Secondary organic aerosol formation from ... - Semantic Scholar

s

Sciences

ss

Sciences

Discussions

Discussions

2

2

Discussions

Open Access

1

Open Access

L. D. Yee , K. E. Kautzman , C. L. Loza , K. A. Schilling , M. M. Coggon , 1 P. S. Chhabra2,** , M. N. Chan1,*** , A. W. H. Chan2,**** , S. P. Hersey J. D. Crounse3 , Earth,System Earth System 1,3 2,1 2,1 P. O. Wennberg , R. C. Flagan , and J. H. Seinfeld Dynamics Dynamics

|

Open Access

Open Access

Earth System Sciences

Discussion Paper

Open Access

Open Access

Earth System 3485 Sciences

ACPD 13, 3485–3532, 2013

Secondary organic aerosol formation from biomass burning L. D. Yee et al.

Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Open Access

Open Access

Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA Geoscientific Geoscientific 2 Division of Chemistry and Chemical Engineering, California Institute of Technology, Instrumentation Instrumentation Pasadena, CA, USA Methods and Methods and 3 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, Data Systems Data Systems CA, USA Discussions * now at: Department of Chemistry, Towson University, Towson, MD, USA Geoscientific ** now at: Aerodyne Research Geoscientific Inc., Billerica MA, USA *** ModelLaboratory, Development now at: Chemical Sciences Division, Lawrence Berkeley National Berkeley, CA, Model Development Discussions USA **** now at: Department of Environmental Science, Policy and Management, University of Hydrology and Hydrology California, Berkeley, Berkeley, CA, USA and

Discussion Paper

2

|

2,*

Open Access

1

Open Access

of the Past

Discussions

Open Access

Open Access

Biogeosciences Biogeosciencesaerosol formation Secondary organic from biomass burning intermediates: Climate Climate phenol and methoxyphenols of the Past

Discussion Paper

Discussions

|

Open Access

Atmospheric

This discussion paper is/has Measurement been under review for the journal Atmospheric Chemistry Measurement and Physics (ACP). Please referTechniques to the corresponding final paper in ACP ifTechniques available.

Discussion Paper

Open Access

Discussions Open Access

Atmospheric

Atmospheric Chemistry and Physics

Open Access

Atmos. Chem. Phys. Discuss., 13, 3485–3532, 2013 Atmospheric www.atmos-chem-phys-discuss.net/13/3485/2013/ Chemistry doi:10.5194/acpd-13-3485-2013 and Physics © Author(s) 2013. CC Attribution 3.0 License.

Full Screen / Esc

Printer-friendly Version Interactive Discussion

Correspondence to: J. H. Seinfeld ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union.

Discussion Paper

Received: 20 January 2013 – Accepted: 25 January 2013 – Published: 6 February 2013

ACPD 13, 3485–3532, 2013

| Discussion Paper


Title Page

| Discussion Paper

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Abstract

Discussion Paper |

3486

Full Screen / Esc


5

Discussion Paper |

3487

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

25

Biomass burning is a major source of atmospheric organic aerosol (OA), with contributions from both anthropogenic (biofuel, deforestation, etc.) as well as natural sources such as wildfires. Aerosol produced from biomass burning has been estimated to ac-

Discussion Paper

1 Introduction

|

20

Discussion Paper

15

|

10

The formation of secondary organic aerosol from oxidation of phenol, guaiacol (2methoxyphenol), and syringol (2,6-dimethoxyphenol), major components of biomass burning, is described. Photooxidation experiments were conducted in the Caltech laboratory chambers under low-NOx ( 24 h, until the particle number concentration was < 100 cm−3 and the volume 3 −3 concentration was < 0.1 µm cm . In all yield experiments, ammonium sulfate seed aerosol was used to promote condensation of low volatility oxidation products. The seed aerosol was generated by atomization of a 0.015 M aqueous ammonium sulfate solution. Following atomization, the size distribution of the seed particles peaked at ∼ 56 nm with an average number concentration of ∼ 2700 cm−3 , and a total seed vol−3 ume concentration of 10–15 µm cm was achieved. The hydrocarbon was introduced into the chamber by injecting a known volume of pure hydrocarbon into a glass bulb and flowing purified air over the hydrocarbon at 5 L min−1 until the hydrocarbon had fully vaporized. For these low-NOx experiments, hydrogen peroxide (H2 O2 ) was used as the OH precursor. Prior to atomization of the ammonium sulfate seed, H2 O2 was introduced

|

3

Discussion Paper

2 Experimental section

|

10

Discussion Paper

5

of phenol, guaiacol, and syringol by OH in laboratory chamber studies under low-NOx (< 10 ppb) conditions. In addition, we present analyses of the gas- and particle-phase constituents in guaiacol photooxidation to elucidate the chemical mechanism involved in guaiacol SOA formation. We qualitatively compare the chemistry of the test compounds to explore why syringol results in lower SOA yield compared to phenol and guaiacol. A further motivation for this work is the potential use of phenol, guaiacol, and syringol as compounds to represent biomass burning emissions in atmospheric models of organic aerosol formation. SOA products identified in the laboratory studies may also serve as markers for biomass burning in ambient aerosols.

Full Screen / Esc


5

Discussion Paper

2.2 Gas-phase measurements

|

10

Discussion Paper

−1

by flowing 5 L min of purified air through a glass trap containing 280 µL of a 50 % aqueous H2 O2 solution. The glass trap was submerged in a warm water bath maintained at 35–38 ◦ C. This resulted in an approximate concentration of 4 ppm H2 O2 in the chamber. The aerosol number concentration and size distribution were measured by a differential mobility analyzer (DMA, TSI model 3081) coupled with a condensation nuclei counter (TSI, CNC-3760). After allowing all concentrations to stabilize, irradiation was initiated. The temperature (T ), relative humidity (RH), and concentrations of O3 , NO, and NOx were continuously monitored. Experiments were run at temperatures ranging ◦ ◦ 20–26 C and varied within ±2 C. RH remained below 10 %. Table 2 summarizes the experimental conditions for the series of methoxyphenol oxidation experiments conducted.

|

15

Discussion Paper |

3490

13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

20

The hydrocarbon concentration was continuously monitored by GC/FID in the phenol experiments. Chamber air was sampled into a 10 mL injection loop and injected onto a HP5 15 m × 0.53 mm ID ×1 µm thickness column installed on a 6890 Agilent GC. The GC response was calibrated by dissolving a known mass of the hydrocarbon in methanol and then vaporizing a known volume of that solution into a 55 L Teflon chamber. Guaiacol and syringol measurements obtained using the GC/FID were unreliable due to condensation loss in the sample loop; thus, the hydrocarbon concentration during these experiments was monitored using Chemical Ionization Mass Spectrometry (CIMS) in negative mode operation.

Discussion Paper

2.2.1 Gas chromatography/flame-ionization detection (GC/FID)

ACPD

Full Screen / Esc


5

|

3491

Discussion Paper

25

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

20

A detailed description of the aerosol filter sample collection and extraction protocol for the Caltech laboratory chambers has been previously published (Surratt et al., 2008). Aerosol samples were collected on Teflon filters (PALL Life Sciences, 47-mm diameter, 1.0-µm pore size, teflomembrane). Filter samplers employed for aerosol filter sample collection used a front and back-up filter sampling approach, in which back-up filters were collected in order to examine if aerosol breakthrough from the front filter occurred or whether evaporation of semivolatiles from the front filter occurred during sampling. In all experiments, no SOA constituents were detected on the back-up filters. Filter sam-

Discussion Paper

2.3.1 Chamber filter sample collection, extraction, and off-line chemical characterization

|

2.3 Particle-phase measurements

Discussion Paper

15

|

10

Monitoring of gas-phase oxidation products was carried out in real time by the use of a CIMS instrument. The details of this instrument are described elsewhere (St. Clair et al., 2010). The instrument operates in both negative mode, using CF3 O− as a reagent ion, and in positive proton transfer reaction (PTR)-MS mode. Negative mode is found to be more selective towards the detection of hydroperoxides and polar molecules, particularly acids, while positive mode detects a broader range of organic compounds. Analytes in negative mode can be monitored as the cluster product [R · CF3 O]− and/or as the transfer product if it is more strongly acidic [R · F]− , where R + is the analyte. Analytes in positive mode cluster as [R · (H2 O)n ] . Mass scans covering masses 50–300 amu for negative mode, and 50–200 amu for positive mode, with a total scan time of ∼ 6 min were continuously repeated over the course of each experiment. Guaiacol was monitored at the fluoride transfer product ([M + 19]− ), m/z 143, and the cluster product ([M + 85]− ), m/z 209, in negative mode operation. Syringol was also monitored at the fluoride transfer product, m/z 173, and the cluster product, m/z 239.

Discussion Paper

2.2.2 Chemical ionization mass spectrometry (CIMS)

Full Screen / Esc


3492

|

Discussion Paper

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

pling was initiated when the aerosol volume reached its maximum (constant) value, as determined by the DMA. Depending on the total volume concentration of aerosol in the 3 chamber, the duration of filter sampling was 1.8–2.1 h, which resulted in 2.0–2.9 m of total chamber air sampled. Teflon filter extraction protocols in high-purity methanol (LC-MS CHROMASOLV-Grade, Sigma-Aldrich) have been described previously (Surratt et al., 2008). The resultant filter extracts were then analyzed by a Waters ACQUITY ultra performance liquid chromatography (UPLC) system, coupled with a Waters LCT Premier TOF mass spectrometer equipped with an ESI source, allowing for accurate mass measurements by UPLC/ESI-TOFMS to be obtained for each ion (Surratt et al., 2008). Selected filter extracts from experiments were also analyzed by a Thermo Finnigan Surveyor high performance liquid chromatography (HPLC) system (pump and autosampler) coupled to a Thermo Finnigan LCQ ion trap mass spectrometer (ITMS) equipped with an ESI source, allowing for tandem MS measurements to be obtained. Data were acquired and processed using Xcalibur version 1.3 software. A Waters Atlantis T3 column (3 µm particle size; 2.1 × 150 mm) was employed, which is similar to the Water ACQUITY UPLC HSS column used for the UPLC/ESI-TOFMS analysis. The mobile phases consisted of 0.1 % acetic acid in water (A) and 0.1 % acetic acid in methanol (B). The applied 45 min gradient elution program was as follows: the concentration of eluent B was kept at 3 % for 4 min, then increased to 100 % in 21 min, holding at 100 % for 10 min, then decreased to 3 % in 5 min, and kept at 3 % for 5 min. The −1 injection volume and flow rate were 10 µL and 0.2 mL min , respectively. The ion trap mass analyzer was operated under the following conditions: sheath gas flow (N2 ), 65 arbitrary units; auxiliary gas flow (N2 ), 3 arbitrary units; source voltage, −4.5 kV; capillary voltage, −14.5 V; tube lens offset, 7 V; capillary temperature, 200 ◦ C; and maximum ion injection time, 200 ms. Two scan events were used during each chromatographic run; scan event 1 was the full scan mode in which data were collected from m/z 120 to 600 in the negative ionization mode and scan event 2 was the MS2 mode in which product ions were generated from significant base peak ions observed in scan event

Full Screen / Esc


Discussion Paper

5

1. For MS2 experiments, an isolation width of 2.5 m/z units and a normalized collision − energy level of 35 % were applied. The [M-H] ion signal optimization was carried out −1 by introducing a 1 mg mL malic acid standard solution. Due to the on-axis ESI source that is characteristic of the LCQ ITMS instrument, a solvent delay time of 3.5 min (which diverted the column effluent from the ESI source to waste) was employed to prevent clogging by nonvolatile salts at the entrance of the capillary.

|

10

|

3493

Discussion Paper

25

The formation of secondary organic aerosol (SOA) results from the gas-particle partitioning of low-vapor-pressure products formed in the oxidation of volatile organic compounds (VOCs). The time-dependent aerosol growth curves permit analysis of the equi-

13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

3 SOA yields and growth curves

Discussion Paper

20

|

15

Real-time aerosol mass spectra were obtained using an Aerodyne HR-ToF-AMS (DeCarlo et al., 2006). The HR-ToF-AMS was operated in a lower resolution, higher sensitivity “V-mode”, and a high-resolution “W” mode, switching between modes once every minute. The “V-mode” data were analyzed to extract sulfate, ammonium, and organic spectra according to procedures in Allan et al. (2004). Calculation of the SOA densities were achieved by comparing the particle mass distributions obtained using the particle ToF mode and the volume distributions obtained by the DMA (Bahreini et al., 2005) in nucleation (seed-free) experiments. O:C, N : C, and H : C ratios were determined from “W” mode data using the APES toolbox and applying the procedures outlined in Aiken + et al. (2007) and Aiken et al. (2008). The particle-phase signal of CO and the organic + contribution to Hx O ions were estimated as described in Aiken et al. (2008). Particle-into-liquid sampler/ion chromatography (PILS/IC) was also employed as described in Kautzman et al. (2010) for the guaiacol experiments, though we find that < C6 diacids do not constitute an important fraction of the SOA formed.

Discussion Paper

2.3.2 High-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS)

ACPD

Full Screen / Esc


3494

|

Discussion Paper

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

librium and kinetic roles involved in SOA formation (Chan et al., 2007; Kroll and Seinfeld, 2005). The SOA yield is defined as the ratio of mass of organic aerosol formed, ∆Mo , to the mass of the parent organic species consumed, ∆Org, Y = ∆Mo /∆Org. The SOA yields for all experiments are summarized in Table 2. To calculate the mass concentration of the SOA, the SOA volumes established by DMA measurements are wall-loss corrected and then multiplied by the SOA density, as determined by the AMS −3 in seed-free (nucleation) experiments. A density of 1.65 µg cm was determined for −3 phenol. Guaiacol and syringol densities were determined to be 1.45 and 1.49 µg cm , respectively. The O:C was calculated at time of maximum SOA growth for these systems and were reported in Chhabra et al. (2011). O:C values of 0.88±0.27, 0.89±0.28, and 0.97±0.30 were calculated for the phenol, guaiacol, and syringol systems, respectively. About 80 % of the initial phenol was reacted in these experiments. SOA yields for phenol range 25–44 % under the experimental conditions. For phenol, the hydrocarbon measurement obtained from all gas-phase instruments displayed interferences under low-NOx conditions, leading to a wider spread and greater uncertainty in the yield and growth curve parameters. Still, the measured yields under low-NOx conditions overlap with the range of 38–45 % reported by Nakao et al. (2011). Characteristic growth curves for guaiacol are shown in Fig. 1. Greater than 90 % of the initial guaiacol was consumed over the course of all experiments except for the higher guaiacol loading 1/29 experiment as noted in Table 2. SOA yields from guaiacol photooxidation, based on the final aerosol volume achieved, range 44–50 %. Aerosol growth curves under these conditions for all initial guaiacol and seed concentrations fall on a line (Fig. 1), consistent with the formation of essentially non-volatile products. Aerosol growth curves for syringol are shown in Fig. 2. Within six hours of irradiation, the syringol levels are lower than the limit of detection. The SOA yields for syringol are less than those of guaiacol, ranging 25–37 %. This range overlaps yields of 10– 36 % reported for syringol photooxidation under high-NOx (approaching 10 ppm NO) conducted by Lauraguais et al. (2012) using CH3 ONO as the OH source. The SOA

Full Screen / Esc


|

3495

Discussion Paper

25

Substituent groups such as -OH and -OCH3 activate more strongly the aromatic ring towards electrophilic addition of OH compared to the -CH3 group. Of these groups, activa-

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

4.1 Gas-phase oxidation

Discussion Paper

20

We present in this section an analysis of the gas-phase mechanistic chemistry involved in SOA formation based on the CIMS traces for each system along with SOA mass growth over time. All ions unless otherwise noted were monitored during negative mode operation. CIMS signals are plotted in arbitrary units (a.u.). Discussion is focused on the guaiacol system since the offline aerosol filter analyses complement the gas-phase data. Chemical parallels are drawn between the three systems.

|

4 SOA formation chemistry

Discussion Paper

15

|

10

Discussion Paper

5

yields from the photooxidation of syringol are substantially lower than those of phenol and guaiacol, even though the boiling point and vapor pressure of syringol suggest it might have greater potential to form SOA. We further explore the chemical basis for this after examining the gas-phase chemistry. In this low-NOx regime, the aerosol growth curves overlap within a system, regardless of initial organic loading. Most methoxyphenol experiments ended shortly after the hydrocarbon decay was complete. Though, even 4 h after 109 ppb syringol was completely reacted in the 3/29 experiment, there was no additional SOA growth. The type of growth observed here is typified by a mechanism involving oxidation to form SOA either from first-generation products or sufficiently rapid low-volatility product formation over the course of the experiment from further generation reactions (Chan et al., 2007; Ng et al., 2006). We believe it to be the latter explanation in the case of methoxyphenol systems. The high-level of oxidation determined from the measured O:C ratios of the SOA are indicative of multi-generation products, which is consistent with the identified gas and aerosol products discussed below.

