Luận án tiến sĩ: Sugars and plyol compounds in ambient aerosols and cooking fume aerosols

Sugars and Polyol Compounds in Ambient Aerosols and Cooking Fume AerosolsbyWan Chun Hong B.Sc.. 1.1 The role of aerosols in the atmosphere1.2 Chemical composition of atmospheric aerosols

Sugars and Polyol Compounds in Ambient Aerosols and

Cooking Fume Aerosols

byWan Chun HongB.Sc (Hons) in Chemistry, University of Hong Kong, Hong Kong

UMI Number: 3240452

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Sugars and Polyol Compounds in Ambient Aerosols and Cooking Fume Aerosols

byWan Chun Hong

B.Sc (Hons) in Chemistry, University of Hong Kong, Hong Kong

I here declare that I am the sole author of the thesis

I authorize the Hong Kong University of Science and Technology to lend this thesis to

other institutions or individuals for the purpose of scholarly research

I further authorize the Hong Kong University of Science and Technology to reproducethe thesis by photocopying or by other means, in total or in part, at the request of otherinstitutions or individuals for the purpose of scholarly research

a

Wan Chun HongBachelor of Science in Chemistry,University of Hong Kong, Hong Kong

(1999)

ili

Dr Jianzhen Yu, my supervisor, gains the greatest gratitude for her invaluablesupport and guidance during the studies in HKUST She supervises and teaches me themysteries in aerosol science and gives me a support on problem-solving in my researchworks During these years when I have been working in the laboratory, she has given mechallenging projects and tasks to do and to improve myself as a researcher

Sincere thanks go to Prof Jian Zhen YU, my supervisor; Dr Song Gao; Dr LamLung Yeung; Prof Alexis Lau K.H., and Prof Frank Lee Shun Cheng for being themembers of my thesis examination committee

I want to thank all of my colleagues especially, Elber Sit, Hilda Huang and Simon

Ip, in my research group for giving me a pleasant environment to work in In addition, Iwant to express my gratitude to Dr L L Yeung and Mr W K Lau, project assistant togive a great support and assistance in sample collection in kitchen exhaust study and also,the Atmospheric, Marine and Coastal Laboratory to provide a technical support in LC-

MS instrument in my research,

I heavily thank to all members in Food and Environmental Hygiene C Section inHong Kong Government Laboratory during my working period in 2003 — 2005 to givepatience to teach me the technique and knowledge on LCMS

iv

Finally, I’m thankful to all my friends with whom I have been able to discusstopics related to the scientific work as well as enjoy joyful moments I specially thank to

my parents, my sister and my wife, Joyce Ho, for their love and support during my life

1.1 The role of aerosols in the atmosphere

1.2 Chemical composition of atmospheric aerosols

Chapter 2 Literature Review

2.1 Chemical substances in water-soluble carbohydrate-like

compounds2.2 Sources of carbohydrate-like compounds in the atmosphere

2.3 Abundance of target compounds

2.3.1 Levoglucosan

vi

iliii

viXi

xiixvixix

XX

1415

152222

liquid chromatographyDetermination of Total Water-soluble Sugar andPolyol Contents in Ambient Aerosols

IntroductionExperimental Section3.2.1

3.2.23.2.3

3.2.4

Chemical and reagentsPreparation and analysis of standard solutionsAerosol sampling

3.2.3.1 Sampling in Hong Kong3.2.3.2 Sampling in Nanjing3.2.3.3 Sampling in Jeju Island, South KoreaExtraction and analysis of aerosol samplesResults and Discussion

3.3.13.3.23.3.33.3.4

Analytical methodLimit of detectionAbundance of WSMC in bulk ambient aerosolsSize segregated samples collected in Hong Kong

Vii

272929

30

33

37

3842424244

44

454549535335

35

63

IntroductionExperimental Section4.2.1 Reagents and standards4.2.2 Aerosol sample collection and pre-analysis treatmentInstrumentation

LC-MS analysisResults and Discussion4.5.1 Ionization and MS conditions4.5.2 Optimization of chromatographic conditions4.5.3 Seven-point mass calibration

4.5.4 Method recoveries, precision, and limit of detection4.5.5 Analysis of aerosol samples

SummaryAnalysis of Sugars and Polyols by ChlorideAttachment in Liquid Chromatography/Negative IonElectrospray Mass Secptrometry

