Atmosphere

1
Atmosphere
Troposphere
17 kilometers (11 miles) in altitude - half that
over the poles
Composition
- 78 nitrogen - 21 oxygen -Water vapor, Argon,
Carbon dioxide, Trace amounts of other gases.
2
Stratosphere

• 17 - 48 km (11 - 30 miles)

• Much less water vapor
• Higher ozone concentration

- Acts a global sunscreen
Mesosphere
Thermosphere
3
Air Pollution
1. Causes harm to us, other forms of life, and
materials.
2. Alters climate
Major classes of Air Pollutants - Page 420
4

• Primary pollutants - emitted directly into
  troposphere

• Secondary pollutants - result from primary
  pollutants interacting with each other or other
  components of the atmosphere.

• Natural sources
• 1. Dust and other particulates - windstorms
• 2. Sulfur oxides - volcanoes
• 3. Carbon oxides, nitrogen oxides - forest fires
• 4. Hydrocarbons and pollens - plants
• 5. Methane, Hydrogen sulfide - decaying plants
• 6. Salt particles - sea

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Page 421
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Photochemical Smog
Mixture of primary and secondary pollutants
formed under the influence of sunlight
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Chemical Reactions resulting in Photochemical Smog
N2 O2 2NO
During Combustion
In the troposphere
2NO O2 2NO2 (nitrogen dioxide)
3NO2 H2O 2HNO3 NO (nitric acid)
NO2 UV radiation NO O
O2 O O3 (photochemical ozone)
Hydrocarbons O2 NO PANs (peroxyacyl
nitrates)
O O3 Hydrocarbons aldehydes
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Figure 17-7 (1)Page 425
40
Nitric oxide
Nitrogen dioxide
Ozone
30
20
Parts per million
10
0
6
7
8
9
10
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12
1
2
3
4
5
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7
8
A.M.
Noon
P.M.
Time
11
Industrial Smog
Results from burning of coal and heavy oil

1. Sulfur dioxide
2. Droplets of sulfuric acid
3. Variety of suspended particles and droplets

12
Acid Deposition
Mixture of wet secondary pollutants with a pH of
less than 5.6, and dry acidic particles, that
fall on the surface of the earth.
Wet deposits occurs 4 - 14 days after being
expelled by the source.
Dry deposition occurs usually within 2 - 4 days
of expulsion.
13
pH
- the negative logarithm of the H ion
concentration (see handout)
17-10
14
17-11
15
17-15
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Acid Deposition Effects Pages 430 - 431
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Chemistry of Industrial Smog
C O2 CO2 carbon dioxide
2C O2 2CO carbon monoxide
S O2 SO2 sulfur dioxide
2SO2 O2 2SO3 sulfur trioxide
SO3 H2O H2SO4 Sulfuric acid
2NH3 H2SO4 (NH4)2SO4 ammonium
sulfate