The volatility of pollen extracts and their main constituents in aerosolized form via the integrated volume method (IVM) and the volatility basis set (VBS)

Abstract

The volatility of organic aerosol in the atmosphere is an important quality that determines the aerosol/gas partitioning of compounds in the atmosphere and thus influences their ability to participate in gas-phase reactions in the atmosphere. In this research, the volatility of biological aerosols, specifically water-soluble pollen extracts and their chemical constituents, are studied for important thermodynamic properties such as saturation vapor concentration and latent heat of vaporization. The integrated volume method (IVM) was applied to characterize these properties for various free amino acids and saccharides in pollen, and the volatility basis set (VBS) approach was utilized to obtain a distribution of the mass fraction of pollen extracts with respect to saturation vapor concentration. Our results indicate that among seven compounds tested with the IVM, proline, γ-aminobutyric acid, and fructose had semivolatile saturation vapor concentrations of 17.5 ± 2.2, 14.7 ± 0.8, and 4.4 ± 0.5 μg m−3, respectively. Additionally, our VBS measurements indicate that aspen pollen extract contains a greater semivolatile mass fraction (up to 8.5% of total water-soluble mass) than lodgepole pine pollen (up to 2.2%), indicating that different pollen species may contribute to the total atmospheric semivolatile organic compound (SVOC) and low volatile organic compound (LVOC) budget differently. Depending on estimates of several factors, fluxes and concentrations of SVOCs and LVOCs from pollen could be comparable to other sources such as biomass burning and ambient urban emissions, though further research is needed to better constrain the contribution of pollen and other bioaerosols to organic compounds in the atmosphere.