Full Screen / Esc


ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

25

Discussion Paper

20

|

Initial steps of the phenol gas-phase mechanism have been elucidated elsewhere (Olariu et al., 2002; Berndt and Boge, 2003). Phenol + OH proceeds primarily with ortho-OH addition to the ring, O2 addition, followed by elimination of HO2 to form 1,2-dihydroxybenzene (catechol). In the low-NOx phenol experiments, CIMS ions are tracked that show successive OH adduct product formation up to three generations. Quinone products are also likely, though these are not detected in negative mode operation of the current CIMS technique unless they are additionally functionalized. A list of ions monitored in this system is presented in Table 3. Representative data for the phenol low-NOx system are shown in Fig. 3. Phenol, C6 H6 O, is monitored at m/z 179, a cluster product. We do not include m/z 113, the fluoride transfer product, because 3496

|

4.2 Phenol chemistry

Discussion Paper

15

|

10

Discussion Paper

5

tion potential of the ring increases in order of -CH3 < -OCH3 < -OH. Thus, as predicted, methoxyphenol compounds react faster with OH than their methyl or unsubstituted equivalents (Coeur-Tourneur et al., 2010). Methoxy and hydroxy substituent groups tend to make OH-attack favorable at positions ortho and para to the substituents, so structures for the measured m/z’s are proposed from chemical mechanisms assuming one of these positions of initial OH-attack. H-atom abstraction from the methoxy group is expected to be small, as this path was determined to contribute < 4 % in the case of methoxybenzene (Coeur-Tourneur et al., 2010). A generation is defined as the OH-initiated reaction of a stable (non-radical) species, and the OH exposure is calculated as the product of the OH concentration (inferred from the parent hydrocarbon decay) and the hours of irradation. Each m/z is the sum of the signal from all isomeric structures detected by the CIMS at that ion, but are not shown explicitly in the abbreviated mechanisms and tables presented. However, from the chemical ionization method employed, we expect certain common chemical features of the proposed structures. For example, many of the transfer [M+19]− products are likely acidic, containing carboxylic acid groups and/or sufficient acidic hydroxyl groups.

Full Screen / Esc


ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper |

3497

Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

this signal includes interference from another compound (likely a small acid) that grows in over time. Dihydroxybenzene, C6 H6 O2 , is observed primarily as the fluoride transfer product m/z 129 (DHB) with less signal observed at the m/z 195 cluster product. A trace at m/z 211 indicates a third OH addition to the ring to form trihydroxybenzene (THB), C6 H6 O3 . These time profiles are shown along with SOA growth and phenol decay for the first nine hours of irradiation (Fig. 3). SOA growth occurs coincident with the growth of m/z 211 (THB), indicating that the transition to lower volatility products to 6 −3 form SOA likely occurs along the 3rd addition of OH just after ∼ 1 × 10 molec cm h of OH exposure. This is the approximate equivalent of one hour of photooxidation in the atmosphere assuming an ambient OH concentration of ∼ 1 × 106 molec cm−3 . There was very little signal at m/z 227, presumably C6 H6 O4 (4HB) and a minor amount at m/z 229, the hydroperoxide C6 H8 O4 . Figure 3 also shows that the SOA is in equilibrium with m/z 185, which we propose to be the ring fragment C4 H4 O3 , a carboxylic acid that forms from the decomposition of the bicyclic radical from phenol + OH. Another carboxylic acid, C4 H4 O4 , is monitored at m/z 135, which could be the analogous ring fragment from dihydroxybenzene + OH. These acids approach the high O:C ratios characteristic of the SOA in this system. Comparisons of the CIMS gas-phase traces and the offline filter analyses from similar experiments performed by Nakao et al. (2011) provide additional insights. Nakao et al. (2011) utilized electrospray ionization and atmospheric pressure chemical ionization mass spectrometry (ESI/APCI-TOFMS) as well as PILS-ESI-TOFMS for analysis, though Nakao et al. (2011) noted that the PILS-ESI-TOFMS spectra may include water soluble gas-phase species because a denuder was not used. While Nakao et al. (2011) observed an exact mass match that corresponds with the bicyclic hydroperoxide from phenol (C6 H8 O6 ) and another compound with a suggested formula C6 H8 O7 using both techniques, we do not observe these products in the gas-phase with the CIMS. It is possible that these compounds are of sufficiently low volatility at this point that they are not measurable in the gas phase. The CIMS does detect ions corresponding to several

Full Screen / Esc


Discussion Paper

4.3 Guaiacol chemistry

|

20

Discussion Paper

15

|

10

Discussion Paper

5

< C6 products seen in Nakao et al. (2011), including: C4 H4 O3 at m/z 185, C4 H4 O4 at m/z’s 135 and 201, and C3 H4 O3 at m/z 107. Nakao et al. (2011) also observed a series of oxygen additions, from C6 H6 O2 to C6 H6 O5 , which are interpreted to possibly be a series of OH adduct products. Another structural possibility is that these are C6 retaining, but ring-opened carboxylic acids that would correspond to large signals in the CIMS as transfer products: m/z’s 145, 161, and 177. From the time profiles of these CIMS ions, we predict that they are likely carboxylic acids even though the proposed chemical formulae are isomeric to the aromatic OH adducts. The prevalence of these products may explain the absence of a strong signal from a hydroperoxide C6 H8 O4 at m/z 229. The alkylperoxy radical preferentially isomerizes to form the bicyclic peroxide radical and decomposes to < C6 fragments as mentioned above, or it may participate in chemistry that regenerates OH and opens the ring (Birdsall et al., 2010). Figure 4 outlines a potential mechanism similar to that presented in Birdsall et al. (2010) to form these multifunctional C6 carboxylic acids from phenol, dihydroxybenzene, and trihydroxybenzene. OH regeneration could also come from photolysis of a hydroperoxide producing a favorable alkoxy radical for ring opening, though we would not expect this to be significant on such a quick timescale that is consistent with negligible signal from the hydroperoxide. All CIMS traces for proposed ring opening acids (ACID) and ring fragments (FRAG) are presented in Fig. 5. They all share a similar trend of constant linear growth over time.

ACPD 13, 3485–3532, 2013


Title Page Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Abstract

Discussion Paper

25

|

Figure 6 presents proposed oxidation pathways for the guaiacol system under low-NOx conditions. Solid boxed structures indicate that the expected m/z from the chemical ionization reactions in the CIMS for that compound was detected. The m/z monitored is indicated, as are proposed Cx Hy Oz formulas and molecular weights. A list of ions monitored in this system is presented in Table 4. Chemical formulas shown in red indicate correspondence with a suggested Cx Hy Oz for accurate mass observations in filter data (Table 5). The particular structures in Fig. 6 indicate potential structures for 3498

Full Screen / Esc


Discussion Paper

4.3.2 Pathway 2: continuous OH addition to ring

|

15

Despite predominant conditions of RO2 + HO2 chemistry, we do not observe strong signals in the CIMS measurements for potential hydroperoxides, as is similar to the case of phenol. A small trace at m/z 259 suggests that there is slight production of the hydroperoxide C7 H10 O5 . The offline filter analysis does reveal a small contribution from a corresponding accurate mass measurement (Table 5). More significant signals in the CIMS are presented in Fig. 7, demonstrating that the preferred routes are to preserve aromaticity or involve isomerization to the bicyclic radical. This observation is consistent with previous studies on aromatic systems (Calvert et al., 2002; Bloss et al., 2005; Johnson et al., 2005; Birdsall et al., 2010).

Discussion Paper

10

|

4.3.1 Pathway 1: RO2 + HO2

Discussion Paper

5

the accurate mass suggested chemical formulae and the mechanism does not explicitly present all potential isomeric structures. The boxed colors correspond with the colors used for ion time traces as measured by the CIMS and included in Fig. 7. Guaiacol gas-phase oxidation proceeds with OH addition to the ring, followed by reaction with oxygen to form an organic peroxy radical. Under the experimental conditions, the fate of this RO2 radical is reaction with HO2 to form a hydroperoxide (Fig. 6, pathway 1), elimination of HO2 to retain aromaticity (Fig. 6, pathway 2), or isomerization to the bicyclic radical (Fig. 6, pathway 3).

ACPD 13, 3485–3532, 2013



Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Abstract

3499

|

25

The general chemical development of the consecutive OH addition pathways in the guaiacol low-NOx system are tracked in Fig. 7. Figure 6, pathway 2 is marked by m/z 225 on the CIMS, a cluster product for the guaiacol OH-adduct product, C7 H8 O3 and denoted as G + OH. Successive OH addition products are monitored at 16 amu increments at m/z’s 241 and 257, for C7 H8 O4 denoted as G + 2OH and C7 H8 O5 denoted as G + 3OH, respectively. The third OH adduct can be tracked at both the transfer and the cluster products, m/z 191 and m/z 257, respectively. However, m/z 257 includes the

Discussion Paper

20

Full Screen / Esc


Discussion Paper

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

25

|

20

|

The bicyclic peroxy radical can react with HO2 to form the bicyclic hydroperoxide C7 H10 O7 (Fig. 6, pathway 3ai), however no evidence exists for this product in the CIMS. This is analogous with the bicyclic hydroperoxide from the phenolic case. However, if this product is formed, it already has a low vapor pressure and an O:C of 1, and would likely partition into the aerosol phase. Filter data also indicate the presence of C7 H10 O7 in the particle-phase (Table 5). The majority of the filter data guaiacol products exhibit O:C ratio > 0.7, and the average bulk O:C ratio as measured by the AMS is 0.89, so it is likely these hydroperoxide species may immediately partition and become further processed in the particle phase. Alternatively, the bicyclic radical can rearrange, breaking the oxygen bridge to form an epoxide and open the ring (Fig. 6, pathway 3aii). There is evidence of a significant epoxide (EPOX) route that grows in early with the dihydroxybenzene route (Fig. 7). The epoxide is monitored at m/z 257, the cluster product of C7 H8 O5 (Fig. 7), though there is some later contribution from the third generation OH adduct, as mentioned earlier. The epoxide will continue to react with OH to generate more functionalized molecules that will likely contribute to SOA formation. The bicyclic radical can also decompose to several fragments as shown in the box in Fig. 6, pathway 3aiii. A major fragment is observed at m/z 149, which could be the 3500

Discussion Paper

15

4.3.3 Pathway 3: isomerization to bicyclic radical

|

10

Discussion Paper

5

combined signal of rapid epoxide formation and the later formed third generation OH adduct. A signal at m/z 191 is predominantly the third generation OH adduct during the first 8 h until another product (likely an acid) grows in at this m/z. The first OH-adduct product (m/z 225) is short-lived due to further activation of the ring by the additional hydroxy group. Formation of C7 H8 O4 monitored at m/z 241 follows promptly. The signal at m/z 191 (not shown) was observed to follow after m/z 241, indicating that third OH addition is achieved. C7 H8 O5 is also a proposed chemical formula for a product observed in the filter analysis (Table 5), suggesting that the third OH adduct is of sufficiently low volatility to partition to the particle phase.

Full Screen / Esc


Discussion Paper

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

25

|

20

|

The early growth of a strong signal at m/z 129 (Fig. 7) and a matching time profile at m/z 195 upon irradiation suggests that dihydroxybenzene (C6 H6 O2 ) is somehow formed from guaiacol (C7 H8 O3 ) + OH in the gas phase. This is further supported by matching time profiles from the guaiacol and phenol systems for dihydroxybenzene (DHB) and its oxidation to trihydroxybenzene (THB) in Fig. 8a, as well as growth of the proposed C6 ring opening acids (Fig. 8b). In the guaiacol system, the raw signal at m/z 211 18 includes contributions from the O natural isotope peak of the guaiacol cluster product and trihydroxybenzene. The signal at m/z 211 has been corrected to reflect only the contribution from trihydroxybenzene (G-THB). There is negligible signal at m/z 227 in the guaiacol system, indicating that the dihydroxybenzene that is formed proceeds only to one more step of oxidation before the carbon along this route is incorporated into pathways besides continuous OH adduct formation. Rather, the carbon likely ends up in production of ring-opened acids as shown in Fig. 8b. A trace at m/z 243 is present in the guaiacol system, though because there is negligible signal at m/z 227, it is unlikely that this ion is part of the OH adduct series from dihydroxybenzene as C6 H6 O5 . Still, an exact mass match for C6 H6 O5 is the fourth highest product (in terms of area counts) of constituents identified in the filter data, and m/z 243 follows the SOA trace indicating that it may be an important contributor to 3501

Discussion Paper

15

4.3.4 Pathway 4: methoxy loss route

|

10

Discussion Paper

5

methoxy analog to the phenolic fragment, hydroxy-butenedial (C4 H4 O3 ) at m/z 185. We propose that m/z 149 is a methoxy-hydroxy-butenedial fragment, C5 H6 O4 . C5 H6 O4 is also an accurate mass assignment for a product observed in the filter data (Table 5). The m/z 149 trace has a similar profile to the SOA mass curve, indicating that it is in equilibrium with the particle phase (Fig. 7). Other possible fragments are observed at m/z’s indicated in the mechanism. The < C4 fragments approach O:C values > 1, and the C4 and C5 fragments would likely undergo further oxidation in the gas phase and then possibly contribute to the particle phase. The fate of butenedial (C4 H4 O2 ) has been described elsewhere (Calvert et al., 2002; Bloss et al., 2005).

Full Screen / Esc


5

| Discussion Paper

4.4 Syringol chemistry

Discussion Paper

15

The offline filter analysis suggests that there are additional chemical pathways for this system than those inferred from the gas-phase CIMS measurements. The top fifteen ions (by highest peak area) are presented in Table 5 along with measured masses and suggested corresponding chemical formulae. Of the suggested chemical formulae, the O:C ranges from 0.67 to 1.5. The < C7 components are likely ring fragments that have undergone further oxidation to achieve such high O:C compared to those shown in Fig. 6, pathway 3aiii. Of the C7 retaining products listed in Table 5, all suggested chemical formulae except C7 H5 O5 can be explained by first-generation products along pathways 1, 2, 3ai, and 3aii (Fig. 6) and the analogous pathways in higher generation chemistry from the OH adducts. Similar structures to those proposed here have been observed previously in EI-MS analyses (Justesen, 2001). However, since many corresponding signals are not observed in the CIMS, it is also possible that a number of these highly oxygenated (> O5 ) species may be formed in the particle phase.

|

10

4.3.5 Guaiacol aerosol-phase products

Discussion Paper

the particle phase. In the event that radical placement occurs on the carbon containing the methoxy group during formation of the bicyclic radical, carbon loss may occur by removal of a methyl radical. This leads to formation of a C6 bicyclic ketone product as outlined in pathway 3b of Fig. 6.

