Sources of Fine Organic Aerosol. 9. Pine, Oak, and Synthetic Log Combustion in Residential Fireplaces

Sources of Fine Organic Aerosol. 9.Pine, Oak, and Synthetic LogCombustion in ResidentialFireplacesW O L F G A N G F . R O G G E , †

L Y N N M . H I L D E M A N N , ‡

M O N I C A A . M A Z U R E K , § A N DG L E N R . C A S S *

Environmental Engineering Science Department,California Institute of Technology, Pasadena, California 91125

B E R N D R . T . S I M O N E I T

Petroleum and Environmental Geochemistry Group,College of Oceanic and Atmospheric Sciences,Oregon State University, Corvallis, Oregon 97331

Combustion of wood in residential fireplaces contributesapproximately 14% on an annual average of the totalprimary fine particle organic carbon (OC) emissions to theLos Angeles urban atmosphere and up to 30% of the fineparticulate OC emissions on winter days. This paper presentscomprehensive organic compound source profiles forsmoke from burning pine, oak, and synthetic logs in residentialfireplaces. Mass emission rates are determined for ap-proximately 200 organic compounds including suites ofthe n-alkanes, n-alkenes, cyclohexylalkanes, n-alkanals, n-alkanoic acids, alkenoic acids, dicarboxylic acids, resinacids, hydroxylated/methyoxylated phenols, lignans, substi-tuted benzenes/benzaldehydes, phytosterols, polycyclicaromatic hydrocarbons (PAHs), and oxy-PAHs. Wood smokeconstituents reflect to a great extent the underlyingcomposition of the wood burned: pine and oak logs producesmoke that is enriched in lignin decomposition products,pine smoke is enriched in resin acids and their thermalalteration products, while smoke from the synthetic log burnedhere bears the major signature of the petroleum productscombined with traces of the sawdust components fromwhich it is made. Resin acids are discussed as potentialwood smoke tracers in the environment, and it is shownthat the time series of resin acids concentrations in theLos Angeles atmosphere follows the extreme seasonal varia-tion in wood use reported in previous emissions inventoriesfor the Los Angeles urban area.

IntroductionWood is burned for space heating in residential homes inmany urbanized and rural areas of the colder northeastern,northwestern, and north central areas of the United States

(1). In contrast, in southern California wood is burned mainlyin open fireplaces, largely to enhance the residential ambi-ance and to mark special holiday gatherings at Thanksgiving,Christmas, and New Year’s Eve. Gray (2) surveyed woodcombustion within an 80 × 80 km area centered overdowntown Los Angeles. He estimated that there were 3.4million residential homes within that study area in 1980,with about 720 000 open fireplaces, and that about 190 000ton of softwood and 120 000 ton of hardwood were burnedin open fireplaces within that study area in 1982 (2).

Wood combustion has been identified in earlier studiesas a non-fossil fuel source (biofuel) that can contributeappreciably to the deterioration of both outdoor and indoorair quality (3-8). Fireplace burning of wood in the Denverarea during wintertime accounts for 20-30% of the total fineparticulate matter released directly from sources in that city(9). Emission inventory estimates show that more than 4000kg day-1 on average of fine particulate organic matter (particlediameter e2.1 µm) is released to the atmosphere of an 80 km×80 km study area centered over Los Angeles from residentialwood burning over the year, with greater than 10 000 kgemitted during a typical winter day (2, 10). Wood smokeaccounts for 14% on average of the airborne primary fineparticulate organic matter emitted from all primary particlesources in that Los Angeles urban study area throughout theyear and close to 30% of such emissions during wintermonths.

Due to their mutagenic and carcinogenic potential,previous studies characterizing wood smoke emissions havefocused on the identification of PAH-type compounds inwood smoke (11-18). In the present work, we seek a morecomplete description of the organic compounds found inwood smoke emissions, with particular emphasis on thedetection of compounds that may serve as nearly uniquetracers for the presence of wood smoke in ambient aerosolsamples.

To determine the contribution of wood smoke aerosolsto ambient concentrations, several different organic tracercompounds have been proposed including resin acids, retene,and methoxylated phenols (17, 19-24). In addition to thepotential wood smoke tracer compounds already mentioned,lignans (dimers of substituted phenols) recently have beensuggested as wood smoke tracers that aid in distinguishingbetween coniferous versus deciduous wood fires (22).

This study provides the most extensive account to dateof the molecular composition of combustion aerosols frompine and oak wood as well as from synthetic logs. Massemission rates are measured for nearly 200 distinct organiccompounds. This detailed emissions characterization pro-vides organic chemical composition profiles for wood smokesources that can be used to compute wood smoke concen-trations in a complex multi-source urban atmosphere viareceptor modeling techniques (25).

Experimental MethodsThe wood combustion experiments reported here wereconducted in a single-family house using a traditionalundampered brick fireplace that is typical of those found insouthern California. Each wood type (seasoned pine andoak wood) or synthetic log (Pine Mountain brand, 5 lb) wasburned in separate combustion experiments, typically overthe course of about 3 h for each experiment. To start thefire, a few pieces of newspaper were used. Kindling wasexclusively made of the type of wood tested.

For pine and oak wood fires, wood logs having weightsfrom 1 to 6 kg were used. To mimic traditional undampered

* Author to whom correspondence should be addressed. Phone:818-395-6888; fax: 818-395-2940; e-mail: [email protected].

† Present address: Department of Civil and EnvironmentalEngineering, Florida International University, Miami, FL 33199.

‡ Present address: Department of Civil Engineering, StanfordUniversity, Stanford, CA 94305-4020.

§ Present address: Institute of Marine and Coastal Sciences,Rutgers Universty, New Brunswick, NJ 08903.

Environ. Sci. Technol. 1998, 32, 13-22

S0013-936X(96)00930-3 CCC: $14.00 1997 American Chemical Society VOL. 32, NO. 1, 1998 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 13Published on Web 01/01/1998

fires in residential fireplaces, wood logs were added to thefire at intervals, and the fire was periodically stirred (woodburned per test: 12.5-20 kg). In contrast, the synthetic logwas left burning undisturbed during testing in accordancewith the manufacturer’s guidelines. For a more detaileddescription of the source sampling procedure, see Hildemannet al. (10).

Smoke aerosols were withdrawn from the chimney at fourdifferent horizontal sampling points along the axis of thechimney and collected using the dilution sampling systemdescribed by Hildemann et al. (10, 26). Fine particulateemission rates ranged from 6.2 g/kg burned for the oak woodexperiment to 13.0 ( 4.0 g/kg burned for the two pine woodexperiments and 12.0 g/kg for the synthetic log experiment.

