|
|
Clouds and the ozone hole
What's the connection with the ozone hole?
Under normal circumstances, the ozone layer is stable because the rate of ozone destruction roughly equals the rate of ozone production. However, some molecules are particularly dangerous to ozone - for example nitric oxide (NO), bromine, and chlorine. Consider reactions between chlorine radicals (Cl) and ozone:
Cl + O3 -> ClO + O2
ClO + O -> Cl + O2 A chlorine radical collides with an ozone molecule to form chlorine monoxide and molecular oxygen. The chlorine monoxide can then quickly react with molecular oxygen to reform chlorine. These two reactions have destroyed one ozone molecule, but the chlorine radical is still intact and can go on to destroy many more ozone molecules. A single chlorine atom can remove as many as 100,000 ozone molecules in its life. A major source of chlorine is CFC's (chlorofluorocarbons), which were commonly used in spray cans and refrigerators until the late 1970's. They are non-reactive in the lower atmosphere and so were thought to be safe, but because they don't react they can gradually make their way into the stratosphere. The average lifetime of a CFC molecule is about 50 to 100 years.
Next page
->
What's the connection with the ozone hole? continued
Links and resources
What's the connection with the ozone hole?
Under normal circumstances, the ozone layer is stable because the rate of ozone destruction roughly equals the rate of ozone production. However, some molecules are particularly dangerous to ozone - for example nitric oxide (NO), bromine, and chlorine. Consider reactions between chlorine radicals (Cl) and ozone:
Cl + O3 -> ClO + O2
ClO + O -> Cl + O2 A chlorine radical collides with an ozone molecule to form chlorine monoxide and molecular oxygen. The chlorine monoxide can then quickly react with molecular oxygen to reform chlorine. These two reactions have destroyed one ozone molecule, but the chlorine radical is still intact and can go on to destroy many more ozone molecules. A single chlorine atom can remove as many as 100,000 ozone molecules in its life. A major source of chlorine is CFC's (chlorofluorocarbons), which were commonly used in spray cans and refrigerators until the late 1970's. They are non-reactive in the lower atmosphere and so were thought to be safe, but because they don't react they can gradually make their way into the stratosphere. The average lifetime of a CFC molecule is about 50 to 100 years.
