Analysis Of Temporal And Spatial Characteristics Of Water Quality And The Impact Factors In Tetma Lake,China

The deterioration of water quality is an important research topic in the evolution of lake environment,which has been widely concerned by countries and academia in the world.In recent years,the problem of lake water pollution in arid areas has become increasingly serious,especially in the relatively independent inland humidity circulation system and the tail lakes affected by climate change and human activities.Environmental problems such as the disappearance of lakes in arid areas,vegetation cover retreat,desertification,salinization,biodiversity reduction,and frequent climate disasters have posed a serious threat to human survival and development in the basin.The water environment quality of the lake will affect the structure and function of its aquatic ecosystem,and ultimately affect the health of the aquatic ecosystem.Scientific understanding of the change characteristics of water quality is the key to solving the problem of aquatic ecological environment.In this study,the Tetma Lake Basin was selected as the research object,and sampling was carried out in Tetma Lake from November 2021 to June 2022.Based on the comprehensive investigation and water sample analysis of the Tetma Lake Basin,the single factor evaluation method and the Nemero pollution index method were used to comprehensively evaluate the water quality of Tetma Lake.The horizontal spatial distribution and overall temporal variation trend of water quality in Tetma Lake were analyzed to reveal the spatial and temporal distribution of water environment.Principal component analysis and correlation analysis were used to identify the main influencing factors,and the main pollution indicators COD and fluoride were analyzed.The main driving factors affecting the water quality change in the Tetma Lake Basin were proposed,and finally the countermeasures and suggestions for water environment protection were proposed based on the characteristics of water pollution.The main conclusions are as follows:（1）The results of single factor evaluation showed that the water quality of Tetma Lake in autumn was IV,and the main pollution index was fluoride.The water quality in winter is inferior to Class V,and the main pollution index is fluoride.The water quality in spring was inferior to Class V,and the main pollution indexes were TP,COD and fluoride.The water quality in summer was inferior to class V,and the main pollution indexes were COD,COD_Mnand fluoride.The water quality of the whole year was inferior to grade V,and the main pollution indexes were TP,COD and fluoride.The evaluation results of the improved Nemerow index method show that the water quality of Tetma Lake is in the order of autumn>winter>summer>spring.（2）The water quality of Lake Tetma is inferior to the Class V standard of surface water environmental quality,which is a serious pollution.The main indicators affecting the water quality category of Lake Tetma are fluoride and chemical oxygen demand;the water body of Tema Lake is alkaline and highly mineralized,belonging to brackish or saline water.Dissolved oxygen,ammonia nitrogen and BOD5 all meet the Class I standard of surface water environmental quality.TN and COD_Mn meet the Class III standard of surface water environmental quality.The concentration of total phosphorus is high in summer,exceeding the Class V standard of surface water environmental quality.COD meets the Class IV standard of surface water environmental quality.Fluoride exceeds the Class V standard of surface water environmental quality in four seasons.（3）The water quality in the northeastern part of Tetma Lake is better near the inlet of the Tarim River.The pollution in the central and southern parts of the Lake and some areas of the Lake Conak is more serious.Among them,fluoride pollution is the most serious,and most areas exceed the surface water environmental quality V standard.（4）Four main fluorescent components of DOM in the samples were identified by parallel factor analysis,which represented UV humic-like（fulvic acid）C1 component,protein-like（tryptophan）fluorescence peak C2 component,protein-like（tyrosine）C3 and C4 components.Three-dimensional fluorescence regional integration analysis showed that the main components of DOM in the water body of Tetma Lake Basin were tryptophan-like proteins and tyrosine-like proteins,accounting for 66.57%of the total,and there were few humic-like substances.The fluorescence characteristic parameters of the Tetma Lake Basin show that the DOM source in the Tetma Lake Basin is mainly endogenous input,the relative concentration of newly generated organic matter is high,and the degree of humification is low.The sources of protein-like substances are mainly microbial degradation of algae or aquatic plant residues,as well as the release of sediments.The accumulation of DOM in lakes will cause an increase in COD concentration.There is a strong positive correlation between fluoride and salinity,and it is speculated that the high concentration of fluoride is also the result of long-term accumulation of the lake.