Ozone Depletion

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