Ozone Layer Depletion

Ozone is a natural trace component of the atmosphere. It is created continuously through the action of sunlight and oxygen in the upper atmosphere. At the same time this destroyed by various reactions with other components in the air. The next result of these natural processes is the so-called ozone layer in the stratosphere at altitudes between 15 and 50 kilometers in which the concentration of the ozone is raised. Ozone is a colorless gas, a form of oxygen. However, an ordinary molecule of oxygen contains two atoms. Because of ozone’s composition, it is reactive. It readily combines with whatever materials it comes in contact with, including such biological Far above the earth, ozone forms naturally as oxygen produced from living things moves from the troposphere, the layer of air nearest to the earth surface, to the stratosphere.

Air in the stratosphere absorbs solar energy, or heat from the sun, which in turn creates a photochemical reaction that produces ozone – a benefit to the environment since ozone protects people, plants, and animals from harmful radiation (Health effects of….). The ozone layer is important because it absorbs most of the damaging ultra-violet radiation from the sun before it reaches ground level, where it can cause sun burn, skin cancer and cataracts. Research suggests that any additional UV-B (ultra-violet radiation) at ground level could depress our bodies’ immune systems, damage the natural food chain and reduce crop yields. Although ozone makes up less that 1ppm of all the gases in our planet’s atmosphere, but it is essential to life on earth. Scientists assume that in the early days of the earth’s evolution there was no atmosphere, but gases from planet surfaces and volcanoes slowly collected.

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At first, the gas was little protection from the sun’s UV radiation. But according to some evolutionary theories, life forms on earth may have been able to develop in water that filtered out most of the UV rays but allowed enough visible lights for chemical reactions to take place. However, ozone concentration are not static, winds transport, ozone throughout the stratosphere. Although the photochemical process constantly produces ozone, it is also destroyed by chemical reactions involving such gases as nitrogen, hydrogen, and chlorine. In addition, the amounts of ozone change with seasons. The end results, is that over centuries ozone in the stratosphere has maintained a dynamic equilibrium: the production and loss processes have balanced. Keeping a layer of ozone around the planet that protects all life from too much UV radiation.

However, that delicate balance now may be threatened. Why did scientist become concerned about the ozone layer? A number of events prompted scientific research into the possibility that the ozone layer might be in danger. The research on the stratospheric effects of shuttle launches altered others in the scientific community and in government agencies to view chlorine compounds as possible threats to the ozone layer. Damage to the ozone layer is largely caused by the release of certain volatile chemicals in the halogenated hydrocarbons groups into the air. These are compounds of carbon and hydrogen which some or all the hydrogen atoms have been replaced by halogens, such as fluorine, chlorine and bromine.

Aquatic life could be endangered by ozone depletion. Although some aquatic species such as anchovy larvae have developed a tolerance for increased UV radiation, greater ozone depletion might result in abnormal development of larvae or kill of larvae, which are used worldwide in animal feeds. There is some speculation that organism such as blue green algae that are unharmed by UV light could dominate aquatic system. Other direct effects of increased UV radiation include damage to various polyvinyl or plastic materials used in construction. UV radiation discolored rigid vinyl home sliding, and it also may cause vinyl pipelines to become brittle, leading to more serious problems if say, natural gas pipes should leak or burst. Indirectly, added UV radiation is expected to stimulate climatic condition that promotes smog ozone pollution.

Studies show that ozone concentration would peak earlier in the day and at greater distances from the source, with the result that a larger human population would be exposed at risk. Gases that help destroy atmospheric ozone also play a part in another environmental problem, the gradual warming of the earth due to an enhanced greenhouse effect. Is a process by which the sun’s infrared rays hit the earth’s surface and then radiate heat back in the Some heat escapes into space but the rest is trapped by naturally occurring carbon dioxide and other gases that act somewhat like the glass of a greenhouse surrounding the earth, keeping it warm. Without the warming, the planet would be too could to sustain life. But human activities have loaded the atmosphere with carbon dioxide, CFCs, and such gases as methane and nitrous oxide.

Creating an imbalance in the climate system – an enhanced or forced greenhouse effect, which scientists predict could, by the middle of the next century, make the earth warmer than it has been in the last two million years.Another greenhouse effect gas is methane, which comes from the cattle waste, termite nests, and rice paddies. In 1987, atmospheric chemists at the University of California released a report showing that methane had steadily increased in the troposphere and measured 1,7ppm, 11 percent higher than a decade before and 2,4 times higher than it has been over the past 160.000 years (Grave threat to….).

Atmospheric scientist are looking at the possibility that increased cattle raising, increases the amount of acreage worldwide devoted to rice planting, and an explosion of termite populations which thrive in areas where vast tropical forests have been burned away may account for some of the rise in the methane levels. But no one is certain what all the methane sources contributes to global warming, although its effect is probably much greater than once thought. In addition, there have always been warming and cooling trends and it is possible that the hot years of the 1980s could give way to a cooler cycle. Since the late 1800’s for example, there have been fluctuations in decade averages for temperature. Although temperatures rose steadily until the 1980s, they dropped slightly over the next two decades. Still it appears that unless changes are made to cut back the emission off greenhouse gases, they will continue to build up in troposphere.

