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We analyzed the N2O content of surface seawater sampled from Prydz Bay,Antarctica,on a cruise track between 30°S and 30°N during the twenty-second Chinese National Antarctic Research Expedition during austral summer,2006.The surface water showed an average pN2O value of 311.9±7.6 nL.L-1 (14.1±t0.4 nmol.L-1),which was slightly undersaturated.The air-sea N2O flux in the region was -0.3±0.8 μmol·m-2·d-1; however,N2O in the surface water was oversaturated in most stations along the cruise track.Saturation anomalies were greater than 10％,with a maximum of 54.7％ being observed at the Equator,followed by 31％ at 10°N in the Sulu Sea.The air-sea fluxes at these locations were 12.4 and 4 μmol.m-2·d-l,respectively.Overall,the results indicated that surface water in Prydz Bay was near equilibrium with atmospheric N2O,and that ocean waters in lower latitudes acted as a N2O source.Physical processes such as stratification,ice-melt water dilution,and solar radiation dominate the factors leading to N2O saturation of surface water of Prydz Bay,while biological production and upwelling are primarily responsible for the N2O oversaturation of surface water observed in subtropical and tropical regions along the cruise track.