Modeling Riverine N2O Sources, Fates, and Emission Factors in a Typical River Network of Eastern China,Environmental Science & Technology

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Modeling Riverine N2O Sources, Fates, and Emission Factors in a Typical River Network of Eastern China
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2021-09-14 , DOI: 10.1021/acs.est.1c01301
Minpeng Hu _{1,

2} , Bingqing Li _{1,

2} , Kaibin Wu _{1,

3} , Yufu Zhang _{1,

2} , Hao Wu _{1,

2} , Jia Zhou _{1,

2} , Dingjiang Chen _{1,

2,

3}

Affiliation

Estimates of riverine N₂O emission contain great uncertainty because of the lack of quantitative knowledge concerning riverine N₂O sources and fates. Using a 3.5-year record of monthly N₂O measurements from the Yongan River network of eastern China, we developed a mass-balance model to address the riverine N₂O source and sink processes. We achieved reasonable model efficacies (R² = 0.44–0.84, Nash–Sutcliffe coefficients = 0.40–0.80) across three tributaries and the entire river system. Estimated riverine N₂O loads originated from groundwater (38–88%), surface runoff (3–26%), and in-stream production (4–48%). Estimated in-stream losses via atmospheric release + complete denitrification accounted for 76, 95, 25, and 89% of riverine N₂O fate for the agricultural, residential, forest, and entire river system, respectively. Considering limited complete denitrification, the model estimated an upper-bound riverine N₂O emission rate of 2.65 ton N₂O–N km^–2 year^–1 for the entire river system. Riverine N₂O emission estimates were of comparable magnitude to those estimated with a power-law scaling model. Riverine N₂O emissions using the IPCC default emission factor (0.26%) overestimated emissions by 3–15 times, whereas the dissolved N₂O concentration-based emission factor overestimated or underestimated emissions. This study highlights the importance of combining comprehensive information on N₂O sources and fates to achieve accurate riverine N₂O emission estimates.

更新日期：2021-10-06

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