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SMOG. And its Environmental Effects. History of Smog. Name comes from a mix of “Smoke” and “Fog” First observed in London during the industrial revolution There are 2 types of smog: Industrial Smog (London) and Photochemical Smog (Los Angeles). Industrial Smog (Reducing).

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And its Environmental Effects

history of smog
History of Smog
  • Name comes from a mix of “Smoke” and “Fog”
  • First observed in London during the industrial revolution
  • There are 2 types of smog: Industrial Smog (London) and Photochemical Smog (Los Angeles)
industrial smog reducing
Industrial Smog (Reducing)
  • Source: Pollution from the burning of coal and oil that contains sulfur
  • Consists mainly of: Sulfur Dioxide, Sulfur Trioxide, soot and ash (particulate matter) and sulfuric acid
  • It can cause breathing difficulties in humans, plus acid rain damage to plants, aquatic systems, and metal or stone objects
  • London and Chicago have problems with industrial smog.
  • Methods of reducing this smog: Alkaline Scrubbers reduce SO2 and SO3 levels; electrostatic precipitators reduce particulates.
photochemical smog oxidizing
Photochemical Smog (Oxidizing)
  • Source: Mainly automobile pollution
  • Contains: Nitrogen Oxides, Ozone, Alkanals, Peroxyacyl Nitrates (PANs), plus hundreds of other substances
  • Effects: PANs cause eyes to water and can damage plants, O3 irritates eyes and deteriorates rubber and plants, NOx causes acid rain.
  • First observed in LA in the 1940s, Manila and Mexico City also experience this kind of smog
  • Catalytic Converters change NO to N2, Lean burning engines reduce Nox, but create more CO and Hydrocarbons.
reactions of smog
Reactions of Smog
  • Sulfur Dioxide can be oxidized to Sulfur trioxide, a secondary pollutant:
  • Metallic Particulates act as a catalyst for this reaction.
  • In addition, free radicals from NO2 also speed up the reaction:
reactions of smog6
Reactions of Smog
  • The formation of Secondary Pollutants in Photochemical Smog.

1. Formation of NOx:

2. Photo-Dissociation of nitrogen dioxide to produce oxygen atoms:

reactions of smog7
Reactions of Smog

3. Atomic oxygen forms Ozone:

4. Formation of organic free radicals:

reactions of smog8
Reactions of Smog

5. Formation of photochemical “soup” containing hundreds of chemicals including PANs:

thermal inversions
Thermal Inversions
  • Abnormal arrangement of air masses
    • A warmer layer of air is trapped between two layers of colder air
    • This causes pollutants to be trapped near the earth’s surface
  • Can form when hills or mountains stop horizontal winds, causing pollutants to collect over a city.
  • Warm air collects over the polluted air, acting as a lid to stop the pollutants from being dispersed.
  • In London, 1952, a thermal inversion lasting several days resulted in the deaths of several thousand people, most severely affecting the very old and young
  • Thermal inversions worsen any type of smog
thermal inversions10
Thermal Inversions

Cooler Air

Winds disperse pollutants worldwide

Warmer Air

Cooler Air

Warm air layer

Cool Air trapped at surface

Pollutants dissociate upwards

Pollutants trapped at surface

Normal Conditions

Thermal Inversion