We are attempting to use Biosphere 2's ocean for some 13C studies (CO3=
dependence of fractionation).  In order to hold the CO3= at the desired
values, we must add NaHCO3 each week (~60 pounds).  The HCO3- we buy has
a d13C of -19 per mil and the ocean a d13C of -5 per mil.  Hence, each
addition causes a shift in the ocean  d13C.  Do you know of a commercial
HCO3 salt with a value closer to  zero?  If we could find such a source
we could add the two in the right  proportions and thereby avoid the 13C
shift.  Of course, we could make our  own from limestone but considering
the large quantities needed, this would be a lot of work.

Cheers, Wally    Wallace S. Broecker

--
Chris Langdon, Assoc. Res. Sci.
Lamont-Doherty Earth Observatory
Palisades, NY 10964
Tel: 914/365-8641  Fax: 914/365-8150
Email:  [log in to unmask]
Web page: www.ldeo.columbia/~langdon