Characterization of gas-phase organics using proton transfer reaction time-of-flight mass spectrometry: fresh and aged residential wood combustion emissions

Abstract

Organic gases emitted during the flaming phase of residential wood combustion are characterized individually and by functionality using proton transfer reaction time-of-flight mass spectrometry. The evolution of the organic gases is monitored during photochemical aging. Primary gaseous emissions are dominated by oxygenated species (e.g., acetic acid, acetaldehyde, phenol and methanol), many of which have deleterious health effects and play an important role in atmospheric processes such as secondary organic aerosol formation and ozone production. Residential wood combustion emissions differ considerably from open biomass burning in both absolute magnitude and relative composition. Ratios of acetonitrile, a potential biomass burning marker, to CO are considerably lower ( ∼ 0.09pptvppbv^-1) than those observed in air masses influenced by open burning ( ∼ 1-2pptvppbv^-1), which may make differentiation from background levels difficult, even in regions heavily impacted by residential wood burning. A considerable amount of formic acid forms during aging ( ∼ 200-600mgkg^-1 at an OH exposure of (4.5-5.5) × 10⁷moleccm^-3h), indicating residential wood combustion can be an important local source for this acid, the quantities of which are currently underestimated in models. Phthalic anhydride, a naphthalene oxidation product, is also formed in considerable quantities with aging ( ∼ 55-75mgkg^-1 at an OH exposure of (4.5-5.5) × 10⁷moleccm^-3h). Although total NMOG emissions vary by up to a factor of ∼ 9 between burns, SOA formation potential does not scale with total NMOG emissions and is similar in all experiments. This study is the first thorough characterization of both primary and aged organic gases from residential wood combustion and provides a benchmark for comparison of emissions generated under different burn parameters.

Atmos. Chem. Phys., 17, 705720, 2017 www.atmos-chem-phys.net/17/705/2017/ doi:10.5194/acp-17-705-2017 Author(s) 2017. CC Attribution 3.0 License.

Emily A. Bruns1, Jay G. Slowik1, Imad El Haddad1, Dogushan Kilic1, Felix Klein1, Josef Dommen1, Brice Temime-Roussel2, Nicolas Marchand2, Urs Baltensperger1, and Andr S. H. Prvt1

1Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland

2Aix Marseille Univ, CNRS, LCE, Laboratoire de Chimie de lEnvironnement, UMR7376, 13331, Marseille, France

Correspondence to: Emily A. Bruns ([email protected]) and Andr S. H. Prvt ([email protected])

Received: 21 August 2016 Published in Atmos. Chem. Phys. Discuss.: 30 August 2016 Revised: 1 December 2016 Accepted: 11 December 2016 Published: 16 January 2017

Abstract. Organic gases emitted during the aming phase of residential wood combustion are characterized individually and by functionality using proton transfer reaction time-ofight mass spectrometry. The evolution of the organic gases is monitored during photochemical aging. Primary gaseous emissions are dominated by oxygenated species (e.g., acetic acid, acetaldehyde, phenol and methanol), many of which have deleterious health effects and play an important role in atmospheric processes such as secondary organic aerosol formation and ozone production. Residential wood combustion emissions differ considerably from open biomass burning in both absolute magnitude and relative composition. Ratios of acetonitrile, a potential biomass burning marker, to CO are considerably lower ( 0.09 pptv ppbv1[notdef] than those

observed in air masses inuenced by open burning ( 1

2 pptv ppbv1[notdef], which may make differentiation from background levels difcult, even in regions heavily impacted by residential wood burning. A considerable amount of formic acid forms during aging ( 200600 mg kg1 at an OH ex

posure of (4.55.5) 107 molec cm3 h), indicating residen

tial wood combustion can be an important local source for this acid, the quantities of which are currently underestimated in models. Phthalic anhydride, a naphthalene oxidation product, is also formed in considerable quantities with aging ( 5575 mg kg1 at an OH exposure of (4.5

5.5) 107 molec cm3 h). Although total NMOG emissions

vary by up to a factor of 9 between burns, SOA forma

tion potential does not scale with total NMOG emissions and is similar in all experiments. This study is the rst thorough characterization of both primary and aged organic gases from

Characterization of gas-phase organics using proton transfer reaction time-of-ight mass spectrometry: fresh and aged residential wood combustion emissions

residential wood combustion and provides a benchmark for comparison of emissions generated under different burn parameters.

1 Introduction

Residential wood combustion is a source of gaseous and particulate emissions in the atmosphere, including a complex mixture of non-methane organic gases (NMOGs; McDonald et al., 2000; Schauer et al., 2001; Hedberg et al., 2002; Jordan and Seen, 2005; Pettersson et al., 2011; Evtyugina et al., 2014; Reda et al., 2015). NMOGs impact climate (IPCC, 2013) and health (Pouli et al., 2003; Blling et al., 2009) both directly and through the formation of products during atmospheric processing (Mason et al., 2001; Kroll and Seinfeld, 2008; Shao et al., 2009), which makes NMOG characterization critical. Although two studies have speciated a large fraction of the NMOG mass emitted during residential wood combustion in commercial burners (McDonald et al., 2000; Schauer et al., 2001), these studies relied on ofine chromatographic approaches, which are time consuming in terms of sample preparation and analysis and can introduce both positive and negative artifacts (Nozire et al., 2015). Relatively recently, the proton transfer reaction mass spectrometer (PTR-MS) has emerged as a powerful tool for online quantication of atmospherically relevant NMOGs (Lindinger et al., 1998; Jordan et al., 2009), eliminating many of the artifacts associated with ofine approaches. NMOGs emitted during open burning of a variety of biomass fu-

Published by Copernicus Publications on behalf of the European Geosciences Union.

706 E. A. Bruns et al.: Fresh and aged residential wood combustion emissions

els in the laboratory have been recently quantied using a high-resolution proton transfer reaction time-of-ight mass spectrometer (PTR-ToF-MS; Stockwell et al., 2015), and select nominal masses were followed during aging of residential wood combustion emissions using a quadrupole PTRMS (Grieshop et al., 2009a). However, a complete high-resolution characterization of residential wood combustion emissions has yet to be performed.

The quantities and composition of NMOGs emitted during residential wood combustion are highly dependent on a number of parameters including wood type, appliance type and burn conditions, and as few studies have characterized these NMOGs (McDonald et al., 2000; Schauer et al., 2001;Hedberg et al., 2002; Jordan and Seen, 2005; Pettersson et al., 2011; Evtyugina et al., 2014; Reda et al., 2015), further work is needed to constrain emission factors, as highlighted in the recent review article by Nozire et al. (2015). Also, little is known about the evolution of NMOGs from residential wood combustion with aging.

In this study, we present results from the rst use of a smog chamber and a PTR-ToF-MS to characterize primary and aged gaseous emissions from residential wood combustion in real time. This novel approach allows for an improved characterization of NMOG emissions, particularly oxygenated NMOGs, which are a considerable fraction of the total NMOG mass emitted during residential wood combustion (McDonald et al., 2000; Schauer et al., 2001). This study focuses on a narrow set of burn conditions, namely the aming phase of beech wood combustion, in order to generate emissions that are as reproducible as possible for a complementary investigation of the effects of parameters such as temperature on the emissions. While these experiments are a narrow representation of real-world conditions, this novel work provides a benchmark and direction for future wood combustion studies.

2 Methods

2.1 Emission generation and smog chamber operation

Beech (Fagus sylvatica) logs are combusted in a residential wood burner (Fig. S1 in the Supplement; single combustion chamber, operated in single batch mode; Avant, 2009, Attika) and emissions are sampled from the chimney through a heated line (473 K), diluted by a factor of 810 us

ing an ejector diluter (473 K, DI-1000, Dekati Ltd.) and in

jected into the smog chamber ( 7 m3[notdef] through a heated

line (423 K). Emissions are sampled during the stable aming phase of the burn and modied combustion efciencies (MCEs), dened as the ratio between CO2 and the sum of

CO and CO2 range from 0.974 to 0.978 (Table 1).

Emissions are injected for 1121 min and total dilution factors range from 100200. All experiments are con

ducted under similar conditions with starting wood masses

in the burner of 2.9 0.3 kg and a wood moisture content

of 19 2 %. The smog chamber has an average temperature

of 287.0 0.1 K and a relative humidity of 55 3 % over

all ve experiments. Experimental parameters and primary emission values are summarized in Table S1 in the Supplement. After characterization of the primary emissions, as described below, a single dose of d9-butanol (2 L, butanol-D9, 98 %, Cambridge Isotope Laboratories) is injected into the chamber and a continuous injection of nitrous acid in air(2.32.6 L min1, 99.999 %, Air Liquide) into the cham

ber begins. The decay of d9-butanol measured throughout aging is used to estimate hydroxyl radical (OH) exposures (Barmet et al., 2012). Nitrous acid produces OH upon irradiation in the chamber and is used to increase the degree of aging. Levels of NOx in the chamber prior to aging are in the range of 160350 and increase to 250380 ppbv after

reaching OH exposures of (4.55.5) 107 molec cm3 h

(NOx data unavailable for experiment 1). The small continuous dilution in the chamber during aging, due to the constant nitrous acid injection, is accounted for using CO as an inert tracer. The chamber contents are irradiated with UV light (40 lights, 90100 W, Cleo Performance, Philips;Platt et al., 2013) for 4.56 h (maximum OH exposures of(4.76.8) 107 molec cm3 h which corresponds to 23

days of aging in the atmosphere at an OH concentration of 1 106 molec cm3[notdef]. Reported quantities of aged species

are taken at OH exposures of (4.55.5) 107 molec cm3 h

(Table 1; 1.92.3 days of aging in the atmosphere at an OH

concentration of 1 106 molec cm3; Barmet et al., 2012).

2.2 Gas-phase analysis

NMOGs with a proton afnity greater than that of water are measured using a PTR-ToF-MS (PTR-ToF-MS 8000, Ionicon Analytik GmbH) and CO2, CO and CH4 are measured using cavity ring-down spectroscopy (G2401, Picarro, Inc.). The PTR-ToF-MS operates with hydronium ion ([H2O+H]+[notdef] as the reagent, a drift tube pressure of 2.2 mbar,

a drift tube voltage of 543 V and a drift tube temperature of 90 C leading to a ratio of the electric eld (E) and the density of the buffer gas (N) in the drift tube (reduced electric eld, E/N) of 137 Townsend (Td). The transmission function is determined using a gas standard of six NMOGs of known concentration (methanol, acetaldehyde, propan-2-one, toluene, p-xylene, 1,3,5-trimethylbenzene; Carbagas).As the RH and temperature of the sampled air is similar in all experiments, changes in the detection efciency of individual species are not expected.

PTR-ToF-MS data are analyzed using the Tofware postprocessing software (version 2.4.5, TOFWERK AG, Thun, Switzerland; PTR module as distributed by Ionicon Analytik GmbH), running in the Igor Pro 6.3 environment (version 6.3, Wavemetrics Inc.). The minimum detection limit is taken as 3 standard deviations above the background, where the standard deviation is determined from the measurements

Atmos. Chem. Phys., 17, 705720, 2017 www.atmos-chem-phys.net/17/705/2017/

E. A. Bruns et al.: Fresh and aged residential wood combustion emissions 707

Table 1. Modied combustion efciencies, OH exposures of reported aged values (molec cm3 h) and enhancement of select species relative to CO enhancement above background levels (pptv ppbv1[notdef].

