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History of Ozone

History of Ozone. Discovered in 1840 by Christian Friedrich Schönbein . In the 1920’s Gordon Dobson made the first O 3 column measurements. 1 DU = 1x10 -3 m thick layer of pure ozone at standard temperature and pressure.

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History of Ozone

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  1. History of Ozone • Discovered in 1840 by Christian Friedrich Schönbein . • In the 1920’s Gordon Dobson made the first O3 column measurements. 1 DU = 1x10-3m thick layer of pure ozone at standard temperature and pressure. • In 1930 Sydney Chapman proposed a mechanism for ozone in the stratosphere.

  2. The Stratosphere from: http://okfirst.ocs.ou.edu/train/meteorology/graphics/VertTP.gif

  3. Ozone in the Stratosphere • Shields the surface of the Earth from harmful UV radiation. From: http://www.atmosphere.mpg.de/enid/208.html

  4. Ozone in the Stratosphere From: Jacob

  5. The Chapman Mechanism

  6. The Chapman Mechanism From: Jacob

  7. The Chapman Mechanism (2) fast (3) (1) slow O2 O O3 (4) slow

  8. The Ox Family • Reaction 1: Production of Ox • Reaction 4: Loss of Ox

  9. The Chapman Mechanism Assuming steady-state for either O or O3:

  10. The Chapman Mechanism Everywhere in the stratosphere

  11. O3 in the Stratosphere Derive an expression for the steady-stateof O3 in the stratosphere: Find steady-state for O

  12. O3 in the Stratosphere

  13. O3 in the Stratosphere From: Jacob

  14. Catalytic Ozone Destruction X is a catalyst and may be: X = H, OH, NO, Cl, or Br

  15. z T The HOx Family in the Stratosphere • Source: Water vapor • Source: methane, H2 stratosphere cold trap, T≈190K PH2O≈2.5x10-4 torr at 75mbar (3.5ppmv) tropopause troposphere

  16. The HOx Family in the Stratosphere

  17. Catalytic Ozone Destruction (HOx)

  18. Catalytic Ozone Destruction (HOx) Cycle II Cycle I • Cycle I: important at higher z and only during the day • Cycle II: important at lower z and also at night

  19. Catalytic Ozone Destruction (HOx) • Termination occurs when: • H2O and HNO3 may mix back to the troposphere and be removed. • However:

  20. The NOx Family in the Stratosphere • Source: N2O • Source: Direct emissions of NO to the stratosphere only about 5%

  21. Catalytic Ozone Destruction (NOx) Active in the daytime -reaction scheme should look familiar?! Active in the day or night -a little different than cycle II To complete the catalytic cycle in the daytime

  22. Null Cycles Ox Ox ‘Null cycles’ do not lead to the formation or destruction of O3. -ties up reactive species (in this case, NOx) reducing their ability to destroy ozone.

  23. Catalytic Ozone Destruction • Cycles may be ‘short-circuited’ through competing reactions: Leads to O3 destruction Leads to null cycle

  24. Catalytic Ozone Destruction (NOx) • Termination of catalytic cycles occur when: • However:

  25. Reservoirs • For NOx: • HNO3, and N2O5 are reservoirs of NOx • NOy = NOx + reservoirs • NOx/NOy gives us an idea of how effective NOx is at destroying ozone. • For HOx: • H2O and HNO3 are reservoirs of HOx • HOy = HOx + reservoirs • HOx/HOy gives us an idea of how effective HOx is at destroying ozone.

  26. Mixed Cycles • The HOx and NOx cycles are coupled: An increase of stratospheric HOx causes a decrease in the effectiveness of NOx towards destroying O3.

  27. Transport in the Stratosphere From: http://www-as.harvard.edu/people/faculty/djj/book/powerpoints/

  28. Global Ozone Distribution From: http:woudc.ec.gc.ca/e/ozone/Curr_allmap_g.htm

  29. Global Ozone Distribution From: http:woudc.ec.gc.ca/e/ozone/Curr_allmap_g.htm

  30. Tropospheric NOx and HOxversusStratospheric NOx and HOx • In the troposphere (ozone production): • In the stratosphere (ozone destruction): HOx The troposphere has extremely low atomic oxygen concentrations. NOx The stratosphere has high ozone and atomic oxygen concentrations relative to the troposphere. HOx NOx

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