Abstract
Abstract. We have investigated the production of secondary organic aerosol (SOA) from pinanediol (PD), a precursor chosen as a semi-volatile surrogate for first-generation oxidation products of monoterpenes. Observations at the CLOUD facility at CERN have shown that oxidation of organic compounds such as PD can be an important contributor to new-particle formation. Here we focus on SOA mass yields and chemical composition from PD photo-oxidation in the CMU smog chamber. To determine the SOA mass yields from this semi-volatile precursor, we had to address partitioning of both the PD and its oxidation products to the chamber walls. After correcting for these losses, we found OA loading dependent SOA mass yields from PD oxidation that ranged between 0.1 and 0.9 for SOA concentrations between 0.02 and 20 µg m−3, these mass yields are 2–3 times larger than typical of much more volatile monoterpenes. The average carbon oxidation state measured with an aerosol mass spectrometer was around −0.7. We modeled the chamber data using a dynamical two-dimensional volatility basis set and found that a significant fraction of the SOA comprises low-volatility organic compounds that could drive new-particle formation and growth, which is consistent with the CLOUD observations.
Highlights
Particulate matter (PM) in the atmosphere affects human health and life expectancy (Pope et al, 2009) and influences Earth’s climate by absorbing and scattering radiation (Solomon et al, 2007)
Our studies show that oxidation of pinanediol, a semi-volatile surrogate for first-generation oxidation products of monoterpenes, can produce Secondary organic aerosol (SOA) with very high mass yields
Along with previously studied model systems for first-generation products, this shows that aging of semi-volatile SOA is a significant source of additional SOA mass, with higher mass yields typical of less volatile first-generation products
Summary
Particulate matter (PM) in the atmosphere affects human health and life expectancy (Pope et al, 2009) and influences Earth’s climate by absorbing and scattering radiation (Solomon et al, 2007). Secondary organic aerosol (SOA), formed from oxidation of gas-phase organic compounds in the atmosphere, accounts for a significant fraction of the organic aerosol (OA) in PM (Zhang et al, 2007). Classical smog-chamber experiments encompass only the early stages of SOA formation, including one generation or at most a few generations of oxidation chemistry (Pandis et al, 1991; Odum et al, 1996a). While those experiments may include some later-generation chemistry, the commonly used two-product model (Odum et al, 1996a) treats the (quasi-)first-generation products as effectively non-reactive
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