Size-Resolved Characteristics and Sources of Inorganic Ions, Carbonaceous Components and Dicarboxylic Acids, Benzoic Acid, Oxocarboxylic Acids and α-Dicarbonyls in Wintertime Aerosols from Tianjin, North China

Abstract

Size-resolved aerosols collected at Tianjin, North China in winter were studied for inorganic ions, carbonaceous components, dicarboxylic acids, benzoic acid, oxocarboxylic acids and α-dicarbonyls. Na⁺ found to be the dominant ions, while sum of SO₄²⁻, NO₃⁻ and NH₄⁺ was almost more than half of the total ionic mass in all size fractions. Both inorganic anions and carbonaceous components showed a bimodal distribution. Water-soluble organic carbon (WSOC) accounted for 53.9% to total OC, with 36.0% in fine- and 17.9% in coarse-mode fractions (≤ 2.1 and ≥ 2.1 μm particles, respectively) of aerosols. Most of dicarboxylic acids and related compounds peaked at 0.43–0.65 μm size bin followed by a gradual decrease, except for few species. Average concentrations of total dicarboxylic acids were 1223 and 516 ng m⁻³ in fine and coarse mode fractions, respectively. Oxalic acid found to be the most abundant species followed by phthalic and azelaic acids in fine- and coarse-mode fractions, except the third most abundance of glyoxylic acid in the coarse mode fraction. Based on size-resolved distributions, correlations and mass ratios of selected marker species, we found that inorganic aerosols were mainly derived from sea salt and vehicular exhaust and coal combustion emissions rather than biomass burning and soil dust in winter over the Tianjin region, North China. While dicarboxylic acids and related compounds were mainly originated from fossil fuel including coal combustion and their contributions from biomass burning and marine and terrestrial biogenic emissions were minor. Their in situ secondary formation and transformations were intensive at local and regional scales.