Denitrification

Denitrification is the microbial process of reducing nitrate and nitrite to gaseous forms of nitrogen, principally nitrous oxide (N2O) and nitrogen (N2). A large range of microorganims can denitrify. Denitrification is a response to changes in the oxygen (O2) concentration of their immediate environment. Only when O2 is limited will denitrifiers switch from aerobic respiration to anaerobic respiration, using nitrite (NO2) as electron acceptor. Denitrification is a process ubiquitous to all our terrestrial and aquatic ecosystems and occurs in tropical and temperate soils, in natural and intensively managed ecosystems, in marine and freshwater environments, in wastewater treatment plants, manure stores, and aquifers. It is a beneficial process in removing nitrate (NO3) from wastewater, but has a negative effect in removing valuable nitrogen fertilizer from the soil and releasing the greenhouse gas N2O and the tropospheric pollutant NO. This article summarizes current knowledge on the groups of microorganisms involved in denitrification, the environmental conditions required for denitrification to take place, and how we measure and model denitrification rates.