Abstract
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-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 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 molecules cm−3 s, was 1. 35 ± 0. 30 µg min−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 (cooking-related 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 semi-volatile oxygenated organic aerosol (SV-OOA), indicating that SOA in these experiments was lightly oxidized.
Highlights
Organic aerosol (OA) is an important component of atmospheric particulate matter (PM), which influences air quality, climate and human health (Hallquist et al, 2009)
During the initial 10 min of heating, the mass concentration of organics was close to the detection limit of the instrument, indicating that primary organic aerosol (POA) emissions were thoroughly removed by the Teflon filter
During these periods of experiments where OH radicals were not present, we found that ozone chemistry had a negligible influence on secondary organic aerosol (SOA) formation in this study
Summary
Organic aerosol (OA) is an important component of atmospheric particulate matter (PM), which influences air quality, climate and human health (Hallquist et al, 2009). A significant fraction of OA is secondary organic aerosol (SOA) (Zhang et al, 2007), formed via the oxidation of volatile organic compounds (VOCs) (Hallquist et al, 2009). Cooking-related organic aerosol (COA), thought to be primary in origin, contributed 10–34.6 % of the total OA in urban areas (Allan et al, 2010; Sun et al, 2011, 2012; Ge et al, 2012; Mohr et al, 2012; Crippa et al, 2013; Lee et al, 2015). Lee et al (2015) found that COA even dominated the contribution to POA at roadside sites in the commercial and shopping area of Mongkok in Hong Kong. Cooking may be a large source of SOA in urban areas, yet the formation of SOA from cooking remains poorly understood.
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