IntroductionExperimental Section5.2.1 Reagents and Instruments

5.2.2 _ˆ LCMS conditions

Viii

70

7174747475

75

7878818587909498

99

100100

100

5.3.6 Analysis of aerosol samplesSummary

Determination of glycerol, levoglucosan, fatty acidsand cholesterol in cooking oil emission

IntroductionExperimental Section6.2.1 Sample collection from restaurant exhausts6.2.2 Sample collection from heated cooking oil in

controlled chamber experiments6.2.3 Sample extraction and treatment6.2.4 Sample analysis

6.2.4.1 Mass measurement6.2.4.2 Carbon measurement6.2.4.3 Analysis of individual organic compoundsResults and Discussion

6.3.1 MS characeteristics

ix

103105105

126127

127131

134136

136138139141141

6.3.2 Kinetic of BSTFA derivatization reactions

6.3.3 Recovery of standard compounds

6.3.4 Calibration curves and minimum detection limits

6.3.5 Relationship between glycerol, levoglucosan and

other cooking emission compounds

145(147150

152

6.3.6 Target compounds analysis in commercial kitchen exhausts 157

6.3.7 Assessment of contributions of cooking emissions

to ambient levogllucosan and Glycerol

List of Publications

H Yang, J.Z Yu, S.S H Ho, J H Xu, W.S Wu, C H Wan X D Wang,X.R Wang, L S Wang, “The chemical composition of inorganic andcarbonaceous materials in PM2.5 in Nanjing, China”, Atmos Environ., 39(20),

3735 — 3749, 2005

H Yang, J.H Xu, W.S Wu, C H Wan, J Z Yu, “Chemical characterization

of water-soluble organic aerosols at Jeju Island collected during ACE-Asia”,

Environ Chem., 1(1), 13 — 17, 2004

Eric Chun Hong Wan, Jian Zhen Yu, “Determination of Sugar Compounds inatmospheric aerosols by liquid chromatography combined with positiveelectrospray ionization mass spectroscopy”, J Chromatography A, 1107(1-2),

175 — 181, 2006

Eric Chun hong Wan, Jian Zhen Yu, “Determination of Sugar compounds inatmospheric aerosols by liquid chromatography combined negativeelectrospray ionization mass spectroscopy”, in preparation

G.S.W Hagler, M.H Bergin, L.G Salmon, J.Z Yu, Eric C H Wan, M.Zheng, L.M Zeng, C.S Kiang, Y.H Zhang, and J.J Schauer, “Source areasand chemical composition of fine particulate matter in the Pearl River DeltaRegion of China”, Atmospheric Environment, 40, 3802 — 3815, 2006

G.S.W Hagler, M.H Bergin, L.G Salmon, J.Z Yu, Eric C.H Wan, M.Zheng, L.M Zeng, C.S Kiang, Y.H Zhang, J.J Schauer, “Local and regionanthropogenic influence on fine particulate trace elements in Hong Kong”,Atmospheric Environment, in presentation

xi

et al., 1999, (b) Kuhlbush et al., 2000, and (c) Rodriquez et al.,2002.

Chemical composition of PM¿; in Hong Kong (a) Mong Kok(roadside); (b) Tsuen Wan (urban); (c) Hok Tsui (rural)

Mass balance on the chemical composition of annualmean fine concentrations, 1982, for (a) West LosAngeles and (b) Rubidoux (Riverside) from Rogge et al.,1993

Mechanism of the formation of levoglucosan in the pyrolysis

of celluloseChemica! reaction of BSTFA with —OH containing compoundsReaction sequence of the formation of two molecules

of formaldehyde from one molecule of monosaccharideusing glucose as an example

Derivatization of formaldehyde with DNPHExtraction and analysis procedure for determination

of water-soluble monomeric carbohydrate in aerosol samples

Example HPLC chromatogram of the DNPH-derivativesIndividual size distribution of aerosol mass

Size distribution of total water-soluble mono-carbohydrates

xii

19

3241

4131

526568

Peak areas of [M+NHg]" ions versus different compositions

of methanol (a) and acetonitrile (b) in mobile phase

SIM chromatograms of an aerosol sample

(Note levoglucosan is scaled by a factor of 0.3)Calibration curves of individual analytesBackground subtracted ESI- mass spectra of the targetsugar compounds in the presence of CH;C]

Comparison of detection sensitivity between with anwithout addition of CHCl; under two ionization modes,(a) ESI- and (b) APCT-

Comparison of detection sensitivity of three post-columnaddition solution compositions as a function of thepost-column addition flow rate

Chromatograms of a standard mixture of 12 sugars andsugar alcohols

SIM chromatograms of an aerosol sample analyzed using

xiii

69

69

7380

83

84

86106

110

112

114

120

the carbohydrate column.

