中文关键词农业源溪流N₂O间接排放N₂O间接排放系数(EF_5r)降雨硝态氮反硝化 英文关键词agricultural headwater streamindirect N₂O emissionindirect N₂O emission factor (EF_5r)rainfallnitratedenitrification

作者	单位	E-mail
田琳琳	中国科学院水利部成都山地灾害与环境研究所, 成都 610041 中国科学院山地表生过程与生态调控重点实验室, 成都 610041 中国科学院大学, 北京 100049	tianlin025@163.com
王正	中国科学院水利部成都山地灾害与环境研究所, 成都 610041 中国科学院山地表生过程与生态调控重点实验室, 成都 610041 中国科学院大学, 北京 100049
朱波	中国科学院水利部成都山地灾害与环境研究所, 成都 610041 中国科学院山地表生过程与生态调控重点实验室, 成都 610041	bzhu@imde.ac.cn

中文摘要 农业源溪流与农田生态系统有着紧密的水文连接，其会随着农业非点源氮（N）污染的加剧而成为重要的N汇和氧化亚氮（N₂O）间接排放源.本研究采用静态暗箱-气相色谱法于2015年6~9月（所研究区域的雨季）原位测定了长江上游紫色土丘陵区农业源溪流的N₂O间接排放通量.结果表明，农业源溪流雨季中N₂O平均排放通量为12.8 μg·（m²·h）^-1，接近其所在区域内同季节农田的N₂O直接排放水平，是重要的农业N₂O间接排放源.该农业源溪流中N₂O间接排放系数值（EF_5r=0.01%）远低于IPCC的建议值（0.25%）和重新计算的全球平均值（0.20%），然而，全球EF_5r的现有数据量仍十分有限、且有较大的空间差异，应加强对此类N₂O间接排放的研究，从而进一步修正EF_5r的精度、减少N₂O间接排放估算的误差.本研究的N₂O间接排放通量与水中NO₃^--N浓度正相关，反硝化是N₂O的主要产生过程.雨季中较强的降雨（如连续降雨日内降雨>9 mm）可促进溪流中NO₃^--N浓度在雨后短期内急剧升高，进而激发水中N₂O间接排放通量的明显增加. 英文摘要 Agricultural headwater streams have a close hydrologic connection with adjacent farmland ecosystems. Based on the aggravation of agricultural nonpoint source of nitrogen (N) pollution, these streams can become an important sink of N and source of indirect nitrous oxide (N₂O) emission. In this study, indirect N₂O emissions from an agricultural headwater stream in the hilly area of purple soil in the upper reach of the Yangtze River were measured in situ using the closed static chamber-GC technique during the rainy season (June to September 2015). The results show that the headwater stream is a source of indirect N₂O emissions, with a mean emission rate of 12.8 μg·(m²·h)^-1, which is close to the direct N₂O emission level from local farmland during the same season. The indirect N₂O emission factor (EF_5r=0.01%) determined in this study is much lower than the default value proposed by the Intergovernmental Panel on Climate Change (0.25%; IPCC, 2006) for the estimation of indirect agricultural N₂O emissions and far lower than the recalculated mean value (0.20%) based on available global data. However, based on the limited number of studies on EF_5r and the high spatial variations among them, more in situ observations are needed and vital to generate more accurate EF_5r values and reduce the uncertainty of indirect N₂O estimations calculated based on the EF_5r. The indirect N₂O fluxes are positively correlated with the NO₃^--N concentrations of the stream. Thus, denitrification is the main process of N₂O production. Moreover, the indirect N₂O fluxes could be notably promoted by the rapid increase of the NO₃^--N concentrations that were driven by rainfall>9 mm during days with continuous rain.

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