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

Abstract

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 (P sat 0) and vaporization enthalpy (ΔH v) at 25 °C of the SOA constituents were determined by applying the integrated volume method to the measured volatility profiles. The determined P sat 0 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 ΔH v 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.

Comparison of saturation vapor pressures of <i>α</i>-pinene + O<sub>3</sub> oxidation products derived from COSMO-RS computations and thermal desorption experiments

“…The FIGAERO-CIMS-derived saturation vapor pres- 2020) and Kostenidou et al (2018), respectively. The difference of 3 orders of magnitude in experimentally determined saturation vapor pressures of MBTCA (Lienhard et al, 2015;Babar et al, 2020;Kostenidou et al, 2018) demonstrates how different experimental methods give widely different values. Kurtén et al (2016) computed saturation vapor pressures of isomers that are potential products of gas-phase autoxidation, rather than products of condensed-phase reactions.…”

“…In addition, an elemental composition corresponding to pinic acid (C 9 H 14 O 4 ) was seen in our experiments, but we were not able to determine T max values from the thermogram. Previously, Kurtén et al (2016) (Bilde and Pandis, 2001;Lienhard et al, 2015;Babar et al, 2020) are given for the specific isomer, while COSMOtherm15 values (Kurtén et al, 2016) are for various other isomers.…”

Comparison of computational and experimental saturation vapor pressures of α-pinene + O<sub>3</sub> oxidation products

“…Recently, Thomsen et al (2021) identified multiple carboxylic acids in SOA formed in α-pinene ozonolysis experiments using an ultra-high performance liquid chromatograph (UHPLC). Out of the compounds included in Thomsen et al (2021) (Bilde and Pandis, 2001;Lienhard et al, 2015;Babar et al, 2020) are given for the specific isomer, while COSMOtherm15 values (Kurtén et al, 2016) are for various other isomers. Babar et al (2020) and Kostenidou et al (2018), respectively.…”

“…Out of the compounds included in Thomsen et al (2021) (Bilde and Pandis, 2001;Lienhard et al, 2015;Babar et al, 2020) are given for the specific isomer, while COSMOtherm15 values (Kurtén et al, 2016) are for various other isomers. Babar et al (2020) and Kostenidou et al (2018), respectively. The 3 orders of magnitude difference in experimentally determined saturation vapor pressures of MBTCA (Lienhard et al, 2015;Babar et al, 2020;Kostenidou et al, 2018) demonstrates how different experimental methods give widely different values.…”

“…Babar et al (2020) and Kostenidou et al (2018), respectively. The 3 orders of magnitude difference in experimentally determined saturation vapor pressures of MBTCA (Lienhard et al, 2015;Babar et al, 2020;Kostenidou et al, 2018) demonstrates how different experimental methods give widely different values. Kurtén et al (2016) computed saturation vapor pressures of isomers that are potential products of gas-phase autoxidation, rather than products of condensed-phase reactions.…”