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Reports & Essays: Science - Earth

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Ozone
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.

 



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