Ozone Depletion Essay, Research Paper
Ozone Depletion And its Consequences
The life on Earth is protected from harmful radiations by ozone layer. However, this shield is being damaged day by day due to harmful human activities. This paper will emphasize on how destruction of the ozone has and can further result in dire consequences to life on Earth unless steps are taken to reduce and eradicate this situation by covering the following vital points:
+ Introduction to Ozone layer.
+ Causes of depletion.
+ Effects of depletion.
+ World s reaction.
Introduction to Ozone Layer
According to the facts given by United States Environmental Protection Agency (EPA)(1990):
The Earth s atmosphere is divided into several layers. The lowest region, the
troposphere, extends from the Earth s atmosphere up to 10 km in altitude. The next
layer, the stratosphere, continues from 10 km to about 50 km. Most of the
atmospheric ozone is concentrated in the stratosphere, about 15-30 km above the
Earth s surface.
Ozone is much less common than normal oxygen. Out of each 10-million air
molecules, about 2-million are normal oxygen but only 3 are ozone but even this small
amount of ozone plays a key role in the atmosphere. At any given time, ozone
molecules are constantly formed and destroyed in the stratosphere. The total amount,
however, remains relatively stable (par.3,2).
In explaining the role of the ozone, Close and Playford (1997) state:
The Earth s atmosphere is a vast chemical factory that continuously forms and
destroys substances, including ozone. When everything is working properly, there is a
natural balance that maintains stratospheric ozone layer as protective sun blocker and
dissipates concentration of ground level ozone that can also harm human health and
the living environment (par.3).
The major role played by the ozone is in absorbing the ultraviolet radiation from the sun, preventing it from reaching the planet s surface. The ozone s most significant role is absorbing the portion of ultraviolet radiation (UV) called UVB, which has been linked to several harmful diseases and effects (EPA, 1990).
Furthermore Close and Playford (1997) explains:
Stratospheric ozone filters out dangerous ultraviolet radiation by means of continuous
cycle in which oxygen and ozone breakdown and re-form, absorbing ultraviolet light
and releasing less damaging kinds of energy. Without enough ozone, the
effectiveness of the filter decreases and more ultraviolet radiation reaches earth
Recent measurements show that the amount of ozone in the stratosphere has decreased by about two percent since 1967.What is called the ozone hole over Antarctica actually is an area where concentrations are significantly lower than in the rest of the stratosphere. It is estimated that up to eight percent of the protective ozone layer over the United States, Canada, and Europe has disappeared. Researchers report that the seasonal hole over Antarctica and some populated regions of the Southern Hemisphere thins the ozone layer by as much as 60 or 70 percent (Close & Playford, 1997).
Kerr (1990) states that new satellite data show that the ozone shield over the United States is eroding as fast as had been assumed. Indeed the ozone is disappearing so quickly that it now looks as if the current plans to reduce the losses may be too little, too late (par.1).
Causes of Ozone Depletion
In 1974, Molina and Rowland suggested that ozone would be destroyed by catalysis of chlorine atoms and the main anthropogenic source if chlorine atoms could be chlorofluoromethanes (Urbach, 1988).
The culprit destroying the stratospheric ozone are chemicals known as chlorofluorocarbons (CFCs) and halons produced and released into atmosphere by human activity. They are very stable, and remain unchanged in the air for as long as a century. Other threats to ozone come from chemicals found in certain degreasers, adhesives, dyes, pesticides, and fungicides (Close & Playford, 1997).
There was another detection of apparent ozone destruction, this one by a group headed by Edward Browell s detected two patches of air that had up to 17% less ozone than the surrounding air. The nitrous oxide data again seemed to require chemical destruction of ozone. In addition, the altitude range of the patches, 17 to 23 km, coincided with that of the polar stratospheric clouds. In the Antarctic ozone hole, these icy clouds catalyze the production of ozone-destroying chlorine. The coincidence of ozone loss and clouds in the Arctic implies the same may be happening there (Kerr, 1990).
Despite this evidence, there are still doubters, but the link between CFCs and ozone loss was buttressed by calculation by three different groups of the amount of ozone that should have disappeared, given the chemical state of the atmosphere at its start (Kerr (1990).
There is evidence now that ozone-destroying forms of chlorine also form over the Arctic during the winter. The significance of this first chemical clue, the presence of chlorine dioxide, was hotly debated when it was first found over the Antarctic, especially by the meteorologists preferring purely wind-driven mechanisms for creating the hole (Kerr, 1988).
Just how chlorine dioxide participates in ozone destruction has been a matter of some debate. It is a by- product of a recycling of chlorine and bromide that destroys ozone. It may be a participant in another ozone-destroying catalytic cycle in which two-chlorine monoxide molecules combine to form a dimer (Kerr 1988).
Hoffman, Oltmans, Harris, Solomon, Deshler and Johnson (1992) gave evidence on possible causes of new zone depletion stating the 50% decline in stratospheric ozone levels over Antarctica in the spring of 1991 may have been brought on by the release of aerosol particles from the volcanic eruption of Mount Hudson in Aug 1991 (par.5).
Researches also attributed the depletion of tropospheric ozone in the Arctic Region to sea salt. It is hypothesized that the depletion is caused by the gasification of sodium bromide and their release into the atmosphere (Vandendorpe, 1998).
