ozone depletion
DESCRIPTION
J(Hans) van Leeuwen. Ozone Depletion. – The hole story. Stratospheric ozone and its importance. Solar Spectrum. 400nm. 100nm. Visible Light. Radio. IR. UV. X-Rays. l. Far UV. UV-A. UV-B. UV-C. 300nm. 200nm. DNA damaging range. The Ultraviolet Spectrum. - PowerPoint PPT PresentationTRANSCRIPT
Ozone Depletion
Stratospheric ozone and its importance
J(Hans) van Leeuwen
– The hole story
Solar Spectrum
The Ultraviolet SpectrumThe 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
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
Radio IR Visible Light
UV X-Rays
UV-A UV-B UV-C Far UV
400nm 100nm
DNA damaging range
200nm300nm
DNA Damaging Range of UV LightDNA Damaging Range of UV Light
Ultraviolet Radiation230-280 nm damages nucleic acidsStops reproduction of cells by breaking apart the DNA bondsOzone production peaks at 185nm Ozone absorbance and destruction at 200-320nm
Ozone destruction Ozone formation
UV ozone generation and destruction: equilibrium
O2 + h185 2O.
O. + O2 + M O3 + M
O3 + h254 O2 + O.
Equilibrium between production and destruction
Atmospheric Layers
Ozone Formation and Depletion
The catalyzed cycle of stratospheric ozone production and destruction
1. h + O2 2O.
2. O. + O2 O3
3. O3 + X O2 + OX
4. OX + O. O2 + X
X could be Cl from a CFC
ozone:
Halogen catalysis of ozone destruction
Halogen removal from atmosphere
Cl + CH4 HCl + CH3.
ClO + NO2 ClONO2
Both HCl and ClONO2 inactive: rain out
Br + O3 BrO + O2
Br + CH4 HBr + CH3.
HBr can photolytically provide Br againHalons and CH3Br provide Br
List of ozone depleting substances Table 8.13 Masters
http://www.epa.gov/ozone/ods.html
Ozone Depleting Substances
Halons
Antarctic Ozone Problems
Strong circulatory winds around Antarctica isolate the air in the lower and middle stratosphere
Ice crystals form in vortex
Antarctic Vortex during Winter
Antarctic Reactions
Winter reactions Polar vortex: -90 oC Ice clouds ClONO2 + H2O HOCl + HNO3
HOCl + HCl Cl2 + H2O
Spring reactions Cl2 + h 2 Cl in early spring
Cl + O3 ClO + O3 destructive loop
HNO3 + Cl ClONO2 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
"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
1933 - 1943 - 1927 -
Paul J. Crutzen Mario J. Molina F. Sherwood Rowland
Ozone Hole Growth: 29y
October 27, 1980 September 21, 2006 September 17, 2009
http://www.youtube.com/watch?v=brblHxZctsA
Ozone Hole 2009
Ozone Hole 2009
Ozone Hole 2009
Ozone hole size in recent years
http://www.cmdl.noaa.gov/ozwv/ozsondes/spo/ozone_anim2004.html