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This article in SSSAJ

  1. Vol. 49 No. 4, p. 891-895
     
    Received: Aug 20, 1984
    Published: July, 1985


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doi:10.2136/sssaj1985.03615995004900040020x

Transient Microsite Models of Denitrification: II. Model Results1

  1. P. K. McConnaughey and
  2. D. R. Bouldin2

Abstract

Abstract

Solutions to four models of denitrification are presented. The models are based on four coupled reaction-diffusion equations, each model describing a different type of reaction term. The equations were solved by standard finite-difference methods and a boundary tracking technique when needed. For a chosen test problem, the zero-order model predicted sequential reduction of nitrogenous species, a N2/N2O ratio of 0.17, and relatively high transient NO-2 levels. The Michaelis-Menten model with threshold and concentration-dependent NO-3 and NO-2 inhibition of N2O reduction predicted N2/N2O ratios of 19.15 and 6.69, respectively. The competitive inhibition model predicted a N2/N2O ratio of 0.23 and N2 evolution followed N2O. A sensitivity analysis of the Michaelis-Menten model with concentration-dependent inhibition showed that the species of gaseous N evolved depended strongly on NO-3 levels in the soil. N2/N2O ratios were also influenced by O2 fluxes, diffusion coefficients, and diffusion distances that affect anaerobic volume and solute transport. The predicted N2/N2O ratios were less sensitive to the Michaelis-Menten kinetic parameters Vimax and KiM where i = nitrate, nitrite, or nitrous oxide. The qualitative behavior of gaseous N evolution as a function of nitrate levels, gaseous oxygen concentration, and depth of saturation predicted by the models agrees with data in the literature.

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