Figure
1: The destruction of stratospheric ozone (6)
Effects of CFCs on environment
CFCs, when released from the surface of the Earth, rise slowly into the stratosphere.
Once there, they are bombarded by the incoming UV light from the Sun, releasing
the chlorine atoms from the parent compound, which can then react with the ozone
molecules (Figure 1). Eventually the chlorine atom is
removed from the atmosphere by other reactions.
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Figure
1: The destruction of stratospheric ozone (6) |
Chlorofluorocarbons (which are used in aerosols, refrigerants, and other industrial
products) are remarkably inert and nonreactive. Indeed, it is because of these
characteristics---specifically because they are nontoxic and nonflammable---that
they were invented. But when they eventually rise into the stratosphere, they
are decomposed by solar ultraviolet radiations into free chlorine atoms:
Chlorofluorocarbon ---> Cl,
Cl + O3 ---> ClO + O2,
ClO + O ---> Cl + O2.
The chlorine atoms are recycled in these reactions, and are then free to attack
other ozone molecules. A single chlorine atom, released by the action of UV
radiation on chlorofluorocarbons, is capable of destroying catalytically tens
of thousands of ozone molecules during its residence in the stratosphere.
The emission of chlorofluorocarbons (CFCs) from refrigerators, air conditioners,
and aerosols attributes to an increasing “hole” in the ozone layer
in the atmosphere above Antarctica, coupled with growing evidence of global
ozone depletion. (7)