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Francis,
I am also interested in natural abundance 15N of soil ammonium and
nitrate.
There is definitely no straightforward method as for bulk soil.
I have used the diffusion technique (see Stark & Hart, Soil Sci. Soc.
Am. J. 60:1846-1855) for KCl extracts. I'd recommend it for ammonium.
Nitrate is more difficult, because potential contamination from
residual ammonium and there is contamination from reagents. If your
soil N concentrations are high, the latter should not be as big a
problem. If you have adequate funding, you could use the denitrifyer
method for nitrate. There are a few service labs available.
You'd have to transport frozen soil extracts or fresh soil back to
your lab- I don't know if this is logistically possible for you.
Good luck,
Kirsten
Kirsten Stephan
PhD Candidate
Department of Forest Resources
University of Idaho
P.O. Box 441133
Moscow, ID 83844-1133
----- Original Message -----
From: Francis Brearley <[log in to unmask]>
Date: Saturday, May 20, 2006 8:21 am
Subject: [ISOGEOCHEM] 15N of ammonium and nitrate
To: [log in to unmask]
> Dear All,
>
> I will be working in Jamaica this summer to look at 15N in plant-
> soil
> systems. I will be measuring 15N of bulk soil which will be
> straightforward but I am also hoping to measure 15N of ammonium
> and
> nitrate (which are the forms of nitrogen that will be immediately
> available to plants and are therefore of more interest). Does
> anyone know
> of a method which can be used to measure 15N of these two
> compounds.
>
> The main drawback I have is that I'll be in Jamaica while our IRMS
> is in
> Dublin. This means that I need to be able to process and/or store
> the
> samples for a few weeks before being able to analyse them. Also,
> I won't
> really have access to a lab so the easier and simpler the method
> the
> better.
>
> Many thanks
>
> Francis
>
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