Issue 8

What’s Nitrogen Got to Do With It?

There are many different forms of the element nitrogen. Three common forms are ammonia (NH₃), nitrate (NO₃), and nitrite (NO₂). Ammonia is a result of the natural breakdown of animal and vegetable matter by bacteria. Ammonia will react with water to form ammonium ions. Nitrate is formed from the complete oxidation of ammonium by certain microorganisms, with nitrite as an intermediate product. In well oxygenated waters, nitrite is readily oxidized to nitrate in a process called nitrification.

Major sources of nitrogen (besides the decay of animal and vegetable matter) include fertilizers, industrial and agricultural waste, sewage, and the atmosphere. Ammonia, nitrate, and nitrite are all toxic to aquatic life under certain conditions. Nitrate encourages the growth of algae and other organisms which can produce undesirable tastes and odors in water. In high enough levels, ammonia can cause a direct toxicity to fish and aquatic life. Oxygen in water is consumed in the conversion of ammonia to nitrites and nitrates, leading to a condition called anoxia.

In the process of biotransformation, chemicals are changed from one form to another by microorganisms. Denitrification is part of this larger process; nitrate is transformed into nitrogen gas by microorganisms in anaerobic conditions, resulting in the loss of nitrogen as it is converted to (gaseous) molecular nitrogen (N₂) and nitrous oxide (N₂O). This is a significant part of the cleaning process that takes place in wetlands.

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