Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Jiangsu Key Laboratory of Agricultural Meteorology, Nanjing University of Information Science & Technology, Nanjing, 210044, China; 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, Jiangsu Key Laboratory of Agricultural Meteorology, Nanjing University of Information Science & Technology, Nanjing, 210044, China.
Environ Pollut. 2019 Aug;251:185-192. doi: 10.1016/j.envpol.2019.04.076. Epub 2019 Apr 22.
Agriculture is one of major emission sources of nitrous oxide (NO), an important greenhouse gas dominating stratospheric ozone destruction. However, indirect NO emissions from agriculture watershed water surfaces are poorly understood. Here, surface-dissolved NO concentration in water bodies of the agricultural watershed in Eastern China, one of the most intensive agricultural regions, was measured over a two-year period. Results showed that the dissolved NO concentrations varied in samples taken from different water types, and the annual mean NO concentrations for rivers, ponds, reservoir, and ditches were 30 ± 18, 19 ± 7, 16 ± 5 and 58 ± 69 nmol L, respectively. The NO concentrations can be best predicted by the NO-N concentrations in rivers and by the NH-N concentrations in ponds. Heavy precipitation induced hot moments of riverine NO emissions were observed during farming season. Upstream waters are hot spots, in which the NO production rates were two times greater than in non-hotspot locations. The modeled watershed indirect NO emission rates were comparable to direct emission from fertilized soil. A rough estimate suggests that indirect NO emissions yield approximately 4% of the total NO emissions yield from N-fertilizer at the watershed scale. Separate emission factors (EF) established for rivers, ponds, and reservoir were 0.0013, 0.0020, and 0.0012, respectively, indicating that the IPCC (Inter-governmental Panel on Climate Change) default value of 0.0025 may overestimate the indirect NO emission from surface water in eastern China. EF was inversely correlated with N loading, highlighting the potential constraints in the IPCC methodology for water with a high anthropogenic N input.
农业是一氧化二氮（NO）的主要排放源之一，NO 是一种重要的温室气体，主导着平流层臭氧的破坏。然而，农业流域水表面的间接 NO 排放还不太清楚。在这里，测量了中国东部农业流域水体中表面溶解的 NO 浓度，该地区是最密集的农业区之一，为期两年。结果表明，不同水类型的水样中溶解的 NO 浓度不同，河流、池塘、水库和沟渠的年平均 NO 浓度分别为 30±18、19±7、16±5 和 58±69 nmol L。NO 浓度可以通过河流中的 NO-N 浓度和池塘中的 NH-N 浓度来最好地预测。在农忙季节，强降水引发了河流中 NO 排放的热点时刻。上游水域是热点区域，其中 NO 的产生速率比非热点区域高两倍。模拟的流域间接 NO 排放速率与施肥土壤的直接排放相当。粗略估计表明，间接 NO 排放约占流域尺度上 N 肥料总 NO 排放的 4%。为河流、池塘和水库分别建立的单独排放因子（EF）分别为 0.0013、0.0020 和 0.0012，表明 IPCC（政府间气候变化专门委员会）默认值 0.0025 可能高估了中国东部地表水的间接 NO 排放。EF 与 N 负荷呈反比，突出了高人为 N 输入水体中 IPCC 方法的潜在局限性。
