Technical Description


Instrumentation


Research Interests

HEC: Yield of Secondary Organic Aerosol

Multiple studies indicate that state-of-the-art chemistry and transport models, which rely on laboratory parameterizations of SOA yield, under-predict the measured SOA mass by a factor of 10-100. In an effort to reconcile these differences and to provide yield data for atmospherically relevant amounts of reacted hydrocarbon, the yield of secondary organic aerosol (SOA) mass was measured for the dark ozonolysis of 0.3 - 22.8 ppbv of reacted α-pinene. For mass loadings of 2.0 to 40 μg m^-3, the SOA mass yields are 1.8 to 2 times larger than batch-mode results reported in literature. For the lowest loadings studied (0.15 - 2 μg m^-3), we observe a steep, step-like increase in the SOA mass yields with loading and yields appear to be nearly stoichiometric (ie., nearly independent of loading) over this range. Furthermore, we observe significant SOA formation for reacted α-pinene concentrations as low as 0.3 ppbv while literature data suggest that no SOA formation will occur for reacted α-pinene concentrations below 1 ppbv. As a result, for loadings below 2 μg m^-3, our yields are offset from the literature data by approximately +0.07. Our new observations of higher yields at low mass loadings are potentially important for reconciling the differences between the predictions of chemical transport models and recent ambient observations.

This figure shows the comparison of particle SOA mass yield obtained in this work to those of other studies for the dark ozonlysis of α-pinene. Data shown in Panels A1 and A2 are as reported by the original researchers, with the exception of the data of Gao et al.(2004), which are adjusted by us to ρ1.0, to facilitate the comparison with other studies all reported for this density. The studies were conducted at different temperatures, which affects SOA particulate yield. Therefore, yield data shown in panels B1 and B2 are adjusted, by us to 298 K, using a temperature correction of 1.6% per K, as recommended by Pathak et al. (2007a).