ACPD 13, 3485–3532, 2013



Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Abstract

3502

|

25

The chemistry of syringol under low-NOx conditions leads to rapid formation of a rich diversity of gas-phase products and SOA growth. Whereas at least two generations of OH oxidation of phenol are required to generate SOA, guaiacol and syringol produce SOA in the first generation. This is clear when comparing the SOA mass curves between systems in Figs. 3, 7, and 9. As expected, syringol is more reactive than guaiacol because of its additional methoxy group. Syringol is detected primarily at the transfer − − [M+19] , m/z 173, with some signal at the cluster product [M+85] , m/z 239. This

Discussion Paper

20

Full Screen / Esc


ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close


3503

Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

is the opposite of guaiacol, the signal of which is found predominantly at the cluster product. This suggests that the extra methoxy group on syringol compared to guaiacol leads to an enhancement towards greater acidity to be seen predominantly at the transfer product. This shift is observed for many of the ions in the syringol case that are analogous to the guaiacol system. CIMS ions monitored in this system are presented in Table 6. Syringol oxidation chemistry seems to undergo similar routes as guaiacol with analogous ions monitored by the CIMS for the following pathways: (1) hydroperoxide formation, (2) OH adduct formation up to two to three generations, and (3) epoxide and < C8 ring fragment formation from decomposition of the bicyclic radical. These pathways are highlighted in Fig. 9a by selected ions at m/z’s 189 and 271 for OH adducts C8 H10 O4 (S + OH) and C8 H10 O5 (S + 2OH), respectively, m/z 287 for the C8 H10 O6 syringol epoxide (SEPOX), and a C6 H8 O5 ring fragment (FRAG) at m/z 245. A minor contribution from the C8 H12 O6 syringol hydroperoxide at m/z 289 was observed in the CIMS spectra and is not shown. These routes seem to be minor, however, in comparison to those that favor immediate scission of the C8 backbone (Fig. 9). Many of the higher signals in the CIMS are at m/z values that can only be reasonably explained by < C8 molecular formulas. For example, major traces are from ions at m/z 275 (Fig. 9b), likely C7 H10 O6 . A signal was also observed in the CIMS spectra at m/z 291, possibly C7 H10 O7 , and is not shown. There is also evidence of methoxy and hydroxy exchanges and eliminations, providing even more diversity of masses in the CIMS spectra from syringol photooxidation. More detailed analyses on chemical structure would be required to confirm precise mechanisms. For syringol, the immediate loss of carbon through novel chemical pathways (methoxy group elimination or exchange with hydroxy) is more evident in multiple routes than was observed in the case of guaiacol. Figure 10 proposes several possibilities of syringol conversion to compounds with fewer methoxy groups. Each of these pathways

Full Screen / Esc


ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

25

Discussion Paper

20

|

We observe evidence that guaiacol and syringol OH-initiated photooxidation leads to loss of carbon, likely due to unique chemistry involving the methoxy group. While gas-phase aromatic chemistry is not completely understood (Calvert et al., 2002), we propose possible explanations for these novel carbon loss pathways that seem specific to the methoxyphenols. Aihara et al. (1993) studied two pathways in which 1,2dihydroxybenzene (catechol) forms from o-methoxyphenols using a copper(II)-ascorbic acid-dioxygen system: hydroxyl radical attack ipso to the methoxy containing carbon, and H-abstraction from the methoxy group. Hydroxy radical attack ipso to the methoxy containing carbon allows for loss of the methoxy (-OCH3 ) group in the form of methanol (CH3 OH), removing a C atom from the parent molecule. During H-abstraction from the methoxy group, Aihara et al. (1993) propose that the OCH2 radical reacts with the OH radical and then elimination of formaldehyde (HCHO) ensues. In isotopically labeled 3504

|

4.5 Novel chemical pathways for loss of carbon in methoxyphenol systems

Discussion Paper

15

|

10

Discussion Paper

5

has representative ions that also appear in the guaiacol case, though they are not necessarily the same mechanistically. Analogous to the formation of dihydroxybenzene in the case of guaiacol + OH, the early growth of m/z 225 (presumably C7 H8 O3 ) suggests that hydroxy guaiacol (G + OH) may form from syringol + OH (Figs. 9b, 10, pathway a). Another possibility is the complete exchange of both methoxy groups for hydroxy groups, resulting in trihydroxybenzene (THB) monitored at m/z 211 (Figs. 9b, 10, pathway b). Formation of guaiacol is also evident by matching time profiles growing in at m/z 143 and 209 (Figs. 9b, 10, pathway c). Growth of dihydroxybenzene (DHB) at m/z 129 and m/z 195 is observed later in the experiment, likely from conversion of guaiacol (Fig. 10, pathway d). Observation of signal at m/z 257 (the guaiacol epoxide and third OH adduct) supports that there is a guaiacol channel in syringol photooxidation, and is not shown. Though a guaiacol channel exists, the coincident formation of m/z 225 (G + OH) and m/z 211 (THB) with that of guaiacol at m/z 209 is consistent with their direct formation from syringol + OH.

Full Screen / Esc


3505

|

Discussion Paper

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

studies, Aihara et al. (1993) observed transformation of guaiacol to catechol and syringol to hydroxy guaiacol. They also measure yields of these products that might imply ipso addition of OH being a more important route than previously considered compared to ortho- and para-OH addition to the ring. This route could serve as explanation of the observed hydroxy substitutions of methoxy groups in the current systems, but they cannot be verified without measurements of methanol and formaldehyde. While we see ions indicating that methoxy groups may convert to hydroxyl groups, we do not see evidence supporting the addition of or reversible exchange of methoxy groups to the ring. Methoxy radicals may be formed from photolysis of the C−OCH3 bond, if we assume that this bond energy can be proxied by the bond in dimethylether (CH3 −OCH3 ). This bond energy, 351.9 kJ mol−1 (Luo, 2007), translates to an approximate wavelength of 340 nm, exactly where the irradiance spectrum of the light source in our atmospheric chambers peaks. In the event that methoxy radicals are formed, though, it seems unlikely that methoxy radical reaction with the methoxyphenols results in methoxy addition to the ring or replacement of a hydroxy group, especially compared to rapid reaction with O2 . Gomez et al. (2001) studied the reaction rate constants for methoxy radical with cyclohexane, cyclohexene, and 1,4-cyclohexadiene. It was found that methoxy radical reaction with these compounds is likely to result in preferential H abstraction with minor routes of addition to cyclohexene and 1,4-cyclohexadiene. This corroborates the absence of > C7 species in the guaiacol case and > C8 species in the syringol case. Thermodynamic evaluation of the substituent group effects in methoxyphenols can also provide some insight. The following discussion is based on the work presented in Varfolomeev et al. (2010) that examines pairwise substitution effects, and interand intramolecular hydrogen bonds in methoxyphenols and dimethoxybenzenes. Varfolomeev et al. (2010) show that intramolecular hydrogen bonding plays a significant role on ortho-methoxy substituted phenols. This leads to o-methoxyphenols having a lower phenolic O−H bond dissociation energy (BDE) compared to meta isomers and higher than para isomers. This means that the phenolic O−H BDE increases in order

Full Screen / Esc


◦ ∆f Hm (2-methoxyphenol) 5

◦ ∆f Hm (2,6-dimethoxyphenol)

Discussion Paper

→ OH) + 2 × ∆H(H → OCH3 )

+ 2 × (ortho−OH-OCH3 ) + (meta−OCH3 -OCH3 ),

|

where (meta−OCH3 -OCH3 )=0.1 kJ mol−1 from Varfolomeev et al. (2010). After writing a similar expression for 3-methoxybenzene-1,2-diol (hydroxyguaiacol), the difference between the substituent effects for hydroxyguaiacol and syringol is 3506

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

=

◦ ∆f Hm (B) + ∆H(H

Discussion Paper

25

◦ where ∆f Hm (B)= enthalpy of formation of benzene, ∆H(H → OH) = −179.0 kJ mol−1 , the increment in enthalpy for substitution of an H atom by -OH, ∆H(H → OCH3 ) = −1 −150.5 kJ mol , the increment in enthalpy for substitution of an H atom by -OCH3 , −1 and (ortho-OH−OCH3 ) = 4.5 kJ mol , the increment in enthalpy for the pairwise interactions of -OH and -OCH3 ortho to one another. The enthalpy of formation expression begins with the base enthalpy of formation from benzene, then adds the effects of hydroxy or methoxy substitution to the ring. Finally, the pairwise interactions are added, reflecting the stabilizing intramolecular H bonding and destabilizing effect from sterics in the ortho-OH−OCH3 configuration. From comparison of the substitution effects alone, this suggests that H → OH is slightly more favorable than H → OCH3 . For example, this might support substitution of a methoxy group by a hydroxy group in the guaiacol system, as the pairwise ortho effect is minimal. Assuming that the Varfolomeev et al. (2010) formulation can be extended to the case of a trisubstituted benzene, we can write an analogous expression for the case of syringol (2,6-dimethoxyphenol):

|

20

+ (ortho−OH-OCH3 ),

Discussion Paper

15

→ OH) + ∆H(H → OCH3 )

|

10

=

◦ ∆f Hm (B) + ∆H(H

Discussion Paper

the order 4-methoxyphenol < 2-methoxyphenol < 3-methoxyphenol. From the ab initio calculations of Varfolomeev et al. (2010), the enthalpy of formation for 2-methoxyphenol (guaiacol) is expressed below:

Full Screen / Esc


5

| Discussion Paper

20

Discussion Paper

15

|

10

Discussion Paper

−1

−30 kJ mol , in slight favor of hydroxyguaiacol. The pairwise effect of (ortho-OH-OH) was not calculated by Varfolomeev et al. (2010), but assuming that it is less sterically hindered compared to (ortho-OH-OCH3 ) and is stabilized by intramolecular hydrogen −1 bonding similar to 1,2-dimethoxybenzene, we assume it to be < 4.5 kJ mol . Due to the combined favorability of energetics for the substituent effects and the pairwise effects, this can help explain why some of the syringol rapidly converts to hydroxyguaiacol and even trihydroxybenzene. The “phenolic route”, involving OH addition at the ortho position to the main electrondonating substituent group has been cited as being the main channel responsible for SOA formation in many aromatic systems (Calvert et al., 2002; Johnson et al., 2005; Nakao et al., 2011). However, with the additional methoxy groups, OH attack alpha to the methoxy groups becomes competitive and changes the potential for maintaining aromaticity in the methoxyphenol systems. It is possible that the extra methoxy group in syringol inhibits OH attack that is typically favored ortho to the hydroxyl substituted carbon in other systems that generate SOA via this route. For the other compounds, in order to achieve the degree of oxidation of the aerosol, it appears that at least two steps of reaction are needed, but that these steps occur fairly rapidly. If subsequent OH reactions are even slower due to the extra methoxy group in the case of syringol, then conversion to SOA may not be as complete as with the other two compounds over the duration of the experiments reported here. 4.6 Chemical basis for observed yields

ACPD 13, 3485–3532, 2013



Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Abstract

|

3507

Discussion Paper

25

The AMS high-resolution spectra for the methoxyphenol systems are distinct. Initial aerosol growth in the guaiacol system is marked by the exact mass ion C4 H3 O+ 2 . Later + + the aerosol growth is characterized by the ions C2 H3 O , and C2 H5 O2 . In the case + + of syringol, initial growth is characterized by C5 H2 O2 and C7 H9 O3 ions, followed by + + + C5 H5 O4 , and then by C5 H2 O4 and C2 H4 O3 . This suggests that guaiacol SOA is char-

Full Screen / Esc


3508

|

Discussion Paper

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

acterized by smaller carbon number and less oxygenated fragments than the case of syringol. The characteristic ions from the AMS spectra for syringol SOA seem counter-intuitive for understanding why the syringol SOA yield is lower than that of guaiacol. Syringol has more carbon and oxygen to begin with and these ions are larger, more oxygenated fragments than in guaiacol. However, if we return to the gas-phase comparison of the characteristic trends in the guaiacol (Fig. 7) and syringol (Fig. 9) systems, one notes that many of the major products from syringol photooxidation peak later than their analogs in the guaiacol system. Further, there is no analogous peak in the guaiacol system to the m/z 275 unique to the syringol system. Since this is a major product of gas-phase syringol photooxidation and it peaks > 4×106 molec cm−3 h of OH exposure 6 −3 compared to guaiacol ions that peak generally within 3 × 10 molec cm h, it acts like a gas-phase carbon reservoir. That is, the signal at m/z 275 is much more significant than the more efficient SOA formers at m/z 129 (dihydroxybenzene, not shown) and m/z 209 (guaiacol) in Fig. 9b. AMS elemental analyses of SOA from these systems as reported in Chhabra et al. (2011) suggest that the majority of oxygenation is derived from organic acid functionalities: 77 % for phenol, 61 % for guaiacol, and 59 % for syringol. This is consistent with the necessity of further oxidation of acidic fragments to explain the presence of highly oxidized species observed in the guaiacol filter analyses. The decrease in oxygenation derived from organic acid functionalities from phenol to the methoxphenol systems may reflect the oxygen reserved in OH adduct and aromatic retaining pathways, especially in the case of syringol (Fig. 10). This may also partially explain why the syringol SOA yield is lower if acid formation drives the SOA growth. At similar OH exposures, the syringol system still has not developed an acid signal that tracks well with the SOA growth, as m/z 185 does in the phenol system (Fig. 3) and m/z 149 does in the guaiacol system (Fig. 7). The m/z 245 fragment lags the SOA growth in the syringol system (Fig. 9a). This could be due to the lack of OH addition to the ring on syringol in critical positions that lead to SOA formation via ring-opening acid formation.

Full Screen / Esc


5

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close


3509

Discussion Paper

25

|

20

Discussion Paper

15

|

10

While the current experiments were conducted without the addition of NOx , the chemistry elucidated under these low-NOx conditions is expected to be relevant for typical atmospheric conditions. For phenol photooxidation in the presence of NOx , Olariu et al. (2002) measured yields of 0.8 catechol (1,2-dihydroxybenzene), 0.037 1,4benzoquinone, and 0.058 2-nitrophenol. However, according to kinetic data and yield comparisons for nitrophenol presented in Berndt and Boge (2003), it is likely that this nitro-product formation can be biased due to sufficiently high NO2 (. 800 ppb) concentrations. Berndt and Boge (2003) point out that for atmospheric conditions with NO2 of approximately 20 ppb, it is probable that phenoxy radicals also react with O3 as well as NO and NO2 . This would result in more minor nitrophenol yields in the atmosphere. Thus, because OH addition dominates over H abstraction, and subsequent O2 addition to the OH radical adduct is rapid, it is more likely that in the atmosphere, SOA primarily forms via pathways involving higher-generation OH adducts and their respective routes to oxygenated fragments. This is consistent with the chemistry presented in this work. Though we did not observe appreciable evidence of gas-phase hydroperoxides, they may be rapidly incorporated into the particle phase and contribute to peroxide formation, as postulated by Johnson et al. (2005) and observed by Sato et al. (2007) for the case of toluene photooxidation. Sato et al. (2007) also find similar species in the particle-phase under [NO]0 = 0.2 and 1 ppm, still citing O2 addition to the OH-aromatic adduct as the major channel contributing to SOA formation. In the presence of moderate NOx , we would expect the major gas-phase species to be the same as those presented here, with only a minor contribution from nitrogencontaining products. Still, for the studied compounds, novel routes of reaction of alkylperoxy radicals under these low-NOx conditions may still result in product distributions expected under higher NOx conditions. First, the aromatic peroxy radicals in the studied systems may preferentially decompose to regenerate OH via novel RO2 + HO2 chemistry (Birdsall et al., 2010). This is a possible explanation for the observation of

Discussion Paper

5 Atmospheric relevance

Full Screen / Esc


ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close


3510

Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

ring-opened acids in phenol and guaiacol. Second, generation of carbonyls via novel rearrangements of ether peroxy radicals (Orlando and Tyndall, 2012), relevant for guaiacol and syringol, would further make the product distributions less distinct from alkoxy radical pathways expected under high-NOx chemistry. These observations warrant caution when conducting experiments in the presence of NOx for aromatic compounds, as derived aerosol yields may be based on chemistry non-representative of the atmosphere. Klotz et al. (2002) found that at high-NOx conditions (hundreds of ppb to ppm) one must also start to consider reactions of NOx with the hydroxy radical adduct. At sufficiently high NOx concentrations, the gas-phase chemistry can generate higher yields of nitroaromatics as compared to the OH aromatic adduct (Koch et al., 2007; Nishino et al., 2008). Nitroaromatics can serve to enhance aerosol yields if sufficient nitro-containing functionalities are achieved or to act as gas-phase carbon reservoirs and depress aerosol yields. Hydroxyl groups will lead to a vapor pressure lowering more than that associated with nitro groups, but sufficient nitro groups could lead to incorporation to the particle phase. Owing to the lower OH reactivity of the molecule containing a nitro group as compared to the comparable molecule containing a hydroxyl group (Kwok and Atkinson, 1995), one might also find that more OH is necessary in the presence of NOx to attain further gas-phase development to more highly oxidized species that contribute to SOA formation. While the OH-initiated photooxidation of aromatics in general is complex (Calvert et al., 2002), methoxyphenols seem to follow some steps of the general mechanism developed for simpler aromatics. We have qualitatively presented gas-phase trends that give some insight into the chemistry of SOA formation. Though, more complete mechanism development would be enhanced by the availability of authentic standards to solidify mass assignments and more detailed structural information. For example, the structural identity of the ion at m/z 275 in the syringol system remains elusive. Calculation of quantitative gas-phase yields would benefit from additional kinetic data pertaining to some of the complex intermediates.

