CONCENTRATION VARIATION AND FLUX ESTIMATION OF DISSOLVED INORGANIC NUTRIENT FROM THE CHANGJIANG RIVER INTO ITS ESTUARY

Based upon the monthly dissolved nutrient(C?N?P?Si)concentrations and runoff discharge during the past several years at the Datong control section,which divides the Changjiang River main stream and the Changjiang River estuary,concentration variations are discussed and nutrient fluxes are estimated The concentrations of different elements showed different variation characteristics The concentration of HCO - 3 changes little while that of NO - 3?NO - 2?PO 3- 4have an increasing trend and that of CO 2?NH + 4 and SiO 2- 3 have a declining trend The monthly mean flux and annual mean fluxes C?N?P?Si are estimated Further,fitting functions between the discharge and the fluxes are obtained to predict the monthly flux with the monthly discharge