Transcript Atmospheric Pollution

Atmospheric Pollution
Outline
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Our Atmosphere
Natural Sources
Human-Caused Air Pollution
Climate and Topography
Effects of Air Pollution
Air Pollution Control
Clean Air Legislation
Current Conditions and Future Prospects
What is the Atmosphere
• Thin outer shell of the earth
• Made up of gases, often transparent
• Essential to life on earth for several reasons
• Provides oxygen
• Provides carbon dioxide for photosynthesis
• Moves thermal energy from equatorial regions to
polar regions
• Greenhouse effects
• Shields life from the sun’s harmful ultraviolet rays
If the Earth Was an Apple
• If the earth was an
apple, the atmosphere
would be no thicker
than the apple’s skin
• Our vital air supply is
not that thick
Atmosphere Characteristics
• The atmosphere is made up of four
main characteristics
1. The atmosphere is fluid
2. It is made up of various gases
3. It has mass
4. It consists of layers
Atmosphere
composition
Layers of the atmosphere
Atmospheric Pollution
• first became a problem with
the industrial revolution
– Coal burning created very dirty
air.
• Both natural and
anthropogenic sources for
pollution
– most pollution comes from
humans.
AIR POLLUTION
• We expect clean air yet we expel a variety of
wastes into the atmosphere
• Already seriously damaged the quality of air in
many parts of the earth
• Results - damage to health of vegetation, animal
life, and people
• air pollution is the most difficult type to contain
Air Pollution
• Worldwide air pollution causes
– premature deaths
– aggravates respiratory diseases
– damages crops, trees, building and other
objects
Effects of Pollution on Health and Well-Being
Major types of Air Pollution
1. Carbon oxides
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Carbon monoxide (CO), Carbon Dioxide (CO2)
2. Nitrogen Oxides
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Nitric oxide (NO), Nitrogen dioxide (NO2),
Nitrous oxide (N2O)
3. Sulfur oxides
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Sulfur dioxide (SO2), Sulfur trioxide (SO3)
Carbon Monoxide
• Impacts: Blood
– oxygen levels
– Headaches,
alertness, death
• Sources: Vehicles
(plus others)
Source: Ref. (1)
Nitrogen Oxides
• Excess nitrogen causing
fertilization and
eutrophication of inland
waters and coastal seas.
• Contributes to acid rain and
ground level ozone
• Humans responsible for
60% of emissions.
– Impacts: Respiratory
irritant (NO2)
– Leads to ozone
formation
– Leads to acidic
deposition of HNO3
Sulfur Dioxide
• Impacts:
– Eye and lung irritation (but seldom >
standard)
– Acidic deposition of H2SO4.
– Damage to limestone and concrete.
Source: Ref. (1)
Major Types of Air Pollution
4. Volatile organic compounds – hydrocarbons
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Methane, butane, ethylene, benzene
benzopyrene
5. Suspended particulate matter
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Dust, soot, asbestos, lead, cadmium,
chromium, arsenic, beryllium, nitrate and
sulfate salt.
Others include: Liquid droplets such as
sulfuric acid and oil, and Photochemical
oxidants such as ozone and formaldehyde
Particulate Matter
Source: Ref. (2)
Figure 3.10
Comparison of different greenhouse gases
CO2
Concentration
ppm
Preindustrial (<1800) 280
Current
370
CH4
CFC-11
CFC-12
N2O
ppm
0.8
1.74
ppt
0
268
ppt
0
484
ppb
288
314
Sources of Air Pollution
 Most are from humans:
 Burning of fossil fuels such as gas, oil, coal
and wood
 Emissions from cars, trucks and other motor
vehicles and machinery
 Emissions from industrial manufacturing and
processing plants
 Burning of agricultural and forestry materials
Natural Sources of Air Pollution
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Volcanoes - Ash and acidic components
Sea Spray - Sulfur
Vegetation - Volatile organic compounds
Pollen, spores, viruses, bacteria
Dust storms
Bacterial metabolism is responsible for 2/3 of
methane in the air.
• Forest fires
Spatial scales of Pollution
• The effects of pollution can be:
– Global
• Global Warming
• Ozone hole
– Regional
• Acid rain
– Local
• Smog
Formation of Ozone
• Oxygen that we breathe (and plants
produce) is O2
• UV radiation breaks down O2 into 2 O.
• O bonds with other O2 to give O3.
• See page 476 of textbook
Ozone hole
• Breakdown of ozone
– CFC’s are broken down by strong ultraviolet radiation
to create chlorine atoms.
– Cl destroys O3 molecules.
– Chlorine is not consumed by the reaction.
– One Cl atom can destroy 100,000 O3 molecules.
*See page 477 of the textbook for reactions
Ozone Hole Over Antarctic
Effects of Air Pollution
• Human Health
– WHO estimates each year 5-6 million people die
prematurely from illnesses related to air pollution.
• Likelihood of suffering ill health is related to intensity and
duration of exposure.
– As much as a 5 to 10 year decrease in life expectancy if you
live in worst parts of Los Angeles
Effects of Air Pollution
• PM2.5 - particulates less than 2.5 micron in
diameter are particularly risky and have been
linked with heart attack, asthma, lung cancer
and abnormal fetal development.
• New rules will remove particulates from diesel
engines and power plants.
• Most air pollutants are inhaled, but some can be
directly absorbed through the skin or ingested in
food and water.
Human Health
• Bronchitis
– Persistent inflammation of airways in the lung that
causes mucus build-up and muscle spasms
constricting airways.
• Can lead to emphysema - irreversible chronic obstructive
lung disease in which airways become permanently
constricted and alveoli are damaged or destroyed.
• In the U.S. half of all lungs examined at autopsy show
alveolar deterioration.
Soybean Leaves Damaged by
Sulfur Dioxide
Acid Deposition
• Acid precipitation - deposition of wet acidic
solutions or dry acidic particles from the air
– Unpolluted rain generally has pH of 5.6.
• Carbonic acid from atmospheric CO2
– H2SO4 and HNO3 from industrial and automobile
emissions are cause of acid precipitation.
– Aquatic effects are severe, as pH of 5 in freshwater
lakes disrupts animal reproduction and kills plants,
insects and invertebrates. Below pH 5, adult fish die.
Air Pollution Control
• Reducing Production
– Particulate Removal
• Remove particles physically by trapping them in a porous
mesh which allows air to pass through but holds back solids.
• Electrostatic Precipitators - fly ash particles pick up
electrostatic charge as they pass between large electrodes in
waste stream, and accumulate on collecting plate
Air Pollution Control
– Sulfur Removal
• Switch from soft coal with a high sulfur content to low sulfur
coal.
• Change to another fuel (natural gas).
– Nitrogen Oxides
• Best method is to prevent creation
– Staged Burners
– Selective Catalysts
– Hydrocarbon Control
• Use closed systems to prevent escape of fugitive emissions.