Published on

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

Published in: Technology, Health & Medicine
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide


  1. 1. L-11 OZONE DEPLETION Air Pollution and Control (Elective(Elective-I)
  2. 2. Earth’s Atmosphere Prof S S Jahagirdar, NKOCET 2
  3. 3. The ozone layer • • • • Ozone is an unstable gas It rapidly breaks down The ozone layer is only a few cm thick If the rate of breakdown is faster than the rate of formation the ozone layer thins • This could develop into hole • An ozone hole was first observed over the Antarctic in 1985 Prof S S Jahagirdar, NKOCET 3
  4. 4. The Discovery • In 1985, using satellites, balloons, and surface stations, a team of researchers had discovered a balding patch of ozone in the upper stratosphere, the size of the United States, over Antarctica. British Atlantic Survey Research station, Holly Bay, Antarctic coast Team who discovered the hole 1985. From left: Joe Farman, Brian Gardiner, and Jonathan Shanklin Prof S S Jahagirdar, NKOCET 4
  5. 5. Prof S S Jahagirdar, NKOCET 5
  6. 6. What is ozone? • Ozone forms a layer in the stratosphere, thinnest in the tropics (around the equator) and denser towards the poles • measured in Dobson units (DU) • ~260 DU near the tropics Prof S S Jahagirdar, NKOCET 6
  7. 7. What is a Dobson unit? • 1 Dobson Unit (DU) is defined to be 0.01 mm thickness at STP - (00C and 1 atmos pressure). • A slab 3mm thick corresponds to 300 DU Prof S S Jahagirdar, NKOCET 7
  8. 8. How is ozone formed? UV radiation strikes the O2 molecule and splits it, atomic oxygen associates itself with another O2 molecule – simplistic version Prof S S Jahagirdar, NKOCET 8
  9. 9. How ironic . . . • At ground level, ozone is a health hazardhazard-major constituent of photochemical smog • However, in the stratosphere, we could not survive without it. • It absorbs potentially harmful ultraultraviolet (UV – 240-320nm harmful) 240radiation • Protects from skin cancer, etc 9 Prof S S Jahagirdar, NKOCET
  10. 10. The ozone layer is in the stratosphere Good up high!  Bad nearby! 
  11. 11. “Chapman Reactions” • Ozone is formed by: O2 + hv -> O + O (1) • Ozone can reform resulting in no net loss of ozone: O3 + hv -> O2 + O O + O2 -> O3 • Ozone is also destroyed by the following reaction: O + O3 -> O2 + O2 Prof S S Jahagirdar, NKOCET (3) (2) 11 (4)
  12. 12. Comparison of reactions • Reaction (2) slower with increasing altitude • Reaction (3) faster with increasing altitude • Lower in stratosphere, atmosphere denser, UV absorption increases – ozone peaks 20km • Closer to surface, UV level decreases, ozone decreases Prof S S Jahagirdar, NKOCET 12
  13. 13. The ozone layer •Ozone is a triatomic form of oxygen (O3) found in Earth’s upper and lower atmosphere. •The ozone layer, situated in the stratosphere about 15 to 30 km above the earth's surface. •Ozone protects living organisms by absorbing harmful ultraviolet radiation (UVB) from the sun. Prof S S Jahagirdar, NKOCET 13
  14. 14. ultraviolet A (long-wave) and ultraviolet B (shortwave) rays Prof S S Jahagirdar, NKOCET 14
  15. 15. • The ozone layer is being destroyed by CFCs and other substances. • Ozone depletion progressing globally except in the tropical zone. • Chlorofluoro carbons (CFC’s) and other halogenated hydrocarbons contribute to the destruction of stratospheric ozone. • Just one chlorine and bromine atom can catalyze the destruction of 100,000 ozone molecules 15 Prof S S Jahagirdar, NKOCET
  16. 16. What are CFCs? • Used as propellants in aerosol spray cans • Used as refrigerants in fridges, freezers and air conditioning units Prof S S Jahagirdar, NKOCET 16
  17. 17. Prof S S Jahagirdar, NKOCET 17
  18. 18. The ozone depletion process Prof S S Jahagirdar, NKOCET 18
  19. 19. Too much ultra-violet light can result in: ultrain: • • • • • • Skin cancer Eye damage such as cataracts Immune system damage Reduction in phytoplankton Damage to the DNA in various life-forms Possibly other things too that we don't know about at the moment 20 Prof S S Jahagirdar, NKOCET
  20. 20. Effects on Plants Physiological and developmental processes of plants are affected by UVB radiation, even by the amount of UVB in present-day sunlight. Prof S S Jahagirdar, NKOCET 21
  21. 21. • Effects on Marine Ecosystems • Phytoplankton form the foundation of aquatic food webs. • Exposure to solar UVB radiation has been shown to affect both orientation mechanisms and motility in phytoplankton, resulting in reduced survival rates for these organisms. Prof S S Jahagirdar, NKOCET 22
