Non-Target Screening of Organic Pollutants and Target Analysis of Halogenated Polycyclic Aromatic Hydrocarbons in the Atmosphere

Yang et al. Environ Sci Eur (2020) 32:96 https://doi.org/10.1186/s12302-020-00376-9

RESEARCH Open Access Non‑target screening of organic pollutants and target analysis of halogenated polycyclic aromatic hydrocarbons in the atmosphere around metallurgical plants by high‑resolution GC/Q‑TOF‑MS Lili Yang1, Jiajia Wu2, Minghui Zheng1,3, Zhe Cao2, Cui Li1, Miwei Shi4 and Guorui Liu1,3*

Abstract Background: The 16 priority polycyclic aromatic hydrocarbons (PAHs) issued by US Environmental protection agency are a major focus in atmosphere in previous studies. Many more PAH congeners or their substitutes could be produced during combustion or thermal industrial processes and released into the atmosphere. However, a full screening of various organic pollutants in air surrounding important industrial sources has not been conducted. Identifying and characterizing organic pollutants in air is essential for accurate risk assessment. This study conducted non-target screening of organic pollutants and simultaneous target analysis of emerging contaminants including 8 polychlorinated naphthalenes and 30 higher cyclic halogenated PAHs by high-resolution gas chromatography quadrupole time- of-fight mass spectrometry (GC/Q-TOF-MS) and applied to the air samples collected surrounding metallurgical plants. Emerging organic chemicals of high toxicity in air were identifed. Results: We identifed and characterized 187 organic chemicals categorized as PAHs, alkylated polycyclic aromatic compounds (PACs), heterocyclic PACs, and aliphatic hydrocarbons in atmosphere around industrial sources. Some of these identifed chemicals, such as phthalic acid esters, dimethylbenz[a]anthracene, and hydroquinone with alkane substituents are of potential high toxicities and have not been the focus of previous studies of airborne contaminants. Moreover, hydroquinone with alkane substituents may be critical intermediates and precursors of an emerging contaminant—environmentally persistent free radicals. Thus, the presence of those identifed highly toxic chemicals in the air merits attention. Moreover, 38 chlorinated and brominated PAHs as target compounds were accurately quantitated by using isotopic dilution method by application of GC/Q-TOF-MS, and the fndings were similar to those of high-resolution magnetic mass spectrometry. Conclusion: In this study, both non-target screening of organic pollutants and target analysis of halogenated PAHs in air were achieved by GC/Q-TOF-MS. The method could be of signifcance for simultaneous analysis of those trace pollutants containing multiple congeners. Specifc pollutants of potential high toxicity in atmosphere around industrial

*Correspondence: [email protected] 1 State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco‑Environmental Science, Chinese Academy of Sciences, Beijing 100085, China Full list of author information is available at the end of the article

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sources were identifed. Those knowledge could be helpful for comprehensively recognizing the organic contaminants in air surrounding metallurgical plants and better understanding their potential health risks. Keywords: Halogenated polycyclic aromatic hydrocarbons, Persistent organic pollutants, GC/Q-TOF-MS, Air pollutants, Environmentally persistent free radicals

Background widely applied method currently [14]. GC × GC/TOF- Te 16 priority polycyclic aromatic hydrocarbons (PAHs) MS or Fourier transform ion cyclotron resonance mass issued by US Environmental protection agency (EPA) are spectrometry has been applied for non-target analysis a major focus of eforts to assess the risks of pollutants in of soil and biota samples, and high levels of several halo- atmosphere to human health [1]. However, besides the 16 genated PAH congeners were detected [14]. Besides the priority PAHs, much more PAH congeners or their sub- well-known dioxins and PAHs, it is believed that numer- stitutes are also produced during combustion or thermal ous other toxic organic pollutants could simultaneously industrial processes and released into the atmosphere [2]. be formed during the metallurgical processes. However, Taking polychlorinated naphthalenes (PCNs) as an exam- comprehensive recognition of the pollutant components ple, they can be unintentionally produced and emitted to in environment surrounding the industrial sources was the air. PCNs are on the list of persistent organic pollut- still unknown. Screening of more organic pollutants such ants (POPs) covered under the Stockholm Convention as PAH congeners and their substitutes should be con- because of their toxicity, persistence, bio-accumulation, ducted for better understanding the potential impact of and long-range transport in the environment [3, 4]. Halo- source emissions on surrounding environment. High-res- genated PAHs, which exert similarly toxic efects, can olution GC quadrupole time-of-fight (GC/Q-TOF-MS) also be formed during activities such as incineration of mass spectrometry has great potential for the non-target municipal solid waste and secondary copper smelting [5, analysis of GC-amenable compounds. Te same full- 6]. Chlorinated and brominated PAHs (Cl/Br-PAHs) with spectrum accurate mass data enable both quantitation three to fve rings are considered more toxic than their of priority targets and reliable screening of more com- parent chemicals [7–9]. Tose less focused PAH conge- pounds, especially those present in trace amounts. ners or their substitutes might be important pollutants In this study, we developed a high-resolution GC/Q- or precursors for highly toxic air contaminants. Tere- TOF-MS method to comprehensively measure and iden- fore, pollutants of high concentrations and toxicities in tify organic pollutants such as PAHs, alkylated polycyclic atmosphere need to be recognized and further intensive aromatic compounds (PACs), heterocyclic PACs in air. studied. Novel PACs of high toxicity and concentrations in the Metallurgical plants have been identifed to be impor- air samples will be identifed and focused with the aim tant sources of unintentional POPs, and can release trace of obtaining comprehensive overview of various organic levels but carcinogenic polychlorinated dibenzo-p-diox- chemicals in the air surrounding the metallurgical plants. ins and dibenzofurans, polychlorinated biphenyls, and We also conducted a simultaneous analysis of targeted PAHs [10, 11]. Incomplete combustion of the organic halogenated PAHs including PCNs regulated by the residues, such as cables, paint and heavy oil in the raw Stockholm Convention by GC/Q-TOF-MS. Te method materials used for metallurgical plants and the formation by application of GC/Q-TOF-MS could be useful for during cooling stage of fue gas is the inherent cause for simultaneous analysis of those trace pollutants contain- toxic pollutant emissions [12, 13]. Studies characterizing ing multiple congeners. Te knowledge obtained in this and measuring the levels of these dioxins and dioxin-like study could be helpful for recognizing and characterizing compounds of trace levels in the environment surround- the organic contamination in air and better understanding metallurgical plants have been widely conducted by ing their potential health risks. gas chromatography coupled with magnetic sector high- resolution mass spectrometry (GC–HRMS) for the accu- Methods and materials rate qualifcation and quantifcation [14, 15]. GC–HRMS Air samples were collected from an area surround- is typically run in selected ion monitoring mode to ing metallurgical plants including iron ore sintering achieve high sensitivity and selectivity, meeting the ana- plants and steel-making plants by high-volume air sam- lytical requirements of trace levels of specifc POPs in air plers (Echo Hi-Vol, Tecora, Milan, Italy) at a fow rate [8, 10, 11, 16]. GC/MS, GC/MS/MS and GC/HRMS have of 0.24 m3/min for 24 h, according to US EPA method been used for the analysis of halogenated PAHs, among TO-9A. Te air volume was approximately 1000 m3. which GC/HRMS in selected ion mode is the most Cleaned quartz fber flters (102 mm diameter, baked in Yang et al. Environ Sci Eur (2020) 32:96 Page 3 of 14