Experiment

Parameter 1 2 3 4 5 Average

MCE 0.975 0.978 0.977 0.974 0.978 0.976 0.002

OH exposure 4.5 10

7 5.5 10

7 5.3 10

7 5.2 10

7 4.7 10

7

[Delta1]CH3CNprimary / [Delta1]CO 0.079 0.11 0.099 0.077 0.082 0.09 0.01

[Delta1]CH3CNaged / [Delta1]CO 0.084 0.11 0.11 0.072 0.069 0.09 0.02

[Delta1]CH3OHprimary / [Delta1]CO 3.4 21 11 2.4 1.5 8 8

[Delta1]CH3OHaged / [Delta1]CO 3.4 19 11 2.5 1.8 7 7

[Delta1]C2H4O2primary / [Delta1]CO 12 84 57 9.8 5.9 30 30

[Delta1]C2H4O2aged / [Delta1]CO 12 68 48 9.4 6.5 30 30

Uncertainties correspond to one sample standard deviation of the replicates.

to which reactions leading to ions other than [M+H]+ occurs

is dependent on instrument parameters such as E/N. The unknown relative contributions of various isomers makes it difcult to account for reactions generating ions besides [M+H]+ and thus, no fragmentation corrections are applied.

Emission factors of compounds likely to undergo extensive reactions to form products besides [M+H]+ (i.e., methyl

cyclohexane (Midey et al., 2003), ethyl acetate (Baasandorj et al., 2015) and saturated aliphatic aldehydes (Buhr et al., 2002), with the exception of acetaldehyde) are not reported.Due to interferences, butenes ([C4H8+H]+[notdef] are not quanti

ed.

3 Results and discussion

3.1 NMOG emissions

In all experiments, the largest EFs for a single gas-phase species correspond to CO2 (17701790 g kg1[notdef] and CO (27

30 g kg1; Table 2), which are in good agreement with previous measurements from residential beech logwood combustion where CO2 EFs of 1800 and CO EFs of 20

70 g kg1 were measured (Ozil et al., 2009; Schmidl et al., 2011; Kistler et al., 2012; Evtyugina et al., 2014; Reda et al., 2015). Methane is also emitted in considerable quantities(1.52.8 g kg1[notdef], similar to previously observed values for beech wood burning in replaces (0.51 g kg1; Ozil et al., 2009), although at generally lower levels than total NMOGs(1.513 g kg1[notdef]. Total NMOG EFs from beech wood combustion have not been previously reported, but values are similar to studies of residential wood stove burning of different hardwoods which have attempted a detailed quantication of total NMOGs, such as McDonald et al. (2000;6.255.3 g kg1 for a hardwood mixture) and Schauer et al. (2001; 6.7 g kg1 for oak). Total NMOG quantities reported in this study refer to species quantied using the PTRToF-MS.

www.atmos-chem-phys.net/17/705/2017/ Atmos. Chem. Phys., 17, 705720, 2017

of each ion in the chamber prior to emission injection. Isotopic contributions are constrained during peak tting and are accounted for in reported concentrations. Possible molecular formulas increase with increasing m/z, making accurate peak assignments difcult in the higher m/z range. Mass spectral data from m/z 33 to m/z 130 are assigned molecular formulas, as well as the 18O isotope of the reagent ion and signal above m/z 130 corresponding to compounds previously identied during residential wood combustion (Mc-Donald et al., 2000; Schauer et al., 2001; Hedberg et al., 2002; Jordan and Seen, 2005; Pettersson et al., 2011; Evtyugina et al., 2014; Reda et al., 2015). All signal above m/z 130 is included in total NMOG mass quantication. Using this approach, 9497 % of the total NMOG mass measured us

ing the PTR-ToF-MS has an ion assignment.

The reaction rate constant of each species with the reagent ion in the drift tube is needed to convert raw signal to concentration. When available, individual reaction rate constants are applied to ions assigned a structure (Cappellin et al., 2012; Table S2), otherwise a default reaction rate constant of 2 109 cm3 s1 is applied. For possible isomers, the reac

tion rate constant is taken as the average of available values. Approximately 6070 % of the total NMOG mass is comprised of compounds with known rate constants. NMOG signal is normalized to [H182O+H]+ to convert to concentration.

Emission factors (EFs) normalize concentrations to the total wood mass burned (e.g., mg kg1 reads as milligrams of species emitted per kilogram of wood burned) to facilitate comparison between experiments and are calculated as described previously (Andreae and Merlet, 2001; Bruns et al., 2015a).

PTR-ToF mass spectrometry is a relatively soft ionization technique generally resulting in protonation of the parent NMOG ([M+H]+[notdef], although some compounds are known

to produce other ions, for example through fragmentation or rearrangement (e.g., Baasandorj et al., 2015). Reactions potentially leading to considerable formation of species besides [M+H]+ are discussed in the Supplement. The extent

708 E. A. Bruns et al.: Fresh and aged residential wood combustion emissions

Table 2. Primary emission factors of gas-phase species (mg kg1[notdef]a, b.Species Monoisotopic Structural assignmentc Functional group Experiment Averaged

m/z 1 2 3 4 5

CO2 1 780 000 1 781 000 1 777 000 1 772 000 1 784 000 1 779 000 4000

CO 27 000 26 000 27 000 30 000 27 000 28 000 2000

CH4 1800 1600 2000 2800 1500 1900 500

NMOG 2800 13 000 9200 3200 1500 6000 5000

acid 750 5000 3500 700 340 2000 2000

O-containing 560 3400 2200 590 290 1000 1000

carbonyl 310 1500 960 270 170 600 600

oxygenated aromatic 230 780 520 270 140 400 300

alcohol 130 660 360 90 48 300 300

furan 93 680 410 95 51 300 300

O- and N-containing 120 81 77 120 91 100 20

CxHy 120 210 210 160 64 150 60

aromatic hydrocarbon 320 170 490 680 250 400 200

N-containing 20 39 36 23 16 30 10

other 140 390 310 160 94 200 100

[CH3OH+H]+ 33.034 methanol alcohol 110 660 360 87 47 300 300

[C2H3N+H]+ 42.034 acetonitrile N-containing 3.4 3.4 4.1 3.6 3.2 3.5 0.3

[C3H6+H]+ 43.055 propene CxHy 38 61 40 28 15 40 20

[C2H4O+H]+ 45.034 acetaldehyde carbonyl 94 330 230 79 48 200 100

[CH2O2+H]+ 47.013 formic acid acid 9.9 96 100 31 4.2 50 50

[C2H6O+H]+ 47.050 ethanol alcohol 16 BDL 3.3 2.5 BDL 4 7

[C4H6+H]+ 55.055 buta-1,3-diene CxHy 14 38 33 14 5.7 20 10

[C3H4O+H]+ 57.034 prop-2-enal carbonyl 45 160 120 45 25 80 60

[C2H2O2+H]+ 59.013 glyoxal carbonyl BDL BDL BDL 1.3 BDL 0.3 0.6

[C3H6O+H]+ 59.050 propan-2-one carbonyl 54 190 120 30 30 80 70

propanal

[C2H4O2+H]+ 61.029 acetic acid acid 740 4900 3400 670 340 2000 2000

glycolaldehyde[C4H4O+H]+ 69.034 furan furan 17 140 82 19 9.7 50 60

[C5H8+H]+ 69.070 isoprene CxHy 3.4 12 9.4 2.8 1.1 3 2

cyclopentene[C4H6O+H]+ 71.050 (E)-but-2-enal carbonyl 25 120 72 19 14 50 40

3-buten-2-one 2-methylprop-2-enal[C5H10+H]+ 71.086 (E)-/(Z)-pent-2-ene CxHy 2.7 5.3 4.0 2.0 0.86 3 2

2-methylbut-1-ene2-methylbut-2-enepent-1-ene3-methylbut-1-ene[C3H4O2+H]+ 73.029 2-oxopropanal carbonyl 26 140 96 26 15 60 50

[C4H8O+H]+ 73.065 butan-2-one carbonyl 7.2 44 24 5.2 4.2 20 20

butanal2-methylpropanal[C3H6O2+H]+ 75.045 methyl acetate O-containing 62 490 300 56 28 200 200

[C6H6+H]+ 79.055 benzene aromatic hydrocarbon 210 90 300 450 150 200 100

[C5H6O+H]+ 83.050 2-methylfuran furan 21 160 88 21 12 60 60

[C5H8O+H]+ 85.065 3-methyl-3-buten-2-one carbonyl 10 69 39 8.7 5.4 30 30

[C6H12+H]+ 85.102 (E)-hex-2-ene CxHy BDL 2.2 1.6 0.60 BDL 1 1

2-methyl-pent-2-ene[C4H6O2+H]+ 87.045 butane-2,3-dione carbonyl 51 450 250 52 26 200 200

[C7H8+H]+ 93.070 toluene aromatic hydrocarbon 23 22 34 39 16 27 9

[C6H6O+H]+ 95.050 phenol oxygenated aromatic 110 110 130 130 68 110 20

[C5H4O2+H]+ 97.029 furan-2-carbaldehyde furan 40 270 180 40 21 100 100

[C6H8O+H]+ 97.065 2,4-/2,5-dimethylfuran furan 11 86 48 11 5.5 30 30

[C4H2O3+H]+ 99.008 maleic anhydride

e O-containing 40 91 66 40 26 50 30

[C8H8+H]+ 105.070 styrene aromatic hydrocarbon 12 8.0 20 24 9.6 15 7

[C7H6O+H]+ 107.050 benzaldehyde oxygenated aromatic 18 14 23 27 11 18 7

[C8H10+H]+ 107.086 m-/o-/p-xylene aromatic hydrocarbon 4.2 6.9 7.5 6.3 2.9 6 2

ethylbenzene[C7H8O+H]+ 109.065 m-/o-/p-cresol oxygenated aromatic 24 71 48 25 14 40 20

[C6H6O2+H]+ 111.045 m-/o-/p-benzenediol oxygenated aromatic 26 150 86 22 14 60 50

2-methylfuraldehyde[C9H8+H]+ 117.070 1H-indene aromatic hydrocarbon 5.0 BDL 9.5 15 2.9 6 6

[C9H10+H]+ 119.086 2,3-dihydro-1H-indene aromatic hydrocarbon 2.3 2.8 3.9 3.3 1.3 3 1

[C8H8O+H]+ 121.065 1-phenylethanone 3-/4-methylbenzaldehyde oxygenated aromatic 8.3 14 13 8.8 4.6 10 4

[C9H12+H]+ 121.102 i-propylbenzene aromatic hydrocarbon 1.0 2.4 2.3 1.2 0.68 1.5 0.8

n-propylbenzene1,3,5-trimethylbenzene[C8H10O+H]+ 123.081 2,4-/2,6-/3,5-dimethylphenol oxygenated aromatic 4.7 36 18 4.9 3.0 10 10

[C7H8O2+H]+ 125.060 2-methoxyphenol oxygenated aromatic 9.2 110 55 12 4.9 40 50

methylbenzenediols[C6H6O3+H]+ 127.040 5-(hydroxymethyl)furan-2-carbaldehyde furan 4.4 29 17 4.9 2.7 10 10

[C10H8+H]+ 129.070 naphthalene aromatic hydrocarbon 42 20 80 100 33 60 30

[C8H10O2+H]+ 139.076 2-methoxy-4-methylphenol oxygenated aromatic 3.2 59 29 6.2 1.8 20 20

4-(2-hydroxyethyl)phenol[C11H10+H]+ 143.086 1-/2-methylnaphthalene aromatic hydrocarbon 4.0 2.3 5.7 7.5 3.3 5 2

[C9H6O2+H]+ 147.045 indene-1,3-dione oxygenated aromatic 11 13 13 11 6.0 11 3

[C8H4O3+H]+ 149.024 phthalic anhydride

e O-containing 16 31 25 16 8.3 19 9

[C8H8O3+H]+ 153.055 4-hydroxy-3-methoxybenzaldehyde oxygenated aromatic 3.8 27 15 3.7 1.4 10 10

[C12H8+H]+ 153.070 acenaphthylene aromatic hydrocarbon 6.1 3.6 12 15 8.3 9 5

Atmos. Chem. Phys., 17, 705720, 2017 www.atmos-chem-phys.net/17/705/2017/

E. A. Bruns et al.: Fresh and aged residential wood combustion emissions 709

Table 2. Continued.

