Stratospheric Pollution
Stratospheric Pollution
The upper
stratosphere consists of considerable amount of ozone (O3), which
protects us from the harmful ultraviolet (UV) radiations (λ 255nm) coming from
the sun. These radiations cause skin cancer (melanoma) in humans. Therefore, it
is important to maintain the ozone shield.
Ozone in the
stratosphere is a product of UV radiations acting on dioxygen (O2)
molecules. The UV radiations split apart molecular oxygen into free oxygen (O)
atoms. These oxygen atoms combine with the molecular oxygen to form ozone.
Ozone is
thermodynamically unstable and decomposes to molecular oxygen. Thus, a dynamic
equilibrium exists between the production and decomposition of ozone molecules.
In recent years, there have been reports of the depletion of this protective
ozone layer because of the presence of certain chemicals in the stratosphere.
The main reason of ozone layer depletion is believed to be the release of
chlorofluorocarbon compounds (CFCs), also known as Freon. These compounds are
nonreactive, non flammable, non toxic organic molecules and therefore used in
refrigerators, air conditioners.
In the
production of plastic foam and by the electronic industry for cleaning computer
pars etc. once CFCs are released in the atmosphere, they mix with the normal
atmospheric gases and eventually reach the stratosphere. In stratosphere, they
get broken down by powerful UV radiations, releasing chlorine free radical.
The chlorine
radical then react with stratospheric ozone to form chlorine monoxide radicals
and molecular oxygen.
The chlorine
radicals are continuously regenerated and cause the breakdown of ozone. Thus,
CFCs are transporting agents for continuously generating chlorine radicals into
the stratosphere and damaging the ozone layer.
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