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[APD] Re:Ammonia and Soil Substrates

Scott said:
>The diff in ammonia vs ammonium is slightly changed as the
>pH changes.

"The percentage of ammonia in a solution with a given N concentration
changes dramatically with pH.  Typically, there is a 10 fold increase in
ammonia for every 1 unit increase in pH as NH4+ converts to NH3 in the above
equilibrium reaction.  For example, if the pH increases from 7.0 to 8.0 the
% of N that is NH3 increases from about 0.33% to 3.3%, while the % of N that
is NH4+ correspondingly falls from 99.7% to 96.7%[53].  Thus the higher the
pH the greater the NH3 concentration and the toxicity of a given
concentration of inorganic nitrogen." - D. Walstad, "The Ecology of the
Planted Aquarium", 1st edition.

So I agree that "slightly" would describe the change in ammonium, but I
would prefer to use the word "dramatically", as Walstad does, to describe
the increase in ammonia. I feel a factor of 10 increase in ammonia is
significant and can mean the difference between life and death for a fish.

Steve Pituch

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