Characteristics of Dissolved Oxygen and Its Affecting Factors in the Pearl River Estuary in Summer

This paper analyses the temperature,salinity,DO and the concentrations of nutrients N and P in Lingdingyang in summer of 1999 and 1996.The results indicate there is distinct difference between the concentrations of DO in surface and bottom waters.The concentrations of DO show great correlation with S and the concentrations of N in surface water but the latter is the most affecting factor for DO.The halocline in the Lingdingyang is more important for the concentrations of DO in bottom water than the thermocline.The greater the differences of S between surface and bottom waters are,the greater the variations of DO's concentrations are,and the lower the concentrations of DO the bottom water are.The tidal cycle has effect on the stratification.So,the concentration of DO in surface water is primarily affected by the content of DIN in the Lingdingyang in summer.And the mainly controlling factor for the concentrations of DO in bottom water is stratification caused by the convergence of the discharges and outer water masses.The tidal mixing affects the DO through its effect on stratification.