Environ. Sci. Technol. 2008, 42, 5081–5086
Ozonolysis of β-Pinene: Temperature Dependence of Secondary Organic Aerosol Mass Fraction RAVIKANT PATHAK,† NEIL M. DONAHUE,† AND S P Y R O S N . P A N D I S * ,†,‡ Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, and Department of Chemical Engineering, University of Patras, Patra, Greece
Received March 23, 2007. Revised manuscript received February 09, 2008. Accepted April 28, 2008.
The SOA formation from β-pinene ozonolysis at modest precursor concentrations (2-40 ppb) was investigated in the temperature range of 0-40 °C. The presence of inert seeds and high ozone concentrations is necessary to minimize losses of semivolatile vapors to the walls of the smog chamber. β-pinene secondary organic aerosol production increases significantly with decreasing temperature. An increase by a factor of 2-3, depending on the reacted β-pinene concentration, was observed as the temperature decreased from 40 to 0 °C. This increase appears to be due mainly to the shifting of partitioning of the semivolatile SOA components toward the particulate phase and not to a change of the β-pinene product distribution with temperature. The measurements are used to develop a new temperature-dependent parametrization for the fourcomponent basis-set. The parametrization predicts much higher SOA production for β-pinene ozonolysis for typical atmospheric conditions than the values that have been suggested by previous studies.
1. Introduction The total annual global biogenic organic vapor emissions are estimated to be in the range of 490-1150 TgC, greatly exceeding the 100 TgC of the corresponding total anthropogenic emissions (1). β-pinene is one of the most important biogenic secondary organic aerosol (SOA) precursors (1–4). Global annual β-pinene emissions are estimated to be around 33 TgC (1). Approximately 50-60% of the emitted β-pinene reacts with ozone while the rest reacts with OH and NO3 radicals (5). The β-pinene/O3 reaction constant is approximately 6 times smaller than that of the R-pinene ozonolysis (6) because R-pinene has an endo double bond, whereas β-pinene has an exo double bond. In the R-pinene/ O3 system pinonaldehyde, pinonic acid, and pinic acid are the major secondary organic aerosol (SOA) products (7, 8). Nopinone, pinic acid, pinalic-3 acid, 1 and 3-hydroxynopinone are some of the major products of the β-pinene reaction with ozone (8, 9). Laboratory smog chamber studies have demonstrated that the β-pinene SOA production depends strongly on the reacted precursor concentrations, oxidizing agent, the NOx level, and temperature (4, 9- (15)). SOA production is described by an * Corresponding author phone: (1) 412-268 3531; fax: (1) 412-268 7139; e-mail:
[email protected] † Carnegie Mellon University. ‡ University of Patras. 10.1021/es070721z CCC: $40.75
Published on Web 06/14/2008
2008 American Chemical Society
aerosol mass fraction (AMF), the ratio of aerosol produced to precursor consumed (also called aerosol yield in other studies). Hoffman et al. (12) reported an AMF of 0.32 from the ozonolysis of 53 ppb of β-pinene at 20 °C. On the other hand, Griffin et al. (5) measured much lower AMFs varying from almost zero to 0.052 for 12-80 ppb of reacted β-pinene at 35 °C. Ng et al. (15) reported AMFs varying from 0.01 to 0.17 for 30-180 ppb of reacted β-pinene in the dark at room temperature. Despite the above efforts, the SOA AMF at modest β-pinene concentrations (
