Who-Ray,

Finally some cents in this discussion of proper usage.  Sure we should all
be perfect all the time (NOT) but life is short and if I have a Mac (was
that just a shallow IBM-er shot) and I don't hav ethe time to type 5
characters when 1 gets my point across-- well I sorry.  And sure depletion
is an ambiguous word, but long ago we decided that the rare isotope goes on
top and the common one on the bottom (look at some acient lit. from the
50's and it is the other way around), the term should be claer enough. 
Personally I would say depleration in the rare isotope, but to worry about
del is to worry about "ioti".   Pass me another, organics-filled beverage,
please.
Regards,

Bob Ilchik
Department of Geosciences
University of Arizona
Tucson, AZ  85721
(520) 621-9792 (W)
(520) 881-2002 (H)