Nitrate [NO3-]and
nitrite [NO2-] are naturally occurring
ions that are part of the nitrogen cycle. Nitrate is used mainly in inorganic
fertilizers, and sodium nitrite is used as a food preservative, especially in
cured meats. The nitrate concentration in groundwater and surface water is
normally low but can reach high levels as a result of agricultural [activity
and] runoff, refuse dump runoff, or contamination with human or animal wastes.
Chloramination may give rise to the formation of nitrite within the
distribution system, and the concentration of nitrite may increase as the water
moves towards the extremities of the system.
