Diurnal Variations in High Time-Resolved Molecular Distributions and Formation Mechanisms of Biogenic Secondary Organic Aerosols at Mt. Huang, East China

The molecular characteristics and formation mechanism of biogenic secondary organic aerosols (BSOAs) in the forested atmosphere are poorly known. Here, we report temporal variations processes BSOA tracers derived from isoprene, monoterpenes, β caryophyllene PM2.5 samples collected at foot Mt. Huang (483 m a. s. l) East China during summer 2019 with a 3 h time resolution. concentrations nearly all detected species, including carbon (OC), elemental (EC), levoglucosan, SIA (sum SO42−, NO3−, NH4+), were higher night (19:00–7:00 next day) than daytime (7:00–19:00). In addition, air pollutants that accumulated by dynamic transport mountain breeze also crucial reason for tracers. Most exhibited peaked 1:00 to 4:00 or 7:00. Those presented strong correlations O3 rather night, indicating BSOAs primarily photo-oxidation BVOCs O3. close SO42− particle acidity (pHis) suggest acid-catalyzed aqueous-phase oxidation. Considering relative humidity LWC concentration promoted aqueous oxidation was essential night. Moreover, levoglucosan robust correlation tracers, especially β-caryophyllinic acid, suggesting biomass burning long-distance exerted significant impact on formation. Based tracer-based method, estimated (SOC) (0.90 ± 0.57 µgC m−3) those (0.53 0.34 daytime, accounting 14.5 8.5% 12.2 5.0% OC, respectively. Our results reveal mountain-valley breezes anthropogenic long-range transport.