Species Monoisotopic Structural assignmentc Functional group Experiment Averaged

m/z 1 2 3 4 5

[C9H12O2+H]+ 153.092 4-ethyl-2-methoxyphenol oxygenated aromatic 1.4 30 14 3.2 BDL 10 10

1,2-dimethoxy-4-methylbenzene[C8H10O3+H]+ 155.071 2,6-dimethoxyphenol oxygenated aromatic 2.2 73 35 7.8 1.0 20 30

[C12H10+H]+ 155.086 1,1-biphenyl aromatic hydrocarbon 3.1 BDL 4.3 6.1 2.9 3 2

1,2-dihydroacenaphthylene[C12H12+H]+ 157.102 dimethylnaphthalene aromatic hydrocarbon 1.3 3.0 3.2 2.2 1.2 2.2 0.9

[C10H12O2+H]+ 165.092 2-methoxy-4-[(E)-prop-1-enyl]phenol oxygenated aromatic 0.92 24 13 2.3 0.59 8 10

2-methoxy-4-prop-2-enylphenol2-methoxy-4-[(Z)-prop-1-enyl]phenol[C9H10O3+H]+ 167.071 1-(4-hydroxy-3-methoxyphenyl)ethanone oxygenated aromatic 2.5 11 6.7 2.2 1.2 5 4

2,5-dimethylbenzaldehyde3,4-dimethoxybenzaldehyde[C13H10+H]+ 167.086 uorene aromatic hydrocarbon BDL BDL 1.0 2.5 2.0 1 1

[C10H14O2+H]+[notdef] 167.107 2-methoxy-4-propylphenol oxygenated aromatic 0.88 7.6 4.4 1.1 BDL 3 3

[C9H12O3+H]+ 169.086 2,6-dimethoxy-4-methylphenol oxygenated aromatic BDL 14 6.2 1.1 BDL 4 6

[C14H10+H]+ 179.086 phenanthrene aromatic hydrocarbon 6.4 8.4 6.1 3.6 7.7 6 2

anthracene[C13H8O+H]+ 181.065 uoren-9-one oxygenated aromatic 2.7 4.0 2.7 1.2 1.9 2 1

phenalen-1-one[C10H12O3+H]+ 181.086 1-(4-hydroxy-3-methoxyphenyl)propan-2-one oxygenated aromatic BDL 4.2 2.6 1.1 0.69 2 2

[C9H10O4+H]+ 183.066 3,4-dimethoxybenzoic acid oxygenated aromatic 1.1 BDL 1.4 1.1 1.0 0.9 0.5

4-hydroxy-3,5-dimethoxybenzaldehyde[C10H14O3+H]+ 183.102 4-ethyl-2,6-dimethoxyphenol oxygenated aromatic 1.0 7.4 4.2 1.0 BDL 3 3

[C15H12+H]+ 193.102 1-/2-/3-/9-methylphenanthrene aromatic hydrocarbon 0.50 2.6 1.3 BDL 0.44 1 1

2-methylanthracene[C11H14O3+H]+ 195.102 1,3-dimethoxy-2-prop-2-enoxybenzene oxygenated aromatic BDL 1.7 1.2 BDL BDL 0.6 0.8

2,6-dimethoxy-4-[(Z)-prop-1-enyl]phenol[C16H10+H]+ 203.086 uoranthene aromatic hydrocarbon BDL 0.87 BDL BDL BDL 0.2 0.4

pyrene acephenanthrylene

a CO2, CO and CH4 are measured using cavity ring down spectroscopy and all other species are measured using the PTR-ToF-MS. b BDL indicates value is below the detection limit. c Multiple structural assignments for a given ion correspond to possible isomers. d Uncertainties correspond to one sample standard deviation of the replicates. e Structural assignment based on known products produced during oxidation of aromatics (Bandow et al., 1985; Chan et al., 2009; Praplan et al., 2014).

ions based on previously identied species (McDonald et al., 2000; Schauer et al., 2001; Hedberg et al., 2002; Jordan and Seen, 2005; Pettersson et al., 2011; Evtyugina et al., 2014; Reda et al., 2015). A few small, unambiguous ions are also assigned a structure, including methanol, formic acid and acetonitrile. Approximately 70 % of the total NMOG mass measured using the PTR-ToF-MS is assigned a structure based on this method.

NMOGs are categorized by functional groups including oxygenated, total CxHy, nitrogen-containing and other. Oxygenated subcategories include the following: acids (comprised of non-aromatic acids), carbonyls (comprised of non-aromatic carbonyls), oxygenated aromatics (not including furans), furans, O-containing (comprised of structurally unassigned oxygenated compounds and multifunctional oxygenated compounds) and O- and N-containing (comprised of species containing both oxygen and nitrogen atoms). Species categorized as N-containing contain no oxygen atoms. Total CxHy subcategories include: aromatic hydrocarbons, and non-aromatic and structurally unassigned species (referred to as CxHy in the text and gures). Higher molecular weight species lacking an ion assignment are categorized as other.In the case of possible isomers, ions are categorized according to the species most likely to dominate based on previous

www.atmos-chem-phys.net/17/705/2017/ Atmos. Chem. Phys., 17, 705720, 2017

Although a large fraction of atmospherically relevant organic gases are measured using the PTR-ToF-MS, some species are not quantitatively detected, including those with a proton afnity less than water (i.e., small alkanes). Based on previous studies of residential burning, alkanes are estimated to contribute less than 5 % to the NMOG mass of

either hard or soft wood and the sum of alkenes and alkynes, some of which are quantiable with the PTR-ToF-MS, are estimated to contribute less than 15 % to the total mea

sured NMOG mass (McDonald et al., 2000; Schauer et al., 2001).

Figure 1 shows the primary NMOG mass spectrum for each experiment classied by NMOG functionality and the fractional contribution of NMOG functional groups to the total NMOG mass. EFs for individual compounds are presented in Table 2. For ease of reading, nominal m/z is presented in the text and gures; however, monoisotopic m/z for all identied species can be found in Tables 2 and S3. Separation of isobaric species is possible using the PTR-ToFMS, although isomers remain indistinguishable. Quantities of gas-phase species generated during residential wood combustion depend on a variety of parameters, such as type of burner and wood species. However, many compounds are commonly emitted and structures are assigned to observed

710 E. A. Bruns et al.: Fresh and aged residential wood combustion emissions

5000

4000

3000

2000

1000

0

(a)

61

(b)

61

Emission factor (mg kg)

-1

800 700 600 500 400 300 200 100

0

Acid

O-containing

Carbonyl

Oxygenated

aromatic

Alcohol

Furan

O- and N-

containing

Aromatic

hydrocarbon

CxHy

N-containing

Other

Emission factor (mg kg)

-1

Emission factor (mg kg)

-1

43

79

43

95

75

50

75

100

125

150

175

200

50

75

100

125

150

175

200

m/z m/z

(c)

(d)

Emission factor (mg kg)

-1

3500 3000 2500 2000 1500 1000

500 0

61

61

79

43

43

95 129

75

50

75

100

125

150

175

200

50

75

100

125

150

175

200

m/z

m/z

(e) (f)

Emission factor (mg kg)

-1

350 300 250 200 150 100

50

0

79

Fractional contribution

to total NMOG mass

700 600 500 400 300 200 100

0

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

61

43

95

129

1 2 3 4 5 Average

50

75

100

125

150

175

200

m/z

Experiment

Figure 1. Mass spectra of primary NMOG emissions for experiments 15 (ae) colored by functional group. (ae) Labeled peaks correspond to [C2H3O]+ (m/z 43, fragment from higher molecular weight compounds), [C2H4O2+H]+ (m/z 61, acetic acid), [C3H6O2+H]+ (m/z 75,

methyl acetate), [C6H6+H]+ (m/z 79, benzene), [C6H6O+H]+ (m/z 95, phenol) and [C10H8+H]+ (m/z 129, naphthalene). The bars in

(f) correspond to the fractional contribution of each functional group to the total NMOG mass for each experiment and the average of all experiments. Error bars correspond to one sample standard deviation of the replicates. Legend in (b) applies to (a)(f).

studies (McDonald et al., 2000; Schauer et al., 2001; Hedberg et al., 2002; Jordan and Seen, 2005; Pettersson et al., 2011; Evtyugina et al., 2014; Reda et al., 2015).

Oxygenated species contribute 6894 % to the total pri

mary NMOG mass, which has important atmospheric implications due to the role of these compounds in photochemical reactions, for example by altering O3 and peroxide formation (Mason et al., 2001; Shao et al., 2009). McDonald et al. (2000) and Schauer et al. (2001) previously ob-

served the dominance of oxygenated NMOGs during residential burning of other wood types, whereas Evtyugina et al. (2014) found that benzene and benzene derivatives contributed 59 % to the total measured NMOGs, compared to only 26 % from oxygenated compounds for residential burning of beech wood in a woodstove. However, Evtyugina et al. (2014), as well as McDonald et al. (2000) and Schauer et al. (2001), did not include emissions from all lower molecular weight NMOGs, such as acetic acid. Oxygenated NMOGs

Atmos. Chem. Phys., 17, 705720, 2017 www.atmos-chem-phys.net/17/705/2017/

E. A. Bruns et al.: Fresh and aged residential wood combustion emissions 711

are also reported as a large fraction of NMOGs emitted during open burning of many biomass fuels (Gilman et al., 2015;Stockwell et al., 2015).

Acids are the most abundant subclass of species in all experiments with an average EF of 2000 2000 mg kg1,

and acetic acid ([C2H4O2+H]+ at nominal m/z 61) is the

most highly emitted compound in all experiments. In addition to acetic acid, [C2H4O2+H]+ can correspond to gly

colaldehyde; however, Stockwell et al. (2015) found that acetic acid contributes 7593 % to [C2H4O2+H]+ dur

ing open burning of black spruce (Picea mariana) and ponderosa pine (Pinus ponderosa) and thus, it is expected that this ion is also largely attributable to acetic acid in the current study. Acetic acid and formic acid ([CH2O2+H]+ at nomi

nal m/z 47) are the most abundant carboxylic acids in the atmosphere and are important contributors to atmospheric acidity (Chebbi and Carlier, 1996). However, the sources of these acids are poorly understood (Paulot et al., 2011) and data on their EFs from residential wood combustion are relatively unknown. The high acetic acid EFs found here indicate that residential wood combustion can be an important local source of this acid. Interestingly, the enhancement of acetic acid ([Delta1]C2H4O2[notdef] over background levels relative to

CO enhancement ([Delta1]CO) in the current study ranges from

6 to 80 pptv ppbv1 (Table 1), which is much higher than the average 0.58 pptv ppbv1 (sum of gas and aerosol phase) measured in an Alpine valley heavily impacted by residential wood combustion in winter (Gaeggeler et al., 2008). Further work is needed to investigate the source of this discrepancy, as limited ambient measurements are available from regions heavily impacted by residential wood combustion. However, it is possible that the ambient measurements were dominated by emissions produced during poor burning conditions (e.g., starting phase) where CO EFs are expected to be higher than during the stable burning phase investigated in the current study.

The sum of oxygenated and non-oxygenated aromatic compounds contribute 730 % (800 300 mg kg1[notdef] to the

total primary NMOG mass with benzene ([C6H6+H]+ at

nominal m/z 79), phenol ([C6H6O+H]+ at nominal m/z 95),

and naphthalene ([C10H8+H]+ at nominal m/z 129) as the

three most dominant species. Oxidation products of aromatic species are the largest contributors to residential wood combustion SOA in this study (Bruns et al., 2016) and both aromatic and related oxidation products are of interest due to their particularly deleterious effects on health (Fu et al., 2012).

For the other functional group categories, carbonyl and alcohols contribute 812 % (600 600 mg kg1[notdef] and 3

5 % (300 300 mg kg1[notdef], respectively, to the total NMOG

mass. In general, the most highly emitted carbonyl compound is acetaldehyde ([C2H4O+H]+ at nominal m/z 45).

