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Typically, denitrification occurs in anoxic environments, where the concentration of dissolved and freely available oxygen is depleted. In these areas, nitrate (NO 3 −) or nitrite (NO 2 −) can be used as a substitute terminal electron acceptor instead of oxygen (O 2), a more energetically favourable electron acceptor. Terminal electron ...
Water samples for nitrate/nitrite analyses need to be kept at 4 °C in a refrigerated room and analysed as quick as possible to limit the loss of nitrate. In the first step of the denitrification process, dissolved nitrate (NO − 3) is catalytically reduced into nitrite (NO − 2) by the enzymatic activity of bacteria.
Nitrate, acting as an oxidant, is therefore reduced in a succession of four reactions performed by the enzymes nitrate, nitrite, nitric-oxide, and nitrous oxide reductases. [2] The pathway ultimately yields reduced molecular nitrogen (N 2 ), as well as, when the reaction does not reach completion, the intermediate species nitrous oxide ( N 2 O ).
The most common denitrification process is outlined below, with the nitrogen oxides being converted back to gaseous nitrogen: 2 NO 3 − + 10 e − + 12 H + → N 2 + 6 H 2 O. The result is one molecule of nitrogen and six molecules of water. Denitrifying bacteria are a part of the N cycle, and consists of sending the N back into the atmosphere.
Nitrogen assimilation is the formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment. Organisms like plants, fungi and certain bacteria that can fix nitrogen gas (N 2) depend on the ability to assimilate nitrate or ammonia for their needs.
Elevated nitrate in groundwater is a concern for drinking water use because nitrate can interfere with blood-oxygen levels in infants and cause methemoglobinemia or blue-baby syndrome. [28] Where groundwater recharges stream flow, nitrate-enriched groundwater can contribute to eutrophication , a process that leads to high algal population and ...
Nitrogen cycle. Nitrification is the biological oxidation of ammonia to nitrate via the intermediary nitrite.Nitrification is an important step in the nitrogen cycle in soil.The process of complete nitrification may occur through separate organisms [1] or entirely within one organism, as in comammox bacteria.
As dissimilatory nitrate reduction to ammonium is an anaerobic respiration process, marine microorganisms capable of performing DNRA are most commonly found in environments low in O 2, such as oxygen minimum zones (OMZs) in the water column, or sediments with steep O 2 gradients. [11] [12] The oceanic nitrogen cycle with the role of DNRA.