| There is a large research gap in understanding abiotic NO3 - and NO2- transformations by Fe(II) species. This is important to understand in light of the important role of this chemical pathway in the inhibition of soil Fe(III) reduction by NO3 - and NO2-. This project investigated the kinetics and stoichiometry of the reaction of Fe(II) minerals (siderite (FeCO 3) and wustite (FeO)) with NO3- and NO 2-; and the reactivity of adsorbed Fe(II) species (adsorbed Fe(II) on kaolinite) with NO2- over a range of experimental conditions in the laboratory (initial reactant concentrations, pH, and temperature) using stirred-batch experiments and ion chromatography, gas chromatography, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Nitrate reduction by FeO produced NH4+ and Fe3O4 as reaction products and a rate equation was derived that included a fractional order dependence on FeO and H+, and a first order dependence on NO3-. The temperature study indicated that the reaction was surface chemical controlled and proceeded by an associative mechanism. Siderite reduced NO2- to N2O and itself oxidized to goethite (alpha-FeOOH) and lepidocrocite (gamma-FeOOH). Sidente did not react with NO3-. The kinetics of NO 2- reduction were described by a rate equation with a first order dependence on FeCO3(s) and NO2- and fractional order dependence on H+. The rate data can be used to predict NO2- removal under conditions where FeCO3(S) is present. Kaolinite reduced NO2- to N2O in the presence and absence of adsorbed Fe(II). Chemical extractions and XRD indicated iron impurities provided a source of reduction capacity in the kaolinite.; Keywords. Nitrate, nitrite, reduction, kinetics, siderite. |
