2013—2020年泸沽湖溶解氧随时间变化规律及主要影响因素分析

泸沽湖坐落于川滇交界处,是中国典型高原淡水湖泊。对泸沽湖水质的客观评价对于其规划保护及保护成效评估极为重要。鉴于溶解氧常常成为决定泸沽湖水质类别的唯一关键指标,在综合分析泸沽湖2013—2020年连续8年水环境主要指标变化的基础上,着重分析了溶解氧随季节、年际等的变化情况及其主要影响因素。结果表明,溶解氧浓度及饱和率存在明显的季节和年际波动。其中:溶解氧浓度一般是在春季升至全年最高,夏季末降低,并在秋冬季维持低位;溶解氧饱和率则是夏秋季节最高,冬季最低。溶解氧浓度的季节变化与水温显著负相关,而溶解氧饱和率的季节变化和水温、pH显著正相关;溶解氧浓度及饱和率的年际变化与水质主要指标均不存在显著相关关系。受高海拔低气压影响,虽然采取了大气压和温度补偿校准,但泸沽湖溶解氧浓度仍不易达到Ⅰ类水质标准限值(7.5 mg/L);而优良的水质加之茂盛的水生植被使得其溶解氧饱和率长期处于较高水平,可以达到Ⅰ类标准限值(90%)。因此,在自然环境特征类似于泸沽湖的水质优良高原湖泊,优先以饱和率作为溶解氧的评价指标更为合理。

Analysis of Temporal Variation of Dissolved Oxygen and Its Main Influencing Factors in the Lugu Lake from 2013 to 2020

Located at the junction of Sichuan and Yunnan,Lugu Lake is a typical plateau freshwater lake in China.Objectively evaluating the water quality of Lugu Lake is extremely important for its planning preservation and preservation effectiveness evaluation.Given dissolved oxygen is usually considered the only key indicator that determines the water quality type of Lugu Lake,this paper focused on the annual and seasonal changes in dissolved oxygen and their influencing factors based on a comprehensive analysis of the changes in the lake''s main water environment indicators for eight consecutive years from 2013 to 2020.The results showed that the concentration and saturation rate of dissolved oxygen had obvious annual and seasonal fluctuations.Dissolved oxygen concentration generally rose to the highest year-round in spring,decreased in late summer,and remained at a low level in autumn and winter.The saturation rate of dissolved oxygen was the highest in summer and autumn,and lowest in winter.The seasonal variation of dissolved oxygen concentration was significantly and negatively correlated with water temperature,while seasonal variation of dissolved oxygen saturation rate was significantly and positively correlated with water temperature and pH value.Annual changes in the concentration and saturation rate of dissolved oxygen were insignificantly correlated with the main indicators of water quality.Under the impacts of high altitude and low atmospheric pressure,it was still not easy for the dissolved oxygen concentration of Lugu Lake to reach the standard limit for Class I water quality of 7.5 mg/L,although atmospheric pressure and temperature-compensated calibration measures were adopted.And excellent water quality and lush aquatic vegetation made the saturation rate of dissolved oxygen remained at a high level for long,which could reach the Class I standard limit of 90%.Thus,in plateau lakes with excellent water quality whose natural environment features are similar to those of Lugu Lake,it is more reasonable to give priority to the saturation rate as the indicator for evaluating dissolved oxygen.