Methanol ([CH3OH+H]+ at nominal m/z 33) is the most

highly emitted alcohol, although other acyclic alcohols can undergo extensive fragmentation in the mass spectrometer.

10

8

6

4

2

0

0

2

4

6

8

10

Enhancement

Acid

O-containing

Carbonyl

Oxygenated aromatic

Alcohol

Furan

O- and N-containing

Aromatic hydrocarbon

CxHy

N-containing

Other

SOA potential

Figure 2. Enhancement (average value (mg kg1[notdef] of experiments 2 and 3 relative to the average value of experiments 1, 4 and 5) in each

NMOG functional group category and for SOA formation potential.

Total SOA formation potential is determined using the primary EF of each NMOG identied as a SOA precursor and literature SOA yields and assumes complete consumption of each NMOG with aging (see text for details). Error bars correspond to one sample standard deviation.

Furans are only a minor contributor to the total primary NMOG mass, contributing 35 % (300 300 mg kg1[notdef],

but are of potential interest as several furans were recently identied as SOA precursors (Gmez Alvarez et al., 2009) and possible open biomass burning markers (Gilman et al., 2015).

3.2 Burn variability

Although the same compounds are emitted during all burns, there is variability in EFs between experiments despite efforts to replicate burns as closely as possible and the fact that the MCE for each experiment falls within a narrow range(0.9740.978; Table 1). Experiments 2 and 3 show marked differences in total NMOG EFs and NMOG composition compared to experiments 1, 4 and 5. For example, the total NMOG EF is 9 times higher in experiment 2 compared

to experiment 5 (Table 2). Acetic acid EFs vary by a factor of 15 between burns, with high emissions in experiments

2 and 3 relative to experiments 1, 4 and 5. The total emission of oxygenated species also correlates with acetic acid emissions, with total oxygenated EFs considerably higher in experiments 2 and 3 than in experiments 1, 4 and 5. In contrast, aromatic hydrocarbons and CxHy EFs show no correlation with total oxygenated species or acetic acid EFs. Interestingly, differences in black carbon EFs, primary organic aerosol EFs and primary organic aerosol mass to black car-

www.atmos-chem-phys.net/17/705/2017/ Atmos. Chem. Phys., 17, 705720, 2017

712 E. A. Bruns et al.: Fresh and aged residential wood combustion emissions

bon ratios are also not observed between these two groupings of experiments (2, 3 and 1, 4, 5), as presented previously (Bruns et al., 2016). Enhancements in the average EF for the different functional groups in experiments 2 and 3 relative to experiments 1, 4 and 5 are shown in Fig. 2.

The differences in EFs due to inter-burn variability illustrate the difculty in constraining EFs from residential wood combustion. The burner is housed in an uninsulated building and the emission prole variability could be due to effects of outdoor temperature variability on the burner. For example, emission proles from burning lignite and pyrolysis of bark and other biomass sources have been shown to vary with burn temperature (Hansson et al., 2004; yc et al., 2011). Further work to constrain the possible range of EFs generated under different conditions is critical for improving model inputs.EFs are also dependent on factors such as appliance type and fuel loading, and further work is needed to characterize the emissions and the evolution of these emissions with aging generated from burning of different wood types and under different burn parameters.

3.3 Biomass burning tracers

Individual compounds emitted exclusively or in large quantities during biomass burning are of interest for source apportionment, and compounds contributing to SOA formation are of particular interest for climate and health (Fig. 3).Acetonitrile is used as an ambient gas-phase marker for open biomass burning (de Gouw et al., 2003; Singh et al., 2003). In the current experiments, acetonitrile EFs are relatively low (3.5 0.3 mg kg1[notdef] compared to open biomass

burning ( 20-1000 mg kg1; Yokelson et al., 2008, 2009;

Akagi et al., 2013; Stockwell et al., 2015). The enhancements of acetonitrile over background levels relative to CO enhancement, [Delta1]CH3CN / [Delta1]CO, are 0.080.1 pptv ppbv1

(Table 1). This is slightly lower than the only previously published residential wood combustion measurements (0.1 to0.8 pptv ppbv1; Grieshop et al., 2009a), but is much lower than [Delta1]CH3CN / [Delta1]CO measurements in ambient air masses impacted by open biomass burning ( 12 pptv ppbv1[notdef]

(Holzinger et al., 1999; Andreae and Merlet, 2001; Christian et al., 2003; de Gouw et al., 2003; Jost et al., 2003;Holzinger et al., 2005; de Gouw et al., 2006, 2009; Warneke et al., 2006; Yokelson et al., 2008, 2009; Aiken et al., 2010;Akagi et al., 2013). However, [Delta1]CH3CN / [Delta1]CO during open burning has been shown to depend strongly on fuel type;Stockwell et al. (2015) observed [Delta1]CH3CN / [Delta1]CO values from 0.0060 to 7.1 pptv ppbv1 for individual open burns of different biomass types in the laboratory. In agreement with the current study, ambient measurements of acetonitrile made in Colorado (USA) were not associated with fresh residential burning emissions (Coggon et al., 2016). Lower ambient measurements of nitrogen-containing NMOGs (including acetonitrile) during residential burning compared to open burning were attributed to the generally lower nitrogen

104

103

Emission factor (mg kg)

-1

102

101

100

2-methylprop-2-enal/(2E)-2-butenal

4-(2-hydroxyethyl)phenol/2-methoxy-4-methylphenol

10-1

Acetic acid

Benzene

Methanol

Phenol

Furan

Toluene

2-methoxyphenol

Prop-2-enal

Naphthalene

2-/3-methylfuran

o-benzenediol

m-/o-cresol

2,4-/2,5-dimethylfuran

Benzaldehyde

2,4-/2,6-/3,5-dimethylphenol

Styrene

2,6-dimethoxyphenol

Acenaphthylene

1-/2-methylnaphthalene

m-xylene

Acetonitrile

1,2-dihydroacenaphthylene

1,2-dimethylnaphthalene

Figure 3. Geometric mean of the primary emission factors for gas-phase species of particular interest for SOA formation (solid bars and gray patterned bars) and identication of air masses inuenced by biomass burning (black patterned bars). Colors and patterns corresponding to NMOGs contributing to SOA formation are consistent with Bruns et al. (2016). Error bars correspond to the sample geometric standard deviation of the replicates.

content in fuels burned residentially (Coggon et al., 2016).

Lower nitrogen content of the fuel is likely a contributor to the relatively low acetonitrile emissions in the current study.

The primary emission factors of other nitrogenated species, such as C3H3N (likely corresponding to acrylonitrile) and HNCO ranged in our study from 3.6 to 6.4 mg kg1 and BDL (below detection limit) to 11 mg kg1, respectively. Emission factors of C3H3N in the current study are lower than those observed during open burning (e.g., 10

90 mg kg1; Akagi et al., 2013), as expected based on the lower acetonitrile emission factors observed in the current study and the ndings of Coggon et al. (2016).

Further work is needed to investigate CH3CN emissions from residential burning of other wood types, as well as emissions during other burning phases (e.g., smoldering). How-

Atmos. Chem. Phys., 17, 705720, 2017 www.atmos-chem-phys.net/17/705/2017/

E. A. Bruns et al.: Fresh and aged residential wood combustion emissions 713

ever, these low enhancements may be difcult to differentiate from ambient background levels, making acetonitrile a poor marker for residential wood combustion under these burning conditions. Coggon et al. (2016) concluded that acetonitrile may not be a good tracer for residential burning in urban areas.

The interference from isobaric compounds when quantifying acetonitrile using a PTR-MS is an important consideration when high-resolution data are not available. Previously, several studies have determined that this interference is minimal during open biomass burning (de Gouw et al., 2003;Warneke et al., 2003, 2011; Christian et al., 2004). Recently, Dunne et al. (2012) quantied interferences with acetonitrile measurements in polluted urban air using a quadrupole PTR-MS and found contributions of 541 % to m/z 42 from non-acetonitrile ions including [C3H6]+ and the 13C isotope contribution from [C3H5]+. In the current study, in addition to contributions from [C3H6]+ and the isotopic contribution from [C3H5]+, 3050 % of the total signal at m/z 42 is due

to [C2H2O]+, which is presumably a fragment from higher molecular weight species. The total contribution to m/z 42 from species besides acetonitrile is 7085 %. Although an

investigation into the effects of the PTR-MS operating conditions (e.g., [O2]+ signal from ion source, E/N affecting fragmentation) is outside the scope of the current study, the possibility of considerable non-acetonitrile signal at m/z 42 should be taken into consideration when using nominal mass PTR-MS data to quantify acetonitrile from residential wood combustion.

Methanol is also used to identify air masses inuenced by open biomass burning, and enhancement over background levels relative to CO enhancement ([Delta1]CH3OH/[Delta1]CO)

is typically 180 pptv ppbv1 in ambient and laboratory

measurements of fresh open biomass burning emissions (Holzinger et al., 1999; Goode et al., 2000; Andreae and Merlet, 2001; Christian et al., 2003; Yokelson et al., 2003;Singh et al., 2004; Tabazadeh et al., 2004; Holzinger et al., 2005; de Gouw et al., 2006; Gaeggeler et al., 2008; Yokelson et al., 2008, 2009; Akagi et al., 2013; Stockwell et al., 2015; Mller et al., 2016). Here, we nd similar values ranging from 2 to 20 pptv ppbv1 (Table 1), in agreement with

Gaeggeler et al. (2008) who measured a [Delta1]CH3OH / [Delta1]CO value of 2.16 pptv ppbv1 in an Alpine valley heavily impacted by residential wood combustion emissions in winter.

3.4 Chamber studies of NMOG aging

Previous investigations of aged residential wood combustion emissions have largely focused on the evolution of the aerosol phase (Grieshop et al., 2009a, b; Hennigan et al., 2010; Heringa et al., 2011; Bruns et al., 2015a, b, 2016) and little is known about the evolution of the gas phase.The evolution of the NMOG functional group categories with increasing OH exposure is shown in Fig. 4. Figure 5 shows the absolute change in mass spectral signal between

the aged and primary NMOG quantities. Although an increase in NMOG mass could be expected with aging due to oxygenation, total NMOG mass decreases by 530 %

at an OH exposure of (4.65.5) 107 molec cm3 h relative

to the primary emissions in experiments 14, likely due to the conversion of species from the gas to particle phase, the mass of which increased considerably with aging (Bruns et al., 2016), and the formation of gas-phase species not quantied here (e.g., formaldehyde). Previous investigation of these experiments determined that the conversion of NMOGs traditionally included in models to SOA accounts for only

327 % of the observed SOA, whereas 84116 % of

the SOA is explained by inclusion of non-traditional precursors, including naphthalene and phenol (Bruns et al., 2016).The total NMOG mass increases slightly, by 5 %, in ex

periment 5. Quantities of individual NMOGs and NMOG functional group categories, after reaching an OH exposure of (4.6-5.5) 107 molec cm3 h, are presented in Table S3.

In addition to gas-to-particle phase partitioning and formation of gas-phase species not quantied here, a decrease in NMOG mass with aging could also be due to losses of gas-phase species to the chamber walls (Zhang et al., 2014;Bian et al., 2015). Measurements of NMOGs in the chamber prior to aging are stable, indicating that the chamber walls are not a sink for NMOGs, but rather that NMOGs are in equilibrium with the chamber walls, particles and the gas phase. Zhang et al. (2014) show that the rate of NMOG wall loss is inversely proportional to seed aerosol concentration and OH concentration, both of which are relatively high in the current experiments (Table S1; OH concentrations were

1.4 107 molec cm3[notdef]. Under these experimental condi

tions, NMOG wall losses are not expected to be large. Future studies are needed to investigate vapor wall loss of residential wood combustion emissions during aging.

