Abstract: We investigated secondary organic aerosol (SOA) from β-caryophyllene oxidation generated over 213-313 K from ozonolysis. Positive matrix factorization (PMF) was used to deconvolute the desorption data (thermograms) of SOA products detected by a chemical ionization mass spectrometer (FIGAERO-CIMS). A non-monotonic dependence of particle volatility (saturation concentration at 298 K, C_298K^*) on formation temperature (213-313 K) was observed, primarily due to temperature-dependent formation pathways of β-caryophyllene oxidation products. The PMF analysis grouped detected ions into 11 compound groups (factors) with characteristic volatility. These compound groups act as indicators for the underlying SOA formation mechanisms. Their different temperature response revealed that the relevant chemical pathways (e.g., autoxidation, oligomer formation, and isomer formation) had distinct optimal temperatures between 213–313 K, significantly beyond the effect of temperature-dependent partitioning. Furthermore, PMF-resolved volatility groups were compared with volatility basis set (VBS) distributions based on different vapor pressure estimation methods. The variation of the volatilities predicted by different methods is affected by highly oxidation oxygenated molecules, isomers and thermal decomposition of oligomers with long carbon chains. This work distinguishes multiple isomers and identifies compound groups of varying volatility, providing new insights into the temperature-dependent formation mechanisms of β-caryophyllene-derived SOA particles.
TechnicalRemarks: Data related to: “Volatility of secondary organic aerosol from β-caryophyllene ozonolysis between 213-313 K” by Gao et al., Environ. Sci. & Technol., 2023.
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Excel file “Data_manuscript_Gao_EST_2023” includes:
Figure 1. Mass spectra and sum thermogram of SOA at 213 K - 313 K.
Notes: Mass spectra are reprinted with permission under the terms of the Creative Commons Attribution 4.0 License1. Copyright 2022 L. Gao. (KITopen-ID: 1000144632).
Figure 2. Fixed-peak gaussian fit for C15H24O3I- at the 213 K, 243 K, 273 K, and 298 K.
Notes: The 6-peak gaussian fitting is done using a home made code in MATLAB2018b. The relative fitting error is 1.4%, 2.0%, 1.4%, and 20.1% for SOA213K, SOA243K, SOA273K and SOA298K, respectively.
Figure 3. Factor contribution to β-caryophyllene SOA at five formation temperatures.
Figure 4. One-dimensional volatility basis set (1D-VBS) based on the volatility calibration and formula method for SOA formed at temperatures (from top to bottom) of 213 K - 313 K.
Notes: The estimation of volatility (log10C* at 298 K, log10Csat at 298 K) can be found in the Experimental Section in the manuscript.
Table 1. Summary on the average molecule formula, molecular weight (MW), O:C, OSC, and Tmax of 12 PMF factors.
Notes: The error of the 12-factor PMF solution can be found in Figure S7 in the supplement.
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Excel file “Data_supplement_Gao_EST_2023” includes:
Figure S1. Correlation between temperatures of maximum desorption (Tmax) and the known saturation vapor pressures (VP) of seven carboxylic acids.
Figure S2. Van-Krevelen diagram for β-caryophyllene-dereived particles during the SOA generation period at all temperatures from HR-AMS measurements.
Figure S3. Comparison of O:C ratio, H:C ratio, and OSC of SOA particles formed at 213 K - 313 K between the measurements from HR-AMS and FIGAERO-CIMS.
Figure S4. The contribution of C15H24O3 in both gas and particle phases for all SOA formation temperatures.
Figure S5. A 12-factor PMF solution for β-caryophyllene SOA particles at five temperatures.
Figure S6. Q/Qexp values for the varying number of factors in PMF solutions, and varying fpeak in a 12-factor PMF solution.
Figure S7. Residual, relative residual, and Q/Qexp change for all samples when varying the number of factors and fpeak values.
Figure S8. One-dimension volatility basis set (1D-VBS) based on the formula method for monomers, dimers, and trimers in the SOA particles formed at 213 K – 313 K.
Table S1. Compilation of experimental conditions, concentration of β-caryophyllene and O3.
Note: This table is reprinted with permission under the terms of the Creative Commons Attribution 4.0 CC BY License1. Copyright 2022 L. Gao. (KITopen-ID: 1000144632).
Table S2. Compounds used for the volatility calibration and saturation vapor pressures from literature.
Table S3. Compilation of O:C ratios, H:C ratios, OSC, derived from FIGAERO-CIMS measurements and the Tmax of sum thermograms.
