Essay/Term paper: The ozone layer

Essay, term paper, research paper:  Science Research Papers

The Ozone Layer


In environmental science the green house effect is a common term for the
role water vapor; carbon dioxide and ozone play in keeping the earth"s surface
warmer than it would normally be. The atmosphere is primarily transparent to
infrared radiation from the sun, which is mostly absorbed by the earth"s surface.
The earth being much cooler than the sun, remits radiation most strongly at
infrared wavelengths. Water vapor, carbon dioxide and ozone then absorb much of
this radiation and remit a large proportion back towards the earth. The
atmosphere thus acts as a kind of blanket: without its presents the earth"s
average ground temperature of 15 degrees Celsius would fall to -28 degrees
Celsius. The termed greenhouse effect implies that a comparable effect keeps
the interior of the green house warm. Actually, the man role of the glass in a
green house is to prevent convection currents from mixing cooler air outside
with the warmer air inside.
Although water is the most important factor in the greenhouse effect, is
a major reason why human regions experience less cooling at night than do dry
regions. Changes in both water and carbon dioxide play an important role in
climate changes. For this reason many scientist have expressed concerns over
the global increase of carbon dioxide in resent decades, largely as a result of
the burring of fossil fuels. In many other factors of the earth"s present
climate remain more or less constant, the carbon dioxide increase should raise
the average temperature at the earth"s surface. Because warm air can contain
warm water before reaching saturation than cooler air can, the amount of water
would probably increase as the atmosphere got warmer . This process could go on
forever. Although this considered unlikely many negative feed backs could as so
occur, such as increase in cloud cover or increase carbon dioxide absorption
by the oceans, the results of even a limited rise in average surface temperature
remains sufficiently dramatic to justify concern.
In October 1983 the US Environmental Protection Agency released a report
that projected the irreversible onset of the greenhouse effect by the 1990"s.
Shortly there after the National Academy of Sciences issued its own report, in
which the matter of irreversibility remain more in question. Both reports,
however, strongly indicated the need for measures to check the rise in carbon
dioxide.
No matter what term you use global warming or greenhouse effect, they
both play a major role in the earth"s climate. Climate researchers are
attempting to predict, based on ocean and air circulation, how great an increase
there will be. If global warming continues then the polar ice caps will melt and
most of the earth will be flooded and a lot of lives will be lost.
The Ozone is located in the stratosphere, approximately 10 km - 50 km
above the earth. The density of ozone gas at zero degrees Celsius is 1 ATM.
The Ozone is relatively unstable form of molecular oxygen containing three
oxygen atoms (O ). Radiation from the sun continuously bombards the Earth"s
atmosphere, causing molecules to break apart into component elements that form
into new chemical compounds. Ozone is produced when upper-atmosphere oxygen
molecules (O ) are broken apart by ultra-violet light. Most of the freed oxygen
atoms immediately bond with nearby oxygen molecules to form ozone (O + O =O ).
The only method used to make commercially is to pass gaseous oxygen or air
through a high voltage alternating-current electric discharge called a silent
electric discharge. Ozone near the earth"s surface is generally regarded to as
a bad . It is created from industrial, transportation, and some natural
sources. It is the most noxious component of smog. All high concentration, 0
is known to reduce human lung capacity, as well as damage the cells of many
plants, animals, and other organisms. For these reasons, ozone is treated as
and air pollutant in most industrial countries. Furthermore, O in the upper
troposphere is a powerful greenhouse gas and is believed to play a role in
global warming.
On the other hand, ozone in the stratosphere is highly valued. It
serves as a protective radiation shield that interprets solar ultraviolet light
harmful to living things. Ultraviolet light splits the relatively unstable O
molecules into O and atomic O. Most of the time, the O atom created by Ozone
breakup recombines with one of the plentiful O molecules to re-form O . This
Ozone-creation process is constantly at work producing more ozone. Scientist
can"t predict with certainly the consequences for life on the earth if the
