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The reduction of ozone over Antarctica over time. Area in purple indicates the “ozone hole.”

Stratospheric Ozone Depletion. The reduction of ozone over Antarctica over time. Area in purple indicates the “ozone hole.”. Ozone in the Stratosphere- What causes an Ozone hole? . FIGURE 01b: Ozone concentrations in the atmosphere and stratosphere. CFC.

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The reduction of ozone over Antarctica over time. Area in purple indicates the “ozone hole.”

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  1. Stratospheric Ozone Depletion The reduction of ozone over Antarctica over time. Area in purple indicates the “ozone hole.”

  2. Ozone in the Stratosphere- What causes an Ozone hole?

  3. FIGURE 01b: Ozone concentrations in the atmosphere and stratosphere

  4. CFC • Three key ingredients in Polar Ozone Loss • CFCs as source of catalyst, CFCs  Cl radicals • Sunlight • 3. Surface for heterogeneous reactions

  5. How does ozone form in the stratosphere / what controls the concentration • Ozone is produced when an oxygen molecule and an oxygen atom combine: • O2 + O + M  O3 + M • The source of the oxygen atom in the stratosphere is photolysis of O2: • O2 + hn  O + O • So the basic series of reactions involving ozone in the are: • O2 + hn  O + O • O2 + O + M  O3 + M • O3 + hn  O2 + O • O3 + O  O2 + O2

  6. Possible Explanation for Major Ozone Loss- Refrigerants, CFCs  Cl radicals A catalytic cycle involves chlorine Cl + O3  ClO + O2 ClO + O  Cl + O2 O3 + hn  O2 + O 2O3 + hn  3O2 Eventually, Cl is “tied up” in reservoir species that do not participate in reactions involving O3 Cl + CH4  HCl + CH3 ClO + NO2 + M  ClONO2 + M Point out that NO is lost in the 1st reaction, but produced in the 2nd, while NO2 is produced in the 1st, but lost in the 2nd – i.e., no net change.

  7. Ground based Observations of Ozone Loss over Antarctica

  8. This enhanced depletion is related to stratospheric clouds HOCl Cl2 Ice ClONO2 HCl

  9. Banning of CFCs • 1987 Montreal Protocol • 1990 London Agreement • 1992 Copenhagen Amendments

  10. FIGURE 5: Predicted concentrations of ozone-depleting chemicals in the atmosphere under various scenarios

  11. Great Scientific Success- Announced in August of 2006-The ozone hole is in recovery!

  12. FIGURE 04b: Computer-generated images of the changing size of the ozone hole over Antarctica Courtesy of NASA/JPL/Agency for Aerospace Programs (Netherlands)/Finnish Meteorological Institute

  13. Susan Solomon, senior scientist with the National Oceanic and Atmospheric Administration • Solomon expects a full recovery of the ozone hole by 2060. But, she cautions, a lot of work must be done to reach that goal. "I think that it is very important to make sure that we actually measure ozone not only not getting any worse, but actually starting to improve to make sure that the actions that we have taken internationally have been effective." • CFCs are long-lived and remain in the atmosphere for 50 to 200 years. But with global phase-out efforts, Solomon expects to see signs of a reduction in the ozone hole within a decade. Her job, she says, is to measure that process.

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