Preliminary Study on the Spatial and Temporal Characteristics and Influencing Factors of Dissolved Oxygen Content in Beihai Lake,Tengchong
Dissolved oxygen(DO)is an important index to evaluate water environment quality and ecosystem health,and is often considered as the only criterion to measure water quality in plateau lakes.DO is influenced by reoxygenation and oxygen consumption processes,and environmental and biological factors influence DO dynam-ics by influencing these two processes.Finding out these influencing factors can provide a reference for the man-agement of the plateau river,lake and reservoir.In the study,the main factors affecting the DO of Beihai Lake in Tengchong,Yunnan Province were investigated and analyzed by measuring the seasonal dynamics of the DO at the whole lake and the provincial control point in autumn.The results show that ① The site of DO in Tengchong Beihai Lake above the level of class Ⅲ accounts for 91％of the total study sites,indicating that the water quality of Tengchong Beihai Lake is excellent.② The DO of Beihai Lake in Tengchong has a significant spatio-temporal variation,and the DO in the southern area is significantly higher than in the northern area;The provincial control point DO is higher in winter and spring,but lowest in summer,which accords with the general law of DO varia-tion of surface water.③ In autumn,there was a significant positive correlation between DO and pH and water temperature in Tengchong Beihai Lake,reflecting a significant biological effect;On the annual scale,the provin-cial control point DO has a significant positive correlation with PH,but a significant negative correlation with wa-ter temperature.④ The DO which area distributed submerged plants is significantly higher than that without sub-merged plants,and the DO which area distributed Brasenia schreberi is significantly lower than that with sub-merged plants,indicating that submerged plants play an important role in maintaining the high DO of Beihai Lake,while high dense Brasenia schreberi will reduce the reoxygenation capacity of the water.The distribution of grass raft has little effect on DO of Tengchong Beihai Lake.The results of this study will provide a reference for water environment assessment and effective management of plateau lakes.
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