1. Mary Lam
Fall 2011

2. What is Ozone?
 Molecule containing three oxygen atoms
unstable with respect to O2
 Blue in color and has a strong odor
 Very reactive gas, and even at low
concentrations it is irritating and toxic
 Very powerful oxidizing agent

3. Ozone
 Occurs naturally in small amounts in
upper atmosphere and in the air of the
lower atmosphere after a lightning
storm.
 Oxidizes many organic compounds
 Powerful germicide, used to sterilize air
and drinking water

4. Formation of Ozone
 Ozone can be formed when a mixture of
O2 and NO2 is exposed to bright light.
 Such mixtures occur in the polluted air
of large cities.

5. Earth’s Atmosphere
 Found in layers
- Troposphere: lowest region, extends
from the Earth's surface up to about 10
kilometers (km) in altitude.
-The next layer, the
stratosphere, continues from 10 km to
about 50 km.

6. Environmental Issues
 Photochemical
“smog”/ pollution
 Health problems
 Greenhouse gas
 Loss of ozone
layer

7. Ground-Level Ozone
 In the
troposphere, ground-level
or "bad" ozone is a
pollutant that is a
significant health risk
 It damages crops, trees
and other vegetation. It is
a main ingredient of
urban smog.

8. Ozone Pollution
 A concern during the summer months
because strong sunlight and hot weather
result in harmful ozone concentrations

9. Ozone Alert
 The concentration of ozone in the air can
reach levels that are dangerous for plants
and animals.
 The U.S. Environmental Protection Agency
characterizes ozone levels as "unhealthful"
when they exceed the National Ambient Air
Quality Standard of 125 parts per billion
(ppb).
 In addition to posing a threat to health,
ozone in the air also damages polymeric
materials such as rubber and plastics,
causing them to deteriorate prematurely.

10. Stratosphere
 Most atmospheric ozone is concentrated
in a layer in the stratosphere

11. Stratospheric Ozone
 The stratosphere, or "good" ozone layer
protects life on Earth from the sun's
harmful ultraviolet (UV) rays.
 Was gradually depleted by man-made
chemicals like chlorofluorocarbons
(CFCs).
 A depleted ozone shield allows more UV
radiation to reach the ground.

12. Greenhouse Gas
 The increases  Ozone is also a greenhouse gas in
in primary the upper atmosphere
greenhouse and, therefore, plays a role in Earth's
gases, such as climate.
carbon
dioxide, may
affect how the
ozone layer
recovers in
coming years.

13. Ultraviolet Radiation Protection
 Absorbs a portion of the radiation from
the sun, preventing it from reaching the
planet's surface
 Most importantly, it absorbs the portion
of ultraviolet light called UVB.
 UVB has been linked to many harmful
effects

14. Ozone-Depleting substances
(ODS)
 Chlorofluorocarbons (CFCs)
 Other chlorine-containing compounds
include methyl chloroform, a solvent,
and carbon tetrachloride, an industrial
chemical.
 Halons, extremely effective fire
extinguishing agents, and methyl
bromide, an effective produce and soil
fumigant, contain bromine.

15. Chlorofluorocarbons
 Stable, low in toxicity, and inexpensive
to produce
 Noncorrosive, nonflammable
 Used as refrigerants, solvents, foam
blowing agents, and in other smaller
applications
 Used in fire extinguishers, as propellants
in aerosols, solvents in electronics
manufacture, and as foaming agents in
plastics.

16. Ozone Depletion
 The CFCs are so stable that only
exposure to strong UV radiation breaks
them down.
 When that happens, the CFC molecule
releases atomic chlorine.
 One chlorine atom can destroy over
100,000 ozone molecules. The net effect
is to destroy ozone faster than it is
naturally created.

17. CFC’s
 http://www.youtube.com/watch?v=I1wrEvc2URE

18. Ozone Hole
 An annual ozone “hole” has been
documented over Antartica every spring
since the early 1980s.
 Ozone depletion is focused mainly over
Antarctica, and to a lesser degree the
North Pole.

19. Montreal Protocol
 Discontinue the production of
CFCs, halons, carbon tetrachloride, and
methyl chloroform and industry has
developed more "ozone-friendly"
substitutes.
 Montreal Protocol is widely considered
to be the most successful of the global
environmental treaties.
 The ozone layer is expected to recover
over the next 50 years or so.

20. If CFC’s Weren’t
Regulated…
 http://www.youtube.com/watch?v=P-
VZ3q7tbag

21. Expected Learning
Outcomes
 Discuss the differences between “good”
and “bad ozone”
 Discuss how ozone is produced by
human activity
 Discuss the Montreal Protocol

22. Bibliography
 http://scifun.chem.wisc.edu/chemweek/ozo
ne/ozone.html
 http://www.ozonelayer.noaa.gov/science/ba
sics.htm
 http://www.epa.gov/oar/oaqps/gooduphigh/
bad.html#6
 http://www.oar.noaa.gov/climate/t_ozonelay
er.html
 http://www.eoearth.org/article/Montreal_Pro
tocol_on_Substances_that_Deplete_the_O
zone_Layer