Sources Of Air Pollutants
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Sources Of Air Pollutants

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    Sources Of Air Pollutants Sources Of Air Pollutants Presentation Transcript

    • O p tion E Environmental Chemistry Describe the main sources of carbon monoxide (CO), oxides of nitrogen (NO x ), oxides of sulfur (SO x ), particulates and volatile organic compounds (VOCs) in the atmosphere
    • Methane produced animals as a digestive gas (e.g. cows) Bacterial decomposition of organic matter in marshes and tropical regions (e.g. rice fields, rivers, lakes) Natural Sources of Carbon Monoxide
    • Oxidation of methane
      • Methane oxidises to produce the primary pollutant CO and H 2 O
      • 2CH 4 (g) + 3O 2 (g)  2CO (g) + 4H 2 O (l)
    • Man-made sources of Carbon Monoxide Factory combustion Power plants Combustion of Fossil fuels Vehicular exhausts
    • Combustion of fossil fuels
      • Under the presence of oxygen, combustion of fossil fuels will produce carbon dioxide and water.
      • CH 4 + 2O 2  CO 2 + 2H 2 O
      • Lack of oxygen will result in incomplete combustion to produce carbon monoxide instead of carbon dioxide.
      • C 7 H 16 + 7 ½O 2  7CO + 8H 2 O
    • Oxides of Nitrogen (NO x )
      • Nitrogen gas exists as N 2 molecules in the air
      • N 2 is inert in room temperature and does not produce Oxides of Nitrogen as atoms are share a triple bond
      • Reaction occurs at high temperatures
        • N2 (g) + O2 (g)  2NO (g)
        • N2 (g) + 2O2 (g)  2NO2 (g)
    • Natural sources of Nitrogen Oxides
      • B acterial decomposition of nitrogen containing compounds
      • High energy of lightning will produce N 2 O and NO
    • Man-made sources of Nitrogen Oxides E xhaust gases from internal combustion engines Wood and fuels Airplanes
    • Oxides of Sulfur (S O x )
      • Sulphur Dioxide (SO 2 ) is the most abundant in the atmosphere whilst sulphur trioxide (SO3) is only produced in very small amounts
      • Atmospheric Sulphur dioxide tend to oxidise into sulphur trioxide over time
      • Reaction is speeded up by the presence of heavy metal pollutants and finely divided particulates of ash
      • 2SO 2 (g) + O 2 (g)  2SO 3 (g)
    • Sources of S O x : Coal
      • Combustion of coal can produce SO x
      • Poor quality coal can contain up to 7% sulphur; although most contain 1 to 5%
      • Sulfur present in coal are in the form of elemental sulfur, iron pyrite and organic sulfur compounds
      • S (s) + O2 (g)  SO2 (g)
      • 4FeS2 (g) + 11O2 (g)  2Fe2O3 (s) + 8SO2 (g)
    • Other sources of SO x
      • Smelting plants oxidise sulfide ores to produce metal oxides; thus producing SO 2
      • Cu 2 S (s) + 2O 2 (g)  2CuO (s) + SO 2 (g)
      • Production of Sulfuric acid
      • Sulfur dioxide is produced due to lack of oxygen
    • Natural Sources of SO x
      • No major natural primary sources of sulphur dioxide
      • Small amounts produced from volcanic and bacterial activity
      • Sulphur dioxide is produced in the atmosphere from oxidation of H 2 S
      • 2H 2 S (g) + 3O 2 (g)  2SO 2 (g) + 2H 2 O (l)
    • Particulates
      • These substances are solid particles suspended and carried within the air. They are generally large enough to be seen.
    • Sources of Particulates
      • Naturally produced by sandstorms, volcanic activity and forest fires started by lightning
      • Man-made sources include the combustion of fossil fuels used by the industry, vehicular exhaust from transportation, industrial plants which produce smoke, soot, ash and dust.
    • Volatile Organic Compounds (VOCs)
      • These substances are primary pollutants directly introduced into the environment. Examples include hydrocarbon gases and volatile organic liquids that can easily convert into gases and escape into the air.
    • Sources of VOCs
      • Methane (CH4) is produced by anaerobic bacterial decomposition of organic matter in bodies of water including swamps and oceans
      • Methane is also produce as a digestive gas in many animals (e.g. cows)
      • Vegetation produced VOCs called terpenes
      • Man-made sources include extracting, refining, transporting petroleum as well as using petroleum products can result in air pollution