Outdoor Air Pollution Key Concepts Structure and Composition of the Atmosphere Types and Sources of Outdoor Air Pollution Types Formation and Effects of Smog Sources and Effects of by HC111111091228


									Outdoor Air Pollution
             Key Concepts
Structure and Composition of the Atmosphere
Types and Sources of Outdoor Air Pollution
Types, Formation and Effects of Smog
Sources and Effects of Acid Deposition
Effects of Air Pollution
Types and Sources of Indoor Air Pollution
Prevention and Control of Air Pollution
        Structure of the Atmosphere
 The atmosphere is divided into five
  layers. It is thickest near the surface
  and thins out with height until it
  eventually merges with space.

 1) The troposphere is the first layer
  above the surface and contains half
  of the Earth's atmosphere. Weather
  occurs in this layer.
 2) Many jet aircrafts fly in the
  stratosphere because it is very stable.
  Also, the ozone layer absorbs
  harmful rays from the Sun.
 3) Meteors or rock fragments burn
  up in the mesosphere.
  4) The thermosphere is a layer with
  auroras. It is also where the space
  shuttle orbits.
 5) The atmosphere merges into space
  in the extremely thin exosphere. This
  is the upper limit of our atmosphere.
Contains 75 – 80% of Earth’s Air
Layer closest to Earth’s surface
The layer of the atmosphere involved
 in the cycling of Earth’s vital nutrients
Largely responsible for the planet’s
 short- term weather and long-term
Contains the Ozone Layer
  Stratospheric ozone is produced when some oxygen
   molecules interact with ultraviolet radiation of the Sun
        (3 O2 + UV        2 O 3)
  The “global sunscreen” of ozone keeps approximately 95% of
   the Sun’s harmful UV rays from reaching Earth’s surface. This
   “good ozone” allows us and other life forms to live on planet
Earth protecting us from sunburn, skin and eye cancer,
   cataracts, and damage to our immune systems.
 “Bad ozone” is found in the troposphere – especially in urban
       Outdoor Air Pollution
                       CO       CO2
Primary Pollutants                               Secondary Pollutants
                     SO2     NO       NO2
                   Most hydrocarbons
                                                   HNO3        H2SO4
                     Most suspended
                        particles                H2O2     O3     PANs
                                            Most NO3– and SO4 2 –salts


Major Classes of Air Pollutants

Class                                    Examples
Carbon oxides                            Carbon monoxide (CO) and carbon dioxide (CO2)

Sulfur oxides                            Sulfur dioxide (SO2) and sulfur trioxide (SO3)
                                         Nitric oxide (NO), nitrogen dioxide (NO2), nitrous
Nitrogen oxides                          oxide (N2O) (NO and NO2 often are lumped together
                                         and labeled NOx)
Volatile organic compounds (VOCs) Methane (CH4), propane (C3H8),
                                         chlorofluorocarbons (CFCs)
Suspended particulate matter (SPM) Solid particles (dust, soot, asbestos, lead, nitrate, and
                                         sulfate salts), liquid droplets (sulfuric acid, PCBs,
                                         dioxins, and pesticides)
Photochemical oxidants
                                         Ozone (O3), peroxyacyl nitrates (PANs), hydrogen
                                         (H2O2), aldehydes
Radioactive substances
                                         Radon-222, iodine-131, strontium-90, plutonium-239
                                         (Table 3-1, p. 49)

Hazardous air pollutants (HAPs),
                                         Carbon tetrachloride (CCl4), methyl chloride
which cause health effects such as       (CH3Cl), chloroform (CHCl3), benzene (C6H6),
cancer, birth defects, and nervous       ethylene dibromide (C2H2Br2), formaldehyde
system problems                          (CH2O2)
Major Outdoor Air Pollutants

Description: Colorless, odorless gas that is poisonous to air-breathing
animals; forms during the incomplete combustion of carbon-containing
fuels (2 C + O2      2 CO).
Major human sources: Cigarette smoking (p. 409), incomplete
burning of fossil fuels. About 77% (95% in cities)comes from motor vehicle
Health effects: Reacts with hemoglobin in red blood cells and reduces the
ability of blood to bring oxygen to body cells and tissues. This impairs
perception and thinking; slows reflexes; causes headaches, drowsiness,
dizziness, and nausea; can trigger heart attacks and angina; damages the
development of fetuses and young children; and aggravates chronic
bronchitis, emphysema, and anemia. At high levels it causes collapse,
coma, irreversible brain cell damage, and death.
Major Outdoor Air Pollutants
NITROGEN DIOXIDE (NO2)    Table 20-2
                           Page 438 be converted to nitric
Description: Reddish-brown irritating gas that gives photochemical
smog its brownish color; in the atmosphere can
acid (HNO3), a major component of acid deposition.
Major human sources: Fossil fuel burning in motor vehicles (49%) and
power and industrial plants (49%).
Health effects: Lung irritation and damage; aggravates asthma and
chronic bronchitis; increases susceptibility to respiratory infections
such as the flu and common colds (especially in young children and
older adults).
Environmental effects: Reduces visibility; acid deposition of HNO3 can
damage trees, soils, and aquatic life in lakes.
Property damage: HNO3 can corrode metals and eat away stone on
buildings, statues, and monuments; NO2 can damage fabrics.
Major Outdoor Air Pollutants
SULFUR DIOXIDE (SO2)            Table 20-2
                                 Page 438
Description: Colorless, irritating; forms mostly from the combustion of sulfur
containing fossil fuels such as coal and oil (S + O2    SO2); in the atmosphere
can be converted to sulfuric acid (H2SO4), a major component of acid deposition.
Major human sources: Coal burning in power plants (88%) and industrial processes
Health effects: Breathing problems for healthy people; restriction of airways in people
with asthma; chronic exposure can cause a permanent condition similar to bronchitis.
According to the WHO, at least 625 million people are exposed to unsafe levels of
sulfur dioxide from fossil fuel burning.
Environmental effects: Reduces visibility; acid deposition of H2SO4 can damage trees,
soils, and aquatic life in lakes.
Property damage: SO2 and H2SO4 can corrode metals and eat away stone on
buildings, statues, and monuments; SO2 can damage paint, paper, and leather.
Major Outdoor Air Pollutants

