Effects of Temperature on No3− and No2− Reduction, Nitrogenous Gas Production, and Redox Potential in a Saturated Soil

Samples of the Ap horizon of a Huron soil were used to investigate the effects of temperature on NO3− and NO2− reduction, nitrogenous gas production, and redox potential under anaerobic conditions in the laboratory. NO3− and NO2− reduction occurred at redox potential (Eh) values of 200 and 180 mV, respectively. The rate of NO3− and NO2− reduction decreased with decreasing temperatures (30–5 C). At 5 C, NO3− reduction was completely inhibited but NO2− reduction continued at a slow rate. Gas chromatographic analyses showed that the denitrification gas was composed of N2, N2O, and NO. Decreasing the temperature decreased the production of N2, increased the production of NO, and did not significantly affect the production of N2O. The increased production of NO at low temperatures when NO2− was the nitrogen source is attributed to chemodenitrification processes.