nitrates and NO3-N

[Stephan Mifsud <valerandi at yahoo_com>]

> I guess I got confused for a couple of reasons.
> 1) water chemistry professionals refer to nitrates
as
NO3-N, at
> least that's what an EPA document I found on the
web, and
my local
> water company does. We aquarists refer to nitrates
as NO3

I hope this does not sound patronising but either you
misunderstood them or else they are'nt water chemistry
professionals. NO3-N means 'nitrate-nitrogen' not
'nitrates'. It refers to the content of nitrogen (N)
in
solution due to nitrates. It leaves out the three
oxygen atoms (O3) in NO3; that is why it is a smaller
value. We also use it in testing plant tissues. This
might sound strange but chemical tests for
nitrate-nitrogen detect the nitrate ions and not the
nitrate-nitrogen specifically. The instruments or
tests may however be calibrated to read nitrate-N, or
else the value can be computed with the x 0.22
conversion factor.

But why do non-aquarists need to work with
nitrate-nitrogen? You have to remember that Nitrogen
in water exists in many forms : Nitrate, nitrite,
ammonia, proteins, amino acids, urea etc... To perform
calculations with nitrogen they need to work with just
the N and leave out the O3 of NO3, H4 of NH4,  etc.

So to determine the N content of a solution of
nitrates, nitrites and ammonium, One can not just add
the concentrations of N03,NO2 and NH4. But with
NO3-N,NO2-N and NH4-N they can.

Luckily we do not usually have to this in the hobby!

Hope this helps, but if you need more info look at
this
site: 
http://www.tomgriffin.com/aquasource/nitrobal.html

regards

Stephan
Malta


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