[Analysis of PM_2.5 Transmission Characteristics in Main Cities of Jinzhong Basin in Winter]

In this study, we analyzed the hourly concentration data of PM₁₀ and PM_2.5 in major cities in Jinzhong basin from 2017 to 2019. The main distribution characteristics of aerosols in Jinzhong and Taiyuan were determined, and PM_2.5 hourly concentration data and HYSPLIT in Jinzhong basin in winter were discussed. The results showed that the overall level of particulate matter concentration in Taiyuan was higher than that in Jinzhong, and the monthly and seasonal variation characteristics were similar. All showed high concentrations in winter and low concentrations in summer, and the highest concentration value appeared in January. The aerosol pollution caused by the static and stable weather in Jinzhong was more common than that caused by the sand and dust weather in Taiyuan. The distribution of particulate matter showed the characteristics of more intermediate values in Jinzhong and more high and fewer low values in Taiyuan, and winter was the highest incidence season of PM_2.5 pollution in Jinzhong basin. PM_2.5 transmission passageways in the main cities of Jinzhong basin in winter could be divided into four categories:class 1 was transmitted along the transverse valley of Taihang Mountain, and class 2 was the southeast transmission channel. Class 1 and class 2 were the short-range transmission passageways; air masses carried more moisture, and PM_2.5 transmitted along such passageways allowed moisture to be absorbed more easily, increasing levels and aggravating local pollution. Class 3 was the northwest passageway, corresponding to the most serious pollution period of PM_2.5 in Jinzhong basin before the arrival of cold air, which also corresponded to the dust transmission passageway. Class 4 was the Fenwei Plain passageway, corresponding to high-concentration PM_2.5 pollution. Areas with dense pollution tracks (more than 100 pollution tracks) and areas with slow air flow movement (RTA pollution track end points greater than 50) easily became potential source areas of target cities (PSCF contribution greater than 0.7). The main potential source areas of PM_2.5 in winter in Jinzhong (PSCF contributing more than 0.7) were mainly distributed in Linfen, Jincheng, and other places in Shanxi province, as well as in the north of Henan province, the south of Hebei province, and central and south Shaanxi province. The distribution range of main potential source areas of PM_2.5 in Taiyuan in winter was wider than that in Jinzhong, including the south of Lvliang, Yangquan, Linfen, and Yuncheng and the south of Jinzhong in Shanxi, as well as most areas in southern Shaanxi, northern Henan province, and southern Hebei province. In addition, the PSCF distribution of high-value centers above 0.9 was wider than that of Jinzhong. When pollution occurs in cities that PSCF contributed more than 0.9, special attention should be paid to the influence of mutual transmission between them and cities in Jinzhong basin. Jinzhong and Taiyuan showed different distribution characteristics corresponding to the surface wind direction when light and higher pollution occur, when the wind direction near the ground in Jinzhong was E, the frequency of light and higher pollution was 8.1%; it was the highest in all wind directions. When the wind direction near the ground in Taiyuan was SSW, the frequency of light to higher polluted weather was the highest in all wind directions (5.1%). In the case of calm wind, the frequency of light to higher pollution in Taiyuan (3.4%) was higher than that in Jinzhong (0.5%).