Total extracts and methylated extracts (diazomethane) offine organic particulate emissions from the fireplace com-bustion of pine, oak, and synthetic logs have been analyzedon a compound by compound basis using GC-MS tech-niques identical to those described by Rogge et al. (27-33).Briefly, this consisted of analysis on a Finnigan Model 4000quadrupole GC-MS system in the electron impact ionizationmode (70 eV). Sample introduction was by splitless injectiononto a DB-1701 capillary column (30 m× 0.25 mm i.d.), andthe operating conditions were as follows: injection at 65 °C,isothermal hold at 65 °C for 10 min, temperature programfrom 65 to 275 °C at 10 °C/min, isothermal hold at 275 °Cfor 49 min, and using He as carrier gas. Mass spectrometricdata were acquired and processed using a Finnigan INCOSdata system. Compound identification was conducted byreference to authentic standards injected onto the GC-MSsystem, by reference to the National Institute of Standardsand Technology (NIST) mass spectral data base accessed bythe INCOS Data System, and by reference to the NIST/EPA/NIH mass spectral data base (PC Version 4.0) distributed byNIST. Lignans were identified by comparison to publishedmass spectra (34-37). In general, lignans show strongmolecular ions as trimethylsilyl ethers, facilitating theidentification process (22). Compound identification waslabeled accordingly: (a) positive, the sample mass spectrum,library mass spectrum, and authentic standard mass spec-trum compared well and showed identical retention times;(b) probable, same as before except no authentic standardswere available, but the library mass spectrum and the samplemass spectrum agreed well; (c) possible, same as above exceptthe sample spectrum contained information from othercompounds but with minor overlap; (d) tentative, the samplespectrum contained additional information from possiblyseveral compounds (noise) with overlap.

Discussion and ResultsChemical Constituents of Wood. Emissions from thecombustion of any type of fuel depend directly on thechemical composition of the fuel and the combustionconditions. To appreciate the chemical structures found inwood smoke, it is necessary to first understand their originin the wood itself. Different species of trees develop markedlydifferent woody constituents during growth. In temperateregions, conifers are prolific resin producers, while deciduoustrees (for example, oak) do not synthesize such compounds.Typically, all tree wood consists of various forms of lignins(20-30% dry weight of wood, d.w.w.), celluloses (40-50%d.w.w.), hemicelluloses (20-30% d.w.w.), and extraneouscompounds (extractives and ash together, 4-10% d.w.w.)(38). Together, lignins and celluloses are responsible for therigidity of wood that allows it to be used for construction.Cellulose provides a supporting mesh that is reinforced bylignin polymers. The lignin biopolymers are derived fromp-coumaryl, coniferyl, and sinapyl alcohols and containmainly anisyl, vanillyl, and syringyl nuclei (22, 39). Tannins,terpenes, and other compounds add to the woody tissue,

making it a complex substance that is altered duringcombustion causing the characteristic wood smoke odor offireplaces. Many softwood species are prolific resin produc-ers. The softwood genera, including pines (pinus), spruces(picea), larches (larix), and firs (pseudotsuga), have well-established systems of horizontal and vertical resin ducts(40, 41). Synthetic logs are typically proprietary productsmanufactured using sawdust and petroleum waxes. Thesemajor differences in fuel composition are reflected directlyin the compounds emitted during the separate source tests.

Changes in Cut Wood. The moisture contents of fresh-cut green soft- and hardwood can differ drastically. Majordifferences in moisture content also occur between heart-wood and sapwood. The moisture content of wood iscommonly determined by drying wood samples in a con-vection oven at 103 °C. The moisture content of wood isconventionally defined as the ratio of the amount of waterremovable from the sample divided by the dry weight of thewood times 100 and by that definition can exceed 100% (42).The average moisture content of heartwood from softwoodspecies grown in the United States is about 55% (30-121%).Sapwood of the same softwoods shows a mean moisturecontent of 149% (98-249%) (42). Hardwoods instead showa green moisture content that is on average similar for bothheartwood and sapwood, 81% (44-162%) versus 83% (44-149%), respectively (42). Depending on the type of woodand the climate, wood seasoning (air drying) can take from3 to 12 months for firewood. The optimal moisture contentin terms of minimizing particulate emissions during woodcombustion is between 20 and 30% (43). If the moisturecontent is too high, an appreciable amount of energy isnecessary to vaporize the water, reducing the heating valueof the wood as well as decreasing combustion efficiency,which in turn increases particulate smoke formation (43).On the other hand, wood with a moisture content that is toolow burns too fast causing oxygen-limited conditions, whichlead to incomplete combustion with increased wood smokeparticle formation.

During the wood seasoning process (wood weathering),the woody tissue degrades mainly due to photochemicaldegradation of the lignins, causing the formation of organicacids, vanillin, syringaldehyde, and other higher molecularweight compounds that are leachable by water (44). Becausethese photochemical degradation processes occur only inthe outer wood layers, the resulting chemical changes arenot important in terms of the bulk chemical composition offirewood. Biodegradation occurs due to fungal, bacterial,and insect attack. These biochemical changes of wood tissueare slow and therefore are generally not important forrelatively fresh firewood (39).

Wood Combustion Process. When heating wood, thewood constituents start to hydrolyze, oxidize, dehydrate, andpyrolyze with increasing temperature, forming combustiblevolatiles, tarry substances, and highly reactive carbonaceouschar (45). When reaching the ignition temperature of thevolatiles and tarry substances, the exothermic reactionscharacteristic of combustion begin. The heat release gener-ated during flaming combustion first provides the energynecessary for gasification of the wood substrate and propa-gation of the fire as well as evaporation of the “free or capillarywater” found in the cell cavities, followed by the vaporizationof bound water stored in the cell walls (42). Together withthe water, extractives such as resinous compounds anddecomposition products of cellulose, hemicelluloses, andlignin are vaporized (41). They then undergo either partialor complete combustion in the flaming zone. During flamingcombustion, char formation continues until the flux ofcombustible volatile substances drops below the minimumlevel required for the propagation of flaming combustion.Then the smoldering process starts and is best described as

14 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 32, NO. 1, 1998

the gradual oxidation of the reactive char (solid phasecombustion). During the smoldering process, enough heatis produced to propagate the charring process as well ascause the release of additional volatile wood decompositionproducts.