Schematic diagram of the particulate matter sampling systemControlled chamber experiment set-up Top: chamber;

Bottom: emission collection setupTemperature profile of the heating oil in a controlledchamber experiment

Flow chart of the filter extraction protocolMass spectra of the TMS derivatives of (a) glycerol,(b) levoglucosan, (c) oleic acid, (đ) myristin, and(e) cholesterol

Kinetic reaction of glycerol (A) and levoglucosan (B) inBSTFA reaction

Scatter plots for glycerol versus the fatty acids in nmol/m?

(a) tridecanoic acid; (b) myristic acid; (c) pentadecanoic(b) acid; (d) palmitic acid; (e) heptadecanoic acid;

(c) (f) oleic acid; (g) stearic acid; (h) myristin;

(d) (i) 2-palmitin; (j) 1-palmitin; (k) stearinTypical ECOC thermogram of kitchen exhaust samplesThe 73 ion chromatogram for a sample compoundsCorrelation of glycerol with fatty acids and glyceridescompounds (a) tridecanoic acid; (b) myristic acid;

(c) pentadecanoic acid; (d) palmitic acid; (e) palmitoleicacid; (f) heptadecanoic acid; (g) stearic acid; (h) oleic acid;

XIV

130132

133

137142

146

155

160161164

(c) pentadecanoic acid; (d) palmitic acid; (e) palmitoleic

acid; (f) heptadecanoic acid; (g) stearic acid; (h) oleic acid;

@ myristin; (J) 2-palmitin; (k) 1-palmitin; (1) stearin

Correlation of levoglucosan with TCComparison of levoglucosan/OC ratios in ambientaerosol samples with those in cooking aerosolsand biomass burning aerosols

Comparison of glycerol/OC ratios in ambientaerosol samples with those in cooking aerosolsand biomass burning aerosols

Ambient annual average concentration (ng/m”) for fine

particle organic compounds found in West Los Angeles,downtown Los Angeles, Pasadena, Riverside and SanNicolas Island for 1982

Structure information on those target compounds

Ambient levoglucosan concentration (ng/m”) in

different locations in the world (2002 — 2006)

Concentrations (ng/m”) of individual carbohydrate-like

compounds in various ambient environments in the world(2001- 2005)

Examples of GC analysis of carbohydratesApplications of using LC for determination of individualcarbohydrates

Summary information of aerosol samples collected inJeju Island

Information on portions of filter used for water extractionand final volume of water extracts

Calibration results of a series of monomeric carbohydratesand their relative response to formaldehyde

Summary and comparison of WSMC levels in Hong Kong,

Nanjing and Jeju Island

Concentrations of Water-soluble monomeric carbohydrates

XVi

10

1724

28

3236

in PM2.5 and TSP sample collected in Hong Kong.

Concentrations of WSMC and WSOC in the NJU-SeptemberSamples

Concentrations of WSMC and WSOC in the NJU-Februaryand PMO-Februrary samples

Concentrations of WSMC collected at Jeju IslandAerosol mass concentrations (mg/m?) in individual size bins

Concentration (nmol/m”) of total water-soluble

mono-carbohydrates in individual size bins of the impactorsamples

Molecular weights, MS quantification ions, calibrationcurve parameters, and limits of detection of the targetsugar compounds

Recoveries of target sugar compoundsMeans and ranges of concentrations of the targetsugar compounds detected in aerosol samplesCorrelation (r) matrix of the aerosol concentrations ofthe nine sugar compounds

Cone voltage of each compound under negative ionizationRecovery of the target sugar compounds analyzed using ESI(-)Molecular weights, MS quantification ions, retention times,and limits of detection of the targeted sugar and polyolcompounds

xvi

59

60

626467

77

8992

95

102104

107

Concentrations of major constituents in thirty ambientaerosol samples

Factor loadings of PCA analysisSummary information of the kitchen exhaust samplesTemperature program for the ECOC analysis of thekitchen exhaust samples

