Department of Environmental Toxicology, University of California, Davis, California

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1 1 Supporting information 2 3 Photochemical aging of guaiacol by Fe(III)oxalate complexes in 4 atmospheric aqueous phase 5 6 ongwei Pang 1, Qi Zhang 2, ongli Wang 3, Dongmei ai 1, Yingge Ma 3, Li Li 3, 7 Kangning Li 1, Xiaohui Lu 1 *, ong hen 1, Xin Yang 1,4 *, Jianmin hen Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, 10 Department of Environmental Science and Engineering, Fudan University, Shanghai , hina 12 2 Department of Environmental Toxicology, University of alifornia, Davis, alifornia , United States 14 3 State Environmental Protection Key Laboratory of Formation and Prevention of the 15 Urban Air Pollution omplex, Shanghai Academy of Environmental Sciences, 16 Shanghai , hina 17 4 Shanghai Institute of Pollution ontrol and Ecological Security, Shanghai , 18 hina orrespondence to: Xiaohui Lu (luxiaohui@fudan.edu.cn); Xin Yang 21 (yangxin@fudan.edu.cn) S1

2 41 ontents: Text S1. Materials and reagents Page S3 44 Text S2. Additional experimental details Page S4 45 Text S3. Analytical procedures Page S Figure S1. The UVvis spectra of solution containing Fe(III) + GUA and solution 48 containing Fe(III)+ oxalate + GUA Page S7 49 Figure S2. Mechanism for the dark reaction of GUA with Fe(III) ions Page S8 50 Figure S3. The Fecatalyzed photooxidation kinetics of GUA in the presence of 51 oxalate and in the absence of oxalate Page S9 52 Figure S4. The Fecatalyzed photooxidation kinetics of NB in the presence of oxalate 53 and in the absence of oxalate Page S10 54 Figure S5. Effect of oxalate concentration on the Fe(III)oxalate mediated 55 photooxidation kinetics of GUA Page S11 56 Figure S6. Molefraction distribution of the Fe(III) species Page S12 57 Figure S7. Effect of Fe(III) concentration on the Fe(III)oxalate mediated 58 photooxidation kinetics of GUA Page S13 59 Figure S8. Effect of solution p on the Fe(III)oxalate mediated photooxidation 60 kinetics of GUA Page S14 61 Figure S9. Effect of the presence of oxygen on the formation of 2 2 in irradiated 62 ferrioxalate system Page S15 63 Figure S10. Van Krevelen diagram of the oxidative products of GUA Page S16 64 Figure S11. GMS spectra of methanol formed from the photooxidation of GUA 65 Page S Table S1. The products formed through the aqueousphase reactions of GUA with 68 Page S References Page S23 S2

3 71 Text S1. Materials and reagents 72 All chemicals were analytical grade and were used as received. The water 73 employed was distilled and deionized by a Millipore purification system (Barnstead 74 NAN Pure, USA). hemical agents of iron (III) chloride anhydrous (Fel 3 ), 75 ethanedioic acid dehydrate ( ), guaiacol ( ), nitrobenzene 76 ( 6 5 N 2 ), hydrochloric acid (l), sodium hydroxide (Na) were purchased from 77 Sinopharm hemical Reagent o. Ltd. (Shanghai, hina). Sodium phosphate dibasic 78 (Na 2 P 4 ), sodium phosphate monobasic (Na 2 P 4 ), N,NDiethylp 79 phenylenediamine sulfate salt, peroxidase from horseradish were purchased from 80 SigmaAldrich. Glassware and quartzware were cleaned with a 10% l solution, 81 followed by rinsing with deionized water. All solutions were prepared using deionized 82 water S3

4 85 Text S2. Additional experimental details 86 Except where noted, the photochemical reactions were carried out under the 87 following experimental conditions: initial [Fe(III)] = 20 μm, initial [guaiacol] = 50 μm 88 and initial oxalate concentration [ ] = 250 μm at the solution p 3.0 with ml solution, all solutions were saturated with air. Moreover, the ionic strength of each 90 experiment was mol kg 1 for Nal. A tenfold (molar) excess of oxalate/fe(iii) 91 was used for the experiment to ensure complete complexation of Fe(III) by oxalate [1]. 92 These concentrations reflect the concentrations of these species found in real 93 atmospheric liquid phases. The p value of the solution was monitored by a p meter 94 during the whole experiment. The initial p of solution was adjusted to the desired p 95 with either diluted l or Na solution prior to the photochemical reactions, when 96 necessary, the p was kept constant by addition of diluted l or Na solution. The 97 p variations during all experiments were < ± 0.2 p units. The dark control 98 experiments were performed in a flask containing the necessary agents and the flask 99 was covered with aluminum foil. Aliquots of the sample (1mL) were withdrawn at 100 given time intervals and were analyzed by PL. 101 S4

