Seasonal variation of N 2 O emissions in France inferred from atmospheric N 2 O and 222 Rn measurements

Nitrous oxide (N 2 O) concentrations and 222 Rn activities are measured semi‐continuously at three stations in France: Gif‐sur‐Yvette (a semi‐urban station near Paris), Trainou tower (a rural station) and Puy‐de‐Dôme (a mountain site). From 2002 to 2011, we have found a mean rate of N 2 O increase of 0.7 pbb a −1 . The analysis of the mean diurnal N 2 O and 222 Rn cycles shows maximum variabilities at the semi‐urban site of Gif‐sur‐Yvette (0.96 ppb for N 2 O and 2 Bq m −3 for 222 Rn) compared to the rural site of Trainou tower (0.32 ppb for N 2 O and 1.3 Bq m −3 for 222 Rn). The use of 222 Rn as a tracer for vertical mixing and atmospheric transport, combined with the semi‐continuous N 2 O measurements, allows estimation of N 2 O emissions by applying the Radon‐Tracer‐Method. Mean N 2 O emissions values between 0.34 ± 0.12 and 0.51 ± 0.18 g(N 2 O) m −2 a −1 and 0.52 ± 0.18 g(N 2 O) m −2 a −1 were estimated in the catchment area of Gif‐sur‐Yvette and Trainou, respectively. The mean annual N 2 O fluxes at Gif‐sur‐Yvette station correlate well with annual precipitation. A 25% increase in precipitation corresponds to a 32% increase in N 2 O flux. The N 2 O fluxes calculated with the Radon‐Tracer‐Method show a seasonal cycle, which indicates a strong contribution from the agricultural source, with the application of fertilizers in the early spring inducing a strong increase in N 2 O emissions. Finally, the results of the Radon‐Tracer‐Method agree well with the national and global emission inventories, accounting for the uncertainties of both methods. Mean seasonal cycle of N2O shows the importance of the agricultural source Annual nitrous oxide emissions are correlated with annual precipitation Comparison between atmospheric approach and inventories agree well