Target analytes and the quantification ion used intheir GC-MS determination

Extraction recoveries of target compound with threeextraction methods

Linear regression parameters of calibration curves,limit of detection (LOD), and limit of quantification (LOQ)Air concentrations of target compounds above heatedcooking oil in a controlled chamber experiment

Typical composition of fatty acid in peanut oil

TC results of the kitchen exhaust samples

Concentration of kitchen exhaust sample (ng/m”) in

different commercial kitchen exhaustRatios of levoglucosan/OC in ng/ugC in ambient, cookingemissions, and biomass burning aerosols

170

Table 6.11 Ratios of glycerol/OC in ng/ugC in ambient, cooking

emissions, and biomass burning aerosols

Appendix

Appendix 4A Reports of Hill Fires on 16, 17, and 18 October 2004

Appendix 6A Silylation reaction kinetics of fatty acids, monoglycerides

and cholesterol in the absence and presence of pyridine

Xix

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96173

Sugar and Polyol Compounds in Ambient Aerosols and Cooking Fume Aerosols

by

Wan Chun HongBachelor of Science in Chemistry,University of Hong Kong

(1999)

Department of ChemistryThe Hong Kong University of Science and Technology

Abstract

Sugars and polyols are broadly distributed in a wide range of living organisms.They can become airborne through biomass burning, cooking, soil re-suspension, windabrasion of vegetables, and bubble-bursting of sea water Their abundance and sources inthe ambient environments are little known because of a lack of suitable and simpleanalytical methods In this thesis work, I have explored and established analyticalmethods for the determination of total water-soluble monomeric carbohydrates (WSMC)and individual sugar and polyol compounds in aerosol samples Ambient fine aerosolscollected in Hong Kong, Nanjing, and Jeju Island (Korea) were determined for WSMC

concentrations and similar WSMC levels in the range of 228-640 ng/m” were found at

different locations The average water-soluble carbon mass percentage contribution by

XX

WSMC at different locations varied from 2.5% in the Nanjing samples to 7.6% in theHong Kong samples These results indicate that WSMCs are ubiquitous in the ambientenvironment and their contributions to water-soluble organic aerosol mass were notnegligible The application of a gas chromatography-based method for individual sugarsand polyols to cooking aerosols has allowed the assessment whether cooking is animportant source for glycerol and levoglucosan in the ambient environments It wasfound that cooking processes produce glycerol and levoglucosan, but comparison withambient aerosol measurements indicated that cooking was not a major source for thesetwo carbohydrate-like compounds in the ambient environment Two analytical methodsusing liquid chromatography-mass spectrometry (LC-MS) were successfully developed

in this thesis work and were found to be simple and most suitable for the determination of

various sugars and polyols in ambient aerosols The application of the LC-MS methods

to a set of thirty ambient aerosol samples collected in Hong Kong, in conjunction with themeasurements of the major aerosol constituents, has identified biomass burning andsoil/soil microbiota to be the major sources for ambient sugars and polyols Such afinding is also consistent with the total WSMC measurement results made for bulkaerosols and size-segregated aerosols Future work is suggested to focus on theapplication of the LC-MS methods on both the source aerosols (e.g., suspended soil dust,vegetative detritus, and sea salt aerosols) and the ambient aerosols The analysis of thesecompounds in the source aerosols will help to quantify the contributions of theses sources

to ambient aerosol loadings Their measurement in ambient aerosols will help tounderstand the role of sugars and polyols in enabling their host particles to serve as cloudcondensation nuclei

XXi

Chapter 1

Introduction

1 Introduction

1.1 The role of aerosols in the atmosphere

Since the industrial revolution, mankind has been releasing more and morechemicals into the atmosphere Many of these emitted compounds have negative andundesirable effects on human beings and ecosystems A relatively visible airpollution form in everyday life is smog, which manifest in the hazy sky and reducedvisibility The haziness is attributed to the presence of aerosols, i.e., solid or liquidparticles suspected in the air Aerosols have significant effects at various spatialscales ranging from local, regional to global [Seinfeld and Pandis, 1998]

