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- From: parson_r@cubldr.colorado.edu (Robert Parson)
- Newsgroups: sci.environment
- Subject: Re: Another ozone question
- Message-ID: <1993Jan26.175921.1@cubldr.colorado.edu>
- Date: 27 Jan 93 00:59:21 GMT
- References: <1466602062@igc.apc.org> <1k3fo2INN29k@gap.caltech.edu> <1993Jan26.173513.1@cubldr.colorado.edu>
- Sender: news@ucsu.Colorado.EDU (USENET News System)
- Organization: University of Colorado, Boulder
- Lines: 21
- Nntp-Posting-Host: gold.colorado.edu
-
- In article <1993Jan26.173513.1@cubldr.colorado.edu>, I wrote:
-
- > 1. The whole process took hundreds or thousands of millions of years,
- > with the oxygen content of the atmosphere slowly creeping upwards.
- >
- Whoa - that's a peculiar image there, oxygen diffusing upwards on a
- billion-year time scale? I meant that the concentration of oxygen in
- the atmosphere increased very slowly.
-
- Wayne's _Chemistry of Atmospheres_ (Oxford 1991, Ch. 7) has a brief
- discussion of the evolution of the earth's (and other planets') atmospheres.
- He reproduces a figure from a model calculation of ozone concentrations
- for various oxygen concentrations. With oxygen at 10**-4 of its present
- level, ozone is mostly at the surface, but even for oxygen at 10**-3 of
- present an "ozone layer" starts to form (down around 10 km, whereas the
- present layer is between 15 and 40 km). All such calculations are
- speculative since, as Carl said, the ozone loss rate depends sensitively
- upon trace constituents and we don't know much about what their
- concentrations were a billion years ago!
-
- Robert
-
