A highly soluble form of nitrogen that is both a nutrient and, in excess quantities, a toxic substance.
Ammoniacal nitrogen is converted to nitrate nitrogen in soils, from where it can then leach into waterways. Nitrate is a plant fertiliser, however, due to its high solubility in water, it is one of the most common contaminants in rural and urban areas.
View factsheets on Nitrogen and Nitrate nitrogen in Groundwater.