The State of Canada's Environment — 1996

Glossary of Selected Terms - N

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Sources for definitions

natural regeneration: See regeneration.

nitrogen fixation: Conversion of gaseous (atmospheric) nitrogen (N₂) to compounds such as ammonia (NH₃). Carried out in ecosystems mainly by bacteria of the genus Rhizobium (Arms 1990). See also ammonia nitrogen.

nitrogen oxides (nox): A group of gases released by fossil fuel combustion, forest fires, lightning, and decaying vegetation (adapted from Greater Vancouver Regional District 1994). Nitrogen dioxide (NO2), a reddish-brown gas with an irritating odour, is one of the key ingredients in smog. Nitrous oxide (N2O) is a greenhouse gas whose principal source is agricultural soil in a degraded state (Environment Canada 1995).

nonnative: See alien.

non-point source: Source of pollution in which pollutants are discharged over a widespread area or from a number of small inputs rather than from distinct, identifiable sources (Environment Canada et al. 1988). Examples include eroding croplands, urban and suburban lands, and logged forestlands. See also point source.

nonrenewable resource: Natural resource that cannot be replaced, regenerated, or brought back to its original state once it has been extracted (International Organization for Standardization 1995). Examples of nonrenewable resources include coal, crude oil, and metal ores.

nutrient: Any element or compound that an organism must take in from its environment because it cannot produce it or cannot produce it as fast as it needs it (Arms 1990). As pollutants, any substance or group of substances (e.g., phosphorus or nitrogen) that, if added to water in sufficient quantities, provides nourishment that promotes the growth of aquatic vegetation in those waters to such densities as to degrade or alter or form part of a process of degradation or alteration of the quality of those waters to an extent that is detrimental to their use by any plant or animal, including humans (modified from Environment Canada et al. 1988). An example would be eutrophication of a lake.

nutrient enrichment: See eutrophication.