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It is entirely the UV light energy that does it. It is actually very complex, but you can consider that there is a resonance in the oxygen molecule that absorbs the UV energy at a given frequency and this energy is sufficient to break down the covalent bond between the two oxygen atoms to liberate them from each other. The "loose" atoms of oxgen the beetle around until they find an oxygen molecule, with which it combines to form an ozone molecule. This happens at typically 12 to 50 km altitude, but the main effect is at 20-40 km, Below 20, there is already sufficient UV filtering that the energy levels tail off: above 40, there is less oxygen for chance combinations of O and O2 to occur.
As ozone is an unstable gas, it is constantly forming (in daytime) and decomposing, and a natural equilibrium occurs. Ozone depletion occurs because of chain reactions whereby odd chlorine and bromine atoms attack huge numbers of ozone molecules and thus upset the natural equilibrium.
The reason for the depletion to be less at the N. Pole is simple: it's a lot warmer there (sea under the ice, instead of land). The Polar Vortex is therefore much less active and the chemical conditions in the upper and middle stratosphere are different.
One of the best brief laymen's explanations is called Action on Ozone (26 pages) at http://www.unep.ch/ozone/pdf/ozone-action-en.pdf
An excellent book outlining the problem, very easy to read and even fascinating is 'Between Earth and Sky' by Cagin and Dray, published by Pantheon ISBN 0-679-42052-5. It actually gives the history of CFCs. For example, did you know that both tetraethyl lead in motor fuel and CFCs for refrigeration were developed by the same guy, a Thomas Midgeley, who was not even a chemist, but a mechanical engineer? He suffered badly from lead poisoning, as did many of the early workers handling TEL.
Midgeley would have had a lot to answer for today, if he were still alive
It is entirely the UV light energy that does it. It is actually very complex, but you can consider that there is a resonance in the oxygen molecule that absorbs the UV energy at a given frequency and this energy is sufficient to break down the covalent bond between the two oxygen atoms to liberate them from each other. The "loose" atoms of oxgen the beetle around until they find an oxygen molecule, with which it combines to form an ozone molecule. This happens at typically 12 to 50 km altitude, but the main effect is at 20-40 km, Below 20, there is already sufficient UV filtering that the energy levels tail off: above 40, there is less oxygen for chance combinations of O and O2 to occur.
As ozone is an unstable gas, it is constantly forming (in daytime) and decomposing, and a natural equilibrium occurs. Ozone depletion occurs because of chain reactions whereby odd chlorine and bromine atoms attack huge numbers of ozone molecules and thus upset the natural equilibrium.
The reason for the depletion to be less at the N. Pole is simple: it's a lot warmer there (sea under the ice, instead of land). The Polar Vortex is therefore much less active and the chemical conditions in the upper and middle stratosphere are different.
One of the best brief laymen's explanations is called Action on Ozone (26 pages) at http://www.unep.ch/ozone/pdf/ozone-action-en.pdf
An excellent book outlining the problem, very easy to read and even fascinating is 'Between Earth and Sky' by Cagin and Dray, published by Pantheon ISBN 0-679-42052-5. It actually gives the history of CFCs. For example, did you know that both tetraethyl lead in motor fuel and CFCs for refrigeration were developed by the same guy, a Thomas Midgeley, who was not even a chemist, but a mechanical engineer? He suffered badly from lead poisoning, as did many of the early workers handling TEL.
Midgeley would have had a lot to answer for today, if he were still alive
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