Formation of secondary organic aerosols from gas–phase emissions of heated cooking oils
Tengyu Liu1, Zijun Li2, ManNin Chan2,3, and Chak K. Chan11School of Energy and Environment, City University of Hong Kong, Hong Kong, China 2Earth System Science Programme, The Chinese University of Hong Kong, Hong Kong, China 3The Institute of Environment, Energy and Sustainability, The Chinese University of Hong Kong, Hong Kong, China
Received: 29 Jan 2017 – Accepted for review: 30 Jan 2017 – Discussion started: 31 Jan 2017
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 ºC and 65–70 % RH. The characterization instruments included a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight 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 mono-unsaturated 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 molecules cm−3 s, was 1.35 ± 0.30 µg min−1, three 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 (cooking-related organic aerosol) in ambient air, with R2 ranging from 0.74 to 0.88, suggesting that COA might not be entirely primary in origin. The average carbon oxidation state (OSc) of SOA was −1.51–−0.81, falling in the range between ambient hydrocarbon-like organic aerosol (HOA) and semi-volatile oxygenated organic aerosol (SV-OOA), indicating that SOA in these experiments was lightly oxidized.
Liu, T., Li, Z., Chan, M., and Chan, C. K.: Formation of secondary organic aerosols from gas–phase emissions of heated cooking oils, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-77, in review, 2017.