production，emission and export of nitrous oxide from the Jiulong river estuary

In order to investigate the spatio-temporal variations of dissolved nitrous oxide (N₂O), and to explore the main processes and key factors affecting the distribution of N₂O in the Jiulong river estuary. N₂O concentration and the related physical and chemical parameters were measured along the estuary with salinity gradient in July 2020 and December 2020. Nitrification rate and N₂O production rate were also determined via incubation experiments. A Land-Ocean Interaction Coastal Zone (LOICZ) box model was used to evaluate the N₂O budget in the Jiulong river estuary, including river input, water-gas exchange, biological production, and estuarine output fluxes. The results showed that the concentration and saturation of N₂O in the Jiulong river estuary have significant spatial variations, ranging from 15.3～50.2 nmol/L and 214.6%～699.1%, respectively. The water-air flux of N₂O was 5.02×10³ mol/d in December 2020 and 4.09×10³ mol/d in July 2020, indicating that the Jiulong river estuary was an important source of atmospheric N₂O. Nitrification was the main process of N₂O production, which was thus the main process of regulating the distribution of N₂O in the estuary. The amount of N₂O produced by nitrification to total N₂O output in the Jiulong river estuary was 53.8% in July 2020 and 50.3% in December 2020.