Comparison of Amazonian biomass burning and East Asian marine aerosols : Bulk organics, diacids and related compounds, water-soluble inorganic ions, stable carbon and nitrogen isotope ratios

In this study, biomass burning and marine aerosols collected in the Amazon, Brazil and on an island south of South Korea are compared in terms of chemical characteristics and ageing by the determination of water-soluble organic carbon (WSOC), water-insoluble organic carbon (WIOC), elemental carbon (EC), diacids (C2-C11) and related compounds (ketoacids and α-dicarbonyls), stable carbon isotopic ratios (δ13C) of total carbon (TC), and nitrogen isotopic ratios (δ15N) of total nitrogen (TN). The concentration ratios of WSOC, WIOC, and EC to aerosol mass are 2-12 times higher in biomass burning aerosols than in marine aerosols. In contrast, concentration ratios of water-soluble cations and anions to aerosol mass are lower by a factor of 0.2-0.6 in biomass burning aerosols than in marine aerosols. Among diacids and related compounds, oxalic acid (C2) was found to be the most abundant, followed by succinic acid (C4) in biomass burning aerosols, while malonic acid (C3) dominated in marine aerosols. Lower relative abundances of C2-C4 diacids, unsaturated diacids, and α-dicarbonyls in total diacids and related compounds were observed in biomass burning aerosols than in marine aerosols, whereas those of C5-C11 diacids, branched diacids, multifunctional diacids, and ketoacids were higher in biomass burning aerosols. These results suggest that there are significant differences in the sources and photochemical production pathways of individual diacids and related compounds. While the δ13C values (－26.5 to －20.5‰) of TC and δ15N values (＋6.8 to ＋26.9 ‰) of TN showed a large variation in marine aerosols, the variations were rather small (δ13C:－26.1 to －23.6‰; δ15N: ＋21.5 to ＋25.7‰) in biomass-burning aerosols. We propose that these δ13C and δ15N values can be used to characterize biomass-burning aerosols.