How do fluorocarbons destroy the ozone composing the ozone layer?

(Lansing State Journal, Jan. 29, 1997)

Question submitted by Todd Chupko.

The ozone layer is a region of ozone in the upper atmosphere that protects the earth from the harmful rays of the sun. If the ozone layer were transported to the surface of the earth, it would be about 3 millimeters thick.

The natural balance of ozone productions and destruction involving high-energy solar rays is disrupted by nitrogen dioxide and chlorine in the atmosphere. The main sources of chlorine are man made chlorofluorocarbons. A single chlorine from one CFC can destroy around 10,000 ozone molecules in it's lifetime.

When CFCs are released into the atmosphere, they migrate from the lower atmosphere (troposphere), to the upper atmosphere (stratosphere) after about three to five years.

In the stratosphere, the CFCs go through a series of reactions, which include the destruction of ozone.

These reactions begin with the solar rays reacting with the CFCs to produce a reactive chlorine atom. The chlorine reacts with ozone to form chlorine monoxide. Chlorine monoxide then either reacts with nitrogen dioxide to produce chlorine nitrate, or two chlorine monoxides will react to reform reactive chlorine.

Chlorine nitrate does not react with ozone until it reaches Antarctica. There, during the winter the ozone hole forms. The hole is caused by the release of reactive forms of chlorine from chlorine nitrate. The reactions take place on the ice particles and with the small number of solar rays in the region.

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