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Thu, 16 Jul 1998 14:34:27 +1000 |
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Dear listmembers,
I would be grateful for any help you could give me with the following problem:
I am using delta15N values, obtained from a "bioindicator" macrophyte to try
and solve some questions regarding the main sources of N pollution (ie
sewage outfalls vs agricultural run off vs stormwater drains etc) in the
Hawkesbury-Nepean River near Sydney, Australia.
My problem is that my plants, like many macrophytes, appear to
prefererentially take up ammonia over nitrate, switching to nitrate as their
primary N source only after ammonium is depleted in the water column. As
the sites where the plants are deployed vary quite widely in the proportion
of ammonium to nitrate, I suspect the plants will also vary in the amount of
N that they gain from each type of N compound. I need to know if this will
affect the delta15N signal that I get from the plants, regardless of other
factors.
Does anyone know if the form that the N is in (ie ammonia as opposed to
nitrate) affects its' delta15N signal? For example, would ammonia and
nitrate, both from a sewage treatment plant, have the same delta15N? If
not, how much would you expect them to vary? A literature search has so far
proved fruitless......
Any references, expert knowledge or educated guesses would be much appreciated!
Many thanks in advance
Jo
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Jo Rush Phone: (61 2) 9351 3006
PhD student (61 2) 9351 5118
Biological Sciences A08 Fax: (61 2) 9351 4119
University of Sydney 2006 Mobile: 0416 28 2309
Australia [log in to unmask]
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