nitrification

https://doi.org/10.1351/goldbook.N04147
Sequential oxidation of ammonium salts to nitrite and nitrate by microorganisms.
Source:
PAC, 1993, 65, 2003. 'Glossary for chemists of terms used in toxicology (IUPAC Recommendations 1993)' on page 2075 (https://doi.org/10.1351/pac199365092003)