Novel Findings on Molecular SOA Fingerprint Lists: Implications for Interaction of Multiprecursor Oxidation

Abstract

The molecular compositions and formation mechanisms of secondary organic aerosol (SOA) remain incompletely understood. Measurement of SOA fingerprints is vitally important in revealing precursor interactions in mixed systems. In this work, anthropogenic (naphthalene (Nap) and 2-methyl naphthalene (2-MN)) and biogenic (α-pinene (Alp)) precursors and their mixture are OH-oxidized in a chamber to investigate the interaction of precursors on SOA formation. Organics formed from the single and mixed precursor systems are analyzed by using a thermal desorption comprehensive two-dimensional gas chromatography–mass spectrometer (TD-GC×GC-MS). A pixel-based nontargeted analysis technique is deployed to resolve the mass spectra. Nearly 70% of the total response is resolved at the molecular level. The “full spectrum” template is then applied to identify SOA markers with the combination of enhancement ratios of blob quantifier responses. We found that all SOA markers in mixed systems are related to Alp, including 8-hydroxycarvotanacetone, and 5-isopropenyl-2-methyl-7-oxabicyclo[4.1.0]heptan-2-ol. SOA markers of Nap and 2-MN are suppressed in mixed systems, indicating the complexity of the SOA formation mechanism under mixed-precursor conditions. Our work first provides reliable SOA fingerprint lists, which are beneficial in understanding SOA formation mechanisms and modeling.