In order to investigate the spatial distributions and aging of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls in Northeast Asia, we collected fine aerosols (PM_2.5) in Tianjin (TJ), northern China and in Padori (PD) and Daejoen (DJ), South Korea during winter 2019. We measured the molecular and compound-specific carbon isotopic composition (δ¹³C) of diacids, oxoacids and α-dicarbonyls in selected sets of the PM_2.5 samples, covering a clean and a polluted periods during the campaign. Concentrations of diacids, oxoacids, and a-dicarbonyls were higher in polluted days than in clean days and were high in TJ followed by DJ and PD in the former case, whereas in DJ followed by TJ and PD in the latter case. Relative abundances of C₉ in their total straight chain diacids (ΣC₂–C₁₂) mass in PM_2.5 in DJ was significantly lower than that in TJ and PD. The correlations and mass ratios between selected species (and/or components), together with the δ¹³C of diacids and related compounds, revealed that the secondary formation of aerosols and their aging is dominant in PD and local anthropogenic emissions are dominant in TJ, while both of them are important in DJ.
 

Dicarboxylic acids; Stable carbon isotopic composition; sources; aging; PM2.5; Northeast Asia