Subcategories of oxygenated species behave differently with aging. For example, total quantities (mg kg1[notdef] of oxygenated aromatic species decrease by factors of 715 and

furan quantities decrease by factors of 49, whereas all

other oxygenated subcategories, as well as N-containing species, remain within a factor of 2 of primary values at an OH exposure of (4.65.5) 107 molec cm3 h. Aromatic

hydrocarbons and CxHy quantities decrease with aging by factors of 1.53. The large decreases in oxygenated aro

matic species and furans illustrate the highly reactive nature of these species with respect to OH. The evolution of the bulk NMOG elemental composition during aging is shown in Fig. S2.

In all experiments, formic acid quantities increase considerably with aging (by factors of 550), as do

[C4H2O3+H]+ quantities at nominal m/z 99 (by factors of 2-3, and which likely corresponds to maleic anhydride), both of which are formed during the oxidation of aromatic species among other compounds (Bandow et al., 1985; Sato et al., 2007; Praplan et al., 2014). However, the fragment resulting from the loss of water from maleic acid cannot be dis-

www.atmos-chem-phys.net/17/705/2017/ Atmos. Chem. Phys., 17, 705720, 2017

714 E. A. Bruns et al.: Fresh and aged residential wood combustion emissions

1000

800 600 400 200

0

Concentration (mg kg)

-1

(a)

(b)

Concentration (mg kg)

6000

-1 5000

4000

3000

2000

1000

0

0 10 20 30 40 50 60x106

0

10

20

30 40x106

OH exposure (molec cm-3 h)

OH exposure (molec cm-3 h)

OH exposure (molec cm-3 h)

OH exposure (molec cm-3 h)

Concentration (mg kg)

-1

Concentration (mg kg)

-1

4000

3000

2000

1000

0

0 10 20 30 40 50 60x106

(d)

Concentration (mg kg)

-1

1000

800 600 400 200

0

0 10 20 30 40 50x106

(c)

600

500

400

300

200

100

0

(e)

Acid

O-containing

Carbonyl

Oxygenated

aromatic Alcohol

Furan

O- and N-

containing Aromatic

hydrocarbon CxHy

N-containing

0

10 20 30 40 50x106

OH exposure (molec cm-3 h)

Figure 4. Temporal evolution of gas-phase species categorized by functional group throughout aging in the smog chamber for experiments 15 (ae). Units on the y axes are mass of each functional group (mg) per mass of wood consumed (kg).

tinguished from maleic anhydride using the PTR-ToF-MS.

Formic acid is underestimated in models, likely due to missing secondary sources (Paulot et al., 2011), and these results indicate that aging of residential wood combustion emissions can result in considerable secondary formic acid production.The signal at m/z 149, corresponding to [C8H4O3+H]+, in

creases by factors of 27 with aging. This ion likely corre

sponds to phthalic anhydride, which is a known naphthalene oxidation product (Chan et al., 2009).

Acetic acid formation has been observed in some ambient, open biomass burning plumes with aging (Goode et al., 2000; Hobbs et al., 2003; Yokelson et al., 2003), whereas it has not in others (de Gouw et al., 2006), and a doubling

of m/z 61, likely dominated by acetic acid, was observed during aging of residential burning emissions in a previous laboratory study (Grieshop et al., 2009a). In the current study, no increase in the average acetic acid concentration relative to CO[notdef]g[notdef] is observed (Table 1). Note that this implies production of secondary acetic acid that compensates for the expected consumption of 810 % of primary

acetic acid by reaction with OH at an OH exposure of (4.55.5) 107 molec cm3 h. These results indicate that acetic

acid from residential burning of beech wood is dominated by primary emissions of this species (Table 1). As with acetic acid, there are discrepancies in methanol behavior as open biomass burning plumes undergo aging (Goode et al., 2000;

Atmos. Chem. Phys., 17, 705720, 2017 www.atmos-chem-phys.net/17/705/2017/

E. A. Bruns et al.: Fresh and aged residential wood combustion emissions 715

300

47

900

-1 )

200

-1 )

600

47

47

D with aging

(aged-primary; mg kg

D with aging

(aged-primary; mg kg

100

149

149

149

300

99

149

0

0

-100

79

99

129

-300

95

97

-200

-600

(a)

(c)

(b)

(d)

-300

-900

61

50

75

100

125

150

175

200

50

75

100

125

150

175

200

m/z

m/z

600

300

47

-1 )

-1 )

400

200

D with aging

(aged-primary; mg kg

D with aging

(aged-primary; mg kg

200

99

100

99

149

0

0

-200

79 95 129

97

-100

-400

-200

61

-600

-300

50

75

100

125

150

175

200

50

75

100

125

150

175

200

m/z

m/z

150

Fractional contribution

to total NMOG mass

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

47

(f)

-1 )

100

D with aging

(aged-primary; mg kg

50

61

99

0

-50

79

129

95

-100

(e)

-150

50

75

100

125

150

175

200

1 2 3 4 5 AverageExperiment

m/z

Furan

Carbonyl

Oxygenated aromatic

Alcohol

O- and N-containing

Aromatic

hydrocarbon

CxHy

N-containing

Other

Acid

O-containing

Figure 5. Absolute difference of aged and primary mass spectra for experiments 15 (ae), where peaks less than zero decrease during aging and peaks greater than zero increase during aging. Aged emissions correspond to an OH exposure of (4.55.5) 10

7 molec cm3 h.

(ae) Labeled peaks correspond to [CH2O2+H]+ (m/z 47, formic acid), [C2H4O2+H]+ (m/z 61, acetic acid), [C6H6+H]+ (m/z 79,

benzene), [C6H6O+H]+ (m/z 95, phenol), [C5H4O2+H]+ (m/z 97, furan-2-carbaldehyde), [C4H2O3+H]+ (m/z 99, maleic anhydride),

[C10H8+H]+ (m/z 129, naphthalene) and [C8H4O3+H]+ (m/z 149, phthalic anhydride). The bars in (f) correspond to the fractional con

tribution of each category to the total NMOG EF at an OH exposure of (4.55.5) 10

7 molec cm3 h for each experiment and the average of all experiments. Error bars correspond to one sample standard deviation of the replicates.

Yokelson et al., 2003; Tabazadeh et al., 2004; Holzinger et al., 2005; de Gouw et al., 2006; Akagi et al., 2013). As described by Akagi et al. (2013), methanol enhancement has been hypothesized to correlate with terpene concentration and here, methanol remains within 120 % of the pri

mary value after exposure to (4.55.5) 107 molec cm3 h

OH (Table 1), which is expected based on the reaction with OH (Overend and Paraskevopoulos, 1978) and the low terpene concentrations. Monoterpene concentrations are below the detection limit in all experiments and isoprene emissions are relatively low (Table 2).

www.atmos-chem-phys.net/17/705/2017/ Atmos. Chem. Phys., 17, 705720, 2017

716 E. A. Bruns et al.: Fresh and aged residential wood combustion emissions

We have previously identied the compounds contributing to the majority of the SOA formed during these experiments (Bruns et al., 2016). The average EF for each of these species is shown in Fig. 3. Figure S3 shows the observed decay of the SOA precursors contributing the most to SOA formation during aging in the chamber, compared to the expected decay based on the OH concentration in the chamber and the reaction rate with respect to OH. There is generally good agreement between the observed and calculated decay for each compound which supports the structural assignment of each ion. For 2-methoxyphenol and 2,6-dimethoxyphenol (Fig. S3f and i, respectively), the agreement between the ob-served and calculated decays is not as good as for the other compounds, with slower decays than predicted. This discrepancy may be due to fragmentation of related compounds to form 2-methoxyphenol and 2,6-dimethoxyphenol in the instrument or formation of these compounds in the chamber during oxidation. For o-benzenediol, the decays are initially faster than expected and then become slower with increased aging, possibly due to the presence of isomers with different reaction rates with respect to OH.

3.5 Aged emission variability

As described above, the primary emission proles, as well as total NMOG mass emitted, vary considerably for experiments 2 and 3 compared to experiments 1, 4 and 5, with much higher total NMOG emissions in experiments 2 and3. It is expected that the aged emission proles also exhibit variability based on the primary emissions. Total acid and O-containing species decrease with aging in experiments 2 and 3, in contrast to experiments 1, 4 and 5, where these classes increase with aging (Fig. 4). Formic acid shows the largest increase with aging in all experiments ( 190480 mg kg1

relative to the primary EF, Fig. 5), however, in experiments 1, 4 and 5, this increase contributes much more to the total acid mass as the total acid mass is 515 times lower com

pared to experiments 2 and 3. An analogous case occurs for maleic anhydride for the O-containing class of compounds.As formic acid and maleic anhydride are formed from the oxidation of aromatic compounds (Bandow et al., 1985; Sato et al., 2007; Praplan et al., 2014), among others, a higher fraction of aromatic species to the total NMOG emissions will contribute to increases in acid and O-containing NMOGs.Inclusion of NMOGs not quantied by PTR-ToF-MS could impact the trends observed in Fig. 4.

To determine the impact of the high NMOG emission experiments (2 and 3) compared to the lower NMOG emission experiments (1, 4 and 5) on SOA formation potential, individual SOA precursors with published SOA yields are investigated. The SOA formation potential for each of these 18 compounds is determined as the product of the primary EF and the best-estimate SOA yield determined from the literature, as determined previously (Bruns et al., 2016). The total SOA formation potential for each experiment is taken

as the sum of the individual SOA formation potentials. Interestingly, the SOA formation potential is similar in all experiments and the average enhancement of SOA formation potential in experiments 2 and 3 compared to the average of experiments 1, 4 and 5 is insignicant (Fig. 2), despite the considerably different total NMOG EFs.

4 Conclusions

This study is the rst detailed characterization of primary NMOGs from residential wood combustion using a PTRToF-MS and the rst investigation of the evolution of the majority of these NMOGs with aging. Differences in EFs and proles between residential burning and open burning can be considerable and these results illustrate the importance of considering these emission sources individually. While total emissions from open burning are much larger than from residential burning, the societal relevance of residential wood burning emissions is nontrivial. A large fraction of open biomass burning derives from wildres in sparsely populated regions (Ito and Penner, 2004), whereas residential wood combustion has been shown to be a major fraction of wintertime submicron organic aerosol in densely populated communities (Glasius et al., 2006; Krecl et al., 2008; Gonalves et al., 2012; Guofeng et al., 2012; Crippa et al., 2013; Herich et al., 2014; Tao et al., 2014; Paraskevopoulou et al., 2015). Interestingly, MCE does not completely capture inter-burn variability, which is driven by differences in oxygenated content. This work clearly shows that measurements of total NMOGs or total hydrocarbon measurements are insufcient for estimating SOA formation potential from residential wood combustion. While this work characterizes the stable burning of beech wood in a modern woodstove, the composition and quantities of wood combustion emissions are highly dependent on many factors, and further work is needed to characterize the emissions and the evolution of these emissions with aging generated from burning of different wood types and under different burn parameters.

5 Data availability

The datasets are available upon request to the corresponding authors.

The Supplement related to this article is available online at http://dx.doi.org/10.5194/acp-17-705-2017-supplement

Web End =doi:10.5194/acp-17-705-2017-supplement .

Acknowledgement. The research leading to these results received funding from the European Communitys Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 290605 (PSI-FELLOW), from the Competence Center Environment and

Atmos. Chem. Phys., 17, 705720, 2017 www.atmos-chem-phys.net/17/705/2017/

E. A. Bruns et al.: Fresh and aged residential wood combustion emissions 717

Sustainability (CCES) (project OPTIWARES) and from the Swiss National Science Foundation (WOOSHI grant 140590 and starting grant BSSGI0_155846). We are grateful to Ren Richter for technical assistance and to Mike Cubison for analysis support.

