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Re: pH crashes maybe not
The effect of pH on nitrite toxicity is indirect:
Nitrite oxidizes hemoglobin to methemoglobin, which does not carry
oxygen, hence its toxicity.
The oxidation of nitrite to nitrate is pH dependent, the optimum being
pH 7.1. Thus at low pH the nitrite is not converted to nitrate as fast
Nitrite can be quite toxic (LD50 for salmon is 0.5 ppm and for rainbow
trout 0.2 ppm.) so as it accumulates to the lethal level, the fish,
This, in my understanding, is the correlation of nitrite toxicity with
Wright Huntley wrote:
> Scott Lewis wrote:
> > Wright Huntley wrote:
> >>Likewise, ammonia can kill at higher pH (more gets converted from
> >>ammonium) and nitrite gets deadly at pH below about 6.5. It is the toxic
> >>materials damaging the fish, and it just happens that pH correlates with
> >>the chemical effects that render them lethal.
> > Wright, could you point me to a reference that describes the increased toxicity of
> > nitrites at low pH levels?
> My recent move left all my reference books scattered or stored, so not
> really. Sorry Scotty.
> You might start with Spotte, but I'm not too sure it is there.
> I understand the equilibrium change in the ammonium/ammonia ratio as pH
> increases. If you find a good description of the nitrite chemistry, how
> about sharing it here, with us. I have never been sure why nitrite (NOT
> nitrate, BTW) is worse at lower pH. Nitrates appear to be harmless in
> concentrations below about 200-300 ppm, regardless of pH.
> Wright Huntley -- 209 521-0557 -- 731 Loletta Ave, Modesto CA 95351
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