Seasonal variation, source contribution, and impact factors of biogenic organic aerosols in PM2.5 in Nanjing, China

Abstract

In this study, a liquid chromatography–mass spectrometry (HPLC-ESI-MS/MS) was used to develop a rapid method to detect carbohydrates (one anhydrosugar, five sugars, and four sugar alcohols) and monoterpene secondary organic aerosol (SOAM) tracers in the atmosphere, successfully applied to 139 atmospheric aerosol samples in Nanjing in 2019. Anhydrosugar (levoglucosan) is the most abundant carbohydrate in the atmospheric environment, with an annual mean concentration of 103.96 ng m−3. The measured compounds exhibited distinct seasonal variation, with a higher concentration in spring and summer and a lower concentration in autumn and winter. The distinct seasonal variation in these Bioorganic aerosol (BOA) tracers may be caused by the different dominant sources in different seasons. Their seasonal trends are also similar to other worldwide observations. In Nanjing, the yield of SOAM tracers is affected by meteorological conditions and anthropogenic pollutants (e.g., NO2 and O3). Furthermore, five source factors (secondary formation, biomass burning, soil resuspension, plant debris, and fungal spores) of BOA and their geographic origin were obtained using the Positive Matrix Factor (PMF) and Potential Source Contribution Factor (PSCF) models. The contribution of these factors to BOA also varies, with biomass burning (77.4 %) contributing the most, followed by fungal spores (12.2 %) and soil suspension (2.1 %).