The document discusses ozone chemistry and ozone depletion. It provides information about the distribution of ozone in the atmosphere, with 90% located in the stratosphere. Ozone acts as a natural sunscreen and absorbs UV radiation. Certain man-made chemicals like CFCs released gases that reacted with ozone and depleted the ozone layer. The document includes a graph showing the size of the 2006 ozone hole over Antarctica.

1. Ozone Chemistry and
Ozone Depletion

2. Aurora over Halley Bay Station, Antarctica, 75.6ºS 26.5ºE
Brunt Ice Shelf, Coats Land
105 days of continuous darkness
Population: 65 in summer, 15 in winter

3. The Four Principal Layers of the Atmosphere

5. UV rays
+
=
Molecular Oxygen Ozone
Oxygen Atoms Molecule
UV rays
+

6. UV rays
+
=
Molecular Oxygen Ozone
Oxygen Atoms Molecule
UV rays
+

8. Distribution of Ozone
100 60
Thermosphere
80 50
Altitude (miles)
Mesosphere 40
60
Altitude (km)
Ozone 30
Oxygen
40
20
90% of ozone is in the stratosphere
20
10
10% of ozone is in the troposphere Troposphere
0 0
0 2 4 6 8
Ozone (parts per million)

9. Ozone is the Earth’s natural sunscreen
100 60
Thermosphere
80 UVc - 100% Absorption 50
Mesosphere
UVb - 90% Absorption
Altitude (miles)
UVa - 50% Absorption & Scattering 40
60
30
40
20
20
10
Troposphere
0 0
0 2 4 6 8
Ozone (parts per million)

11. UV radiation
CCl3F(g) ---------> CCl2F(g) + Cl(g)
Cl(g) + O3(g) ----> ClO(g) + O2(g)
ClO(g) + O(g) ----> O2(g) + Cl(g)

12. Other gases
Methyl chloroform (CH3CCl3) Other halons
3400 1% HCFCs (e.g., HCFC-22 = CHClF2) 4%
20 Halon-1301 (CBrF 3)
4% CFC-113 (CCl2FCClF2)
5%
3000 7% Carbon tetrachloride 14%
(CCl4) Halon-1211 (CBrCIF 2)
12% 15
CFC-11 (CCl3F) 20%
2000 5-20%
23% 10 Methyl bromide (CH3Br)
CFC-12 (CCl2F2)
1000
5
32% 27-42% Very-short lived gases
Methyl chloride (CH3Cl)
Natural (e.g., bromoform = CHBr3)
sources 16% 15%
0 0

15. Ozone Hole as of September 2006