Full Screen / Esc


3511

|

Discussion Paper

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

Carbon loss via the methoxy groups in guaiacol and syringol appears to be a feasible route to describe the gas-phase product distributions. While the chemistry of syringol is complex, this compound may be a better model system to represent the mixture of methoxy and phenolic compounds since it displays chemistry from both classes. Syringol, however, does not generate as much SOA as these other systems. This may be a result of the unique OCH3 −OH−OCH3 pairwise effects that hinder the typical phenolic pathway responsible for SOA formation. Future studies to investigate this effect might start with methoxyphenols of different substituted positions relative to the hydroxy group to see the effect on SOA yields. For example, using a methoxyphenol where at least one or two methoxy groups are not ortho to the hydroxy group would serve to further investigate the importance of OH addition ortho to the hydroxy group in these compounds, as 1,2-dihydroxybenzene is the major gas-phase product and SOA fomer from phenol. Also, 2,5-dimethoxyphenol might also indicate if OH attack is preferred at the 6-position, again ortho to the hydroxy group. Such studies would require more detailed analyses that provide greater structural analysis for the gas-phase products as well as unique tracers for fragmentation patterns that would clarify the chemistry. Detailed study of the gas-phase products from the OH-initiated photooxidation of methoxybenzene might also be informative for understanding the proposed carbon loss associated with methoxy groups in the guaiacol and syringol systems. If phenol is a major product, this has implications on understanding the chemical fate of methoxyphenollike compounds in the atmosphere. For example, Lauraguais et al. (2012) suggest that syringol is too reactive with OH (1.8 h) to be a relevant tracer in the atmosphere for woodsmoke emissions and that it results in a very minor SOA yield. However, the chemical analyses presented in this study suggest that syringol can efficiently convert to guaiacol and hydroxylated benzenes that are longer lived in the atmosphere and potentially have larger SOA yields. This can be analogous to the isoprene photochemical cascade, where it is the products of isoprene photooxidation that have greater SOA forming potential (Kroll et al., 2006). The syringol conversion to guaiacol also has im-

Full Screen / Esc


5

10

|

3512

Discussion Paper

30

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

25

Discussion Paper

20

|

15

Aihara, K., Urano, Y., Higuchi, T., and Hirobe, M.: Mechanistic studies of selective catechol formation from o-methoxyphenols using a copper(II) ascorbic-acid dioxygen system, J. Chem. Soc. Perk. T., 2, 2165–2170, doi:10.1039/p29930002165, 1993. 3504, 3505 Aiken, A. C., DeCarlo, P. F., and Jimenez, J. L.: Elemental analysis of organic species with electron ionization high-resolution mass spectrometry, Anal. Chem., 79, 8350–8358, 2007. 3493 Aiken, A. C., DeCarlo, P. F., Kroll, J. H., Worsnop, D. R., Huffman, J. A., Docherty, K. S., Ulbrich, I. M., Mohr, C., Kimmel, J. R., Sueper, D., Sun, Y., Zhang, Q., Trimborn, A., Northway, M., Ziemann, P. J., Canagaratna, M. R., Onasch, T. B., Alfarra, M. R., Prevot, A. S. H., Dommen, J., Duplissy, J., Metzger, A., Baltensperger, U., and Jimenez, J. L.: O/C and OM/OC ratios of primary, secondary, and ambient organic aerosols with high-resolution time-of-flight aerosol mass spectrometry, Environ. Sci. Technol., 42, 4478–4485, 2008. 3493 Allan, J. D., Delia, A. E., Coe, H., Bower, K. N., Alfarra, M. R., Jimenez, J. L., Middlebrook, A. M., Drewnick, F., Onasch, T. B., Canagaratna, M. R., Jayne, J. T., and Worsnop, D. R.: A generalised method for the extraction of chemically resolved mass spectra from Aerodyne aerosol mass spectrometer data, J. Aerosol Sci., 35, 909–922, 2004. 3493 Bahreini, R., Keywood, M. D., Ng, N. L., Varutbangkul, V., Gao, S., Flagan, R. C., Seinfeld, J. H., Worsnop, D. R., and Jimenez, J. L.: Measurements of secondary organic aerosol from oxidation of cycloalkenes, terpenes, and m-xylene using an Aerodyne aerosol mass spectrometer, Environ. Sci. Technol., 39, 5674–5688, 2005. 3493 Berndt, T. and Boge, O.: Gas-phase reaction of OH radicals with phenol, Phys. Chem. Chem. Phys., 5, 342–350, doi:10.1039/b208187c, 2003. 3496, 3509

Discussion Paper

References

|

Acknowledgements. This work was supported by the US Department of Energy grants DEFG02-05ER63983 and DE-SC 0006626 and US Environmental Protection Agency (EPA) STAR Research Agreement No. RD-833749. Lindsay Yee and Christine Loza were supported by National Science Foundation Graduate Research Fellowships.

Discussion Paper

plications for using these compounds as specific tracers for fuel type (hardwood vs. softwood). Thus, care must be taken in selecting one or more surrogate species for use in modeling aerosol yields from biomass burning emissions in the atmosphere.

Full Screen / Esc


3513

|

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

30

Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

Birdsall, A. W., Andreoni, J. F., and Elrod, M. J.: Investigation of the role of bicyclic peroxy radicals in the oxidation mechanism of toluene, J. Phys. Chem. A, 114, 10655–10663, doi:10.1021/jp105467e, 2010. 3498, 3499, 3509 Bloss, C., Wagner, V., Bonzanini, A., Jenkin, M. E., Wirtz, K., Martin-Reviejo, M., and Pilling, M. J.: Evaluation of detailed aromatic mechanisms (MCMv3 and MCMv3.1) against environmental chamber data, Atmos. Chem. Phys., 5, 623–639, doi:10.5194/acp-5-6232005, 2005. 3499, 3501 Bond, T. C., Streets, D. G., Yarber, K. F., Nelson, S. M., Woo, J. H., and Klimont, Z.: A technology-based global inventory of black and organic carbon emissions from combustion, J. Geophys. Res.-Atmos., 109, D14203, doi:10.1029/2003JD003697, 2004. 3488 Calvert, J. G., Atkinson, R., Becker, K. H., Kamens, R. M., Seinfeld, J. H., Wallington, T. J., and Yarwood, G.: The Mechanisms of Atmospheric Oxidation of Aromatic Hydrocarbons, Oxford University Press, Inc, New York, USA, 2002. 3499, 3501, 3504, 3507, 3510, 3517 Chan, A. W. H., Kroll, J. H., Ng, N. L., and Seinfeld, J. H.: Kinetic modeling of secondary organic aerosol formation: effects of particle- and gas-phase reactions of semivolatile products, Atmos. Chem. Phys., 7, 4135–4147, doi:10.5194/acp-7-4135-2007, 2007. 3494, 3495 Chhabra, P. S., Ng, N. L., Canagaratna, M. R., Corrigan, A. L., Russell, L. M., Worsnop, D. R., Flagan, R. C., and Seinfeld, J. H.: Elemental composition and oxidation of chamber organic aerosol, Atmos. Chem. Phys., 11, 8827–8845, doi:10.5194/acp-11-8827-2011, 2011. 3494, 3508 Cocker, D. R., Flagan, R. C., and Seinfeld, J. H.: State-of-the-art chamber facility for studying atmospheric aerosol chemistry, Environ. Sci. Technol., 35, 2594–2601, 2001. 3489 Coeur-Tourneur, C., Cassez, A., and Wenger, J. C.: Rate coefficients for the gas-phase reaction of hydroxyl radicals with 2-Methoxyphenol (guaiacol) and related compounds, J. Phys. Chem. A, 114, 11645–11650, doi:10.1021/jp1071023, 2010. 3496, 3517 DeCarlo, P. F., Kimmel, J. R., Trimborn, A., Northway, M. J., Jayne, J. T., Aiken, A. C., Gonin, M., Fuhrer, K., Horvath, T., Docherty, K. S., Worsnop, D. R., and Jimenez, J. L.: Field-deployable, high-resolution, time-of-flight aerosol mass spectrometer, Anal. Chem., 78, 8281–8289, 2006. 3493 Dills, R. L., Zhu, X. Q., and Kalman, D. A.: Measurement of urinary methoxyphenols and their use for biological monitoring of wood smoke exposure, Environ. Res., 85, 145–158, 2001. 3488

Full Screen / Esc


3514

|

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

30

Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

Fine, P. M., Cass, G. R., and Simoneit, B. R. T.: Chemical characterization of fine particle emissions from fireplace combustion of woods grown in the northeastern United States, Environ. Sci. Technol., 35, 2665–2675, 2001. 3488 Gomez, N., Henon, E., Bohr, F., and Devolder, P.: Rate constants for the reactions of CH3 O with cyclohexane, cyclohexene, and 1,4-cyclohexadiene: Variable temperature experiments and theoretical comparison of addition and H-abstraction channels, J. Phys. Chem. A, 105, 11204–11211, doi:10.1021/jp010204h, 2001. 3505 Hawthorne, S. B., Krieger, M. S., Miller, D. J., and Mathiason, M. B.: Collection and quantitation of methoxylated phenol tracers for atmospheric-pollution from residential wood stoves, Environ. Sci. Technol., 23, 470–475, 1989. 3488 Hawthorne, S. B., Miller, D. J., Langenfeld, J. J., and Krieger, M. S.: PM-10 high-volume collection and quantification of semivolatile and nonvolatile phenols, methoxylated phenols, alkanes, and polycyclic aromatic-hydrocarbons from winter urban air and their relationship to wood smoke emmisions, Environ. Sci. Technol., 26, 2251–2262, 1992. 3488 Ito, A. and Penner, J. E.: Historical emissions of carbonaceous aerosols from biomass and fossil fuel burning for the period 1870–2000, Global Biogeochem. Cy., 19, GB2028, doi:10.1029/2004GB002474, 2005. 3488 Johnson, D., Jenkin, M., Wirtz, K., and Martin-Reviejo, M.: Simulating the formation of secondary organic aerosol from the photooxidation of aromatic hydrocarbons, Environ. Chem., 2, 35–48, doi:10.1071/EN04079, 2005. 3499, 3507, 3509 Justesen, U.: Collision-induced fragmentation of deprotonated methoxylated flavonoids, obtained by electrospray ionization mass spectrometry, J. Mass Spectrom., 36, 169–178, doi:10.1002/jms.118, 2001. 3502 Kautzman, K. E., Surratt, J. D., Chan, M. N., Chan, A. W. H., Hersey, S. P., Chhabra, P. S., Dalleska, N. F., Wennberg, P. O., Flagan, R. C., and Seinfeld, J. H.: Chemical composition of gas- and aerosol-phase products from the photooxidation of naphthalene, J. Phys. Chem. A, 114, 913–934, 2010. 3493 Keywood, M. D., Varutbangkul, V., Bahreini, R., Flagan, R. C., and Seinfeld, J. H.: Secondary organic aerosol formation from the ozonolysis of cycloalkenes and related compounds, Environ. Sci. Technol., 38, 4157–4164, 2004. 3489 Klotz, B., Volkamer, R., Hurley, M., Andersen, M., Nielsen, O., Barnes, I., Imamura, T., Wirtz, K., Becker, K., Platt, U., Wallington, T., and Washida, N.: OH-initiated oxidation of benzene –

Full Screen / Esc


3515

|

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

| Discussion Paper

30

Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

Part II. influence of elevated NOx concentrations, Phys. Chem. Chem. Phys., 4, 4399–4411, doi:10.1039/b204398j, 2002. 3510 Koch, R., Knispel, R., Elend, M., Siese, M., and Zetzsch, C.: Consecutive reactions of aromaticOH adducts with NO, NO2 and O2 : benzene, naphthalene, toluene, m- and p-xylene, hexamethylbenzene, phenol, m-cresol and aniline, Atmos. Chem. Phys., 7, 2057–2071, doi:10.5194/acp-7-2057-2007, 2007. 3510 Kroll, J. H. and Seinfeld, J. H.: Representation of secondary organic aerosol laboratory chamber data for the interpretation of mechanisms of particle growth, Environ. Sci. Technol., 39, 4159– 4165, 2005. 3494 Kroll, J. H., Ng, N. L., Murphy, S. M., Flagan, R. C., and Seinfeld, J. H.: Secondary organic aerosol formation from isoprene photooxidation, Environ. Sci. Technol., 40, 1869–1877, doi:10.1021/es0524301, 2006. 3511 Kwok, E. S. and Atkinson, R.: Estimation of hydroxyl radical reaction rate constants for gasphase organic compounds using a structure-reactivity relationship: an update, Atmos. Environ., 29, 1685–1695, doi:10.1016/1352-2310(95)00069-B, 1995. 3510 Lauraguais, A., Coeur-Tourneur, C., Cassez, A., and Seydi, A.: Rate constant and secondary organic aerosol yields for the gas-phase reaction of hydroxyl radicals with syringol (2,6dimethoxyphenol), Atmos. Environ., 55, 43–48, doi:10.1016/j.atmosenv.2012.02.027, 2012. 3494, 3511, 3517 Luo, Y. R.: Comprehensive Handbook of Chemical Bond Energies, CRC Press, Boca Raton, FL, 2007. 3505 Naeher, L. P., Brauer, M., Lipsett, M., Zelikoff, J. T., Simpson, C. D., Koenig, J. Q., and Smith, K. R.: Woodsmoke health effects: a review, Inhal. Toxicol., 19, 67–106, 2007. 3488 Nakao, S., Clark, C., Tang, P., Sato, K., and Cocker III, D.: Secondary organic aerosol formation from phenolic compounds in the absence of NOx , Atmos. Chem. Phys., 11, 10649–10660, doi:10.5194/acp-11-10649-2011, 2011. 3494, 3497, 3498, 3507 Ng, N. L., Kroll, J. H., Keywood, M. D., Bahreini, R., Varutbangkul, V., Flagan, R. C., Seinfeld, J. H., Lee, A., and Goldstein, A. H.: Contribution of first- versus second-generation products to secondary organic aerosols formed in the oxidation of biogenic hydrocarbons, Environ. Sci. Technol., 40, 2283–2297, 2006. 3495 Nishino, N., Atkinson, R., and Arey, J.: Formation of nitro products from the gas-phase OH radical-initiated reactions of toluene, naphthalene, and biphenyl: effect of NO2 concentration, Environ. Sci. Technol., 42, 9203–9209, doi:10.1021/es802046m, 2008. 3510

Full Screen / Esc


ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close


3516

Discussion Paper

25

|

20

Discussion Paper

15

|

10

Discussion Paper

5

Olariu, R. I., Klotz, B., Barnes, I., Becker, K. H., and Mocanu, R.: FTIR study of the ring-retaining products from the reaction of OH radicals with phenol, o-, m-, and p-cresol, Atmos. Environ., 36, 3685–3697, 2002. 3496, 3509 Orlando, J. J. and Tyndall, G. S.: Laboratory studies of organic peroxy radical chemistry: an overview with emphasis on recent issues of atmospheric significance, Chem. Soc. Rev., 41, 6294–6317, doi:10.1039/c2cs35166h, 2012. 3510 Pye, H. O. T. and Seinfeld, J. H.: A global perspective on aerosol from low-volatility organic compounds, Atmos. Chem. Phys., 10, 4377–4401, doi:10.5194/acp-10-4377-2010, 2010. 3487 Sato, K., Hatakeyama, S., and Imamura, T.: Secondary organic aerosol formation during the photooxidation of toluene: NOx dependence of chemical composition, J. Phys. Chem. A, 111, 9796–9808, doi:10.1021/jp071419f, 2007. 3509 Schauer, J. J., Kleeman, M. J., Cass, G. R., and Simoneit, B. R. T.: Measurement of emissions from air pollution sources. 3. C-1-C-29 organic compounds from fireplace combustion of wood, Environ. Sci. Technol., 35, 1716–1728, 2001. 3488 Simpson, C. D. and Naeher, L. P.: Biological monitoring of wood-smoke exposure, Inhal. Toxicol., 22, 99–103, 2010. 3488 St. Clair, J. M., McCabe, D. C., Crounse, J. D., Steiner, U., and Wennberg, P. O.: Chemical ionization tandem mass spectrometer for the in situ measurement of methyl hydrogen peroxide, Rev. Sci. Instrum., 81, 94–102, 2010. 3491 ´ ´ Surratt, J. D., Gomez-Gonz alez, Y., Chan, A. W. H., Vermeylen, R., Shahgholi, M., Kleindienst, T. E., Edney, E. O., Offenberg, J. H., Lewandowski, M., Jaoui, M., Maenhaut, W., Claeys, M., Flagan, R. C., and Seinfeld, J. H.: Organosulfate formation in biogenic secondary organic aerosol, J. Phys. Chem. A, 112, 8345–8378, 2008. 3491, 3492 Varfolomeev, M. A., Abaidullina, D. I., Solomonov, B. N., Verevkin, S. P., and Emel’yanenko, V. N.: Pairwise substitution effects, inter- and intramolecular hydrogen bonds in methoxyphenols and dimethoxybenzenes. thermochemistry, calorimetry, and firstprinciples calculations, J. Phys. Chem. B, 114, 16503–16516, doi:10.1021/jp108459r, 2010. 3505, 3506, 3507

