This study evaluates the impact of nitrate injection on a full scale landfill bioreactor, with a particular emphasis on the monitoring of gaseous emissions and particularly N2O emissions. During several weeks, we monitored gas composition in the landfill gas collection system as well as surface emissions with a series of seven static chamber boxes. Measurements were realized before, during and after recirculation of raw leachate and leachate enriched with nitrate. No significant variation of the surface gas emissions, directly related to the recirculations was observed. A recirculation of raw leachate does not have a significant effect on the biogas concentrations (CO2, CH4 and N2O) in the collection systems. On the other hand, a recirculation of leachate enriched with nitrate increases by 100 fold the N2O concentrations in the gas collection system located in the recirculation trench. In the common gas collection system however, this increase of N2O was no more detectable because of a dilution by gas coming from other cells. No significant increase of N2O gaseous surface emissions was recorded in the week following nitrate injection.