5 102 Text S3. Analytical Procedures 103 S3.1 PL analysis 104 The concentration of guaiacol was determined using a PL [Agilent (1260), 105 Phenomenex Luna18 18 column ( mm, 5 μm), photodiode array detector 106 (DAD)] with a flow rate of 1 ml/min and detection wavelength of 274 nm. The mobile 107 phase consisted of 40/60 (v/v) acetonitrile/water acidified with trifluoroacetic acid 108 (TFA, 0.05%). The injection volume was 20 μl and the retention time of guaiacol was min. The concentration of nitrobenzene was determined using a PL [Agilent 110 (1260), Phenomenex Luna18 18 column ( mm, 5 μm), photodiode array 111 detector (DAD)] with a flow rate of 1 ml/min and detection wavelength of 267 nm. The 112 mobile phase consisted of 60/40 (v/v) acetonitrile/water acidified with trifluoroacetic 113 acid (TFA, 0.05%). The injection volume was 20 μl and the retention time of 114 nitrobenzene was7.22 min S3.2 RMS coupled with PL analysis 117 The analysis of oxidation products was carried out using a Q Exactive mass 118 spectrometer (rbitrap, Thermo Fisher Scientific, mass resolution= FWM ) 119 equipped with UltiMate 3000 UPL. The samples were separated on a Waters 120 XBridge 18 column ( mm, 3.5 μm) equipped with a guard column ( mm) of same packing material. The mobile phase consisted of A: 0.1% acetic acid in and B: 0.1% acetic acid in 3 N, with a gradient elution of 5% B for 3min, 123 followed by a linear increase to 100% B within 27 min, back to 5% B in 30 min. The 124 flow rate was 0.3 ml/min and injection volume was 5 μl. The mass spectra (m/z 90500) 125 were obtained in negative ion mode with electrospray ionization technology (ESI). The 126 major ion peaks were assigned as deprotonated formulas c h1 o (c 4, h 4, o 10) using Thermo Xcalibur software (version 2.2). The mass accuracy limit was set 128 as ±5ppm, and the double bond equivalent value (DBE) ought to be less than 9. The 129 DBE is calculated as c+10.5h for an ion of c h1 o S3.3 UVvis analysis and 2 2 analysis 132 A YKE UV1901 diode array spectrophotometer utilizing both its tungsten lamp 133 and deuterium lamp was used for UVVIS absorption measurements. A 1 cm quartz 134 cuvette was used for measuring absorbance and the deionized water was utilized as the 135 spectroscopic blank. The detection range of the entire spectrum was between nm. The concentration of 2 2 formed during the course of irradiation was determined 137 by a modified method based on the horseradish peroxidase (PD) catalyzed oxidation 138 of N,Ndiethylpphenylenediamine sulfate salt (DPD) by 2 2 [2]. 139 A series of standard solutions of 2 2 at concentrations of 0.1, 0.5, 1.0, 5.0, μm were freshly prepared by diluting a stock solution of 2 2 (9.79 M). 1 ml ( M Na 2 P 4 /0.263 M Na 2 P 4 ) buffer solution was added to 4 ml of a standard 142 solution or an irradiated solution followed by addition of 50 μl 1% (w/w) DPD in N 2 S 4 and 50 μl 100% (w/w) PD solution (specific activity of 100 units mg 1 ) in 144 rapid succession. The absorbance of the sample was measured at 552 nm at 40 ± 5 s 145 after the addition of the PD. The detection limit of 2 2 is 0.1 μm. S5

6 S3.4 GMS analysis 148 For gas chromatography/mass spectrometry (GMS) analyses, the sample 149 solution after reaction was directly injected into a Thermo FUS DSQ GMS, 150 equipped with a PINNWax fusedsilica capillary column (30 m 0.25 mm ID, μm). The conditions utilized for GMS analysis were: carrier gas flow 1 ml/min (e), 152 injector temperature 250, the column temperature was initially held at for 60 for 153 3min, then raised to 300 at a rate of 30 min 1, with a final holding time of 2 min. 154 The mass spectra were scanned from m/z with electron impact ionization 155 technology (EI). Data acquisition and analysis were carried out by using the Thermo 156 Xcalibur software (version 2.2). ompounds were identified using the NIST Mass 157 Spectral Library (National Institute of Standards and Technology, Washington D, 158 USA) S3.5 p measurement 161 p value was measured by a SX610 pmeter (Shanghai SanXin) equipped with 162 a SX615 combination glass electrode with saturated Kl as inner reference solution, 163 and calibrated with p 4, 7, 10 standard buffers (Shanghai SanXin) S3.6 Irradiance measurements 166 Irradiance measurements at the surface of solutions was carried out by using a 167 ELNP 2000 optical power meter (Beijing EAULIGT) S3.7 Equilibrium calculation 170 All speciation calculations in this work were carried out with a chemical 171 equilibrium calculation programvisual MINTEQ at fixed Fe(III) concentration of μm at p 3.0, 25 o and the ionic strength was mol kg S6