Full Screen / Esc


Discussion Paper |

OH

182

OH

O3 CH

CH3

205

OH

O O H3C H3C

Syringol Syringol Syringol Syringol

OH O OH O3 CH

OH O OH O3 CH O O3 CH

CH3

260

182

1820.351 182

0.351 0.351

13, 3485–3532, 2013


Title Page

◦

0.351 2.7 ± 0.25 at 252.7C±(Calvert 0.25 atet25 Calvert et al. (2002) al., C, 2002) ◦

2.7 ± 0.25 at 25 ◦ C (Calvert et al., 2002) 2.7 ± 0.25 at 25 ◦ C (Calvert et al., 2002)

◦

◦ 0.13 7.53 ± 0.41 at7.53 21 ±±2 0.41 C (Coeur-Tourneur al., 2010) ± 2 C, et Coeur-Tourneur 205 205 0.13 0.137.53 ± 0.41 at 21 ± 2 ◦at C 21 (Coeur-Tourneur et al., 2010) et al. (2010) 205 0.13 7.53 ± 0.41 at 21 ± 2 ◦ C (Coeur-Tourneur et al., 2010)

0.0062 9.66 ± 1.11 at 21 ± 2 ◦ C (Lauraguais et al., 2012) ◦ 260 260 0.00620.0062 9.66 ± 1.11 at ± 211.11 ± 2 ◦ C (Lauraguais et al., 2012) et al. (2012) ◦ ± 2 C, Lauraguais 260 0.0062 9.669.66 ± 1.11 at 21 at ± 221 C (Lauraguais et al., 2012)

Discussion Paper

Guaiacol Guaiacol Guaiacol Guaiacol

H3C

OH

|

Phenol Phenol Phenol Phenol

kO H × 10−11 −11kOH × 10−11 kO H × 10 −11 −3 −1 H(molec (molec cm−3ksO−1 )× 10 cm s ) (molec cm−3 s−1 ) −1 −3 (molec cm s )

Discussion Paper

Table 1. Chemical properties. Table 1. Chemical Properties Table 1. Chemical Properties Table 1. Chemical Properties Compound Structure V.P. @ Compound Structure Boiling Pt.Boiling Pt.25 ◦ CV.P.◦ @ 25 ◦ C Compound Structure Boiling Pt. V.P. @ 25 C ◦ ◦ ◦ Compound Structure @ 25Hg) C ( (mm C)Pt.Hg)V.P.(mm ( C) ◦ Boiling ( C) ◦ (mm Hg) ( C) (mm Hg) OH

ACPD

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Abstract

Discussion Paper |

3517

Full Screen / Esc


Discussion Paper |

[Org]0 (ppb)

[Org]f (ppb)

[NO2 ]0 (ppb)

[NO]0 (ppb)

V0 µm3 cm−3

Vf µm3 cm−3

Yield

29 Jan 2 Feb 4 Feb 6 Feb

guaiacol guaiacol guaiacol guaiacol

66.3 5.9 12.4 45.5

13.4 < LDL∗ < LDL∗ 4.1

< LDL∗ < LDL∗ < LDL∗ < LDL∗

< LDL∗ < LDL∗ < LDL∗ 5

18.2 16.4 13.6 12.9

120.0 25.0 31.0 85.0

0.49 0.46 0.44 0.50

11 Feb 15 Feb 17 Feb 20 Feb

phenol phenol phenol phenol

47.6 10.0 73.9 101.9

9.9 2.1 14.4 18.8

< LDL∗ ∗ < LDL ∗ < LDL < LDL∗

6 5 ∗ < LDL 5

16.0 11.4 12.0 10.0

58.0 20.0 44.0 69.0

0.44 0.40 0.25 0.24

10 Mar 15 Mar 29 Mar

syringol syringol syringol

185.1 49.5 112.9

< LDL∗ < LDL∗ < LDL∗

7 < LDL∗ 9

< LDL∗ < LDL∗ < LDL∗

11.0 14.2 11.7

325.0 67.0 174.0

0.37 0.25 0.34

Discussion Paper

Organic

|

13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

∗

Date (2010)

Discussion Paper

Table 2. Experimental conditions.

ACPD

Below lower detection limit.

Discussion Paper |

3518

Full Screen / Esc


Discussion Paper | Discussion Paper

13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close


3519

|

Table 3.product, Proposed structures for CIMS ions in the phenol low-NOxx system. C and T indicate the cluster and transfer respectively. transfer product, respectively. Table 3. Proposed structures for CIMS ions in the phenol low-NO system. C and T indicate the cluster and x transfer x Table 3.product, Proposed structures Chemical for CIMS CIMS Formula ions in in the the Proposed phenol low-NO low-NO system. C and andshown) T indicate indicate the the cluster cluster and and transfer product, respectively. x system. Observed m/z respectively. Product Chemical Formula Proposed Structure (one isomer isomer shown) Chemical Pathway Pathway Table 3. Proposed structures for ions phenol C T x Observed m/z Product Structure (one Chemical Observed m/z Product Chemical Formula Proposed Structure (one isomer shown) Chemical Pathway transfer product, respectively. Observed Product Chemical Proposed Structure Chemical OH Observed m/z Product Chemical Formula Proposed Structure (one isomer shown) Chemical OH transfer product, respectively. Observed m/z Product Chemical Formula Proposed Structure (one isomer shown) Chemical Pathway Pathway OH transfer product, respectively. OH Observed m/z Product Chemical Formula Proposed Structure (one isomer shown) Chemical Pathway m/zObserved Formula (oneStructure isomer OH OH Observed m/z Product Product Chemical Formula Proposed Structure (oneshown) isomer shown) shown) Pathway Chemical Chemical Pathway Chemical Proposed (one isomer Pathway 179 m/z C C66 H HFormula O phenol 6O 179 C C phenol 179 C C phenol 6 H6 6O OH OH OH OHOH OH 179 C C H O phenol OH 6 6 179 C C66 H66 O phenol OH OH OH OH OH 179 C H phenol OH 6O OH 179 C H6H O622 O phenol 179 179 C TTTCCCaaa C6666666H phenol 129 C H DHB = =phenol phenol + + OH OH 6O 66 C O OH 129 C DHB phenol OH 6H 129 C H O DHB = phenol + OH 66O 2 OH OH OHOH a OH OH 129 T C DHB = phenol OHOH OH 129 Taa C666 H H666 O O222 DHB = phenol + + OH OH OHOH HO OH HO OH HO OH OH OH 129 C DHB = phenol + OH OH 6 6 DHB = phenol + OH 129 129 TaTTTCCCaaaa 6H 6O HO OH 129 DHB == phenol +OH OH 211 CC H O6232322O2 THB= =phenol DHB ++ OH 6 6 DHB OH HO OH 6 66H 211 C O THB DHB + 6 HO OH 211 C H O THB = DHB + OH 6H 3 OH OH OH OH HO 211 C C THB = DHB + OH OH OH HO OH 211 C C666 H H666 O O333 THB = DHB + OH HO OH HO OH HO OH OH OH 211 C H O THB DHB OH OH 211 211 C CCC C666H THB = DHB +== DHB OH+++ OH 6 6 HO OH 211 C H O6333O3 THB DHB OH 6H 6O C THB HO OH 227 4HB = THB OH HO 227 C C 4HB = + OH OH 227 C C666 H H666 O O3444 4HB = THB THB + OH OH OH OH OH HO OH OH HO 227 C C 4HB OH HO 227 C C666 H H666 O O444 4HB = = THB THB + + OH OH HO OH OH O 4HB = THB +==OH 227 227 C CCC CH O 227 C O 4HB THB + OH OH O 6 OH 6H O 6 227 C666H H O6444 4 4HB = THB + + OH OH OH 6O O C 4HB THB O O OH 145 T C666 H H66 O O43 ring opening opening acid acid OH O 145 T C ring O 145 T C ring opening acid 6 H6 6 O3 3 O OH O O O O O OH C H66H O3 ring O 6 OH O 145 CC ring opening opening acid 145 145 T TT ring opening acid acid O 6 O O OH 6H O 6 6 O633 O3 O O OH O OH O O O O OH 145 T C H O ring opening acid O OH OHO OH OH ring opening acid 161 T C666 H H666 O O343433 O OH 145 OH 161 OH O 145 T C ring opening acid 161 O OH 4 O OH O OH OH O OH OH O ring opening acid T C H O OH O O OH 161 161 T C H O ring opening acid 6 6 4 ring opening acid 161 T C66 H O OH OH O 6 66 O644 4 O OH O OH OH O OH OH OH ring opening acid 161 T C H O OHO OH O OH OH 177 T C666 H H666 O O454544 ring opening opening acid acid O 161 OH 177 OH OH O ring 161 T C 177 O 5 OH OH O OH OH O OH O OH ring opening acid acid 177 177 T C H O OH O T C ring opening O OH 6 666 O 177 T C666 H H O6555 5 ring opening acid O OH OH O O OH OH OH O OH 177 T C H O ring opening acid OH O OH O 177 Tb C6666H H6666O O5555 ring opening opening acid acid OH O 177 C ring bCT O b O OH b 185 C H O ring fragment fragment OH O 4 4 3 C O ring 185 185 C CCb ring fragment 4 O 185 CC H O433 O3 ring fragment 4H O OH 4 44H O OH O O OH O OH O b 185 C C ring OH O OH O 185 Cb C444 H H444 O O333 ring fragment fragment O O O OH O O O OH O ring fragment fragment 135 CC H O444 O4 135 135 TcCTTTcccbbbb ring fragment OH O OH O 4H 4O ring C O OH OH ring fragment 135 C H O 4 44H O 185 OH O O OH OH C4444H H O4333 ring fragment fragment OH O 4 185 Ccc 4O O OH O 185 C C ring 4 4 3 O O OH ring fragment 135 T C OO OH OH ring fragment 135 Tc C444 H H444 O O444 OH OH O OH O O HO OH O OH ring fragment 107 107 T C H O O 107 T C H O ring fragment HO OH O c 3 4 3 Tc C H ring fragment 3 44 O HO O O OH 107 C H O ring fragment O 135 T O OH OH ring fragment fragment C33444H H O433444 3 OH 4 135 TTcc OH 4O ring 135 T C HO OH 107 T C ring HO OH O 107 T C4333 H H4444 O O4333 ring fragment fragment HO O a O OH a O a m/z m/z 195 is also present as C H O , but is lower signal than at m/z 129. a 6 6 2 195 is also present as C H O , but is lower signal than at m/z 129. 2 m/z107 195 is alsopresent present asas C66C H66CO but isbut lower signal than at m/z 129.OH 2 ,4 HO m/za195 is also H O , is lower signal than at m/z 129. T H O ring fragment HO OH 3 3 6 6 44O HO OH 107 is also present T as C6 HC C333H H O2333 is lower signal than at m/z ring fragment fragment HO OH a b m/z107 T 4but a b m/z 195 195 is also present as Ois but lowerwhich signalis at m/z 129. 129.in b The transfer product at C C44C H6644H O66633O is222 ,,at at m/zis119, 119, which isthan not monitored monitored in low-NO low-NOxx conditions conditions because because it it is isring the cluster cluster product product of of H H22 O O2 ... b The transfer product at m/z not the The transfer product at C H O at m/z 119, which not monitored in low-NO because it is the cluster product of H 4O 3 is x conditions 2 O2 2 Thebaaatransfer product at C44H H at m/z 119, is which is not monitored in low-NO 46O 32 ,is x conditions m/z 195 is also present as C H O but is lower signal than at m/z 129. b c The 6 a transfer product at C H O is at m/z 119, which is not monitored in low-NO conditions because it is the cluster b c 6 6 2 4 4 3 x 195 129.in low-NOxx conditions because it is the cluster product transfer product at product C44C H446644H O446633O m/z 119, which not monitored product of of H H222 O O222 .. c The m/zit201 201 is also present as C H Oisof but is lower signalisthan than at m/z m/z 135. 135. 2,,at 4 195 129. m/z is also present as but is lower signal at 2 4 because is the cluster H O . m/z 201 is also present as C H O , but is lower signal than at m/z 135. 4 4 4 2 2 b b c c The transfer product at C H O is at m/z 119, which is not monitored in low-NO conditions because it is the cluster product of H O 4 x m/z is present H but is 119, lower signal at 135. 4 x The 201 transfer product at as Cas H4444444C O44443333O is4444,,at at m/z 119, which isthan not monitored inatlow-NO low-NO conditions because because it it is is the the cluster cluster product product of of H H2222O O2222... m/z 201 is also also present as C H O but lower signal than at m/z m/zthan 135.in 4C x conditions m/z bccb201 is also present His O iswhich lower signal m/z 135. The transfer product at C H O m/z is not monitored 4 x 4 ,isbut c c 201 is also present as C H O , but is lower signal than at m/z 135. 4 4 4 cc m/z 4 4 4 m/z 201 is also present as C H O , but is lower signal than at m/z 135. m/z 201 is also present as C44H44O44, but is lower signal than at m/z 135.

Discussion Paper

Table 3. Proposed structures for CIMS ions in the phenol low-NOx system. C and T indicate Table 3. 3. Proposed Proposed structures structures for for CIMS CIMS ions ions in in the the phenol phenol low-NO low-NOxx system. system. C C and and T T indicate indicate the the cluster cluster and and Table Proposed structures for CIMS ions in the phenol low-NO and T indicate the cluster and x system. C the clusterTable and3. transfer product, respectively. Table Proposed structures Table 3.product, Proposed structures for for CIMS CIMS ions ions in in the the phenol phenol low-NO low-NOx system. system. C C and and T T indicate indicate the the cluster cluster and and transfer3. respectively.

ACPD

Full Screen / Esc


Table 4. Proposed structures for CIMS ions in the guaiacol low-NO system. C and T indicate the cluster and transfer product, respectively.