mufe furnace at 450 °C for 6 h) and polyurethane foam Target analysis of the 38 Cl/Br-PAHs, including eight (63 mm diameter, 76 mm length, purifed by accelerated PCNs congeners and 30 Cl/Br-PAHs congeners, were solvent extraction with acetone and hexane) were used conducted using isotope dilution GC/Q-TOF-MS. Te to gather particle phase and gas phase of the air samples, compounds were measured by calibration curves with respectively. Te collected air samples were wrapped with 13C-labeled compounds as internal standards (shown in aluminum foil and retained in polyethylene valve bags. Tables 1 and 2). Most calibration concentrations were Prior to extraction, the samples were spiked with labeled 5–800 ng/mL. Te lowest level of calibration solution standards (2 ng of a mixture of three PAHs, 2 ng of a mix- (5 ng/mL) was sequentially injected eight times and the ture of six halogenated PAHs and 2 ng of a mixture of six RSDs of almost all congeners ranged from 2.0 to 14.4%, PCNs) for target analysis of halogenated PAHs. Te spike all below 15% over the range. Te signal-to-noise ratios of label internal standards into the samples was used for of these congeners at the lowest concentration in the cali- accurate qualifcation and quantifcation of target com- bration curve were all > 10. Tese calibration curves were pounds. Moreover, the labeled internal standards could used to quantitate the target Cl/Br-PAHs congeners in be helpful for preliminarily estimating the relative abun- the air samples. Relative response factors (RRFs) equa- dance of non-target compounds by comparing their peak tion was used and measured for accurate quantifcation areas with that of labeled internal standards. Te signal- of the target congeners on the basis of the Method 1613 to-noise ratio and the recoveries of labeled standards can developed by the United States Environmental Protec- meet the accurate identifcation of target compounds tion Agency for dioxins: and the semi-quantifcation of non-target chemicals. Te (A1x + A2x)C1 samples were extracted by accelerated solvent extrac- RRF = , (A11 + A21)Cx (1) tion with dichloromethane and hexane (1:1). Te extraction solution was concentrated and then cleaned using where A1 and A2 are the peak areas of quantitative and an activated silica gel column [14]. Te sample solution x x qualitative ion of target congeners, respectively; A1 and was then concentrated by rotary evaporator and nitrogen 1 A2 are the peak areas of quantitative and qualitative ion gas and the elution was concentrated to approximately 1 of 13C-labeled internal standard, respectively; C and 20 μL. Fly ashes from the metallurgical plants were also x C are concentration of target congeners and the cor- collected and analyzed by gas chromatography–Orbitrap 1 responding 13C-labeled internal standard (pg/m3). Te mass spectrometry in our previous studies [6]. Te non- RRFs ranged from 1.21 to 1.65, and the variable deviation target screening results were compared between that in ranged from 8.3 to 14.6%. air samples and in fy ashes samples to show their diferent distribution characteristics. Data were acquired using an Agilent 7890B GC instru- Results and discussion ment coupled to an Agilent 7250 high-resolution Q-TOF- General characteristics of organic pollutants in air MS platform equipped with a multimode inlet (Agilent Target priority PAHs were quantifed using a calibration Technologies, Santa Clara, CA, USA). Te electron ioni- curve with labeled internal standards. Te concentrations zation full-spectrum mode of the GC/Q-TOF-MS system of target priority PAHs ranged from 0.12 to 101.2 pg/m3. enabled target and non-target acquisition using the same We used SureMass signal processing of GC/Q-TOF-MS method. Te resolution of the mass analyzer was set data to deconvolute the components and MassHunter at > 25,000 (full width at half maximum) at m/z 271.9867. Unknowns Analysis software to identify untargeted A DB-5 ms UI (60 m–0.25 mm–0.25 μm) column was PAHs to briefy understand the components of pollutants used to separate all targeted and untargeted chemicals. in the air surrounding industries. Compounds were iden- Additional fle 1: Table S1 lists the detail parameters of tifed and verifed via the NIST17 library using the exact analytical settings. Te data were acquired and processed mass of the molecular ion or characteristic fragments using MassHunter Qualitative Analysis (version B.08.00) (mass error < 10 ppm) and isotopic distribution as the cri- and Quantitative Analysis (version B.09.00) software teria parameters. Figure 1 shows an example compound, (Agilent Technologies). Unknowns Analysis software 9H-fuorene, 9-methylene-. Altogether, we identifed (version B.09.00) with the SureMass deconvolution algo- and verifed 187 organic chemicals using GC/Q-TOF- rithm, on the basis of the exact mass number, was used MS. Among these organic chemicals, 146 were aromatic for non-target analysis. Initial compound identifcation hydrocarbons (Table 1) and 41 were