Ozone Depletion: an Example of Pollution Effects on a Global Scale

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Ozone Depletion an Example of Pollution Effects
on a Global Scale
Air pollution can expand beyond a regional area
to cause global effects. The stratosphere is the
layer of the atmosphere above the troposphere,
that is, between 10 miles and 30 miles above sea
level. The stratosphere is rich in ozone, the
same ozone that acts as a pollutant when found at
lower levels (troposphere) of the atmosphere in
urban smog.
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UV-B is stopped here by the ozone layer in the
stratosphere ?
Polluting ozone is found here
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Ozone Depletion
Up at the stratospheric level ozone forms a
protective layer that serves a vital function it
absorbs the wavelength of solar radiation known
as ultraviolet-B (UV-B) associated with sunburns
and skin cancers.
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Ozone Depletion
Several pollutants attack the ozone layer. Chief
among them is the class of chemicals,
chloro-fluoro-carbons (CFCs). CFCs are used as
refrigerants (notably in air conditioners), as
agents in some manufacturing processes, and
formerly as propellants in spray cans.
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Ozone Depletion
In the stratosphere, intense UV radiation breaks
the CFC molecules apart, releasing the chlorine
atoms. These chlorine atoms then react with ozone
(O3), breaking O3 down into ordinary oxygen
molecules (O2). The chlorine acts as a
catalystthat is, it takes part in several
chemical reactionsyet at the end emerges
unchanged and is able to react again.
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Ozone Depletion
The chlorine acts as a catalystthat is, it takes
part in several chemical reactionsyet at the end
emerges unchanged and is able to react again.
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Ozone Depletion
So . . . because of pollution, the protective
ozone layer in the stratosphere is thinning. In
the Antarctic, the ozone layer essentially
vanishes entirely for a few weeks every
year. Fortunately, CFC use has greatly decreased.
However, CFC molecules that have already been
released into the lower atmosphere (that is, the
troposphere) will be making their way up to the
stratosphere for decades. So, further O3 loss
(the hole in ozone layer) is expected. As a
result, one can anticipate an increase in skin
cancers, cataracts (clouding of the lens of the
eye), and reduced yields of some agricultural
crops.