Hi! Theresa,

If you are worried about losing a fraction of OM that is soluble in HCL,
acid fumigation of soil could be an option.  The following is the
reference:

David Harris, et al. 2001, Acid fumigation of soils to remove carbonates
prior to total organic carbon or carbon-13 isotopic analysis, Soil
Science Society of America Journal, v.65, 1853-1856.

Hope this helps.

Kyungsoo Yoo
graduate student
Pedology and Isotope Biogeochemistry Lab.
Ecosystem Sciences Div.
U. C. Berkeley
510-643-6910

-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On
Behalf Of Carrie Masiello
Sent: Thursday, August 22, 2002 2:18 PM
To: [log in to unmask]
Subject: Re: inorganic carbon elimination from soil samples

Hi Theresa --

        I have another opinion on this -- I think you need to be careful
rinsing off acid because you lose a fraction of the OM when you do this.
Effectively you end up measuring the carbon content of the
acid-insoluble
fraction of the sample, NOT the total organic carbon content.  I'm not
sure of the effect of this on the sample's 13C signature, but I DO know
that by removing overlying HCl you can dramatically alter a sample's 14C
signature, easily by as much as 100 per mil.  There are 2 options to
avoid
this:

1) pump off the HCl.  This can be done in a vacuum centrifuge overnight,
and leaves you with all your original OM.  If you do this you have to be
prepared to deal with HCl coming through your vacuum system.

2) prep the samples with H2SO3 (not H2SO4).  H2SO3 breaks down at about
50C to H2O and SO2 and will evolve from the samples.  There's a paper on
this method by Dave Verardo in Deep Sea Research part A v 37, 157-165,
1990.

good luck,

Carrie Masiello
AAUW Postdoctoral Fellow 2002-2003

On Wed, 21 Aug 2002, Giovanni Calderone wrote:

> Dear all, I am interested in C and N stable isotope composition of SOM
> using an elemental analyzer coupled with a MS, so by 1N HCl I can
> remove carbonates from the soil samples, but how can I rinse it from
> the sample?
>
> Thank you
>
>
> Teresa Bertolini
>
> CNR-ISAFOM, Italy
>
>