[Variation of O₃ Concentration in Different Regions of Beijing from 2006-2015]

O₃ continuous monitoring data for the Dingling, Guanyuan, Liulihe, and Qianmen sites from 2006-2015 were analyzed to investigate concentration levels, variation trends, temporal variations, and relationships with precursors and meteorological factors. The results showed that the ten year average concentrations of O₃ at the Dingling site were the highest at 65.2 μg·m^-3, followed by concentrations at Liulihe (53.4 μg·m^-3), Guanyuan (49.6 μg·m^-3) and Qianmen (40.4 μg·m^-3). The O₃ concentrations at Dingling showed a decreasing trend[0.5 μg·(m³·a)^-1], while O₃ concentrations at Guanyuan[0.9 μg·(m³·a)^-1], Liulihe[0.3 μg·(m³·a)^-1], and Qianmen[0.3 μg·(m³·a)^-1] showed an increasing trend. The highest monthly average concentrations appeared during June and August, and the highest frequency occurred in July (17 times) with average concentrations of 99.8 μg·m^-3. The lowest monthly average concentrations appeared during November and February, and the highest frequency occurred in January (14 times) with an average concentration of 16.6 μg·m^-3. Notably, the time for the peak concentrations of O₃ appeared earlier in the day in recent years. The peak concentrations of O₃ appeared at 15:00-16:00 during 2013-2015, which was 1-2 hours earlier than previous years. The heavy air pollution of O₃ occurred on 11 days at the Dingling site in 2015, which was ten days more than in 2013, indicating O₃ pollution in the downwind suburban regions of Beijing in summer became more and more serious. The concentrations of O₃ and NO₂ at Dingling showed a positive correlation, while the concentrations of O₃ and NO₂ at the other sites showed a negative correlation, indicating O₃ formation in Dingling was sensitive to NO₂ chemistry, while O₃ formation at the other sites was sensitive to VOC chemistry. The concentrations of O₃ showed a positive correlation with temperature and negative correlations with humidity and surface pressure. Temperature had the greatest influence on O₃ concentration, followed by surface pressure and humidity. For cases when daily maximum temperature exceeded 30℃ and relative humidity was between 30% and 70%, the probability of the O₃ daily maximum 8 h concentration exceeding 200 μg·m^-3 was high, indicating the air quality level reached levels for light pollution and moderate pollution.