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

摘要

Most aquatic ecosystems contribute elevated N_2 O 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 N_2 O emission along Poyang Lake aquatic continuum during the flood season from 15 July 2013 to 10 August 2013. The results showed the N_2 O concentrations, the ratio of N_2O/dinitrogen(N_2) gases production, N_2 O emission and denitrification rates ranged from 0.10 to 1.11 μg N/L,- 0.007% to 0.051%,- 9.73 to 127 μg N/m2/hr and 1.33 × 104to31.9 × 104μg N_2/m2/hr, respectively, across the continuum. The average N_2 O concentrations,the ratio of N_2O/N_2 and N_2O emission was significantly lower in wetlands as compared to the rivers and lake(p < 0.01). The significantly high denitrification rate and low N_2 O emission together highlighted that most N_2 O can be converted into N_2 via near complete denitrification in the Poyang Lake wetlands. Our study suggests that the wetlands might impact N_2 O budget in an integrated aquatic ecosystems. Moreover, N_2 O emission from different aquatic ecosystem should be considered separately when quantifying the regional budget in aquatic ecosystem.