aliphatic hydrocar- was performed by spectrum comparison with data from bons (Additional fle 1: Table S2). the NIST17 EI library. Hexane solution was analyzed by Fly ashes are considered to be important matrix for the same methods as a solvent blank to exclude interfer- catalyzing the organic pollutant formations during ther- ences from systematic errors. mochemical processes. General characteristics of organic Yang et al. Environ Sci Eur (2020) 32:96 Page 4 of 14 4944 12,258 39,736 50,960 13,573 88,147 28,579 10,978 509,329 233,150 335,917 801,787 867,951 142,691 787,979 373,719 156,776 455,096 161,426 199,615 266,527 194,982 904,262 122,621 388,473 737,656 122,980 171,996 1,601,379 1,436,278 Area 4 2 3 O O O O O O 12 18 12 12 16 12 12 12 18 12 12 16 12 18 14 14 20 42 14 12 10 14 16 24 10 12 12 12 10 16 H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H 17 18 17 17 17 17 17 17 9 18 17 17 18 17 18 18 18 19 22 18 18 18 18 19 24 18 18 18 18 18 C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C Formula 68.6 95.0 90.4 65.2 83.5 84.0 94.0 75.4 72.1 95.7 90.0 72.5 65.7 67.3 68.4 81.7 94.2 67.9 75.4 87.5 74.2 94.1 81.8 66.0 82.4 81.0 66.3 96.6 87.2 84.1 Match factorMatch - thenyl)- oxy]- ethynyl]- ester Pyrene, dimethyl- Pyrene, Pyrene, methyl- Pyrene, Cyclopenta[cd]pyrene Naphthalene, (methyl-phenyle Naphthalene, triphenyl- Cyclohexane, Isopropyl-methylphenanthrene Benzo[b]fuorene Benzo[b]fuorene Ethyl-methylanthracene Benzo[b]fuorene Phenanthro[b]pyran [(tetrahydro-pyran-yl) Butanal, methyl-[(propylphenyl) Benzene, Azulene, dimethyl-phenyl- dimethyl- Pyrene, Cyclopenta[cd]pyrene Pyrene, methyl- Pyrene, Phenanthro[b]pyran Isopropyl-dimethylphenanthrene bis(ethylhexyl) Hexanedioic acid, dimethyl- Pyrene, Triphenylene Benzo[b]fuorene Isopropyl-methylphenanthrene Pyrene, methyl- Pyrene, Cyclopenta(cd)pyrene, dihydro- Cyclopenta(cd)pyrene, Bicyclohex-en-one, diphenyl- Triphenylene Benzo[c]phenanthrene b’]bisbenzofuran Benzo[b: Name 41.528 37.895 44.623 43.817 44.058 36.954 37.061 37.391 37.635 37.667 38.066 38.133 38.248 39.290 41.002 43.149 38.961 39.490 42.133 42.163 42.227 44.800 36.878 40.152 38.685 42.903 43.189 45.088 44.973 45.481 Retention time Retention 89 79 98 96 97 74 75 76 77 78 80 81 82 85 88 94 84 86 90 91 92 99 73 87 83 93 95 101 100 102 No. 5510 54,297 90,325 68,883 77,767 92,301 85,943 99,806 68,935 58,051 75,251 141,601 369,692 360,672 180,355 253,558 239,308 205,121 154,350 105,858 126,399 122,059 111,953 238,035 364,045 116,949 405,710 578,874 412,765 159,814 Area S 4 3 4 4 O O O O O O O O O O 8 8 10 10 10 10 12 12 10 12 8 12 12 8 14 14 14 14 10 16 10 10 10 16 18 12 12 10 8 10 H H H H H H H H H H H H H H H H H H H H H H H H H H H H D D 10 12 11 11 12 12 12 12 12 12 12 13 13 12 13 13 13 12 13 15 13 13 13 14 14 14 14 10 10 12 C C C C Formula C C C C C C C C C C C C C C C C C C C C C C C C C C 91.3 91.2 90.9 84.8 Match factorMatch 86.3 91.9 96.1 73.0 91.8 92.5 78.2 75.2 74.5 94.9 86.5 86.4 89.7 78.9 78.4 66.5 77.0 66.8 95.3 83.5 66.1 89.7 92.3 66.9 88.7 89.6 (standard) 10 (standard) 8 tetrahydrocyclohepta[de] ester naphthalen-8-yl phenyl- Acenaphthene-D Xanthene and isomers Xanthene Naphthalene, dimethyl- Naphthalene, Name Naphthalene, trimethyl- Naphthalene, methyl- Fluorene, Naphthalene Acenaphthylene methyl- Naphthalene, Biphenyl ether Diphenyl dimethyl- Naphthalene, ethenyl- Naphthalene, Acenaphthylene methyl- Biphenyl, Dibenzofuran trimethyl- Naphthalene, trimethyl- Naphthalene, Phenalene acid, Methanesulfonic and isomers Xanthene Tetramethylnaphthalene pentylMethyl phthalate Naphthalene, dimethyl- Naphthalene, Isopropenylnaphthalene Phthalate Diethyl and isomers Xanthene (methylphenyl) Methanone, Naphthalene, methyl- Naphthalene, Dimethyl phthalate Dimethyl Naphthalene-D Aromatic hydrocarbons in air samples screened by gas chromatography quadrupole time-of-fight mass spectrometry chromatography by gas in air samples screened hydrocarbons Aromatic 8.565 8.611 13.812 17.433 12.499 Retention time Retention 15.463 20.023 10.065 10.156 11.524 11.874 12.103 12.642 13.215 13.704 14.750 14.938 15.325 16.517 16.992 18.184 19.369 19.525 12.853 13.956 15.883 17.892 19.949 10.434 12.533 22 8 1 Table No. 18 28 1 2 3 5 6 7 10 12 13 15 16 17 20 21 24 25 26 11 14 19 23 27 4 9 Yang et al. Environ Sci Eur (2020) 32:96 Page 5 of 14 15,144 26,160 51,069 15,568 19,493 97,032 197,331 161,256 322,065 226,719 111,193 116,789 171,678 346,092 250,792 232,886 185,894 197,814 238,148 121,290 169,928 178,610 574,992 329,204 880,538 959,816 254,272 127,870 279,212 447,400 1,969,873 1,465,392 Area 4 4 4 O O O O O O O O 38 30 10 14 14 14 14 14 12 12 14 14 12 14 14 14 16 16 38 12 12 12 12 12 12 12 12 12 12 18 14 46 H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H 24 20 18 19 19 19 19 19 19 19 20 19 19 20 20 20 20 20 24 20 20 20 20 20 20 20 20 20 20 24 21 27 C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C Formula 81.0 80.9 80.2 80.0 80.3 82.2 79.6 93.7 81.5 83.5 85.6 73.7 68.2 92.0 95.2 94.2 77.5 88.8 79.8 88.7 85.0 