Articles | Volume 18, issue 14
Atmos. Chem. Phys., 18, 10693–10713, 2018
Atmos. Chem. Phys., 18, 10693–10713, 2018

Research article 26 Jul 2018

Research article | 26 Jul 2018

The secondary formation of organosulfates under interactions between biogenic emissions and anthropogenic pollutants in summer in Beijing

Yujue Wang1, Min Hu1,5, Song Guo1, Yuchen Wang3, Jing Zheng1, Yudong Yang1, Wenfei Zhu6, Rongzhi Tang1, Xiao Li1, Ying Liu1,5, Michael Le Breton2, Zhuofei Du1, Dongjie Shang1, Yusheng Wu1, Zhijun Wu1, Yu Song1, Shengrong Lou6, Mattias Hallquist2, and Jianzhen Yu3,4 Yujue Wang et al.
  • 1State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
  • 2Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
  • 3Environmental Science Programs, Hong Kong University of Science & Technology, Hong Kong, China
  • 4Department of Chemistry, Hong Kong University of Science & Technology, Hong Kong, China
  • 5Beijing Innovation Center for Engineering Sciences and Advanced Technology, Peking University, Beijing 100871, China
  • 6Shanghai Academy of Environmental Sciences, Shanghai 200233, China

Abstract. Organosulfates (OSs) with ambiguous formation mechanisms are a potential source of missing secondary organic aerosol (SOA) in current atmospheric models. In this study, we chemically characterized OSs and nitrooxy-OSs (NOSs) formed under the influence of biogenic emissions and anthropogenic pollutants (e.g., NOx, SO42−) in summer in Beijing. An ultrahigh-resolution mass spectrometer equipped with an electrospray ionization source was applied to examine the overall molecular composition of S-containing organics. The number and intensities of S-containing organics, the majority of which could be assigned as OSs and NOSs, increased significantly during pollution episodes, which indicated their importance for SOA accumulation. To further investigate the distribution and formation of OSs and NOSs, high-performance liquid chromatography coupled with mass spectrometry was employed to quantify 10 OSs and 3 NOS species. The total concentrations of quantified OSs and NOSs were 41.4 and 13.8 ng m−3, respectively. Glycolic acid sulfate was the most abundant species among all the quantified species, followed by monoterpene NOSs (C10H16NO7S). The total concentration of three isoprene OSs was 14.8 ng m−3 and the isoprene OSs formed via the HO2 channel were higher than those formed via the NO ∕ NO2 channel. The OS concentration coincided with the increase in acidic sulfate aerosols, aerosol acidity, and liquid water content (LWC), indicating the acid-catalyzed aqueous-phase formation of OSs in the presence of acidic sulfate aerosols. When sulfate dominated the accumulation of secondary inorganic aerosols (SIAs; sulfate, nitrate, and ammonium; SO42− ∕ SIA > 0.5), OS formation would obviously be promoted as the increasing of acidic sulfate aerosols, aerosol LWC, and acidity (pH < 2.8). Otherwise, acid-catalyzed OS formation would be limited by lower aerosol acidity when nitrate dominated the SIA accumulation. The nighttime enhancement of monoterpene NOSs suggested their formation via the nighttime NO3-initiated oxidation of monoterpene under high-NOx conditions. However, isoprene NOSs are presumed to form via acid-catalyzed chemistry or reactive uptake of oxidation products of isoprene. This study provides direct observational evidence and highlights the secondary formation of OSs and NOSs via the interaction between biogenic precursors and anthropogenic pollutants (NOx, SO2, and SO42−). The results imply that future reduction in anthropogenic emissions can help to reduce the biogenic SOA burden in Beijing or other areas impacted by both biogenic emissions and anthropogenic pollutants.

Short summary
The overall characteristics and concentrations of organosulfates (OSs) and nitrooxy-OSs (NOSs) were determined in summer in Beijing. This study provided direct observational evidence that OSs form via acid-catalyzed aqueous-phase reactions in the presence of acidic sulfate aerosols, and monoterpene NOSs form via nighttime NO3 oxidation. Using OSs and NOSs as examples, this work highlights the formation pathways of SOA via anthropogenic–biogenic interactions and organic–inorganic reactions.
Final-revised paper