  22. 22. • Effects on Biogeochemical Cycles • Increases in solar UV radiation could affect terrestrial and aquatic biogeochemical cycles, thus altering both sources and sinks of greenhouse and chemically-important chemicallytrace gases. • e.g., carbon dioxide (CO2), carbon monoxide (CO), carbonyl sulfide (COS) and possibly other gases, including ozone. • These potential changes would contribute to biospherebiosphere-atmosphere feedbacks that attenuate or reinforce the atmospheric buildup of these 23 Prof S S Jahagirdar, NKOCET gases.
  23. 23. • Effects on Materials • Synthetic polymers, naturally occurring biopolymers, biopolymers, as well as some other materials of commercial interest are adversely affected by solar UV radiation. • Today's materials are somewhat protected from UVB by special additives. • Therefore, any increase in solar UVB levels will therefore accelerate their breakdown, limiting the length of time for which they are useful outdoors. Prof S S Jahagirdar, NKOCET 24
  24. 24. Immune Suppression •Scientists have found that overexposure to UV radiation may suppress proper functioning of the body’s immune system and the skin’s natural defenses. • For example, the skin normally mounts a defense against foreign invaders such as cancers and infections. Prof S S Jahagirdar, NKOCET 25
  25. 25. • But overexposure to UV radiation can weaken the immune system, reducing the skin’s ability to protect against these invaders. Prof S S Jahagirdar, NKOCET 26
  26. 26. Effects on Human Health Skin cancer - Unprotected exposure Non-malignant to UV radiation is the most preventable risk factor for skin cancer. malignant 27 Prof S S Jahagirdar, NKOCET
  27. 27. Over Exposure • Accelerate aging of skin due high exposure -The face, hands, forearms, and the “V” of the neck are especially susceptible to this type of lesion. Prof S S Jahagirdar, NKOCET 28
  28. 28. • Cataract - Cataracts are a form of eye damage in which a loss of transparency in the lens of the eye clouds vision. - If left untreated, cataracts can lead to blindness. - Research has shown that UV radiation increases the likelihood of certain cataracts. 29 Prof S S Jahagirdar, NKOCET
  29. 29. What can be done? • Reduce the use of CFCs • They are already banned in aerosols (1987) • BUT they are still used as refrigerants • Recycle fridges and air conditioning plants Prof S S Jahagirdar, NKOCET 30
  30. 30. Skin Protection • Protect the skin against the solar radiation using skin creams with SPF • Use lip balm with SPF • Cover up Prof S S Jahagirdar, NKOCET 31
  31. 31. Protection • Sunglasses with 100% UV block • Wrap around sunglasses • Eye protection for children • Hats Prof S S Jahagirdar, NKOCET 32
  32. 32. What Is Being Done to Counter the Effects of Ozone Depletion? • Montreal Protocol (adopted in 1987) – panel of experts was formed to investigate substances responsible for hole formation • Established policies that prevent future use of certain types of chemicals • Stipulated that the production and consumption of compounds contributing towards depletion of ozone in the stratosphere were to be phased out by the year 2000 (2005 for methylchloroform) methylchloroform) 33 Prof S S Jahagirdar, NKOCET
  33. 33. The current situation • The holes developing over the pole suggest that they may be show an improvement • BUT CFC molecules take 30 years to rise up to the stratosphere • The chlorine radicals last a long time • The peak ozone damage was supposed to be in 2000 • Damage could go on another 50 years © 2007 Paul Billiet ODWS
  34. 34. Signs of Recovery??? There have been some signs of recovery • 1997 satellite showed a decline of several known ozone-depleting gases ozone• Satellite images show some slowing down of ozone loss However…. Antarctica - Dec. 2005 Recovery is slow Prof S S Jahagirdar, NKOCET 35
  35. 35. Objective Questions Q1. Ozone hole was first observed in ____. Q2. The ozone layer, situated in the stratosphere about __________km above the earth's surface. Q3. _______ is responsible for ozone depletion. Q4. ___________ protocol was first step towards reducing use of CFCs. Q5.Breaking of ozone molecule takes place in presence of ________________. Prof S S Jahagirdar, NKOCET 36
  36. 36. Q6. Ozone layer thickness is measured in ____________ units. Q7. Formation and destruction of ozone in the atmosphere can be explained by ___________ reactions. Q8. 1 Du = ____________________________. Prof S S Jahagirdar, NKOCET 37
  37. 37. Theory Questions Q1. Explain ‘Ozone depletion process with respect to following points - Sources/causes - Chemical reactions - Effects - Remedies Q2. Define Dobson unit. Q3. Explain Chapman reactions. Prof S S Jahagirdar, NKOCET 38
  38. 38. Prof S S Jahagirdar, NKOCET 39
  39. 39. Prof S S Jahagirdar, NKOCET 40