Mass Balance for Elutable Fine Organic Matter. Thetotal ion current traces of the methylated total extracts of thewood smoke samples are shown in Figure 1. All samplesexhibit a major UCM (unresolved complex mixture ofbranched and cyclic compounds) along with resolvedcompounds that include biomarkers and other homologousseries of compounds (e.g., n-alkanes and n-alkenes). Materialbalances are shown for the chemical compositions of the

wood smoke extracts in Figure 2a-c as detected by GC-MS.In the case of pine wood smoke, approximately 30% of thetotal organics mass that elutes from the GC column consistsof individual resolved compounds, while the remaining 70%of the organics exist as an unresolved complex mixture. Ofthe organic compounds that are resolved as distinct peaks,56% can be identified as specific known compounds. Justover half of the identifiable compound mass is present aslignin-derived compounds such as hydroxylated and meth-oxylated phenols and substituted benzenes/benzaldehydes(e.g., vanillin). About 15% of the identified compounds inpine smoke consist of resin acids, accompanied by a severalpercent contribution each from lignans, phytosterols, n-alkanoic acids, and dicarboxylic acids. Trace amounts ofn-alkenoic acids plus polycyclic aromatic hydrocarbons(PAH) and oxy-PAH also are present in pine smoke. Com-pounds identified during fireplace combustion of oak wood

FIGURE 1. Total ion current traces for the total extracts of the woodsmoke samples: (a) pine wood smoke, (b) oak wood smoke, and(c) synthetic log smoke (X, contaminant; SC, internal standard; SR,recovery standard; UCM, unresolved complex mixture).

FIGURE 2. Mass balance for elutable organic matter in the fineparticle emissions from fireplace combustion of (a) pine wood, (b)oak wood, and (c) synthetic log.

VOL. 32, NO. 1, 1998 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 15

TABLE 1. Emission Rates for Organic Compounds Released from Burning Pine Wood, Oak Wood, and Synthetic Logs in ResidentialFireplaces

emission rates (in mg/kg)of logs burned


pinewood

oakwood

syntheticlogs

compdIDb

pinewood

oakwood

syntheticlogs

compdIDb

n-Alkanesnonadecane nda nd 8.80 a hentriacontane 0.48 0.077 18.84 aeicosane nd nd 21.74 a dotriacontane 0.19 nd 18.97 aheneicosane 0.44 0.32 15.98 a tritriacontane 0.13 0.027 23.63 adocosane 0.45 0.28 16.41 a tetratriacontane 0.12 0.023 29.45 atricosane 0.41 0.41 19.94 a pentatriacontane nd nd 37.53 atetracosane 0.29 0.26 20.24 a hexatriacontane nd nd 39.22 apentacosane 0.28 0.25 18.03 a heptatriacontane nd nd 44.15 bhexacosane 0.36 0.20 17.74 a octatriacontane nd nd 45.36 bheptacosane 0.47 0.094 18.18 a nonatriacontane nd nd 42.87 boctacosane 0.41 0.13 17.58 a tetracontane nd nd 38.01 bnonacosane 0.61 0.15 17.62 atriacontane 0.42 0.089 17.19 a total class emission rate 5.06 2.31 547.48

n-Alkenesnonadecene nd nd 12.48 b hentriacontene nd nd 10.32 beicosene nd nd 18.11 b dotriacontene nd nd 8.29 bheneicosene nd nd 24.40 b tritriacontene nd nd 5.70 bdocosene nd nd 19.98 b tetratriacontene nd nd 5.34 btricosene nd nd 20.67 b pentatriacontene nd nd 5.19 btetracosene nd nd 22.96 b hexatriacontene nd nd 5.97 bpentacosene nd nd 23.99 b heptatriacontene nd nd 4.40 bhexacosene nd nd 21.92 b octatriacontene nd nd 4.38 bheptacosene nd nd 19.13 b nonatriacontene nd nd 4.31 boctacosene nd nd 14.81 b tetracontene nd nd 3.82 bnonacosene nd nd 10.88 btriacontene nd nd 14.55 b total class emission rate 281.60

Cyclohexylalkanescyclohexylpentacosane nd nd 0.77 b cyclohexylhentriacontane nd nd 3.99 bcyclohexylhexacosane nd nd 0.71 b cyclohexyldotriacontane nd nd 2.59 bcyclohexylheptacosane nd nd 0.75 b cyclohexyltritriacontane nd nd 2.18 bcyclohexyloctacosane nd nd 1.77 b cyclohexyltetratriacontane nd nd 1.17 bcyclohexylnonacosane nd nd 3.13 bcyclohexyltriacontane nd nd 4.17 b total class emission rate 21.23

n-Alkanalsnonanal nd nd 2.97 a docosanal nd nd 20.21 bdecanal nd nd 1.13 b tricosanal nd nd 17.21 bundecanal nd nd 0.94 b tetracosanal nd nd 16.27 bdodecanal nd nd 2.25 b pentacosanal nd nd 14.56 btridecanal nd nd nd b hexacosanal nd nd 13.89 btetradecanal nd nd 4.12 b heptacosanal nd nd 16.28 bpentadecanal nd nd 8.02 b octacosanal nd nd 20.59 bhexadecanal nd nd 6.15 b nonacosanal nd nd 31.95 bheptadecanal nd nd 9.19 b triacontanal nd nd 41.17 boctadecanal nd nd 13.48 b hentriacontanal nd nd 39.76 bnonadecanal nd nd 8.82 b dotriacontanal nd nd 31.60 beicosanal nd nd 12.54 bheneicosanal nd nd 14.64 b total class emission rate 347.74

n-Alkanoic Acidsc

nonanoic acid nd 0.24 0.97 a heneicosanoic acid 5.15 1.50 0.92 adecanoic acid 0.095 0.39 0.70 a docosanoic acid 7.98 4.65 0.99 aundecanoic acid nd nd 0.82 a tricosanoic acid 1.63 2.16 0.55 adodecanoic acid 1.85 1.65 1.41 a tetracosanoic acid 9.87 13.89 1.70 atridecanoic acid nd nd 1.26 a pentacosanoic acid 0.85 1.29 0.80 atetradecanoic acid 1.74 4.89 2.27 a hexacosanoic acid 1.55 6.76 0.67 apentadecanoic acid 0.85 1.55 2.64 a heptacosanoic acid 0.096 0.33 0.49 ahexadecanoic acid [palmitic acid] 13.91 21.46 10.11 a octacosanoic acid 0.15 0.64 0.49 aheptadecanoic acid 1.62 2.55 1.79 a nonacosanoic acid nd 0.098 0.38 aoctadecanoic acid [stearic acid] 4.31 3.33 2.33 a triacontanoic acid nd 0.079 0.29 anonadecanoic acid 0.51 0.41 0.93 aeicosanoic acid 6.46 2.59 1.46 a total class emission rate 58.62 70.46 33.97

n-Alkenoic Acidsc

cis-9-octadecenoic acid [oleic acid] 7.62 1.15 0.93 a total class emission rate 15.97 2.60 0.939,12-octadecadienoic acid [linoleic acid] 8.35 1.45 nd a

