Characteristics of Ozone Pollution in Tai’an and Topographic Effects of Mount Tai

Abstract

Through the analyses of the observed concentrations of ozone (O3) in Tai’an from 2016 to 2021, the results show that O3 pollution was relatively serious, with the mean concentrations of the 90th percentile of daily maximum 8-h O3 (O3-8h-90per) above 180 μg/m3. O3 pollution in Tai’an mainly occurred from May to September, accounting for 69%~100% of the total O3 pollution days, of which the most serious pollution occurred in June. Combined with the analyses of temperature, humidity, and wind speeds, the probability of O3 exceedances in Tai’an increased significantly under the conditions with the temperatures higher than 30 °C, the relative humidity of 20%~40%, and the wind speeds of 1~3 m/s. The dominant wind directions on O3 pollution days in Tai’an were southerly winds, based on the analyses of wind directions and their clustering trajectories. Based on the results at three monitoring stations at different distances from Mount Tai from May to September in 2021, the average O3 concentrations at the Renkou School station near the mountain was about 13~15 μg/m3 higher than those at the other two stations (Dianli College and Shandong First Medical University) which are far away from the mountain, indicating that the Renkou School site was more affected by the obstruction of the mountain. In addition, the WRF-CMAQ model was used to simulate ten O3 pollution events in 2021, showing that the average O3 concentrations in Tai’an were reduced by 1.7~7.5 μg/m3 after changing the topographic height of Mount Tai.