Urban organic aerosol composition in Eastern China differs from North to South: Molecular insight from a liquid chromatography-Orbitrap mass spectrometry study

Abstract

<p><strong>Abstract.</strong> Particulate air pollution in China is influencing human health, ecosystem and climate. However, the chemical composition of particulate aerosol, especially of the organic fraction, is still not well understood. In this study, particulate aerosol samples with a diameter ≤ 2.5 μm (PM<sub>2.5</sub>) were collected in January 2014 in three cities located in Northeast, East and Southeast China, i.e., Changchun, Shanghai and Guangzhou, respectively. Organic aerosol (OA) in the PM<sub>2.5</sub> samples was analyzed by ultrahigh performance liquid chromatography (UHPLC) coupled to high-resolution Orbitrap mass spectrometry in both negative mode (ESI−) and positive mode electrospray ionization (ESI+). After a non-target screening including molecular formula assignments, compounds were classified into five groups based on their elemental composition, i.e., CHO, CHON, CHN, CHOS and CHONS. The CHO, CHON and CHN compounds present the dominant signal abundances of 81–99.7 % in the mass spectra and the majority of these compounds were assigned to mono- and polyaromatics, suggesting that anthropogenic emissions are a large source of urban OA in all three cities. However, the chemical characteristics of these compounds varied among different cities. The degree of aromaticity and the number of polyaromatic compounds were significantly higher in samples from Changchun, which could be attributed to the large emissions from residential heating (i.e., coal combustion) during winter time in Northeast China. Moreover, the ESI− analysis showed higher H / C and O / C ratios for organic compounds in Shanghai and Guangzhou compared to samples from Changchun, indicating that OA in lower latitude regions of China experiences more intense photochemical oxidation processes. The majority of sulfur-containing compounds (CHOS and CHONS) in all cities were assigned to aliphatic compounds with low degrees of unsaturation and aromaticity. Again, samples from Shanghai and Guangzhou exhibit a larger chemical similarity but largely differ from those from Changchun.</p>

Molecular Characteristics of Atmospheric Organosulfates During Summer and Winter Seasons in Two Cities of Southern and Northern China

“…The dominance of aliphatic OS and NOS compounds is consistent with that observed in Figure 4. Similar results have been reported for several other cities in China, such as those in Changchun, Shanghai, and Guangzhou (Wang, Huang, et al., 2021), where the majority of OS compounds were aliphatics. The high abundance of aliphatic OSs in urban environments could be resulted from the interactions of substantial anthropogenic pollutants (e.g., SO 2 and sulfate particles) with biogenic precursors and the intermediate products (Glasius et al., 2018; Wei et al., 2020).…”

Particle characterization and quantification of organic and inorganic compounds from Chinese and Iranian aerosol filter samples using scanning laser desorption/ionization mass spectrometry

“…The relative number of CHO-containing species found in our study is in good agreement with other studies measured in south China and Singapore [46,47]. Since we are able to detect and report other classes of compounds in addition to CHO compounds, such as large carbon fragments, inorganic compounds and PAHs, the relative proportion of CHO compounds is reduced compared to other studies [48]. If we count only organic compounds, the relative percentage of CHO-containing compounds rises to levels between 53 and 75%, as found in other studies [49].…”

Factors Influencing the Molecular Compositions and Distributions of Atmospheric Nitrogen‐Containing Compounds

“…The CHON+ and CHON– compounds were located in areas that corresponded to oxidized unsaturated compounds and intermediately oxidized organic compounds, respectively. The mean H/C and O/C ratios of the CHON+ and CHON– compounds were close to or slightly greater than the mean H/C and O/C ratios of the regional and rural sites of the Pearl River Delta (Jiang et al., 2020; Lin et al., 2012), as well as the mean H/C and O/C ratios of ambient aerosol samples collected in biomass burning potentially influenced sites and large cities such as Beijing (Jiang et al., 2016; Wang et al., 2018), Shanghai (Wang, Hayeck, et al., 2017), Changchun, and Mainz (Wang et al., 2018, 2021). However, the mean H/C and O/C ratios were significantly less than the mean H/C and O/C ratios of urban aged atmospheric aerosols collected from Cambridge, UK; California, USA.…”

“…However, the mean H/C and O/C ratios were significantly less than the mean H/C and O/C ratios of urban aged atmospheric aerosols collected from Cambridge, UK; California, USA. (O'Brien et al., 2014; Rincón et al., 2012; Willoughby et al., 2014); and Guangzhou on hazy days (Wang et al., 2021), as well as the aged atmospheric media of cloud water (Bianco et al., 2018; Zhao et al., 2013) and rainwater(Altieri et al., 2012). Furthermore, the degrees of oxidation and saturation of CHON compounds in Guangzhou were close to the degrees of oxidation and saturation of the BBOA samples (Cai et al., 2020; Song et al., 2018; Tang et al., 2020), vehicle emission, and tunnel aerosols (Tang et al., 2020), but significantly greater than the degrees of oxidation and saturation of fine particles from coal combustion (Song et al., 2018, 2019; Tang et al., 2020) and off‐road engine emissions (Cui et al., 2019).…”