71.8 67.2 92.0 85.4 73.5 84.3 78.0 93.8 72.0 74.4 72.2 Match factorMatch bis(ethylhexyl) ester bis(ethylhexyl) Tribenzo[a,c,e]cycloheptene Cyclopenta[a]pyrene Phthalic acid, di(hex-yl) ester di(hex-yl) acid, Phthalic Naphtho[klmn]xanthene Tribenzo[a,c,e]cycloheptene Binaphthalene Benzo[a]pyrene Perylene Chrysene, methyl- Binaphthalene phenyl- Phenanthrene, dihydro- Benzenoanthracene, dimethyl- Benz[a]anthracene, Benzenedicarboxylic acid, Benzo[e]pyrene Benzo[e]pyrene Dinaphtho[b: d]furan Dinaphtho[b: d]furan Dinaphtho[b: d]furan Benzo[a]pyrene phenyl- Terphenyl, Alpha.H-Trisnorhopane Chrysene, methyl- Tribenzo[a,c,e]cycloheptene Cyclopenta[a]pyrene methyl- Benz[a]anthracene, Cyclopenta[a]pyrene dimethyl- Benz[a]anthracene, Benzo[e]pyrene Dinaphtho[b: d]furan Indeno[b]phenanthrene Bis(ethylhexyl) phthalate Bis(ethylhexyl) Name 47.679 48.958 46.477 46.724 48.110 49.054 52.368 54.136 48.195 49.514 49.835 50.664 51.042 51.342 52.528 52.922 53.491 53.584 53.906 54.605 55.341 56.189 47.958 48.431 48.752 49.097 49.123 51.253 53.856 54.499 55.557 46.468 Retention time Retention 106 112 104 105 108 113 122 129 109 116 117 118 119 121 123 124 125 126 128 131 132 134 107 110 111 114 115 120 127 130 133 103 No. 73,506 50,813 85,131 96,433 18,604 43,955 24,320 59,763 247,131 129,680 277,626 163,081 139,556 354,107 340,666 506,636 161,893 407,602 357,052 375,666 108,908 128,812 263,619 330,800 137,771 566,651 113,988 174,927 2,571,463 2,801,977 2,996,424 2,476,032 Area 3 3 4 4 4 O O O O O O O S N 12 12 8 10 10 14 14 9 22 12 20 12 12 12 10 12 12 22 12 14 14 12 14 14 10 14 14 10 14 10 12 10 H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H D 14 14 12 14 14 11 11 12 16 16 15 15 15 15 15 15 15 16 16 16 16 16 16 16 16 16 17 16 17 16 14 14 C C C C C C C Formula C C C C C C C C C C C C C C C C C C C C C C C C C 76.5 91.2 76.8 68.2 70.2 75.9 93.5 Match factorMatch 69.6 94.7 66.4 94.2 68.1 88.1 94.9 89.8 76.6 92.6 94.1 89.7 93.0 82.1 71.4 71.0 80.8 92.6 79.8 73.9 95.3 68.5 90.5 74.4 80.0 (standard) 10 bis(methylpropyl) ester bis(methylpropyl) Phenanthrene-D Naphthalene, phenylmethyl- Naphthalene, Dibenzothiophene phenyl- Naphthalene, ethyl- Phenanthrene, Fluoranthene Name Phenol, (phenylethenyl)-, (E)- (phenylethenyl)-, Phenol, Dibutyl phthalate Naphthofuran, dimethyl- methylene- Fluorene, Acetyl-trimethylhydroquinone Carbazole Benzenedicarboxylic acid, Indene, phenylmethylene- butyl isoporpyl acid, ester Phthalic Indene, phenylmethyl- Phenanthrene, Indene, phenylmethyl- Phenanthrene, dimethyl- Phenanthrene, dimethyl- Phenanthrene, tetrahydro- Pyrene, dimethyl- Phenanthrene, Fluoranthene phenylmethyl- Naphthalene, Fluoranthene Diphenylacetylene Acetyl-trimethylhydroquinone Cyclobuta[jk]phenanthrene methyl- Anthracene, Indene, phenylmethylene- Fluorene, methyl- Fluorene, (continued) 22.448 32.550 21.722 31.123 31.373 32.081 Retention time Retention 21.520 27.624 20.777 23.001 23.793 24.255 24.355 24.868 25.966 26.331 26.540 26.905 27.352 30.091 30.311 31.618 32.241 32.878 33.140 33.519 22.616 23.721 27.109 27.138 28.863 20.384 56 32 51 52 54 1 Table No. 31 47 30 34 36 37 38 39 40 41 42 43 46 49 50 53 55 57 58 59 33 35 44 45 48 29 Yang et al. Environ Sci Eur (2020) 32:96 Page 6 of 14 13,213 80,372 491,043 237,254 102,004 169,077 376,094 933,981 277,114 155,782 982,552 134,744 Area 2 2 O O 2 2 N N O 12 12 12 22 12 12 14 14 14 12 14 14 H H H H H H H H H H H H 16 16 22 14 22 22 22 22 22 22 23 23 C C C C C C C C C C C C Formula 70.4 73.8 90.3 80.0 70.3 75.0 91.1 86.5 74.8 84.7 65.6 83.1 Match factorMatch dihydropyrimidine -dihydropyrimidine Oxo-phenyl- (hydroxyphenyl)- (hydroxyphenyl)- Oxo-phenyl- Beta.-iso-Methyl ionone Benzo[ghi]perylene Pentacene Dibenz[a,j]anthracene Oxo-phenyl-(hydroxyphenyl) Oxo-phenyl-(hydroxyphenyl) Benzo[ghi]perylene Benzo[ghi]perylene Benzo[ghi]perylene, methyl- Benzo[ghi]perylene, methyl- Benzo[ghi]perylene Pentacene Name 57.722 60.185 60.457 61.357 62.314 57.038 61.129 63.013 64.809 66.526 59.799 62.064 Retention time Retention 136 138 139 141 143 135 140 144 145 146 137 142 No. 78,418 98,062 505,271 397,033 207,966 497,015 256,306 332,863 308,803 143,602 131,081 135,890 2,015,556 Area 2 4 O O O O O O O 10 16 10 14 16 10 16 10 12 22 16 12 10 H H H H H H H H H H H H H 16 17 16 19 17 16 17 16 17 22 17 17 16 C Formula C C C C C C C C C C C C 65.6 Match factorMatch 89.8 68.0 87.0 76.7 91.0 77.4 86.3 75.0 82.6 78.0 78.1 93.4 methyl-phenyl-naphthalenyl)-, methyl-phenyl-naphthalenyl)-, ester dimethyl Pentadiyn-one, bis(methylphenyl)- Pentadiyn-one, Name Benzo[b]naphtho[d]furan Diacetyldiphenylmethane Benzo[kl]xanthene Ethyl-methylanthracene Benzo[b]naphtho[d]furan Ethyl-methylanthracene Benzo[kl]xanthene (dihydro- acid, Propanedioic Benzo[b]fuorene Benzanthrene trimethyl- Phenanthrene, Fluoranthene (continued) 34.771 Retention time Retention 34.015 34.082 34.580 34.902 35.217 35.406 35.902 36.224 36.805 36.160 36.436 33.947 64 1 Table No. 61 62 63 65 66 67 68 70 72 69 71 60 Yang et al. Environ Sci Eur (2020) 32:96 Page 7 of 14

