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Ozone
Depletion and the Greenhouse Effect
Structure
of the Atmosphere and the ozone layer
The
temperature of the atmosphere changes in a somewhat irregular fashion
with altitude while the pressure drops in an essentially logarithmic
fashion. The net result of this is a layering of the atmosphere.
While mixing occurs between the layers it is much slower than the
mixing within any layer.
The
"ozone layer" we are concerned with is the thin region at around
15-40km. If all of the ozone in this region was compressed to a
pressure of one atmosphere, the ozone layer would be less than half
a centimeter in thickness!
The
radiation reaching the upper atmosphere is attenuated by a number
of different species.
Ozone
is of particular interest as it absorbs between 200 and 300nm where
no other common atmospheric species absorb. This radiation is quite
harmful to biological and biochemical systems and is implicated
in skin cancer as well as a variety of other diseases.
Here
is the simplest mechanism for the formation and destruction of stratospheric
ozone. Note that the net effect of the destruction steps is to remove
odd oxygen species (O and O3) and convert them to O2.
We
know that oxides of nitrogen (NOx) are involved in ozone
destruction (remember the atmospheric nuclear testing), so here
is the original mechanism with added steps involving NOx.
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