长江口溶解氧的分布特征及影响因素研究

Characteristics of Dissolved Oxygen and Its Affecting Factors in the Yangtze Estuary

根据2006-06、2006-08、2006-10对长江口及其毗邻海域的大面调查,分析航次B断面上的溶解氧及营养盐的分布特征,并对长江口外溶解氧低值的成因及其与海水稳定度、营养盐的关系进行初步探讨.结果表明,在6月航次中,DO值随着离岸距离的增加而逐渐增加,底层的DO值低于表层.8月份长江口及其邻近水域底层明显出现低氧状态,DO的最低值仅为1.1mg.L-1,该断面表观耗氧量AOU一般在2.79 mg.L-1以上,有氧的亏损发生,形成原因主要是海水层状结构稳定水交换较弱和有机物分解耗氧.10月份,海水层状结构发生变化,上下水层的垂直混合作用加剧,B断面DO分布随着离岸距离的增加逐渐增加.相关性分析显示,表底层的ΔDO与ΔΔZρ、ΔNO3-和ΔDIP都达到显著相关的水平.其中ΔDO与ΔΔZρ呈极显著的正相关,而与ΔNO3-、ΔDIP呈显著负相关关系.长江径流N、P污染物输入的不断增加为低氧区域表层浮游植物的生长提供了丰富的营养盐,从而加剧了该水域的氧亏损.

The cruises on hypoxia research were carried out in the Yangtze Estuary and adjacent area of the East China Sea on June, August and October, 2006. DO, stability and the concentration of nitrate and phosphate in the section B were analyzed. The result indicates that there is distinct difference among the concentration of DO in the section B of the three cruises. The DO distribution is higher in surface water but lower in bottom. The oxygen minimum value （1.1 mg· L^-1） is found at the bottom in August, and the apparent oxygen utilization （AOU） is higher than 2.79 mg· L^-1 in the section B. The strong halocline above the hypoxic zone, as a result of affluent water from the coastwise, Taiwan Warm Current, and the high concentration of organic substance are major factors causing the formation of the hypoxia. The stability of the seawater goes down, the vertical mixing affect the DO through its effect on stratification, in October. △DO is primarily affected by the stability and the concentration of △NO3 , △DIP.