The Ozone Layer Essay Research Paper The — страница 2

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tampered with by humans. UV rays are normally used up in the natural process of producing and destroying ozone. When an unnatural substance destroys ozone and is not used up by the cycle (acts as a catalyst). This means more ozone is broken down than being created and ultra-violet rays are no longer all absorbed and therefore travel through to our atmosphere more easily. Some substances which can react in such a way with ozone are:  CFCs  methyln  chloroform  carbon tetrachloride  halons CFCs are broken down by ultra-violet rays. This process releases chlorine. The chlorine attaches itself to an ozone molecule and then this newly formed molecule breaks up into an oxygen molecule and a chlorine monoxide molecule. The chlorine monoxide molecules in turn attaches

itself to an oxygen atom. This new molecule breaks down forming an oxygen molecule and a chlorine atom and so the process starts again. The first step requires the breakdown of CFCs by UV light into a reactive chlorine atom: CFCl2 + UVCFCl + Cl (equation 4) The next step involves attack on ozone by the chlorine atom Cl + O3ClO + O2 (equation 5) Chlorine regenerated in equation 6 may feed back into equation 5. (The oxygen atom is from equations 1 or 2.) ClO + OCl + O2 (equation 6) This chlorine atom, which can recycle thousands of times, allows one CFC molecule to break down thousands of ozone molecules. The chlorine atom exists longer at Antarctic stratospheric temperatures, yielding more ozone destruction. The most important reactions in the destruction of ozone are: CCl +

ClONO2 -> HNO3 + Cl2 (1) ClONO2 + H3O -> HNO3 + HOCl (2) HCl + HOCl -> H3O + Cl2 (3) N2O5 + HCl -> HNO3 + ClONO (4) N2O5 + H3O -> 2 HNO3 (5) From the reactions above, note that only molecular chlorine (Cl2) is produced, however, to destroy ozone it is required atomic chlorine. The molecular chlorine is split by sunlight which lead to the sudden destruction of ozone. The following diagram shows a schematic illustrating the life cycle of the CFCs; how they are transported up into the upper stratosphere/lower mesosphere, how sunlight breaks down the compounds so they can destroy ozone. The Ozone Layer Data One of the main issues that worry people is the fact that the ozone layer is growing smaller at a steady rate, therefore increasing the size of holes and increasing

our chance of health problems. It can be said that humans are responsible for most of the destruction of the ozone layer. It is now becoming a great concern, and solutions are being provided. However, humans are still using products that contain CFC s and other pollutants. In the following graphs, it is obvious who is responsible for this damage and how it is already affecting some of the planet s living things. Even though, saving the ozone layer is an issue that is concerning everyone, changing the way of life for some companies is a very expensive task, even if it is for a great and necessary cause. Company CFC Quantities Cost Cost/lb. FFord Motor Company 975 tons $9 million $.21 IBM 6,500 tons $10 million $.01 The Ozone Layer Evaluation of Data From the data obtained, it can

be said that chlorine is a natural threat to ozone, whereas CFC’s are a man-made problem. CFC’s contain one fluorine atom, one carbon atom, and three chlorine atoms. When UV radiation hits a CFC molecule it causes one chlorine atom to break away. The chlorine atom then hits an ozone molecule consisting of three oxygen atoms and takes one of the oxygen molecules, destroying the ozone molecule and turning it into oxygen. When an oxygen molecule hits the molecule of chlorine monoxide, the two oxygen atoms join and form an oxygen molecule. When this happens, the chlorine atom is free and can continue to destroy ozone. Naturally occurring chlorine has the same effect in the ozone layer, but has a shorter life span. The ozone hole is growing every day. In 1996, it was about 8.3

million square miles on average in size. We account for between 75% and 85% of the ozone depletion that takes place each year. Compared to the 15% to 20% by natural sources, and the 1% to 5% from volcanoes each year, we are the guilty party. Without our involvement, the ozone would be much more stable than it is now A unique case in the Antarctic in December of 1994 showed us what is to come from our ozone hole. Penguins nesting in Bacharcaise Island had to travel as far as 200 miles offshore and some had to hunt for up to nine days straight for food. Almost all of the penguins returned without food. That summer, only about ten of the 1,800 penguin chicks that hatched on the island survived. The others died of starvation. It is believed that the reduced phytoplankton levels at