Constraining uncertainties in particle wall-deposition correction during SOA formation in chamber experiments.

The effect of vapor wall-deposition on secondary organic aerosol (SOA) formation has gained significant attention; however, uncertainties in experimentally derived SOA mass yields due to uncertainties in particle wall-deposition remain. Different approaches have been used to correct for particle wall-deposition in SOA-formation studies, each having its own set of assumptions in determining the particle wall-loss rate. In volatile and intermediate-volatility organic compound systems in which SOA formation is governed by kinetically limited growth, the effect of vapor wall-deposition on SOA mass yields can be constrained by using high surface area concentrations of seed aerosol to promote the condensation of SOA-forming vapors onto seed aerosol instead of the chamber walls. However, under such high seed aerosol levels, the presence of significant coagulation may complicate the particle wall-deposition correction. Here, we present a model framework that accounts for coagulation in chamber studies in which high seed aerosol surface area concentrations are used. For the α-pinene ozonolysis system, we find that, after accounting for coagulation, SOA mass yields remain approximately constant when large seed aerosol surface area concentrations (≥ 8000 μm² cm^-3) are used, consistent with our prior study (Nah et al., 2016) that α-pinene ozonolysis SOA formation is governed by quasi-equilibrium growth. In addition, we systematically assess the uncertainties in the calculated SOA mass concentrations and yields between four different particle wall-loss correction methods over the series of α-pinene ozonolysis experiments. At low seed aerosol surface area concentrations (< 3000 μm² cm^-3), the SOA mass yields at peak SOA growth obtained from the particle wall-loss correction methods agree within 14%. However, at high seed aerosol surface area concentrations (≥ 8000 3000 μm² cm^-3), the SOA mass yields at peak SOA growth obtained from different particle wall-loss correction methods can differ by as much as 58%. These differences arise from assumptions made in the particle wall-loss correction regarding the first-order particle wall-loss rate. This study highlights the importance of accounting for particle wall-deposition accurately during SOA-formation chamber experiments and assessing the uncertainties associated with the application of the particle wall-deposition correction method when comparing and using SOA mass yields measured in different studies. [ABSTRACT FROM AUTHOR]