Dicarboxylic Acidsc

propanedioic acid [malonic acid] 38.35 nd nd a hexanedioic acid [adipic acid] 0.63 1.75 nd abutanedioic acid [succinic acid] 0.89 11.68 nd amethylbutanedioic acid nd 3.35 nd a total class emission rate 46.52 22.22pentanedioic acid [glutaric acid] 6.65 5.44 nd a

Resin Acidsc

abietic acid 42.00 nd nd b isopimaric acid 26.55 nd nd bdehydroabietic acid 37.23 5.60 nd b 7-oxodehydroabietic acid 3.31 nd nd a13-isopropyl-5R-podocarpa- 2.02 nd nd b sandaracopimaric acid 47.03 nd nd b

6,8,11,13-tetraen-16-oic acid8,15-pimaradien-18-oic acid 4.02 nd nd b total class emission rate 166.33 5.60pimaric acid 24.17 nd nd a


TABLE 1 (Continued)



pinewood

oakwood

syntheticlogs

compdIDb

pinewood

oakwood

syntheticlogs

compdIDb

Other Acidsc

2-furancarboxylic acid 3.02 1.77 nd b 4-hydroxy-3-methoxyphenylacetic 82.82 15.02 nd a3-hydroxybenzoic acid 4.28 7.53 nd b acid [homovanillic acid]

[salicylic acid]d 3,4,5-trimethoxybenzoic acid f nd 22.57 nd a3,4-dimethoxybenzoic acid 65.04 18.68 0.69 a

[veratric acid]e total class emission rate 160.88 66.57 0.693-4-dimethoxyphenylacetic acid 5.72 nd nd a

[homoveratric acid]

Hydroxylated/Methoxylated Phenols1,4-benzenediol [hydroquinone]g 61.78 22.52 nd b 1-(4-methoxyphenyl)ethanone 5.19 3.78 nd b1,3-benzenediol [resorcinol]h 3.33 3.54 nd b 3,4-dimethoxyphenylacetone 10.41 6.34 nd b3-methyl-1,2-benzenediol 34.94 13.27 nd b [veratrylacetone]

[3-methylcatechol]i 1-(2,4-dimethoxyphenyl)propan-2-one 8.98 2.37 nd b4-methyl-1,2-benzenediol 19.53 3.33 nd a 1-(4-hydroxy-3-methoxyphenyl)- 36.27 3.63 0.78 b

[4-methylcatechol] j ethan-2-one [acetoguaiacol]4-propylbenzenediolk 18.75 nd nd b 1-(4-hydroxy-3-methoxyphenyl)- 39.32 10.73 0.79 b2-methyl-5-(1-methylethyl)-2,5- 0.58 nd nd b propan-2-one

cyclohexadien-1,4-dione [guaiacyclacetone][thymoquinone] 1-(3,5-dimethoxy-4-hydroxyphenyl)- nd 55.52 15.79 a

2-methoxy-4-(2-propenyl)phenol 1.54 nd nd b ethan-2-one[eugenol] [acetosyringol]

2-methoxyphenol [guaiacol] 0.21 0.067 nd b 1-(3,5-dimethoxy-4-hydroxyphenyl)- nd 20.82 5.93 b2-methoxy-4-methylphenol 0.78 0.042 nd b propan-2-one

[4-methylguaiacol] [syringylacetone]2-methoxy-4-propylphenol 19.53 3.37 nd b 2,6-dimethoxy-4-(2-propenyl)phenol nd 1.98 nd b

[4-propylguaiacol] 1-(3,4,5-trimethoxyphenyl)ethan-2-one nd 35.61 5.55 b2-methoxy-4-(1-propenyl)phenol 8.04 0.16 nd b 1-(3,4,5-trimethoxyphenyl)- nd 80.27 nd b2,6-dimethoxyphenol [syringol] 1.13 10.81 nd a propan-2-one

dimers and lignansbis(3,4-dimethoxyphenyl)methane 6.34 0.81 nd b tetrahydro-3,4-diveratrylfuran 3.84 0.13 nd bdivanillyl 22.25 2.38 nd b dihydrovanillylsyringyl-2(3H)- 4.93 nd nd btetrahydro-3,4-divanillylfuran 22.87 0.60 nd b furanone

[deoxomatairesinol] bisguaiacylsyringyl nd 3.08 nd btetrahydro-3-vanillyl-4-veratrylfuran 8.93 0.35 nd b disyringyl nd 7.10 nd bdihydro-3,4-divanillyl-2(3H)- 2.78 nd nd b bis(3,4,5-trimethoxyphenyl)ethane nd 0.77 nd b

furanone [matairesinol]dihydro-3,4-diveratryl-2(3H)-

furanone2.24 nd nd b total class emission rate 344.49 293.38 28.84

Substituted Benzenes/Benzaldehydes1,2-dimethoxybenzene [veratrole] 2.96 1.89 nd a 3,4-dimethoxybenzaldehyde 22.62 4.60 nd a1,3-dimethoxybenzene 1.02 1.84 nd b [veratraldehyde]1,4-dimethoxybenzene nd 1.52 nd b 4-hydroxy-3,5-dimethoxy- nd 66.61 15.86 a1,4-dimethoxy-2-methylbenzene 28.12 nd nd b benzaldehyde [syringaldehyde]3-methoxy-4-hydroxybenzaldehyde 29.27 2.05 nd a 3,4,5-trimethoxybenzaldehyde nd 62.42 5.28 a

[vanillin]3-methoxybenzaldehyde 0.74 nd nd b total class emission rate 84.73 140.93 21.14

[anisaldehyde]

Phytosterolsâ-sitosterol 45.50 9.94 nd a total class emission rate 48.37 11.23stigmast-4-en-3-one 2.87 1.29 nd b

Polycyclic Aromatic Hydrocarbons (PAH)phenanthrene 0.47 0.30 0.46 a dimethyl(fluoranthenes, pyrenes) nd nd 0.78 banthracene 0.051 0.057 0.07 a benzo[k]fluoranthene 0.51 0.26 0.51 amethyl(phenanthrenes, nd nd 0.75 b benzo[b]fluoranthene 0.53 0.21 0.42 a

anthracenes) benzo[j]fluoranthene 0.28 0.11 0.14 adimethyl(phenanthrenes, nd nd 0.79 b benzo[e]pyrene 0.30 0.13 0.44 a

anthracenes) benzo[a]pyrene 0.62 0.23 0.40 a1-methyl-7-isopropylphenanthrene 0.68 0.11 2.72 a perylene 0.12 0.038 0.043 a

