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Oxidation of Ammonium to Nitrate in a Soil Column
Author(s) -
Ardakani M. S.,
Rehbock J. T.,
McLaren A. D.
Publication year - 1974
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1974.03615995003800010030x
Subject(s) - nitrite , ammonium , nitrate , chemistry , oxidizing agent , steady state (chemistry) , inorganic chemistry , nitrification , anammox , nitrogen , denitrification , organic chemistry , denitrifying bacteria
A mathematical model based on Michaelis‐Menten kinetics for oxidation of ammonium to nitrate during downward flow in a column of soil mixed with sand has been tested. First the column was perfused with nitrite to stimulate the growth of nitrite oxidizing microorganisms in order to decrease the concentration of nitrite at any time in the column during subsequent perfusion with ammonium. The nitrite oxidizers multiplied in a quasilogistic fashion to nearly maximal numbers, exceeding ammonium oxidizers by at least a factor of 10 2 . After a population density of 10 3 /cm 3 was reached for NO 2 ‐ oxidizers, the column was perfused with ammonium solution; in a steady state the ammonium concentration decreased with depth (proportional to time of flow) in accord with Michaelis‐Menten kinetics. The rate constants for oxidation of NH 4 + were proportional to the numbers of ammonium oxidizing microorganisms extant at any given time of observation; these numbers increased exponentially at first but leveled off after about 3 weeks of continuous perfusion of the column. As expected, the decline of ammonium concentration with depth during solution flow just equalled the appearance of nitrate with very low concentrations of nitrite in the steady state. From the data the normalized rate constant is 4.5 × 10 ‐3 ppm cm 3 /hour per microbe at room temperature, about five times greater than the corresponding figure for nitrite oxidation.