Direct measurement of dissolved N2 and denitrification along a subtropical river-estuary gradient, China

► Denitrification in Jiulong River Estuary was examined by direct measurement of N2. ► Tidal mixing leads to a seaward decline of excess dissolved N2 and water-air flux. ► Denitrification varied between seasons, associated with N input and temperature. ► A low denitrification removal due to strong mixing, poor sediment and high N level.