Molecular Characterization of Firework-Related Urban Aerosols using FT-ICR Mass Spectrometry

Firework (FW) emissions have strong impacts on air quality and public health. However, little is known about the molecular composition of FW-related aerosols especially the organic fraction. Here we describe the detailed molecular composition of Beijing aerosols collected before, during, and after a FW event in New Year's Eve evening. Subgroups of CHO, CHNO, CHOS, and CHNOS were characterized using ultrahigh resolution Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry. We found that high molecular weight compounds with relatively low H/C and O/C ratios and high degree of unsaturation were greatly enhanced during the New Year’s Eve, which are likely to be aromatic-like compounds. They plausibly contributed to the formation of brown carbon and affect the light absorption properties of atmospheric aerosols. Moreover, the number concentration of sulfur-containing compounds especially the nitrooxy-organosulfate was increased dramatically by the FW event, suggesting the important effect of nighttime chemistry on their formation. But, the number concentration of CHO and CHON doubled after the event with photooxidation. The co-variation of these subgroups was suggested to be associated with multiple atmospheric aging processes of aerosols including the multiphase redox chemistry driven by NO_x, O₃, and ^·OH. Our study provides new insights into the anthropogenic emissions for urban SOA formation.