[Analysis of Influencing Factors of Ozone Pollution Difference Between Chengdu and Chongqing in August 2022]

In August 2022, Chengdu and Chongqing showed significant differences in ozone (O₃) pollution. Chengdu had O₃ pollution days for 20 days, whereas Chongqing had no O₃ pollution days. In this study, we analyzed the influencing factors of this difference from the emission level of precursors and meteorological conditions. The results showed that:① the total mixing ratio of 52 VOCs (volatile organic compounds) (including 26 alkanes, 16 aromatics, and 10 alkenes) in Chengdu (18.8×10^-9) was 2.8 times that of Chongqing (6.6×10^-9), and the total O₃ formation potential (OFP) (51.2×10^-9) was 2.0 times that of Chongqing (25.0×10^-9). The·OH radical loss rate (L_·OH) (3.9 s^-1) was 1.7 times that of Chongqing (2.3 s^-1). The top three OFP in Chengdu were ethylene, m/p-xylene, and isoprene, and those in Chongqing were isoprene, ethylene, and propylene. The contribution rate of alkenes to O₃ in Chongqing was 60.7%, whereas the OFP of alkenes and aromatics in Chengdu were 1.6 times and 2.9 times that in Chongqing. In conclusion, the total mixing ratio of VOCs, atmospheric photochemical activity, and O₃ formation potential of Chengdu were higher than those of Chongqing. ② Isoprene was ranked first place in L_·OH in both Chengdu and Chongqing, indicating that the contribution of biogenic sources to O₃ pollution in August was significant. However, the biogenic source emission activity was in response to temperature. From August 14 to 24, the high temperature in Chongqing (38.3℃) decreased biogenic source emission activity, whereas the temperature in Chengdu (34.9℃) increased the biogenic sources emission activity. ③ The horizontal and vertical atmospheric diffusion conditions of Chongqing were better than those of Chengdu, and Chengdu was affected by regional pollution transmission.