| Abstract: | The kinetics of several steps in the microbial denitrification process in Brookston clay and Fox sandy loam, two soils common to Southwestern Ontario, were studied in the temperature range of 5 to 25°C. The extent of chemical denitrification was also determined in otherwise identical but sterilized soils at temperatures up to 80°C. A gas flow system was used in which soil gases were continuously removed from anaerobic soil columns by argon carrier gas. Net steady-state rates of NO and N2O production, rates of loss of NO3−, and production and loss of NO2− were measured over periods of up to 5 days. Arrhenius activation energies for the zero-order process NO3− → NO2− were calculated to be 50 ± 9 kJ mol−1 for Brookston clay and 55 ± 13 kJ mol−1 for Fox sandy loam. The overall reaction, NO2− → NO (chemodenitrification), in both sterile soils was accurately first order with respect to NO2−; the activation energy was 70 ± 2.8 kJ mol−1 in Brookston clay and 79 ± 1.2 kJ mol−1 in the sandy loam, and the preexponential factors were (2.3 ± 1.2) × 109 and (5.7 ± 1.2) × 109 min−1, respectively. |
