I use Phreeqc to simulate fish breathing to see what happen when I dissolve CO2 into seawater and freshwater, with and without NH3. (NH3 is a gas from nitrogen break down in the metabolism). If I, in seawater only use CO2 (for instance 0.3 mmol/l) the reaction is normal with expected fall in pH. But if I also adding NH3 (0.03 mmol/l) the pH falls further? If I simulate the same procedure in fresh water the opposite happen, which I think is normal.
For me it looks that NH3 have functions as acids in seawater (it convert HCO3 to H2CO3) but is a base in freshwater (it convert CO2 to HCO3)?
CO2 + H2O « H2CO3 « (HCO3-) + (H+) « (CO3--) + (H+)
NH3 + H2O « (NH4+) + (OH-)
In freshwater (simplified) CO2 + OH- « HCO3 (pH increase)
In seawater (simplified) HCO3 + OH- « H2CO3 (pH decrease)????
I hope you understand my not so god English.
Please note that some U.S. Geological Survey (USGS) information accessed through this page may be preliminary in nature and presented prior to final review and approval by the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the sole responsibility of the user.
Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government.
The URL of this page is:
Last modified: $Date: 2005-09-13 21:04:21 -0600 (Tue, 13 Sep 2005) $
Visitor number 8203 since Jan 22, 1998.