Ozone Depletion JHans van Leeuwen Stratospheric ozone and

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

Solar Spectrum

The Ultraviolet Spectrum 400 nm Radio q UV light: 100 to 400 nm IR Visible Light 100 nm UV X-Rays l UV-A UV-B UV-C Far UV 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 300 nm 200 nm DNA damaging range

DNA Damaging Range of UV Light

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

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

Atmospheric Layers

Ozone Formation and Depletion

The catalyzed cycle of stratospheric ozone production and destruction 1. h + O 2 2 O. 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

Halogen catalysis of ozone destruction

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

Ozone Depleting Substances List of ozone depleting substances Table 8. 13 Masters http: //www. epa. gov/ozone/ods. html Halons

Antarctic Ozone Problems

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

Antarctic Reactions Winter reactions Polar vortex: -90 o. C Ice clouds Cl. ONO 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 Cl. O + O 3 destructive loop HNO 3 + Cl Cl. ONO 2 in photocatalysis

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.

Record ozone hole, 2006

Ozone hole altitude profile

Ozone hole severity

Ozone hole extent

Global total ozone change

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

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

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

Ozone Hole 2009

Ozone Hole 2009

Ozone Hole 2009

Ozone hole size in recent years

http: //www. cmdl. noaa. gov/ozwv/ozsondes/spo/ozone_anim 2004. html