The local effects of aerosols are mainly their health effects Inhaled particlesare deposited in the trachea and lungs and may cause pathological effects, decline inlung function and increases in respiratory symptoms Elevated levels of ambientparticulate matter have been associated with increase in mortality and hospitaladmissions due to respiratory and cardiovascular diseases [Brunekreff and Holgate,2002; Dockery et al., 1993; Pope et al., 1995] Short term exposure may triggerproblems such as heart failure in susceptible individuals [Peters et al., 2001] Effectssuch as constriction of the arteries even occur in healthy adults

The regional and global impacts of aerosols are rooted in their capability ofinteracting with sunlight and water in the atmosphere Aerosols have a direct impact

on the radiative balance by scattering incoming solar radiation and absorbing solarand thermal radiation A semi-direct effect by aerosols is that absorption of radiation

by the aerosols results in higher atmospheric temperatures causing evaporation andprevention of cloud formation [Hansen et al., 1997] In addition, the aerosols distortthe radiative balance indirectly by acting as cloud condensation nuclei, and thus alter

the cloud microphysics and the albedo of the earth [Kaufmamn et al., 2002; Twomey

et al., 1984] Quantity, size and composition of the aerosols all affect cloud dropletconcentration, optical properties and lifetime of clouds A lot of uncertainties exist inthe estimation of the direct, semi-direct and indirect effects of aerosols [IPCC, 2001].Chemical compositions of aerosols are essential information in quantifying thevarious effects of aerosols on the global climate

Aerosols also modulate atmospheric chemistry Being a medium scatteringand absorbing light, aerosols affect the amount of radiation and thereby photolysisrates of chemical species [He and Carmichael, 1999] In addition, aerosols provide acatalyzed surface for reactions that normally do not occur or are very slow in the gasphase In this way, aerosols act as a mediator for reactions to occur Aerosols alsoaffect atmospheric chemistry by transporting semi-volatile compounds, which may bereleased into the gas phase at a different location from their sources Finally, aerosolsplay an important role in cloud chemistry by affecting the pH of cloud water

1.2 Chemical composition of atmospheric aerosols

Aerosols have different sizes, shapes and chemical composition and arereleased from multiple emission sources [Raes et al., 2000] Their sizes range from afew nanometers (nm) to tens of micrometer (um) in diameter They are composed ofmany different compounds, the composition of which varies in time and space.Aerosol components can be grouped into carbonaceous, inorganic and crustal andmarine materials [Saxena & Hildemann, 1996] Figure 1.1 shows three examples ofPMio chemical composition The major constituents of ambient PM¡o were elementalcarbon (EC), organic carbon (OC), sea salt, sulfate, nitrate, ammonium, and crustal

species The major inorganic species (sulfate, nitrate and ammonium) accounted for

25 - 50% of the total PMio mass The sources and formation pathways for theinorganic species are well understood The production of sulfuric acid in theatmosphere occurs through gas-phase photo-oxidation of sulfur dioxide (SO2) withhydroxyl radicals in the gaseous phase and aqueous phase reactions of SO; withhydrogen peroxide (H;O;) [Seigneur and Saxena, 1984; Joos and Baltensprenger,1991; Pandis et al., 1990] Ammonium becomes part of aerosol when the diffusion ofammonia (NH3) occurs to neutralize of the sulfate aerosol particles [Sioutas andKoutrakis, 1996] Nitric acid is mainly formed through the photo-oxidation reactionbetween NO; and OH During night time, the reaction between NO; and O3 leads toformation of nitrogen peroxide (N2Os), which reacts with water vapor to formaqueous nitric acid Nitric acid is neutralized when it reacts with ammonia and formsparticulate ammonium nitrate Nitric acid can also react with salts of chloride orcarbonate and forms particulate salt solutions

A significant portion of mass (16 — 33%) was not identified This fractionmay contain a considerable amount of water associated with aerosol, as in the case ofPMio in Helsinki (5% of PMio mass) [Pakkanen et al., 1999] In Hong Kong,chemical speciation of PM2.5 measurements was conducted in different locations The

annual average PM2,5 mass concentrations ranged from 23.7 ug/m at a rural site (Hok

