Fates of secondary organic aerosols in the atmosphere identified from compound-specific dual-carbon isotope analysis of oxalic acid

[摘要] Secondary organic aerosols (SOAs) are important components of fineparticulates in the atmosphere. However, the sources of SOA precursor andatmospheric processes affecting SOAs are poorly understood. This limits ourabilities to improve air quality and model aerosol-mediated climate forcing.Here, we use novel compound-specific dual-carbon isotope fingerprints( Δ 14 C and δ 13 C) for individual SOA tracer molecules(i.e., oxalic acid) to investigate the fates of SOAs in the atmosphere atfive emission hotspots in China. Coal combustion and vehicle exhaustaccounted for ∼  55 % of the sources of carbon in oxalic acidin Beijing and Shanghai, but biomass burning and biogenic emissionsaccounted for ∼  70 % of the sources of carbon in oxalic acidin Chengdu, Guangzhou, and Wuhan during the sampling period. The dual-carbonisotope signatures of oxalic acid and bulk organic carbon pools (e.g.,water-soluble organic carbon) were compared to investigate the fates of SOAsin the atmosphere. Photochemical aging and aqueous-phase chemical processesdominate the formation of oxalic acid in summer and in winter, respectively.The results indicated that SOA carbon sources and chemical processesproducing SOAs vary spatially and seasonally, and these variations need to beincluded in Chinese climate projection models and air quality managementpractices.

[学科分类] 医学（综合）