|

e

Discussion Paper

3520

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

e

Discussion Paper

d

|

c

Discussion Paper

b

|

a

Discussion Paper

Table 4. Proposed structures for CIMS ions in the guaiacol low-NOxOHsystem. C and T indicate the cluster and Observed m/z respectively. Product Chemical Formula Proposed Structure (one Chemical Pathwaya transfer product, respectively. OCH3 isomer shown) transfer product, transfer product, respectively. transfer product, respectively. Table 4. Proposed structures for CIMS ions in the guaiacol low-NOxOHsystem. C and T indicate the clusterguaiacol and b 209 C C H O 7 8 2 Observed m/z m/z Product Product Chemical Chemical Formula Formula Proposed Proposed Structure Structure (one (one isomer shown) shown) Chemical Pathway Pathwayaaaaa OCH3 isomer Observed Chemical Observed m/z m/z Product Product Chemical Chemical Formula Formula Proposed Proposed Structure Structure (one (one isomer shown) shown) Chemical Pathway Pathway Observed isomer Chemical transfer product, respectively. Table 4. for CIMS OHsystem. C and T indicate the cluster and 209Proposed structures Cb C7 H8ions O2 in the guaiacol low-NOxOH guaiacol OH OH OCH3 OH OH OCH a 3 OCH3 isomer shown) OCH Observed m/z respectively. Product Chemical Formula Proposedlow-NO Structure (one Chemical 3 transfer product, OCH 3 Table 4. Proposed structures for CIMS ions in the guaiacol system. andPathway HOx OCH 3 C and T indicate the cluster x system. 209Proposed Cbbbbb C77 H H88ions O22 in guaiacol Table 4. structures for CIMS the guaiacol low-NO C and T indicate the clusterx and x 209 C C O guaiacol OH 7 8 2 a 209 C C H O guaiacol OH 7 8 2 209 CC C7H H8Formula O2 guaiacol Observed m/z respectively. Product Chemical Proposed Structure (one Chemical Pathway HOO transfer product, OCH3 isomer shown) 1) hydroperoxide 259 C 7 10 O5 HO OCH3 transfer4. product, respectively. Table Proposed structures for CIMS ions in the guaiacol low-NO x system. C and T indicate the cluster and OH OH 209 m/z Product CCb C7H H8Formula O guaiacol 2 OH Observed Chemical Proposed Structure (one isomer shown) Chemical Pathwayaa HOO OCH OH 3 1) hydroperoxide 259 C O OH 7 10 5 HO OCH Observed m/z respectively. Product Chemical Formula Proposedlow-NO Structure (one isomer shown) Chemical Pathwaya 3 OH transfer HO OCH Table 4.product, Proposed structures for CIMS ions in the guaiacol system. HO x OH OCH33 C and T indicate the cluster and HO OCH b HO OH OCH33 OH 209 C C7 H8 O2 guaiacol HO OH OCH OCH3 Observed Product Proposed Structure Chemical HOO 1) hydroperoxide hydroperoxide 259 C CChemical H10 O55 7H 10 OCH3 HOO Observed m/z respectively. Product Chemical Formula Proposed Structure (one Chemical Pathwaya transfer product, 1) 259 C C O OH HOO 7 OCH33 isomer shown) HOO 10 O 1) hydroperoxide 259 C C a= guaiacol + OH HOO OH hydroperoxide 259 C CC7777H H O3555 10 HO OCH3 225 H10 O 2) G +1)OH 8O 209 CCbbb CFormula H guaiacol m/z (one isomer shown) Pathway 7 8 2 HO OH OCH 3 7 8 2 209 C C H O guaiacol Observed m/z Product Chemical Proposed StructureOH (one Chemical Pathwaya 7 8Formula 2 OH OCH3 isomer shown) HOO OH hydroperoxide 259 C C O HO OH OCH3 HO 225 C C77H H10 2) G +1)OH = guaiacol + OH OH OCH 8 O35 HO OHOH OCH33 OH OCH HO 209 Cb C7 H8 O2 guaiacol 3 HO OCH OCH OH HO OCH 3 33 OH OH HO HOO OH OCH3 HO 1) hydroperoxide 259 C C O345 b 77H 10 2) G + 2OH = guaiacol guaiacol + + OH 2OH 241 C H O HO OCH 8 3 225 C C H O 2) G + OH = guaiacol + OH HO OCH HO OCH 3 7 8 C H88H O323 O 2) G+ OHguaiacol = 7 HO OH OCH33 209 225 C CCCCb guaiacol 209 225 C 2) 7H 3 OH 78 O 2 225 CC H O8 2) G G+ + OH OH = = guaiacol guaiacol + + OH OH 7 3 OH OCH3 HO OH OH OCH3 HOO HO 1) hydroperoxide 259 C C H O455 OH HOO 2) G + 2OH = guaiacol + 2OH 241 C H O 7 10 OH 7 8 7 10 HO OCH HOO 3 1) hydroperoxide 259 C C7 H10 O5 HO HO OH OCH33 OH OCH HO OCH 3 HO OH OCH 225 Cc C7 H8 O3 2) G + OH = guaiacol + OH HO OCH33 HO OCH OH 3 OH OCH 191 C77H H88O O45 2) G G+ + 2OH 3OH = = guaiacol guaiacol + + 2OH 3OH HO 2) 241 C 3 HO HOO (1) hydroperoxide 259 259 C TCCCC C HO O5 2) G + 2OH = guaiacol + 2OH 241 C H 1) hydroperoxide C O10 HO 8 4 77 10 HO OH OCH3 HO 7 7H 8O 45 OH 2) G + 2OH 241 C H HO 7 8 4 OH 2) G + 2OH = guaiacol guaiacol + + OH 2OH 241 C H O 7 8 4 OH 225 2) G +2OH OH = HO OH OCH3 OH OCH HO OH OH 191 Tc C7 H88 O35 2) G + 3OH = guaiacol + 3OH HO OCH3 OH HO OCH OH OCH HO OCH3333 HOO HO 1) hydroperoxide 259 C C77H10 O5 OH HO OCH OCH HO OCH 3 33 HO OCH 2)2)GG++2OH = guaiacol guaiacol + + OH 2OH 241 C77 H O34 8O 225 C OH = OH OCH33 8 OHO 3O 225 225 C TTTCCCccccc C7HH (2) G OH = guaiacol HO OH 191 2)2)G G 3OH 3OH + OH C O G+++ OH = guaiacol + OH 5 3 HO OH 78888H 3 191 C O 2) HO OH OCH OH 3O 5 191 C7777H H O8 2) G G+ + 3OH 3OH = = guaiacol guaiacol + + 3OH 3OH HO OH 5 OH HO OH 8 5 OHOCH 191 TC C H O 2) + 3OH = guaiacol + 3OH OH 3 7 8 5 HO 175 T ring opening acid OCH OH 2) G + 2OH = guaiacol + 2OH 241 C 7H 8O 4 3 OH OCH OHO HO OCH3 225 C C7 H8 O3 2) G + OH = guaiacol + OH HO OCH 3 HO OH OCH33O c HO OH OCH 191 C77 H H88H O45 O 2) G G +ring 3OH = guaiacol guaiacol + 2OH 3OH OH 3 OHOCH HO OCH 175 opening 2) + 2OH = + 241 C O HO 241 241 C TCCT (2) G 2OH =acid guaiacol + 2OH OCH33 3 7H 4 OCH HO OHO 788O 8 4 3 2)2)G 2OH = guaiacol + 2OH CC 225 G+++ OH OH OCH 7 4 OCH O 3 3 3 3O O O OH O OH OH O OHO O OH 191 TTc C H O 2) G + 3OH = guaiacol + 3OH O OH 7 8 5 OH OH 175 C H O ring opening acid O HO OCH 7 8 4 HO OCH 175 T C77 H H88 O O44 ring opening acid OH 33 HO OH HO OCH 2) G + 2OH = guaiacol + 2OH 241 C C d 3 OCH HO OCH 175 T ring opening acid OH OCH33 3 175 C77 H88 O445 opening 3aii) EPOX and 2) acid + 3OH 257 OHO O O OH OH (2) G+ring + 3OH =Gguaiacol + 3OH 191 191 TcTCTTccc 191 CCH O55 O5 2) G 3OH = guaiacol + 3OH HO OH O 7888H HO OH O C7777H O8 2) G + 3OH = guaiacol + 3OH 5 HO OCH 2OHopening 2OH 241 C 3 OCH OH OCH OH 175 ring acid 33 3aii) EPOX and 2) G + 3OH 257 CTd C7 H88 O544 OCH O 3 OCH 3 O O OHOCH O O OCH33 O c OH O O O HO OH O O CC 2) G opening + 3OH = guaiacol + 3OH O 7 H8 O5 OCH3O OHO O OCH OCH OH 175 191 T CCTTdddd O4 ring 3O 3 OH 175 C O ring opening acid OCH 3 O 7H 4 3aii) EPOX EPOX and 2) 2)acid G+ + 3OH 3OH 257 O 788H 5 OH OCH 3aii) and G 257 C H O8 3 OH 7 5 O d OH 7 H8 5 O OCH EPOX 2) 257 C C OH 3 O 7 8 O5 3aii) EPOX and 2) G G+ ++3OH 3OH 257 C C OHO OH OH O 191 TTc 2)3aii) G +3aiii) 3OHring =and guaiacol 3OH O O 149 C775H H886O O554 fragment OO O OCH OH 175 T C77 H88 O44 ring opening acid OH 3 O d OCH 3 OH Td C O ring opening acid OH 7 H8H 4O OCH OH 257 175 C C (3aii) EPOX and (2) G + 3OH 3 OH O 3aii) EPOX and 2) G + 3OH 257 C C H O 7 8 5 O OH 76 O84 5 OO O OH 149 T C5 H 3aiii) ring fragment OO OH OCH OH OCH33 O O OCH O OCH OH3 3 O 175 Td C7 H8 O4 ring opening acid OHOCH 3 O OCH OH O O O OCH 3 3 3aii)3aiii) EPOX andfragment 2) G + 3OH 257 CT C OCH 3aiii) ring fragment 187 C O O33 O O OCH 149 C7554H H8666O O5443 ring O O O T C H O 3aiii) ring fragment O O OH 5H 6H 4O O OO 149 T C O 3aiii) ring fragment OH O O 149 149 T (3aiii) ring 5 6 4 O 175 ring opening acid 149 Tdd CC H O 3aiii) ringfragment fragment 7 56 8 6 4 OHOCH3 O O 4 OH OH O 3aii) EPOX and 2) G + 3OH 257 CCd C7547 H O OH OH 3aiii) ring fragment 187 OCH O 3 HO O OH OH OH OH 199 3aii)3aiii) EPOXring andfragment 2) G + 3OH 257 CC C73H88684O55353 O O OH O OO O O 149 T C5 H6 O4 3aiii) ring fragment O O 3O OCH OO 187 C744 H H866 O O533 3aiii) ring fragment OCH O 3 OH 187 ring fragment HO OH O O OH 3aii)3aiii) EPOX and 2) G + 3OH C 199 187 3aiii) ring fragment O 3 3O 187 257 C CCCCTCTd (3aiii) ring fragment 4H C O 4 3 O O OH 3 3aiii) ring fragment 187 CC H O6 OHOCH 4666464H 3 107 4 3 OO O 3H 149 C O 3aiii) ring fragment OH O 5 4 O O 3O O OCH O O O OCH d 3 O O OH HO OH OH3 3aii) EPOX and 2) G + 3OH 257 C OHOCH 7 8 5 199 C C H O 3aiii) ring fragment 3 4 3 HO OH C H O ring fragment OCH O HO OH 199 199 C CCCTT (3aiii)3aiii) ring 3 3 3 187 OOH HO 4 3 O3 3aiii) ringfragment fragment 107 CC H O4 3H O 199 34464H HOO OH O 3 3 149 C O 3aiii) ring fragment O OH 199 O O O 149 T C5535H6646O4434 3aiii) ring fragment O O OHOCH O OCH O3 3 O O OH O 189 C C H O 3aiii) ring fragment O 3 4 4 OH OCH OO 3 3aiii) ring fragment 187 C OH O OH O OH 4 6O 3 OCH 107 3 3H 3O 107 149 T CTTCT (3aiii)3aiii) ring HOO OCHO 3aiii) ringfragment fragment 107 CC H O4 O 199 3 3 OCH 364444H 3 33 OO 3H 3 OCH C O ring fragment 107 3 5 4 3 3 O OOCH 3aiii) ring fragment 107 T C H O 3 OHOCH OH O3 189 C C33 H H44 O O34 3aiii) ring ring fragment fragment OH O OH O 3aiii) 187 C C OO OH 4 6 3 OH HO OH 4 6 3 O OH OO 199 3aiii) ring fragment 187 C C H O 3 4 OO 4 6 3 O OCH 149 T C H O 3aiii) ring fragment O 3 5 6 4 O O 3aiii) ring fragment 107 T C H O O 3 4H 3 O O HO OCH OO 3O O 189 189 C CC C (3aiii) ring fragment OCH 189 C H O 3aiii) ring fragment O 3 3 4 4 O 3 34 O 44 4 OCH C 3aiii) ring fragment 3H O OH OCH 3 OCH 189 C C H O 3aiii) ring fragment HO O OHO 3 OH OH 187 199 189 C C433336H H644446O O344345 3aiii) ring fragment HO OH O OCH 243 T 3b) C bicyclic ketone HO OH 3 6 O 199 C C 3aiii) ring fragment 107 T 3 4 3 HO O O O O OOO OCH O OHO OO 3 3aiii) ring fragment 187 C CC H64H O34 O OH 189 4 3H OH 243 199 T (3b) C bicyclic ketone HOO OH OCH 3b) C bicyclic ketone 243 T 3 OH C C O 3aiii) ring fragment 6 6 5 6 O OCH 3 4 3 107 T 644O 5 6 ring OH 3 HO O 3aiii) ring fragment fragment C333H H O6 OCH OH 33O O 3 HO 3aiii) 107 T C 4 3 HO OH OO O HO O O O HO OH OCH O 3O OHO 189 C C 3aiii) ring fragment O 3H 4O 4 HOO OHO OH O OH O 3b) C bicyclic ketone 243 T C H O 199 C 3aiii) ring fragment O 6 6 5 6 3 4 3 O 3b) C bicyclic ketone 243 T C366H H466O O55 O O3 OCH OHO O 3aiii) fragment C 3b) C6666 ring bicyclic ketone 243 O 6 6 O3 5 3b) bicyclic ketone 243 C H 6 5 O OH O O 129 107 TeTCTTe (4) methoxy loss 129 CC H O6 4)CMethoxy Loss HO 6H 2 O2 3 64646H O OHOCH OCH 189 C O 3aiii) ring fragment 3 4 OOH33 OCH 3H 4 189 C C 3aiii) ring fragment O 3 4O 4 OCH OHO 3 3aiii) ring fragment 107 T C H O 3 4 3 e OH 3b)4)CMethoxy ketone 243 T C66 H H66 O O O OH 6 bicyclicLoss a 129 C HO O OH Numbers indicateTcorrespondence with25pathways outlined in mechanism (Figure 6). OH OH3 OHOCH OH OOH 189 indicateCcorrespondence C3 H4 O4 3aiii) ring fragment OH O Numbers with pathways Ooutlined in mechanism (Fig. 6). OH OH O OH OH b 3b)4)CMethoxy ketone 243 Teee as C7 H8C O 6H 6but 5 is lower signal than at m/z 6 bicyclicLoss OH a 129 T C H O m/z 143 is also present O , 209. HO O 6 6 2 2 Numbers indicateT correspondence with HO O (Figure 6). e 129 C66H 4) Methoxy Loss 6O 2pathways outlined in mechanism HO OHOCH O 129 T O 4) Loss 189is also present 3aiii) ring fragment 6 O 3O 3H 129 TCe CC H6646H O2242O2 , but is lower signal 4) Methoxy Methoxy Loss m/zbc 143 asC 6 O O OH than at m/z 209. O O 3b) C bicyclic ketone 243 T from C H7, 66ring O855isopening OH Also includes signal C77H H8C O acid. 6 a m/z 8O 6H 143 isindicate alsosignal present as C lower signal thaninatmechanism m/z 209. a 25with 3b) C666 bicyclic ketone 243 T OO Numbers correspondence pathways outlined (Figure 6). 6). 6 6but 5pathways a Numbers e HO OH O (Figure Also includes from C H ring opening acid. a indicate correspondence with outlined in mechanism a Numbers indicate correspondence with pathways outlined in mechanism (Figure 6). 7 8 5 129 indicateTcorrespondence C6 Hwith 4) Methoxy Loss 6 O2pathways outlined in mechanism O OH (Figure 6). d Numbers c O Includes contributions from G + 3OH along pathway 2 in Figure 6 b Also includes signal from C7 H8 O5 ring opening acid. OH b m/z243 143contributions is also also present present as C C H8CO O6G but is lower lower signal than than at m/z m/z 209. b m/z 3b) C6 bicyclic ketone Te as H O53OH 7H 2 ,, 6+ b 143 is but is signal at 209. Includes from along pathway 2 in 7 2 HO OH O Fig. 6 b 7 H8 8 2 ,, but 143 is also present as C O is lower signal m/z 209. OH a e m/z 7 8 129 Tcorrespondence C O2pathways 4) Methoxy Loss m/z 143 is also present as O6 22H but is lower signal than at m/z O 7H 8 d Numbers indicate outlined inat (Figure 6). 26 2 than m/z 195 iscontributions alsosignal present as C C ,6ring but isopening lower signal than atmechanism m/z6OH209. 129. 6O 2with O OH Includes from GH 3OH along pathway in Figure OH Also includes from C677as H+ O acid. OH than at m/z 129.3b) C bicyclic ketone 8O 5 6ring m/zccccbc Also 195 is also present C H O , but is lower signal includes signal from C H opening acid. 243 T C H O 8 5 6 5 6 6 opening 2 8O 56 ring Also includes signal C H acid. e 8 5 e from includes signal from C7777H H8C O opening acid. a 8O e Also m/z 143 is also present as C ,, 66ring but is lower signal than at m/z 209. 129 Tcorrespondence H O22pathways 4) Methoxy Loss OH e 25with 6 d Numbers indicate outlined in mechanism (Figure 6). 26 6 m/z 195 is also present as C H O but is lower signal than at m/z 129. d 6 6 2 129 T C H O 4) Methoxy Loss Includes contributions from G + 3OH along pathway 2 in Figure 6 6 along 2 d Includes contributions from G + 6 OH d 3OH pathway 2 in Figure 6 d Includes contributions from G + 3OH along pathway 2 in Figure 6 c Includes contributions from G + 3OH along pathway 2 in Figure 6 b Also includes signal C H88O O25with openingsignal acid. a e 143 also as ,, ring but is m/z e from a m/z e Numbers indicate correspondence outlined inat mechanism (Figure 6). 26 than m/z 195 is isindicate also present present as C C7667H H66CO O6 H but is lower lower signal signal thanin atmechanism m/zOH209. 129. a e m/z 129 Tcorrespondence O2pathways 4) Methoxy Loss 2with 26 e 195 is also present as C H ,6but is lower at m/z 129. 2 Numbers outlined OH (Figure 6). e 6H 6O 2 but pathways 26 than 195 is also present as is lower signal than at d m/z 6 6 2 m/z 195 iscontributions alsosignal present as C C H O isopening lower signal than at m/z m/z 129. 129. c 6G 6 2 ,, but Includes from + 3OH along pathway in Figure b Also includes from C H O ring acid. b 7 8 5 e 143 is also present as C77 H88CO622H, 6but is lower signal2 than at m/z6 209. b m/z129 a T O 4) Methoxy Loss 2 m/z 143 is also present as C H O , but is lower signal than at m/z 209. 7 8 2with pathways outlined in mechanism (Figure 6). Numbers indicate correspondence

Full Screen / Esc


The error in the accurate mass measurements is the difference between the theoretical mass of the suggested molecular formulae of the parent molecule (M) and the measured mass of the ion.

|

3521

Discussion Paper

∗

−2.1 −0.1 −2.6 −2.4 −2.4 −1.4 2.1 −2.1 −1 −1.5 −1.4 −1.3 −2.2 −2.7 −1.3

13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

C7 H10 O6 C7 H8 O8 C5 H8 O5 C6 H6 O5 C4 H6 O5 C4 H6 O6 C7 H10 O7 C6 H10 O4 C5 H8 O6 C7 H8 O7 C7 H8 O5 C7 H6 O5 C7 H10 O5 C4 H4 O4 C5 H6 O4

Discussion Paper

189.0378 219.014 147.0266 157.0113 133.0133 149.0072 205.0327 145.048 163.0233 203.0177 171.0279 169.0124 173.0428 115.0004 129.0175

∗

Error (mDa)

|

189 219 147 157 133 149 205 145 163 203 171 169 173 115 129

Suggested Chemical Formula (M)

Discussion Paper

Meas. Mass

|

−

[M-H]

Discussion Paper

Table 5. SOA products observed in UPLC/(-)ESI-TOFMS offline filter analysis for the guaiacol low-NOx system.

