Ozone layer  mary lam
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  • 1. Mary LamFall 2011
  • 2. What is Ozone? Molecule containing three oxygen atoms unstable with respect to O2 Blue in color and has a strong odor Very reactive gas, and even at low concentrations it is irritating and toxic Very powerful oxidizing agent
  • 3. Ozone Occurs naturally in small amounts in upper atmosphere and in the air of the lower atmosphere after a lightning storm. Oxidizes many organic compounds Powerful germicide, used to sterilize air and drinking water
  • 4. Formation of Ozone Ozone can be formed when a mixture of O2 and NO2 is exposed to bright light. Such mixtures occur in the polluted air of large cities.
  • 5. Earth’s Atmosphere Found in layers - Troposphere: lowest region, extends from the Earths surface up to about 10 kilometers (km) in altitude. -The next layer, the stratosphere, continues from 10 km to about 50 km.
  • 6. Environmental Issues Photochemical “smog”/ pollution Health problems Greenhouse gas Loss of ozone layer
  • 7. Ground-Level Ozone In the troposphere, ground-level or "bad" ozone is a pollutant that is a significant health risk It damages crops, trees and other vegetation. It is a main ingredient of urban smog.
  • 8. Ozone Pollution A concern during the summer months because strong sunlight and hot weather result in harmful ozone concentrations
  • 9. Ozone Alert The concentration of ozone in the air can reach levels that are dangerous for plants and animals. The U.S. Environmental Protection Agency characterizes ozone levels as "unhealthful" when they exceed the National Ambient Air Quality Standard of 125 parts per billion (ppb). In addition to posing a threat to health, ozone in the air also damages polymeric materials such as rubber and plastics, causing them to deteriorate prematurely.
  • 10. Stratosphere Most atmospheric ozone is concentrated in a layer in the stratosphere
  • 11. Stratospheric Ozone The stratosphere, or "good" ozone layer protects life on Earth from the suns harmful ultraviolet (UV) rays. Was gradually depleted by man-made chemicals like chlorofluorocarbons (CFCs). A depleted ozone shield allows more UV radiation to reach the ground.
  • 12. Greenhouse Gas The increases  Ozone is also a greenhouse gas in in primary the upper atmosphere greenhouse and, therefore, plays a role in Earths gases, such as climate. carbon dioxide, may affect how the ozone layer recovers in coming years.
  • 13. Ultraviolet Radiation Protection Absorbs a portion of the radiation from the sun, preventing it from reaching the planets surface Most importantly, it absorbs the portion of ultraviolet light called UVB. UVB has been linked to many harmful effects
  • 14. Ozone-Depleting substances(ODS) Chlorofluorocarbons (CFCs) Other chlorine-containing compounds include methyl chloroform, a solvent, and carbon tetrachloride, an industrial chemical. Halons, extremely effective fire extinguishing agents, and methyl bromide, an effective produce and soil fumigant, contain bromine.
  • 15. Chlorofluorocarbons Stable, low in toxicity, and inexpensive to produce Noncorrosive, nonflammable Used as refrigerants, solvents, foam blowing agents, and in other smaller applications Used in fire extinguishers, as propellants in aerosols, solvents in electronics manufacture, and as foaming agents in plastics.
  • 16. Ozone Depletion The CFCs are so stable that only exposure to strong UV radiation breaks them down. When that happens, the CFC molecule releases atomic chlorine. One chlorine atom can destroy over 100,000 ozone molecules. The net effect is to destroy ozone faster than it is naturally created.
  • 17. CFC’s http://www.youtube.com/watch?v=I1wrEvc2URE
  • 18. Ozone Hole An annual ozone “hole” has been documented over Antartica every spring since the early 1980s. Ozone depletion is focused mainly over Antarctica, and to a lesser degree the North Pole.
  • 19. Montreal Protocol Discontinue the production of CFCs, halons, carbon tetrachloride, and methyl chloroform and industry has developed more "ozone-friendly" substitutes. Montreal Protocol is widely considered to be the most successful of the global environmental treaties. The ozone layer is expected to recover over the next 50 years or so.
  • 20. If CFC’s Weren’t Regulated… http://www.youtube.com/watch?v=P- VZ3q7tbag
  • 21. Expected LearningOutcomes Discuss the differences between “good” and “bad ozone” Discuss how ozone is produced by human activity Discuss the Montreal Protocol
  • 22. Bibliography http://scifun.chem.wisc.edu/chemweek/ozo ne/ozone.html http://www.ozonelayer.noaa.gov/science/ba sics.htm http://www.epa.gov/oar/oaqps/gooduphigh/ bad.html#6 http://www.oar.noaa.gov/climate/t_ozonelay er.html http://www.eoearth.org/article/Montreal_Pro tocol_on_Substances_that_Deplete_the_O zone_Layer