Transmission pathways and potential source regions for atmospheric fine particulate matter and ozone in Urumqi

To understand the transmission paths and potential source areas of fine particulate matter (PM_2.5) and ozone (O₃) in Urumqi, using the monitoring data from 2020 to 2022, the pollution characteristics and the transmission paths of PM_2.5 and O₃ were studied. Based on the MeteoInfo software, the potential source areas and concentration contributions via the weighted potential source contribution function (WPSCF) and the weighted concentration weighted trajectory (WCWT) were analyzed. Besides, trajectory distribution at different starting heights were compared. The results of the backward trajectory (500 m) showed that the PM_2.5 and O₃ clustering trajectories were mainly derived from the northwest and passed through Yining/Ili and Tacheng. The air flow proportion of PM_2.5 pollution was 44.83 % in winter. With the highest pollution concentration (119.2 µg/m³), the pollution airflow proportion of O₃ was 30.52 % in summer. According to an analysis of the pressure profile, the atmospheric pressure was below 850 hPa in winter, indicating that the near-surface air mass had a substantial impact on PM_2.5 concentrations, whereas in summer the pressure for O₃ rose above 750 hPa, leading to higher pollutant concentrations. The WPSCF/WCWT results of PM_2.5 demonstrated that the largest potential areas were identified in winter and were mainly distributed in Bozhou, Kuitun, and Shihezi (west of Urumqi, cultivated land/grassland), while the largest potential areas of O₃ were distributed in Changji (east of Urumqi, barren land) and Turpan (southeast of Urumqi, grassland) in summer. The study indicates that the government should implement stricter measures to control regional transmission and air pollution.