Inorganic Nitrogen Fluxes at the Sediment-water Interface in Tidal Flats of the Yangtze Estuary
长江口潮滩沉积物－水界面无机氮交换通量

Inorganic nitrogen fluxes at the sediment-water interface of seven typical sites in tidal flats of the Yangtze estuary had been determined seasonally during more than three years. The results revealed that the sediment-water exchanges of inorganic nitrogen appeared to be of complicated spatial differences and seasonal variations. The measured fluxes of NO-3-N and NH+4-N in the Yangtze estuary were higher than those in other estuaries, varying respectively from -32.82 to 24.13 mmol·m-2·d-1 and from -18.45 to 10.65 mmol·m-2·d-1. However, the fluxes of NO-2/sub>-N were very low, and only varied from -1.15 to 2.82 mmol·m-2·d-1. The spatial and seasonal differences between the upper and lower estuary for the NO-3-N fluxes were observed clearly, but the NH+4-N fluxes exhibited the spatial and seasonal differences between the south and north bank. It had been recognized that the NH+4-N exchange behavior was mainly controlled by the salinity, whereas the NO-3-N exchange behavior was influenced by the different combinations of the sediment grain size, nitrate concentration in overlying water, sediment organic matter content, water temperature and dissolved oxygen concentration.