Edited by: E. BrowneReviewed by: two anonymous referees

References

Aiken, A. C., de Foy, B., Wiedinmyer, C., DeCarlo, P. F., Ulbrich, I.M., Wehrli, M. N., Szidat, S., Prevot, A. S. H., Noda, J., Wacker,L., Volkamer, R., Fortner, E., Wang, J., Laskin, A., Shutthanandan, V., Zheng, J., Zhang, R., Paredes-Miranda, G., Arnott, W.P., Molina, L. T., Sosa, G., Querol, X., and Jimenez, J. L.: Mexico city aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) Part 2: Analysis of the biomass burning contribution and the non-fossil carbon fraction, Atmos. Chem. Phys., 10, 53155341, doi:http://dx.doi.org/10.5194/acp-10-5315-2010

Web End =10.5194/acp-10-5315-2010 http://dx.doi.org/10.5194/acp-10-5315-2010

Web End = , 2010.

Akagi, S. K., Yokelson, R. J., Burling, I. R., Meinardi, S., Simpson, I., Blake, D. R., McMeeking, G. R., Sullivan, A., Lee, T., Kreidenweis, S., Urbanski, S., Reardon, J., Grifth, D. W. T., Johnson, T. J., and Weise, D. R.: Measurements of reactive trace gases and variable O3 formation rates in some South Carolina biomass burning plumes, Atmos. Chem. Phys., 13, 11411165, doi:http://dx.doi.org/10.5194/acp-13-1141-2013

Web End =10.5194/acp-13-1141-2013 http://dx.doi.org/10.5194/acp-13-1141-2013

Web End = , 2013.

Andreae, M. O. and Merlet, P.: Emission of trace gases and aerosols from biomass burning, Global Biogeochem. Cy. 15, 955966, 2001.

Baasandorj, M., Millet, D. B., Hu, L., Mitroo, D., and Williams,B. J.: Measuring acetic and formic acid by proton-transfer-reaction mass spectrometry: sensitivity, humidity dependence, and quantifying interferences, Atmos. Meas. Tech., 8, 1303 1321, doi:http://dx.doi.org/10.5194/amt-8-1303-2015

Web End =10.5194/amt-8-1303-2015 http://dx.doi.org/10.5194/amt-8-1303-2015

Web End = , 2015.

Bandow, H., Washida, N., and Akimoto, H.: Ring-cleavage reactions of aromatic hydrocarbons studied by FT-IR spectroscopy. I. Photooxidation of toluene and benzene in the NOx-Air System,B. Chem. Soc. Jpn., 58, 25312540, 1985.

Barmet, P., Dommen, J., DeCarlo, P. F., Tritscher, T., Praplan, A. P., Platt, S. M., Prvt, A. S. H., Donahue, N. M., and Baltensperger,U.: OH clock determination by proton transfer reaction mass spectrometry at an environmental chamber, Atmos. Meas. Tech., 5, 647656, doi:http://dx.doi.org/10.5194/amt-5-647-2012

Web End =10.5194/amt-5-647-2012 http://dx.doi.org/10.5194/amt-5-647-2012

Web End = , 2012.

Bian, Q., May, A. A., Kreidenweis, S. M., and Pierce, J. R.: Investigation of particle and vapor wall-loss effects on controlled wood-smoke smog-chamber experiments, Atmos. Chem. Phys., 15, 1102711045, doi:http://dx.doi.org/10.5194/acp-15-11027-2015

Web End =10.5194/acp-15-11027-2015 http://dx.doi.org/10.5194/acp-15-11027-2015

Web End = , 2015. Blling, A. K., Pagels, J., Yttri, K. E., Barregard, L., Sallsten, G.,

Schwarze, P. E., and Boman, C.: Health effects of residential wood smoke particles: the importance of combustion conditions and physicochemical particle properties, Part. Fibre Toxicol., 6, doi:http://dx.doi.org/10.1186/1743-8977-6-29

Web End =10.1186/1743-8977-6-29 http://dx.doi.org/10.1186/1743-8977-6-29

Web End = , 2009.

Bruns, E. A., Krapf, M., Orasche, J., Huang, Y., Zimmermann, R., Drinovec, L., Mocnik, G., El-Haddad, I., Slowik, J. G., Dommen,J., Baltensperger, U., and Prvt, A. S. H.: Characterization of primary and secondary wood combustion products generated un-

der different burner loads, Atmos. Chem. Phys., 15, 28252841, doi:http://dx.doi.org/10.5194/acp-15-2825-2015

Web End =10.5194/acp-15-2825-2015 http://dx.doi.org/10.5194/acp-15-2825-2015

Web End = , 2015a.

Bruns, E. A., El Haddad, I., Keller, A., Klein, F., Kumar, N. K., Pieber, S. M., Corbin, J. C., Slowik, J. G., Brune, W. H., Baltensperger, U., and Prvt, A. S. H.: Inter-comparison of laboratory smog chamber and ow reactor systems on organic aerosol yield and composition, Atmos. Meas. Tech., 8, 2315 2332, doi:http://dx.doi.org/10.5194/amt-8-2315-2015

Web End =10.5194/amt-8-2315-2015 http://dx.doi.org/10.5194/amt-8-2315-2015

Web End = , 2015. 2015b.

Bruns, E. A., El Haddad, I., Slowik, J. G., Kilic, D., Klein, F., Baltensperger, U., and Prvt, A. S. H.: Identication of signicant precursor gases of secondary organic aerosols from residential wood combustion, Sci. Rep., 6, 27881, doi:http://dx.doi.org/10.1038/srep27881

Web End =10.1038/srep27881 http://dx.doi.org/10.1038/srep27881

Web End = , 2016.

Buhr, K., van Ruth, S., and Delahunty, C.: Analysis of volatile avour compounds by Proton Transfer Reaction-Mass Spectrometry: fragmentation patterns and discrimination between isobaric and isomeric compounds, Int. J. Mass. Spectrom., 221, 17, 2002.

Cappellin, L., Karl, T., Probst, M., Ismailova, O., Winkler, P. M., Soukoulis, C., Aprea, E., Mrk, T. D., Gasperi, F., and Biasioli,F.: On quantitative determination of volatile organic compound concentrations using proton transfer reaction time-of-ight mass spectrometry, Environ. Sci. Technol., 46, 22832290, 2012.Chan, A. W. H., Kautzman, K. E., Chhabra, P. S., Surratt, J. D.,

Chan, M. N., Crounse, J. D., Krten, A., Wennberg, P. O., Flagan, R. C., and Seinfeld, J. H.: Secondary organic aerosol formation from photooxidation of naphthalene and alkylnaphthalenes: implications for oxidation of intermediate volatility organic compounds (IVOCs), Atmos. Chem. Phys., 9, 30493060, doi:http://dx.doi.org/10.5194/acp-9-3049-2009

Web End =10.5194/acp-9-3049-2009 http://dx.doi.org/10.5194/acp-9-3049-2009

Web End = , 2009.

Chebbi, A. and Carlier, P.: Carboxylic acids in the troposphere, occurrence, sources, and sinks: A review, Atmos. Environ., 30, 42334249, 1996.

Christian, T. J., Kleiss, B., Yokelson, R. J., Holzinger, R., Crutzen,P. J., Hao, W. M., Saharjo, B. H., and Ward, D. E.: Comprehensive laboratory measurements of biomass-burning emissions: 1.Emissions from Indonesian, African, and other fuels, J. Geophys.Res.-Atmos., 108, 4719, doi:http://dx.doi.org/10.1029/2003JD003704

Web End =10.1029/2003JD003704 http://dx.doi.org/10.1029/2003JD003704

Web End = , 2003.Christian, T. J., Kleiss, B., Yokelson, R. J., Holzinger, R., Crutzen,P. J., Hao, W. M., Shirai, T., and Blake, D. R.: Comprehensive laboratory measurements of biomass-burning emissions: 2. First intercomparison of open-path FTIR, PTR-MS, and GC-MS/FID/ECD, J. Geophys. Res.-Atmos., 109, D02311, doi:http://dx.doi.org/10.1029/2003JD003874

Web End =10.1029/2003JD003874 http://dx.doi.org/10.1029/2003JD003874

Web End = , 2004.

Coggon, M. M., Veres, P. R., Yuan, B., Koss, A., Warneke, C., Gilman, J. B., Lerner, B. M., Peischl, J., Aikin, K. C., Stock-well, C. E., Hatch, L. E., Ryerson, T. B., Roberts, J. M., Yokelson, R. J., and de Gouw, J. A.: Emissions of nitrogen-containing organic compounds from the burning of herbaceous and arboraceous biomass: Fuel composition dependence and the variability of commonly used nitrile tracers, Geophys. Res. Lett., 43, 9903 9912, 2016.

Crippa, M., DeCarlo, P. F., Slowik, J. G., Mohr, C., Heringa, M.F., Chirico, R., Poulain, L., Freutel, F., Sciare, J., Cozic, J., Di Marco, C. F., Elsasser, M., Nicolas, J. B., Marchand, N., Abidi,E., Wiedensohler, A., Drewnick, F., Schneider, J., Borrmann,S., Nemitz, E., Zimmermann, R., Jaffrezo, J.-L., Prvt, A. S.H., and Baltensperger, U.: Wintertime aerosol chemical composition and source apportionment of the organic fraction in the

www.atmos-chem-phys.net/17/705/2017/ Atmos. Chem. Phys., 17, 705720, 2017

718 E. A. Bruns et al.: Fresh and aged residential wood combustion emissions

metropolitan area of Paris, Atmos. Chem. Phys., 13, 961981, doi:http://dx.doi.org/10.5194/acp-13-961-2013

Web End =10.5194/acp-13-961-2013 http://dx.doi.org/10.5194/acp-13-961-2013

Web End = , 2013.de Gouw, J. A., Warneke, C., Parrish, D. D., Holloway, J. S., Trainer,M., and Fehsenfeld, F. C.: Emission sources and ocean uptake of acetonitrile (CH3CN) in the atmosphere, J. Geophys. Res.-

Atmos., 108, 4329, doi:http://dx.doi.org/10.1029/2002JD002897

Web End =10.1029/2002JD002897 http://dx.doi.org/10.1029/2002JD002897

Web End = , 2003.de Gouw, J. A., Warneke, C., Stohl, A., Wollny, A. G., Brock,C. A., Cooper, O. R., Holloway, J. S., Trainer, M., Fehsenfeld,F. C., Atlas, E. L., Donnelly, S. G., Stroud, V., and Lueb, A.: Volatile organic compounds composition of merged and aged forest re plumes from Alaska and western Canada, J. Geophys.Res.-Atmos., 111, D10303, doi:http://dx.doi.org/10.1029/2005JD006175

Web End =10.1029/2005JD006175 http://dx.doi.org/10.1029/2005JD006175

Web End = , 2006. de Gouw, J. A., Welsh-Bon, D., Warneke, C., Kuster, W. C., Alexander, L., Baker, A. K., Beyersdorf, A. J., Blake, D. R., Canagaratna, M., Celada, A. T., Huey, L. G., Junkermann, W., Onasch,T. B., Salcido, A., Sjostedt, S. J., Sullivan, A. P., Tanner, D. J., Vargas, O., Weber, R. J., Worsnop, D. R., Yu, X. Y., and Zaveri, R.: Emission and chemistry of organic carbon in the gas and aerosol phase at a sub-urban site near Mexico City in March 2006 during the MILAGRO study, Atmos. Chem. Phys., 9, 3425 3442, doi:http://dx.doi.org/10.5194/acp-9-3425-2009

Web End =10.5194/acp-9-3425-2009 http://dx.doi.org/10.5194/acp-9-3425-2009

Web End = , 2009.

Dunne, E., Galbally, I. E., Lawson, S., and Patti, A.: Interference in the PTR-MS measurement of acetonitrile at m/z 42 in polluted urban air A study using switchable reagent ion PTR-MS, Int. J.Mass. Spectrom. 319320, 4047, 2012.

Evtyugina, M., Alves, C., Calvo, A., Nunes, T., Tarelho, L., Duarte,M., Prozil, S. O., Evtuguin, D. V., and Pio, C.: VOC emissions from residential combustion of Southern and mid-European woods, Atmos. Environ. 83, 9098, 2014.

