Physics and Chemistry of Water
Published Online: 15 APR 2005
Copyright © 2005 by John Wiley & Sons, Inc.
How to Cite
Steele, K. F. and Brye, K. R. 2005. Nitrogen. Water Encyclopedia. 4:517–520.
- Published Online: 15 APR 2005
Nitrogen (N) is ubiquitous in the environment and in the correct form is an essential nutrient for plants and animals. About 26.5% of Earth's nitrogen is in rocks and essentially all of the remainder (73%) is in the atmosphere as an inert monotomic gas (N2) that comprises 78% of the atmosphere. Only a small amount of nitrogen is present in the hydrosphere and biosphere, but nitrogen is a crucial nutrient there. For nitrogen to be used by organisms, it must be in a usable form; it must be combined or “fixed” with oxygen or hydrogen. The most common fixed form of nitrogen in ground water is the anionic oxide—nitrate (NO3−), and the second most common form is the cationic form–ammonium (NH4+). Approximately 85% of the nitrogen in stream water is in the form of organic N and most of the rest (NO3− and NH4+) is derived from the decomposition of organic matter. N2 is converted to organic nitrogen predominantly by microorganisms and certain plants. About 96% of the nitrogen in soil is bound in organic matter, and nitrate is a product of organic matter degradation. Nitrogen occurs in five oxidation states, −3, 0, +1, +3 and +5, that are primarily the result of bacteria-induced oxidation.
- nitrogen cycle;
- toxicity of aquatic nitrogen species;
- nitrogen isotopes;