Physicochemical and isotopic properties of ambient aerosols and precipitation particles during winter in Seoul, South Korea.

The aim of this study was to characterize the physicochemical properties and microbial communities of particulate matter (PM) in Seoul, Korea. We collected long-term (2017-2019) precipitation samples and PM and PM monitoring data to determine the impact of soluble and insoluble chemical species on the soil surface. Ambient PM concentrations were higher than PM concentrations during the monitoring period, but both decreased during rainfall due to the washing effect of precipitation. PM particles had a "fluffy" shape and contained sulfur (0.2%), but suspended particles (SPs) contained many carbon particles (approximately 60%). Spherical particles containing metal oxides, Fe and Al, might be originated from coal combustion, wild fires, and metal-refining processes under high-temperature conditions. Dissolved ions in precipitation included those eluted from salts and coal combustion based on the correlation coefficients of Na and Cl (R = 0.953) and F and NO (R = 0.706). The δN-NO and δS-SO of precipitation were enriched as the atmospheric temperature decreased from 9.8 to -1.6°C, implying the influence of domestic coal combustion. Backward trajectories showed that, in winter, air parcels passed through industrialized cities from China to South Korea. The microbial communities associated with PM were strongly influenced by atmospheric conditions. Proteobacteria (range from 4.6 to 76.7%) and Firmicutes (range from 6.0 to 91.4%) were the most dominant phyla and were significantly affected by changes in the PM environment. The results indicate that the acidity of precipitation and the composition of aerosols were affected by fossil fuel combustion and mineral dust, and that atmospheric conditions may change as PM concentrations increase.