2010年夏季珠江口海域溶解氧的分布特征和海气交换通量

根据2010年8月的调查资料,分析了珠江口海域溶解氧的分布特征,探讨了其与水体稳定性、营养盐、叶绿素a及CO2分压的关系。结果表明,溶解氧浓度由珠江口内向口外近海逐渐递增,在垂向上则随着水深由浅至深呈下降趋势。相关性分析显示,溶解氧在表底层的浓度差与温度差、盐度差和叶绿素a含量差都达到显著相关的水平,低氧区的形成与水体层化和有机质的降解耗氧密切相关,其中珠江冲淡水为浮游植物的生长和繁殖提供了丰富的N、P营养盐,而浮游生物的消亡和有机质的分解加剧了氧的亏损。溶解氧海气通量呈现明显的空间差异,其中河口上游表现为氧汇,而下游海域为氧源。

Characteristics of dissolved oxygen and O2 flux across the water-air interface of the Pearl River Estuary during summer 2010

Based on the cruise carried out in the Pearl River Estuary(PRE) in August 2010,DO,stability,the concentration of nutrient species(NO-3,NO-2,NH+4 and PO4-P),Chl a and carbon dioxide in the water column were analyzed.The results showed that DO displayed a decreasing trend from the upper to the lower reaches of the estuary,and the concentrations were in general higher in surface waters than bottom layer.This suggested that river inflows were probably the main factor in controlling the DO distribution in the PRE.A further analysis of these data showed that DO was closely related to temperature and salinity in the water column,while the vertical DO gradient was significantly correlated with temperature,salinity and Chl a.Our results indicated that low DO conditions can develop as a result of vertical stratification and organic matter decomposition during summer.Oxygen flux showed a marked spatial variation.As a whole,the freshwater region and mixed water region were oxygen sinks,while the seawater region was a source.