Lecture 6 - Ozone

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Lecture 6 - Ozone

  1. 1. Ozone Chemistry and Ozone Depletion
  2. 2. Aurora over Halley Bay Station, Antarctica, 75.6ºS 26.5ºE Brunt Ice Shelf, Coats Land 105 days of continuous darkness Population: 65 in summer, 15 in winter
  3. 3. The Four Principal Layers of the Atmosphere
  4. 4. UV rays + =Molecular Oxygen Ozone Oxygen Atoms Molecule UV rays +
  5. 5. UV rays + =Molecular Oxygen Ozone Oxygen Atoms Molecule UV rays +
  6. 6. Distribution of Ozone 100 60 Thermosphere 80 50 Altitude (miles) Mesosphere 40 60Altitude (km) Ozone 30 Oxygen 40 20 90% of ozone is in the stratosphere 20 10 10% of ozone is in the troposphere Troposphere 0 0 0 2 4 6 8 Ozone (parts per million)
  7. 7. Ozone is the Earth’s natural sunscreen100 60 Thermosphere80 UVc - 100% Absorption 50 Mesosphere UVb - 90% Absorption Altitude (miles) UVa - 50% Absorption & Scattering 4060 3040 2020 10 Troposphere 0 0 0 2 4 6 8 Ozone (parts per million)
  8. 8. UV radiationCCl3F(g) ---------> CCl2F(g) + Cl(g)Cl(g) + O3(g) ----> ClO(g) + O2(g)ClO(g) + O(g) ----> O2(g) + Cl(g)
  9. 9. Other gases Methyl chloroform (CH3CCl3) Other halons3400 1% HCFCs (e.g., HCFC-22 = CHClF2) 4% 20 Halon-1301 (CBrF 3) 4% CFC-113 (CCl2FCClF2) 5%3000 7% Carbon tetrachloride 14% (CCl4) Halon-1211 (CBrCIF 2) 12% 15 CFC-11 (CCl3F) 20%2000 5-20% 23% 10 Methyl bromide (CH3Br) CFC-12 (CCl2F2)1000 5 32% 27-42% Very-short lived gases Methyl chloride (CH3Cl) Natural (e.g., bromoform = CHBr3) sources 16% 15% 0 0
  10. 10. Ozone Hole as of September 2006

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