Study on the Temporal Characteristics of Air Quality in Chang-Zhu-Tan Urban Agglomeration

Based on the air quality index（AQI） and hourly monitoring data of conventional pollutants from May 2015 to July 2021,the air quality index evaluation method was used to study the temporal succession characteristics of air quality in Changsha, Zhuzhou and Xiangtan urban agglomeration from the perspectives of different time scales, air quality grades and pollutant concentration changes. The results showed that the daily variation of AQI in Changsha, Zhuzhou and Xiangtan presented the characteristics of "double peak"; The value of AQI in spring showed an increasing trend from Monday to Wednesday, and reached the maximum value of one week on weekdays; The change of AQI in Changsha, Zhuzhou and Xiangtan urban agglomeration showed a trend of decreasing first and then increasing. The air quality of the three cities had an overall good trend, and the proportion of excellent air quality was increasing year by year. The change of air quality index and PM_2.5 was consistent with the change of concentration.