Ammonia+Information

Ammonia-Nitrogen. Ammonia (NH3) is extremely soluble in water. When dissolved, it reacts to form ammonium (NH4+) and hydroxide (OH-) ions, as shown by the following reversible equation.

Since NH4+ is relatively less toxic to aquatic organisms than NH3, toxicity is primarily attributed to the un-ionized form. Of all freshwater organisms, fishes are generally considered the most sensitive to ammonia toxicity. By decreasing the ability of hemoglobin to combine with oxygen, NH3 may cause fish to suffocate. Brief exposure of fishes to high concentrations of NH3 may lead to loss of equilibrium, hyperexcitability, increased breathing and cardiac output, and, in extreme cases, convulsions, coma, and death. Prolonged exposure to lower concentrations reduces hatching success, growth rate, and morphological development and may cause pathological changes in the tissues of gills, livers, and kidneys (CA State Water Resources Control Board 1963).

The toxicity of ammonia is affected by several factors including pH, temperature, dissolved oxygen concentration, salinity, carbon dioxide concentration, previous acclimation to NH3, fluctuating or intermittent exposures, and other toxins. Some factors minimize or exacerbate the effects of NH3 itself, while others alter the concentration of NH3 by shifting the equilibrium. Of all factors affecting toxicity, temperature and pH are considered the most important. Increases in either variable are associated with increased concentrations of NH3 relative to NH4+. As NH3 becomes more abundant, the risk to aquatic organisms increases.

Test results for ammonia are often expressed as ammonia-nitrogen (NH3-N), or "nitrogen that was in the form of ammonia." In unpolluted, well-oxygenated freshwaters NH3-N levels are usually less than 1.0 mg/l. In CT, the maximum acceptable concentration of NH3-N, assuming a pH of 7.0 and a temperature of 250C, is 1.24 mg/l. In especially sensitive areas, like salmon spawning grounds, the maximum limit is lower (0.86 mg/l). As either temperature or pH change, the amount of ammonia needed to produce the same toxic effects also changes. If temperature or pH decrease, more NH3 is needed and the maximum acceptable concentration increases. Conversely, if temperature or pH rise, less NH3 is needed and the maximum limit decreases. The criteria for NH3-N concentrations at various temperatures, given a constant pH, are presented in Appendix D of Water Quality Standards (CT DEP 1992). For a description of the chemical reactions occurring in tests for NH3-N, see the section entitled "Chemical Reactions."

The ammonia test, like the ph test was done with an indicator. The darker the green, the more ammonia was present. 1mg/l = 1ppm