7 Figure S1. The UVvis spectra of solution containing 20 μm Fe(III) and 50 μm GUA 192 (a) and solution containing 20 μm Fe(III), 250 μm oxalate and 50 μm GUA (b) as a 193 function of time at p = 3 ± S7

8 Figure S2. Proposed mechanism for the dark reaction of GUA with Fe(III) and the 209 formation of oligomers through the radical recombination reactions in aqueous phase. 210 Adopted from ref [3] S8

9 Figure S3. The Fecatalyzed photooxidation kinetics of GUA in the presence of oxalate 220 (red line) and in the absence of oxalate (black line). Fe(III)] 0 = 20 μm, [GUA] 0 = μm, [xalate] 0 = 250 μm, p = 3.0 ± 0.1, air saturated solution. 222 S9

10 Figure S4. The Fecatalyzed photooxidation kinetics of NB in the presence of oxalate 225 (red line) and in the absence of oxalate (black line). Fe(III)] 0 = 20 μm, [NB] 0 = 50 μm, 226 [xalate] 0 = 250 μm, p = 3.0 ± 0.1, air saturated solution S10

11 Figure S5. Effect of oxalate concentration on the photooxidation kinetics of GUA in 241 the presence of Fe(III)oxalate complexes. Fe(III)] 0 = 20 μm, [GUA] 0 = 50 μm, p = ± 0.1, air saturated solution. x represents oxalate S11

12 Figure S6. Molefraction distribution of the Fe(III) species (25 o, p 3.0, [Fe(III)] = μm, the ionic strength of was mol kg 1 ) S12

13 Figure S7. Effect of Fe(III) concentration on the photooxidation kinetics of GUA in 271 the presence of Fe(III)oxalate complexes. [xalate] 0 = 250 μm, [GUA] 0 = 50 μm, p 272 = 3.0 ± 0.1, air saturated solution S13

14 Figure S8. Effect of solution p on the photooxidation kinetics of GUA in the presence 280 of Fe(III)oxalate complexes. Fe(III)] 0 = 20 μm, [xalate] 0 = 250 μm, [GUA] 0 = μm, air saturated solution S14

15 Figure S9. Effect of the presence of oxygen on the formation of 2 2 in irradiated 293 ferrioxalate system. [Fe(III)] = 20 μm, [xalate] = 250 μm, [GUA] = 50 μm, p = ± 0.1, air bubbling (red line), nitrogen bubbling (blue line). 295 S15

16 Figure S10. Van Krevelen diagram of the oxidative products of GUA from the 298 photo/ferrioxalate system: [Fe(III)] 0 = 20 μm, [xalate] 0 = 250 μm, [GUA] 0 = 50 μm, 299 p = 3.0 ± 0.1, air bubbling S16

17 Figure S11. GMS spectra of methanol formed from the photooxidation of GUA in 305 the presence of Fe(III)oxalate system. [Fe(III)] 0 = 20 μm, [xalate] 0 = 250 μm, 306 [GUA] 0 = 50 μm, p = 3.0 ± 0.1, air bubbling S17

18 Table S1. The products formed through the aqueousphase reactions of GUA with generated by photolysis of Fe(III) oxalate system identified with ( ) rbitrap MS. The rank is based on the peak abundance of the ions. No. 1 Ion composition (m/z) ( ) Molecular Formula Proposed Structure The compound s code in the Fig. 5 or 6) Fig. 5, A 15 2 No. Ion composition (m/z) ( ) Molecular formula Proposed structure The compound s code in the Fig. 5 or 6) ( ) Fig. 5, A ( ) Fig. 5, A ( ) ( ) S18

19 ( ) ( ) Fig. 5, A ( ) Fig. 6, B ( ) Fig. 6, B ( ) ( ) ( ) Fig. 6, B ( ) Fig. 5, A ( ) Fig. 5, A ( ) S19

20 ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) Fig. 5, A ( ) Fig. 5, A 7 S20

21 ( ) ( ) ( ) Fig. 5, A ( ) ( ) ( ) ( ) ( ) ( ) Fig. 5, A ( ) S21

22 ( ) ( ) ( ) Fig. 5, A ( ) S22

23 References: [1] Weller, orn S, errmann. Effects of Fe (III)concentration, speciation, excitationwavelength and light intensity on the quantum yield of iron (III)oxalato complex photolysis. Journal of Photochemistry and Photobiology A: hemistry. 2013;255:419. [2] Bader, Sturzenegger V, oigne J. Photometric method for the determination of low concentrations of hydrogen peroxide by the peroxidase catalyzed oxidation of N, N diethylpphenylenediamine (DPD). Water Research. 1988;22(9): [3] Lavi A, Lin P, Bhaduri B, armieli R, Laskin A, Rudich Y. haracterization of LightAbsorbing ligomers from Reactions of Phenolic ompounds and Fe (III). AS Earth and Space hemistry. 2017;1(10): S23