title: Direct measurement of dissolved N₂ and denitrification along a subtropical river-estuary gradient, China.
abstract: The spatial pattern and seasonal variation of denitrification were investigated during 2010-2011 in the Jiulong River Estuary (JRE) in southeast China. Dissolved N₂ was directly measured by changes in the N₂:Ar ratio. The results showed that excess dissolved N₂ ranged from -9.9 to 76.4 μmol L⁻¹. Tidal mixing leads to a seaward decline of dissolved gaseous concentrations and water-air fluxes along the river-estuary gradient. Denitrification at freshwater sites varied between seasons, associated with changes in N input and water temperature. The denitrification process was controlled by the nitrate level at freshwater sites, and the excess dissolved N₂ observed at the tidal zone largely originated from upstream water transport. Compared to other estuaries, JRE has a relative low gaseous removal efficiency (E(d)=12% of [DIN]; annual N removal=24% of DIN load), a fact ascribed to strong tidal mixing, coarse-textured sediment with shallow depth before bedrock and high riverine DIN input.
authors.affiliation: State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, PR China.
authors.forename: Jiezhong
authors.initials: J
authors.lastname: Wu
authors.forename: Nengwang
authors.initials: N
authors.lastname: Chen
authors.forename: Huasheng
authors.initials: H
authors.lastname: Hong
authors.forename: Ting
authors.initials: T
authors.lastname: Lu
authors.forename: Longjian
authors.initials: L
authors.lastname: Wang
authors.forename: Zhuhong
authors.initials: Z
authors.lastname: Chen
mesh_terms: D002681:China; D058440:Denitrification; D004784:Environmental Monitoring; D063366:Estuaries; D009584:Nitrogen / Q000032:analysis*; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D012623:Seawater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data
chemical_list: D014874:Water Pollutants, Chemical; D009584:Nitrogen