Formation of secondary organic aerosols from gas-phase emissions of heated cooking oils

Abstract

Cooking emissions can potentially contribute to secondary organic aerosol (SOA) but remain poorly understood. In this study, formation of SOA from gas-phase emissions of five heated vegetable oils (i.e., corn, canola, sunflower, peanut and olive oils) was investigated in a potential aerosol mass (PAM) chamber. Experiments were conducted at 19-20 °C and 65-70% relative humidity (RH). The characterization instruments included a scanning mobility particle sizer (SMPS) and a high-resolution time-offlight aerosol mass spectrometer (HR-TOF-AMS). The efficiency of SOA production, in ascending order, was peanut oil, olive oil, canola oil, corn oil and sunflower oil. The major SOA precursors from heated cooking oils were related to the content of monounsaturated fat and omega-6 fatty acids in cooking oils. The average production rate of SOA, after aging at an OH exposure of 1.7×1011 moleculescm-3 s, was 1.35±0.30 μgmin-1, 3 orders of magnitude lower compared with emission rates of fine particulate matter (PM2.5) from heated cooking oils in previous studies. The mass spectra of cooking SOA highly resemble field-derived COA (cookingrelated organic aerosol) in ambient air, with R2 ranging from 0.74 to 0.88. The average carbon oxidation state (OSc) of SOA was -1.51 to -0.81, falling in the range between ambient hydrocarbon-like organic aerosol (HOA) and semivolatile oxygenated organic aerosol (SV-OOA), indicating that SOA in these experiments was lightly oxidized.