ABSTRACT
Nitrogen (N) (MW ¼ 14.0067) is an integral part of the hydrosphere (2.3 1013 tn), atmosphere (3.5 1015 tn), and lithosphere (5 1016 tn).[1,2] Nitrogen serves as an essential component of cells and participates in almost every biological phenomenon in the biosphere.[2] Nitrogen cycles in the biosphere along with carbon, water, oxygen, sulfur, phosphorus, and other elements. Nitrogen in the form of nitrate (NO3
-N), nitrite (NO2 -N), ammonium (NH3-N), and
organic N are of great importance in waters and wastewaters.[3] Approximately 95% of the hydrosphere’s N is stored as molecular N with the remaining 5% distributed in a 60:40 ratio between inorganic nitrates and organic N. Although N is very abundanta significant disturbance on a local level, such as wastewater or fertilizer introduction, can result in abnormal N redistributions on regional, continental, and even global levels.[2] Thus, it is very important to recognize and quantify N sources and cycle pathways. This entry discusses typical concentrations of N in waters and wastewaters, and methods suitable for measuring N concentrations in water and wastewater.