This in turn will indirectly affect the abundance of stratospheric ozone – by modifying the temperature structure of the atmosphere and hence the rates of ozone destruction. Warmer temperatures in the troposphere are predicted to lead to colder temperatures in the stratosphere, which would allow ice clouds to develop beyond the Polar Regions, providing the surface for additional ozone. Since increased ozone loss allows more UV radiation to reach the earth, not only warming trends would continue but also the effects of harmful Theory states that CFCs in aerosol spray cans could be destroying the ozone layer. The public reacted quickly, flooding congress with mail and telephone calls urging a ban on CFC aerosols. The federal government sponsored a study that confirmed the hazard posed by CFCs, which led to their eventual ban on aerosol spray cans.

Now spray can contain other type of propellant, and to assure consumers that a touch if the spray value will not add to the CFC burden in the stratosphere, some of manufacturers even paste labels on the can. Because of the CFC aerosol ban, Americans generally were convinced that the ozone layer had been adequately protected. The stratospheric ozone problem was out of sight and out of mind, as far as the public consciousness was concerned, few people seemed concerned about the possibility of ozone losses. Nevertheless, studies of stratospheric ozone loss continued, and in the late 1970s the EPA planned to ban non-aerosol use of CFCs and halons. In addition, other federal agencies were analyzing data and developing reports on the ozone depleting effects of various Since studies during the late 1970s and early 1980s suggested that the ozone layer might not be in as a great a danger as once believed.

One report from the National Academy of Sciences, indicated that human and naturally produced compounds, such as carbon dioxide, methane and nitrogen oxides, in the atmosphere could help to slow down the depletion of ozone, and might even raise the ozone level in the stratosphere one percent by the next century. CFC manufacturers have argued as well that a freeze or cutback in U.S. production of CFCs will make little difference unless there is a worldwide restriction on the chemicals. Many other nations not only make wide use of CFCs but some have increased production of these chemicals for a variety of purposes. U.S. manufacturers do not want to be singled out for cutbacks while industries in other parts of the world continue to enjoy profits from products that contain CFCs.

While policies to control ozone-depleting chemicals and greenhouse gases were swinging in and out of favor in the United States, directors of the United Nations Environment Program (UNEP) called for worldwide restriction of CFC use. Along with the United States, Japan, and Western European countries, including Britain, West Germany, and France, are major producers and the Soviet Union have been increasing their CFC use during the latter part of the 1980s. The next step would be convincing the participating nations to sign a protocol or a draft for a treaty that would regulate use of CFCs and halons on a global scale. According to Science News magazine report, manufacturers of CFCs and halons are using two methods to develop substitute products that will not be a threat to the ozone layer.

One method involves changing the common molecular structure of CFCs by attaching a disruptive hydrogen atom into the stable arrangement of chlorine and fluorine. Because these new molecules are less stable, they break up in the lower atmosphere and are less liable to reach the stratosphere where they can do harm. Some manufacturers or rigid and soft foam products are turning to pentane as a blowing agent instead of CFC. Because of pentane flammability during manufacturing, it requires added fire preventive measures. Pentane is also used in aerosol sprays. When it is mixed with a deodorant or another water-based substance, the hire hazard is eliminated.

Variety of businesses that use products manufactured with CFCs, such as foam packaging for foods, have begun to cut back on their purchases of CFC containers. One well-publicized example is McDonald’s. In August 1987, the company announced that it would phase out CFC-produced Styrofoam packaging and use another type of container manufactured without the use of ozone depleting chemicals (Ozone Supporting environmental protection policies is one form of action you can take, but like many others concerned about the fate of the planet, you may wonder about more personal, more direct approaches. Since dry-cleaning solvents release CFCs into the atmosphere, you could buy and wear clothing that is produced from washable fabrics. You can also buy furniture and food that are not made from CFC foam.

A home fire extinguisher does not have to contain halons – buy the type filled with a more environmentally safe chemical. If you could join with millions of people across the nation in conservation efforts designed to protect the environment from atmospheric pollutants, fossil fuel consumption – and the release of hazardous chemical substances would certainly decrease. Whatever each of us can do to protect our global commons, it seems crucial to begin those efforts now, to use a much quoted phrase:“ We are all in this together.” All of us need to work in our own particular ways to be caretaker of the earth.

Bibliography:

“Health effects of Overexposure to the sun.” 22 March 2000. (23 March 2000). “Ozone Science: The facts behind the phaseout.” 22 March 2000. (23 March 2000). “Grave threat to Earth’s protective ozone layer.” (2 April 2000).

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