Tsui) to 58.1 j1g/m? at a roadside location, and are 1.5 4 times higher than the USEPA annual NAAQS of 15 ug/mỶ [Louie et al, 2005] The urban area loading is

the highest due to the vehicle emission and other combustion sources such as cooking

or vegetation burning Figure 1.2 shows the chemical composition of PM¿x; indifferent locations in winter season The organic matter concentrations were ~30% ofmass concentration while sulfate loading was 15 — 29% [Louie et al, 2005]

mMEC

moc

@Sea salt mso4 NO3

BINH4

Melements 26% OUD

PM10 = 7.8 ng/mŠ

(b) Voerde (Germany) - Rural

7%

EC HỌC

8 Sea salt mso4 NO3 B=NH4 Belements HUD

33% 17%

13%

9%

PM10 = 49.5 ug/mÊ

Figure 1.1 Overview of aerosol composition at several sites, including the

unidentified (UD) fraction Data were from (a) Pakkanen et al,

1999, (b) Kuhlbush et al, 2000, and (c) Rodriquez et al, 2002

(a) Mong Kok (roadside)

10% 1% 4%

16% eC

NO3 6% nSo©4

@ NH4 s8ỌC wEC mNa

12% BNH4

mỌCc mEC wNa

8 Other Element

Figure 1.2 Chemical composition of PM¿z in Hong Kong (a) Mong Kok

(roadside); (b) Tsuen Wan (urban); (c) Hok Tsui (rural)

Ambient PM contains two forms of carbon, elemental carbon (EC) andorganic carbon (OC) These carbonaceous species contribute a large fraction ofaerosol mass EC has a chemical structure similar to impure graphite and is emitted

as primary particles mainly during combustion processes such as wood-burning,diesel engines [EPA, 1996; Burtscher, 1992; Hansen and Lacis, 1990] Theconcentration of combustion sources in urban areas dictates that much higherconcentrations of EC are found in urban areas compared to rural and remote locations

The typical EC concentration is 5 20 ng/m? in remote ocean atmospheres [Clarke, 1989], 0.2 2.0 ug/m? in rural and remote locations [Clark et al., 1984; Pinnick et al., 1993] and 1.5 20 g/m? in urban areas [Heintzenberg and Winkler, 1984; Rau, 1989].

EC is a minor component of the carbonaceous aerosols The ratio of EC to totalcarbon ranges from 0.15 to 0.20 in rural area and from 0.2 to 0.6 in urban areas[Wolff et al., 1982; Chow et al., 1993]

The OC fraction of ambient PM is a complex mixture of thousands of different

organic compounds, of which only a small part (~10%) has been identified [Cass et al.,

1982; Turpin and Huntzicker, 1995; Grosjean, 1992; Odum et al., 1997; Pandis et al.,

1992] The characterization of the OC fraction is a challenging task due to a widerange of compounds present [Turpin et al., 2000] As a result, information available

on the organic fraction is far less complete in comparison with the inorganic fraction

In a detailed chemical characterization study using gas chromatography—massspectrometry (GC-MS), n-alkanes, n-alkanoic acid, aliphatic dicarboxylic acids,aromatic polycarboxylic acids, diterpenoid acids, polycyclic aromatic hydrocarbons(PAH), polycyclic aromatic ketones (PAK), polycyclic aromatic quinones (PAQ) andN-containing compound are identified and quantified to be constitutents of the fine

particles in West Los Angeles and Rubidoux [Rogge et al., 1993] The sum of

individual compounds in different compound groups ranged from a few ng/mỶ to a few hundreds ng/m? (Table 1.1) The three groups of acid compounds were among

the most abundant identified constituents Single compounds identified in this studyaccount for approximately 10% of total OC mass (Figure 1.3)

