L 30 final

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AIR POLLUTION CONTROL course material by Prof S S JAHAGIRDAR,NKOCET,SOLAPUR for BE (CIVIL ) students of Solapur university. Content will be also useful for SHIVAJI and PUNE university students

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L 30 final

  1. 1. What do you think why such a difference is there?
  2. 2. L-30 UNIT-VI Photochemical smog Air Pollution and Control (Elective - I)
  3. 3. Unit- VI L-29 Chemistry of air pollution, Chain reactions of hydrocarbons, nitrogen oxide, Sulphuric oxides and intermediates, photochemical smog formation L-30 Air pollution indices -aerosols, fog, smog index.
  4. 4. Smog  The word ‘smog’ comes from two words: smoke and fog.  Characterize visible combination of smoke and fog  Occurs in highly motorised areas and where inversion conditions prevail in the atmosphere. e.g. – Los Angeles  It is because of action of sunlight on H-C (Hydrocarbons) and Nitrogen Oxides (NOx) emitted from the automobiles
  5. 5. smog primary pollutants   volatile hydrocarbons VOC nitrogen oxides secondary pollutants      ketones, aldehydes, PANs, peroxides, ozone,
  6. 6. Smog Formation Sun
  7. 7. Composition of smog       Nitrogen oxides Ozone Aldehydes Unreacted carbon Particular matter Peroxyaceyl nitrate (PAN)
  8. 8. Chemical compounds involved Molecule Name and Formula Nitric Oxide, NO Nitrogen Dioxide, NO2 Ozone, O3 ThreeTwo-Dimensional Dimensional Representation Representation
  9. 9. Acetaldehyde, C2H4O (an example of an Aldehydes) Peroxyacetyl Nitrate, C2H3O5N 1,3-Butadiene, C4H6 (an example of a volatile organic hydrocarbon)
  10. 10. smog: variation in day
  11. 11.    Early morning traffic increases the emissions of both nitrogen oxides and VOCs as people drive to work. Later in the morning, traffic dies down and the nitrogen oxides and volatile organic compounds begin to be react forming nitrogen dioxide, increasing its concentration. As the sunlight becomes more intense later in the day, nitrogen dioxide is broken down and its by-products form increasing concentrations of ozone.
  12. 12.   At the same time, some of the nitrogen dioxide can react with the volatile organic compounds to produce toxic chemicals such as PAN. As the sun goes down, the production of ozone is halted. The ozone that remains in the atmosphere is then consumed by several different reactions.
  13. 13. Colour   Nitrogen dioxide is responsible for the brownish colour of the haze. The particulates formed and the brown colour of nitrogen dioxide give the air a dirty, ‘smoggy’ appearance.
  14. 14. Los Angeles Photochemical smog / LA smog 18
  15. 15. Photochemical smog / LA smog LA Santiago Las Vegas
  16. 16. Reaction with NO2       UV light energy is absorbed by NO It moves into high energy state and becomes unstable. Then decomposes in to NO and O (nascent oxygen) Nascent oxygen quickly reacts with atmospheric oxygen to form ozone. This reaction takes place in presence of third body (X). If nitric oxide is present it reacts with ozone to form NO2 and O2
  17. 17. Chemical reactions :NO2 + hv  NO*  O + O2  O3 O3 + NO  NO2 +O2 NO2 behaves like catalyst NO + O
  18. 18. Aldehydes Peroxyacyl radical Acetyl radical
  19. 19. Acetaldehyde Acetone Methyl Methyl Formyl radical Acetyl
  20. 20. Factors affecting photochemical reactions       Light intensity Hydrocarbon reactivity. Ratio of H-C to nitric oxide Presence of light absorbers Meteorological variables Height and intensity of atmospheric inversion
  21. 21. smog: effects  Effects on human health     Headaches Eyes, nose and throat irritations Impaired lung function Coughing and wheezing
  22. 22.   PAN’s cause eyes to water and respiratory problems, also catalyses formation of sulphuric acid, ozone in the troposphere is:       an eye irritant and also irritates respiratory system causes deterioration of rubber as it breaks –C=Cand bleaches dyes affects leaves and therefore growth/damages crops reduced visibility secondary pollutants are toxic to plants corrosion of building materials by acids and ozone.
  23. 23. Objective Questions 1. 2. 3. 4. 5. _________________ is main driving factor for photochemical smog formation. NO2 acts as ________________. Increase in ozone concentration during day time indicates _____________________ formation. Cracking of rubber takes place because of ______. Photochemical smog occurs in highly _________area.
  24. 24. Theory Questions Q1. Write detailed short note on ‘Photo-chemistry of air pollution’ OR Explain ‘Photochemical reactions’ in detail. Q2. Explain effects of photochemical smog.
  25. 25. Video Clip-1
  26. 26. Video Clip-2

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