Analysis of trend of nutrient structure and influencing factors in Changjiang Estuary and its adjacent sea during 23 years

According to monitoring data from 1984 to 2006,the trend of disolved inorganic nitrogen(DIN),phosphate(PO4-P) and their ratio in Changjiang Estuary and its adjacent sea were analyzed.The results showed that the concentrations of DIN and PO4-P had been increasing,while the ratio of which has been decreasing during 23 years.The concentrations of DIN and PO4-P range from 2.13~140.0 μmol/L and 0.0211~1.6955 μmol/L in Changjiang Estuary,respectively,while 1.94~95.69 μmol/L and 0.0226~1.380 6 μmol/L in its adjacent sea,respectively.The N/P ranges from 51.24~580.56 and 64.38~339.73 in the study area,respectively.And currently the nutrient limiting factor was still phosphorus.The change in nutrient structure may result from the decrease of sendiment load in river and N/P in chemical fertilizer in farmland.