ACPD

Full Screen / Esc


x x

225 211

205 287 245

3

b c d

149 C H ring 5 6O 4 149 CC H O6 ring fragment fragment T TTTT ring fragment 5 4 5H 4 O4 149 C H O ring fragment 566666H 5 4 149 C O ring fragment 5 4 149 T C H O ring fragment 5 4 149 T C H O ring fragment 149 T C5555H H6666O O4444 ring fragment fragment 149 T C ring 5 6 4 149 T 185 C C H O ring fragment 5 6 4 C C H O ring fragment 4 4 3 149 T 185 C 4 3 149 T C ring 4664444O 3 4 3 185 C C554444H H O4 ring fragment fragment 3 185 C C H O ring fragment 3 185 C C H O ring fragment 4 4 3 4 4 3 185 C C H O ring fragment 185 C C44 H444O O33 ring fragment 185 C C ring 185 C C4444H H444 O O33 ring fragment fragment 185 C C H ring fragment C O333 ring fragment 4 H4 203 185 C CCC O4 ring fragment ring 203 C H O 4 4 ring fragment fragment 203 CC H O6 46666H 4 4 4H 4 ring fragment 203 C C H O 4 4 ring fragment 203 C C O 4 H6 6 O4 4 ring fragment 203 C C 4 4 6 4 ring fragment 203 C C H O 4 6 4 275 203 C CCC O6 none C8 scission 275 C O none proposed C scission ring fragment 203 CC H O 74H 6H 46 275 C H O10 noneproposed proposed C888 fragment scission ring C H O 710 10 6 6 4 6 4 10 6 ring fragment 203 C77774444H H O 275 C H O none proposed C scission 6O 46 10 6 8 fragment 275 C H O none proposed C scission ring 203 C C H 10 8 6 4 275 C O none proposed C scission ring fragment 203 C C H O 7 10 6 8 4 6 4 7 10 6 8 275 CC H10 O766 O noneproposed proposed C88 scission scission 7H 10 291 C O none proposed C 275 291 275 C CCCC HO none C8 scission 7 291 C none C 7 6 7 10 6 7 275 C7777H H710 O10 none proposed proposed C8888 scission scission 291 10 O 6 7 291 275 C C H none proposed C scission 7 10 6 291 275 C C H O none proposed C scission 7 10O 291 C C H none C 10 291 C C7777H H10 O76777 none proposed proposed C8888 scission scission a 10O 291 C C none C a outlined (Figure a Letters 10 7 291 indicate C C7777with H10 O none proposed proposed C8888 scission scission a 10 pathways 7 Letters indicate correspondence correspondence with pathways outlined in in mechanism mechanism (Figure 10). 10). 291 C C H O none proposed C scission a 10 7 291 C C H O none proposed C Letters indicate correspondence with pathways outlined in mechanism (Figure 10). a 7with 10 7 8 scission a Letters indicate correspondence pathways outlined in mechanism (Figure 10). a indicate correspondence with pathways outlined in mechanism (Figure 10). Letters indicate correspondence with pathways outlined in mechanism (Fig. b a Letters Letters indicate correspondence with pathways outlined in mechanism (Figure 10). b a a m/z 239 is also present as C H O , but is lower signal than at m/z 173. Letters indicate correspondence with pathways outlined in mechanism (Figure 10). b 8 10 3 a b m/z 239indicate is also also present present as C C8 H H10 O33 ,, but but is lower lower signal than than at m/z m/z 173. 173.(Figure Letters correspondence pathways outlined in b a 10with Letters indicate correspondence with pathways outlined in mechanism mechanism (Figure 10). 10). m/z 239 is as O is signal at b a 10 3 ,, but b m/z 239 is also present present as C8888 H H10 O but is lower signal than at m/z 173. 173.(Figure Letters indicate correspondence with pathways outlined in mechanism (Figure 10). 10 3 b 239 is also as C O is lower signal than at m/z Letters indicate correspondence with pathways outlined in mechanism 10). 3 c b m/z 10 m/z 239 is also also present as C C6888H H610 O but is lower signal than at m/z 173. m/z 239 is also present as C Osignal , but lower c b b m/z 195 is also present as C H O is lower than at 129. 239 is O223333,, ,,,but but isH lower signal thanis atm/z m/z 173. signal than at m/z 173. c m/z 10 8 10 3 b c 195 O but is lower signal than at m/z 129. 239 present as O but is lower signal than at m/z 173. 6 6 8 10 c b 8 10 3 6 6 2 m/z 239 239 is also also present present as as C C H H10 O2233,,, ,,but butis islower lowersignal signalthan thanat atm/z m/z129. 173. 195 is OO but isis lower signal than atat m/z 129. c m/z b 10 6O 195 O but is lower signal than at m/z 129. is O but is lower signal than at m/z 173. 6 195 m/z 239 also present as C88866666H but lower signal than m/z 173. 6 2 10 6O 23 ,but m/z 195 is also present as H is lower signal than m/z m/zccdccdcdddcc m/z 195 also present as C H Oring lower 2 Includes from 2OH as well opening m/z 195 is iscontributions also present as C C6S H+ O but is lower signal thanisat atacid. m/z 129. 129. signal than at m/z 129. 2,,, but 6as 2 , but Includes contributions from SH +66666O 2OH as6 well as ring opening acid. 195 also as is lower signal than m/z 2 2 m/z 195 is iscontributions also present present from as C C6666S H+ O but iswell lower signal than at atacid. m/z 129. 129. Includes contributions from S + 2OH as well as ring opening acid. d c 2 ,, but d m/z Includes contributions from S + 2OH as well as ring opening acid. 195 is also present as C H O is lower signal than at m/z 129. 6O 2 d Includes 2OH as as ring opening 195 is also present as C H , but is lower signal than at m/z 129. 6S 6 2 d m/z Includes contributions from + 2OH as well as ring opening acid. d d Includes contributions from S + 2OH as well as ring opening acid. Includes Swell + 2OH as well as ring opening acid. d Includes contributions + as acid. d Includes contributions contributions from from S S from + 2OH 2OH as as well as ring ring opening opening acid. d Includes contributions from S + 2OH as well as ring opening acid. Includes contributions from S + 2OH as well as ring opening acid.

3522

|

28 28 28 28 28 28 28 28 28

10).

Discussion Paper

a

hydroperoxide a) a) G G+ + OH OH = = guaiacol guaiacol + + OH OH a) G + OH = guaiacol + OH a) G + OH = guaiacol + OH a) G + OH = guaiacol + OH a) G + OH = guaiacol + a) G G ++ OHOH = guaiacol guaiacol + OH OH (a) G = guaiacol + OH a) + OH = + a) G G+ + OH OH = = guaiacol guaiacol + + OH OH a) OH a) G+ OH = guaiacol + OH b) b) THB THB = = DHB DHB + + OH OH b) THB = DHB + OH b) THB = DHB + OH b) THB = DHB + OH b) THB = + (b) b) THB DHB + OH b) THB = = DHB DHB + OH OH b) THB THB = = DHB DHB + + OH OH b) THB = DHB + OH b) THB = DHB + OH c) guaiacol c) guaiacol c) guaiacol guaiacol c) guaiacol c) (c) guaiacol c) c) guaiacol guaiacol c) c) guaiacol guaiacol c) guaiacol c) guaiacol d) d) DHB DHB = = phenol phenol + + OH OH d) DHB = phenol + OH d)DHB DHB = == phenol + OH DHB phenol + OH (d)d) phenol + OH d) d) DHB DHB = = phenol phenol + + OH OH d) d) DHB DHB = = phenol phenol + + OH OH d) DHB = phenol + OH d) DHB = phenol + OH ring opening acid ring opening acid ring opening opening acid acid ring opening acid ring opening acid ring ring ring opening opening acid acid ring ring opening opening acid acid ring opening acid ring opening acid SEPOX SEPOX SEPOXSEPOX SEPOX SEPOX SEPOX SEPOX SEPOX SEPOX SEPOX SEPOX ring ring fragment fragment ring fragment ring fragment ring fragment ring fragment ring fragment ring fragment fragment ring ring fragment ring fragment fragment ring

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

149 185

hydroperoxide hydroperoxide hydroperoxide hydroperoxide hydroperoxide

hydroperoxide hydroperoxide hydroperoxide hydroperoxide hydroperoxide hydroperoxide

Discussion Paper

129

OH OH OCH3 OH OH OCH OH OH 333 OCH OH OCH OOH 3 OH OCH OOH OH OOH OCH OH 33 OOH OH OOH OH OOH OH OH OOH OH OH OOH OH OH OOHOCH OH OH HO OOH OH OH 3 OOH HO OCH OH OOHOCH HO OCH33 OH OOH HO OH 3 HO OCH OOH OH 3 HO OCH OH HO OCH33 OH HO OH OCH HO OCH33 OH HO OCH OH HO OCH HO OCH333 HO OCH OH 3 HO OH OH OCH3 OH HO OH OH HO OH OH HO OH OH OH HO OH HO OH OH OH HO OH HO OH OH HO OH OH HO OH OH HO OH OH HO OH HO OH HO OH OH HO OH OH OH OH OH OCH 3 OCH OH 3 OCH OH OCH33 OH OCH OH OCH 3 OH OCH33 OH OH OCH OCH33 OH OCH OH OCH OCH333 OCH OH 3 OH OH OCH3 OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH O OH O OH O O OH O OH O O O OH O O OH OCH O 3O 3OCH OH O OCH OCH OH 3 OCH33O OCH O O 3OCH OH OCH O 3O 3 OH O OCH 3OCH3O O OCH OCH333O OCH33OCH O O OCH OCH O O OCH33OCH OCH33O OCH 3 HO OCH 3O HO OCH333OCH OCH O O 3 HO OCH OCH O O 3 3 HO O OCH OCH3O O HO OCH33O O O O HO OCH O O HO OCH O O O HO OCH333O OCH O 3O HO O OCH O OCH HO OCH33O O 33O O OCH HO O OCH O HO 3O O O OCH 3O HO O O OCH HO OCH33O O OH O O O OCH OH O OCH33O OH OH OCH O 3 3 O OCH OH 3 OCHOCH O OCH OH 3 3 O OCH OH OCH 3 3 O OCH OH OCH 3 3 O OCH OH 3 O OCH OH O OCH OCH33 3 OCH OH OCH O OH O 3 3 OCH O OCH 3 OCH O OH 3 O OCH O 333 OH OCH O 3 OCH O O OCH OCH O 3 OCH33 OOCH O O 3 OCH O 3 O OCH33 OOCH OO OCH O 3 OCH O 3 O H CO OCH 3OCH 3 O O H CO OOH H33OCH CO 3 O OO OH H 3CO 3 O OH H OO OH 3CO H O OH H33CO CO O H CO O OH OH H33CO CO O OH H O 3 OH H CO H33CO CO OH O OH H O 3CO OH O H 3 OH O OH O O O OO O O O O O O O O O OO O O OH O O OH O O OH O O OH O O O OH O O O OH OCH O OH 3 O OCH O OH 3 O O OCH OH 3 O HO OCH OH 3 OCH OH O 3 HO OCH OH O 33 O HO OCH OH O HO OCH 3 OOH HO OCH O HO OCH O 333 HO OCH O HO OCH O 3 O HO O OCH O HO O OCH O 33 HO O HO O O O HO O O O HO O O O O O O O O O

H33CO CO H H H333CO CO H CO 3CO H

C O C888 H H12 O666 12 12 O C H O 8H 12 6 C H 8 12 6 C 8 12 6 12O C H O C8888H H12 O6666 O 12 C HO 8 12 6 CC H812 O12 6 8H 12 O C 8 12 C8 H12 O666 C H O C777 H H88 O O33 C 7H C H8888 O O3333 7 C 7 7 8 3 C H O 7 8 O3 CC 7 H8 3O C O 3 78888H 3 3 C7777H H O8 3 C H O 3 C O 7 H8 3 C C666 H H666 O O333 C H O 6 6 3 C H O 6 6 3 C 6 6 3 6H 6O C O 6 CC H O3333 O3 6H C O 666666H 3 C6666H H O6 3 C H O 6O 3 C 6 H6 3 C H O 7 8 2 C H O 7 8 C777 H H888 O O2222 C H O C 7 2 7 H8 2O C O 7 2 CC O8 7888H 2 7H 2 C C7777H H8888O O2222 C H O C7 H8 O2 C C666 H H666 O O222 C H O 6H CC H666H O222 O 6 C 6 2 C O 6666O 2 2 C666H H O6 2 C C6666H H6666O O2222 C H O C O 6 H6 2 C H O 8 10 5 C H O 8 10 5 8H 10 O 5 C H O 8 10 5 C C H O 8 10 5 C 8 H810 5 5 10O 5 C O 5 C888H H10 O10 10O 5 C 10 C8888H H10 O55 10 O C H 10 C O555 8 H10 C H O 8 10 6 C H O 8 10 6 8H 10 6 O CC H810 O10 HO 8 10 6 C 8 6 C H 6 8 10 6 10O C O C888H H10 O666 10O C 10 C8888H H10 O66 10 O C H 10 C O666 8 H10 C H O 6 8 5 C H O 6 8 O5 6H 5O CC H 6 5 C O8 68888H 5 6 5 C H O 6 5 C C666H H888O O555 C C6666H H8888O O5555 C H O C O 6 H8 5

|

209

C C C C C C CCCCC C C C C C C CCCCC C C C C C C C CCCCC C C C C C C CCCCC C C Cc Tccc cT T TTTTTcccccccc T Tcc T T d d T d d TdTTTTTddddddd T d T d T d T T C CCCCC C C C C C C C C CCCC C C C C C C