stratosphere ozone layer weakens. In general, biologists and health
professionals recognize that life on earth enveloped under the protection of an
ozone layer thick enough to remove much of the UV-B solar radiation known to
damage cellular organisms. Accordingly, various organisms--including humans--
may have difficult adjusting to the higher UV-B levels resulting from a thinner
ozone Layer.
Medical studies have quantified some of the expected effects of
increased UV-B levels, based on real-life information form people exposed to
greater than average UV-B levels--populations living at high altitudes and in
the tropics, where the average ozone layer is thinner and the sunlight more
direct. The most serious medical effects include increased incidence of
cataracts and skin cancer, as well as evidence of weakened immune-system
response. Ecological research indicated that some crop yields will decrease and
disruption in marine food chains may occur.
A weakened ozone layer may also case climatological effects. The
stratosphere warms with altitude because the splitting of stratospheric ozone is
caused by ultraviolet photons, which contain much more energy than that required
to break the O-O bond. This extra energy is converted to heat. Less
stratospheric ozone means less local heating, but it also means that more UV
light is transmitted to heat the lower atmosphere and the earth"s surface.
Ozone can be destroyed by chemicals that react directly with it, or by
those that react with the oxygen atom temporarily freed whenever an o molecule
breaks apart. However, since ozone concentrations are higher than those of most
reactive chemicals in the stratosphere, the only ozone destroyers of concern are
those that can participate in a "catalytic cycle" that is, where one trace
catalytic chemical can be responsible for destroying terns or even hundreds of
thousands of ozone molecules.
In the last few years, various human activities have released ozone -
destroying chemicals into the atmosphere. Of Particular importance are halogen
atoms -- chlorine and bromide. Chemicals release into the ozone by industrial
particles include chlorocarbon compounds (such as CCL and CHI CL ),
chloroflucarbon compounds CFCs and halon compounds.
Chlorocarcon compounds are used primarily as industrial solvents,
degreasing compounds, and CFC precursors. The CFCs are used as working fluids
in refrigeration and air conditioning units. Aerosol propellant agents. The
Halons are used as fire suppressants. Once in the stratosphere, all these
chlorine and bromine containing compounds are broken apart by solar ultraviolet
radiation, releasing their Cl or Br atoms. These atoms start the process of
Ozone destruction. Each Chlorine of Bromine atom that starts the destruction
cycle can destroy 100,000 ozone molecules. There are on the other hand natural
ozone depletes such as volcanic eruptions.
A hole in the Ozone has emerged because of all of the depletion.
Starting in the spring of 1980, a massive 8.2 square mile ozone hole accounting
for one quarter to one half the appeared over the continent of Antarctica. For
the past 16 years the hole has grown larger. There was a theory that predicted
that the most severe O loss would occur relatively high in the stratosphere
above 30 km). It was called the Roland/Molina theory. In fact the largest
depletion over Antarctica occurred in the middle range between 13 and 21 km.
Atmospheric chlorine and bromine levels are expected to peak around 1998.
There are currently steps being made to protect the ozone. One such
step is the 1987 Montreal Protocol on substances that harmed the ozone. 37
nations signed the bill, it read that the signing nations cut down on the use of
chlorofluorocarbons and to completely stop CFC emissions by the year 2000. In
general people are waking up to this serious problem; as well they should. The
more ozone that is destroyed the more UVA rays and UVB rays that reach the earth.
It is hypothesized that by the year 2086 if depletion continues at the current
rate that no living organism will be able to survive on on earth unless they
are underwater.
Ozone is debatibly the most important thin known man. The survival of
the human race is really dependent upon the ozone layer. If we keep using these
dangerous chemicals, such as CFC, found in arisol cans, we could ultimatly
destroy the ozone layer. If we destroy the ozone layer then we are really
killling ourselves. If the ozone layer is destroyed then powerful ultriviolent
rays will penitrate the earth and everyone would get skin cancer and eventually
die. I hope organizations will continue to work to prevent the distruction of
ozone because I would like to see man survive for a while.