(a) Total Fine Particle Mass Organics Elutible Organics Resolvable Organics

24.5 ug/m3 7.8 ug/m3 3.7 ug/m3 910 ng/m3 100%

Others

Unidentified

: Organics

Now 880%- Anrnenium Eiractable nh

- Non-Elutable mer

Nitrate Organics Duerpenoid Acids | ~PAHS

Aromauc Unresoived Polycarboxylic

60% ~ Organics Acids

Sulfate

Aliphatic Dicarboxylic Acids

40%- Elemental

Carbon _R:AREnoK AC

Elutable Organics

20% +4 N-Alkanoic

N-Alkanes

(b) Total Fine Particle Mass Organics Elutable Organics Resolvable Organics

42.1 ug/m3 6.2 ug/m3 3.8 ug/m3 1070 ng/m3

100%¬

Others Non- Unidentified

earratt Organics 80% Extractable

0% NomElutable

Ammonium Unresolved Polyearboxylie Diterpenaid Acids

Sulfate Organics N-Alkenoic Acids

20%- Elemental N-AlkanoiCarbon Resolved tka oreAcids

Organics Organics

N-Alkanes

Figure 1.3 Mass balance on the chemical composition of annual mean fine

concentrations, 1982, for (a) West Los Angeles and (b) Rubidoux

(Riverside) from Rogge et al., 1993

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It is noted that most often chemical speciation of OC is performed on afraction that extracts in relatively nonpolar organic solvents such as benzene, ether,hexane, or dichloromethane [Abas et al., 1995; Elias et al., 1999; Oros and Simoneit,1999; Simoneit el al., 1999, 2000; Simoneit and Elias, 2000, Fang et al., 1999] Thenonpolar organic solvent extractable mass typically accounts for only 50-60% of thetotal organic aerosol [Cass, 1998] In addition, GC-MS methods are commonly usedfor the determination of organic compounds and the nature of this analytical approachlimits the type of measurable analytes to non-polar or semi-polar compounds As aresult, the more polar and potentially water-soluble organic compounds (WSOCs) areleft unanalyzed and remain poorly characterized Little has been done to ascertain thechemical nature of this class of compounds.

On the other hand, the affinity of WSOCs for water renders the WSOCsplaying a special role in the interaction between aerosol and water For example, theycould influence the ability of an aerosol particle to act as cloud condensation nuclei(CCN) [Novakov and Penner, 1993; Novakov and Corrigan, 1996; Facchini et al.,1999] The molecular composition knowledge of water-soluble organic componentswill improve our understanding of contribution of organic carbon to CCN activity Inaddition, the chemical composition may provide hints on the origins of the fineaerosols, since certain compounds are characteristic of specific sources Origins must

be identified in order to attribute forcing to anthropogenic and natural causes Thechemical composition of water-soluble organic fraction is also important inunderstanding wet scavenging of atmospheric particles, their impact on human healthupon inhalation, and their role in the formation of haze

WSOCs constitute a significant fraction of OC Studies encompassing bothurban and rural locations have reported that WSOCs constitute approximately 20% to

11

67% of the total particulate carbon in the atmosphere [Sempere and Kawamura, 1994;Mueller et al., 1982; Zappoli, et al., 1999; Mader et al., 2004] The scarcity ofinformation on WSOCs stems from the fact that analytical methods commonly usedfor aerosol chemical analysis are not aimed at characterizing this fraction.

Observations regarding the molecular composition of the water-solubleorganic fraction are limited [Andreae et al., 1998; Narukawa et al., 1999; Yamasoe etal., 2000] Available studies on characterizing WSOCs have mainly aimed at organicanions, dicarboxylic acids, keto acids and dicarbonyls Kawamura and his colleagues,for example, have studied water-soluble organics including a,w-dicarboxylic acids(Cz-Ca), œ-oxo-carboxylic acids (C;-Cs), pyruvic acid, and œ-dicarbonyls (C2-C3) inurban aerosols as well as Antarctic and Arctic aerosols [Sempere and Kawamura,1994; Kawamura et al, 1996a, b] They employed a water extraction and analyzed theabove chemicals as their dibutyl ester using GC-MS For urban aerosols collected inTokyo, the above compound classes accounted for only 5-17% of the total water-soluble organic carbon For the Antarctic and Arctic aerosols, no measurement wascarried out on the total WSOC fraction Li and Winchester [1993] measured eightwater-soluble organic anions formate, acetate, oxalate, propionate, methanesulfonate,lactate, benzoate, and pyruvate in Arctic aerosols using ion chromatography (IC) In

a later study, Li et al [1996] measured a selected number of WSOCs includingglyoxylic acid, and five of the above organic anions (formate, acetate, propionate,oxalate, and methanesulfonate) in aerosol samples collected near the coast ofSouthern Nova Scotia, Canada The total WSOC mass was not determined in eitherstudy, therefore it is unknown how much organic anions and glyoxylic acid contribute

to the total WSOC fraction

12

Additional candidate WSOCs have been identified by Saxena and Hildemann[1996] on the basis of their solubility, condensibility, and atmospheric occurrence.They include polyols (C2-C7), amino acids (C2-C7), hydroxyl amines (C2-C7), andsome miscellaneous multifunctional compounds containing multiple hydroxy,carboxyl, and carbonyl groups (e.g glyceraldehyde, malic acid, citric acid, lactic acid,tartaric acid, and a-ketoglutaric acid) The limited number of studies aiming atWSOCs have merely identified a small fraction [e.g Sempere and Kawamura, 1994;Yang et al., 2005] Therefore, there is a need for developing suitable analyticalmethods for the remaining unidentified fraction.