Discussion Paper

289

289 289 289 289 289 289 289 289 289 289 289 225 225 225 225 225 225 225 225 225 225 225 211 211 211 211 211 211 211 211 211 211 211 209 209 209 209 209 209 209 209 209 209 209 129 129 129 129 129 129 129 129 129 129 129 205 205 205 205 205 205 205 205 205 205 205 287 287 287 287 287 287 287 287 287 287 287 245 245 245 245 245 245 245 245 245 245 245

|

Table 6. 6. Proposed Proposed structures structures for for CIMS CIMS ions ions in in the the syringol syringol low-NO low-NOxxxx system. system. C C and and T T indicate indicate the the cluster cluster and and Table Table 6. Proposed structures transfer respectively. Table 6. 6.product, Proposed structures for for CIMS CIMS ions ions in in the the syringol syringol low-NO low-NOxxx system. system. C C and and T T indicate indicate the the cluster cluster and and transfer product, respectively. Table Proposed structures Table 6.product, Proposed structures for for CIMS CIMS ions ions in in the the syringol syringol low-NO low-NOxxxx system. system. C C and and T T indicate indicate the the cluster cluster and and transfer product, respectively. transfer product, respectively. Table 6. Proposed structures for CIMS ions in the syringol low-NO system. C and T indicate the cluster and transfer respectively. Table 6. Proposed structures for CIMS ions in the syringol low-NO x system. C and T indicate the cluster and a transfer product, respectively. transfer product, respectively. Observed m/z Product Formula Structure isomer Chemical transfer product, Observed m/z respectively. Product Chemical Chemical Formula Proposed Proposed Structure (one (one isomer shown) shown) Chemical Chemical Pathway Pathwayaaaaa Observed Product Chemical Proposed Structure transfer product, respectively. Observed m/z Product Chemical Formula Proposed Structure (one isomer shown) Chemical Pathway transfer product, respectively. a Observed m/z respectively. Product Chemical Chemical Formula Formula Proposed Proposed Structure Structure OH (one isomer isomer shown) shown) Chemical Pathway Pathway transfer product, a Observed m/z Product (one Chemical a Observed m/z Product Chemical Formula Proposed Structure (one isomer shown) Chemical Pathway a a Pathway OH a Observed m/z m/z Product Product Chemical Chemical Formula Formula Proposed Proposed Structure Structure (one isomer shown) Chemical Pathway OH OH Observed (one isomer shown) Chemical O O OH m/z Formula (oneStructure isomer Observed m/z m/z Product Product Chemical Chemical Formula Proposed Proposed Structure (one isomer shown) Pathway Chemical Pathway Pathwayaa O O OH H CH O O shown) OH Observed Formula (one isomer shown) Chemical 3C 3 H C CH O O OH Observed m/z Product Chemical Formula Proposed Structure (one isomer shown) Chemical Pathwaya 3 H33C C O CH O OH 3 H CH O b 3C O 3 OH H CH O O OH 3 3 b H OH O 173 T C O syringol H33C C O CH33 O O CH OH 173 Tbbbb C888 H H10 O333 syringol H C CH 10 O OH H33C CO CH33 O O 10 O 173 T C H O syringol O O CH 8H 10 3 H 173 T C H syringol H CH 8 10 3 O O bb OH 173 T C syringol H333C C O CH333 8 10 3 OH 10O H CH 173 T C H O syringol 3C 3 OH O CH H 173 Tbbbb C8888H H10 O333 syringol OH 3CCO 3 10O H OCH OH 173 T C syringol 3 CO 3 H OCH OH 8 10 H33CO CO OCH33 173 CC H10 O3333 O syringol OH OCH 8H 10 H OH 173 C O syringol 3 3 8 10 173 173 TbTTTbb H syringol H CO OCH OH OCH33 C8 H810 O10 syringol 3 3 H OH 3 H33CO CO OCH3 OH H CO OCH OH OH H33CO CO OCH3 189 T C H O S + OH = syringol OH OH 8 10 4 H OCH 189 T C H O S + OH = syringol + + OH OH OH OH 333 3 8 10 4 H CO OCH 3 OH 8 10 4 H CO OCH 189 T C88 H H10 O44 S+ + OH OH = = syringol syringol + OH OH 33 10 O H33CO CO OCH 189 T C O S + OH = syringol + OH OH OH H OCH 189 T C S + OH OH 3 3 8H 10 4 OH 10O 189 T C H S + OH = syringol + OH OH OH OH 189 T C8888H H10 O4444 S+ + OH OH = = syringol syringol + + OH OH OH OH 10O H OCH OH T C S OH 3CO 3 H CO OCH OH OH 8 10 4 H33CO CO OCH33 189 T CC H810 O10 S + OH = syringol + OH OH OH 8H 10 4 O 189 189 T H S + OH = syringol H OCH OH 189 T C O S + OH = syringol + OH 3 3 OH 8 10 4 H CO OCH OH OCH33 4 189 T C8 H10 O4 S + OH = syringol + OH + OH 3 H OH H33CO CO OCH3 OH H CO OCH OH OH HO H33CO CO OCH3 271 C C H O S + 2OH = syringol + 2OH OH HO OH 8 10 5 H OCH 271 C C H O S + 2OH = syringol + 2OH OH HO OH 333 3 8 10 5 H CO OCH 3 HO OH 8 10 5 H CO OCH 271 C C88 H H10 O55 S+ + 2OH 2OH = = syringol syringol + + 2OH 2OH HO OH 33 10 O H33CO CO OCH 271 C C O S + 2OH = syringol + 2OH HO OH OH H OCH 271 C C S HO OH 3 3 HO 8H 10 5 OH 10O OH OH 271 C H 2OH + HO OH OH 271 C8888H H10 O5555 O 2OH = = syringol syringol + 2OH 2OH OH 10O H CO OCH OH 3HO 3 C 2OH + HO OH H CO OCH OH HO OH 271 271 C CCCCCC HO S SSSSSS+++++++2OH = syringol 8 10 5 H33HO CO OCH33 OH OH 271 CC H10 O10 2OH = = syringol syringol + 2OH 2OH + 2OH 8H 10 5 H CO OCH OH 5 271 C O 2OH = syringol + 2OH 3CO 3 8 10 5 H OCH OH OH 3HO 3 271 C H810 2OH = syringol + 2OH H 8 5 OH H33CO CO OCH33 OH OCH H CO OCH

Discussion Paper

Table 6. Proposed structures for CIMS ions in the syringol low-NOx system. C and T indicate the cluster and transfer product, respectively. Table 6. for ions Table 6. Proposed Proposed structures structures for CIMS CIMS ions in in the the syringol syringol low-NO low-NO system. system. C C and and T T indicate indicate the the cluster cluster and and Table 6. Proposed structures for CIMS ions in the syringol low-NO system. C and T indicate the cluster and

Full Screen / Esc


Discussion Paper |

140

3

) m/gµ(

100

Discussion Paper

2/2, 5.9 ppb 2/4, 12.4 ppb 2/6, 45.5 ppb 1/29, 66.3 ppb

120

80

|

MÄ

o

60 40

0 0

50

100

150

200 3

ÄGuaiacol (µg/m )

13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Fig. 1. Growth curves of guaiacol aerosol.

250

Discussion Paper

20

ACPD

Discussion Paper

owth curves of guaiacol aerosol.

|

3523

Full Screen / Esc


Discussion Paper |

3

) m/gµ(

300 200

|

MÄ

o

Discussion Paper

3/10, 185.1 ppb 3/15, 49.5 ppb 3/29, 112.9 ppb

400

0 0

200

400

600

800 3

ÄSyringol (µg/m )

1200

13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Fig. 2. Growth curves of syringol aerosol.

1000

Discussion Paper

100

ACPD

Discussion Paper

owth curves of syringol aerosol.

|

3524

Full Screen / Esc


Discussion Paper

-3

OH Exposure (molec cm h) 0

2

4

6

6

8

10x10

|

50

-2

2.0x10

1.0

30

20 0.5

10

0

10

0

0.0 2

4

6

Fig. 3. Phenol low-NOx gas-phase and particle-phase development.

enol low-NOx gas-phase and particle-phase development.

|

3525

Discussion Paper

Hours of Irradiation

8

13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

0

3

CIMS Signal (a.u.)

40

Discussion Paper

20

50

|

Phenol (ppb)

30

1.5

Discussion Paper

40

60

SOA Mass (µg/m )

Phenol (P) m/z 129 x 0.15 DHB m/z 211 THB m/z 185 FRAG SOA Mass

ACPD

Full Screen / Esc


Discussion Paper |

OH OH

C6H6O (-) 179

OH OH O2, HO2

OH OO

O HO2

O C6H6O3

O2,

OH (-) 145

+ O2, OH

-HO2 OH

OH OH C6H6O2 (-) 129

OH OH O2, HO2 OH

OH

OH OO

O HO2

OH

O C6H6O4

+ O2, OH

|

O2,

OH OH (-) 161

Discussion Paper

OH

-HO2 OH OH OH C6H6O3 (-) 211

OH OH O2, HO2 OH

OH O OH OO OH

OH

HO2

O C6H6O5

OH + O2, OH OH (-) 177

Discussion Paper

compound was detected.

|

3526

13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Fig. 4. Proposed pathway for gas-phase production of C6 carboxylic acids in the phenol lowFig. 4. Proposed pathway for gas-phase production of C6 carboxylic acids in the phenol low-NOx system. NOx system. Boxed structures indicate that the expected m/z from the chemical ionization Boxed structures indicatefor that the compound expected m/zwas fromdetected. the chemical ionization reactions in the CIMS for that reactions in the CIMS that

Discussion Paper

OH

OH

ACPD

Full Screen / Esc


0

2

4

6

6

10x10

8

-2

2.5x10

1.5

| Discussion Paper

CIMS Signal (a.u.)

Discussion Paper

2.0

|

m/z 145 x 0.2 ACID1 m/z 161 ACID2 m/z 177 ACID3 m/z 185 FRAG m/z 135 FRAG m/z 107 FRAG

Discussion Paper

-3

OH Exposure (molec cm h)

1.0

0.5

13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

0.0

ACPD

2

4

6

Hours of Irradiation Fig. 5. Selected phenol low-NOx gas-phase acids.

d phenol low-NOx gas-phase acids.

|

3527

8

Discussion Paper

0

Full Screen / Esc


Discussion Paper

products OH Analogous to C6 ring opening acids formation in phenol case

C6H6O2, MW = 110 C7H10O5, MW = 174 OH HO OCH3

OH

OCH3 + OH, O2

O O

(-) 259

HOO

(-) 175

OH

4 HO2

C7H8O2, MW = 124 OH OCH3 OH HO

HO2

1

C7H8O4, MW = 156

C7H8O3, MW = 140 OH

OH OCH3

O2

OCH3 -HO2

HO

(-) 209

OCH3 OH, O2, (-) 225 -HO2

HO

2 OO isom. isom. 3a

OCH3

HO

OCH3

O O

OO

HO

(-) 243

O

O

OCH3

O O C4H6O3 (-) 187

O

C5H6O3 (-) 199

O C4H4O2 (+) 103 OH

O O

O

O OCH3

O C2H2O2

C3H4O3 (-) 107

O

O OH C2H2O3

O

O OCH3

C3H4O4 (-) 189

Discussion Paper

O C5H6O4 (-) 149

C7H8O5, MW = 172 OCH3 O O OH

OH (-) 191

13, 3485–3532, 2013


Title Page

O

OH OCH3

O

(-) 257

HO

Ring Fragments (from various isomers) OH

decomp.

OCH3

OH

- CH3

O O

iii

O

O

O2, (-) 241 -HO2

HO

HO

decomp. ii

OCH3

OH,

C6H6O5, MW = 158 OH

OH

OH HO

OH OCH3

3b

epoxide

OOH

HO

|

C7H10O7, MW = 206 OH HO OCH3 O2, HO2 HO OO i

C7H8O5, MW = 172

OH

OH

Discussion Paper

(-) 129

C7H8O4, MW = 156

|

OH

ACPD

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Abstract

|

3528

Discussion Paper

Fig. mechanism for guaiacol Boxed structures that x oxidation. Fig.6. 6. Proposed Proposed mechanism for guaiacol low-NOxlow-NO oxidation. Boxed structures indicate that the indicate expected m/z the expected m/z from the chemical ionization reactions in the CIMS for that compound was from the chemical ionization reactions in the CIMS for that compound was detected. Chemical formulae in red detected. Chemical formulae in red correspond with those proposed for the filter accurate mass correspond with those proposed for the filter accurate mass aerosol measurements. aerosol measurements.

Full Screen / Esc


Discussion Paper

-3

OH Exposure (molec cm h) 0

2

4

6

6

8x10

3.0x10 50

2.0 100 1.5

80 60

1.0 40

3 )

10

120

0.5 20

0

0.0

0

Discussion Paper

20

140

|

Guaiacol (ppb)

30

160

SOA Mass (µg/m

40

CIMS Signal (a.u.)

2.5

m/z 257 EPOX, G + 3OH m/z 149 FRAG SOA Mass

Discussion Paper

Guaiacol (G) m/z 129 DHB m/z 225 G + OH m/z 241 G + 2OH

|

-2

ACPD 13, 3485–3532, 2013



Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Abstract

0

2

4

6

8

Fig. 7. Selected traces in guaiacol low-NOx gas-phase and particle-phase development.

lected traces in guaiacol low-NOx gas-phase and particle-phase development.

|

3529

Discussion Paper

Hours of Irradiation

Full Screen / Esc


0

-3

0

A

m/z 129 x 53 G-DHB m/z 211 x 230 G-THB m/z 129 x 31 P-DHB m/z 211 x 491 P-THB

Discussion Paper

1.5

|

Peak Normalized Signal

2.0

Phenol OH Exposure (molec cm h) 6 8x10 2 4 6

1.0 0.5 0.0 2

4

6

8

Discussion Paper

B -1

m/z 145 ACID1 m/z 161 ACID2 m/z 177 ACID3 m/z 145 ACID1 m/z 161 ACID2 m/z 177 ACID3

0.8 0.6 0.4

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

0.2

|

CIMS Signal (a.u.)

1.0x10

|

0

Discussion Paper

-3

Guaiacol OH Exposure (molec cm h) 6 2 4 6 8x10

0.0 2

4 6 Hours of Irradiation

8

Discussion Paper

0

Full Screen / Esc

Printer-friendly Version Fig. 8. Common chemical routes in the phenol and guaiacol low-NOx systems. (A) Dihydroxybenzenechemical routes in routes phenol in (diamonds) and guaiacol (open circles). Each CIMS is normal. 8. Common the phenol and guaiacol low-NO (A)trace Dihydroxybenzene routes x systems. Interactive Discussion ized by the peak value. (B) Common acids in phenol (diamonds) and guaiacol (open circles).

phenol (diamonds) and guaiacol (open circles). Each CIMS trace is normalized by the peak value. (B) |

3530

mmon acids in phenol (diamonds) and guaiacol (open circles).

200

CIMS Signal (a.u.)

150 100

0

500 1.5 400 1.0

200 100 0.0 0

Syringol (S) m/z 209 Guaiacol (G) m/z 225 G + OH

-2

2.0x10 CIMS Signal (a.u.)

Syringol (ppb)

8

m/z 211 THB m/z 275 x 0.21 SOA Mass

600 500

1.5 400 1.0

300 200

0.5 100 0 0

2

4 6 Hours of Irradiation

8

Fig. 9. Selected traces in syringol low-NOx gas-phase and particle-phase development. (A) OH

Discussion Paper

0.0

Fig. 9. addition Selectedpathways. traces in (B) syringol and pathways. particle-phase development. (A) OH addition x gas-phase Traceslow-NO indicating methoxy loss |

pathways. (B) Traces indicating methoxy loss pathways. 3531

ACPD 13, 3485–3532, 2013


Title Page Abstract

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

0

6

3

50

4

Discussion Paper

100

2

|

150

0

SOA Mass (µg/m )

200

300

0.5

B 250

600

3

50

-2

Discussion Paper

2.0x10

m/z 287 SEPOX m/z 245 FRAG SOA Mass

|

250

Syringol (S) m/z 189 S + OH m/z 271 S + 2OH

6

10x10

SOA Mass (µg/m )

Syringol (ppb)

0

OH Exposure (molec cm h) 2 4 6 8

Discussion Paper

-3

A

Full Screen / Esc


Discussion Paper |

(-) 209

C8H10O3, MW = 154 c

OH H3CO

OCH3

C7H8O3, MW = 140 a

OH HO

OCH3

(-) 173

OH

products

(-) 225

OH

|

products C6H6O3, MW = 128

OH

OH OH

HO

(-) 129

OH (-) 211

Fig. 10. Possible routes of methoxy loss in syringol gas-phase chemistry. Fig. 10. Possible routes of methoxy loss in syringol gas-phase chemistry.

OH

products

Discussion Paper

C6H6O2, MW = 110 products

13, 3485–3532, 2013


Title Page

b

d

OH

Discussion Paper

products

C7H8O2, MW = 124 OH OH OCH3

ACPD

Introduction

Conclusions

References

Tables

Figures

J

I

J

I

Back

Close

|

Abstract

Discussion Paper |

3532

Full Screen / Esc
