Estimation of secondary organic aerosol formation parameters for the Volatility Basis Set combining thermodenuder, isothermal dilution and yield measurements

Abstract

Abstract. Secondary organic aerosol (SOA) is a major fraction of the total organic aerosol (OA) in the atmosphere. SOA is formed by the partitioning onto pre-existent particles of low vapor pressure products of the oxidation of volatile, intermediate volatility, and semivolatile organic compounds. Oxidation of the precursor molecules results in a myriad of organic products making the detailed analysis of smog chamber experiments difficult and the incorporation of the corresponding results into chemical transport models (CTMs) challenging. The volatility basis set (VBS) is a framework that has been designed to help bridge the gap between laboratory measurements and CTMs. The parametrization of SOA formation for the VBS has been traditionally based on fitting yield measurements of smog chamber experiments. To reduce the uncertainty of this approach we developed an algorithm to estimate the SOA product volatility distribution, effective vaporization enthalpy, and effective accommodation coefficient combining SOA yield measurements with thermograms (from thermodenuders) and areograms (from isothermal dilution chambers) from different experiments and laboratories. The algorithm is evaluated with “pseudo-data” produced from the simulation of the corresponding processes assuming SOA with known properties and introducing experimental error. One of the novel features of our approach is that the proposed algorithm estimates the uncertainty of the predicted yields for different atmospheric conditions (temperature, SOA concentration levels, etc.). The predicted yield uncertainty is significantly less than that of the estimated volatility distributions for all conditions tested.

Formation of secondary organic aerosol during the dark-ozonolysis of α-humulene

“…The SOA volatility distribution was estimated using the algorithm of Uruci et al . 31 This algorithm combines yield, TD, and isothermal dilution measurements, to estimate the volatility distribution of the SOA, its vaporization enthalpy, the accommodation coefficient, and their uncertainties. This algorithm also provides an uncertainty range of the estimated yields at different temperatures and SOA levels.…”