Description: Variety of particles and droplets (aerosols) small and light enough to
remain suspended in atmosphere for short periods (large particles) to long periods
(small particles; Figure 20-6, p. 441); cause smoke, dust, and haze.
Major human sources: Burning coal in power and industrial plants (40%), burning diesel
and other fuels in vehicles (17%), agriculture (plowing, burning off fields), unpaved
roads, construction.
Health effects: Nose and throat irritation, lung damage, and bronchitis; aggravates
bronchitis and asthma; shortens life; toxic particulates (such as lead, cadmium, PCBs,
and dioxins) can cause mutations, reproductive problems, cancer.
Environmental effects: Reduces visibility; acid deposition of H2SO4 droplets can
damage trees, soils, and aquatic life in lakes.
Property damage: Corrodes metal; soils and discolors buildings, clothes, fabrics, and
Major Outdoor Air Pollutants
                              Table 20-2
                                Page with an unpleasant odor that forms in the
Description: Highly reactive, irritating gas
troposphere as a major component of photochemical smog (Figures 20-3 and 20-5).

Major human sources: Chemical reaction with volatile organic compounds (VOCs,
emitted mostly by cars and industries) and nitrogen oxides to form photochemical
smog (Figure 20-5).

Health effects: Breathing problems; coughing; eye, nose, and throat irritation;
aggravates chronic diseases such as asthma, bronchitis, emphysema, and heart
disease; reduces resistance to colds and pneumonia; may speed up lung tissue

Environmental effects: Ozone can damage plants and trees; smog can reduce

Property damage: Damages rubber, fabrics, and paints.
Major Outdoor Air Pollutants
                          Table 20-2
                          Page 438
Description: Solid toxic metal and its compounds, emitted into the
atmosphere as particulate matter.

Major human sources: Paint old houses), smelters (metal refineries), lead
manufacture, storage batteries, leaded gasoline (being phased out in
developed countries).

Health effects: Accumulates in the body; brain and other nervous system
damage and mental retardation (especially in children); digestive and other
health problems; some lead-containing chemicals cause cancer in test

Environmental effects: Can harm wildlife.
 Carbon Dioxide as a Pollutant
1. In high enough concentrations any
   chemical in the air can become a pollutant.
2. We have been increasing the CO2 in the
   troposphere by burning fossil fuels and
   clearing CO2 absorbing trees faster than
   they can grow back.
3. The troposphere is warming and the
   evidence points to the additional CO2
   added as a result of human activities.
           Photochemical Smog
 Photochemical smog is a
  mixture of air pollutants
  formed by the reaction of
  nitrogen oxides and volatile
  organic hydrocarbons when
  they are exposed to sunlight.

 More than 100 primary and
  secondary pollutants can be
           Photochemical Smog

                              ground level ozone (O3)
                              + other photochemical
VOC + NOx + heat + sunlight       oxidants
                              + aldehydes
                              + other secondary air
       Temperature Inversions
During daylight hours, the sun warms the ground which
warms the air near the Earth’s surface. The warm air
rises as more dense cool air displaces it. Any pollution
in the air normally disperses in the turbulence caused
by the mixing of the air. When a layer of cool air traps
the layer of warm air near the Earth’s surface, then the
situation is known as a temperature inversion. In this
case, pollutants are not dispersed but continue to build
up in the still, stagnant air.
Temperature Inversions

  Subsidence Inversion
                                                Los Angeles
                                                            Descending warm air mass

                                                                 Inversion layer
Increasing altitude

                                               Sea breeze


                      Decreasing temperature

                       Sea breezes keep the air and pollution onshore,
                       and the mountains prevent the air from
                       escaping. The cold air aloft acts as a lid.
         Photochemical Smog
Brown Air Smog

