Across the horizon: the rising sun and endless possibilities

Home - Studyworld Studynotes - Quotes - Reports & Essays 






Oakwood Publishing Company:


Study Material




 Ozone is an important molecule in maintaining the homeostasis in the
environment. Ozone, the molecule O3, makes a layer in the stratosphere,
situated 10 to 15  kilometers from the earth's surface. The dioxide
molecule, O2 and Oxygen atom O, collide with each other result in the
formation of Ozone, O3. In this reaction, the molecule O3 contains an excess
of energy. Once the molecule is formed, it is not stable enough to last
long. The energy-rich O3 molecules discards the excess energy by colliding
with another atom or molecule and transferring the energy in the form of
heat. In the results of the decomposition of ozone into O2 and O in the
ozone layer, solar radiation is absorbed. This process of the chemical bond
breaking causing the absorption of a photon by a molecule is called
photodissociation.  Radiation with sufficient intensity, is capable of
separating the O3 molecule, resulting in photodissociation. The cyclic
process formation and decomposition of ozone provides a shield against
ultraviolet radiation that enter the earth's atmosphere. If it were not for
the chemical reaction of radiation and ozone in the stratosphere, these
high-energy photons would penetrate the earth's surface. The ozone layer
absorbers about 99% of the harmful radiation which makes it possible for
animals and plants to live on the planet.
 In 1974, F. Sherwood Rowland and Mario Molina of the University of
California proposed that chlorine from chlorofluorocarbons (CFCs) could
deplete the ozone layer.  Beginning in 1957 to 1985, the British Antarctic
Survey had measured the average ozone concentration over  Halley Bay in
Antarctica. Up until 1974, the ozone concentration remained stable. Yet
after 1974, the team observed a decline of the ozone layer to levels less
than 10%.  From this study the awareness over the danger of the "hole" and
ultraviolet radiation and the destruction being done to the earth.
 Scientists believe the expanding ozone hole, which is centered over
Antarctica was caused by Chloroflurocarbons. CFCs are released into the
environment through such sources as  spray cans , air conditioners,
factories, refrigerants and cleaning products. CFCs are dangerous to the
atmosphere because after they are released into the environment, the
sunlight  breaks down the compound. The chlorine molecules react with the
ozone molecules by permanently breaking down the molecule, thus diminishing
the ozone layer. This rise poses a major threat environment.  In 1985, in
Vienna and in 1987 in Montreal, a Protocol was signed proposing the gradual
termination of use of CFCs over the decades.  A dramatic reduction in the
use of CFCs was agreed on.  Regulations to limit the production of
fluorocarbon-11 and fluorocarbon-12 are being implemented in a number of
nations. Yet scientist are still concerned for what the future holds.
Scientist have estimated that the average rate of ozone depletion is 0.5%
per year. For this reason, scientists are pushing for finding some option to
fix the disaster.
 Hydrofluorocarbons and hydrochlorofluorocarbons have been proposed as CFC
replacements. The atmospheric combinations expected to produce
trifluoroacetate (TFA), which is removed mainly by the rain. Yet there still
are problems which scientist are trying to sort out. The global average TFA
concentration is very low, yet there is some concerns in situations of  high
evaporation, and the affects of TFA. TFA in high concentration  could
inhibit the plant growth, a risk that could turn disastrous.
  Another harmful ozone destroyer is Mythl bromide which is used by farmers
for pests control, which is found in leaded gasoline, and Marine plants
discharge it into the air. Mythl bromide reacts the same way as
chloroflurocarbons, with the bromide molecule destroying the ozone. Why
Mythl bromide is not as much of a problem as CFCs is because bromide does
not survive as long in the atmosphere.  By 1991, CFC's had been firmly
established chlorine as the principle cause of the destruction of the ozone
molecule, but scientist are still unsure about the degree of danger that
myth bromide and other compounds pose to the ozone layer.
  To determine the depletion of the ozone layer, the National Aeronautic and
Space Administration (NASA) has been studying the stratosphere  and to
measure the concentration of ozone, aerosol particles, nitrogen oxides,
hydrogenoxied, and CFCs.   Scientist studying the effects of the depletion
of ozone agreed that there was a growing erosion in the ozone layer.
Scientist have also agreed that the ozone layer has dropped to as much as
10%.   There is a scary parallel in the rise in the amount of ultraviolet
rays and the hole in the ozone. This threatens all living things.  Scientist
have predicted a 5 to 20 percent increase in ultraviolet radiation in the
next 40 years.  Some scientists have also predicted that for every 1%
decrease in the ozone layer, there will be a 2% increase in the in incidence
of skin cancer.  The increase of ultraviolet radiation (UVR) is one of the
main risk factors for skin cancer. High exposure to ultraviolet radiation
can weaken the immune system.
 In plants, the cells are damaged by the rise in ultraviolet radiation. With
the continuing rise in ultra-violet B radiation (different frequency 280-320
nm) plants have become the next victims. In plants, there are several
targets for UV-B rays. UV-B rays  slow down the photosynthesis,
productivity, and growth in plants. Such affects could mean 20% to 25%
decrease in crop yields.  UV-B rays directly damages the plants DNA in the
chloroplast.  From absorption of the high energy photons, the plant becomes
damaged . For the increasing levels of UV-B rays and UV-A rays, farmers
worry about the highly possible reduction in yields.
 Scientists have done a lot to research a problem that has been recently
been discovered. In the understanding of how the ozone layer works, and it^Òs
importance, finding a way to stop the depletion of the ozone layer has
become necessary. The Ozone layer is essential for their to be life on
earth. All living things can not live in an environment of high radiation.
For this science and humans are looking for ways to fix the problem.

walkingman.gif (5600 bytes)

Copyright © 1996-2008 Studyworld



Teacher Ratings: See what

others think

of your teachers

Copy Right