Chemical Structural Characteristics of HULIS and Other Fractionated Organic Matter in Urban Aerosols: Results from Mass Spectral and FT-IR Analysis

Abstract

The chemical characteristics of complex organic matter in atmospheric aerosols remain poorly understood. Water-insoluble organic matter (WISOM) and water-soluble organic matter (WSOM) in the total suspended particulates collected in the city of Nagoya in summer/early autumn and winter were extracted using multiple solvents. Two fractions of humic-like substances, showing neutral and acidic behavior (HULIS-n and HULIS-a, respectively), and the remaining highly polar part (HP-WSOM) were fractionated from WSOM using solid phase extraction. The chemical structural characteristics and concentrations of the organic matter were investigated using mass spectrometry and Fourier transform infrared (FT-IR) spectroscopy. WISOM and HULIS-n had low O/C ratios (0.1 and 0.4, respectively) and accounted for a large fraction of the organics in aerosols (70%). HULIS-a and HP-WSOM had higher O/C ratios (0.7 and 1.0, respectively), and their concentrations in summer and early autumn were on average ∼2 times higher than those in winter. The mass spectrum and FT-IR analyses suggest the following: (1) WISOM were high-molecular-weight aliphatics (primarily C27-C32) with small proportions of -CH3, -OH, and C═O groups; (2) HULIS-n was abundant in aliphatic structures and hydroxyl groups (primarily C9-C18) and by branched structures; (3) HULIS-a and HP-WSOM contained relatively large amounts of low-molecular-weight carboxylic acids and alcohols (primarily C4-C10); and (4) WISOM and HULIS-n were relatively abundant in amines and organic nitrates.

Water uptake by fresh Indonesian peat burning particles is limited by water-soluble organic matter

“…The complexity in chemical composition inhibits understanding their water uptake properties at molecular levels (Asa-Awuku et al, 2008;Psichoudaki and Pandis, 2013;Riipinen et al, 2015). To overcome this difficulty, classification of organic compounds using multiple solvents Polidori et al, 2008;Chen et al, 2016), liquid-liquid extraction using 1-octanol and water (Kuwata and Lee, 2017), and solid-phase extraction (Asa-Awuku et al, 2008) has been conducted. Functional-group analysis of segregated organic matter has also been demonstrated as a strong tool to characterize complex mixture of organic compounds (Chen et al, 2016).…”

“…To overcome this difficulty, classification of organic compounds using multiple solvents Polidori et al, 2008;Chen et al, 2016), liquid-liquid extraction using 1-octanol and water (Kuwata and Lee, 2017), and solid-phase extraction (Asa-Awuku et al, 2008) has been conducted. Functional-group analysis of segregated organic matter has also been demonstrated as a strong tool to characterize complex mixture of organic compounds (Chen et al, 2016). For instance, chemical characteristics of water-soluble organic matter (WSOM) have been intensively investigated, revealing that WSOM predominantly consists of levoglucosan-like species, carboxylic acids, aldehydes, ketones, aliphatic alcohols, and polyacids (Decesari et al, 2000;Peng et al, 2001;Suzuki et al, 2001;MayolBracero et al, 2002;Chan et al, 2005;Psichoudaki and Pandis, 2013).…”

Chemical characterization of humic-like substances (HULIS) in PM2.5 in Lanzhou, China

“…HULIS are of special interest because of their ubiquity, high level, surface activity, light-absorbing capability and photochemical activity. HULIS can affect aerosol properties, such as hygroscopicity, cloud condensation nucleus, surface tension, and optical property (Kiss et al, 2005;Dinar et al, 2007;Fan et al, 2012;Chen et al, 2016). Because of their aqueous solubility and surface activity, HULIS also play an important role on the activation of aerosol particle into cloud droplets, and thereby have important impacts on climate change Kiss et al, 2005;Dinar et al, 2007).…”

Towards the isolation and estimation of elemental carbon in atmospheric aerosols using supercritical fluid extraction and thermo-optical analysis

“…The removal of 49–57% OC using scCO 2 with addition of 10% methanol shows that the aerosol samples used in the experiments may contain up to 57% non-polar to medium polar organic compounds. The removed fraction may include organic compounds with low molecular masses, e.g., carboxylic acids, anhydrous sugars, methoxyphenols, and other similar classes of organic compounds as reported in earlier studies [35]. No characterization of extracted organic compounds was performed.…”

“…This makes scCO 2 modified with a co-solvent suitable for the extraction (in a single step) of a wide range of OC fractions, ranging from non-polar to medium polar compounds. Studies on characterization of humic-like substances and organic matter in ambient aerosols demonstrate that up to 70% of organic mass consists of water-insoluble organic matter and neutral humic-like substances with an O/C ratio of 0.1 and 0.4, respectively [35]. The water-insoluble organic matter with an O/C ratio of 0.1 is more likely to undergo pyrolysis in TOA protocols.…”