Relationship between total ammonia and free ammonia in terrestrial and ocean waters

Abstract

The toxic effects of ammonia to fish are generally considered to be caused by the unionized fraction (NH3), rather than by the ionic components (NH4+ and NH4SO4−), which co-exist in equilibria in ammonia-in-water systems. The equilibrium is highly dependent on pH, temperature, pressure and ionic concentrations. The physico-chemical parameters of the system have been evaluated by Whitfield (1974) for most conditions encountered in terrestrial and ocean waters, including fish rearing situations. This note describes a computer program which has been written for easy, routine but precise calculation of the unionized ammonia fractions.