               Smog Disasters
 Meuse Valley, Belgium, 1930   6000 people ill, 63 deaths
                                     in a few days
 Donora, Pennsylvania, 1948    6000 people ill, 20 deaths
                                 in three days
 Poza Rica, Mexico, 1950       22 dead & 320 hospitalized
                                in 25 minutes

 London, England, 1952         4,000 dead in three days

 London 1956, 56, 62           2500 deaths attributed to coal
                                   smoke (smog)

 New York, New York, 1953,     In 1962, increased to 269
        1962-1963, 1966         due to photochemical smog
                 Industrial Smog


Sulfur Dioxide

Sulfuric Acid

Gray Air Smog
Emission Reduction
Regional Outdoor Air Pollution from Acid

 Wet Acid Deposition   Dry Acid Deposition
 In the United States, coal burning
  power and industrial plants in the Ohio
  Valley emit the largest quantities of
  sulfur dioxide and other pollutants that
  can cause acid deposition.

 The typical precipitation in the Eastern
  United States has a pH of 4 – 4.8.
  More than 10 times the natural
  precipitation with a pH of 5.6.
Acid Deposition in the US
 Acid Deposition - Plants, and Soil

Nutrient Leaching

Heavy Metal Release

 Weakens Trees

                    Fig. 20-11 p. 447

                                           Acid Deposition
  Acid     SO2  NOX
deposition H2O2  O3
          PANs Others
                                                          to drought,
        Direct damage                      Reduced        extreme cold,
        to leaves and bark                 photosyn       insects,
                                           thesis         mosses,
                                           and            and disease
                                           growth         organisms

                      Soil acidification                              Tree death

                                                 Root     Reduced nutrient
          Leaching                Release of
                         Acid     toxic          damage   and water uptake
          Soil                    metal
          nutrients               icons

Acid Deposition and Aquatic Systems

Fish Declines
        Aluminum Toxicity

                  Acid Shock
Potential problem areas
because of sensitive soils

Potential problem areas because
of air pollution: emissions leading
to acid deposition
Current problem areas
(including lakes and rivers)
                           Acid Deposition
                  Prevention              Cleanup

Reduce air pollution by                   Add lime to neutralize
improving energy efficiency               acidified lakes

Reduce coal use                           Add phosphate
                                          fertilizer to neutralize
                                          acidified lakes
Increase natural gas use

Increase use of
renewable resources

Burn low-sulfur coal

Remove SO2 particulates,
and Nox from smokestack gases

Remove Nox from motor
vehicular exhaust

Tax emissions of SO2
    Acid Deposition and Humans
Respiratory Diseases
Toxic Metal Leaching
Damage to structures especially
 containing calcium carbonate
Decreased Visibility
Decreased Productivity and profitability
of fisheries, forests and farms
Nasal cavity

Oral cavity

Pharynx (throat)

Trachea (windpipe)

Bronchus                Cancer
Right lung
        Stationery Source Air Pollution

    Prevention            Dispersion or

Burn low-sulfur                Disperse
coal                           emissions above
                               thermal inversion
Remove sulfur
                               layer with tall
from coal
Convert coal
to a liquid or                 Remove
 gaseous fuel                  pollutants after
Shift to less                  Tax each unit
polluting fuels                of pollution
       Cleaned gas

Dust discharge
                       Dirty gas
Electrostatic Precipitator

     Cleaned gas

     Dirty gas

Baghouse Filter    Dust discharge
      Cleaned gas

      Dirty gas

Cyclone Separator   Dust discharge
    Cleaned gas                    Dirty gas



            Dirty water
Wet Scrubber - Remove 98% of SO2 and particulate matter
                     Motor Vehicle Pollutions
                 Prevention                Cleanup
          Mass transit
   Bicycles and walking                  Emission control
    Less polluting engines
                                           Improve fuel efficiency
       Less polluting fuels
                                         Car exhaust
Get older, polluting                     Inspections
cars off the road                        twice a year

 Give buyers tax write-
 offs for buying low-                             emission
 polluting, energy-
 efficient vehicles     Restrict driving in
                        polluted areas
                            Air Pollution
                   Prevention                Cleanup

Improve energy efficiency                   Reduce poverty
to reduce fossil fuel use

Rely more on lower-                         Distribute cheap and efficient
polluting natural gas                       cookstoves to poor families in
                                            developing countries

Rely more on renewable
energy (especially solar
cells, wind, and solar-                     Reduce or ban indoor smoking
produced hydrogen)

Transfer technologies for                   Develop simple and cheap
latest energy efficiency,                   test for indoor pollutants
renewable energy, and
pollution prevention to                     such as particulates, radon,
developing countries.                       and formaldehyde
   How Can Laws Be Improved?
 Rely on pollution prevention rather than cleanup.
 Force Congress to increase fuel efficiency
 standards for cars, SUVs and light trucks.
 Regulate the emissions from inefficient 2 cycle
 engines (lawnmowers, leaf blowers, jet skis, outboard motors, etc)
 Regulate pollution from oceangoing ships in
 American ports.
 Amend the Clean Air Laws to deal with emissions
 of carbon dioxide and other greenhouse gases.
 Better enforce the Clean Air Acts

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