Ozone Depletion

1. J(Hans) van Leeuwen Ozone Depletion – The hole story Stratospheric ozone and its importance

2. Solar Spectrum

3. 400nm 100nm Visible Light Radio IR UV X-Rays l FarUV UV-A UV-B UV-C 300nm 200nm DNA damaging range The Ultraviolet Spectrum • UV light: 100 to 400 nm UV spectrum – 4 regions • Far UV: 100 – 200 nm • UV – C : 200 – 280 nm • UV – B : 280 – 315 nm • UV – A : 315 – 400 nm

4. DNA Damaging Range of UV Light

5. Ultraviolet Radiation • 230-280 nm damages nucleic acids • Stops reproduction of cells by breaking apart the DNA bonds • Ozone production peaks at 185nm • Ozone absorbance and destruction at 200-320nm Ozone destruction Ozone formation  

6. UV ozone generation and destruction: equilibrium • O2 + h185 2O. • O.+ O2 + M  O3 + M • O3 + h254  O2 + O. Equilibrium between production and destruction

7. Atmospheric Layers

8. Ozone Formation and Depletion

10. The catalyzed cycle of stratospheric ozone production and destruction • h + O2 2O. • O. + O2 O3 • O3 + X  O2 + OX • 4. OX + O.  O2 + X X could be Cl from a CFC

12. Halogen catalysis of ozone destruction ozone:

13. Halogen removal from atmosphere • Cl + CH4 HCl + CH3. • ClO + NO2  ClONO2 Both HCl and ClONO2 inactive: rain out • Br + O3  BrO + O2 • Br + CH4  HBr + CH3. HBr can photolytically provide Br again Halons and CH3Br provide Br

14. Ozone Depleting Substances List of ozone depleting substances Table 8.13 Masters http://www.epa.gov/ozone/ods.html Halons

15. Antarctic Ozone Problems

16. Antarctic Vortex during Winter Strong circulatory winds around Antarctica isolate the air in the lower and middle stratosphere Ice crystals form in vortex

17. Antarctic Reactions Winter reactions • Polar vortex: -90 oC  Ice clouds • ClONO2 + H2O  HOCl + HNO3 • HOCl + HCl  Cl2 + H2O Spring reactions • Cl2 + h  2 Cl in early spring • Cl + O3  ClO + O3 destructive loop • HNO3 + Cl  ClONO2in photocatalysis

18. Ozone in Stratosphere: Dobson Units (DU) If 100 DU of ozone were brought to the Earth's surface, it would form a layer 1 millimeter thick. In the tropics, ozone levels are typically between 250 and 300 DU year-round. In temperate regions, seasonal variations can produce large swings in ozone levels. For instance, measurements in Leningrad have recorded ozone levels as high as 475 DU and as low as 300 DU.

19. Record ozone hole, 2006

21. Ozone hole altitude profile

22. Ozone hole severity

23. Ozone hole extent

24. Global total ozone change

27. http://jwocky.gsfc.nasa.gov/

31. The Nobel Prize in Chemistry 1995 Paul J. CrutzenMario J. MolinaF. Sherwood Rowland The Netherlands USA USA Max-Planck-Institute MIT, USA Department of Chemistry, for Chemistry Mainz, Germany Cambridge, MA University of California Irvine, CA, USA 1933 - 1943 - 1927 - "for their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone"

39. Ozone Hole Growth: 29y September 21, 2006 September 17, 2009 October 27, 1980 http://www.youtube.com/watch?v=brblHxZctsA

40. Ozone Hole 2009

41. Ozone Hole 2009

42. Ozone Hole 2009

44. Ozone hole size in recent years

45. http://www.cmdl.noaa.gov/ozwv/ozsondes/spo/ozone_anim2004.htmlhttp://www.cmdl.noaa.gov/ozwv/ozsondes/spo/ozone_anim2004.html