Table 2 Quantitative method performance for chlorinated and brominated polycyclic aromatic hydrocarbons Compound name Retention time/ Quantitative ion Qualitative ion Internal standard LOQ/pg/μL min (ISTD)

Polychlorinated naphthene (Nap) 2-Cl-Nap 11.66 162.0231 164.0202 ISTD 1 3.0 1,5-diCl-Nap 15.96 195.9841 197.9812 ISTD 1 3.5 1,2,3-TriCl-Nap 22.38 229.9451 231.9422 ISTD 1 2.6 1,2,3,5-TetraCl-Nap 27.81 265.9033 263.9062 ISTD 2 2.1 1,2,3,5,7-PentaCl-Nap 32.47 299.8643 301.8614 ISTD 3 2.4 1,2,3,4,6,7-HexaCl-Nap 39.94 333.8253 335.8224 ISTD 4 2.7 1,2,3,4,5,6,7-HeptaCl-Nap 47.91 367.7863 365.7892 ISTD 5 3.5 OctaCl-Nap 52.92 403.7444 401.7473 ISTD 6 5.0 ISTD 1_1,3,5,7-TetraCl-Nap-13C 24.92 275.9368 273.9397 ISTD 2_1,2,3,4-TetraCl-Nap-13C 28.39 275.9368 273.9397 ISTD 3_1,2,3,5,7-PentaCl-Nap-13C 32.45 309.8978 311.8948 ISTD 4_1,2,3,5,6,7-HexaCl-Nap-13C 39.98 343.8588 345.8559 ISTD 5_1,2,3,4,5,6,7-HeptaCl-Nap-13C 47.90 377.8199 379.8169 ISTD 6_OctaCl-Nap-13C 52.92 413.7779 411.7809 5-Bromoacenapthene 23.54 231.9882 233.9862 ISTD 7 2.1 2-Bromofuorene 26.74 243.9882 245.9862 ISTD 7 2.9 3-Chlorophenanthrene 29.29 212.0389 214.0358 ISTD 7 1.6 2/9-Chlorophenanthrene 29.59 212.0389 214.0358 ISTD 7 1.0 1-Chloroanthracene 29.59 212.0389 214.0358 ISTD 8 1.5 2-Chloroanthracene 30.01 212.0389 214.0358 ISTD 8 3.3 2,7-2 Chlorofuorene 30.62 233.9998 235.9968 ISTD 8 2.3 1,2-Dibromoacenaphthylene 30.70 309.8811 307.8831 ISTD 8 4.2 3-Bromophenanthrene 33.06 257.9867 255.9883 ISTD 9 2.7 9-Bromophenanthrene 33.47 257.9867 255.9883 ISTD 9 3.3 2-Bromophenanthrene 33.47 257.9867 255.9883 ISTD 9 4.7 1-Bromoanthracene 33.70 257.9867 255.9883 ISTD 9 3.8 9-Bromoanthracene 34.02 257.9867 255.9883 ISTD 9 3.9 1,4-Dichloroanthracene 36.08 245.9998 247.9968 ISTD 9 1.5 1,5/9,10-Dichloroanthracene 36.59 245.9998 247.9968 ISTD 9 2.6 9,10-Dichlorophenanthrene 37.07 245.9998 247.9968 ISTD 9 2.8 2,7-Dibromofuorene 38.37 323.8967 325.8947 ISTD 9 2.9 3-Bromofuoranthene 42.99 279.9883 281.9862 ISTD 10 2.7 1,8/1,5-Dibromoanthracene 43.94 335.8967 337.8947 ISTD 10 3.6 9,10-Dibromoanthracene 44.31 335.8967 337.8947 ISTD 10 3.2 4-Bromopyrene 44.80 279.9883 281.9862 ISTD 10 3.9 9,10-Dibromophenanthrene 44.87 335.8967 337.8947 ISTD 10 2.9 1-Bromopyrene 45.02 279.9883 281.9862 ISTD 10 2.3 3,8-Dichlorofuoranthene 46.03 269.9998 271.9969 ISTD 10 4.5 1,5,9,10-Tetrachloroanthracene 51.35 315.9189 313.9218 ISTD 11 4.5 2-Bromotriphenylene 52.81 306.0039 308.0019 ISTD 12 4.0 1,6-Dibromopyrene 53.21 359.8967 361.8947 ISTD 12 4.5 6-Chlorobenzo[a]pyrene 59.39 286.0544 288.0515 ISTD 12 7.2 ISTD 7_9-Chlorophenanthrene-13C 29.56 218.0589 220.0559 ISTD 8_2-Chloroanthracene-13C 30.01 218.0589 220.0559

