title: Two chemically distinct light-absorbing pools of urban organic aerosols: A comprehensive multidimensional analysis of trends.
abstract: The chemical and light-absorption dynamics of organic aerosols (OAs), a master variable in the atmosphere, have yet to be resolved. This study uses a comprehensive multidimensional analysis approach for exploiting simultaneously the compositional changes over a molecular size continuum and associated light-absorption (ultraviolet absorbance and fluorescence) properties of two chemically distinct pools of urban OAs chromophores. Up to 45% of aerosol organic carbon (OC) is soluble in water and consists of a complex mixture of fluorescent and UV-absorbing constituents, with diverse relative abundances, hydrophobic, and molecular weight (Mw) characteristics between warm and cold periods. In contrast, the refractory alkaline-soluble OC pool (up to 18%) is represented along a similar Mw and light-absorption continuum throughout the different seasons. Results suggest that these alkaline-soluble chromophores may actually originate from primary OAs sources in the urban site. This work shows that the comprehensive multidimensional analysis method is a powerful and complementary tool for the characterization of OAs fractions. The great diversity in the chemical composition and optical properties of OAs chromophores, including both water-soluble and alkaline-soluble OC, may be an important contribution to explain the contrasting photo-reactivity and atmospheric behavior of OAs.
authors.affiliation: Department of Chemistry & CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Andreia S
authors.initials: AS
authors.lastname: Paula
authors.affiliation: Department of Chemistry & CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: João T V
authors.initials: JT
authors.lastname: Matos
authors.affiliation: Department of Chemistry, CICECO & CESAM, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: regina.duarte@ua.pt.
authors.forename: Regina M B O
authors.initials: RM
authors.lastname: Duarte
authors.affiliation: Department of Chemistry & CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Armando C
authors.initials: AC
authors.lastname: Duarte
mesh_terms: D000336:Aerosols / Q000032:analysis* / Q000737:chemistry; D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D002947:Cities; D057927:Hydrophobic and Hydrophilic Interactions; D008027:Light; D008970:Molecular Weight; D009930:Organic Chemicals / Q000032:analysis* / Q000737:chemistry; D012621:Seasons; D014867:Water / Q000737:chemistry
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D009930:Organic Chemicals; D014867:Water
keywords: Alkaline-soluble organic matter; Atmospheric aerosols; Chromophores; Comprehensive multidimensional analysis; Light-absorbing properties; Water-soluble organic matter