Modeling nitrous oxide emission from rivers: a global assessment
Modeling nitrous oxide emission from rivers: a global assessment
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河流一氧化二氮排放建模：全球评估
DOI：
10.1111/gcb.13351
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发表时间：
2016-11-01
影响因子：
11.6
通讯作者：
Dahlgren, Randy A.
中科院分区：
文献类型：
--
作者：
Hu, Minpeng;Chen, Dingjiang;Dahlgren, Randy A.
对全球河流一氧化二氮(N2O)排放量的估计包含很大的不确定性。我们进行了一项荟萃分析，综合了169个已发表文献的观察结果，以估计全球河流N2O的排放速率和排放因子。河流N2O通量与NH_4、NO_3和DIN(NH_4+NO_3)浓度、负荷和产量显著相关。排放因子Ef(A)(即N2O排放速率与DIN负荷之比)和EF(B)(即N2O与DIN浓度之比)具有可比性，与氮浓度、负荷、产水量和排水量呈负相关，与溶解有机碳/DIN比呈正相关。在对全球、温带和亚热带数据集的基于EF(A)或EF(B)的82个潜在回归模型分别进行评估后，确定了DIN产生量乘以流域面积的幂函数，以提供全球和气候区模型的N2O排放速率与观测数据之间的最佳拟合(EF(A)：全球和气候带模型的R2=0.92，n=70；EF(B)：全球模型的R2=0.91，气候带模型的R2=0.90，n=70)。利用最近对6400条河流DIN负荷的估计，模型估计全球河流N2O排放量为29.6-35.3(平均值=32.2)Gg-N2O-Nyr(-1)，排放系数为0.16-0.19%(平均值=0.17%)。根据千年生态系统评估的全球协调、实力排序、技术花园和适应马赛克情景，预计2050年全球河流N2O排放量将比本世纪头十年分别增加35%、25%、18%和3%。以前的研究可能高估了全球河流N2O的排放量(300-2100 Gg N2O-Nyr(-1))，因为它们忽略了排放因子值随着氮素水平和渠道规模的增加而下降，以及忽略了不同氮素形态对应的排放因子的差异。通过改进排放系数估计、沿整个河流网络纵向扩展测量以及改进对全球河流氮负荷的估计，将进一步提高河流N2O排放量的估计。
Estimates of global riverine nitrous oxide (N2O) emissions contain great uncertainty. We conducted a meta-analysis incorporating 169 observations from published literature to estimate global riverine N2O emission rates and emission factors. Riverine N2O flux was significantly correlated with NH4, NO3 and DIN (NH4 + NO3) concentrations, loads and yields. The emission factors EF(a) (i.e., the ratio of N2O emission rate and DIN load) and EF(b) (i.e., the ratio of N2O and DIN concentrations) values were comparable and showed negative correlations with nitrogen concentration, load and yield and water discharge, but positive correlations with the dissolved organic carbon : DIN ratio. After individually evaluating 82 potential regression models based on EF(a) or EF(b) for global, temperate zone and subtropical zone datasets, a power function of DIN yield multiplied by watershed area was determined to provide the best fit between modeled and observed riverine N2O emission rates (EF(a): R-2 = 0.92 for both global and climatic zone models, n = 70; EF(b): R-2 = 0.91 for global model and R-2 = 0.90 for climatic zone models, n = 70). Using recent estimates of DIN loads for 6400 rivers, models estimated global riverine N2O emission rates of 29.6-35.3 (mean = 32.2) Gg N2O-N yr(-1) and emission factors of 0.16-0.19% (mean = 0.17%). Global riverine N2O emission rates are forecasted to increase by 35%, 25%, 18% and 3% in 2050 compared to the 2000s under the Millennium Ecosystem Assessment's Global Orchestration, Order from Strength, Technogarden, and Adapting Mosaic scenarios, respectively. Previous studies may overestimate global riverine N2O emission rates (300-2100 Gg N2O-N yr(-1)) because they ignore declining emission factor values with increasing nitrogen levels and channel size, as well as neglect differences in emission factors corresponding to different nitrogen forms. Riverine N2O emission estimates will be further enhanced through refining emission factor estimates, extending measurements longitudinally along entire river networks and improving estimates of global riverine nitrogen loads.