text: Definition for NH3-N\nAmmonia Nitrogen - an inorganic, dissolved form of nitrogen that can be found in water, but in the presence of oxygen will convert to nitrate.\n\nAmmonia (NH3-N) \nan inorganic form of nitrogen, is contained in fertilizers, septic system effluent, and animal wastes. It is also a product of bacterial decomposition of organic matter. Ammonia NH3-N (NH3-N) becomes a concern if high levels of the un-ionized form are present. In this form NH3-N can be toxic to aquatic organisms. The presence of un-ionized ammonia is a function of the NH3-N concentration, pH, and temperature. Conversion of NH3-N to nitrite nitrogen by nitrification requires large quantities of oxygen which can kill aquatic organisms due to the lowered dissolved oxygen concentrations in water. NH3-N concentrations are reported in mg/L NH3-N.