[retene] indeno[1,2,3-cd]pyrene 0.087 0.047 0.10 afluoranthene 1.24 0.40 0.70 a indeno[1,2,3-cd]fluoranthene 0.35 0.15 0.26 apyrene 1.59 0.53 0.94 a benzo[ghi]perylene 0.32 0.13 0.52 abenzacenaphthylene 0.57 0.16 0.24 b anthanthrene 0.12 0.039 nd a2-phenylnaphthalene nd nd 0.21 b dibenz[a,h]anthracene 0.079 0.012 0.045 amethyl(fluoranthenes, pyrenes) 1.19 0.33 0.99 b benzo[b]triphenylene nd nd 0.19 bbenzo[a]fluorene/benzo[b]fluorene 0.056 0.11 0.56 a coronene nd nd 0.10 abenzo[ghi]fluoranthene 0.27 0.11 0.24 acyclopenta[cd]pyrene 0.72 0.23 nd a total class emission rate 11.91 6.77 14.32benzo[c]phenanthrene 0.15 0.033 nd abenz[a]anthracene 0.63 0.21 0.38 achrysene/triphenylene 0.98 2.83 0.75 amethyl(benz[a]anthracenes, nd nd 0.56 b

chrysenes, triphenylenes)


likewise are dominated by lignin-derived combustion prod-ucts. As expected, resin acids as a group are generally absentfrom the oak smoke (since oak trees do not produce suchresins), with the traces of resin acids detected probably dueto previous pine combustion in the fireplace tested. Incontrast, the compounds detected in the synthetic log smokeconsist largely of n-alkanes, n-alkenes, and n-alkanalsaccompanied by a few percent lignin-derived compoundsand other trace constituents. The combustion mechanismsand compositional variations in source material that ex-plain these differences in smoke composition are discussedbelow.

Wood Smoke Aerosol Composition. The individualorganic compounds quantified in wood smoke aerosolsduring this study are summarized in Table 1. Each of themajor organic compound classes present will be discussedin turn.

Aliphatic and Cyclic Hydrocarbons. Smoke emitted frompine as well as oak wood fires contains only very smallamounts of n-alkanes (C20-C34; 2.3-5.0 mg/kg of woodburned). No preference for odd carbon numbered n-alkanesexists, in contrast to the strong carbon number preferencethat is typically seen in the leaf surface waxes from vegetation(e.g., ref 31). The synthetic log burned here, a composite ofsaw dust and petroleum products (heavy paraffin wax), showsan n-alkane emission pattern (C19-C40; Cmax ) C38) that iscomparable to that typically found in crude oils (46-49).The n-alkane emissions from the synthetic log reach anemission rate of more than 500 mg/kg burned. Similarly,n-alkenes (n-alk-1-enes; C19-C40; Cmax ) C25) were found onlyin the fine particulate emissions from burning synthetic logs;again, these are derived from the petroleum products in thesynthetic log and show no predominance for even or oddcarbon numbered homologues. Another paraffinic com-ponent of petroleum, cyclohexylalkanes (C21-C40) have beenidentified in the synthetic log smoke emissions as well(Table 1).

Alkanals and Alkanols. Long-chain n-alkanals andn-alkanols are typically found in the waxy portion of leafsurface materials from plants and trees. n-Alkanals are notdetectable in the smoke emissions from pine and oak woodcombustion, indicating that they are not a major part of thewoody portion of trees. In contrast, synthetic log smokeemissions contain n-alkanals (C9-C32) in amounts compa-rable to n-alkanes or n-alkenes. They are oxidation productsof the n-alkenes (e.g., ref 50) that are also abundant in thesynthetic log smoke. The n-alkanols are not detectablewithout further derivatization in any of these smoke samples.Derivatization with silylating reagents was not carried outfor these initial studies.

Carboxylic Acids. The n-alkanoic and alkenoic acids areubiquitous in the plant as well as animal kingdoms (51-53).

The n-alkanoic and n-alkenoic acids synthesized by biologicalsystems show a preference for even carbon numberedhomologues, often with the C16 and C18 acids as the majorcompounds. Consistent with this expectation, both thenatural wood fires as well as synthetic log combustionexperiments conducted here show that hexadecanoic acid(C16) has the highest emission rate among the carboxylicacid series. Oak and pine smoke particulate matter exhibitsthe typical even-to-odd carbon numbered n-alkanoic aciddistribution that is characteristic for biosynthetic organicmatter (Table 1). In contrast, the synthetic log smokeemission shows a weaker preference for even carbonnumbered n-alkanoic acids, reflecting the combined sawdustplus crude oil origin of the synthetic log material.

Dicarboxylic (R,ω-alkanedioic) acids are detectable in thewood smoke samples but not in the synthetic log smoke(Table 1). Only the short-chain homologues from C3 to C6

are observed.

Diterpenoid Acids and Retene. Resin acids [e.g., abietic(I, see Figure 3 for structures cited), pimaric (II), isopimaric(III), and sandaracopimaric (IV) acids] are synthesized mainlyby conifers (gymnosperms) in the temperate regions of theNorthern Hemisphere (54, 55). Deciduous trees native totropical zones are also prolific resin and gum producers, buttypically contain no tricyclic resin acids (e.g., refs 56 and 57).

During the combustion of coniferous wood, tricyclic resinacids are released due to volatilization by steam in eithertheir unaltered form, partially altered, or completely com-busted (22). Common altered resin acids are dehydroabietic(V) and 7-oxodehydroabietic (VI) acids. Retene (1-methyl-7-isopropylphenanthrene, VII), a completely dehydrogenatedresin diterpenoid, is a pyrolysis end product from diterpe-noids that have the abietane or pimarane skeletons (17, 23).Depending on the combustion parameters (e.g., combustiontemperature, excess air) and fuel parameters (moisturecontent, log size, wood type) greater or lesser amounts ofunaltered, partially altered, and pyrolyzed diterpenoids arefound in the smoke emissions. Table 1 illustrates largely theeffect of variation in wood type between pine and oak asother combustion conditions were similar.

