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Nedeľa, 14. augusta 2022
Ozone depletion
Dátum pridania: 21.11.2002 Oznámkuj: 12345
Autor referátu: aradvan
 
Jazyk: Angličtina Počet slov: 620
Referát vhodný pre: Stredná odborná škola Počet A4: 2.2
Priemerná známka: 2.99 Rýchle čítanie: 3m 40s
Pomalé čítanie: 5m 30s
 

It could gradually diffuse into the stratosphere, there reacting with ozone molecules.
Other chemical pollutants such as methyl chloride and carbon tetrachloride may also diffuse into the ozone layer and eliminate ozone molecules.
Natural pollutants such as nitrogen oxides from volcanoes and chloride ions from sea salt may also destroy the ozone layer, although these processes are presumably in balance with natural ozone replenishment.
Ozone depletion will increase the amount of UV light striking the earth. In reasonable amounts, UV light tans light skin and stimulates vitamin D production in the skin. However, excess UV exposure causes serious burns and may cause skin cancer. It would also be lethal to bacteria and plants.
In September, 1987, 24 nations signed a treaty, called the Montreal Protocol, which would cut CFC production in half by 1999.
Manufacturers now are pursuing several options: (1) production of less stable CFC compounds, (2) production of non-CFC substitutes, (3) conservation (using less to do the same job), and (4) recycling.
By adding a hydrogen atom to the stable CFC molecule, researchers can make less stable CFCs that break up in the lower atmosphere. The chlorine atoms released during this process, are less likely to reach the stratosphere.
One of these less stable CFCs, HCFC-22, is already on the market. It is 20 times less destructive than the CFC-12, and is used as a coolant in some home air conditioners. The main drawback is that it works at a higher pressure than CFC-12, therefore systems using this new chemical will require much heavier compressors and stronger tubes. That means more cost. There are some other substitutes...
International cooperation is badly needed to avert potential disaster.
 
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