Fact Sheet - Ammonia

Ammonia (NH₃)
Ammonia is a source of nitrogen (N), an important nutrient for plants and algae. Ammonia is excreted by animals and is produced during the decomposition of plants and animals. Ammonia is an ingredient in many fertilizers and is also present in sewage, storm water runoff, certain industrial wastewaters, and runoff from animal feedlots.

Ammonia in Water
At the temperature and pH range typical of most rivers and lakes, ammonia exists predominantly in the ionized form (NH₄⁺). As pH and temperature increase, the ionized ammonia changes to un-ionized ammonia gas (NH₃). Ammonia gas can be toxic to fish and other aquatic organisms. If dissolved oxygen (DO) is present, ammonia can easily be broken down by nitrifying bacteria to form nitrite and nitrate.

Ammonia in the Red River
The water quality standards for ammonia in both Minnesota and North Dakota are intended to protect aquatic life against the impacts of gaseous ammonia (un-ionized ammonia). The proportion of ammonia gas to the total ammonia concentration increases with temperature and pH. The pH of the Red River is slightly alkaline year-round but the temperature of the water varies from just above freezing (0°C) to over 25°C (over 77°F). The changes in water temperature mean that only a small portion of the total ammonia in the water occurs as a gas in the winter but a greater proportion of ammonia occurs as a gas in the summer. The Minnesota Pollution Control Agency (MPCA) standard, based on chronic (long-term) exposure to un-ionized ammonia, is set at 0.016 mg/L of nitrogen from un-ionized ammonia. The North Dakota Department of Health (NDDH) has two ammonia-related standards for the Red River: 1) a chronic standard and 2) a site-specific chronic standard for a 32-mile stretch of the Red River in the Fargo-Moorhead (FM) area extending from Fargo's 12th Avenue North bridge downstream to the mouth of the Buffalo River. Both NDDH chronic standards are calculated using mathematical equations that account for both temperature and pH.

Trends
The graph shows the monthly average concentration of total ammonia in the Red River. If the concentration of total ammonia enters the red zones on the graph, fish and other aquatic organisms can be harmed by ammonia gas. As you can see, the concentration of total ammonia in the river is generally too low to pose a danger to river organisms, even in the warmer water of the summer months when more ammonia occurs as a gas.

Graph of total ammonia levels (mg/L) for the Red River in the FM metro area during the period January 2000 to January 2003. The red areas on the graph indicate the levels of total ammonia in the river water (based on actual conditions of pH and water temperature) needed to produce levels of ammonia gas dangerous to aquatic life. The graph shows that only when the water temperature is high in the summer does the proportion of ammonia in the river water that occurs as a gas approach the danger level for aquatic life.