Atmos. Chem. Phys., 20, 6803–6820, 2020 https://doi.org/10.5194/acp-20-6803-2020 © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License. Molecular characterization of firework-related urban aerosols using Fourier transform ion cyclotron resonance mass spectrometry Qiaorong Xie1,8, Sihui Su2, Shuang Chen2, Yisheng Xu3, Dong Cao4, Jing Chen5, Lujie Ren2, Siyao Yue1,6,8, Wanyu Zhao1,8, Yele Sun1, Zifa Wang1, Haijie Tong6, Hang Su6, Yafang Cheng6, Kimitaka Kawamura7, Guibin Jiang4, Cong-Qiang Liu2, and Pingqing Fu2 1State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China 2Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China 3State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China 4State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085, China 5School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China 6Max Planck Institute for Chemistry, Multiphase Chemistry Department, Hahn-Meitner-Weg 1, 55128 Mainz, Germany 7Chubu Institute for Advanced Studies, Chubu University, Kasugai 487-8501, Japan 8College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China Correspondence: Pingqing Fu ([email protected]) Received: 20 December 2019 – Discussion started: 20 January 2020 Revised: 27 April 2020 – Accepted: 7 May 2020 – Published: 10 June 2020 Abstract. Firework (FW) emission has strong impacts on ticularly aromatic-like substances in urban particulate matter, air quality and public health. However, little is known about which may affect the light absorption properties and adverse the molecular composition of FW-related airborne particu- health effects of atmospheric aerosols. late matter (PM), especially the organic fraction. Here we describe the detailed molecular composition of Beijing PM collected before, during, and after a FW event in the evening of New Year’s Eve in 2012. Subgroups of CHO, CHON, and 1 Introduction CHOS were characterized using ultrahigh-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrom- The widespread haze pollution in China has aroused much at- etry. These subgroups comprise a substantial fraction of tention due to its strong impacts on air quality, human health, aromatic-like compounds with low O=C ratio and high de- and climate change (Ramanathan et al., 2001; Pöschl, 2005; grees of unsaturation, some of which plausibly contributed Lelieveld et al., 2015; Thomason et al., 2018; Kaufman et al., to the formation of brown carbon in Beijing PM. Moreover, 2002). The levels of haze pollution are strongly dependent we found that the number concentration of sulfur-containing on the source of haze particles, e.g., industry, coal combus- compounds, especially the organosulfates, increased dramat- tion, vehicle emissions, cooking, and biomass burning (Sun ically during the FW event, whereas the number concentra- et al., 2013; Zheng et al., 2005). Among different haze par- tion of CHO and CHON doubled after the event, which was ticle sources the firework (FW) emission can be expected to associated with multiple atmospheric aging processes includ- play an important role in urban air quality during festivals ing the multiphase redox chemistry driven by NOx,O3, and (Feng et al., 2012; Jing et al., 2014; Jiang et al., 2015; Tian et •OH. These findings highlight that FW emissions can lead to al., 2014). However, the chemical composition of FW-related a sharp increase in high-molecular-weight compounds, par- aerosols, especially the organic fraction, is not well charac- terized. Published by Copernicus Publications on behalf of the European Geosciences Union. 6804 Q. Xie et al.: Molecular characterization of firework-related urban aerosols There are a high number of pollutants released by FW the ultrahigh-resolution mass spectrometers (UHRMSs) with burning, such as sulfur dioxide, nitrogen oxide, volatile or- extremely high mass accuracy, has been successfully used ganic compounds, and particles comprising inorganic ma- to characterize complex organic mixtures of water-soluble terials (e.g., potassium and sulfate), and organic com- organic matter in urban aerosols (e.g., Ohno et al., 2016; pounds (e.g., n-alkanes and polycyclic aromatic hydrocar- Qi and O’Connor, 2014; Lin et al., 2012a; Wozniak et al., bons, PAHs) (Feng et al., 2012). They impose threats on 2008; Jiang et al., 2016; Mazzoleni et al., 2012; Kundu et human health (Sarkar et al., 2010) and can reduce visibil- al., 2012; Xie et al., 2020). However up to date, little is ity (Vecchi et al., 2008). Moreover, real-time chemical com- known about the detailed molecular information in