However, Vandendorpe (1998) explains:
It is not yet clear how seawater affects ozone beyond the poles. In areas that
experience traditional day and night patterns, convention heats air up to 10 km from
the ground, mixing the atmospheric chemistry and making it difficult to measure the
impact of sea salt on ozone. If proved it will affect the existing atmospheric model, as
over 70% of the world is ocean (par. 19).
Effects of Ozone Depletion
Atmospheric ozone absorbs UV light from the sun, especially in the ultraviolet range (290-320nm), and protects plants and animals from its damaging effects. Loss of ozone from the earth s outer atmosphere could have dire consequences for human and other living organisms on earth (Godlee, 1991).
Millions of people will be harmed in the future by the thinning of the global ozone layer. The extra radiation may cause skin cancer and cataracts worldwide. The ocean s plankton growth will be affected, causing damage to the natural food chain (Science News, 1991).
When concentration of this protective gas decreases by 10 % — as expected by the end of century the extra UV radiation reaching Earth s surface will cause 300,000 additional cases of skin cancer and 1.6 million additional cases of cataracts each year worldwide (Science News, 1991).
The effects on human health are mainly due to the action of ultraviolet B (UVB) on the skin and eyed (box). Sunburn and snow blindness result form acute exposure to intense sunlight. In relation between exposure to the sun and skin cancer, Godlee (1991) explains, UVB falls with in the photo absorption spectrum of DNA and, when not eliminated by the ozone in the atmosphere or melanin in the skin, it causes direct damage to DNA (par.6).
The increased level of UVB also seriously affects vegetation on land. Of some three hundred-food species tested, two-third has shown some sensitivity to UVB in terms of impaired growth. Recent research on maize has brought another hazard of increased exposure to UVB, that of jumping Mutator gene in which genes that are currently stable, start jumping from one site on the genome to another, where they cause disruption of the plant s development and fertility (Bunyard, 1999).
According to one article, plants are affected by ozone depletion. Green is the symbol of environmentalism the world over, because green is the color of chlorophyll. The chlorophyll in plants makes life on earth possible through the chemical cleverness of photosynthesis. So anything that gets rid of chlorophyll will make the planet less green in more ways than one. After years of speculation, there is now evidence that ultraviolet light coming through the hole in the ozone over Antarctica is doing that (Economist Newspaper, 1992).
Other consequences of ozone depletion are the effects on marine organisms. New studies in Antarctica show phytoplankton (tiny plants) growth slowing by 6 to 12% when ozone levels dropped 40%. These tiny plants anchor the ocean food chain so damage to them could spread throughout that chain (Science News, 1991).
Research published recently in Science suggests that the phytoplanktons are reproducing less profusely than before. Researchers also found that increased UV Still appears to be the cause of harm. Experiments carried out by taking samples of phytoplankton at several sites, some under ozone hole and some beyond its influence. They did not measure the UVB directly because it varies with the factors such as cloud cover. From the experiment they concluded that production of organic material was lowest within the Hole s influence. UVB affects phytoplankton in two ways; it interferes with photosynthesis by wrecking the chlorophyll molecules and it damages the DNA on which genes are stored, leading to problems in growth and reproduction (Economist Newspaper, 1992).
After discovering that the CFCs and halons are involved in depletion of ozone leading to the global warming, steps were taken by world nations with Vienna convention in1985 and Montreal protocol in 1987, banning the use of these chemicals. CFCs and halons are used in refrigerators, air conditioners, aerosol spray cans, plastic and rubber foam manufacture, and fire extinguishers (Urbach, 1989).
Scientists are evaluating options about how to fix the ozone hole and prevent global warming. Chemicals may be used to repair the ozone hole over Antarctica, and reforestation and reducing the number of trees cut down would reduce atmospheric carbon dioxide, a key element of global warming (Davies, 1993).
A study by Miller and Mcfarland (1996) showed that there is an agreement on evolving laws to curb emissions of harmful gases. US industry has reverted to energy efficiency means to stall carbon dioxide emission. However, developing states feel that global environmental laws will impinge on their potential for economic growth. Global warming remains a contentious issue marked by glaring discrepancies (par. 1).
However, fields like geo-engineering are built on the premises that what technology has given us — global warming and ozone depletion — it may also take away.
Davies (1993) describes that geo-engineering offers to reforest more than 28million hectares about 17,500 square miles of marginal US farmland, so tress can absorb the carbon dioxide that industry and consumers give off (par.7).
However, as usual, all the geo-engineering schemes came under attack as soon as they were announced. A main critic among them is Robert Charlson, whose work helped inspire this line of geo-engineering in the first place. Davies (1993) quotes Charlson s critics some people misinterpreted our findings, using sulfate or dust to counteract global warming is and unworkable proposition. It would require a designer sulfate and distribute it in just the right fashion. Its impossible to have that level of control (par.11).
Though the efforts are being awarded with few positive results, the road to success is far from being over. People need to be educated about how serious the problem is and only a joint effort can eradicate further damage. Man is the cause of destruction of ozone and unless the problem is solved completely, that is the ozone is completely repaired and the destruction of zone layer is stopped, there will be more severe consequences.
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