Dear Chris
There is a method for DIC analysis that does not need preservation of the
sample, is simple and reliable.  The reference is given below.  I am sure
others can address the issue of S-34 and sample preservation.


Atekwana E. A. and Krishnamurthy, R. V., 1998. Seasonal variations of
dissolved inorganic carbon and ?13C of surface waters: Application of a
modified gas evolution technique. Journal of Hydrology 205, 265-278.


Good luck

Eliot Atekwana                  Assistant Professor
Department of Geology           (317) 274 7969 (office)
IUPUI                           (317) 274 7484 (dept.)
723 W Michigan Street           (317) 274 7966 (fax)
Indianapolis IN 46202-5132      e-mail:  [log in to unmask]
www.geology.iupui.edu


-----Original Message-----
From:   Christopher Romanek [SMTP:[log in to unmask]]
Sent:   Thursday, October 07, 1999 7:25 AM
To:     [log in to unmask]
Subject:        DIC analysis

Dear subscribers,

I have a student who is collecting water samples for dissovled inorganic
carbon (C-13) and sulfide (S-34) analysis (both at 100's of ppm).  I
usually add a few granules of solid HgCl to vials to inhibit microbial
activity for  samples lacking sulfide,  but I'm worried about sequestering
Hg as HgS, potentially compromising both C-13 and S-34 analyses.

Can anyone please offer advice or a protocol for such samples (different
way to "poison" samples)?  I apologize in advance if this issue has been
broached recently.

Chris Romanek
Savannah RIver Ecology Lab