New collaborative work by the McNeill, Thomson, and Geiger groups reports the synthesis and measurements of some climate-relevant physical properties of SOA particle constituents consisting of the isoprene oxidation products α-, δ-, and cis– and trans-β-IEPOX (isoprene epoxide), as well as syn– and anti-2-methyltetraol. Following viscosity measurements, we use octanol–water partition coefficients to quantify the relative hydrophobicity of the oxidation products while dynamic surface tension measurements indicate that aqueous solutions of α- and trans-β-IEPOX exhibit significant surface tension depression. We hypothesize that the surface activity of these compounds may enhance aerosol CCN activity, and that trans-β-IEPOX may be highly relevant for surface chemistry of aerosol particles relative to other IEPOX isomers.

Climate-relevant physical properties of molecular constituents for isoprene-derived secondary organic aerosol material
Upshur, M. A., Strick, B. F., McNeill, V. F., Thomson, R. J., and Geiger, F. M.:
Atmos. Chem. Phys., 14, 10731-10740