[Water Quality Evolution in the Guishui River Section of Guanting Reservoir in Recent Years].

Based on manual and automatic monitoring data of water quality at the Gujiaying section of the upstream of Guanting Reservoir （Guishui River section） from 2017 to 2023， this study comprehensive applied the Mann Kendall statistical test， STL trend decomposition， grey prediction model， and emission inventory statistics and other analysis methods， combined with literature research， and systematically revealed the water quality evolutions， influencing factors， and the impact of epidemic control and rainstorm events on water quality in the upper reaches of Guanting Reservoir. The results showed that： ① The period from 2017 to 2023 was the best time for the upstream inflow water quality of Guanting Reservoir in 50 years. Since Guanting Reservoir was restored as a backup water source in 2007， the inflow water quality was significantly improved， rising from Class Ⅳ to Class Ⅲ， reaching Class II in some months.

[Temporal and Spatial Variations in Water Quality of Hanjiang River and Its Influencing Factors in Recent Years].

Hanjiang River is the main water source and influence area of the Middle Route of the South to North Water Transfer Project. In recent years, the water quality and ecological environment in the middle and lower reaches of the Hanjiang River has become seriously degraded and water blooms occur frequently. Scientific identification of the temporal and spatial variations in water environment quality (and the main driving factors) has become an important management requirement for optimizing the upstream water transfer project.

[Characteristics of Ozone Background Concentration in Beijing from 2004 to 2015].

Based on the hourly O monitoring data from 2004 to 2015 of Beijing, a comprehensive discussion on the characteristics of O concentration at a background station Dingling in Beijing was conducted. The results showed that the annual concentration of O1h was increasing with a growth rate of 4.40 μg·m while the annual concentration of O8h was decreasing with annual average rates of -1.