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

Most aquatic ecosystems contribute elevated NO 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 NO emission along Poyang Lake aquatic continuum during the flood season from 15 July 2013 to 10 August 2013. The results showed the NO concentrations, the ratio of NO/dinitrogen (N) gases production, NO emission and denitrification rates ranged from 0.10 to 1.11μgN/L, -0.007% to 0.051%, -9.73 to 127μgN/m/hr and 1.33×10 to 31.9×10μgN/m/hr, respectively, across the continuum. The average NO concentrations, the ratio of NO/N and NO emission was significantly lower in wetlands as compared to the rivers and lake (p<0.01). The significantly high denitrification rate and low NO emission together highlighted that most NO can be converted into N via near complete denitrification in the Poyang Lake wetlands. Our study suggests that the wetlands might impact NO budget in an integrated aquatic ecosystems. Moreover, NO emission from different aquatic ecosystem should be considered separately when quantifying the regional budget in aquatic ecosystem.