The Yellow Sea (YS) and the East China Sea (ECS) are marginal seas of the western North Pacific, and influenced by the land runoff and human perturbations. Based on field investigations carried out during 2018−2021, the spatial and temporal distribution patterns of dissolved N₂O and NH₂OH concentrations and sea-to-air N₂O fluxes in the YS and the ECS were studied, as well as their regional contribution to the atmospheric N₂O. Physical constraints and microbial processes were the primary drivers of spatiotemporal variation of dissolved N₂O, and revealed the seasonal difference. The annual N₂O emission from the YS and the ECS was estimated to be 1.8×10^-2 Tg N₂O yr^-1, contributing about 0.33% of global oceanic N₂O emission. Meanwhile, the N₂O isotopic analysis were conducted to explore the microbial production pathways of dissolved N₂O in the water column of the ECS. Almost equal contributions of archaeal N₂O production (archaeal nitrification and/or hybrid mechanism) and nitrifier-denitrification to the total in situ N₂O production were identified for the shallow water, but archaeal nitrification was responsible for ~80% of the deeper N₂O production.

Nitrous oxide (N2O),Yellow Sea,East China Sea,flux,production processes