摘要：Using the eddy covariance technique, nitrous oxide (N2O) fluxes were measured at the semi-urban SMEAR III station in Helsinki, Finland, between 21 June and 27 November 2012. The measurement period covered a seasonal change from summer to autumn allowing us to examine variations in the N2O fluxes by season. Also, varying land cover around the measurement site enabled us to study the effects of different urban land covers on the N2O exchange. Overall, the measurement surroundings acted as a source of N2O with a median and quartile deviation for the campaign of 1.7 ± 2.0 μmol m–2 h–1. The net emissions were slightly higher from the direction of green areas than from the direction of roads under heavy traffic indicating that vegetation cannot be neglected in the urban N2O exchange studies. No seasonal change in the N2O flux during the measurement campaign was found.
