Chemical characterization of oxygenated organic compounds in the gas phase and particle phase using iodide CIMS with FIGAERO in urban air

Abstract

Abstract. The atmospheric processes under polluted environments involving interactions of anthropogenic pollutants and natural emissions lead to the formation of various and complex secondary products. Therefore, the characterization of oxygenated organic compounds in urban areas remains a pivotal issue in our understanding of the evolution of organic carbon. Here, we describe measurements of an iodide chemical ionization\ntime-of-flight mass spectrometer installed with a Filter Inlet for Gases and\nAEROsols (FIGAERO-I-CIMS) in both the gas phase and the particle phase at an urban\nsite in Guangzhou, a typical megacity in southern China, during the autumn\nof 2018. Abundant oxygenated organic compounds containing two to five oxygen atoms\nwere observed, including organic acids, multi-functional organic compounds\ntypically emitted from biomass burning, oxidation products of biogenic\nhydrocarbons and aromatics. Photochemistry played dominant roles in the\nformation of gaseous organic acids and isoprene-derived organic nitrates,\nwhile nighttime chemistry contributed significantly to the formation of\nmonoterpene-derived organic nitrates and inorganics. Nitrogen-containing\norganic compounds occupied a significant fraction of the total signal in\nboth the gas and particle phases, with elevated fractions at higher\nmolecular weights. Measurements of organic compounds in the particle phase\nby FIGAERO-I-CIMS explained 24\u2009 ± \u20090.8\u2009% of the total organic aerosol\nmass measured by aerosol mass spectrometer (AMS), and the fraction increased\nfor more aged organic aerosol. The systematical interpretation of mass\nspectra of the FIGAERO-I-CIMS in the urban area of Guangzhou provides a\nholistic view of numerous oxygenated organic compounds in the urban\natmosphere, which can serve as a reference for the future field measurements\nby FIGAERO-I-CIMS in polluted urban regions.