[Ozone Pollution Trend in the Pearl River Delta Region During 2006-2019]

Based on the monitoring data of the Guangdong-Hong Kong-Macao Pearl River Delta Regional (PRD) Air Quality Monitoring Network from 2006 to 2019, the ozone trend in RRD was analyzed using the Mann-Kendall test method, Sen's slope method, and the Pettitt change point test. The results show that:① the average ozone concentration in the PRD has increased significantly from 2006 to 2019 (P<0.05), with an average growth rate of 0.80 μg·(m³·a)^-1. After 2016, the rate of ozone increase has accelerated. ② The average annual ozone concentration in the central PRD increased significantly, while in the peripheral areas of the PRD, this is not obvious. Ozone increases significantly in summer but not in other seasons.③ From 2006 to 2019, the concentration of NO₂ in the central PRD decreased remarkably, so the titration effect weakened and resulted in an increase in the ozone concentration. The concentration of NO₂ in the marginal areas of the PRD has little change, so the ozone concentration in these areas has little change. ④ With the changes of VOCs and NO₂ concentrations, the chemical sensitivity of O₃ production in the PRD is changing. The VOC-limited regimes are continuously decreasing, and the mixed NO-VOC-limited regimes and NO-limited regimes are increasing. In order to deal with regional ozone pollution, the cooperative control of VOCs and NO needs to strengthen.