ABSTRACT

INVESTIGATION OF THE SOURCES OF HYDROGEN PEROXIDE IN AMBIENT PARTICULATE MATTER

Reactive oxygen species (ROS) are oxygen centered free radicals and their metabolites, including hydroxyl (OH), hydroperoxyl (HO2), hydrogen peroxide .- (H2O2), and the superoxide radical anion (O2 ). ROS may affect the chemical composition of the atmosphere by aerosol aging.Redox active species such as transition metals and quinone compounds may be important sources of ROS that are produced by redox cycling. The goal of this project is to quantify ROS

(specifically H2O2) generation by particles as well as to elucidate the components in particles that are responsible for ROS generation. Particulate matter samples were collected in Claremont and Fresno during 2012 and 2013.Sections of these filters were extracted into dilute acid solutions, and high performance liquid chromatography (HPLC) was used to quantify ROS generated by samples. The data indicate that Fresno samples and Claremont samples generate similar quantities of ROS, and that quinones and free transition metal ions cannot account for the generation of ROS by the particulate matter filter samples. The formation of ROS might be due to the presence of organic soluble, non-polar compounds present within the particles.

Sowmya Keerthi Tummala May 2015

INVESTIGATION OF THE SOURCES OF HYDROGEN PEROXIDE IN AMBIENT PARTICULATE MATTER

by Sowmya Keerthi Tummala

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Chemistry in the College of Science and Mathematics California State University, Fresno May 2015 APPROVED For the Department of Chemistry

We, the undersigned, certify that the thesis of the following student meets the required standards of scholarship, format, and style of the university and the student's graduate degree program for the awarding of the master's degree.

Sowmya Keerthi Tummala Thesis Author

Alam S. Hasson (Chair) Chemistry

Jai-Pil Choi Chemistry

Laurent Dejean Chemistry

For the University Graduate Committee:

Dean, Division of Graduate Studies AUTHORIZATION FOR REPRODUCTION OF MASTER’S THESIS

X I grant permission for the reproduction of this thesis in part or in its entirety without further authorization from me, on the condition that the person or agency requesting reproduction absorbs the cost and provides proper acknowledgment of authorship.

Permission to reproduce this thesis in part or in its entirety must be obtained from me.

Signature of thesis author: ACKNOWLEDGMENTS I would like to express my sincere gratitude to my thesis advisor Dr. Alam S. Hasson, who gave me the opportunity to conduct my study in his Research group. Words are not sufficient to describe the sincere appreciation for your guidance and the endless support. Thank you to my committee members, Dr. Jai- Pil Choi and Dr. Laurent Dejean, for the feedback and support. To the Department of Chemistry staff, Rosalina Messer, Doug Kliewer, and Alan Preston, thanks for the work behind the scenes. I would like to extend a special appreciation to The Hasson Atmospheric Lab; I have made lifelong friends throughout the time. A special thanks to my family. Words cannot express how grateful I am to, my mother, my father, and my sister for all the support and the sacrifices that you have made. Your prayers for me was what sustained me so far. I would also like to thank all my friends who supported me in every aspect to strive towards my goal. TABLE OF CONTENTS Page

LIST OF TABLES ...... vii

LIST OF FIGURES ...... viii

INTRODUCTION ...... 1

Air Pollution ...... 1

Particulate Matter ...... 4

Reactive Oxygen Species (ROS) ...... 9

Measurements of Peroxides ...... 12

Research Objectives ...... 20

EXPERIMENTAL ...... 22

General Research Design ...... 22

Sampling Locations ...... 22

Sample Collection ...... 23

Extraction Methods ...... 25

Extraction Solution Preparation ...... 25

Preparation of Fluorescent Reagent ...... 26

Solid Phase Extraction (SPE) ...... 26

Instrumentation ...... 28

Calibration of HPLC ...... 30

RESULTS ...... 36

Hydrogen Peroxide Calibration ...... 36

Production Rates of H2O2 for the Trial Filters ...... 37

Production Rates of H2O2 for Fresno Samples: Fresno Filter 11 ...... 40

DISCUSSION ...... 49 vi vi Page

Ambient Mass Loadings ...... 49

Parallel Studies ...... 53

Role of Quinones and Metals ...... 55

Back Trajectories ...... 60

CONCLUSION ...... 66

Future Work ...... 67

REFERENCES ...... 68

LIST OF TABLES

4 Table 1. National Ambient Air Quality Standards for Criteria Pollutants ...... 3

Table 2. H2O2 Calibration Data for Different Lab Suppliers...... 37

Table 3. Collection Details of Fresno Filters ...... 44

Table 4. Collection Data for Claremont Filters ...... 46 Table 5. Statistical Data for Correlation Between PM 2.5 Mass Loadings and H2O2 Formation ...... 55

Table 6. Statistical Data for the Correlation Between H2O2 Formation and Specific Quinones ...... 56

LIST OF FIGURES

Page

8 Figure 1. Aerosol size distribution ...... 5 51 Figure 2. Quinone redox cycle reactions ...... 18 Figure 3. Regional overview of air quality sampling location sites at 61 Claremont[A], CA and Fresno[B], CA...... 23 65 Figure 4. Tisch Environmental TE-6070 hi-volume PM2.5 sampler ...... 24 Figure 5. High Performance Liquid Chromatography with post-column 63 derivation and fluorescence detection instrument...... 29

Figure 6. Calibration curve of H2O2 for Macron, Fischer and Sigma-Aldrich ..... 36

Figure 7. Production rates of H2O2 per hour for the trial filters ...... 38

Figure 8. H2O2 Production rates under variable conditions for Fs-02 ...... 38

Figure 9. Differences in the production of H2O2 under variable conditions for Fresno filters 1 and 2...... 40

Figure 10. Production rates of H2O2 under variable conditions for Fs-11 ...... 41

Figure 11. Rate of formation of H2O2 for Fresno samples grouped into morning, afternoon, and overnight samples ...... 43

Figure 12. Average production rates of H2O2 for the filters collected from 16 to 19 January 2013 ...... 43

