The characterization of ambient levoglucosan in Beijing during summertime: Dynamic variation and source contributions...

Particulate levoglucosan is an important tracer for biomass burning emission in ambient air. However, recent studies question its reliability as a biomass burning tracer in Chinese mega cities due to important contribution from potential non-biomass burning sources, such as cooking. To address this, we examined the dynamic variation and sources of levoglucosan using a chemical ionization mass spectrometer and other advanced instruments during Beijing's summer of 2021. The average mass concentration of levoglucosan and its isomer (C₆H₁₀O₅) was 0.025 ± 0.014 µg/m³, constituting 0.55 % ± 0.32 % of total organic carbon (OC) in this campaign. Despite cooking emissions contributing significantly to the organic aerosol (OA, 20 %), levoglucosan and its isomers correlated more strongly with biomass-burning related tracers (R > 0.6), black carbon (R = 0.72) and less so with cooking-related sources (R = 0.3). This indicates that levoglucosan is primarily dominated by biomass-burning emissions rather than cooking in Beijing's urban areas during summertime. The diurnal variation of levoglucosan concentrations highlighted the importance of daytime and nocturnal biomass burning emissions during polluted periods in Beijing. Using levoglucosan as a tracer to quantify the biomass burning OC (BBOC), we found good agreement on the time series of BBOC between the tracer method and other independent source apportionment method. This reaffirms the reliability of levoglucosan as a biomass burning tracer. Biomass burning contributed an average of 7 %-8 % to OC, highlighting its significant impact on Beijing's summer air quality. Our study enhances understanding of biomass burning influences on ambient aerosol in typical urban areas.