[Pollution Characteristic and Control Factor Analysis of Atmospheric Ozone During Summer Typical Periods in Linyi,...

In June 2020, an observation experiment of O₃ and its precursors was carried out in Linyi City, Shandong Province. Based on the observation data and MCM photochemical model simulation, the formation mechanism and control mechanism of an ozone pollution case in mid-June were analyzed. The study found that, despite the high precipitation during the observation period, ozone concentrations rapidly accumulated and exceeded the limits once the weather cleared, with the 1-h average and 8-h φ (O₃) exceeding the national ambient air quality standards on 10 days (32% in frequency)and 14 days (45%), respectively. The diurnal variation in O₃ concentration was unimodal and accompanied by the afternoon peak at 16:00. MCM simulation results showed that the daily net reaction rate of O₃ was 20×10^-9 h^-1, and HO₂·+NO and RO₂·(except CH₃O₂·)+NO contributed 49.0%-51.1% and 37.3%-40.2% of O₃ generation, respectively. The contribution of the·OH+NO₂ reaction to the total consumption of O₃ was 35.1%-57.4%. The results of VOCs reactivity, relative incremental reactivity (RIR), and the EKMA curve method showed that the generation of O₃ was more sensitive to alkenes (mainly trans-2-pentene and trans-2-butene)and aromatics (mainly m/p-xylene and toluene)but was negatively sensitive to NO. In other words, the reduction in VOCs concentration would lead to the decrease in O₃ concentration, whereas the reduction in NO concentration would lead to the increase in O₃ concentration. PMF source analysis results showed that volatile sources used by solvents and vehicle exhaust emissions contributed significantly to the above key precursor VOC species. Considering the titration effect of NO from vehicle exhaust emissions on ozone, controlling the use of volatile sources of solvents can realize the control of O₃ pollution accurately and efficiently.