Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, School of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China.
Sci Total Environ. 2021 May 15;769:144558. doi: 10.1016/j.scitotenv.2020.144558. Epub 2021 Jan 17.
Freshwaters are receiving growing concerns on atmospheric carbon dioxide (CO) and methane (CH) budget; however, little is known about the anthropogenic sources of CO and CH from river network in agricultural-dominated watersheds. Here, we chose such a typical watershed and measured surface dissolved CO and CH concentrations over 2 years (2015-2017) in Jurong Reservoir watershed for different freshwater types (river network, ponds, reservoir, and ditches), which located in Eastern China and were impacted by agriculture with high fertilizer N application. Results showed that significantly higher gas concentrations occurred in river network (CO: 112 ± 36 μmol L; CH: 509 ± 341 nmol L) with high nutrient concentrations. Dissolved CO and CH concentrations were supersaturated in all of the freshwater types with peak saturation ratios generally occurring in river network. Temporal variations in the gas saturations were positively correlated with water temperature. The saturations of CO and CH were positively correlated with each other in river network, and both of these saturations were also positively correlated with nutrient loadings, and negatively correlated with dissolved oxygen concentration. The highly agricultural river network acted as significant CO and CH sources with estimated emission fluxes of 409 ± 369 mmol m d for CO and 1.6 ± 1.2 mmol m d for CH, and made a disproportionately large, relative to the area, contribution to the total aquatic carbon emission of the watershed. Our results suggested the aquatic carbon emissions accounted for 6% of the watershed carbon budget, and fertilizer N and watersheds land use played a large role in the aquatic carbon emission.
淡水受到越来越多的关注，因为大气中的二氧化碳 (CO) 和甲烷 (CH) 收支平衡；然而，对于农业为主的流域河网中 CO 和 CH 的人为来源知之甚少。在这里，我们选择了这样一个典型的流域，并在 2015 年至 2017 年期间测量了 Jurong 水库流域不同淡水类型（河网、池塘、水库和沟渠）的地表溶解 CO 和 CH 浓度，这些地区位于中国东部，受到高化肥 N 应用的农业影响。结果表明，在富营养化的河网中（CO：112±36 μmol L；CH：509±341 nmol L），气体浓度显著升高。所有淡水类型中的溶解 CO 和 CH 浓度均过饱和，峰值饱和度比通常出现在河网中。气体饱和度的时间变化与水温呈正相关。河网中 CO 和 CH 的饱和度相互正相关，两者的饱和度均与营养负荷呈正相关，与溶解氧浓度呈负相关。高度农业化的河网是 CO 和 CH 的重要来源，CO 的排放通量估计为 409±369 mmol m d，CH 的排放通量为 1.6±1.2 mmol m d，对流域水生生碳排放量的贡献相对于面积而言不成比例地大。我们的结果表明，水生生碳排放量占流域碳预算的 6%，化肥 N 和流域土地利用对水生生碳排放量有很大影响。
