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Ozone Depletion
Dátum pridania: 27.12.2001 Oznámkuj: 12345
Autor referátu: kris_d
Jazyk: Angličtina Počet slov: 686
Referát vhodný pre: Stredná odborná škola Počet A4: 2.3
Priemerná známka: 3.00 Rýchle čítanie: 3m 50s
Pomalé čítanie: 5m 45s
Ozone depletion

One of the biggest ecological problems of today is the ozone depletion. Many chemical compounds, in the past considered not being dangerous, have been released into the air and have come to the lower atmospheric layers – their collecting causes ozone to deplete. Let us firstly see what the ozone is, what is its function and where can we find it. The ozone molecule contains three oxygen atoms and is very similar to the “normal” oxygen we breathe, which has two such atoms. It is mostly concentrated in the lower atmospheric regions (in the stratosphere) - 15 up to 30 kilometers above the Earth’s surface. Though being much less common then normal oxygen (in 10 million air molecules about 2 million are normal oxygen, but only 3 are ozone), ozone plays a key role in the atmosphere. The ozone layer absorbs a portion of the very dangerous ultraviolet (UVB) light radiation from the sun. These rays have very harmful effects for both plants and animals, including cancers, cataracts, harms to forms of marine life etc. The ozone layer’s destruction is catalyzed by many different chemical substances released in the air. Chlorofluorocarbons (CFCs), along with other chlorine- and bromine-containing compounds, are accelerating the depletion rapidly. The CFC, broken down by the strong UV radiation, releases one atomic chlorine that destroys 100,000 ozone molecules. The effect is that the ozone is destroyed faster then it could be naturally created. These processes were known potentially dangerous, but the depletion was not measured and evidenced until 1984.
Chlorofluorocarbons had great exploitation in the past. Better known as freons, maybe from the “fre(eze)on”, they were developed in the third decade of the last century. For around fifty years, they were thought of as miracle: they are stable to both chemical reactions and thermodynamic factors, almost non-toxic, cheap and nonflammable. These properties made them ideal for a great variety of uses: as coolants for commercial and home refrigeration units, aerosols, electronic cleaning solvents and blowing agents. Along with halons, used for example in fire extinguishers, their production and use grew rapidly as demand for products requiring their use continued to rise.
CFCs and all the other bad-for-ozone chemical compounds are very hard do get rid of.
Just for a compare: there are 20 million tons (!) of CFCs released in the air, but only 15% of them have reached the ozone layer yet.
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