1. Depletion of Ozone Layer 6S Yeung Wut Pan 6S Tsang Chi Ho

2. What is ozone layer? a layer in Earth ’ s atmosphere contains relatively high concentrations of ozone (O 3 ) absorbs 93-99% of the sun's high frequency ultraviolet light located in the lower portion of the stratosphere

3. The following equations describe how ozone is formed- O 2 ------------  O + O O+ O 2 ------------  O 3

4. Ozone and ultraviolet Ultraviolet is a kind of radiation Divided into three categories Harmful to humans Absorbed and screened by ozone

5. What caused ozone depletion? By free radical catalysts Emissions from jumbo jets and civil aircraft increased concentrations of chlorine and bromine, nitrogen oxides, and hydrogen liberated by the action of ultraviolet light initiate and catalyze a chain reaction

6. How the ozone layer is destroyed? CFCs (chlorofluorocarbons) commonly used in refrigeration and aerosol broken down by UV radiation and give out chlorine atoms which acts as the catalyst: CFCl 3 ---------  CFCl 2 + Cl Cl +O 3 -------  ClO +O 2 ClO +O -------  Cl +O 2 The Cl atom is then used again to destroy more ozone molecules.

8. Where does the most ozone depletion occur? A very large ozone hole forms at Antarctica. November 27, 2008

9. Results of ozone layer depletion Ozone levels drop being unable to absorb ultraviolet radiation an increase of skin cancer and eye cataract yield of crops decrease Economic loss global warming

10. What have been done? Monitor the use of CFCs Compounds containing C – H bonds designed to replace CFCs Lower sulphur jet aircraft fuel and redesigned engines Reduce vehicles ’ exhaust emissions Develop less polluting propulsion systems

11. Is the ozone layer recovering? The report from United Nations Environmental Programme in 2006 states that the Montreal Protocol is working. The ozone layer is expected to recover to pre- 1980 levels in 2050. If all emissions of ozone depleting substances were eliminated, the recovery will advance by 15 years.

12. What can we do to help? Use no CFCs items Conduct regular inspection and maintenance of air-conditioning and refrigeration appliances CFCs containing items should be recovered or recycled

13. Sources http://www.nasa.gov/vision/earth/environment/ozone _resource_page.html http://www.nasa.gov/vision/earth/environment/ozone _resource_page.html http://www.epd.gov.hk/epd/textonly/english/environ mentinhk/air/ozone_layer_protection/wn6_protect.ht ml http://www.epd.gov.hk/epd/textonly/english/environ mentinhk/air/ozone_layer_protection/wn6_protect.ht ml http://esrl.noaa.gov/csd/assessments/2002/qandas. html http://esrl.noaa.gov/csd/assessments/2002/qandas. html http://ozone.unep.org/index.shtml

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