Everything you should KNOW about OZONE

1. Everything you should KNOW about OZONE

3. 1. O3 in the troposphere • Photo-chemical rxns produce O3 from NOx, HCs (VOCs), and O2 • O3 is a strong oxidant.

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

8. 2. O3 in Stratosphere • O3 forms when sunlight strikes O2 • O2 + O => O3 • About 90% of Earth’s O3 is in stratosphere

10. 3. UV

13. 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

14. UV-B • UV-B is most harmful to cells • 290 – 320 nm • Most UV-B absorbed by O3, some reaches Earth’s surface • O3 depletion has increased UV-B at Earth’s surface

15. UV-C • UV-C is 100 - 290 nm • (shortest of the UV) • Most energetic of the UVs • All is absorbed by O3 in stratosphere

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

18. Ozone should be balanced in the stratosphere constantly Except…..for the little problem of the ???

19. CFCs • Chlorofluorocarbons 

20. 4. Chlorofluorocarbon rxns • Cl3CF + UV  Cl2 + Cl • (UV light strikes the CFC and splits it, releasing chlorine.) • Cl + O3  ClO + O2 • (The chlorine reacts with ozone to produce chlorine monoxide.) • ClO + O  Cl + O2 • (The chlorine monoxide reacts with monatomic oxygen to produce chlorine again.)

21. Thus, CFCs create a chain reaction that stops the production of ozone. The chlorine is a catalyst that can be used over and over, breaking down as many as 100,000 O3 to O2.

22. CFCs • Are used during industrial processes & for refrigeration. • Are non-reactive, thus can drift for years, eventually in stratosphere.

23. 5. Antarctic O3 Depletion

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

26. Winter, continued… • Clouds of ice crystals form in stratosphere, providing surface area for CFC-O3 rxns • Clouds & winds are trapped within the vortex

27. Antarctic Spring • Increasing sunlight including UV • CFCs - O3 rxns increase • > 50% of stratospheric O3 is destroyed over Antarctica

29. As the Antarctic Spring ends… • Warming temps cause vortex to break up. • Ozone-rich air from the north floods into Antarctica • While ozone-depleted air flows northward over S. America, Australia, & New Zealand

30. 6. Ozone hole

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

35. At its “peak” in September, the ozone hole was • 27.2 million km2 in 1998 (3rd) • 29.5 mkm2 in 2000 (largest) • 28.7 mkm2 in 2003 (2nd largest) • 24.3 mkm2 in 2004 • 25.9 mkm2 in 2005

36. Why the declines? Declines may be linked to warmer winter Antarctic temperatures. Climate Change?

38. 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. • AND,

39. During the winter of 2013 – 2014, • The “Polar Vortex” wreaked havoc on most of our country (except us), bringing record storms and cold temperatures.

41. 8. Effects of O3 depletion

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

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

47. (2) Basal carcinoma

48. Basal carcinoma

49. (3) Melanoma