Figure 13. Rate of formation of H2O2 for Claremont filters ...... 45

Figure 14. Rate of formation of H2O2 for aqueous, organic and residual filter extracts for specific Fresno samples ...... 47

Figure 15. H2O2 variations for aqueous, organic, and residual filter extract for specific Fresno samples ...... 48

Figure 16. Variation between Fresno and Claremont samples ...... 49

Figure 17. Temporal variations of H2O2 formation rates for specific Fresno samples ...... 51

Figure 18. Temporal variation of mass loadings for Claremont filters ...... 51 Figure 19. Correlation between PM Particle mass and H O mass loadings 3 2.5 2 2 in (µg/m ) for Fresno filters ...... 54 ix ix Page

Figure 20. Correlation between PM mass loadings and H O mass loadings in 3 2 2 (µg/m ) for Claremont filters...... 54 Figure 21. Correlation between H2O2 against anthraquinone and phenanthraquinone ...... 57 Figure 22. Correlation between the average copper concentration and rate of formation of H2O2 for Fresno samples ...... 59

Figure 23. Correlation between H2O2 production rates and average copper mass loadings for Claremont samples ...... 59 Figure 24. Backward trajectory of airmass for Fresno samples with higher production rates of H2O2 ...... 62 Figure 25. Backward trajectory of airmass for Fresno samples with lower production rates of H2O2 ...... 63 Figure 26. Backward trajectory of airmass for Claremont samples with higher H2O2 formation rates ...... 64

Figure 27. Back trajectory of airmass for Claremont samples with lower H2O2 formation rates ...... 65

INTRODUCTION

Reactive oxygen species (ROS) are oxygen centered free radicals with strong oxidative capacity. ROS along with their metabolites have both 1,2 environmental and health effects . Hydrogen peroxide (H2O2), an ROS play an important role in aqueous phase photochemical reactions that occurs in atmospheric water drops. Furthermore, ROS may affect the chemical composition of the atmosphere by aerosol aging and also through the oxidation of organic and inorganic species within the particles2. Redox-active species such as quinones and transition metals are observed to be the major factors of particulate matter and are involved in particle bound ROS formation. This study will quantify ROS generation as well as elucidate the components in particles that are responsible for ROS generation by particles.

Air Pollution Suspension of dust along with the gas in the air, the emission of pollutants from fuel combustion, industrial processes, rock debris, and non-industrial fugitive sources contribute to the lethal effects on the environment. Air pollution is more characterized by the release of nitrogen oxides (NOx), particulate matter (PM) and volatile organic compounds (VOCs), which undergo photochemical reactions in sunlight to form more toxic products such as ozone2. High concentrations of pollutants in the atmosphere have deleterious effects on humans and environment. To prevent pollution from increasing and to protect public health from diverse array of pollution sources, the clean air act (CAA) imposed federal regulations of certain pollutants.3,4 2 2 The Clean Air Act The CAA was the first modern environmental law enacted by the U.S. Congress in 1970 and major amendments were made in 1977 and 1990. CAA imposed federal regulations on some pollutants called criteria pollutants. The environmental protection agency3 was formed to implement the law, set standards and monitor pollutant levels in the presence of sunlight and hydrocarbons. National Ambient Air Quality Standards (NAAQS)4 monitored six pollutants which include ozone, nitrogen oxides (NO x), particulate matter (PM), Volatile organic compounds (VOCs),sulfur oxides (SO x), Lead (Pb). Of these criteria air pollutants, particulate matter is one of the pollutants that pose the greatest threat to human health. These chemical emissions are able to react in the atmosphere to form more toxic products in the atmosphere. These criteria air pollutants’ sources are listed in Table 1.

Primary and Secondary Pollutants Air pollutants are classified into primary and secondary pollutants by their formation and entry into the atmosphere. Primary pollutants are directly emitted into the atmosphere either through natural or anthropogenic sources. Secondary pollutants are formed in the atmosphere when chemical reactions produce low volatility species that condense on to preexisting particles or nucleate new particles. Secondary particles may also be more hazardous than the chemicals that are emitted directly (Sulfuric acid, VOCs)2,8. Atmospheric conditions, geographic conditions affect the relative importance of primary and secondary pollutants.

3 3

Table 1. National Ambient Air Quality Standards for Criteria Pollutants4

Primary/ Averaging Federal Pollutant Secondary Major sources time standard Carbon Primary Motor vehicle exhaust 8-h 9 ppm monoxide (CO) 1-h 35 ppm Lead (pb) Primary/ Fuels in on-road motor 3-month 0.15 µg.m- Secondary vehicles and industrial 3 sources Nitrogen Primary Motor vehicle exhaust 1-h 100 ppb Dioxide (NO2) Primary/ Annual 53 ppb Secondary Ozone (O3) Primary/ Chemical reactions 8-h 0.075 ppm Secondary between oxides of Nitrogen (NOx) and volatile organic compounds in the presence of sunlight Particulate Primary Direct emissions from Annual 12 µg.m-3 Matter(PM) incomplete combustion, -3 PM 2.5a Secondary fire/wood burning and Annual 15 µg.m industrial emissions -3 Primary/ 24-h 35 µg.m Secondary Primary/ 24-h 150 µg.m- PM 10b Secondary 3 Sulfur Primary Unpaved road and 1-h 75 ppb Dioxide agricultural dust (SO2) Secondary Combustion of sulfur 3-h 0.5 ppm containing fuels a b Particulate matter with Da < 2.5 µm. Particulate matter with Da > 2.5 µm 4 4 Particulate Matter Atmospheric aerosol is often described in terms of particle size distribution, nature of origin, and chemical composition. A dramatic increase in atmospheric aerosols is observed during the last two centuries, which may be due to due to the industrialization and rapid growth in the world’s population. High levels of ambient PM have been linked to adverse health effects, affect global climate, and lead to visibility reduction.5 Many approaches have been made to measure, characterize, and model atmospheric aerosols during the last few decades.6, 7 PM is present as tiny particles of floating debris in the air we breathe and the particle size ranges from 0.002 µm to 100 µm. PM arises from natural sources such as windborne dust, volcanoes, and also from anthropogenic activities such as combustion of fuels. PM can be categorized in terms of aerodynamic diameter8 into fine, ultrafine, and coarse particles. As all the particles are not perfectly smooth spheres with uniform densities, aerodynamic diameter, Da specifies the size, shape, density, and velocity of the particle classified. Aerodynamic diameter is defined as the diameter of a sphere with unit density that retains the same terminal speed in air8. Coarse particles have an aerodynamic diameter of 2.5-10