Here, in the fine particle emissions from burning of pinewood, the unaltered resin acids such as abietic (I) andsandaracopimaric (IV) acids show the highest emissionrates (42 and 47 mg/kg of pine wood burned, respectively,Figure 4). In contrast, dehydroabietic acid (V) is the majoraltered resin acid at 37.2 mg/kg (Figure 4). Small amountsof dehydroabietic acid also have been found during theoak wood burning experiments conducted here (Figure 4).Because oak wood typically does not contain resinouscompounds, we believe that this represents carry over ofcompounds evolved from soot deposits on the chimney

TABLE 1 (Continued)



pinewood

oakwood

syntheticlogs

compdIDb

pinewood

oakwood

syntheticlogs

compdIDb

Oxo-PAH1H-phenalen-1-one 1.87 0.81 0.75 b 6H-benzo[cd]pyren-6-one nd nd 0.11 b9,10-phenanthrenedione nd nd 0.38 a [benzo[cd]pyrenone]

[phenanthrenequinone]1H-benz[de]anthracen-1-one 0.13 0.076 nd a total class emission rate 2.50 1.08 1.547H-benz[de]anthracen-7-one 0.50 0.19 0.30 a

a nd, not detected. b For more details see text. a, positive: authentic std. verification; b, probable: library spectrum verification; c, possible;d, tentative. c Analyzed as methyl esters. d Determined as 2-methoxybenzoic acid [o-anisic acid]. e Could also have been originally 4-hydroxy-3-methoxybenzoic acid [vanillic acid] or both due to the methylation step. f Could also have been originally 4-hydroxy-3,5-dimethoxybenzoic acid[syringic acid] or both due to the methylation step. g Determined as 2-methoxyphenol in the methylated fraction only. h Determined as3-methoxyphenol in the methylated fraction only. i Determined as 2-methoxy-3-methylphenol in the methylated fraction only. j Determined as2-methoxy-4-methylphenol in the methylated fraction only. k Determined as 2-methoxy-4-propylphenol in the methylated fraction only.


walls due to previous pine wood fires conducted in the samefireplace.

The synthetic log burned during the present experimentsshows no detectable levels of resin acids. In contrast, retene

is substantially more abundant in the synthetic log smokethan in pine or oak smoke aerosol emissions. This indicatesthat the slow combustion process typical of synthetic logsproduces an enhanced tendency to pyrolyze log constituents,

FIGURE 3. Chemical structures of the biomarkers and their derivatives cited in the text by Roman numerals.


which is also expressed in the form of increased PAHemissions from such logs.

Dehydroabietic acid has been proposed as a candidatemarker compound for coniferous wood combustion (22, 58).Later in this paper, that hypothesis will be tested by theexamination of resin acids concentrations in the Los Angelesarea atmosphere.

Lignin Combustion Products. As mentioned before, asubstantial portion of wood consists of biopolymers such aslignin. The lignin of gymnosperms (e.g., pine) is primarilyderived from monomers such as coniferyl alcohol (VIII) and

to a lesser degree of sinapyl alcohol (IX) (59). In contrast,lignin of angiosperms (e.g., oak) is enriched in the sinapylalcohol monomers. Upon combustion of wood, the ligninbiopolymer emits breakdown products that include aromaticphenols, aldehydes, ketones, acids, and alcohols. Dependingon the combustion and fuel parameters, some thermalalteration products of lignin are volatilized before completecombustion can occur. In the smoke emissions, guaiacyl(substituted 2-methoxyphenol, X) and syringyl (substituted2,6-dimethoxyphenol, XI) type phenyl rings, often with theoriginal C1-C3 substituents, condense on preexisting smokeparticles. Because the monomers in the lignin are connectedvia the substituent para to the -OH group to the polymer, thelignin breakdown products differ only in that substituent.Thus, guaiacyl derivatives (X) are typically favored in pinewood smoke, whereas syringyl (XI) derivatives are nearlyexclusively found in oak wood smoke (22). Previously, severalresearchers have suggested that guaiacyl derivatives arepotential tracers for both types of wood smoke, while syringylderivatives are indicative for hardwood smoke only (4, 19-22, 60).

The major guaiacyl derivatives quantified in pine woodsmoke are vanillic acid/veratric acid, homovanillic acid,veratraldehyde, guaiacylacetone, vanillin, and others (Figure5). Because veratric as well as vanillic acids are both toopolar without methylation for elution from the GC column,the veratric acid methyl ester identified could also haveoriginally been vanillic acid where the second hydroxy groupwas methylated. Guaiacyl type compounds have beenquantified in the oak wood smoke emissions (Table 1), butthe respective guaiacyl derivatives show much lower emissionrates than in the case of pine wood smoke (Figure 5). Themajor syringyl derivatives in oak smoke are syringaldehyde,syringic acid, syringol, acetosyringol, and syringylacetone(Table 1, Figure 5). The synthetic log smoke does contain

FIGURE 4. Distributions of resin acids from wood burning in aresidential fireplace: (9) pine, (0) oak.

FIGURE 5. Distributions of the dominant lignin breakdown productsfrom wood burning in a residential fireplace: (9) pine, (0) oak.

FIGURE 6. Distributions of lignans and lignin breakdown product“dimers” from wood burning in a residential fireplace: (9) pine,(0) oak.


acetosyringol, syringaldehyde, syringylacetone, and a traceof veratric acid, which indicates that the log also contains atleast some hardwood saw dust (angiosperm).

Dimers and Lignans. Guaiacyl and less prevalent syringyldimers appear to form on smoke particles from theirubiquitous monomer radicals (20, 22). Lignans are naturalproduct dimers from coniferyl and/or sinapyl alcohols andare found as such in wood. They serve as natural toxins andfillers and are recognizable in the smoke as the naturalproducts or slightly altered (deoxygenated) derivatives (61).Minor amounts of mainly guaiacyl dimers and lignans arefound in the pine smoke, to a much lesser extent in the oaksmoke (Figure 6), and not at all in the smoke from thesynthetic logs. Major compounds include divanillyl (XII, R) H), disyringyl (XII, R ) OCH3), deoxomatairesinol (XIII, R) H), and matairesinol (R ) O) (Table 1), and some may beuseful tracers of wood smoke in the atmosphere.

Phytosterols. Phytosterols are the sterols of higher plantsand are generally comprised of the C28 and C29 compounds,with â-sitosterol (C29, XIV) as the dominant component (62-64). Pine smoke has a significant content of â-sitosterol (45.5mg/kg), and this compound is also present in the oak smokebut not in the smoke from the synthetic logs. A minor amountof stigmast-4-en-3-one (XV) is detectable in the wood smokesamples (Table 1). This compound is an alteration productfrom mild thermal dehydrogenation of â-sitosterol.

