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O 3 zone Story Terry Deshler, Atmospheric Science

O 3 zone Story Terry Deshler, Atmospheric Science. Formation Importance Loss Before 1985 After 1985 Recovery Relationship to global warming The end. Relationship to Global Warming. Peripheral Ozone has a slight greenhouse effect, but

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O 3 zone Story Terry Deshler, Atmospheric Science

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  1. O3zone StoryTerry Deshler, Atmospheric Science • Formation • Importance • Loss • Before 1985 • After 1985 • Recovery • Relationship to global warming • The end

  2. Relationship to Global Warming • Peripheral • Ozone has a slight greenhouse effect, but • Loss of ozone over Antarctica may have intensified the polar vortex and reduced the warming expected in Antarctica • CFCs are a significant green house gas • Reduction of CFCs largest single human action mitigating the current warming

  3. The End? • No, we have to limit the release of CFCs into the atmosphere from now on. • The good news - the atmosphere will cleanse itself of present atmospheric chlorine. • The bad news - it will take another 50 years to see the ozone hole above Antarctica disappear.

  4. Ozone Formation • O2 + hO + O • Then, O + O + M O2 + M • or O + O2 + M O3 + M (Ozone created) • Where will this primarily occur? • Also, O3 + h ( > 310 nm) O2 + O • and O3 + h ( < 310 nm)O2* + O* (UV absorption) • O2* + O2 2O2 + thermal energy (Excess energy dumped • O2*O2 + h ( = 1.3 m) in ozone layer)

  5. Importance of ozone • Absorbs DNA damaging UV radiation • This UV affects both animals and plants • SH/NH differences - In summer UV radiation is 50% more intense in SH than NH. Australia - world leader in skin cancer • Reasons • 10% - Earth is closer to sun in SH summer than NH summer • 20% - Antarctic ozone loss/clearer atmosphere • 20% - Unknown

  6. Food Preservation • 100 BC - 1700s, Early methods: Drying, Salting, Cool cellars/Spring houses, Pickling, Fermenting, Canning. • Cooking -> could eat spoiled food - spices to hide the flavor. • 1803 Ice Boxes - Thomas Moore invented the insulated box, with ice was in a separate container above the food storage area. Relied on stores of natural ice from frozen lakes and rivers. • 1850s - Methods to artificially produce ice were developed. • 1890 - Warm weather/rain lead to a shortage of natural ice. Spurred the development of mechanical refrigeration.

  7. Refrigeration • 1918 - Kelvinator, First refrigerator introduced to American market. • 1920s - Refrigerators used ammonia (NH4), sulfur dioxide (SO2), (toxic, odorous), and methyl chloride (CH3Cl), (toxic, no odor) - silent killer. • 1928 - Thomas Midgley, Fridgidaire, dichlorodifluoromethane (CCl2F2) • 1929 - Fridgidaire and DuPont joined to produce CCl2F2, and CFCl3 as Freon.

  8. 1974 - Molina and Rowland - simple question - What happens to CFCs released into the atmosphere? (awarded Nobel prize Chemistry 1995) CCl3F(F-11) + h ( < 240 nm, z > O3 layer) CCl2F + Cl CCl2F2 (F-12) + h ( < 240 nm, z > O3 layer) CClF2 + Cl • Then • Cl + O3ClO + O2 • ClO + OCl + O2 • Net: O3 + OO2 + O2 • This would occur above ozone layer altitudes above 30 km

  9. Reservoir molecules • 1975 - 1980 – Predicted ozone losses above 30 km were not observed. Reservoir molecules discovered. • Cl+ CH4HCl+ CH3 • ClO + NO2ClONO2 • HCl and ClONO2are reservoirspecies. 1984 – Models predict 10% ozone loss in 100 years for current CFC production rates.

  10. Ozone Profiles McMurdo Station, Antarctica 1986 - 1994 1986 1988 1987 1991 1989 1990 1992 1993 1994

  11. Late winter spring During Winter

  12. Catalytic Cycle Polar Stratosphere • PSC particle + HCl + ClONO2Cl2 • Cl2 + hCl + Cl • 2 [ Cl + O3ClO + O] • ClO + ClO + M ClOOCl + M (M=N2 or O2) • ClOOCl + hCl + ClOO • ClOO + M Cl + O2 + M • h = Sun’s return • Net 2O3 + h 3O2 • A single Cl atom can destroy more than100,000 ozone molecules. • This cycle will continue until the NO2 and OH lost in the form of HNO3 in polar stratospheric clouds is replenished by mid latitude air, thus converting Cl back to its reservoir species.

  13. Nitric acid/water Ice Nitric acid/water Ice

  14. Antarctic ozone hole discovered Molina & Rowland, 1974 Montreal Protocol, and amendments Reservoir Molecules Discovered

  15. An Industry in Transition 1986 Base Year for Montreal Protocol 1974 Ozone Depletion Hypothesis 1996 CFC Phaseout Complete in Developed Countries Thousands of tonnes HFCs HCFCs CFCs Refrigerants Other Refrigerants Solvents Fire Extinguishants Foam Expansion Propellants

  16. Return

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