µm and are commonly referred to as PM10. Fine particulate matter (PM2.5), has an aerodynamic diameter range of 0.1-2.5 µm, while ultrafine particulate matter has an aerodynamic diameter less than 0.01 µm. Lifetimes of emitted pollutants are dependent on their classification to size and also on the mode of formation. Particle growth9 determines the fate and transport processes in the atmosphere. Four distinctive modes of particle formation and their respective particle sizes are listed in Figure 1. 5 5

Figure 1. Aerosol size distribution8

Formation and Growth of Particulate Matter PM in the atmosphere is formed by condensation, nucleation or coagulation mechanisms.8,9 The path through which the particles are formed depends on the ambient temperature, vapor pressure, humidity, concentration, and particle size. The formation of fine particulate matter can be categorized into Aitken or transient nuclei (0.01µm-0.08µm) and fine accumulation (0.08-1-2µm), which have an atmospheric life time of a few days to weeks and can be transported up to a few thousand kilometers. Primary emissions produce particles of 0.01µm- 0.08µm where hot vapors from sources such as incomplete combustion fuel from diesel exhaust and the oxidized organic compounds are released. Thus, the 6 6 particles that are condensed to form fresh particles are largely lost by coagulation with larger atmospheric particles. The accumulation mode extends the formation of fine PM up to a diameter of 2.5µm by coagulation and condensation of vapors on to existing particles causing them to grow in size. Figure 1 represents the aerosol size distribution and particle formation mechanisms in atmosphere. Ultra fine particles have atmospheric life time of few hours and can be transported up to few tens of kilometers. Combustion sources and new particle production from low volatile gaseous compounds are major sources of ultrafine particles. Ultra fine particles are removed from the atmosphere by coagulation, particle growth, and deposition processes2. On mass concentration basis, ultrafine particles contribute to only a small fraction of atmospheric PM. Organic matter, which is a major component of tropospheric aerosol, constitutes about 10 to 70% of the fine particulate matter.13 Ambient aerosols containing organic matter play an important role in the atmosphere by acting as cloud condensation nuclei (CCN), which are further activated to form cloud condensation nuclei and are known to alter the cloud properties. Organic aerosols undergo several changes in the atmosphere through various mechanisms, which include aging, condensation of soluble inorganic and oxidized organic species (OOA), condensed phase chemistry, and heterogeneous oxidation of volatile organic compounds (VOCs) by O3, OH and NO3, followed by the conversion of the oxidized gaseous products to particles. Aging processes and oxidation of organic compounds enhance the water solubility and increase the number of polar functional groups of organic aerosol, which makes them active as cloud condensation nuclei.14,15 7 7

Recent work14 has shown that the majority of the organic particulate matter emitted from various anthropogenic and combustion sources are evaporated after their emission. The resultant semi-volatile organic vapors can react in the gas- phase with atmospheric oxidants, hydroxyl radicals, and OH to form low volatility oxidation products. The low volatility oxidation products can recondense to the particle phase within a time span of several hours to days. This evaporation, reaction, and condensation process leads to the formation of highly oxygenated organic aerosol that has significant effect on the physical properties, chemical properties, and chemical nature of organic aerosol. The low volatility organic compounds exist in particle phase in distinctive atmospheric concentrations. Organic aerosols evolve by becoming highly oxidized, more hygroscopic, and less volatile compounds, which finally lead to the formation of oxygenated organic aerosols (OOA). Previous studies16 from various locations identified that the major content of organic aerosol is constituted of oxygenated organic aerosol which is characterized with high oxygen content and high oxidation state. The increased levels of oxidized organic aerosols are strongly correlated with photochemical activity.17,18 Oxidized organic aerosol formation occurs mainly through the condensation of less volatile compounds on to the accumulation mode particles.15 Field and laboratory data from previous studies15 have observed that oxidation state and volatility of organics can be used to identify the evolution of organic aerosols. Low volatile (LV-OOA), highly oxidized organic aerosols are strongly correlated with non-volatile species such as sulfates and semi-volatile oxidized organic aerosols (SV-OOA) and are strongly correlated with semi- volatile species such as ammonium chloride, which are less photo chemically aged 8 8 aerosols.19,20 The relative concentrations of these aerosols are dependent on the photochemistry and temperature in the atmosphere.15

Aging of Aerosols Organic aerosol particles undergo various chemical reactions by interacting with inorganic ions, clouds, or water vapor and change the physical structure of aerosol. The chemical aging of organic aerosols alter the chemical composition of the particles forming more water soluble and hygroscopic compounds. A review on the chemical processing of organic aerosols has been done in previous studies.10,11 Aldehydes are detected to be the major volatile products in reaction of ozone with aerosol that has a fatty acid component. Previous studies also proved that ozonolysis of long chain unsaturated carboxylic acids lead to smaller molecules with higher hygroscopicity, which can either stay in aerosol-phase or escape in to the atmosphere.10-13 Hydrolysis, nitration, and oxidation of solid organics allow the hydrocarbons to escape from the aerosol-phase by volatilization. The condensation reactions and oligo or polymerization reactions initiated by radicals or acid catalyzed heterogenous reactions of aldehydes increases the aerosol mass and thus decreases the volatility of organic aerosol components and promote the formation of secondary organic aerosol particulate matter.12

