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SMOG water damage los angeles

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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)

• 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)
• 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


• Sulfur Dioxide can be oxidized to Sulfur trioxide, a
  secondary pollutant:
                   2SO2  O2  2SO3
• Metallic Particulates act as a catalyst for this reaction.
• In addition, free radicals from NO2 also speed up the
  reaction:     NO + uv light  NO + O
                   2

                   SO2 + O  SO3
            Reactions of Smog

• The formation of Secondary Pollutants in
   Photochemical Smog.
1. Formation of NOx:
                 N 2(g) + O2(g)  2NO(g)
                 2NO(g) +O2(g)  2NO2(g)

2. Photo-Dissociation of nitrogen dioxide to produce
  oxygen atoms:
             NO 2(g) + uv light  NO(g) + O(g)
         Reactions of Smog

3. Atomic oxygen forms Ozone:
              O (g) + O 2(g)  O3(g)


4. Formation of organic free radicals:
              3O + HC  HCO3
                    -or-
              O3 + HC  HCO3
            Reactions of Smog
5. Formation of photochemical “soup” containing
   hundreds of chemicals including PANs:
     R-CH=CH-R + O3  RCH=O + R-O  + CH-O 
     hydrocarbon         alkanal   free radicals

     R-CH=O + O + uv light  R-C=O +  OH
                                  free radical
            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 Inversions
Cooler Air                                   Cooler Air


   Winds disperse pollutants worldwide



                                             Warm air layer
             Pollutants dissociate upwards

                                                                 Pollutants trapped
                                                                 at surface


Warmer Air                                   Cool Air trapped at surface
             Normal Conditions                            Thermal Inversion
Related Research
ANY QUESTIONS?

				
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posted:2/15/2011
language:English
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