Dissolved nitrous oxide and emission relating to denitrification across the Poyang Lake aquatic continuum

Most aquatic ecosystems contribute elevated N₂O to atmosphere due to increasing anthropogenic nitrogen loading. To further understand the spatial heterogeneity along an aquatic continuum from the upriver to wetland to lake to downriver, the study was conducted on spatial variations in N₂O emission along Poyang Lake aquatic continuum during the flood season from 15 July 2013 to 10 August 2013. The results showed the N₂O concentrations, the ratio of N₂O/dinitrogen (N₂) gases production, N₂O emission and denitrification rates ranged from 0.10 to 1.11μgN/L, -0.007% to 0.051%, -9.73 to 127μgN/m²/hr and 1.33×10⁴ to 31.9×10⁴μgN₂/m²/hr, respectively, across the continuum. The average N₂O concentrations, the ratio of N₂O/N₂ and N₂O emission was significantly lower in wetlands as compared to the rivers and lake (p<0.01). The significantly high denitrification rate and low N₂O emission together highlighted that most N₂O can be converted into N₂ via near complete denitrification in the Poyang Lake wetlands. Our study suggests that the wetlands might impact N₂O budget in an integrated aquatic ecosystems. Moreover, N₂O emission from different aquatic ecosystem should be considered separately when quantifying the regional budget in aquatic ecosystem.