Quote:
Originally Posted by John D Harris
You wrote that the pace that UV destroyes O3 is fast, and that the rate O2 bonds with O is also fast, what's the ratio or relative speeds? ie: UV takes 2 minutes to destroy, O2 & O take 3 minutes to create.
What about the rate at which CFC's destroy Ozone?
The O2 that CI creates in the upper atmosphere, that would be broken down by UV into 2 O atoms letting them Bind to O2 that haven't been broken down yet Right?
Or does the O2 drop into the lower atmosphere before it gets broken down into 2 O atoms?
What are those rates?
Would more (higher levels) UV speed up breaking O2 down into 2 O Atoms?
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GAK! I'm going to defer on the question of rates.
Go back to the first four equations I gave you:
1) O2 + UV radiation => 2 O
2) O2 + O + M = O3 + M (the original equation didn't show that this requires a non-reactive element to abbsorb energy - typically N2 or O2))
3) O3 + UV radiation (between 240 and 300 nm) => O2 + O
4) O + O3 => 2 O2
and the reaction rates are (numbers in brackets represent concentrations):
Rate1 = JO2 [O2], where JO2 is the photolysis rate constant of the reaction
Rate2 = k2 [O] [O2] [M]
Rate3 = JO3 [O3]
Rate4 = k4 [O] [O3]
Like I said, the rates of 2 and 3 are generally faster than 1 and 4. And by several orders of magnitude. I had ONE link that showed some relative numbers but I can NOT find it now.
To complicate matters, the JO3 and JO2 numbers aren't constants. They depend in part on the absorption spectrum cross section which we know varies with altitude. The net result is that there can be several order of magnitude variations in the reaction rates throughout the atmosphere. And the rate coefficient K4 isn't constant either. It varies based on temperature as
k4(O,O3) = 8.0 x 10-12 e-2060/T cm3molecule-1sec-1
And k4 is also influenced by CFCs.
I did find a parameter called PRT which is defined as the time it would take to generate the observed ozone concentration at a specific location at the existing production rate with no loss processes.
Here's a couple of pages which describe those, the reactions and far more.
http://www.ccpo.odu.edu/~lizsmith/SE...Chap_8/8_3.htm
http://www.ccpo.odu.edu/~lizsmith/SE...Chap_8/8_4.htm
And at this point I will freely admit to having reached the limit of my understanding vis a vis Ozone. LOL