Abstract:

To study the characteristics of heavy-air pollution process of Jinan in winter, a typical heavy-air pollution process that occurred during December 8 to 13 in 2020 was taken as an example to comprehensively analyze the characteristics and causes from the perspectives of pollution process, meteorological conditions, and chemical composition of fine particles. The results were shown as follows: During the heavy pollution process, the primary pollutant was PM_2.5, with an average mass concentration of 137 μg/m³. The pollution peak was reached at 21:00 on the December 11, and the mass concentration of PM_2.5 was as high as 235 μg/m³. During heavy pollution, the high-altitude circulation was relatively straight; the low 850 hPa was affected by the southwest airflow, which was conducive to the formation of temperature inversion stratification; the ground pressure field was controlled, and advection and radiation fogs occurred alternately. The static and stable meteorological conditions worsened the accumulation of PM_2.5 concentration and the secondary conversion of particulate matter under high-humidity conditions. During the observation period, the mass concentration of SNA was 85.4 μg/m³, accounting for 52.0% of the PM_2.5 concentration. The average values of R_S and R_N were 0.44 and 0.33 respectively, the secondary oxidation of SO₂ and NO₂ in the atmosphere was relatively high. R_S was higher than R_N, indicating that the secondary conversion efficiency of $SO^{2-}_{4}$ is higher than $NO^{-}_{3}$. The average value of $\rho_{NO^{-}_{3}}$ / $\rho_{SO^{2-}_{4}}$ was 2.1, indicating that the contribution of mobile sources to PM_2.5 pollution is dominant. The average ratio of OC/EC was 6.5, which indicated that there was SOC pollution in the atmosphere of Jinan during the heavy pollution period. Using the ρ_OC/ρ_EC minimum ratio method, the mass concentrations of POC and SOC during the heavy pollution period were estimated to be 11.9 μg/m³ and 4.3 μg/m³, respectively. The mass concentration of POC was higher than SOC, and it indicated that the primary combustion source has a greater contribution to the pollution process.

Key words: :heavy pollution, PM_2.5, meteorological factors, water-soluble ions, carbonaceous species