Climate-relevant physical properties of molecular constituents for isoprene-derived secondary organic aerosol material

Secondary organic aerosol (SOA) particles, formed from gas-phase biogenic volatile organic compounds (BVOCs), contribute large uncertainties to the radiative forcing that is associated with aerosols in the climate system. Reactive uptake of surface-active organic oxidation products of BVOCs at the gas-aerosol interface can potentially decrease the overall aerosol surface tension and therefore influence their propensity to act as cloud condensation nuclei (CCN). Here, we synthesize and measure some climate-relevant physical properties of SOA particle constituents consisting of the isoprene oxidation products ±-and-2-IEPOX (isoprene epoxide), as well as-and-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 ±-and2-IEPOX exhibit significant surface tension depression. We hypothesize that the surface activity of these compounds may enhance aerosol CCN activity, and that 2-IEPOX may be highly relevant for surface chemistry of aerosol particles relative to other IEPOX isomers.