MadSci Network: Environment & Ecology |
Ozone in the upper atmosphere exists in equilibrium with ordinary molecular oxygen and oxygen atoms. You can wite the equation as O3 = O2 + O That, is, all three of these forms are present in the "ozone layer." Ozone (O3) absorbs the far ultraviolet rays of sunlight, and when this absorption takes place, the ozone splits into an oxygen molecule and an oxygen atom. By absorbing the UV, the ozone layer protects people from the harmful effects of the UV -- it appears to cause basal cell skin cancers. Normally the oxygen molecules and atoms recombine to form ozone, thereby maintaining the equilibrium. However, some jet engine exhaust gases like NO, and the photochemical products of Freon aerosols, will combine readily with the oxygen atoms so that the oxygen atoms can't recombine with molecules to form ozone. These substances act as oxygen scavengers. If the atomic oxugen is not available to recombine, the ozone layer becomes depleted and cannot protect as effectively against UV in sunlight.
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