Sciencemadness Discussion Board

The Ozone layer.

White Yeti - 25-7-2011 at 11:49

I have a feeling that this question has an obvious answer, but I will ask it anyway.

We all seem to be concerned about the destruction of the ozone layer that protects us from UV rays. But the following set of reactions seems to show that as long there is oxygen, high energy ultraviolet rays will be absorbed.
O2+ hv--> 2O
O2+ O--> O3
O3+ O--> 2O2

So where is the problem? As long as there is oxygen, the must also be a detectable amount of ozone. Furthermore, the ozone doesn't actually absorb ultraviolet radiation, the dissociation of the oxygen atoms in O2 absorbs the UV rays. One last thing, the photolysis of oxygen creates AND destroys ozone, as shown my the last reaction. So do CFC's really destroy the ozone layer? Or do we even need an ozone layer? Since it is oxygen that absorbs high energy ultraviolet rays.

Polverone - 25-7-2011 at 12:38

Atmospheric oxygen effectively absorbs UV radiation with a wavelength shorter than about 240 nm, and this is the initial source of ozone as you've shown in your reactions. It lets through longer-wavelength (but still biologically hazardous) UV radiation. The ozone layer absorbs most UV radiation between 240 and 320 nm. If the equilibrium concentration of ozone in the ozone layer decreases -- such as happened when CFC breakdown starting producing halogen radicals in the layer -- the irradiation of Earth's surface by ultraviolet between 240 and 320 nm increases.

Sedit - 25-7-2011 at 13:30

I find it interesting that the "photos" of the hole I seen when I was younger was in an area where there is little industrial process and that it was a little off from the north pole. Logic at even a young age just suggest to me that the hole has been there due to the low angle of sun rays reaching it and its just our satellite technology catching up with it.

Mr. Wizard - 25-7-2011 at 21:42

Quote: Originally posted by Sedit  
I find it interesting that the "photos" of the hole I seen when I was younger was in an area where there is little industrial process and that it was a little off from the north pole. Logic at even a young age just suggest to me that the hole has been there due to the low angle of sun rays reaching it and its just our satellite technology catching up with it.


I suspected the same thing.

White Yeti - 26-7-2011 at 05:18

"The ozone layer absorbs most UV radiation between 240 and 320 nm."
Ok, thanks, that was more or less the answer I was looking for.