Chemical Composition of PM Particles emitted or formed in the atmosphere undergo changes in their size and composition by coagulation with other particles, condensation or evaporation of volatile species, absorption of water in high relative humidity conditions and activation into fog or cloud droplets before removed through wet or dry deposition 9 9 processes. Collective properties of atmospheric aerosol such as mass and number concentration, radiative and optical properties can be determined form the emission sources and their subsequent transformation mechanisms. Particles in the coarse particle range are produced mechanically through crushing or attrition of larger particles and derived from suspensions or re- suspension of dust, sea salt, volcanic eruptions, and biomass burning. These large particles settle out of the atmosphere by sedimentation or by wet deposition via cloud drops. Coarse particles have atmospheric lifetime of few hours and are transported over tens of kilometers before they are removed through wet or dry deposition. These large particles settle out of the atmosphere by sedimentation or by wet deposition via cloud drops.2,8

Reactive Oxygen Species (ROS) PM plays an important role in the formation of reactive oxygen species. Several chemical species like transition metals and organic compounds, such as quinones, are known to be involved in the event of particle bound ROS formation. •‾ H2O2 can be produced via redox cycling between HO2/O2 radical and transition metals, which in ambient particles and cloud drops may be complexed by organics.23-25,46,57 ROS are oxygen centered free radicals and their metabolites which are derived from molecular oxygen (O2). ROS include hydroxyl (OH), hydro peroxyl • (HO2), organic peroxyl radical (RO 2), and anions such as superoxide radical anion •- (O2 ). ROS in aerosols may lead to aging of aerosol, which is the oxidation of organic and inorganic species within particles. Hydrogen peroxide and its related ROS have been identified as a key source to the aqueous phase reactions that take 10 10 place in water suspended in the atmosphere and are central to cloud processing of air.8

Formation and Loss of Gas-Phase Hydroperoxides

Gaseous hydrogen peroxide (H2O2) and organic hydroperoxides (ROOH) are unstable compounds that are decomposed to oxygen in the atmosphere and also act as a sink and source for radicals.25 Additionally, hydroperoxides are efficient in the aqueous oxidation of S (IV) complexes to sulfuric acid (H2SO4) in the troposphere that affects the geographical and temporal patterns of sulfuric acid deposition. H2SO4 plays an important role in the formation of new particles in atmosphere by nucleation.26 Highly oxidized poly carboxylic acids make stronger hydrogen bonds with H2SO4 to form stable molecular clusters that lead to the 26 formation of new particles in the atmosphere. Of the hydroperoxides, H2O2 is dominant, representing 60-90% of total hyroperoxides; the remaining 10-30% are organic hydroperoxides.27,28 Formation of gas-phase hydroperoxides is dependent on factors such as temperature, solar radiation, and water vapor. Also, it is dependent on NOx and higher concentrations of VOCs. Gas-phase and aerosol- phase hydrogen peroxides are formed in the atmosphere via three routes.29-34 The major route through which hydrogen peroxide is produced is through • the self coupling of hydroperoxyl radicals (HO 2) (R1), and with other alkoxy radicals (R2). The reaction of peroxy radical with alkoxy radicals have been shown to proceed by H-atom abstraction to form the hydrogen peroxide with a yield of unity.2,29 • • HO2 +HO2 H2O2+O2 (R1) • • • RO2 +HO2 ROOH +O2 (R2) 11 11

The source of HO2 is primarily from the photolysis of ozone (O3) forming singlet oxygen, O(1D) (R3),which can react with water to form hydroxyl radicals (OH•). Hydroxyl radicals (R4) can further react with carbon monoxide in the presence of O2 to form HO2 and CO2 (R5). 1 O3+ hv (λ >320nm) O ( D) +O2 (R3) 1 • O ( D) + H2O 2OH (R4) • • OH + CO (+O2) HO2 +CO2 (R5) Alkanes react with OH• (R6) to form an alkyl radical, which in turn reacts with O2 (R7) to form a peroxy radical. The peroxyl radical reacts with NO (R8) to produce an alkoxy radical and nitrogen dioxide (NO2). Alkoxy radicals are formed in the atmosphere by the degradation of volatile organic compounds (VOCs) in the presence of nitrogen monoxide (NO).The alkoxy radicals proceed through a number of pathways to form stable radical products and generate low volatility oxygenated species in the condensed phase. • • RH + OH R +H2O (R6) • • R + O2 RO2 (R7) • • RO2 + NO RO + NO2 (R8) Criegee intermediates, which are a product of alkene ozonolysis(R9), react with water vapor (R10) and form hydroperoxides; this is another major route for the formation of H2O2. The yield of H2O2 depends on the concentration of water vapor in alkene ozonolysis.31,32

CH2=CH2+O3 CH2COO+R2CO (R9)

RCHOO +H2O RCHO + H2O2 (R10) • The hydro peroxyl radical (HO2 ) has been considered to be the predominant source of hydrogen peroxide in atmospheric water drops.33,34 Atmospheric water vapor absorbs solar ultraviolet radiation and initiates the 12 12 aqueous phase photochemical reactions in ambient cloud and fog water. The photochemical reaction of organic chromatophores present in cloud water leads to the formation of free radicals and oxidants.25 Photolysis of Fe (III)-oxalate complexes is the source for photoformation of

H2O2 in atmospheric water drops. Fe (III)-organic complexes on photolysis form • - Fe (II) and organic radicals. Fe (II) and some organic radicals reduce O2 to O2 and forms H2O2. Photolysis of Fe (III) with other polycarboxylate complexes such 35,36 as citrate and malonate is also suggested to be a major source of H2O2. Gaseous phase formation of hydroperoxides is not only dependent on NOx,

CO, CH4 and non-methane hydrocarbons but is also dependent on other factors such as high concentrations of volatile organic compounds that enhance the formation of peroxide. It has been found that when NO levels exceed 100 ppt, 66 measurable H2O2 suppression occurs . An environment with high volatile organic carbons (VOCs):NOx ratio, along with carbon monoxide (CO), will tend to enhance peroxide formation due to the availability of radicals, whereas at a low VOC:NOx ratio, peroxide generation is suppressed due to the radical scavenging.