Among possible WSOCs, sugars, anhydro-sugars, and polyols meritconsideration as aerosol components As major organic constituents of organism,they are ubiquitous in the environment The multiple number of polar functionalgroups in each molecule results in high water solubility for this class of compounds.Considering the above two factors, these compounds are probable contributors towater-soluble organic carbon in aerosol One anhydro-sugar compound, levoglucosan,

a known chemical present in biomass burning emissions, has long been established as

an aerosol constituent Sugars and polyols, however, have been rarely studied inatmospheric samples, due to a lack of analytical methods to measure them at thelevels existing in aerosols [Mochida et al., 2003] Only a very limited number studieshave reported their occurrence in atmospheric samples [e.g., Likens et al., 1983,Simoneit et al., 2004; Wang et al., 2005] In this thesis, I focus primarily ondevelopment and application of analytical methods for sugars, anhydrosugars, andpolyols in ambient and source aerosols

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Chapter 2 Literature Review

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2.1 Chemical substances in water-soluble carbohydrate-like compounds

For the convenience of ensuing discussion, the three classes of compounds,sugars, anhydrosugars, and polyols, are given a collective name of carbohydrate-likecompounds Table 2.1 shows the structure and molecular weight of the targetcarbohydrate-like compounds in this work These compounds contain three or morehydroxyl groups As a result, they have a high solubility in water at ambient

temperatures.

2.2 Sources of carbohydrate-like compounds in the atmosphere

Carbohydrates are the most abundant organic constituents of plants They arebroadly distributed in a wide range of tissues including micro-organisms and animals.How they enter the atmospheric compartment is largely undefined A number ofmechanisms are possible

(1) Burning of biomass could release these compounds from their parentbiological material into the atmosphere This source of biogenic organic matter to thetroposphere occurs by natural, as well as man-made fires Chemical reactions, such asoxidation, depolymerization, dehydration and decarboxylation, may occur in theburning process, leading to products having partial carbohydrate characteristic[Shafizadeh et al., 1984; Hornig et al 1985] The heat generated during the burningprocess provides the energy to gasify the wood substrate A prominent example islevoglucosan (1,6-anhydro-B-D-glucopyranose), a dehydrated glucose Levoglucosan

is produced during pyrolysis of cellulose, which is a long-chain linear polymer made

up of 700-12000 D-glucose monomers [Tanner and Loewus, 1982] Levoglucosan is

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abundant in fine biomass burning aerosols [Shafizadeh, 1984; Simoneit et al., 1999;Simoneit and Elias, 2001] Figure 2.1 shows the formation mechanism oflevoglucosan in the pyrolysis of cellulose Combustion of fossil fuels orbiodegradation and hydrolysis of cellulose do not produce levoglucosan [Elias et al.,2001] As a result, levoglucosan is typically used as a marker to indicate the presence

of biomass burning [Simoneit et al, 1993; 1999; 2002; 2004]

In addition to levoglucosan, other sugar compounds could also be releasedfrom wood burning Hemicelluloses, the other major polysaccharide biopolymers ofwood, are a mixture of polysaccharides derived from 100-200 monomers of glucose,mannose, galactose, xylose and galacturonic acid [Parham and Gray, 1984] Theirsugar monomer composition varies widely among different tree species The sugarmonomers could be released when hemicelluloses broken down during burning

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Table 2.1 Structural information on those target compounds

Analytes CAS No MW Class Structure

OHGlycerol 56-81-5 92.09 Polyols

OHOH

-HO OH

OH

H

O OHGlucose 50-99-7 180.16 Monosaccharide

HO OH

OH

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Analytes CAS No MW Class Structure

O OH

OH Fructose 7660-25-5 180.16 Monosaccharide

HO OH

OH

OH

© 9 Levoglucosan 498-07-7 162.14 Anhydro-sugar

OHOH

OH

HO Q OHHO

Sucrose 57-50-1 342.3 Disaccharide HO DƯ VO OH

OH OH

H

OQ oO OHHO

18 OH