Polycyclic Aromatic Compounds. The polycyclic aro-matic hydrocarbons (PAHs) reported here for the varioussmoke samples range from phenanthrene to coronene (Table1). The smoke from the synthetic log has the highest totalPAH emission rate and the most diverse suite of PAHs. Themajor PAHs in the pine wood smoke are retene (VII),fluoranthene, pyrene, and chrysene/triphenylene. Retene(0.68 mg/kg) is present from the thermal alteration ofditerpenoids in the conifer wood. Furthermore, it is detect-able in the smoke from oak wood and is the PAH with thehighest emission rate (2.72 mg/kg) in the smoke from thesynthetic log. The other PAHs reflect a product compositiontypical of the emissions from higher temperature combustionof organic detritus (65).

oxy-PAH are detectable in these smoke samples, and thedominant compounds are polycyclic aromatic ketones (PAKs)

and phenanthrenequinone (Table 1). The low level ofquinones in oak and pine smoke fits with the interpretationthat when these compounds are found in the atmospherethey are the secondary oxidation products formed byatmospheric chemical reactions from the ordinary PAHs(66-68).

Resin Acids in the Atmosphere. Resin acids are some ofthe most prominent thermal alteration products of coniferresins and thus may well serve as tracers for wood smoke inthe urban atmosphere. To check the consistency of thathypothesis, the atmospheric concentrations of all woodsmoke resin acids measured in cities in the Los Angeles areaby Rogge et al. (32) were summed and then graphed to revealtheir seasonal concentration pattern (see Figure 7). Emissioninventory data compiled via telephone survey by Gray (2)recorded that 70% of the wood burned in southern Californiain 1982 was burned in the three winter months of the year,while only 2.3% of total wood burning was reported to occurin the three summer months. That extreme seasonalvariation is clearly reflected in the atmospheric resin acidsconcentration time series shown in Figure 7 and suggeststhat the resin acids indeed are useful tracers for wood smokein this urban area.

AcknowledgmentsWe thank Ed Ruth for his assistance with the acquisition ofthe mass spectrometry data and the staff of the CaltechHousing Office for providing the house in which thesefireplace source tests were conducted. This research wassupported by the California Air Resources Board underAgreement A932-127. Portions of the work benefited fromresearch supported by the U.S. Environmental ProtectionAgency under Agreement R-813277-01-0 and by the SouthCoast Air Quality Management District. Partial funding alsowas provided by the U.S. Department of Energy underContract DE-AC02-76CH00016. The statements and conclu-sions in the report are those of the contractor and notnecessarily those of the California Air Resources Board. Themention of commercial products, their source, or their usein connection with material reported herein is not to beconstrued as actual or implied endorsement of such products.

FIGURE 7. Seasonal variation of total fine particle wood smoke resin acids concentrations in the atmosphere of communities in the LosAngeles area (from ref 32).


This manuscript has not been subject to the EPA’s peer andpolicy review and, hence, does not necessarily reflect theviews of the EPA.

Literature Cited(1) Lipfert, F. W.; Dungan, J. L. Science 1983, 219, 1425-1427.(2) Gray, H. A. Control of atmospheric fine carbon particle

concentrations. Ph.D. Thesis, California Institute of Technology,Pasadena, 1986.

(3) Core, J. E.; Cooper, J. A.; Newlicht, R. M. J. Air Pollut. ControlAssoc. 1984, 34, 138-143.

(4) Hawthorne, S. B.; Miller, D. J.; Langenfeld, J. J.; Krieger, M. S.Environ. Sci. Technol. 1992, 26, 2251-2283.

(5) Honicky, R. E.; Osborne, J. S.; Akpom, C. A. Pediatrics 1985, 75,587-593.

(6) Ramdahl, T.; Schjoldager, J.; Currie, L. A.; Hanssen, J. E.; Moller,M.; Klouda, G. A.; Alfheim, I. Sci. Total Environ. 1984, 36, 81-90.

(7) Sexton, K.; Spengler, J. D.; Treitman, R. D.; Turner, W. A. Atmos.Environ. 1984, 18, 1357-1370.

(8) Standley, L. J.; Simoneit, B. R. T. Environ. Sci. Technol. 1987, 21,163-169.

(9) Muhlbaier-Dasch, J. Environ. Sci. Technol. 1982, 16, 639-645.(10) Hildemann, L. M.; Markowski, G. R.; Cass, G. R. Environ. Sci.

Technol. 1991, 25, 744-759.(11) Claessens, H. A.; Lammerts van Bueren, L. G. D. J. High Resolut.

Chromatogr. 1987, 10, 342-347.(12) Freeman, D. J.; Cattell, F. C. R. Environ. Sci. Technol. 1990, 24,

1581-1585.(13) Guenther, F. R.; Chesler, S. N.; Gordon, G. E.; Zoller, W. H. J.

High Resolut. Chromatogr. 1988, 11, 761-766.(14) Kleindienst, T. E.; Shepson, P. B.; Edney, E. O.; Claxton, L. D.;

Cupitt, L. T. Environ. Sci. Technol. 1986, 20, 493-501.(15) Kamens, R. M.; Rives, G. D.; Peery, J. M.; Bell, D. A.; Paylor, R.

F.; Goodman, R. G.; Claxton, L. D. Environ. Sci. Technol. 1984,18, 523-530.

(16) Kamens, R. M.; Bell, D.; Dietrich, A.; Peery, J. M.; Goodman, R.G.; Claxton, L. D.; Tejada, S. Environ. Sci. Technol. 1985, 19,63-69.

(17) Ramdahl, T. Nature 1983, 306, 580-582.(18) Ramdahl, T.; Becher, G. Anal. Chim. Acta 1982, 144, 83-91.(19) Edye, L. A.; Richards, G. N. Environ. Sci. Technol. 1991, 25, 1133-

1137.(20) Hawthorne, S. B.; Miller, D. J.; Barkley, R. M.; Krieger, M. S.

Environ. Sci. Technol. 1988, 22, 1191-1196.(21) Hawthorne, S. B.; Krieger, M. S.; Miller, D. J.; Mathiason, M. B.

Environ. Sci. Technol. 1989, 23, 470-475.(22) Simoneit, B. R. T.; Rogge, W. F.; Mazurek, M. A.; Standley, L. J.;

Hildemann, L. M.; Cass, G. R. Environ. Sci. Technol. 1993, 27,2533-2541.

(23) Simoneit, B. R. T.; Mazurek, M. A. Atmos. Environ. 1982, 16,2139-2159.

(24) Standley, L. J.; Simoneit, B. R. T. Atmos. Environ. 1990, 24B,67-73.

(25) Schauer, J. J.; Rogge, W. F.; Hildemann, L. M.; Mazurek, M. A.;Cass, G. R.; Simoneit, B. R. T. Atmos. Environ. 1996, 30, 3837-3855.

