Hello,

I would like to know how much of a shift in the d13C of DIC one would
expect between poisoned and unpoisoned samples for relatively alkaline
carbonate groundwaters (3-6 meq/L Alk). I have seen a shift of 1-2 per
mil, and I'm just wondering what others have observed.

Thanks!
Dan

On Fri, 5 Mar 1999, Gilles St-Jean wrote:

> Dear All
>
> We`ve been testing waters for del13C of DIC that are preserved with sodium
> azide, a common bactericide that is used in water samples. As N2O is
> produced during acidification, and which follows the CO2, it was normally
> trapped at -130?C. However, we`ve done some tests, which show that even at
> -130, there is a minor isotope effect. This may not be a concern for large
> samples, but the problem increases with decreasing sample size. Hence, HgCl
> is still a better anti-bacterial agent to prevent reaction during storage
> of water samples for DIC. Note that NaAz was recommended in Clark and
> Fritz`s isotope textbook (Table 10-1), but we have put a note on the book`s
> website (http://www.science.uottawa.ca/~eih) with this new recommendation.
>
> Gilles and Ian
>
> Gilles St-Jean
> Technologue / Technologist
> Laboratoires d'isotopes- G.G. Hatch -Isotope Laboratories
> U d'Ottawa / U of Ottawa
> Dept des Sciences de la Terre / Dept of Earth Sciences
> 140 Louis Pasteur, Ottawa, Ontario, Canada, K1N 6N5
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