Ammonium, as N (NH4-N)

NH4-N, Ammonium, som N



CAS no


Molecular formula


 Ammonium is a colourless, positively charged ion of ammonia. Ammonium is a weak acid.1


Ammonium compounds are often produced by direct reaction between dissolved or gaseous ammonia and an acid. Its main application is as artificial fertiliser, explosive, baking soda and fire retardant in textiles.2

Sources and transportation pathways

Ammonia is emitted to air, where it is converted into ammonium (NH4+) and is deposited to land, water and vegetation3. The chemical reaction of ammonia to ammonium may occur before or after deposition4. Wastewater treatment plants are the single largest point sources of ammonium emissions to water in Sweden.

Effects on environment and health

Deposition of nitrogen compounds results in acidification and eutrophication of land and water5. Acidification harms plants and animals, both on land and in water6. When the ground turns acidic, vital nutrients are leached from the soil, which eventually may result in reduced forest growth. Furthermore, metals are released in the ground that can harm decomposing organisms in the ground as well as birds and mammals higher up in the food chain, including humans7. Eutrophication occurs when there is an excess of nutrients (e.g. nitrogen) in land or water8. The abundance of nutrients threatens biological diversity by allowing species that thrive in a nutrient-rich environment to outcompete species that are adapted to a more nutrient-poor environment9.

Elevated concentrations of ammonium in drinking water may lead to formation of nitrite. If the concentration exceeds 50 mg/l, it should not be given to children below one year old as it will adversely affect the oxygen uptake.10

International agreements and regulations

Ammonium is regulated by the EU Groundwater Directive (2006/118/EC).