Seasonal chemical characteristics and formation of potential secondary aerosols of a remote area in South Korea using an oxidation flow reactor

Due to the complicated characteristics of secondary aerosols (SAs), their study requires research into their formation and oxidation processes under diverse atmospheric conditions and reactions. Moreover, the increasing atmospheric pollution in Korea has been attributed to factors such as long-range transport of pollutants from China and emissions from domestic sources like cities, power plants, and industrial complexes. In this study, an oxidation flow reactor (OFR) was utilized to assess the chemical characteristics of potential SAs in Korea's background atmosphere. Sampling was conducted from 2019 to 2021 on Baengnyeong Island (37.967° N, 124.630° E), located west of the Korean Peninsula and approximately 180 km from China's Shandong Peninsula. The OFR, coupled with a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and various gas monitors (SO 2 , NO, NO 2 , NO X , CO, NH 3 , and O 3 ), facilitated the analysis of the chemical composition of potential SAs. Additionally, to analyze long-range transport from Baengnyeong Island to Seoul, data on SAs and gaseous pollutants from the island were compared with those from Seoul. Results indicate that the potential SAs generated by the OFR were influenced by ozone (O 3 ) and relative humidity (RH) levels. The concentration of these potential SAs increased with aging time and varied depending on O 3 and RH levels. During spring, elevated PM 1 concentrations in Seoul were noted, driven by additional SAs from photochemical reactions in inland regions. In contrast, during winter, the formation of certain SAs was predominantly due to long-range transport or the accumulation of domestic pollutants in the atmosphere. • Ozone and relative humidity significantly influenced the formation of potential secondary aerosols in Baengnyeong Island. • Day and nighttime conditions in Baengnyeong Island showed no significant difference in SOA enhancement across all seasons. • In Seoul, potential SAs were influenced by additional chemical reactions during long-range transport in spring, contrasting with winter.