Chemical interactions within biomass-burning emissions significantly influence the composition and optical properties of nanoscale secondary organic aerosols

Abstract

Biomass burning (BB) emits a substantial amount of trace gases, and their atmospheric oxidation makes a large contribution to secondary organic aerosol (SOA) formation. However, the potential interactive effect of mixed volatile organic compounds (VOCs) from BB on SOA formation remains largely unknown. Here, we studied the molecular composition and optical properties of nanoscale SOA formed from the mixture of two typical VOCs in BB emissions (styrene and furan) with distinct chemical characteristics. The ratio of furan to styrene was controlled within a range of 0.5–10, based on actual emission ratios. By investigating SOA variations at the molecular level, we found that the SOA yield and light absorption in the furan–styrene mixture system were significantly lower than those in the styrene system. The decrease in SOA yield in the mixture experiments might be explained by changes in the distribution of organic aerosol components. Specifically, the addition of furan reduced the proportion of low-volatility organic compounds and increased the proportion of semi-volatile organic compounds. Tandem mass spectrometry (MS/MS) analysis indicated that the reduction in light absorption after furan addition could be attributed to the suppressed formation of nitrophenolic compounds, since typical chromophores such as C₆H₅NO₃ and C₆H₅NO₄ were only identified in styrene SOA. These findings highlight the complex interactions between organic gases in BB emissions and their significant impact on SOA formation and optical properties.