Mechanism underlying revetment effects on the spatial distribution of nitrogen removal and N2O emissions in riparian zones at summer

Abstract

Study Region, Shanghai, China, Study FocusUrban riparian zones can mitigate or even control nitrogen pollution in rivers through nitrification and denitrification processes. However, these processes also produce N2O, a potent greenhouse gas. During urbanization, various types of revetments have been constructed in riparian zones. These revetments alter the exchange of materials and energy between the riparian zone and the river, which in turn affects the nitrification and denitrification processes in the riparian zone. However, the mechanisms by which revetments impact nitrogen removal and N2O emissions in riparian zones are not yet clear, and the ways in which revetments balance nitrogen removal and N2O emissions remain unknown. Therefore, in a single river section, natural (NR), permeable (PR), and impervious revetment (IR) types were replicated. Measurements are taken of nitrogen removal, N2O emissions, and related environmental indicators in both the river-riparian interface (RRI) and the riparian zone area outside the RRI (RZ). The study analyzes the differences in environmental factors, nitrification and denitrification potentials, and N2O emission rates among the different revetments to identify the main factors affecting nitrogen removal and N2O emissions in the riparian zone. It also explores the potential mechanisms by which revetments influence the spatial distribution of nitrogen removal and N2O emissions in the summer riparian zone.New Hydrological Insights for the Region: PR exhibit greater denitrification potential and lower N2O emission rates. The denitrification potential is higher in the RRI compared to RZ, while the N2O emission rate is lower than in RZ. nirK is the primary factor influencing denitrification potential, whereas nosZII predominantly affects N2O emissions. The lower soil carbon-to-nitrogen ratio in PR increases the abundance of nirK, thereby enhancing the riparian zone's denitrification potential. Moreover, greater aboveground vegetation biomass increases the abundance of nosZII, reducing the N2O emission rate. The study results could provide guidance for urban ecological restoration and greenhouse gas emission reduction.