Significant Production of Secondary Organic Aerosol from Emissions of Heated Cooking Oils

Cooking emissions have been identified as a major source of primary organic aerosol (POA) in urban environments. Cooking may also be a potential source of secondary organic aerosol (SOA) because of the abundant emissions of non-methane organic gases. We studied SOA formation from the photooxidation of emissions from seven vegetable oils heated at 200 °C under high-NO_x conditions in a smog chamber. After the samples had been aged under an OH exposure of 1.0 × 10¹⁰ molecules cm^-3 s, the SOA formation rate was generally 1 order of magnitude higher than the POA emission rate. We determined that alkenals, which are not traditional SOA precursors in chemical transport models, accounted for 5-34% of the observed SOA. The unexplained SOA may be attributed to the oxidation of primary semivolatile and intermediate-volatility organic compounds (SVOCs and IVOCs, respectively), which were estimated to contribute an additional 9-106% of the observed SOA assuming the volatility distribution of heated cooking oils is the same as that of vehicle exhaust. Our results suggest that cooking can potentially be an important source of SOA in urban areas and that there is a need to characterize both SVOCs and IVOCs emitted from cooking and their SOA yields.