firework- position measurements illustrated that FW-related organics related aerosols. FT-ICRMS can characterize compounds were mainly secondary organic material (Jiang et al., 2015). with molecular weight from 100 to 1000 Da, especially for Nonetheless, all those studies primarily focused on the inor- HMW compounds. Moreover, compounds containing nitro- ganic chemical species and relatively-low-molecular-weight gen, sulfur, and phosphorus atoms in the organic mixture can (LMW) organic compounds, while little is known about the be identified by FT-ICRMS with high resolution (Hawkes et molecular-level characterization of high-molecular-weight al., 2016). (HMW) organic compounds in urban aerosols during FW In this study, the molecular-level composition of HMW events, which contains important chemical composition in- organic compounds in urban aerosols collected in Beijing formation of aerosols. during the firework events of the traditional Chinese New Water-soluble organic carbon (WSOC) is a ubiquitous Year’s Eve and Spring Festival was investigated using a 15 T component of atmospheric aerosols. A large proportion of ultrahigh-resolution FT-ICRMS. The chemical composition water-soluble organic matter is composed of HMW or- and number concentrations of CHO, CHON, and CHOS sub- ganic compounds that contain a substantial fraction of het- groups in FW- and non-FW-related aerosols were mainly dis- eroatoms (N, S, O) (Lin et al., 2012a; Mazzoleni et al., cussed. In addition, the detailed molecular characteristics of 2012; Wozniak et al., 2008; Wang et al., 2016). Highly oxy- CHNOS species and their volatility using a molecular corri- genated molecules contain a wide range of chemical func- dor method will be present in another study. tional groups such as peroxides, hydroperoxides, carbonyls, and percarboxylic acids (Lee et al., 2019). Organic acids in oxygen-containing species contribute significantly to aerosol 2 Materials and methods acidity. Lots of nitro-aromatic compounds in relatively-high- 2.1 Aerosol sampling molecular-weight compounds, often observed in biomass burning aerosols, are potential contributors to light absorp- Total suspended particle (TSP) sampling was conducted on tion (Laskin et al., 2015; Lin et al., 2015). Moreover, the roof of a building (8 m above ground level) in the campus organosulfates substantially contribute to the secondary or- of the Institute of Atmospheric Physics, Chinese Academy of ganic aerosol (SOA) mass (Tolocka and Turpin, 2012), which Sciences (39◦5802800 N, 116◦2201300 E), a representative ur- plays an important role in exploring the formation pathway ban site in the central north part of Beijing. TSP samples of SOA (Shang et al., 2016; Riva et al., 2015, 2016; Pas- were collected on a 12 h basis from 21 to 23 January 2012 sananti et al., 2016). Meanwhile, because of their polar and (i.e., sample ID: New Year’s Eve daytime, NYE D, before hydrophilic nature, organosulfates can influence the hygro- the FW event; New Year’s Eve nighttime, NYE N, during scopic properties of aerosols (Estillore et al., 2016). Hence, the FW event; Lunar New Year’s Day daytime, LNY D, af- characterizing both the compound class and individual com- ter the FW event; Lunar New Year’s Day nighttime, LNY pound level of organic aerosols (OAs) is important for ex- N), including episodes of short-term pollution raised by FW ploring the formation mechanisms, physicochemical proper- emissions. Detailed sample information is shown in Table 1. ties, and environmental effects of firework-related aerosols. The 48 h clustering air mass trajectories (Fig. S1 in the Sup- Moreover, the large amount of firework emission is an ideal plement) show that all of them mainly originated from the event to understand the contribution of anthropogenic pre- northwest. All aerosol and field blank samples were collected cursors to the formation of organic aerosols. using a high-volume air sampler (Kimoto, Japan) with pre- A molecular-level characterization of chemical con- combusted (6 h in 450 ◦C in a muffle furnace) quartz filters stituents in firework-related aerosols is challenging because (20cm×25cm, Pallflex). After the sampling, the filters were of their highly chemical complexity with vast numbers of stored in a refrigerator at −20 ◦C until analysis. compounds. Less than 10 %–20 % of water-soluble organ- ics, limited to LMW, can be characterized at a molecular 2.2 Chemical component analysis level by a combination of gas chromatography–mass spec- trometry (GC-MS) (Wang et al., 2006), ion chromatogra- One punch