[Analysis of Ozone Pollution Characteristics and Transmission Pathways in the Main Urban Area of Urumqi]

Global climate change is becoming increasingly crucial. With the continuous strengthening of environmental supervision and governance in China, the haze （O₃） weather mainly caused by PM_2.5 pollution has gradually improved, while the emissions of invisible ozone pollutants have been increasing annually. In particular, the problem of near-ground ozone pollution is more crucial, which poses a severe threat to urban production, life, and health of people. To gain a deeper understanding of the pollution characteristics of ozone, this study was conducted based on ozone monitoring, ground meteorological, and global data assimilation system （GDAS） meteorological data from January 2020 to February 2023 in Tianshan District, Urumqi City, to explore the characteristics of ozone mass concentration changes and potential source areas in Urumqi City at different time scales using the cluster analysis of the backward trajectory model （HYSPLIT） and trajectory （Tianshan District） and the concentration weight trajectory analyses （CWT）. The results showed that： ① The maximum 8-hour O₃ （O_3-8h） mass concentration in Tianshan District of Urumqi City had been increasing yearly from 2020 to 2022 and had obvious seasonal variation characteristics, with summer （110.33 μg·m^-3） > spring （87.67 μg·m^-3） > autumn （64.33 μg·m^-3） > winter （39.67 μg·m^-3）. ② The temperature, relative humidity, and air pressure of each season had a significant impact on O_3-8h mass concentration, with correlation coefficients r of 0.871,-0.752, and 0.644 （P < 0.01）, respectively. The annual wind speed variation was relatively low, which was a secondary meteorological factor and had no significant impact on ozone mass concentration. ③ The HYSPLIT clustering analysis results showed that overseas long-distance transportation had less impact on the O_3-8h mass concentration in Tianshan District, Urumqi City. The CWT results indicated that ozone pollution sources were mainly concentrated in the northern area of Urumqi in Xinjiang and the high-value areas in summer [O_3-8h mass concentration > 70 μg·m^-3] mainly appeared in areas with higher temperatures in Urumqi, Changji, Altay, and Tacheng. ④ Especially in autumn, the pollutants emitted by local anthropogenic activities had a great influence. To summarize, spatiotemporal concentration changes were observed in ozone pollution in Urumqi and the prevention and control of urban ozone pollution in Urumqi requires strengthening the emission of ozone precursors while considering implementing coordinated emission reduction measures for surrounding areas.