夏季珠江口水域溶解氧的特征及影响因素

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

对1996年和1999年夏季珠江口的盐度、温度、溶解氧、营养盐等水质调查结果进行了统计分析,结果表明:夏季伶仃洋水体溶解氧的表底层浓度存在显著差异。表层的溶解氧浓度与表层的盐度和无机氮浓度都显著相关,而表层营养盐的浓度为表层溶解氧浓度水平的主要影响因素。通过一个简单的二元线性回归模型分析,径流冲淡水与外海水之间的盐度层化作用比温度层化作用对底层溶解氧的浓度水平影响更为明显。相关性分析显示,水体的层化作用与底层水体溶解氧的浓度呈极显著的负相关关系;同时层化作用与表底层的溶解氧浓度差极显著正相关。潮汐周期循环对层化作用产生一定的影响。因此,在珠江口水域,夏季表层水体溶解氧的含量水平主要取决于营养盐N的浓度;底层水体溶解氧含量的主要影响因素是咸淡水交汇形成的盐度差的层化作用,潮汐混合通过影响层化作用从而影响溶解氧的浓度。

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.