Measurements of Peroxides

Gaseous-Phase Measurements Numerous measurements of gas-phase peroxides have been done at various 28-30,36,37,45 locations. Primary measurements of H2O2 along with organic peroxides have been measured since the 1990s. H2O2 is the dominant peroxide with 0.1- 10ppb with levels typically being 1ppb. Field measurements of gas-phase hydrogen peroxide indicate its presence in the troposphere at concentrations less than 10 ppb by volume. Gas-phase H2O2 was found to be in the range of 0.5-3.5 ppbv from the most recent measurements at UCLA.30 13 13 Aerosol Measurements Only a few studies have been successful in quantifying aerosol-phase hydrogen peroxide due to the difficulty associated with these measurements.

Limited measurements of particle phase H2O2 have demonstrated high levels of

H2O2 associated with ambient fine-mode aerosols. First field measurements done by Hewitt and Kok2 indicated atmospheric aerosol-phase hydrogen peroxide concentration in the range of 0.01 to 10ng m-3.The reported values may be uncertain due to the poor chromatographic separations of hydrogen peroxide, and because of the possible formation of artifacts resulting from reaction of ozone and hydrocarbons in the filter during sampling. Field study of aerosol-phase ROS reported mass loading as high as 63ng m-3. Past studies by Hung and Wang36 indicated that the concentrations of ROS were affected by the intensity of the -3 photochemical reactions and reported the H2O2 concentrations of 21ng m . Measurements of aerosol-phase hydrogen peroxide levels at UCLA were in -3 the range of 0.01-13ng m . Based on the mass loading of aerosol-phase H2O2 and water in the aerosol, it was concluded that the concentration of H2O2 within these aerosols was of the order of 10-3M. 30Also, recent studies by Venkatachari et al. reported an average of 243ng m-3 aerosol-phase ROS concentrations in Rubidoux, CA.37 A strong seasonal variation was observed for studies of both gas-phase and aerosol-phase hydrogen peroxide measurements. Past studies also conclude that

H2O2 productions display variability with H2O2 levels higher in mid-to late afternoon, and lowest during the night and morning hours. Also, extensive studies indicate that H2O2 displays a strong seasonal variation, with highest levels of H2O2 in the spring and summer. Other factors that influence peroxide levels are meteorological parameters such as solar radiation, water vapor concentration, and temperature. Solar 14 14 radiation is required for radical formation and water vapor promotes radical reactions. High temperatures are known to favor peroxide production. Peroxides are the reservoirs of radicals where photolytic destruction will yield HO and to 33 some extent HO2 radicals. The OH radicals can take part in aqueous phase formaldehyde or formic acid oxidation. Gaseous formaldehyde undergoes dissolution into cloud droplets to form hydrated formaldehyde. The hydrated formaldehyde undergoes oxidation with OH to form CH (OH)2 radical (R11). The obtained CH (OH)2 reacts with O2 to form hydrated formic acid (HCOOH)(R12). Formic acid undergoes dissolution to form HCOO- ion (R13).38

CH2 (OH) 2+ OH CH (OH) 2+H2O (R11)

CH (OH) 2+ O2 HO2+HCOOH (R12) HCOOH H+ +HCOO (R13) • Photochemical reactions also lead to the formation of HO 2 from hydroperoxide associated compounds which are typically released into the 34 atmosphere during pollution. Reaction of alkoxy radicals with O2 (R14) and photolysis of formaldehyde (R15, R16) are the major sources of formation of HO2 during the daytime. • RCH2O + O2 RCHO + HO 2 (R14) HCHO + hv H• +HC•O (R15) • HC O + O2 HO2 + CO (R16)

Henry’s Law Numerous field studies have been done to show the presence of hydrogen peroxide and other organic peroxides. The distribution of H2O2 between the gas- phase and aerosol-phase is still under study. 15 15

Gas to water partitioning of H2O2 makes the peroxides enter into the aqueous portion of the aerosols. The partitioning depends on the nature of the species, which are either water soluble or water insoluble compounds. The uptake of water soluble compounds is determined by the Henry’s law constant of the species and its ability to dissociate in solution.41-43 So, hydroperoxides that are water soluble and partitioned between the gas- phase and liquid water is given by the Henry’s law coefficient.42 Hydrogen peroxide partitions strongly into the aqueous phase with a Henry’s law coefficient of 1.0 x 105 M.atm-1. Henry’s law is given as

Xa = Pa x Ha

Where, Ha is Henry’s law coefficient for species ‘a’. Xa is aqueous concentration for a species and Pa is partial pressure of species. This relation predicts that the aqueous concentration of hydrogen peroxide in liquid water is in 42 equilibrium with 1ppb of H2O2 that is equivalent to 0.1mM. Estimation of particle phase ROS content based on gas-phase ROS can be done using Henry’s law. Gas and particle-phase hydrogen peroxide were measured and compared to Henry’s law based predictions. The Henry’s law predictions for aqueous H2O2 levels are derived using measured gas-phase H2O2 multiplied with

Henry’s law coefficient of the species (Ha). Evidence from the previous studies showed that particle phase peroxide levels exceeded predictions by Henry’s law by a factor of about 300-700.41

Calculated concentrations of H2O2 for the aerosol liquid water are higher than

Henry’s law predictions, as the H2O2 dissociates rapidly between gas and liquid phases. The exceeded levels of particle phase peroxide in aerosol liquid water is thought to be due to the continuous production of peroxide in the extraction solution by the particles during the particle dissolution process.45,46 16 16 Possible Explanations for Observed Particle Phase H2O2 Aerosol hydroperoxide levels were observed to be at higher levels over gas- phase partitioning of Henry’s law after extracting them into weakly acidic aqueous solutions. Several sources responsible for elevated levels of H2O2 in aerosols are described below.

