Ozone

Ozone (O3) is a molecule consisting of three oxygen atoms, similar to the oxygen
we breathe (O2), however oxygen consists of only two oxygen atoms. In the
stratosphere, a region high up in the upper atmosphere, light rays are
responsible for the breaking down of oxygen (O2), breathable oxygen into its two
separate oxygen atoms. Lone oxygen atoms are markedly reactive. When a lone
oxygen atom comes into contact with a breathable oxygen molecule (O2) it
combines to form ozone (O3). The ozone layer is a small residual amount of
ozone concentrated in a band in the upper atmosphere. This band of concentrated
ozone resides approximately between twenty and forty kilometers high in the
stratosphere. The ozone layer reactions that both create and destroy ozone has
come into a dynamic equilibrium. This dynamic equilibrium is very delicate and
resulted during atmospheric formation (Environment Canada, 1996). Ozone, however,
is very rare even in the ozone layer. Oxygen makes up approximately twenty
percent of air and ozone makes up only 3 x 10-5 percent of air. Furthermore,
this minuscule amount of ozone is enough to protect the earth from most
ultraviolet light. Ozone prevents most UV-B radiation from reaching the surface
of the earth (Environment Canada, 1996). Ozone is very important to life on
earth because the harmfulness of high-energy UV-B radiation stems from the high
energy of these light rays, enabling them to penetrate deeply into water, plant
tissue and epidermal tissue of animals. Increased UV-B radiation results in
harming the metabolic system of cells and ultimately damage to genetic material
present in effected cells. Living organisms on the surface of the earth have
always been exposed to some, and only slightly differing levels of UV-B
radiation depending of geographic location and season. Through evolution,
cellular repair mechanisms have evolved to safeguard cells against damage done
by UV-B radiation. With the increase in the UV-B radiation, more damage is done
to cellular functions then the natural protection system can deal with
(Environment Canada, 1996). Life on earth would more or less be void if not for
the formation of the ozone layer during atmospheric formation (Porter, 1996).
With out the ozone layer the harmful UV-B radiation would not allow the growth
of autotrophic plants, resulting in reduction in oxygen production; ultimately
the destruction of most living organisms on the earth surface would result.
Increased UV-B radiation has been linked to many incidence of increased health
problems among humans. UV-B radiation leads to increase skin cancer, eye damage,
and possible inhibition of the immune system (Health Canada). These incidence
have been noticed in humans, and it is presumed that these problems will occur
in other animals as well. Terrestrial plant life is of great vulnerability to
increased UV-B radiation, it can cause the destruction of chlorophyll in plant
leaves resulting is less growth, and ultimately reduction in crop yields, forest
annual increments and a general decline in forest ecosystem health. The UV-B
radiation also causes the potential for the decrease in the populations of
phytoplankton in the world\'s oceans, causing yet more problems when one analyzes
phytoplankton in the oceans food chain (Clair, 1996). Humans are responsible for
almost all activities and pollutants that deplete the ozone layer. Humanity has
damaged the ozone layer by adding synthetically made molecules containing both
chlorine and/or bromine to the atmosphere. Both chlorine and bromine are
attributed to ozone destruction. The most commonly know group of these are
called CFCs, chlorofluorocarbons. Chlorofluorocarbons are utilized for many
industrial and domestic applications. At the earth surface, these molecules
remain stable. However, with their release into the atmosphere they are
subject to global air currents, winds aloft and atmospheric mixing, causing them
to drift up into the stratosphere. Other chemicals such as halons, carbon
tetrachloride and methyl chloroform, also attribute to ozone depletion. However
some naturally found molecules in the stratosphere, such as nitrous oxide, also
a by product of the burning of fossil fuels, attribute to the break down of
ozone (O3). Natural factors include the quasi-biennial oscillation of
stratospheric winds which occurs approximately once every 2.3 years, and the 11
year sunspot cycle. However the observation of the sunspot cycle reveals that
the total global ozone levels should not decrease more than one to two percent
(Environment Canada, 1996). In the stratosphere such molecules are effected by
energetic UV-C radiation. UV-C radiation breaks down chlorine, freeing an atom
of chlorine (Cl). Chlorine atoms will react with ozone (O3) by splitting of one
oxygen atom to form Chlorine oxide (ClO) and Oxygen (O2). The Chlorine oxide
however will again be broken down into Chlorine and a free oxygen atom to allow
the chlorine