CORE
SECTION A
GENERAL KNOWLEDGE
STRATOSPHERIC OZONE DEPLETION
The introduction of CFC’s and HCFC’s has dramatically changed our lifestyles. Little did we know that the use and re‐
lease of these compounds into the atmosphere would have far reaching effects on our environment. The greatest ef‐
fect is in the stratosphere, far removed from the Earth's surface.
The stratosphere is the Earth's security blanket. It is located between 7 and 30 miles above sea level and is com‐
prised of, among other things, Ozone. An Ozone molecule consists of three oxygen atoms (0
3
). Ozone protects us from
harmful ultraviolet radiation and helps maintain stable Earth temperatures. Stratospheric Ozone depletion is a global
problem. Depletion of Ozone in the stratosphere causes:
CROP LOSS
INCREASE IN EYE DISEASES
SKIN CANCER
REDUCED MARINE LIFE
DEFORESTATION
INCREASED GROUND LEVEL OZONE
CFC’s have been found in air samples taken from the stratosphere. CFC's and HCFC's, when released into the atmos‐
phere deplete the Ozone layer. The chlorine in these compounds is the culprit. When a chlorine atom meets with an
Ozone molecule, it takes one Oxygen atom from the Ozone. This forms a compound called Chlorine Monoxide (CIO)
and leaves an O
2
molecule. The Chlorine Monoxide will collide with another Ozone molecule, release its Oxygen atom,
forming two O
2
molecules, and leave the chlorine free to attack another Ozone molecule. A single Chlorine atom can
destroy 100,000 Ozone molecules.
There has been a great deal of controversy over the subject of Ozone depletion. Some believe that the Chlorine found
in the stratosphere comes from natural sources such as volcanic eruptions. However, air samples taken over erupting
volcanoes show that volcanoes contribute only a small quantity of Chlorine as compared to CFC's. In addition, the
rise in the amount of Chlorine measured in the stratosphere over the past two decades matches the rise in the amount
of Fluorine, which has different natural sources than Chlorine, over the same period. Also, the rise in the amount of
Chlorine measured in the stratosphere over the past twenty years, matches the rise in CFC emissions over the same
period.
Unlike other Chlorine compounds and naturally occurring chlorine, the chlorine in CFC's will neither dissolve in water
nor break down into compounds that dissolve in water, so they do not rain out of the atmosphere.
OZONE DEPLETION POTENTIAL
Ozone Depletion Potential (ODP) is a measurement of CFC's and HCFC's ability to destroy ozone. CFC's have the highest
ODP. HFC's (R‐134a) do not contain chlorine and have no Ozone Depletion Potential.
Type
Example
Elements
CFC
R‐11, 12, 500
Chlorine Fluorine Carbon
HCFC
R‐22, 123
Hydrogen Chlorine Fluorine Carbon
HFC
R‐134a
Hydrogen Fluorine Carbon
1
