Inhibition by nitrite ion in the process of methane anaerobic oxidation by microorganisms and fractionation dynamics of stable carbon and hydrogen isotopes

Abstract

In the process of methane oxidation by nitrite ion, the latter, when in high concentration, inhibits the oxidation process. The effect of inhibition is incorporated in the proposed model, describing the dynamics of anaerobic oxidation of methane and its heavy fractions δ¹³CH₄ and δC²H¹H₃ by nitrite ion. Two substrates—methane and nitrite—are considered in a modified Monod function, describing the oxidation rate. The model is calibrated against experimental data given in [8]. The dynamic behavior of the system under a deficiency of methane or nitrite ion is described. The dynamics of δ¹³CH₄ and δC²H¹H₃ are shown to be governed by the oxidation dynamics of total methane CH₄. By contrast to the conventional opinion that Rayleigh equation corresponds to 1st-order kinetics in terms of substrate concentration, this study shows that Rayleigh equation can be derived from dynamic equations for methane with heavy isotopes (¹³C and ²H), whatever the kinetic type of total methane oxidation.