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Transient Microsite Models of Denitrification: III. Comparison of Experimental and Model Results
Author(s) -
McConnaughey P. K.,
Bouldin D. R.,
Duxbury J. M.
Publication year - 1985
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/sssaj1985.03615995004900040021x
Subject(s) - nitrous oxide , denitrification , chemistry , nitrous oxide reductase , flux (metallurgy) , carbon dioxide , analytical chemistry (journal) , nitrate , nitrogen , environmental chemistry , denitrifying bacteria , organic chemistry
Experiments were designed to investigate the validity of proposed reaction‐diffusion models of denitrification. Brass respirometers were used to measure fluxes of oxygen (O 2 ), carbon dioxide (CO 2 ), and nitrous oxide (N 2 O) from a 5 × 10 −3 ‐m layer of saturated soil incubated at 25°C. Gaseous fluxes were measured as a function of time after wetting, with and without 0.42 mol m −3 of acetylene (C 2 H 2 ) present in the headspace. The presence of C 2 H 2 in the headspace doubled O 2 fluxes 35 to 60 h after incubations commenced. When C 2 H 2 was not present, N 2 O evolution was negligible after 25 h of incubation. Nitrous oxide fluxes predicted by the models were compared to those observed experimentally. When C 2 H 2 was present, the models predicted N 2 O fluxes reasonably well ( r 2 = 0.90 and 0.78) for initial nitrate (NO − 3 ) N levels of 7.1 and 15.9 mg N kg −1 soil, respectively. When C 2 H 2 was not present, the models predicted the experimentally observed initial flux of N 2 O if an 8 to 10 h lag in N 2 O reductase activity was included in the models. The best model for describing N 2 O fluxes in these experiments used differential rates of Michaelis‐Menten reduction without NO − 3 and nitrite (NO − 2 ) inhibition of N 2 O reduction. Experimental techniques and parameter characterization, however, need considerable refinement. Independent measurements are needed to quantify relationships between reaction order and kinetic parameters. Still, given the general agreement between observed and predicted fluxes, there can be little doubt that the reaction‐diffusion models are essential to a better understanding of denitrification.