1. Ozone Depletion

3. O3 in troposphere Photo-chem rxns produce O3 from NOx, HC and O2
O3 is a strong oxidant.

5. O3 in troposphere Causes eye & lung damage to mammals
Damages or kills leaves
Weakens or kills trees

9. O3 in stratosphere O3 forms when sunlight strikes O2
About 90% of Earth’s O3 is in stratosphere

11. UV

14. UV-A UV-A is 320 - 400 nm (longest of the UV)
Least energetic of the UV, causes some cell damage
All UV-A reaches Earth’s surface
O3 doesn’t absorb UV-A

15. UV-B UV-B is most harmful to cells
Most UV-B absorbed by O3, some reaches Earth’s surface
O3 depletion has increased UV-B at Earth’s surface

16. UV-C UV-C is 100 - 290 nm (shortest of the UV)
Most energetic of the UV’s
All is absorbed by O3 in stratosphere

18. Measuring O3 Ground-based monitors & satellites
1 ppb of ozone = 1 Dobson unit (DU)

19. Ozone should be added to the stratosphere constantly
But…..for the little problem of the CFCs

20. Chloro-fluoro-carbon rxns
Cl3CF + UV  Cl2 + Cl
Cl + O3  ClO + O2
ClO + O  Cl + O2

21. Thus, CFCs stop the production of ozone.

22. CFCs Are used during industrial processes & for refrigeration.
Are non-reactive, thus can drift for years, eventually in stratosphere.
The chlorine is a catalyst that can be used over & over, as many as 100,000 O3  O2

23. Antarctic O3 depletion

24. mid-May (winter) Dark & cold (< - 80º C)
Cold air descending (high pressure)
Coriolis effect sets up a strong westerly wind (counter-clockwise) = a vortex
Vortex traps Antarctic air

26. mid-May continued
Clouds of ice crystals form in stratosphere, providing surface area for CFC-O3 rxns
Clouds & winds trapped within vortex

27. Oct – Nov (springtime) Increasing sunlight including UV
CFCs - O3 rxns increase
> 50% of stratospheric O3 is destroyed over Antarctica

29. mid-December (end of spring)
Warming temps cause vortex to break up.
Ozone-rich air from the north floods into Antarctica
While ozone-depleted air flows northward into S. America & New Zealand

31. Ozone hole

32. Ozone “hole” Not really a hole; more of a thinning.
Defined as concentrations of O3 < 200 ppb
Occurs during Antarctic spring (Sept-Nov)

38. At its “peak” in September, the ozone hole was
27.2 million km2 in (3rd)
29.5 mkm2 in 2000 (largest)
28.7 mkm2 in (2nd largest)
24.3 mkm2 in 2004
25.9 mkm2 in 2005

39. Declines may be linked to warmer winter Antarctic temperatures.
Why the declines?
Declines may be linked to warmer winter Antarctic temperatures.
Global warming?

40. Ozone trends (1) Depletion probably began mid 1970s
(2) Sulfate aerosol emissions from the 1991 Mt Pinatubo eruptions probably caused greater depletion

42. Ozone trends continued
(3) At polar latitudes, sun is lower in sky and light passes through more atmosphere. Thus, less UV reaches surface at polar latitudes.

43. (4) Industrials areas have more ozone at surface levels
(4) Industrials areas have more ozone at surface levels. Ozone absorbs UV and may be why scientists can’t find increased levels of O3 in Northern Hemisphere

44. Ozone trends continued
(5) The energy of > UV-B at Earth’s surface causes > formation of surface O3.

45. Why no ozone “hole” at North Pole?
Warmer temps compared to S. Pole
Jet stream tends to meander rather than creating vortex
However, recent measurements show 5% O3 depletion over North Pole.

46. Effects of O3 depletion

47. Marine food chains
> UV causes decline in productivity of polar phytoplankton
Equatorial phytoplankton have adaptations for UV, no surprise

50. UV Damage to Humans
(1) Clouding of eye’s cornea  cataracts

52. (2) Basal carcinoma

53. Basal carcinoma

54. (3) Melanoma

57. (4) Changes to DNA

59. Is a suntan really a good idea?
Wrinkles

61. As long as O3 depletion continues,
It would be a good idea to add a few things to your self-survival kit.

67. The end