From: billc@devnull.mpd.tandem.com (Bill Carter)
Newsgroups: austin.general
Subject: CFC's and the ozone layer
Date: 12 Jan 93 20:46:41 GMT
Reply-To: billc@devnull.mpd.tandem.com (Bill Carter)
Distribution: tx
Organization: Tandem Computers; Austin TX
Originator: billc@zippy


   I tried posting this earlier this morning, but I don't think
   it got out.  Sorry if it appears twice...


jfh@rpp386.cactus.org (John F. Haugh II) writes;
>It is my understanding that the mobility of different substances within
>the atmosphere is dependent, in large part, on the density of that
>substance.  For example, helium was not discovered on earth, it was
>discovered on the sun, because all of the atmosphere helium "escapes"
>through the upper atmosphere.  Likewise, you will probably find virtually
>all of the radon on the planet very close to the ground.

   I found your analysis of the behavior of gases in the atmosphere
   interesting and it made some sense.  But if I follow your line
   of reasoning, we should have an atmosphere which is highly
   stratified with heavy gases near the ground and light ones near
   space.  It seems to me that the atmosphere is roiled by convection,
   and over time I would expect the gases to get mixed together pretty
   thoroughly.

   You wouldn't have to know much chemistry and physics to know
   more than I do, but I have done some reading on the ozone problem.
   What's more, I saw a show on PBS last night called "The Ozone Hole"
   and now I Am Informed (oboy, fresh ammo).  I don't know how
   accurate the show was, but I figure it's at least as reliable as
   what I see on the net :)

   Here's what I heard.  CFC's are very stable, non-reactive molecules
   and they hang around in the atmosphere for decades.  How they reach
   the upper atmosphere wasn't explained, but apparently they do make
   it up there eventually.  It may take 30-40 years for a particular
   CFC molecule to get to the stratosphere, and that's part of the problem.
   CFC's that were released back in the 60's are just now getting to the
   ozone layer, and we have plenty more in the lower atmosphere which will
   get there as well.

   CFC's don't destroy ozone directly, they require mediation to free
   up the chlorine.  The chlorine acts as a catalyst, and one chlorine
   atom can break up hundreds of thousands of O3 molecules.

>What we DO know is that the polar vortices isolate the polar regions from
>the rest of the atmosphere and that the temperatures in the stratosphere
>over the poles become extremely cold.  We also know that this does not
>favor the production of ozone.  You don't have to create some theory by
>which CFCs drift over the to polar regions to explain a decrease in ozone.
>You can explain it with the fundemental nature of the reactions which
>produce and destroy ozone.  The stratosphere - and the stratosphere in the
>polar regions in particular - is not well suited for ozone production.  It
>never was, it never will be, not using CFC's will not change this
>fundemental fact of nature.

   Polar vortices only occur in the winter.  In the warmer months
   the air over the poles freely blends together with adjacent areas.
   During the winter ice crystals form in the stratosphere, a phenomenon
   unique to the polar vortices.  Chlorine is freed from CFC's on the
   surface of the ice crystals, the show didn't say exactly how.
   The chlorine destroys ozone which migrated to the poles during the
   warm months.  When the vortex disappears, the ozone-free air blends
   in with adjacent air masses and dilutes the ozone there.  The rate
   of ozone production, at least in the high latitudes, appears to be
   slower than the rate of destruction.

>Hydrogen sulfide is agreed by everyone to be destructive to ozone.  It
>is also more plentiful (by orders of magnitude) than CFC's.  It is also
>natural.  It is also lighter and able to get into the upper atmosphere.
>Why is it only in the last few years that CFCs are being blamed for
>ozone depletion?  What about proton emissions from the sun during solar
>storms?  What about volcanic erruptions?

   No mention was made of hydrogen sulfide.  The culprit from volcanic
   eruptions was identified as SO2, which is said to mediate the release
   of chlorine from CFC's similar to the behavior of the ice crystals.
   Ozone (O3)is formed when sunlight hits O2, I don't know exactly how.
   What is the effect of solar proton emissions?

   A researcher on the show who had studied the arctic gases stated that
   there is now no doubt that CFC's are at the root of the depletion.
   The evidence must be fairly convincing, because the U.S. is halting
   all CFC production in 1995.

=========================================
Bill Carter             I draw water.
                        I carry wood.
                        This is my magic.