2015—2019洱海COD变化特征及影响因素研究

Research on the Variation Characteristics and Influencing Factors of COD in Erhai Lake in 2015—2019

通过开展洱海及主要入湖河流沟渠水质监测并应用Mann-Kendall趋势检验法、Morlet小波等方法分析洱海湖区COD变化特征。结果发现,洱海湖区的COD历史趋势具有较为明显的年际和年内变化特征,洱海湖区的COD在近年来由下降趋势转变为上升趋势,突变发生在2017—2018年。在此期间入湖COD负荷、气象条件均未发生突变,洱海湖区COD与入湖COD负荷相关性逐渐降低,与叶绿素和浮游植物相关性升高,反映出洱海COD趋于受内源影响。

The concentration of organic pollutants,represented by COD and permanganate index,has become a major factor affecting the water quality category of Erhai Lake.In this study,the characteristics of COD changes in Erhai Lake and the main rivers and ditches entering the lake were investigated by monitoring the water quality.The Mann-Kendall trend test and Morlet wavelet analysis methods were applied.The results indicated that the historical trend of COD in Erhai Lake had much obvious variation characteristics between years or months within a year,and the COD in Erhai Lake has changed from a decreasing trend to an increasing trend in recent years,with the abrupt change occurring between 2017 and 2018,during which no abrupt changes had occurred in the inflow COD load and meteorological conditions,while the correlation between COD and inflow COD load in Erhai Lake gradually decreased,and correlation with chlorophyll and phytoplankton increased,reflecting that COD in Erhai Lake tended to be impacted by endogenous phytoplankton sources.