Dissolution of H2O2 associated with the particles is one of the major sources of H2O2. Measurements from UCLA indicated that the majority of H2O2 associated with ambient particles is generated by particles themselves, in aqueous solutions and the measured levels exceeded those predicted by Henry’s law by two orders of magnitude based on measured gas-phase H2O2 associated with ambient 45 mass and relative humidity. H2O2 concentrations tend to be lowered in cloud and fog waters from their Henry’s law equilibria due to the oxidation of S (IV) species 2 by H2O2. Recent studies proved that inorganic salts, especially ammonium sulfate and other salts in dissolved form, are known to enhance the solubility of H2O2 by a 25 factor of 2 to 3. Generation of H2O2 in cloud and fog water through photochemical reactions based on radical chemistry is also thought to be one of 34 the possibilities for H2O2 production. Hydrogen peroxide is also produced by the decomposition of aqueous hydroxyhydroperoxides along with corresponding aldehyde.39,40 Particles contain redox active species, including transition metals, such as iron or copper and organic compounds, such as quinones, which may be capable 36,37,47,49 of generating H2O2. The fraction of quinones that contributes to the H2O2 production depends on the availability of electron donors for redox cycling. 17 17 Redox Quinone Chemistry Quinones in particulate matter play an important role due to the redox chemistry that leads to ROS production24,30. The ability of these species to induce such an effect is based on their capacity to accept electrons from biological reductants and, in turn, donating the electrons to molecular oxygen (O2) to . generate a superoxide radical (O2 ).The catalytic intermediate in this process is a semiquinone radical anion species. Thus, quinones capable of participating in this redox chemistry must be good oxidants to accept an electron from biological reductants, and the corresponding semiquinone species must be good reductants to efficiently reduce O2.

Several studies proposed the presence of hydroquinone (QH2) in the 50-52 quinone-catalyzed redox cycle . QH2 undergoes auto oxidation with a quinone (Q) to form a semiquinone (Q•‾ ) intermediate (R17). The semiquinone •‾ intermediate reduces molecular oxygen to generate superoxide radical anion O2 (R18).

•‾ + QH2 +Q 2Q +2H (R17)

Q•‾ +O2 Q + O2•‾ (R18) •‾ •‾ • QH2 + O2 QH +HO2 (R19) •‾ • •‾ QH + HO2 Q + H2O2 (R20) •‾ •‾ + O2 + O2 +2H H2O2 +O2 (R21)

Spontaneous deprotonation of QH2 takes place when QH2 interacts with •‾ •‾ superoxide radical anionO2 (R19). The QH formed is oxidized to generate the semiquinone radical and hydrogen peroxide (R20). Superoxide radical anions •‾ generated in R18 can react with another O2 and two hydrogen ions to generate hydrogen peroxide (R21). Figure 2 represents the quinone redox cycling reactions that shows quinone-mediated H2O2 generation. 18 18

Figure 2. Quinone redox cycle reactions51

Redox Reactions of Transition Metals Metals have the potential to catalyze reactions. Previous chemical and in vitro studies reported in the literature have also shown the association between ROS generation and specific metals by determining the sources, concentrations of ROS and metals.46,47 A better correlation of ROS production with water soluble metals was observed, when compared to total metals which have been consistent 23,57,58 in all the previous studies. Total metals constitute to about 7-13% of PM2.5 whereas water-soluble metals account for about 1-5% of PM2.5. Evidence from the previous studies concluded that a number of water soluble transition metals may potentially lead to the generation of ROS. Iron and copper tend to be the most abundant transition metals found in aerosols in their dissolved and solid forms. Other elements including Ca, V, Pb, Na, Ni, K, Mg, Mn and Se were not 57-59 significantly correlated with H2O2, due to their low concentrations in particles.

One of the transition metals that has the capacity to generate H2O2 is copper

(Cu). Cu is known to efficiently convert HO2/OH radicals to H2O2 at a higher rate when compared to Fe (II). Cu (I) and Cu (II), which are thought to be present in 19 19 the atmospheric waters and particles, are involved in the following reactions (R22, - R23). In an aqueous solution, reaction of Cu (I) with O2 can lead to the formation of high OH/HO2 radical concentrations that result in continuous formation of

H2O2. - + HO2 + Cu (II) Cu (I) + O2 + H (R22) - + O2 +Cu (I) +2H Cu (II) +H2O2 (R23) A recent study by Charier et al. showed a good correlation between Cu and 57 formation of H2O2. Other studies by Chow et al. also reported average metal concentrations of 208ng.m-3 for 24 h in fine PM.58 Another study by Singhs59 reported an average of about 13ng.m-3 which is less than the previous study.58

Removal of Peroxides from Atmosphere Hydrogen peroxide and organic peroxides are removed from the atmosphere by photolysis, reaction with OH, physical decomposition to the ground, and by rain out. The photolysis of H2O2 leads to the regeneration of OH (R24) and the photolysis of organic peroxides (ROOH) leads to the formation of OH and alkoxy radicals (R25). Hydro peroxides can also be lost by reaction with OH radicals (R26 and R27) or by wet and dry deposition to the ground. Wet deposition leads to the major loss of hydrogen peroxide.2 • H2O2 + hv 2 OH (R24) ROOH + hv RO• +.OH (R25) • OH+H2O2 H2O +HO 2 (R26) • • OH +ROOH RO 2 +H2O (R27) 20 20 Research Objectives

Quantification of H2O2 in particle phase was studied. The correlation between the particle composition and formation of H2O2 was identified (specifically for quinones and transition metals). Also, the particle sources that are involved in the formation of H2O2 was also observed.

Measurements The primary objective of this work is to quantify the hydrogen peroxide concentrations present in the PM2.5 filter samples, which are extracted into the aqueous phase. The measurements made will quantify as well as identify the source of hydrogen peroxide which will be compared with quinones and transition metals measurements made at California State University, Fresno and UC Davis to understand their role in ROS generation. The work presented in this thesis will contribute to the overall objective of this study. The research questions that were addressed through this study include the following: 1. What are the rates of formation of hydrogen peroxide in the particle phase samples collected in Claremont and Fresno? 2. What are the temporal variations observed in between morning, afternoon and overnight samples for specific Fresno and Claremont samples?

