Distinctive Sources Govern Organic Aerosol Fractions with Different Degrees of Oxygenation in the Urban Atmosphere

Abstract

Understanding how the sources of an atmospheric organic aerosol (OA) govern its burden is crucial for assessing its impact on the environment and adopting proper control strategies. In this study, the sources of OA over Beijing were assessed yeararound based on the combination of two separation approaches for OA, one from chemical fractionation into the high-polarity fraction of water-soluble organic matter (HP-WSOM), humic-like substances (HULIS), and water-insoluble organic matter (WISOM), and the other from statistical grouping using positive matrix factorization (PMF) of high-resolution aerosol mass spectra. Among the three OA fractions, HP-WSOM has the highest O/C ratio (1.36), followed by HULIS (0.56) and WISOM (0.17). The major sources of different OA fractions were distinct: HP-WSOM was dominated by more oxidized oxygenated OA (96%); HULIS by cooking-like OA (40%), less oxidized oxygenated OA (27%), and biomass burning OA (21%); and WISOM by fossil fuel OA (77%). In addition, our results provide evidence that mass spectralbased PMF factors are associated with specific substructures in molecules. These structures are further discussed in the context of the FT-IR results. This study presents an overall relationship of OA groups monitored by chemical and statistical approaches for the first time, providing insights for future source apportionment studies.

The Relationship between Molecular Size and Polarity of Atmospheric Organic Aerosol in Singapore and Its Implications for Volatility and Light Absorption Properties

“…The dried samples were reconstituted with either 2 mL of ultrapure water or methanol for subsequent analyses. A recent study demonstrated that sequential solvent extraction of filter samples using an ultrasonic bath can quantitatively extract OM …”

“…A recent study demonstrated that sequential solvent extraction of filter samples using an ultrasonic bath can quantitatively extract OM. 88 3.3. Separation of WSOM by the 1-Octanol−Water Extraction Method.…”

Connecting the Light Absorption of Atmospheric Organic Aerosols with Oxidation State and Polarity

“…Solvent extraction from filter samples has been widely used to extract OA with different polarities. Water and alcohol solvents have been widely used to differentiate BrC components according to polarity and to evaluate the absorbing properties for each component. − However, water-soluble OA only represents a limited fraction of the total OA, which accounts for 20–70% of OA and even as low as 20% in some urban environment, , depending on the aging time of aerosols. The extraction efficiency of methanol can reach 80–90%. , Other heavier solvents, such as dichloromethane and hexane, were also used to extract even lower polar OA. , OA at higher molecular weights can be extracted by lower polar solvents, which were found to have higher absorptivity than the more polar water-extractable OA (WSOA). − …”

Abundance, chemical structure, and light absorption properties of humic-like substances (HULIS) and other organic fractions of forest aerosols in Hokkaido

“…In addition to HULIS, OA are also composed of highly polar water-soluble organic matter (HP-WSOM) and water-insoluble organic matter (WISOM). Zhou et al 17 found that the HP-WSOM fraction was most abundant in Beijing, whereas Chen et al 11 found that WISOM was most abundant in Nagoya. Both of these studies reported that HP-WSOM has high O/C ratios (mean: 1.37 and 0.99), while WISOM has low O/C ratios (mean: 0.17 and 0.14) 11 , 17 .…”

“…Zhou et al 17 found that the HP-WSOM fraction was most abundant in Beijing, whereas Chen et al 11 found that WISOM was most abundant in Nagoya. Both of these studies reported that HP-WSOM has high O/C ratios (mean: 1.37 and 0.99), while WISOM has low O/C ratios (mean: 0.17 and 0.14) 11 , 17 . Only a few studies have been reported about the abundance and chemical characteristics of these fractions, although the information is essential to characterize total OA in terms of the fractional contributions of HULIS and non-HULIS fractions.…”