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

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Presentation on theme: "Ozone Depletion Stratospheric ozone and its importance J(Hans) van Leeuwen – The hole story."— Presentation transcript:

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

2 Solar Spectrum

3 The Ultraviolet Spectrum  UV light: 100 to 400 nm UV spectrum – 4 regions o Far UV: 100 – 200 nm o UV – C : 200 – 280 nm o UV – B : 280 – 315 nm o UV – A : 315 – 400 nm RadioIR Visible Light UVX-Rays UV-AUV-BUV-C Far UV 400nm100nm DNA damaging range 200nm300nm

4 DNA Damaging Range of UV Light

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

6 UV ozone generation and destruction: equilibrium O 2 + h  185  2O. O. + O 2 + M  O 3 + M O 3 + h  254  O 2 + O. Equilibrium between production and destruction

7 Atmospheric Layers

8 Ozone Formation and Depletion

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10 The catalyzed cycle of stratospheric ozone production and destruction 1.h  + O 2  2O. 2.O. + O 2  O 3 3.O 3 + X  O 2 + OX 4. OX + O.  O 2 + X X could be Cl from a CFC

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12 ozone: Halogen catalysis of ozone destruction

13 Halogen removal from atmosphere Cl + CH 4  HCl + CH 3. ClO + NO 2  ClONO 2 Both HCl and ClONO 2 inactive: rain out Br + O 3  BrO + O 2 Br + CH 4  HBr + CH 3. HBr can photolytically provide Br again Halons and CH 3 Br provide Br

14 List of ozone depleting substances Table 8.13 Masters Ozone Depleting Substances Halons

15 Antarctic Ozone Problems

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

17 Antarctic Reactions Winter reactions Polar vortex: -90 o C  Ice clouds ClONO 2 + H 2 O  HOCl + HNO 3 HOCl + HCl  Cl 2 + H 2 O Spring reactions Cl 2 + h   2 Cl in early spring Cl + O 3  ClO + O 3 destructive loop HNO 3 + Cl  ClONO 2 in 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

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21 Ozone hole altitude profile

22 Ozone hole severity

23 Ozone hole extent

24 Global total ozone change

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

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39 Ozone Hole Growth: 29y October 27, 1980 September 21, 2006September 17, 2009

40 Ozone Hole 2009

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44 Ozone hole size in recent years

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