ISTD 9_9-Bromophenanthrene-D9 33.20 265.0447 267.0427 ISTD 10_1-Chloropyrene-13C 41.16 242.0589 244.0559 ISTD 11_7-Chlorobenz[a]anthracene-13C 50.63 268.0745 270.0716 ISTD 12_7-Bromobenz[a]anthracene-13C 53.23 312.0240 314.0220 Yang et al. Environ Sci Eur (2020) 32:96 Page 8 of 14

subcooled vapor pressure and lower koa from multiple industries might release into the air. Tose pollutants of high subcooled vapor pressure and toxicity should be focused during the disposal of fy ash. Normal distribution test of subcooled vapor pressure of pollutants in air and fy ashes were also conducted (Fig. 2c). Results showed that the subcooled vapor pressure of pollutants in the air ft the lognormal distribution pattern, indicating the multiple infuence factors on the pollutants in the air. Pollutants in air originated from numerous sources, but the pollutants in fy ashes were relatively simple due to high-temperature combustion processes. Tis might contribute to the abnormal distribution of the organic pollutants in fy ashes. It was suggested that the pollutants with relatively higher subcooled vapor pressure and lower log koa in the fy ashes need to be concerned because their potential adverse impacts on the air pollutions.

Aromatic hydrocarbons in air by non‑target analysis of GC/Q‑TOF‑MS Most of the 16 priority PAHs were detected in the air Fig. 1 Example of deconvolution function for samples surrounding industrial sources. Fluoranthene 9-methylene-9H-fuorene (CAS: 4425-82-5) detected by gas was a major contributor to the atmospheric PAH burden, chromatography quadrupole time-of-fight mass spectrometry. a and its peak areas accounted for 59% of the total peak Co-elution plot of frst fve main deconvoluted fragment ions in an air sample. b The mass spectra after deconvolution. c NIST spectrum areas of the 16 PAHs. A similar fnding was also found for 9-methylene-9H-fuorene. The match factor was calculated by by the comparison of PAHs in diferent areas in India, MassHunter Unknown Analysis software (Agilent Technologies) and the results showed that fuoranthene in the industrial sites was signifcantly higher than those in commer- cial sites [17]. Other studies concluded that atmospheric fuoranthene concentrations may have sources other pollutants in air were summarized and compared to that than motor vehicles [18, 19]. Fluoranthene may there- in fy ashes [6]. As shown in Fig. 2, the compound com- fore be considered an important indicator of indus- position of air and the fy ash were diferent, and pollut- trial emissions. Higher molecular weight parent PAHs ants in air are more diverse than that in fy ash samples. such as benzo[ghi]perylene, triphenylene, perylene, and Comparison between the screening results of air samples benzo[a]pyrene was also abundant in the samples, and and fy ash samples from industrial sources showed that these compounds are typically formed via combustion aliphatic hydrocarbons are more abundant in air. Few at elevated temperatures [20]. Te results are diferent aliphatic hydrocarbons have been reported in fy ash from the PAHs dominance in the air from residential from industrial sources [6]. Halogenated PACs are eas- areas [21], indicating the remarkable infuence of pyro- ily released from industrial activities [6], but PAHs and genic processes on the surrounding air of thermal indus- alkylated or heterocyclic PACs are more common in air tries. Benzo[a]pyrene was reported to be photo-reactive samples. Physical properties including subcooled vapor and thus unstable in air. Benzo[a]pyrene cannot undergo pressure and log koa of the contaminants in air were pre- long distance migration and is normally in relatively low dicted in this study and compared to the pollutants in the abundance in air samples [22]. Terefore, detection of fy ash samples from multiple industries reported in our benzo[a]pyrene in air can be used as an indicator of emis- previous studies [6]. Even though pollutants in air were sions from local sources. Perylene was confrmed to be much more numerous than that in fy ash, the deviation dominant precursor of PCNs during combustion or other degree of the physical properties was smaller for pollut- industrial thermal processes [23, 24]. Terefore, these ants in air than that in fy ashes (shown in Fig. 2). Te parent PAHs with high levels in air surrounding thermal deviation degree of pollutants in fy ashes were greater industries need further attention. than that in air, most of which were of higher subcooled Chemical substitution in PAH molecules can substan- vapor pressure and lower log koa than that of pollutants tially afect their carcinogenic potential [25]. However, in air. Terefore, some pollutants in fy ashes with higher PAH derivatives in the environment have been studied Yang et al. Environ Sci Eur (2020) 32:96 Page 9 of 14

a b a o gk lo

Average value of log subcooled VP: -4.29; Average value of log subcooled VP: -3.47; Standard deviation: 1.52 Standard deviation: 2.08 y y Frequenc Frequenc

log subcooled VP of pollutants in air log subcooled VP of pollutants in fly ashes

