Novel Findings\non Molecular SOA Fingerprint Lists:\nImplications for Interaction of Multiprecursor Oxidation

The molecular compositions and formation mechanisms of\nsecondary\norganic aerosol (SOA) remain incompletely understood. Measurement\nof SOA fingerprints is vitally important in revealing precursor interactions\nin mixed systems. In this work, anthropogenic (naphthalene (Nap) and\n2-methyl naphthalene (2-MN)) and biogenic (α-pinene (Alp)) precursors\nand their mixture are OH-oxidized in a chamber to investigate the\ninteraction of precursors on SOA formation. Organics formed from the\nsingle and mixed precursor systems are analyzed by using a thermal\ndesorption comprehensive two-dimensional gas chromatography–mass\nspectrometer (TD-GC×GC-MS). A pixel-based nontargeted analysis\ntechnique is deployed to resolve the mass spectra. Nearly 70% of the\ntotal response is resolved at the molecular level. The “full\nspectrum” template is then applied to identify SOA markers\nwith the combination of enhancement ratios of blob quantifier responses.\nWe found that all SOA markers in mixed systems are related to Alp,\nincluding 8-hydroxycarvotanacetone, and 5-isopropenyl-2-methyl-7-oxabicyclo[4.1.0]heptan-2-ol.\nSOA markers of Nap and 2-MN are suppressed in mixed systems, indicating\nthe complexity of the SOA formation mechanism under mixed-precursor\nconditions. Our work first provides reliable SOA fingerprint lists,\nwhich are beneficial in understanding SOA formation mechanisms and\nmodeling.