AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Secondary Organic Aerosol Production from Pinanediol
PENGLIN YE, Neil Donahue, Carnegie Mellon University
Abstract Number: 661 Working Group: Aerosol Chemistry
Abstract We have investigated the production of secondary organic aerosol (SOA) from pinanediol (PD) a precursor chosen as a surrogate for first-generation oxidation products of monoterpenes. Monoterpenes have substantial emissions from vegitation, and when they are oxidized some products have very low vapor pressure and thus contribute to SOA formation. Experiments at the CLOUD facility at CERN are focusing on chemistry that can drive formation of new particles in the atmosphere (nucleation), and further oxidation of products such as PD has been proposed as an important contributor to nucleation. Smog-chamber studies allow us to analyze the chemical change and SOA production from PD. We have constrained the SOA mass yield, defined as the mass of SOA formed divided by the precursor consumed. We hypothesize that oxidation products participating in new-particle formation are a subset of those products forming SOA; SOA mass yields are 10-30%, whereas only a few percent of the oxidation products participate in new-particle formation. An objective of this study was to compare the properties of PD oxidation products observed during new-particle formation experiments at CLOUD and properties of SOA derived from PD in smog-chamber experiments to test this hypothesis.
We measured the elemental composition of SOA formed from PD. The average oxidation state of carbon of formed SOA was calculated based on the elemental composition. The value is around -0.6, which is comparable to the most oxidized SOA observed from the direct oxidation of α-pinene. In contrast, composition data from CLOUD show an oxidation state of -0.2 for the smallest molecular clusters, dropping to -0.8 for clusters containing 4 or more oxidized organic molecules. This is consistent with the initial organic molecules in new-particle formation consisting of a highly-oxidized subset of the PD oxidation products, with the subsequent growth of those clusters being driven by compounds that resemble those comprising the bulk SOA formed from PD.
In order to describe organic aerosol chemical evolution, we plot the volatility and average oxidation state of carbon of the oxidized organic products from PD in the two-dimensional volatility-oxidation space (2-D VBS).