Fig. 2 Properties including a subcooled vapor pressure (VP), b log koa of pollutants in air and fy ash samples and the c normal distribution test of log subcooled VP

less than the 16 priority pollutants. We have detected benz[a]pyrene. 7,12-Dimethylbenz[a]anthracene, whose multiple novel aromatic hydrocarbons and substitutes toxic equivalency factor was reported to be 20 times of the 16 PAHs such as isopropyl-methylphenanthrene, that of its parent and twice that of benzo[a]pyrene [2], methylphenanthrene, and ethyl-methylanthracene. Some but this compound is typically ignored in routine tests PAH derivatives, including methyl-, dimethyl-, trime- of PAHs in air samples. Dimethylbenzo[a]anthracene thyl-, tetramethyl-, and ethenyl- substitutes, may be was screened out in this study, even though the methyl more toxic than their parent compounds and contribute substitution position cannot be elucidated according to a large part of toxicity of the atmospheric pollutants [2]. the screening result, alkyl derivatives of PAHs such as Toxicities of several novel PAH derivatives were calcu- 7,12-dimethylbenzo[a]anthracene in the air need further lated and shown in Additional fle 1: Table S3. Chemical attention. substitution in PAH molecules such as fuorene, 9-meth- Concentrations of phthalic acid esters such as dibu- ylene were of relatively higher toxicities compared to tyl phthalate, dibutyl phthalate, bis(2-methylpropyl) Yang et al. Environ Sci Eur (2020) 32:96 Page 10 of 14

ester-1,2-benzenedicarboxylic acid, di(hex-3-yl) ester toxic pollutants in the air—the environmentally persis- phthalic acid (Table 1) were higher than those of other tent free radicals, which has already been found in the chemicals, and their peak areas contributed 19% of all atmospheric particles [40–42]. Semiquinone free radi- 147 chemicals detected. Phthalic acid esters are widely cals and cyclopentadiene radicals attached to airborne used as plasticizers in various industries and have been fne particles were considered as the dominant composi- detected in water, soil, and air, because they are not tion of EPFRs in the air and are believed to exist in the air chemically bound to polymers and can therefore be eas- for a long time [42–47]. Hydroquinone molecules with ily released into the environment [26]. Te oral chronic alkane substituents and phenol substitutes may be pre- reference dose of p-phthalic acid was calculated as 1 mg/ cursors or products in the formation or transformation kg/day, approximately four orders of magnitude higher of environmentally persistent free radicals in airborne than that of the widely recognized toxic benzo[a]pyrene particles [48], and therefore the levels and characteris- −4 (3 × 10 mg/kg/day) [27], and its highest peak areas in tics of hydroquinone and environmentally persistent free the air samples we collected indicated higher inhalation radicals in the air should be correlated and merits further exposure. Six phthalic acid esters have been listed as pri- attention. Oxygenated PAHs such as benzobisbenzofuran ority controlled toxic pollutants by the US and European and dibenzofuran were also detected, and may subse- agencies considering the corroborated endocrine dis- quently chlorinate to polychlorinated dibenzofurans. rupting toxicity, and three phthalic acid esters—dimethyl We also identifed nitro- and sulfurized PAHs such as phthalate, diethyl phthalate, and di-n-octylphthalate—are dibenzothiophene and carbazole, which have acute or regulated in surface and drinking water in China [28, long-term hazardous to the aquatic life. Furthermore, 29], but phthalic acid esters in the air around industrial they may be further chlorinated to the toxic polychlorin- plants has not yet become a focus of study. Our fndings ated dibenzofurans, polychlorinated dibenzothiophenes, were in accordance with those of previous studies, which and polychlorinated carbazoles [49, 50]. Tis highlights reported higher concentrations at industrial sites than at the importance of studying high molecular weight PAHs, residential and trafcked areas [30]. Workers and resi- alkylated PAHs, and heteroatom-substituted PAHs in dents in areas contaminated by phthalic acid esters will the air, beyond the standard focus on the 16 priority be exposed to high levels over time [31], so control of pollutants. phthalic acid esters in industrial areas is essential. We detected heteroatom-substituted polycyclic aro- Occurrences of chlorinated and brominated PAHs in air matic compounds, which are often neglected in studies by target analysis of GC/Q‑TOF‑MS of environmental pollution even though their toxicity Cl/Br-PAHs are halogenated derivatives of PAHs, which is comparable to that of PAHs [32]. Oxygenated PAHs can be emitted as by-products of thermal industries and have one or more carbonyl oxygens in the aromatic ring formed through photochemical reactions in the air [51]. structure and are more mobile in the environment than Because of the large numbers of Cl/Br-PAHs congeners PAHs because of their polarity properties, easily mov- and extremely trace levels in environmental media, it is ing from air to surface water [32]. Terefore, oxy-PAHs difcult to accurately quantify and characterize these should be taken into consideration when assessing risks compounds. In addition, there are no standardized of PAHs in the air. Oxygenated PAHs have also been methods for extraction and instrument analysis of Cl/Br- reported in diesel exhaust [33], stack gas from combus- PAHs. Existing accurate analysis for multiple Cl/Br-PAH tion processes [34], and fy ash from various industries congeners is mainly conducted by HRMS [52]. We used [35]. Hydroquinone, a toxic phenolic organic compound, GC/Q-TOF-MS to analyze 21 chlorinated PAHs (includ- has been found in various industrial efuents [36–38]. In ing eight PCNs) and 17 brominated PAHs and quanti- this study, 42 oxy-PAHs including phenols, xanthenes, tated them with 12 labeled internal standards (Fig. 3a). furans, aldehydes and quinones were detected. Te oxy- Mass spectrum parameters are shown in Table 2. Te PAHs are emitted from similar primary sources of PAHs. limit of quantitation was calculated by these standard Both oxy-PAHs and PAHs were products of incomplete deviations times 10 and ranged from 1.0 to 7.2 pg/µL combustions. In addition, chemical or photo-oxidation (shown in Table 2). An accurate mass extraction win- of PAHs can also form oxy-PAHs in the environment [2]. dow ± 15 ppm was used to eliminate the matrix noise. Terefore, oxy-PAHs can widely occur in diesel exhaust, Two labeled compounds were added to the fnal extract stack gas or fy ash from thermal processes, soils and air prior to injection to assess the recoveries of 12 internal [2]. Oxy-PAHs such as hydroquinone with alkane substit- standards (ISTDs). Te recoveries of 6 PCN internal uents were detected. Apart from the known hematotoxic- standards (ISTD 1–6 in Table 2) relative to 13C-labeled ity and carcinogenicity of hydroquinone [39], it may also 1,2,3,4,5,7-hexachloro-naphthalene were calculated be a critical intermediate and precursor of an emerging to be in the range of 28.9–81.6%. Recoveries of the Cl/ Yang et al. Environ Sci Eur (2020) 32:96 Page 11 of 14

b 5-bromoacenaphthene 2/9-chlorophenanthrene

9-bromophenanthrene 1,4-dichloroanthracene

c Mono-PCN Tetra-PCN

Penta-PCN Hexa-PCN

Fig. 3 a Total ion chromatogram. b Extracted ion chromatograms of chlorinated and brominated polycyclic aromatic hydrocarbon standards. c Extracted ion chromatograms of specifc polychlorinated naphthalene homologs in air samples Yang et al. Environ Sci Eur (2020) 32:96 Page 12 of 14

