The ozone layer in the stratosphere absorbs most UV light from the sun. Ozone is formed when oxygen molecules are split by UV light or lightning, then join with other oxygen molecules to form ozone (O3). Chlorofluorocarbons (CFCs) used in refrigerants and air conditioners were depleting the ozone layer as they take 10-20 years to break down in the stratosphere, and each chlorine atom can destroy 100,000 ozone molecules. This was causing seasonal thinning of the ozone layer over Antarctica, known as the ozone hole. Thinning of the ozone layer allows more harmful UV-B radiation to pass through, which can damage DNA and

1. Ozone
O3

2. The Ozone Layer
absorbs most of
UV light from
sun in
stratosphere.

3. How ozone is formed
UV or lightning
splits an oxygen
(O2) - these join
other O2 to form O3

5. Ozone Eaters
1. CFCs
(Chlorofluorocarbons):
CClF3
qcoolants in refrig. &
a.c.

8. Breaking apart CFCs
qtakes10-20 yrs for
CFC molecules to
reach stratosphere

9. Breaking apart CFCs
q1 Cl atom can
destroy 100,000
ozone
molecules!

11. The Ozone Hole
ozone thinning
over
Antarctica

13. Sept 2006

14. Sept 2007

15. Dec 2007

16. Solar Radiation Types
1. UV-A – milding
irritating
2. UV-B – most harmful to
organisms
3. UV-C – deadly ; does
not reach Earth’s
surface

17. Effects of Ozone Thinning
1. More UV light passes
through, damaging
DNA, causing
mutations, skin
cancer, cataracts.

19. Effects of Ozone Thinning
2. UV-B – kill some
species of plants
and microbes

20. Effects of Ozone Thinning
-Limiting factor for coral
communities
-Reduced productivity of
aquatic ecosystems