Abstract
Abstract. In the present work, we conducted experiments of secondary organic aerosol (SOA) formation from urban cooking and vehicular sources to characterize the mass spectral features of primary organic aerosol (POA) and SOA using an high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Our results showed that the cooking styles have a greater impact on aged COA (cooking organic aerosol) mass spectra than oxidation conditions. However, the oxidation conditions affect the aged HOA (hydrocarbon-like OA) spectra more significantly than vehicle operating conditions. In our study, we use mass spectra similarity analysis and positive matrix factorization (PMF) analysis to establish the POA and SOA mass spectra of these two sources. These mass spectra are used as source constraints in a multilinear engine (ME-2) model to apportion the OA (organic aerosol) sources in the atmosphere. Compared with the traditional ambient PMF results, the improved ME-2 model can better quantify the contribution of POA and SOA from cooking and vehicular sources. Our work, for the first time, establishes the vehicle and cooking SOA source profiles, and can be further used in the OA source apportionment in the ambient atmosphere.
Highlights
Organic aerosol (OA) is an important component of fine particulate matter and has significant environmental and health effects, especially in urban areas (Guo et al, 2012, 2014; Ying et al, 2020)
All the aged hydrocarbonlike OA (HOA) spectral profiles from different vehicle running conditions showed a similar pattern, and the θ angles among the mass spectra of aged HOA were less than 10◦ at equivalent photochemical age (EPA) 0.6 d (Table 1), suggesting little difference between the mass spectra
The mass spectra of aged HOA at 0.6 d were dominated by the ion series of CnH+2n+1 (m/z 29, 43, 57, 71, 85) and CnH+2n−1 (m/z 41, 55, 69, 83), resulting from fewer oxidized components such as saturated alkanes
Summary
Organic aerosol (OA) is an important component of fine particulate matter and has significant environmental and health effects, especially in urban areas (Guo et al, 2012, 2014; Ying et al, 2020). Based on collocated AMS measurements and factor analysis results, the SOA formed by vehicle and cooking sources cannot be effectively resolved from the total SOA due to the lack of secondary mass spectral profiles. The POA mass spectral profiles based on AMS, including HOA (Collier et al, 2015), BBOA (Alfarra et al, 2007; He et al, 2010; Xu et al, 2020), and COA (He et al, 2010; Liu et al, 2017; Mohr et al, 2012; Xu et al, 2020), have been fully explored in laboratory studies and applied as constraint factors into the ME-2 model in the ambient air. We verified the mass spectral profiles by applying POA and SOA profiles to ME-2 for source apportionment of OA in the winter observation with various primary emissions and the summer observation with high-oxidation conditions
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