chemistry question?

[brewmaster15]

Hi all,
I know that ammonia exists as the less toxic ammonium when its in water below 7.0 pH... Does anyone know what happens to Nitrite and Nitrate in acidic water...anything?...

-al

[Polar_Bear]

As far as I know nothing. NO2 remains no more or less toxic at high or low pH, as does NO3. This is the main reason I care far less about NH3/NH4 than I do about NO2. My guess is that the Hydrogen atom in Ammonia/Ammonium is the key to this, since as I'm sure you already know Al, H+ ions are what determines pH, and since NO2 or NO3 don't carry them they are uneffected by pH.

[Graham]

I agree with Larry, as far as I know nothing happens to either one.

[Ardan]

I read in an old Diskusbrief magazine that Nitrite becomes more toxic at lower ph, so if you have ammonia and nitrite it becomes a dilemna.


Ardan

[Graham]

Interesting...don't have a copy of that article that you could scan in?

One thing about nitrite it's affect are easy to overcome, regardless of pH

[Ardan]

I's in Diskusbrief Volume IV, Issue II Summer 1997 pages 8 through 12
it states on page 12 "In contrast to ammonium, nitrite toxicity increases as the pH decreases since the amount of nitrous acid will increase tenfold for every unit the ph drops. In water with low pH and ionic stregth as is the case for breeding discus, possible nitrite formation must be carefully and continuously checked."

It is the nitrous acid Hno2, "that easily diffuses through the gill membrane" at low pH " there are increasing amounts of hydrogen ion, H+ to bond to nitrie NO2- thereby forming nitrous acid, HNO2-."


I will try to scan these pages and attach them, don't know how many kb it will take?
hth

Ardan

[Ardan]

It also states the salt can reduce the effects of nitrite toxicity if the ph is above 7

Ardan

[brewmaster15]

HI Graham,
I have read multiple references to Nitrite being more toxic in lower pH, and also that the benefits of using salt to reduce toxicity of nitrites in lower pHs decrease dramatically.

Part of my purpose in this thread was that My understanding is at more acidic pH values, nitrite exists more as nitrous acid..and I think thats more toxic than nitrite... someone correct me if I am wrong here.

thanks,
al

[Ardan]

Sorry Graham, I can't post a scanned copy due to copyright issues.


Ardan

[Graham]

Nitrites/Nitrous Acid
Nitrite (NO2-) is the by-product of Nitrosomonas bacteria breaking down ammonia in alkaline water. Nitrous Acid (HNO2-) is the by-product of Nitrosomonas bacteria breaking down ammonium in acid water. These reactions are the first steps in the Nitrogen Cycle. There is again an exponential relationship with pH. As pH decreases below pH 7, the amount of nitrous acid increases and becomes more toxic. A test for these molecules should read 0.0 PPM. To reduce toxic nitrous acid, make water changes, reduce the fish load, reduce the feeding amounts or adjust the pH. Add salt at the rate of 0.2% to inhibit the intake by the fish of nitrous acid.

Learn something new everyday..............this is from the Assoc Koi Clubs of America web site

http://www.akca.org/library/akcamed7.htm

It's always been my understanding that it's the Nitrogen that is toxic to the fish and not the overall compound , such as NO2 and HNO2-.........just like the chloride ion that's used to protect the fish, not the sodium or the calcium, so salt works in even lower pH's

[Graham]

Looks like I might be wrong about the salt protecting the fish at low pH's. According to this PP slide HNO2- is readily taken up by the fish where as NO2 is pumped across via the chloride pumps,

Looking at the graph below, at pH of 5.0 or lower toxicity increases very quickly

http://biology.uwsp.edu/faculty/CHartleb/Biol498/PowerPoint/Water.ppt#293,22,Nitrite Water Chemistry

G

[brewmaster15]

Hi Graham,
I've said it a million times...I'm a biologist, not a chemist.. :) so forgive me anyone if I mess this up.

The reason that salt is effective I think has to do with the gill surface.. in pH that is not acidic...you flood the water with sodium chloride ions... this are taken up across the gill membrane because its a function of the gill membrane to exhange Ions like sodium chloride...when you are flooding the water with sodium chloride you are excluding the ability of nitrite to be taken up ....

Thats my understanding of it.. its basically a principal we used in the labs called competitive inhibition.

Now take the same situation in acidic water..the more acidic the water the greater the percent of nitrite exists as nitrous acid. Nitrous acid does not need to actively transported across the gills as nitrite does.. It diffuses freely.... and is more toxic.. I also believe that once it gets into a fish with its physiological pH being alkaline..some probably reverts again to nitrite.

I have no idea on how well or accurately I just explained that...if someone finds an error in it...please speak up.

hth,
al

[brewmaster15]

Looks like we were posting at the same time..:)

-al

[Graham]

Hey you're one ahead of me...I don't have either degree:(

I don't see why most of the HNO2- wouldn't drop that hydrogen ion and then tox out the fish since fish blood has a pH of about 7.4..........not really different than ammonia/ammonium.

Good topic...

G

[Green Country Discus]

Great input and thread Al and Graham!! I wish I had the knowledge to contribute. Thanks for sharing and please do carry on ;) !

[brewmaster15]

LOl Andrew,
I think we are all in the dark as to how exactly this stuff works..I just think its fun to try and shed a few rays of light here and there.:)


SOOO... Heres an unrelated...mostly unrelated question..:)

How does a fish like a discus maintain an internal physiological pH that is neutral to alkaline while living in extremely acidic and soft water? Thats one that has always puzzled me. Talk about an extremely efficient internal buffering system!

-al

[Graham]

Al now you're getting into the basic physiology of a Discus and other low pH, soft water fish. Thier ability to maintain salt levels at about 0.9%, and retain other essential minerals etc while in extremely ''dead'' water is amazing.

By all rights salinity, every salt and mineral in thier blood should be diffusing out via the gills especially when hobbyists are using pure RO water

They are a very fine tuned fish .............

I've linked this thread to KoiShack...everyone can learn from it

http://koishack.com/forums/index.php?showtopic=7157

G