Distribution and variation of dissolved inorganic nitrogen in Changjiang Estuary and adjacent waters

Based on the data obtained from the quarterly investigations in the Changjiang estuary and its adjacent water in 2004,the distributions and variations of DIN are discussed.The results show that the concentrations of DIN were higher near the Changjiang estuary.Generally,the concentration of NO3-N was higher in the surface than in the bottom in shore;the opposite distributions off shore.Due to biological and chemical effect,vertical section distribution of NO2-N and NH4-N is comparatively complicated.The distributions of NO3-N varied with increase and decrease of runoff and with enlarge and reduce of the extent of Changjiang dilution water.However,the concentration of NO2-N was higher in spring,and NH4-N was higher in winter.Each monthly DIN/ PO4-P ratios was much higher than Redfield ratios.Compared with the data of 1985~1986,the concentrations of DIN were increased 2.2 times,DIN/ PO4-P ratios were ascended 1.4 times since 20 years,which depended on the increasing of DIN concentrations.The removals of DIN in the estuary showed that aside from biological removal,there was a mainly affection from seawater dilution.