(26) Hildemann, L. M.; Markowski, G. R.; Cass, G. R. Aerosol Sci.Technol. 1989, 10, 193-204.

(27) Rogge, W. F.; Hildemann, L. M.; Mazurek, M. A.; Cass, G. R.;Simoneit, B. R. T. Environ. Sci. Technol. 1991, 25, 1112-1125.





(32) Rogge, W. F.; Mazurek, M. A.; Hildemann, L. M.; Cass, G. R.;Simoneit, B. R. T. Atmos. Environ. 1993, 27A, 1309-1330.


(34) Duffield, A. M. J. Heterocycl. Chem. 1967, 4, 16-22.(35) Pelter, A. J. Chem. Soc. (C) 1967, 1376-1380.(36) Pelter, A. J. Chem. Soc. (C) 1968, 74-79.(37) Pelter, A.; Stainton, A. P.; Barber, M. J. Heterocycl. Chem. 1966,

3, 191-197.(38) Libby, C. In Pulp and Paper Science and Technology; McGraw-

Hill: New York, 1962; pp 82-107.

(39) Hedges, J. I. In The Chemistry of Solid Wood; Rowell, R. M., Ed.;Advances in Chemistry Series 207; American Chemical Society:Washington, DC, 1984; pp 111-140.

(40) Parham, R. A.; Gray, R. L. In The Chemistry of Solid Wood; Rowell,R. M., Ed.; Advances Chemistry Series 207; American ChemicalSociety: Washington, DC, 1984; pp 3-56.

(41) Petterson, R. C. In The Chemistry of Solid Wood; Rowell, R. M.,Ed.; Advances in Chemistry Series 207; American ChemicalSociety: Washington, DC, 1984; pp 57-126.

(42) Skaar, C. In The Chemistry of Solid Wood; Rowell, R. M., Ed.;Advances in Chemistry Series 207; American Chemical Society:Washington, DC, 1984; pp 127-174.

(43) Core, J. E.; Cooper, J. A.; DeCesar, R. T.; Houck, J. E. ResidentialWood Combustion Study; EPA 910/9-82-089a; U.S. EPA: Seattle,WA, 1982.

(44) Feist, W. C.; Hon, D. N.-S. In The Chemistry of Solid Wood;Rowell, R. M., Ed.; Advances in Chemistry Series 207; AmericanChemical Society: Washington, DC, 1984; pp 401-454.

(45) Shafizadeh, F. In The Chemistry of Solid Wood; Rowell, R. M.,Ed.; Advances in Chemistry Series 207; American ChemicalSociety: Washington, DC, 1984; pp 489-530.

(46) Bray, E. E.; Evans, E. D. Geochim. Cosmochim. Acta 1961, 22,2-15.

(47) Hunt, J. M. Petroleum Geochemistry and Geology, 2nd ed.; W.H. Freeman & Co.: New York, 1996.

(48) Simoneit, B. R. T. Atmos. Environ. 1984, 18, 51-67.(49) Simoneit, B. R. T. Int. J. Environ. Anal. Chem. 1985, 22, 203-

233.(50) Leif, R. N.; Simoneit, B. R. T. Org. Geochem. 1995, 23, 889-904.(51) Mazurek, M. A.; Simoneit, B. R. T. In Identification and Analysis

of Organic Pollutants in Air; ACS Symposium; Keith, L. H., Ed.;Ann Arbor Science/Butterworth Publishers: Woburn, MA, 1984;pp 353-370.

(52) Simoneit, B. R. T. In Chemical Oceanography, 2nd ed.; Riley, J.P., Chester, R., Eds.; Academic Press: New York, 1978; Vol. 7,Chapter 39, pp 233-311.

(53) Simoneit, B. R. T. J. Atmos. Chem. 1989, 8, 251-275.(54) (a) Simoneit, B. R. T.; Grimalt, J. O.; Wang, T. G.; Cox, R. E.;

Hatcher, P. G.; Nissenbaum, A. In Advances in Organic Geo-chemistry 1985; Leythaeuser, D., Rullkotter, J., Eds.; Pergamon:Oxford, 1986. (b) Org. Geochem. 1986, 10, 877-889.

(55) (a) Grimalt, J. O.; Simoneit, B. R. T.; Hatcher, P. G.; Nissenbaum,A. In Advances in Organic Geochemistry 1987; Mattavelli, L.,Novelli, L., Eds.; Pergamon: Oxford, 1988. (b) Org. Geochem.1988, 13, 677-690.

(56) Simoneit, B. R. T.; Cox, R. E.; Standley, L. J. Atmos. Environ.1988, 22, 983-1004.

(57) Simoneit, B. R. T.; Cardoso, J. N.; Robinson, N. Chemosphere1990, 21, 1285-1301.

(58) Standley, L. J.; Simoneit, B. R. T. J. Atmos. Chem. 1994, 18, 1-15.(59) Sarkanen, K. V.; Ludwig, C. H. In Lignins, Wiley and Sons: New

York, 1971; pp 1-18.(60) Steiber, R. S. J. Air Waste Manage. Assoc. 1993, 43, 859-863.(61) Grimshaw, J. In Rodd’s Chemistry of Carbon Compounds, 2nd

ed.; Coffey, S., Ed.; Elsevier: Amsterdam, 1976; Vol. IIID, pp203-278.

(62) de Leeuw, J. W.; Baas, M. In Biological Markers in the SedimentaryRecord; Johns, R. B., Ed.; Elsevier: Amsterdam, 1986; pp 101-123.

(63) Chen, X.-J. Oxygenated natural products in troposphericaerosolsssources and transport. M.Sc. Thesis, Oregon StateUniversity, Corvallis, OR, 1991.

(64) Volkman, J. K. Org. Geochem. 1986, 9, 83-99.(65) Crittenden, B. D.; Long, R. In Carcinogenesissa Comprehenisve

Study; Freudenthal, R. I., Jones, P. W., Eds.; Raven: New York,1976; pp 209-224.

(66) Ramdahl, T. Environ. Int. 1985, 11, 197-203.(67) Korfmacher, W. A.; Natusch, D. F. S.; Taylor, D. R.; Mamantov,

G.; Wehry, E. L. Science 1980, 207, 763-765.(68) Simoneit, B. R. T.; Sheng, G.; Chen, X.; Fu, J.; Zhang, J.; Xu, Y.

Atmos. Environ. 1991, 25A, 2111-2129.

ES960930B

X Abstract published in Advance ACS Abstracts, November 1, 1997.


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Sources of Fine Organic Aerosol. 9. Pine, Oak, and Synthetic Log Combustion in Residential Fireplaces