Effects and driving factors of domestic sewage from different sources on nitrous oxide emissions in a bog

Abstract

Direct sewage discharge may enhance soil nitrous oxide (N2O) emissions, worsening the greenhouse effect. However, the effects of sewage discharge into bogs on N2O flux, drivers, and influencing mechanisms remain unclear. Additionally, investigating the impact of reclaimed water on N2O flux is important for bog replenishment and water shortage alleviation. This study simulated sewage from different sources into a bog and analyzed N2O fluxes, soil (organic carbon, total nitrogen, ammonium nitrogen, nitrate nitrogen, total phosphorus, available phosphorus, pH, and electrical conductivity), plant (species richness and biomass), and microorganisms (ammonia-oxidizing archaea, napA, nirS, nirK, and nosZ genes). Results showed that the reclaimed water did not significantly change N2O flux, while 50% tap water mixed with 50% domestic sewage and domestic sewage significantly increased the N2O flux. Among soil factors, available nitrogen and pH were key in influencing N2O flux. Among plant parameters, species richness was the primary factor affecting N2O flux. Nitrogen transformation functional genes contributed the most to the increase in the N2O fluxes, with an increase in domestic sewage input leading to a higher abundance of these genes and subsequent N2O emissions. Therefore, domestic sewage should be considered, as it significantly increases N2O emissions by affecting the soil, plants, and microorganisms, thereby increasing the global warming potential. This study's findings suggest that using treated reclaimed water for bog replenishment could be an environmentally friendly approach to wetland management.