Salinity fronts and chemical behaviour of nutrient in Jiulongjiang Estuary

Based on the data obtained from the survey stations and sectional stations at a neap tide in the winter of 1997, it shows that a plume water fronts between the freshwater and seawater exists inside Jiulongjiang Estuary. This front was located in the inner estuary at ebb fast tide, and spreads to the outer estuary at flood fast tide. Besides, at ebb fast tide in the outer estuary there was a water front due to the merging of the plume water in the inner estuary and seawater from West Xiamen Harbour. This front plays an important role in the transportation of the plume water and seawater from West Xiamen Harbour. Both of SiO 2- 3 and NO - 3+NO - 2were quite conservative in winter, their distribution was principally determined by the mixing process between the freshwater of high Si, N and the seawater of low Si, N content, leading to a gradual decrease of Si, N concentration seaward in the estuarine region. PO 3- 4 was non conservative owing to buffer mechanism, its horizontal distribution doesn’t vary greatly.