To date, there are limited data on the thermal properties of secondary organic aerosol (SOA) components. In this study, we employed an experimental method to evaluate the physical properties of some atmospherically relevant compounds. We estimated the thermodynamic properties of SOA components, in particularly some carboxylic acids. The molar heat capacity, melting point and enthalpy, and vaporization enthalpy of the samples were determined via differential scanning calorimetry and thermogravimetric analysis, and their vaporization enthalpy (ΔH_vap) was estimated using Clausius–Clapeyron and Langmuir equations based on their thermogravimetric profiles. The thermodynamic properties of benzoic acid as a reference compound agree well with the reported values. The obtained specific heat capacities of benzoic acid, phthalic acid, pinic acid, ketopinic acid, cis-pinonic acid, terpenylic acid and diaterpenylic acid acetate (DTAA) are 118.1, 169.4, 189.9, 223.9, 246.1, 223.2, and 524.1 J mol⁻¹ K⁻¹, respectively. The ΔH_vap of benzoic acid, phthalic acid, ketopinic acid, DTAA, and 3-methylbutane-1,2,3-tricarboxylic acid (3-MBTCA) are 93.2 ± 0.4, 131.6, 113.8, and 124.4 kJ mol⁻¹, respectively. The melting and vaporization enthalpies of the SOA components range from 7.3 to 29.7 kJ mol⁻¹.

Fine particulate matter (PM_2.5) 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 PM_2.5 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 PM_2.5, with particular emphasis on transboundary influences. Results showed a significant increase in PM_2.5 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 PM_2.5 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.