We have been using both the Silva et al (2000) and Chang et al (1999)
methods for some 5 years, and have analyzed many soil water samples.  For
samples with high DOC and Cl concentrations, you will want to use the large
resin amounts and the cation columns described in Chang et al (1999) to
collect the samples.  You need to know something about the water chemistry
before you load filtered water onto the columns because you can easily
overload the anion columns (the anion retention capacity is 1.2 meq/mL).
For really high DOC levels, you might want to try ultrafiltration to remove
much of the DOC before loading the columns.

--Carol
*******************************************************************************

Carol Kendall                                                        tel:
1-650-329-4576
USGS, 345 Middlefield Road, MS 434           fax: 1-650-329-5590
Menlo Park, CA 94025 USA                    email:[log in to unmask]












                    Jim
                    Karagatzides           To:     [log in to unmask]
                    <[log in to unmask]        cc:
                    ENSU.CA>               Subject:     anion resins for N-15 of
                    Sent by: Stable        NO3
                    Isotope
                    Geochemistry
                    <ISOGEOCHEM@LIS
                    T.UVM.EDU>


                    06/27/00 02:54
                    PM
                    Please respond
                    to Stable
                    Isotope
                    Geochemistry





Dear Isogeochemists,

I'd like to use the USGS anion resins for N-15 and O-18 analyses (described
in Chang et al., 1999, Can J Fish Aquat Sci and Silva et al., 2000, J
Hydrol) and am looking for advice or comments from experienced users.

I will be in a fairly remote study area on the west coast of Vancouver
Island, B.C., Canada but have occassional access to a field house to do the
lab work. While I will analyze streamwater, forest throughfall and oceanic
waters, my main goal right now is to measure N-15 in soil moisture
collected with porous-cup lysimeters under vaccuum. I have some preliminary
background levels and it appears to me that I have fairly low nitrate
concentrations (summer average of about 100 ug/L; range 10 - 200 ug/L) but
high DOC (40-90 mg/L) and "high" Cl (50 - 300 mg/L, depending on location
and depth in soil) from sea spray. I will use the 5ml columns with the
cation column to minimize DOC accumulation on the anion column. And, I
presume I will have to use multiple anion columns for each sample because
of the high Cl levels and low NO3.

Has anybody used the anion columns to measure N-15 in nitrate of soil
moisture? Even though I will be working in the wettest part of Canada in
highly saturated soils, I'm developing an uneasy feeling that I may not be
able to use the method since I have low NO3 but high Cl and DOC levels (?).

Thank you for any comments and advice.


Jim


============================

Jim Karagatzides
Department of Geography
Queen's University
Kingston  ON  K7L 3N6

Tel: 613-533-6000 x77831
Fax: 613-533-6122  or 6617