Land-Air Exchanges of Various Gaseous Nitrogen Species in an Urban Wetland Based on In Situ Flux Observations

Abstract

Wetlands are universally recognized as hotspots for nitrogen cycling and gaseous nitrogen emissions. In this study, the fluxes of nitric oxide (NO), nitrogen dioxide (NO₂), ammonia (NH₃), and nitrous oxide (N₂O) were observed seasonally in the mud and waterfront plots of an urban wetland in eastern China using a dynamic flux chamber. The results revealed that the fluxes of NO, NO₂, and NH₃ displayed a diurnal pattern of higher values during the day and lower values at night, which was opposite to that of N₂O. The average annual emissions of NO, NH₃, and N₂O were 0.16 ± 0.04, 0.59 ± 0.03, and 8.81 ± 0.44 kg N ha⁻¹ yr⁻¹, respectively. Conversely, NO₂ exhibited deposition, with an annual flux of 1.51 ± 0.03 kg N ha⁻¹ yr⁻¹. Given the evolving area of urban wetlands, the emissions of gaseous nitrogen, particularly N₂O, deserve substantial attention.