Chemical characterization and source identification of PM2.5 at Baengnyeongdo Island, South korea: Three-year dynamics (2019–2021)

Abstract

Fine particulate matter (PM2.5) remains a critical air pollutant with substantial public health risks, particularly in East Asia, where domestic emissions and transboundary transport contribute to elevated concentrations. This study examined the annual and seasonal variations of PM2.5 and its chemical constituents at Baengnyeongdo Island, South Korea, from 2019 to 2021. The constituents analyzed included carbonaceous components (organic carbon [OC] and elemental carbon [EC]), major inorganic ions (sulfate [SO42−] and nitrate [NO3−]), crustal elements (e.g., silicon [Si], calcium [Ca], iron [Fe], titanium [Ti]), and various other metallic species. The study also sought to identify potential sources of PM2.5, with particular emphasis on transboundary influences. Results showed a significant increase in PM2.5 levels in 2021 (spring mean: 32.657 µgm−3), attributed to the resumption of industrial activities following the COVID-19 lockdowns, specific meteorological conditions, such as higher spring relative humidity (74.91%) and increased aerosol water content (32.16 µgm−3), and significant transboundary pollution, particularly from China. Seasonal analysis indicated that OC, EC, NO3-, and crustal elements (Si, Ca, Fe, Ti) were the dominant contributors. For example, OC and EC peaked in spring and winter, which was associated with biomass burning, heating, and industrial emissions, which were enhanced by low winter temperatures. NO3− also exhibited significant winter peaks (5.921 µgm−3 in 2021), driven by conditions favoring NH4NO3 formation, while SO42− levels, highest in 2019 (4.357 µgm−3), displayed a more moderate trend. Meteorological parameters, including aerosol water content, relative humidity, temperature, and wind patterns, play a major role in PM2.5 formation, accumulation, and dispersion. Back-trajectory modeling consistently confirmed air mass transport from the heavily industrialized regions of China, Mongolia, and Russia during high-pollution episodes across all seasons. These findings underscore the complex interplay between local emissions, transboundary transport, and meteorological factors, highlighting the urgent need for coordinated international air quality management policies.