右江百色水库下游断面低溶解氧形成原因分析

Cause Analysis of Low Dissolved Oxygen Formation in Downstream Section of Baise Reservoir in Youjiang River

广西右江东笋断面溶解氧(DO)呈现5—11月浓度较低,12月及1—4月浓度较高的变化规律。从水温、藻类呼吸、沉积物耗氧、有机物耗氧、上游来水等方面分析了东笋断面低DO形成的原因。结果表明,5—11月东笋断面DO浓度较低,主要是受夏季高温和水利工程运行等非污染型因素的影响。右江流域夏秋季水温较高,限制了水体DO浓度的上限。热分层现象导致百色水库中层水体DO浓度较低,而水利枢纽发电时的下泄水正是中层水体,因此,下泄水DO浓度低是导致5—11月东笋断面DO浓度低的主要原因。东笋河段沉积物和有机物耗氧对DO浓度的影响很小,藻类呼吸作用对DO浓度的影响有限。

The dissolved oxygen(DO)concentration of Dongsun section in Guangxi Youjiang River follows the pattern of a lower concentration from May to November,a higher one from December to the following April.This paper analyzes the causes of low DO formation in Dongsun section from the aspects of water temperature,algae respiration,sediment oxygen consumption,organic matter oxygen consumption and upstream water.The results show that the low DO in Dongsun section from May to November is mainly caused by non-polluting factors such as high temperature in summer and water conservancy project operation.The high water temperature in summer and autumn in the Youjiang Basin limits the upper limit of DO concentration in water.Thermal stratification leads to low DO concentration in the middle layers of the Baise reservoir,which is used for power generation,and the low DO concentration in the discharge water is the main reason for the low DO concentration in Dongsun section from May to November.The sediment and organic matter consumption have little effect on DO concentration in Dongsun section,and algal respiration has a limited effect on DO concentration.