3. Are PM2.5 mass loadings responsible for H2O2 formation?

4. Are transition metals involved in the formation of H2O2?

5. Are quinones involved in the formation of H2O2?

6. Where are the air masses that are responsible for formation of H2O2 coming from?

This study reports the average mass loadings of H2O2 and also gives a brief idea of the sources of ROS and thus the role of quinones and metals in the 21 21 formation of H2O2. Also, the effect of diurnal and seasonal variations on the production of H2O2 were examined. EXPERIMENTAL

General Research Design Particulate Matter samples were collected in Claremont and Fresno using a

Hi-Volume PM2.5 sampler on pre-washed Teflon filters. The filter extracts were tested on HPLC at particular intervals of time to quantify the production of ROS especially hydrogen peroxide in the PM2.5 filter samples. A systematic procedure was followed to identify the presence of ROS and their activity in PM: (1) collection of PM samples, (2) extraction of PM with aqueous and organic solvents, (3) test for the presence of ROS, and (4) separation of extracts. Each step is described briefly in further sections.

Sampling Locations Sampling was carried out in Claremont for a period of 19 days between July and August 2012. The rooftop of the Sprague Hall building at Harvey Mudd College was used to set up the sampling instrumentation. Samples were collected in morning (7 a.m.-1 p.m.), afternoon (1 p.m.-6 p.m.), and evening (6 p.m.- 7 a.m.).61 A portable meteorological station was used to obtain the meteorological data that collected speed and direction of wind, relative humidity, and temperature. Fresno, which is located in the center of the San Joaquin Valley (SJV), is subjected to highest levels of particulate matter pollutions in California. Samples were collected on the rooftop of the Industrial Technology building at California State University, Fresno, during winter from January-February for a period of 3 weeks. The sampling times were similar to those of the Claremont study. Figure 3 maps the sampling locations. 23 23

Figure 3. Regional overview of air quality sampling location sites at Claremont[A], CA and Fresno[B], CA.61

Sample Collection

Hi-Volume PM2.5 Sampler

Atmospheric PM2.5 mass loadings were measured on Teflon coated-glass filters (Tisch Environmental, Lot #102618003) with a pore size 0.45 µm and

260x300 mm dimensions using a Hi-Volume PM2.5 sampler (Tisch Environmental 24 24

TE-6001-2.5-I). Aluminum envelopes, which were rinsed with dichloromethane and baked for 2 h, were used to seal the cleaned filters and stored at -20oC.61

A high-volume, size-selective PM2.5 inlet sampler with 40 impactor jets (Tisch Environmental, TE-6070-2.5-HVS), shown in Figure 4, draws the ambient air through the clean filter at a rate of 1.13 m3.min-1. Smaller particles of sizes less than 2.5µm are collected onto the filter, whereas larger particles greater than 2.5µm are collected onto the oil-wetted surface using multiple impactors. Collected filters were stored for 24 h in the controlled humidity and temperature room prior to weighing. A mettler balance was used to weigh the mass concentrations of the filters under controlled relative humidity (40-45%) and temperature (22-24oC) conditions before and after sample collection. The filters were frozen at -20oC until subsequent analyses were performed.61

Figure 4. Tisch Environmental TE-6070 hi-volume PM2.5 sampler65 25 25 Extraction Methods

Overview Aerosol samples were analyzed for peroxides using a series of extraction methods after the collection of filters. Extraction of aerosol samples into the aqueous phase was the first step involved in sample preparation followed by the analysis of H2O2 using high pressure liquid chromatography (HPLC). Fluorimetric detection was used in sample analysis to identify the H2O2 concentrations in the samples.

Sample Preparation Filter samples of a particular size were cut and spiked with 2,2- trifluoroethanol that acts as wetting agent (sigma-Aldrich,T63002 ≥ 99%). A known volume of extraction solution, Di sodium ethylene diamine tetraacetic acid

(Na2-EDTA), was taken in a petri dish and the Teflon filters were inverted individually with the exposed surface in contact with the extraction solution; the petri dish was covered with a top. Filters were extracted for 24 h, with gentle agitation and the extract was injected into HPLC from 0 min till 6 h and a final injection was given at 24 h.

Extraction Solution Preparation The mobile phase was prepared in a 1L volumetric flask by adding by

(1mM) of (Na2-EDTA) to distilled water. The obtained solution was acidified to a pH of 2.5 using 1M sulfuric acid (H2SO4) and the final solution was made up with distilled water. 26 26 Preparation of Fluorescent Reagent Fluorescent reagent, used to detect peroxides in the sample solutions, was prepared using 26mM para-hydroxy phenyl acetic acid(POHPAA) and 0.5 M potassium hydrogen phthalate in distilled water. The solution mixture was heated and pH was adjusted to 5.8 using sodium hydroxide (NaOH).100 units/mL of type II horse radish peroxidase was added to solution mix and the volume was made up to 100ml using distilled water and stored in refrigerator (4oC) until used.

Organic Extraction Using Dichloromethanol (DCM) and Residual Filter Extraction To the Teflon filter, 2, 2, 2 tri fluoro ethanol was added as a wetting agent followed by Dichloromethanol (DCM). The filter was removed from DCM after certain period of time and DCM was evaporated. Four milliliters of extraction solution was added to the residual filter and also to the DCM evaporated petri dish, which was expected to contain DCM soluble organic species. Both the solutions were injected in to HPLC up to 24 h. Organic extractions were done for a subset of filters including Fresno filters 10, 11, and 12 and Claremont filters 13, 14, and 15.

Solid Phase Extraction (SPE) Solid phase extraction column (Cole Parmer T-10937-15) C18 of 6ml [6.5(L) x 10 (diameter) in cm] was used for the separation of non-polar organic species like quinones. The organics that are adsorbed on to the sorbent bed are then released from the SPE media using a solvent that dissolves the organics. A systematic procedure was followed during the usage of SPE cartridge. The sorbent bed was conditioned using a suitable solvent like methanol, which rinses away all the impurities on the sorbent bed. The aqueous extract of the sample was allowed 27 27 to pass through SPE, which allows the adsorption of the organics on to the sorbent bed. The aqueous solvent has less affinity for the analyte compared to that of SPE support material. A final elution was done with a solvent that has a strong affinity for analyte (DCM) to release the analyte from the support.

