A field study of nitrogen removal and N2O and CH4 fluxes from integrated buffer zones

We present a detailed field study on the dynamics between processes retaining nitrogen (denitrification, plant uptake) and processes producing greenhouse gasses (incomplete denitrification, methanogenesis) in integrated buffer zones (IBZ). Integrated buffer zones are novel systems designed to be integrated within the riparian zone to retain nitrogen and other pollutants that otherwise bypass the riparian buffer zone via drainpipes. However, the anaerobic conditions established within the IBZ to enhance denitrification, can lead to production of the greenhouse gasses N₂O and CH₄. We investigated both the atmospheric emission of N₂O and CH₄, and waterborne losses of dissolved nitrogen, N₂O and CH₄ from two IBZ sites in Denmark for one year. The study showed that the emission of N₂O was relatively low, and that IBZ can even work as a sink of N₂O. On the contrary, the IBZ were sources of CH₄, although the emissions were comparable to those of natural wetlands and other drainage transport mitigation measures. The hydrology was identified as the key driver of emission pathways and their relative importance, as well as the nitrogen retention efficiency.