Br-PAHs internal standards (ISTD 7–12) relative to acid esters, dimethylbenz[a]anthracene, which were of 13C-labeled 7,12-dichlorobenz[a]anthracene were calcu- high toxicity and concentration, indicated the infuence lated to be in range of 18.9–80.3%. Figure 3b shows the of industrial sources on the surrounding atmosphere. extracted ions chromatograms of specifc Cl/Br-PAHs in Hydroquinone with alkane substituents in the air was not air samples. Figure 3c shows the chromatograms of spe- reported previously, except for the known hematotoxicity cifc PCNs homologs, indicating sufcient resolution and and carcinogenicity, they may be critical intermediates sensitivity of the GC/Q-TOF-MS method for the syn- and precursors of an emerging toxic pollutants in air— chronization analysis of those trace pollutants containing the environmentally persistent free radicals. Te toxico- multiple congeners. Further studies can be conducted on logical signifcance of these pollutants is often neglected the development of simultaneous analysis of the widely in studies of airborne contaminants around industries concerned persistent organic pollutants of trace levels in and requires recognition. the environment. Te total concentration of the 13 chlorinated PAHs and Supplementary information 17 brominated PAHs (shown in Table 2) in air samples Supplementary information accompanies this paper at https://doi. org/10.1186/s12302-020-00376-9. was 818.9 and 294.9 pg/m3, respectively. Tese levels are similar to those estimated previously in our laboratory by isotope dilution high-resolution gas chromatography Additional fle 1: Table S1. Gas chromatography (GC) and mass spec- 3 trometry (MS) conditions. Table S2. Aliphatic hydrocarbons in air samples and HRMS (987.4 pg/m for 13 chlorinated PAHs and screened by GC/Q-TOF-MS. Table S3. Calculated toxicities of several typi- 429.6 pg/m3 for 17 brominated PAHs) in air [49]. Con- cal pollutants by the non-target screening of GC/Q-TOF-MS. centrations of chlorinated PAHs were approximately three times higher than those of brominated PAHs, Abbreviations because chlorine levels are typically higher than bro- PAHs: Polycyclic aromatic hydrocarbons; GC/Q-TOF-MS: High-resolution gas chromatography quadrupole time-of-fight mass spectrometry; PACs: mine levels in the natural environment and in thermal- Polycyclic aromatic compounds; EPA: Environmental Protection Agency; PCNs: related activities. Monochlorinated anthracene was the Polychlorinated naphthalenes; POPs: Persistent organic pollutants; Cl/Br-PAHs: most abundant congener, contributing 20%–50% of the Chlorinated and brominated PAH; GC-HRMS: Gas chromatography coupled with magnetic sector high-resolution mass spectrometry; RRFs: Relative total chlorinated PAHs in the samples, and its fractions response factors. were higher than those of dichlorinated or tetrachlorin- ated anthracene, indicating that chlorination may not be Acknowledgements We appreciate Prof. Yanliang Ren from College of Chemistry, Central China favored during the formation of the chlorinated com- Normal University for his great help in the toxicity calculation of several pound. Less-chlorinated polychlorinated naphthalene organic chemicals. This work was supported by the National Natural Science congeners were dominant in the gas phase, while more Foundation of China (Grants 91843301, 21936007, and 21906165), Collabo- rative Project supported by the Chinese Academy of Sciences and Hebei highly chlorinated congeners dominated the particle Academy of Sciences (181602), CAS Interdisciplinary Innovation Team (Grant phase. For example, 70% of 2-chloronaphthalene was in JCTD-2019-03), and the Youth Innovation Promotion Association of the Chi- the gas phase. 54% of more highly chlorinated conge- nese Academy of Sciences (2016038). ners (hexa- to octa-) existed in the particle phase. Te Authors’ contributions phenomenon may be contributed by the physiochemical GL contributed to general planning of the research. LY and GL collected the properties of Cl/Br-PAHs that highly halogenated conge- samples and performed the sample extraction. LY, JW and ZC performed the non-target screening and target analysis by GC/Q-TOF-MS. CL and MS contrib- ners with lower vapor pressure tend to be absorbed into uted to the deconvolution and identifcation of chemicals. LY wrote the draft. the particle phase. GL and MZ critically revised the manuscript. All authors read and approved the fnal manuscript.

Conclusions Funding Non-target screening of organic pollutants and simul- This work was supported by the National Natural Science Foundation of China (Grants 91843301, 21936007, and 21906165), Collaborative Project sup- taneous target detection of halogenated PAHs were ported by the Chinese Academy of Sciences and Hebei Academy of Sciences achieved by GC/Q-TOF-MS and applied to the air (181602), CAS Interdisciplinary Innovation Team (Grant JCTD-2019-03), and the samples collected surrounding metallurgical plants. Youth Innovation Promotion Association of the Chinese Academy of Sciences (2016038). Emerging pollutants of trace levels in the air including 8 polychlorinated naphthalenes (PCNs) and 30 higher Availability of data and materials cyclic halogenated PAHs as target compounds were accu- All data generated or analyzed during this study are included in this published article. rately quantitated. In addition, 187 organic chemicals categorized as PAHs, alkylated polycyclic aromatic com- Ethics approval and consent to participate pounds (PACs), heterocyclic PACs, and aliphatic hydro- Not applicable. carbons in the air samples were identifed by non-target screening. Some specifc compounds such as phthalic Yang et al. Environ Sci Eur (2020) 32:96 Page 13 of 14

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