Understanding the physicochemical characteristics of PM2.5 under meteorological influence: A study in South Chungcheong Province, South Korea (2021–2022)

Despite the implementation of various policies worldwide to reduce PM_2.5 concentrations, they have remained sufficiently high and cause serious environmental and health problems. Most studies and policies regarding PM_2.5 in South Korea have primarily focused on the Seoul Metropolitan Area, including Seoul, and there is a lack of research data necessary for implementing PM_2.5 management policies in South Chungcheong Province (SCP). In this study, we used data from the Air Quality Research Center in Seosan, SCP, to conduct a detailed analysis of PM_2.5, focusing on its chemical and physical properties as well as the influence of meteorological factors on PM_2.5 characteristics. The mean PM_2.5 concentrations were 16.7 ± 12.5 μg/m³ in the warm season and 31.1 ± 18.7 μg/m³ in the cold season, showing a twofold increase in the cold season. The ratio of NO₃⁻ in the chemical composition of PM_2.5 was higher in the cold season (19%) compared to the warm season (15%), while SO₄²⁻ was 1.75 times higher in the warm season. Using the atmospheric oxidant (Ox) and analyzing PM_2.5 concentrations under different photochemical conditions, we found that small particles dominated in the warm season, shifting towards smaller particle sizes in the size distribution with higher temperatures due to secondary particle production. In contrast, higher concentrations of PM_2.5 during the cold season were attributed to direct emissions and external influx. Our findings highlight the importance of managing small particles in summer and provide valuable data for South Chungcheong Province, aiding future policy development to reduce PM_2.5 levels.