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Water Quality Assessment: Chemical: Nitrates, Nitrites, and Ammonia
Nitrogen is an essential nutrient that is required by all plants and animals for the formation of amino acids. In its molecular form, nitrogen cannot be used by most aquatic plants, therefore it must be converted to another form. One such form is ammonia (NH3). Ammonia may be taken up by plants or oxidized by bacteria into nitrate (NO3-) or nitrite (NO2). Of these two forms, nitrate is usually the most important. However, it is very difficult to directly measure nitrate. A common procedure for measuring nitrate is to first measure the amount of nitrite in a sample. Then, reduce any nitrate in the sample to nitrite. Lastly, measure the combined nitrite (the initial nitrite plus the reduced nitrate) concentration. By subtracting the original nitrite concentration from the combined nitrite concentration, one can determine the amount of nitrate that was in the sample.

Image of a baby.Although nitrogen is an essential nutrient for all aquatic plants and animals, it is possible to have too much of a good thing. Excessive concentrations of nitrogen can lead to eutrophication and subsequent degradation of stream water quality. In addition, if water containing nitrate levels greater than 10 mg NO3-N/L is used to prepare infant formula, it can result in methemoglobinemia. Methemoglobinemia is a condition in which red blood cells are prevented from transporting oxygen throughout the body. If the condition persists, the infant can suffocate. Photo © 1999 -www.arttoday.com

Common sources of excessive nitrogen include sewage and agricultural runoff. Elevated stream water nitrogen levels may indicate the presence of one or both of these forms of pollution.

 

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