Exploring Volatility Properties of Discrete Secondary Organic Aerosol Constituents of α-Pinene and Polycyclic Aromatic Hydrocarbons

Limited experimental data are available on the volatility parameters of saturation vapor pressure, vaporization enthalpy, and melting temperature of secondary organic aerosol (SOA) constituents. In this study, we aimed to determine the volatility of individual components of typical biogenic and anthropogenic SOA. The volatility profiles of four synthesized and two commercial SOA constituents were generated using a thermal denuder coupled with a scanning particle sizer. For the volatility measurement, four constituents of α-pinene SOA were synthesized in the laboratory because of the lack of commercial reagents. For each of the SOA species, a volatility profile was measured by changing the thermal denuder temperature below its melting point measured using thermal gravimetric analysis and differential scanning calorimetry. Saturation pressure (Psat0) and vaporization enthalpy (ΔHv) at 25 °C of the SOA constituents were determined by applying the integrated volume method to the measured volatility profiles. The determined Psat0 values of 3-methylbutane-1,2,3-tricarboxylic acid (3-MBTCA), terpenylic acid, diaterpenylic acid acetate (DTAA), sodium-(1R,2R,3S,5R)-2-hydroxy-2,6,6-trimethylbicyclo[3.1.1]heptan-3-yl sulfate (Na-2-OH-2,6,6-TMBHS), 1,2,4,5-benzenetetracarboxylic acid (1,2,4,5-B4CA), and 1,2,4-benzenetricarboxylic acid (1,2,4-B3CA) were 3.4 ± 0.6 × 10-5, 1.7 ± 0.3 × 10-4, 1.8 ± 0.2 × 10-5, 3.4 ± 0.4 × 10-5, 7.7 ± 0.7 × 10-5, and 2.1 ± 0.3 × 10-6 Pa, respectively. The estimated values of ΔHv for 3-MBTCA, terpenylic acid, DTAA, Na-2-OH-2,6,6-TMBHS, 1,2,4,5-B4CA, and 1,2,4-B3CA were 128.4 ± 4.7, 88.4 ± 3.5 135.4 ± 3.7, 38.4 ± 1.7, 42.8 ± 2.1, and 108.1 ± 4.1 kJ mol-1, respectively. These data will improve the knowledge of the formation and fate of SOA.