Ozonolysis of β-Pinene: Temperature Dependence of Secondary Organic Aerosol Mass Fraction

The SOA formation from beta-pinene ozonolysis at modest precursor concentrations (2-40 ppb) was investigated in the temperature range of 0-40 degrees 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. beta-pinene secondary organic aerosol production increases significantly with decreasing temperature. An increase by a factor of 2-3, depending on the reacted beta-pinene concentration, was observed as the temperature decreased from 40 to 0 degrees C. This increase appearsto be due mainly to the shifting of partitioning of the semivolatile SOA componentstoward the particulate phase and not to a change of the beta-pinene product distribution with temperature. The measurements are used to develop a new temperature-dependent parametrization for the four-component basis-set. The parametrization predicts much higher SOA production for beta-pinene ozonolysis for typical atmospheric conditions than the values that have been suggested by previous studies.