air Pollution
• Air pollutants can travel far
• Dust and fine aerosols can be carried great
distances by the wind.
• Pollution from the industrial belt between the
Great Lakes and the Ohio River Valley regularly
contaminates the Canadian Maritime
Provinces and sometimes can be traced as far
as Ireland.
9-22
Stratospheric ozone is declining
9-23
9.7 Effects of Air Pollution
• Polluted air is unhealthy
– Consequences of breathing dirty air include increased
probability of heart attacks, respiratory diseases, and lung
cancer.
• Plants are sensitive to pollutants
– In the early days of industrialization, fumes from furnaces,
smelters, refineries, and chemical plants often destroyed
vegetation and created desolate, barren landscapes
around mining and manufacturing centers.
• Synergistic effects in which the injury caused by exposure to
two factors together is more than the sum of exposure to each
factor individually.
9-24
Effects continued…
• Smog and haze reduce visibility
– Grand Canyon National Park, where maximum visibility
used to be 300 km (185 mi), is now so smoggy on some
days visibility is only 20 km (12.5 mi) across the canyon.
• Acid deposition has many effects
– Acid precipitation, the deposition of wet, acidic solutions
or dry, acidic particles from the air, became widely
recognized as a pollution problem only in the last 20 years.
– The most notable aquatic effects of acid deposition are the
reduction of trout, salmon, and other game fish, whose
eggs and fry die below pH 5.
– Forest damage: On Mount Mitchell in North Carolina,
nearly all the trees above 2,000 m (6,000 ft) are losing
needles, and about half are dead.
9-25
Forest damage by acid rain
9-26
9.8 Air Pollution Control
• Particulate removal involves filtering air emissions.
Filters trap particulates in a mesh or electrostatic
precipitators are used.
• Sulfur removal is important because sulfur oxides
are among the most damaging of all air pollutants in
terms of human health.
• Nitrogen oxides (NOx) can be reduced in both
internal combustion engines and industrial boilers.
• Hydrocarbon controls mainly involve complete
combustion or the control of evaporation.
9-27
Types of Air Pollution Control
• Electrostatic
precipitators are the
most common
particulate controls in
power plants.
9-28
Clean air legislation is controversial
• The Clean Air Act of 1963 was the first national
legislation in the United States aimed at air pollution
control.
• In 1970, an extensive set of amendments essentially
rewrote the Clean Air Act.
• A 2002 report concluded that simply by enforcing
existing clean air legislation, the United States could
save at least another 6,000 lives per year and
prevent 140,000 asthma attacks.
9-29
9.9 Current Conditions and Future
Prospects
• Although the United States has not yet
achieved the Clean Air Act goals in many parts
of the country, air quality has improved
dramatically.
• The outlook is not so encouraging in other
parts of the world.
9-30
There are signs of hope
9-31
Practice Quiz
1. What are the “stabilization wedges” suggested by Pacala and
Socolow at Princeton University (see table 9.2)? How many
wedges do we need to accomplish to flatten our CO2 emissions?
2. What is the greenhouse effect, and how does it work?
3. Why are we worried about greenhouse gases?
4. What is the thermohaline ocean conveyor and what is
happening to it?
5. Describe the El Niño/Southern Oscillation.
9-32
Practice Quiz continued…
6. What gas, action, and country make the largest contribution to
global warming?
7. What has been the greatest air pollution control success in the
United States since 1970?
8. Define primary air pollutant, secondary air pollutant,
photochemical oxidant, point source, and fugitive emissions.
9. What is destroying stratospheric ozone, and where does this
happen?
10. What is the “new source review”?
9-33