Fu, P. P., Xia, Q., Sun, X., and Yu, H.: Phototoxicity and environmental transformation of polycyclic aromatic hydrocarbons (PAHs) light-induced reactive oxygen species, lipid peroxidation, and DNA damage, J. Environ. Sci. Heal. C, 30, 141, 2012.Gaeggeler, K., Prevot, A. S. H., Dommen, J., Legreid, G., Reimann,S., and Baltensperger, U.: Residential wood burning in an Alpine valley as a source for oxygenated volatile organic compounds, hydrocarbons and organic acids, Atmos. Environ., 42, 8278 8287, 2008.

Gilman, J. B., Lerner, B. M., Kuster, W. C., Goldan, P. D., Warneke,C., Veres, P. R., Roberts, J. M., de Gouw, J. A., Burling, I. R., and Yokelson, R. J.: Biomass burning emissions and potential air quality impacts of volatile organic compounds and other trace gases from fuels common in the US, Atmos. Chem. Phys., 15, 1391513938, doi:http://dx.doi.org/10.5194/acp-15-13915-2015

Web End =10.5194/acp-15-13915-2015 http://dx.doi.org/10.5194/acp-15-13915-2015

Web End = , 2015.

Glasius, M., Ketzel, M., Whlin, P., Jensen, B., Mnster, J., Berkowicz, R., and Palmgren, F.: Impact of wood combustion on particle levels in a residential area in Denmark, Atmos. Environ., 40, 71157124, 2006.

Gmez Alvarez, E., Borrs, E., Viidanoja, J., and Hjorth, J.: Unsatu-rated dicarbonyl products from the OH-initiated photo-oxidation of furan, 2-methylfuran and 3-methylfuran, Atmos. Environ., 43, 16031612, 2009.

Gonalves, C., Alves, C., and Pio, C.: Inventory of ne particulate organic compound emissions from residential wood combustion in Portugal, Atmos. Environ., 50, 297306, 2012.

Goode, J. G., Yokelson, R. J., Ward, D. E., Susott, R. A., Babbitt, R. E., Davies, M. A., and Hao, W. M.: Measurements of excess O3, CO2, CO, CH4, C2H4, C2H2, HCN, NO, NH3,

HCOOH, CH3COOH, HCHO, and CH3OH in 1997 Alaskan

biomass burning plumes by airborne Fourier transform infrared spectroscopy (AFTIR), J. Geophys. Res.-Atmos., 105, 22147 22166, 2000.

Grieshop, A. P., Logue, J. M., Donahue, N. M., and Robinson, A.L.: Laboratory investigation of photochemical oxidation of organic aerosol from wood res 1: measurement and simulation of organic aerosol evolution, Atmos. Chem. Phys., 9, 12631277, doi:http://dx.doi.org/10.5194/acp-9-1263-2009

Web End =10.5194/acp-9-1263-2009 http://dx.doi.org/10.5194/acp-9-1263-2009

Web End = , 2009a.

Grieshop, A. P., Donahue, N. M., and Robinson, A. L.: Laboratory investigation of photochemical oxidation of organic aerosol from wood res 2: analysis of aerosol mass spectrometer data, Atmos. Chem. Phys., 9, 22272240, doi:http://dx.doi.org/10.5194/acp-9-2227-2009

Web End =10.5194/acp-9-2227-2009 http://dx.doi.org/10.5194/acp-9-2227-2009

Web End = , 2009b.

Guofeng, S., Siye, W., Wen, W., Yanyan, Z., Yujia, M., Bin, W., Rong, W., Wei, L., Huizhong, S., Ye, H., Yifeng, Y., Wei, W., Xilong, W., Xuejun, W. and Shu, T.: Emission factors, size distributions, and emission inventories of carbonaceous particulate matter from residential wood combustion in rural China, Environ. Sci. Technol., 46, 42074214, 2012.

Hansson, K.-M., Samuelsson, J., Tullin, C., and mand, L.-E.: Formation of HNCO, HCN, and NH3 from the pyrolysis of bark and nitrogen-containing model compounds, Combust. Flame, 137, 265277, 2004.

Hedberg, E., Kristensson, A., Ohlsson, M., Johansson, C., Johansson, P.-., Swietlicki, E., Vesely, V., Wideqvist, U., and Wester-holm, R.: Chemical and physical characterization of emissions from birch wood combustion in a wood stove, Atmos. Environ., 36, 48234837, 2002.

Hennigan, C. J., Sullivan, A. P., Collett, J. L., and Robinson,A. L.: Levoglucosan stability in biomass burning particles exposed to hydroxyl radicals, Geophys. Res. Lett., 37, L09806, doi:http://dx.doi.org/10.1029/2010GL043088

Web End =10.1029/2010GL043088 http://dx.doi.org/10.1029/2010GL043088

Web End = , 2010.

Herich, H., Gianini, M. F. D., Piot, C., Monik, G., Jaffrezo, J. L., Besombes, J. L., Prvt, A. S. H., and Hueglin, C.: Overview of the impact of wood burning emissions on carbonaceous aerosols and PM in large parts of the Alpine region, Atmos. Environ., 89, 6475, 2014.

Heringa, M. F., DeCarlo, P. F., Chirico, R., Tritscher, T., Dommen,J., Weingartner, E., Richter, R., Wehrle, G., Prvt, A. S. H., and Baltensperger, U.: Investigations of primary and secondary particulate matter of different wood combustion appliances with a high-resolution time-of-ight aerosol mass spectrometer, Atmos. Chem. Phys., 11, 59455957, doi:http://dx.doi.org/10.5194/acp-11-5945-2011

Web End =10.5194/acp-11-5945- http://dx.doi.org/10.5194/acp-11-5945-2011

Web End =2011 , 2011.

Hobbs, P. V., Sinha, P., Yokelson, R. J., Christian, T. J., Blake, D. R., Gao, S., Kirchstetter, T. W., Novakov, T., and Pilewskie, P.: Evolution of gases and particles from a savanna re in South Africa, J. Geophys. Res.-Atmos., 108, 8485, doi:http://dx.doi.org/10.1029/2002JD002352

Web End =10.1029/2002JD002352 http://dx.doi.org/10.1029/2002JD002352

Web End = , 2003.

Holzinger, R., Warneke, C., Hansel, A., Jordan, A., Lindinger, W., Scharffe, D.H., Schade, G., and Crutzen, P. J.: Biomass burning as a source of formaldehyde, acetaldehyde, methanol, acetone, acetonitrile, and hydrogen cyanide, Geophys. Res. Lett., 26, 11611164, 1999.

Holzinger, R., Williams, J., Salisbury, G., Klpfel, T., de Reus,M., Traub, M., Crutzen, P. J., and Lelieveld, J.: Oxygenated compounds in aged biomass burning plumes over the Eastern Mediterranean: evidence for strong secondary production

Atmos. Chem. Phys., 17, 705720, 2017 www.atmos-chem-phys.net/17/705/2017/

plume, Atmos. Chem. Phys., 16, 38133824, doi:http://dx.doi.org/10.5194/acp-16-3813-2016

Web End =10.5194/acp- http://dx.doi.org/10.5194/acp-16-3813-2016

Web End =16-3813-2016 , 2016.

Nozire, B., Kalberer, M., Claeys, M., Allan, J., DAnna, B., Decesari, S., Finessi, E., Glasius, M., Grgi, I., Hamilton, J.F., Hoffmann, T., Iinuma, Y., Jaoui, M., Kahnt, A., Kampf, C.J., Kourtchev, I., Maenhaut, W., Marsden, N., Saarikoski, S., Schnelle-Kreis, J., Surratt, J. D., Szidat, S., Szmigielski, R., and Wisthaler, A.: The molecular identication of organic compounds in the atmosphere: state of the art and challenges, Chem.Rev., 115, 39193983, 2015.

Overend, R. and Paraskevopoulos, G.: Rates of hydroxyl radical reactions, 4. Reactions with methanol, ethanol, 1-propanol, and 2-propanol at 296 K, J. Phys. Chem., 82, 13291333, 1978.

Ozil, F., Tschamber, V., Haas, F., and Trouv, G.: Efciency of catalytic processes for the reduction of CO and VOC emissions from wood combustion in domestic replaces, Fuel Process. Technol., 90, 10531061, 2009.

Paraskevopoulou, D., Liakakou, E., Gerasopoulos, E., and Mihalopoulos, N.: Sources of atmospheric aerosol from long-term measurements (5 years) of chemical composition in Athens, Greece, Sci. Total Environ., 527528, 165178, 2015.

Paulot, F., Wunch, D., Crounse, J. D., Toon, G. C., Millet, D.B., DeCarlo, P. F., Vigouroux, C., Deutscher, N. M., Gonzlez Abad, G., Notholt, J., Warneke, T., Hannigan, J. W., Warneke,C., de Gouw, J. A., Dunlea, E. J., De Mazire, M., Grifth, D.W. T., Bernath, P., Jimenez, J. L., and Wennberg, P. O.: Importance of secondary sources in the atmospheric budgets of formic and acetic acids, Atmos. Chem. Phys., 11, 19892013, doi:http://dx.doi.org/10.5194/acp-11-1989-2011

Web End =10.5194/acp-11-1989-2011 http://dx.doi.org/10.5194/acp-11-1989-2011

Web End = , 2011.

Pettersson, E., Boman, C., Westerholm, R., Bostrm, D., and Nordin, A.: Stove performance and emission characteristics in residential wood log and pellet combustion, part 2: wood stove, Energ. Fuel, 25, 315323, 2011.

Platt, S. M., El Haddad, I., Zardini, A. A., Clairotte, M., Astorga,C., Wolf, R., Slowik, J. G., Temime-Roussel, B., Marchand,N., Jeek, I., Drinovec, L., Mocnik, G., Mhler, O., Richter,R., Barmet, P., Bianchi, F., Baltensperger, U., and Prvt, A.S. H.: Secondary organic aerosol formation from gasoline vehicle emissions in a new mobile environmental reaction chamber, Atmos. Chem. Phys., 13, 91419158, doi:http://dx.doi.org/10.5194/acp-13-9141-2013

Web End =10.5194/acp-13-9141- http://dx.doi.org/10.5194/acp-13-9141-2013

Web End =2013 , 2013.

Pouli, A. E., Hatzinikolaou, D. G., Piperi, C., Stavridou, A., Psallidopoulos, M. C., and Stavrides, J. C.: The cytotoxic effect of volatile organic compounds of the gas phase of cigarette smoke on lung epithelial cells, Free Radical Bio. Med., 34, 345355, 2003.

Praplan, A. P., Hegyi-Gaeggeler, K., Barmet, P., Pfaffenberger, L., Dommen, J., and Baltensperger, U.: Online measurements of water-soluble organic acids in the gas and aerosol phase from the photooxidation of 1,3,5-trimethylbenzene, Atmos. Chem. Phys., 14, 86658677, doi:http://dx.doi.org/10.5194/acp-14-8665-2014

Web End =10.5194/acp-14-8665-2014 http://dx.doi.org/10.5194/acp-14-8665-2014

Web End = , 2014.

Reda, A. A., Czech, H., Schnelle-Kreis, J., Sippula, O., Orasche, J., Weggler, B., Abbaszade, G., Arteaga-Salas, J. M., Kortelainen,M., Tissari, J., Jokiniemi, J., Streibel, T., and Zimmermann, R.: Analysis of gas-phase carbonyl compounds in emissions from modern wood combustion appliances: inuence of wood type and combustion appliance, Energ. Fuel, 29, 38973907, 2015.Sato, K., Hatakeyama, S., and Imamura, T.: Secondary organic aerosol formation during the photooxidation of toluene: NOx

www.atmos-chem-phys.net/17/705/2017/ Atmos. Chem. Phys., 17, 705720, 2017

E. A. Bruns et al.: Fresh and aged residential wood combustion emissions 719

of methanol and acetone, Atmos. Chem. Phys., 5, 3946, doi:http://dx.doi.org/10.5194/acp-5-39-2005

Web End =10.5194/acp-5-39-2005 http://dx.doi.org/10.5194/acp-5-39-2005

Web End = , 2005.

