Molecular Composition and Formation Mechanism of Benzene SOA under Diurnal Oxidation Conditions

Aromatic hydrocarbon secondary organic aerosols (SOAs) derived from anthropogenic sources are a typical class of secondary organic aerosols that significantly impact global climate and human health. The composition and physicochemical properties of atmospheric aerosols are notably influenced by varying oxidation conditions during the day and night. Currently, the molecular composition and formation mechanism of SOAs generated from benzene under diurnal oxidation conditions remain unclear. This study focuses on the molecular composition and chemical formation mechanism of secondary organic aerosols (SOAs) derived from benzene. We utilized the SAPHIR smog chamber to simulate diurnal oxidation experiments of benzene. The molecular composition evolution of benzene SOAs was characterized in real-time online using an Extractive Electrospray Ionization Chemical Ionization Mass Spectrometer (EESI-CIMS). We compared the differences in SOA composition under different oxidation conditions during the day and night, identified key characteristic products, and ultimately proposed relevant mechanisms for SOA formation. This research not only enhances our understanding of the chemical formation mechanisms of SOAs but also provides a scientific basis for air pollution control and climate change assessment.