Differences in the composition of organic aerosols between winter and summer in Beijing: a study by direct-infusion ultrahigh-resolution mass spectrometry

Abstract

Abstract. This study investigates the chemical composition of PM2.5 collected at a central location in Beijing, China, during winter 2016 and summer 2017. The samples were characterised using direct-infusion negative-nano-electrospray-ionisation ultrahigh-resolution mass spectrometry to elucidate the composition and the potential primary and secondary sources of the organic fraction. The samples from the two seasons were compared with those from a road-tunnel site and an urban background site in Birmingham, UK, analysed in the course of an earlier study using the same method. There were strong differences in aerosol particle composition between the seasons, particularly regarding (poly-)aromatic compounds, which were strongly enhanced in winter, likely due to increased fossil fuel and biomass burning for heating. In addition to the seasonal differences, compositional differences between high- and low-pollution conditions were observed, with the contribution of sulfur-containing organic compounds strongly enhanced under high-pollution conditions. There was a correlation of the number of sulfur-containing molecular formulae with the concentration of particulate sulfate, consistent with a particle-phase formation process.

Atmospheric conditions and composition that influence PM<sub>2.5</sub> oxidative potential in Beijing, China

“…Furthermore, air mass history may be an important contributor to the observed seasonality of OP. For instance, it was observed that winter days with high PM 2.5 mass concentrations typically originate from regional sources south of Beijing, which is widely industrialised, whereas high mass days in the summer typically have more varied air mass histories ( Panagi et al, 2020 ; Steimer et al, 2020 ). There are likely varying contributions between different sources in different seasons, e.g.…”

“…Significant correlations are also observed between AA m and a range of n-alkanes and hopanes (17a(H)-22, 29, 30trisnorhopane (C27a) and 17b(H)-21a-norhopane (C30ba), Table S6), markers of primary organic aerosol emitted from vehicles (Schauer et al, 1999;Subramanian et al, 2006). Although these species are not redox-active, they are co-emitted with redox-active transition metals such as Fe, V and Cu from vehicle activity, either directly (Bates et al, 2019) or via dust resuspension, and other organics contributing to SOA (Platt et al, 2014) and highlight the potential importance of vehicular emissions on AA m .…”

Nontarget Screening Exhibits a Seasonal Cycle of PM2.5 Organic Aerosol Composition in Beijing

“…These specific compound groups are likely attributed to the increased solid fuel combustion activities in winter. 33 Moreover, unfavorable meteorological conditions (e.g., low wind speed, stagnation of air, and a shallow and stable inversion layer) may promote OA accumulation in Beijing during winter. 42 In contrast, the relative contribution of these two groups to the total intensity in summer are 6% and 8%, respectively.…”

“…We observed an enhanced absolute intensity of organic compounds (Figure C), especially for the intensity of the compound groups CHNO (e.g., nitroaromatics) and CHOa (e.g., oxidized aromatics), which contribute 38% and 17%, respectively, to the total peak intensity during winter. These specific compound groups are likely attributed to the increased solid fuel combustion activities in winter Moreover, unfavorable meteorological conditions (e.g., low wind speed, stagnation of air, and a shallow and stable inversion layer) may promote OA accumulation in Beijing during winter .…”

Emerging Major Role of Organic Aerosols in Explaining the Occurrence, Frequency, and Magnitude of Haze and Fog Episodes during Wintertime in the Indo Gangetic Plain

“…In the VK diagram, slopes of 0, −1, and −2 represent addition of an alcohol/peroxide group, a carboxylic acid group, and a ketone/aldehyde group to the organic compound, respectively. Furthermore, it can be observed from the VK plot that H/C > 1 and O/C > 0.5, which indicates that there is less influence of aromatic compounds and dominance of aliphatic compounds in WSOA at both sites . Mandariya et al observed a shift of the VK slope toward shallower from PrFP (−0.56 ± 0.11) to AFP (−0.47 ± 0.06), indicating the importance of −OH functionalization and fragmentation reactions.…”