IPCC: Climate Change 2013: The Physical Science Basis, Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Stocker,T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S. K., Boschung,J., Nauels, A., Xia, Y., Bex, V., and Midgley, P. M., Cambridge University Press, Cambridge, UK and New York, USA, 2013.Ito, A. and Penner, J. E.: Global estimates of biomass burning emissions based on satellite imagery for the year 2000, J. Geophys.Res.-Atmos., 109, D14S05, doi:http://dx.doi.org/10.1029/2003JD004423

Web End =10.1029/2003JD004423 http://dx.doi.org/10.1029/2003JD004423

Web End = , 2004.Jordan, A., Haidacher, S., Hanel, G., Hartungen, E., Mrk, L., See-hauser, H., Schottkowsky, R., Sulzer, P., and Mrk, T. D.: A high resolution and high sensitivity proton-transfer-reaction time-ofight mass spectrometer (PTR-TOF-MS), Int. J. Mass. Spec-trom., 286, 122128, 2009.

Jordan, T. B. and Seen, A. J.: Effect of airow setting on the organic composition of woodheater emissions, Environ. Sci. Technol., 39, 36013610, 2005.

Jost, C., Trentmann, J., Sprung, D., Andreae, M. O., McQuaid, J.B., and Barjat, H.: Trace gas chemistry in a young biomass burning plume over Namibia: Observations and model simulations, J.Geophys. Res.-Atmos., 108, 8482, doi:http://dx.doi.org/10.1029/2002JD002431

Web End =10.1029/2002JD002431 http://dx.doi.org/10.1029/2002JD002431

Web End = , 2003.

Kistler, M., Schmidl, C., Padouvas, E., Giebl, H., Lohninger, J., Ellinger, R., Bauer, H., and Puxbaum, H.: Odor, gaseous and PM10 emissions from small scale combustion of wood types indigenous to Central Europe, Atmos. Environ., 51, 8693, 2012.

Krecl, P., Hedberg Larsson, E., Strm, J., and Johansson, C.: Contribution of residential wood combustion and other sources to hourly winter aerosol in Northern Sweden determined by positive matrix factorization, Atmos. Chem. Phys., 8, 36393653, doi:http://dx.doi.org/10.5194/acp-8-3639-2008

Web End =10.5194/acp-8-3639-2008 http://dx.doi.org/10.5194/acp-8-3639-2008

Web End = , 2008.

Kroll, J. H. and Seinfeld, J. H.: Chemistry of secondary organic aerosol: formation and evolution of low-volatility organics in the atmosphere, Atmos. Environ., 42, 35933624, 2008.

Lindinger, W., Hansel, A., and Jordan, A.: On-line monitoring of volatile organic compounds at pptv levels by means of proton-transfer-reaction mass spectrometry (PTR-MS) medical applications, food control and environmental research, Int. J. Mass.Spectrom., 173, 191241, 1998.

Mason, S. A., Field, R. J., Yokelson, R. J., Kochivar, M. A., Tinsley,M. R., Ward, D. E., and Hao, W. M.: Complex effects arising in smoke plume simulations due to inclusion of direct emissions of oxygenated organic species from biomass combustion, J. Geophys. Res.-Atmos., 106, 1252712539, 2001.

McDonald, J. D., Zielinska, B., Fujita, E. M., Sagebiel, J. C., Chow,J. C., and Watson, J. G.: Fine particle and gaseous emission rates from residential wood combustion, Environ. Sci. Technol., 34, 20802091, 2000.

Midey, A. J., Williams, S., Miller, T. M., and Viggiano, A. A.: Reactions of O+

2 , NO+ and H3O+ with methylcyclohexane (C7H14[notdef] and cyclooctane (C8H16[notdef] from 298 to 700 K, Int. J. Mass. Spec-trom., 222, 413430, 2003.

Mller, M., Anderson, B. E., Beyersdorf, A. J., Crawford, J. H., Diskin, G. S., Eichler, P., Fried, A., Keutsch, F. N., Mikoviny,T., Thornhill, K. L., Walega, J. G., Weinheimer, A. J., Yang,M., Yokelson, R. J., and Wisthaler, A.: In situ measurements and modeling of reactive trace gases in a small biomass burning

720 E. A. Bruns et al.: Fresh and aged residential wood combustion emissions

dependence of chemical composition, J. Phys. Chem. A, 111, 97969808, 2007.

Schauer, J. J., Kleeman, M. J., Cass, G. R., and Simoneit, B. R. T.: Measurement of emissions from air pollution sources, 3. C1-C29 organic compounds from replace combustion of wood, Environ.

Sci. Technol., 35, 17161728, 2001.

Schmidl, C., Luisser, M., Padouvas, E., Lasselsberger, L., Rzaca,M., Ramirez-Santa Cruz, C., Handler, M., Peng, G., Bauer, H., and Puxbaum, H.: Particulate and gaseous emissions from manually and automatically red small scale combustion systems, Atmos. Environ., 45, 74437454, 2011.

Shao, M., Lu, S., Liu, Y., Xie, X., Chang, C., Huang, S., and Chen,Z.: Volatile organic compounds measured in summer in Beijing and their role in ground-level ozone formation, J. Geophys. Res.-Atmos., 114, D00G06, doi:http://dx.doi.org/10.1029/2008JD010863

Web End =10.1029/2008JD010863 http://dx.doi.org/10.1029/2008JD010863

Web End = , 2009.Singh, H. B., Salas, L., Herlth, D., Kolyer, R., Czech, E., Viezee,W., Li, Q., Jacob, D. J., Blake, D., Sachse, G., Harward, C.N., Fuelberg, H., Kiley, C. M., Zhao, Y., and Kondo, Y.: In situ measurements of HCN and CH3CN over the Pacic Ocean:

Sources, sinks, and budgets, J. Geophys. Res.-Atmos., 108, 8795, doi:http://dx.doi.org/10.1029/2002JD003006

Web End =10.1029/2002JD003006 http://dx.doi.org/10.1029/2002JD003006

Web End = , 2003.

Singh, H. B., Salas, L. J., Chateld, R. B., Czech, E., Fried,A., Walega, J., Evans, M. J., Field, B. D., Jacob, D. J., Blake, D., Heikes, B., Talbot, R., Sachse, G., Crawford, J. H., Avery, M. A., Sandholm, S., and Fuelberg, H.: Analysis of the atmospheric distribution, sources, and sinks of oxygenated volatile organic chemicals based on measurements over the Pacic during TRACE-P, J. Geophys. Res.-Atmos., 109, D15S07, doi:http://dx.doi.org/10.1029/2003JD003883

Web End =10.1029/2003JD003883 http://dx.doi.org/10.1029/2003JD003883

Web End = , 2004.

Stockwell, C. E., Veres, P. R., Williams, J., and Yokelson, R. J.:

Characterization of biomass burning emissions from cooking res, peat, crop residue, and other fuels with high-resolution proton-transfer-reaction time-of-ight mass spectrometry, Atmos. Chem. Phys., 15, 845865, doi:http://dx.doi.org/10.5194/acp-15-845-2015

Web End =10.5194/acp-15-845-2015 http://dx.doi.org/10.5194/acp-15-845-2015

Web End = , 2015.yc, M., Hork, J., Hopan, F., Krpec, K., Tomej, T., Ocelka, T., and

Pekrek, V.: Effect of fuels and domestic heating appliance types on emission factors of selected organic pollutants, Environ. Sci.Technol., 45, 94279434, 2011.

Tabazadeh, A., Yokelson, R. J., Singh, H. B., Hobbs, P. V., Crawford, J. H., and Iraci, L. T.: Heterogeneous chemistry involving methanol in tropospheric clouds, Geophys. Res. Lett., 31, L06114, doi:http://dx.doi.org/10.1029/2003GL018775

Web End =10.1029/2003GL018775 http://dx.doi.org/10.1029/2003GL018775

Web End = , 2004.

Tao, J., Gao, J., Zhang, L., Zhang, R., Che, H., Zhang, Z., Lin, Z., Jing, J., Cao, J., and Hsu, S.-C.: PM2.5 pollution in a megacity of southwest China: source apportionment and implication,

Atmos. Chem. Phys., 14, 86798699, doi:http://dx.doi.org/10.5194/acp-14-8679-2014

Web End =10.5194/acp-14-8679- http://dx.doi.org/10.5194/acp-14-8679-2014

Web End =2014 , 2014.

Warneke, C., de Gouw, J. A., Kuster, W. C., Goldan, P. D., and Fall, R.: Validation of atmospheric VOC measurements by proton-transfer-reaction mass spectrometry using a gaschromatographic preseparation method, Environ. Sci. Technol., 37, 24942501, 2003.

Warneke, C., de Gouw, J. A., Stohl, A., Cooper, O. R., Goldan, P.D., Kuster, W. C., Holloway, J. S., Williams, E. J., Lerner, B.M., McKeen, S. A., Trainer, M., Fehsenfeld, F. C., Atlas, E. L., Donnelly, S. G., Stroud, V., Lueb, A., and Kato, S.: Biomass burning and anthropogenic sources of CO over New England in the summer 2004, J. Geophys. Res.-Atmos., 111, D23S15, doi:http://dx.doi.org/10.1029/2005JD006878

Web End =10.1029/2005JD006878 http://dx.doi.org/10.1029/2005JD006878

Web End = , 2006.

Warneke, C., Roberts, J. M., Veres, P., Gilman, J., Kuster, W. C., Burling, I., Yokelson, R., and de Gouw, J. A.: VOC identication and inter-comparison from laboratory biomass burning using PTR-MS and PIT-MS, Int. J. Mass. Spectrom., 303, 614, 2011.

Yokelson, R. J., Bertschi, I. T., Christian, T. J., Hobbs, P. V., Ward,D. E., and Hao, W. M.: Trace gas measurements in nascent, aged, and cloud-processed smoke from African savanna res by airborne Fourier transform infrared spectroscopy (AFTIR), J. Geophys. Res.-Atmos., 108, 8478, doi:http://dx.doi.org/10.1029/2002JD002322

Web End =10.1029/2002JD002322 http://dx.doi.org/10.1029/2002JD002322

Web End = , 2003.

Yokelson, R. J., Christian, T. J., Karl, T. G., and Guenther, A.:

The tropical forest and re emissions experiment: laboratory re measurements and synthesis of campaign data, Atmos. Chem. Phys., 8, 35093527, doi:http://dx.doi.org/10.5194/acp-8-3509-2008

Web End =10.5194/acp-8-3509-2008 http://dx.doi.org/10.5194/acp-8-3509-2008

Web End = , 2008. Yokelson, R. J., Crounse, J. D., DeCarlo, P. F., Karl, T., Urbanski,S., Atlas, E., Campos, T., Shinozuka, Y., Kapustin, V., Clarke,A. D., Weinheimer, A., Knapp, D. J., Montzka, D. D., Holloway,J., Weibring, P., Flocke, F., Zheng, W., Toohey, D., Wennberg, P.O., Wiedinmyer, C., Mauldin, L., Fried, A., Richter, D., Walega,J., Jimenez, J. L., Adachi, K., Buseck, P. R., Hall, S. R., and Shetter, R.: Emissions from biomass burning in the Yucatan, Atmos. Chem. Phys., 9, 57855812, doi:http://dx.doi.org/10.5194/acp-9-5785-2009

Web End =10.5194/acp-9-5785-2009 http://dx.doi.org/10.5194/acp-9-5785-2009

Web End = , 2009.

Zhang, X., Cappa, C. D., Jathar, S. H., McVay, R. C., Ensberg, J. J., Kleeman, M. J., and Seinfeld, J. H.: Inuence of vapor wall loss in laboratory chambers on yields of secondary organic aerosol, P. Natl. Acad. Sci. USA, 111, 58025807, 2014.

Atmos. Chem. Phys., 17, 705720, 2017 www.atmos-chem-phys.net/17/705/2017/