Ammonia is a nutritious, inorganic nitrogen compound that is found naturally in the air, soil, water and living tissues (think pee). At room temperature, it is a gas.
Its chemical formula is NH3 in the gaseous phase and when dissolved in water, much of it ionizes to NH4+ (now called ammonium ion). Total ammonia is the sum of both NH3 and NH4+. Total ammonia is what is measured analytically in water.
Why it is important: Ammonia is the preferred nitrogen-containing nutrient for plant growth. Ammonia can be converted to nitrite (NO2) and nitrate (NO3) by bacteria, and then used by plants. Nitrate and ammonia are the most common forms of nitrogen in aquatic systems. Nitrate predominates in unpolluted waters. Ammonia is excreted by animals and produced during decomposition of plants and animals, thus returning nitrogen to the aquatic system.
Ammonia is also a common pollutant because it is relatively abundant but can be toxic, causing lower reproduction and growth, or death. The neutral, un-ionized form of ammonia in water (NH3) is highly toxic to fish and other aquatic life.
The ratio of NH3/NH4+ in waters is directly related to the temperature and pH of the water.
Sources in the Environment:
Ammonia is present in surface water and is formed from the decomposition of most nitrogenous organic material.
It is also used in the pharmaceutical industry, in industrial processes, as a fuel, as a fertilizer, and in cleaners. In the Midwest, it is such a common agricultural fertilizer that it is transported by pipeline from Louisiana to Wisconsin and Indiana.
Ammonia is also a byproduct of wastewater treatment that must be mitigated before effluent water can be released into the environment.
Groundwater and landfill leachates are commonly tested for ammonia.
Maine Maximum Exposure Guideline limit: 30,000 ppb in drinking water
EPA Health Advisory Limit: 30,000 ppb
EPA Maximum Contaminant Level: none set
USA Primary Drinking Water Standard limit: n/a
USA Secondary Drinking Water Standard limit: n/a
Toxic Substances Portal: “Ammonia”
California Water Board: “Ammonia,” (pdf)