This study evaluates the impact of nitrate injection on a full scale landfill bioreactor through the monitoring of gaseous releases and particularly N 2 O emissions. During several weeks, we monitored gas concentrations in the landfill gas collection system as well as surface gas releases with a series of seven static chambers. These devices were directly connected to a gas chromatograph coupled to a flame ionisation detector and an electron capture detector (GC-FID/ECD) placed directly on the field. Measurements were performed before, during and after recirculation of raw leachate and nitrate-enhanced leachate. Raw leachate recirculation did not have a significant effect on the biogas concentrations (CO 2 , CH 4 and N 2 O) in the gas extraction network. However, nitrate-enhanced leachate recirculation induced a marked increase of the N 2 O concentrations in the gas collected from the recirculation trench (100-fold increase from 0.2ppm to 23ppm). In the common gas collection system however, this N 2 O increase was no more detectable because of dilution by gas coming from other cells or ambient air intrusion. Surface releases through the temporary cover were characterized by a large spatial and temporal variability. One automated chamber gave limited standard errors over each experimental period for N 2 O releases: 8.1±0.16mg m −2 d −1 (n=384), 4.2±0.14mg m −2 d −1 (n=132) and 1.9±0.10mg m −2 d −1 (n=49), during, after raw leachate and nitrate-enhanced leachate recirculation, respectively. No clear correlation between N 2 O gaseous surface releases and recirculation events were evidenced. Estimated N 2 O fluxes remained in the lower range of what is reported in the literature for landfill covers, even after nitrate injection.