NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/sci/environm/14844

Internet Message Format | 1993-01-26 | 3.0 KB

Path: sparky!uunet!elroy.jpl.nasa.gov!nntp-server.caltech.edu!SOL1.GPS.CALTECH.EDU!CARL
From: [e-mail] (Carl J Lydick)
Newsgroups: sci.environment
Subject: Re: Another ozone question
Date: 26 Jan 1993 13:53:06 GMT
Organization: HST Wide Field/Planetary Camera
Lines: 52
Distribution: world
Message-ID: <[e-mail]>
References: <[e-mail]>
Reply-To: [e-mail]
NNTP-Posting-Host: sol1.gps.caltech.edu

In article <[e-mail]>, [e-mail] (Wanda Ballentine) writes:
=
=I have a question I hope someone out there can answer.
=
=The facts as I understand them:  The beginning of life on Earth
=slowly evolved deep in the oceans, eventually creating oxygen
=that bubbled to the surface and then floated up to the
=stratosphere.  About 30 miles from the surface, ultraviolet
=radiation acted upon it to create ozone, and ultimately there was
=enough created to form a buffer between the UV rays and the
=Earth.
=
=Question:  As the UV rays were already bombarding the Earth, WHY
=did the reaction with the oxygen not create ozone at the ground
=level??

It almost certainly did, and continues to do so.  However, one has to look at
two reaction rates:
    O2 => O3 conversion
and    O3 => O2 conversion

The former is driven by UV radiation.  The more oxygen you have between the sun
and the place you're looking at, the more UV will have been absorbed in the
reaction before the sunlight reaches you.  Hence, the rate of formation of O3
would tend to be higher at higher altitudes.

The latter is, among other things, a surface-catalyzed reaction, and therefore
the greater the concentration of particulate matter, aerosols, and so forth,
the faster the reaction goes.  The concentration of these things is higher near
the ground.  Hence this reaction tends to go faster near the ground.

Combining these two facts:
    1)  The rate of ozone formation would tend to be slower at ground
        level; and
    2)  The rate of ozone destruction would tend to be greater at ground
        level;
we reach the conclusion:
    The concentration of ozone would tend to be lower at ground level.

Now, of course, there are other considerations.  In particular, one path for
formation of ozone involves the photochemical reaction of hydrocarbons and
nitrogen oxides, so you find substantial ozone formation wherever you find a
mixture of hydrocarbons and nitrogen oxides.  The Los Angeles basin is a good
example of such a situation
--------------------------------------------------------------------------------
Carl J Lydick | INTERnet: [e-mail] | NSI/HEPnet: SOL1::CARL

Disclaimer:  Hey, I understand VAXen and VMS.  That's what I get paid for.  My
understanding of astronomy is purely at the amateur level (or below).  So
unless what I'm saying is directly related to VAX/VMS, don't hold me or my
organization responsible for it.  If it IS related to VAX/VMS, you can try to
hold me responsible for it, but my organization had nothing to do with it.