Water quality and pollution by nutrients

Nitrate in the groundwater: Agriculture is the largest contributor of nitrogen pollution to groundwater.

Nitrogen from excess fertiliser percolates through the soil and is detectable as elevated nitrate concentrations under aerobic conditions and as elevated ammonium concentrations under anaerobic conditions. The rate of percolation is often slow and excess nitrogen concentrations may be the effects of pollution on the surface from up to 40 years prior, depending on the hydro-geological conditions.

Drinking water contaminated with nitrate poses a health risk to infants. Nitrate concentrations higher than the 50 mg/l limit set by the Drinking Water Directive are mainly recorded in private and small communal supplies from shallow aquifers, and in areas with intensive agricultural and livestock production. Further information on the content of nitrate in groundwater can be found in the EEA core set indicator on nutrients in freshwater