Abstract Inland waters are significant sources of atmospheric nitrous oxide (N 2 O), and their emissions are expected to rise rapidly due to human activities. However, current estimates remain highly uncertain, partly because sparse field measurements and existing models fail to capture fine‐scale variations in N 2 O emissions, especially due to the interactions between fluid dynamics and biogeochemical drivers. This study developed an N 2 O module in the Environmental Fluid Dynamics Code (EFDC), a comprehensive numerical model capable of simulating hydrodynamics and water quality in different inland aquatic systems, by incorporating key nitrogen (N) processes that influence N 2 O production and emissions. The developed model was applied to a typical mountainous reservoir in China, and reliably reproduced the temporal and spatial variations in N 2 O concentrations and fluxes. Seasonal patterns of N 2 O fluxes were primarily driven by temperature, stratification, and nutrient availability, with autumn exhibiting the peak values. In contrast, spatial variations were mainly regulated by fluid dynamics and nutrient availability, with the highest N 2 O fluxes observed in the main part of the reservoir. Furthermore, the whole‐reservoir N 2 O budget indicated that sediments were the primary source of N 2 O, which is mainly produced via denitrification under low dissolved oxygen conditions, underscoring the importance of understanding the sedimentary N cycle. Overall, our model enables the quantification of significant spatiotemporal variations in N 2 O emissions from inland waters and unravels the underlying mechanisms, thereby enhancing our mechanistic understanding of N 2 O dynamics and improving the quantification accuracy of N 2 O emissions at broader scales.
Shi et al. (Fri,) studied this question.