Dinitrogen from nitrification

Nitrification-denitrification reactions are the major pathway for N loss from wetland ecosystems to the atmosphere. The process involves a series of sequential microbial processes that include mineralization of organic nitrogen to ammonium, oxidation of ammonium to nitrate, and denitrification of nitrate to nitrous oxide or dinitrogen gas. Nitrification-denitrification in wetlands occurs primarily in two zones the aerobic-anaerobic interface at the surface of the flooded soil or sediment, and the oxidized rhizosphere of wetland plants (Figure 16.6). 

Figure 12 Major reduction-oxidation reactions involving nitrogen. The reactions are numbered as follows (1) mineralization, (2) ammonium assimilation, (3) nitrification, (4) assimilatory or dissimilatory nitrate reduction, (5) ammonium oxidation, (6) nitrite oxidation, (7) assimilatory or dissimilatory nitrate reduction, (8) assimilatory or dissimilatory nitrite reduction, (9) denitrification, (10) chemodenitrification, (11) anaerobic ammonium oxidation, and (12) dinitrogen fixation (after Capone, 1991) (reproduced by permission of ASM Press from Microbial Production and Consumption of Greenhouse Gases Methane, Nitrogen Oxides, and Halomethanes, 1991).

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