Study On The Characteristics And Evaluation Of Water Pollution Changes In Lake Bosten

Bosten Lake is located in the southeast of Yanqi Basin in the arid-semi-arid region of Xinjiang,China,connected to the southern foot of the Tianshan Mountains,with the Kaidu River upstream and the Peacock River downstream,and is a typical throughput lake,and the largest inland freshwater lake in China.It has the functions of regulating the inflow of water resources from Kaidu River,irrigating the farmland in Peacock River basin,maintaining water for industry and urban and rural life,ecological protection of the basin and emergency water transfer to the middle and lower reaches of Tarim River,etc.It is also the main source of recharge of Tarim River,the main water resource in South Xinjiang,regulating microclimate and transferring water to the south,etc.It has an important role in the project.In this study,the water quality indicators of Lake Bosten were sampled and tested in June（abundant water period）,September（flat water period）and November（dry water period）,through the comparative analysis of TN,TP,NH₃-N,COD_Mn,DO,SS,turbidity and p H a total of eight indicators in the water quality concentration trends in the rich water period,flat water period and dry water period,water quality spatial distribution characteristics and pollution status and source analysis found that the lake water quality pollution situation is serious in the flat water period,followed by the rich water period,and the dry water period is less polluted.（1）The water quality trends in the water bodies of Lake Bosten were found that the water quality indicators NH₃-N and turbidity showed a decreasing trend in the abundant water period,flat water period and dry water period,DO and TN showed a decreasing trend in the abundant water period and flat water period,but an increasing trend in the dry water period,TP and p H showed a decreasing trend in the abundant water period and dry water period.DO and pH showed a decreasing trend in the abundant and dry periods,and an increasing trend in the dry period;COD_Mnand SS showed a decreasing trend in the flat and dry periods,and an increasing trend in the abundant period;the concentration changes in the small lake area were larger than those in the large lake area in different water periods.（2）The spatial variation characteristics of water quality in Lake Bosten show that the water quality indexes DO,TN,NH₃-N,COD_Mnand SS have obvious spatial variability in different water periods,among which DO shows a gradual decrease from the southwest to the north shore of the lake and from the center to the east and west shores of the lake during the abundant water period and the dry water period,respectively（12-8mg/L）,while the flat water period shows a gradual increase from the west to the east shore of the lake（4.9-7.1mg/L）.TP,TN and turbidity showed similar spatial variability during the abundant water period,with the center of the lake as the midpoint gradually increasing toward the east and west shores of the lake（0.04-0.18mg/L,0.59-2.81mg/L）,while during the flat water period,they showed a decreasing trend from the west to the east shore of the lake together with SS（0.18-0.09mg/L,4.6-0.93mg/L,84-5.48mg/L）,p H values ranged from 7.33-7.74 during the abundant and flat water periods and up to 8.52 during the dry water period,and the lake water quality was more than slightly alkaline.（3）The results of principal component analysis showed that the water quality indicators COD_Mn,NH₃-N,SS,TN and turbidity contributed the largest load matrix in different water periods,with COD_Mn（0.86）,NH₃-N（0.85）,TN（0.81）,turbidity（0.71）and TP（0.65）contributing the most,followed by DO（-0.88）and p H（-0.58）,and finally is SS（0.07）,and the water quality of the lake is polluted in the order of small lake>south shore of the lake>west shore of the lake>north shore of the lake>center of the lake>east shore of the lake.（4）Water quality pollution evaluation and source analysis derived from the water quality of Lake Bosten water body pollution evaluation size in order for the south shore of the lake（1.50）,small lake area（1.49）,the west shore of the lake（1.42）,the east shore of the lake（1.31）,the north shore of the lake（1.30）,the center of the lake（1.18）,the lake water quality are light pollution of three types of water quality;water quality change trend comprehensive index evaluation WQTI shows that DO,TP,NH₃-N,COD_Mn,turbidity,SS and p H integrated index decrease proportion is greater than the proportion of increase,water quality tend to improve;pollution source analysis PCA and cluster analysis results show that the largest contribution of the flat water period,followed by the abundant water period,and finally the dry water period,TP,TN,NH₃-N,COD_Mnand turbidity belong to one category,DO and p H belong to one category,SS The lake is mainly polluted by point sources of domestic sewage.Although the water quality of the lake has improved,it is still subject to point source pollution from domestic and industrial effluent.