[Seasonal and Spatial Variation Characteristics of Surface Water Quality and Its Influencing Factors in Baiyangdian Lake].

Baiyangdian Lake is the major ecological function area of Xiongan New Area. To reveal the surface water quality and its changing trends, seasonal changing trends, spatial changing characteristics, and influencing factors of the important indicators of the surface water,statistical description,ion diagrams,factor analysis, and other methods were comprehensively used to systematically study the surface water quality of Baiyangdian Lake. The results showed that the surface water quality of Baiyangdian Lake was gradually improving,and the water quality was mainly Class IV by 2020. COD,permanganate index,total nitrogen, and total phosphorus were key indicators that affected the water quality of Baiyangdian Lake. The spatial and temporal variation characteristics of these four key indicators were analyzed. The study of spatial change characteristics revealed that the content of oxygen-consuming substances that were difficult to be oxidized in the surface water was high,and the substances carried by the river entering Baiyangdian Lake directly affected the water quality near the entrance of the lake. The time variation characteristics indicated that under the background of ecological water replenishment,the concentration level of pollutants in surface water had significantly decreased, and the water quality had been significantly improved. The hydrochemical type of the surface water was mainly HCO₃-Na type. TDS and the main ion concentrations were higher in the south and lower in the north. The constant ion components mainly originated from the weathering and dissolution of silicate rocks；the trace water chemical components were affected by natural and man-made factors. The natural source was rock weathering. The man-made factors included atmospheric deposition,agricultural and industrial sources,and the superimposed impact of organic pollution. The research results can provide scientific support for the protection and restoration of Baiyangdian Lake ecology.