Markers for anthropogenic sources of secondary organic aerosol: new evaluation from simulation chamber study

Molecular markers are useful to identify the sources of secondary organic aerosols (SOA) by linking them to their precursor volatile organic compounds (VOCs) through their oxidation processes. To advance the apportionment of the anthropogenic contribution to SOA, this work determines the ratio of markers to total SOA mass ( f SOA ) by smog chamber experiments on the photo-oxidation of toluene, m-xylene and naphthalene at different experimental conditions. The aerosol chemical composition was determined by a combination of high-resolution mass spectrometry (HRMS), gas chromatography coupled to mass spectrometry (GC-MS) and ultrahigh performance liquid chromatography electrospray ionization coupled to ion mobility time of flight mass spectrometry (UPLC/ESI-IMS-QTOFMS). The mass fraction of dihydroxy-4-oxo-pentanoic acid (DHOPA) in the aerosol ( f SOA,DHOPA ), associated with toluene and m-xylene oxidation, showed higher values than those previously reported and a dependency on humidity levels during oxidation was found. On the other hand, the f SOA of phthalic acid, associated with naphthalene oxidation, showed the same value as the one previously reported in the literature at different atmospheres. This study highlights that proper selection of the f SOA at relevant atmospheric conditions is required to estimate reliably the contribution of monoaromatics oxidation to SOA.