Secondary aerosol formation drives atmospheric particulate matter pollution over megacities (Beijing and Seoul) in East Asia

Influence of Relative Humidity and Composition on PM2.5 Phases in Northeast Asia

“…As a part of the Fine Particle Research Initiative in East Asia considering National Differences (FRIEND) project, which was launched in 2020 to investigate the mechanisms and characteristics of aerosol pollution in Northeast Asia, ,− we investigated the physicochemical properties of PM 2.5 in four different sites in Northeast Asia: Beijing (40.25° N, 116.19° E), Seoul (37.61° N, 126.93° E), Seosan (36.77° N, 126.49° E), and Ulaanbaatar (47.91° N, 106.94° E) (Figure S1). The measurement sites in Beijing, Seoul, and Ulaanbaatar are in urban environments, − whereas the site in Seosan is in a rural area. , Concurrent field measurements were conducted in these four cities with daily collection of PM 2.5 samples covering three seasons (winter, summer, and spring) between 2020 and 2022 (Tables S1 and S2, Figure S2).…”