Testing of Reverse Phase Column The ability of the solid phase extraction column to adsorb the organics on to the adsorbent bed was determined by using UV-Visible spectrometer. An aqueous standard solution of quinones was prepared by dissolving a known amount of quinones to 15% of 95% ethanol and the solution was made up to volume using distilled water in a 100 ml volumetric flask. The peak intensities for pre- and post-solid phase extraction of the quinones in the aqueous standard was observed and compared. Water was used as blank. The pre-SPE peak intensities were much higher than the post-SPE peak intensities, which indicates an effective adsorption of quinones by the SPE column. The SPE bed was then washed with DCM and the resultant solution shows an increase in peak intensity for quinones at a particular wavelength.

To Check the Effect of Quinones on the Production of ROS To the Teflon filter, 2, 2, 2 tri fluoro ethanol was added as a wetting agent followed by extraction solution. The filter was allowed to stay in contact with the extraction solution for certain periods of time. The solution was injected into

HPLC until 24 h to check the production rates of H2O2, after the removal of quinones using SPE column. The DCM extract of quinones was tested for the presence of quinones using gas chromatography associated with mass 28 28 spectrometry (GC-MS). Trial filters and Fresno filter 11 were tested to find the effect of quinones on ROS production.

Instrumentation

Fluorimetric Analysis of H2O2 by HPLC PM extracts were tested for the presence of ROS using post-column fluorescence method.13 The HPLC unit consists of a peristaltic pump (Rainin, Dynamax Model RP-1), a 250 mm (Length) x 4.6 mm (Internal diameter) hypersil ODS-2 C18 stationary phase reverse phase analytical column (Thermo Scientific), An injection valve (Rheodyne 7125), spectrofluorometric detector (Shimadzu RF- 10AXL), and an isocratic pump (Shimadzu LC-10ADvp). Hydroperoxides are detected via a post-column fluorimetric method. The mobile phase is the same as extraction solution used in the extraction of aerosols from Teflon filters. Sample is injected into the system through an injection valve attached to a 20-µL sample loop. When the injection valve lever was moved to an injection mode, the mobile phase was directed to the sample loop to push the sample towards the reverse phase column. The reverse phase column separates hydroperoxides by polarity where the most polar species elutes first which is hydrogen peroxide. The fluorescence reagent was delivered at a rate of 0.06ml/min by peristaltic pump. The mixture is then forced through 50 cm of 0.02- inch internal diameter tubing that was coiled into the Serpentine II configuration which increases the mixing time between peroxides and fluorescent reagent. As the sample reaction mixture passes through the analytical column, the ROS present in the sample gets separated and is oxidized selectively by horseradish peroxidase, which in turn abstracts an electron from para hydroxyl 29 29 phenyl acetic acid (POHPAA) molecule to generate a radical. The POHPAA radical reacts with another POPHAA (component of fluorescence detector) to form a dimer (R30). Horseradish peroxidase enzyme catalyzes a stoichiometric reaction between hydroperoxides and POHPAA, resulting in quantitative conversion of H2O2 to POHPAA dimer. The obtained dimer fluoresces only in the presence of a base which is added to the system using the same peristaltic pump at the rate of 0.06 mL/min. The fluorescence can be identified using fluorescence detector (Figure 5).

CH2COOH

CH2COOH CH2COOH

2 H2O 2 + H2O2 + OH

OH OH (R30)

Figure 5. High Performance Liquid Chromatography with post-column derivation and fluorescence detection instrument.63 30 30

Finally, the solution was sent through the fluorescence detector where a Xenon (Xe) lamp was set to 320 nm for excitation and 400 nm for the emission which was detected with a photomultiplier tube. A computer that was connected with fluorescence detector records the voltage as signal in a chromatogram of mV versus retention time, where peaks correspond to peroxide detection. The output signal was then recorded and analyzed using CHROMPERFECT software.

Calibration of HPLC The analytical response of hydrogen peroxide is determined by the ability of column to quantitatively pass the hydroperoxides and also ability of the enzyme reaction to quantitatively convert all the hydroperoxyl groups to the fluorescent product. The samples can be compared with the calibrated solutions if both the parameters are nearly unity. Additionally, titrimetric methods were used to standardize and calibrate pure solutions of hydrogen peroxide

Quantification of H2O2 to pass through HPLC column is measured by operating the analytical system with the column in place and determining the response for H2O2. The column is then removed and the response is again measured. The ratio of these two gives the column recovery efficiency. The column efficiency for the used column was nearly unity which is 1.05.

H2O2 Standards Used in Calibrations Redox titration was performed to determine the accurate concentrations of standard H2O2. Hydrogen peroxide stock solutions from three different laboratory suppliers (Sigma-Aldrich, Fischer, and Macron) were standardized to choose a better stock solution with approximately 30% (w/v) concentration. Redox titrations were used to determine H2O2 concentrations in all the three laboratory suppliers of 30% (w/v). The titration procedure is as follows; to a clean 250ml 31 31

Erlenmeyer flask, 25ml of water, 5ml of 6M sulfuric acid (H2SO4) and 1ml of 30%

(w/v) Hydrogen peroxide (H2O2) was added and swirled to mix. Sulfuric acid solution was used to provide an acidic environment for oxidation-reduction reaction to occur. Potassium permanganate (KMnO4, 0.098M) was used as titrant and was added drop-wise using a volumetric burette. The permanganate in KMnO4 solution acts as its own indictor and solution turns from colorless to pale pink near the equivalence point.

A primary H2O2 solution is made by diluting 100µl of standard stock -3 solution to 100mL of water, which gives a H2O2 of concentration of 10 M. H2O2 standard solution for each supplier is then made by diluting 1000,100 and 10 µL of primary H2O2 solution to 100mL of water yielding a concentration range of 9.8x10-5 to 9.8x10-7 M. The dilutions for Fischer stock solution is prepared by adding 2,3,4 and 5mL of water to 1mL of primary H2O2 solution to get the -5 concentrations of 1.9-4.9x10 M. Each H2O2 standard is run for a minimum of three times and the generated fluorescence signals are recorded. The average peak area per H2O2 standard is plotted against H2O2 concentration. The peak area of each signal is found through CHROMPERFECT assisted integration.

Flow Rate of Pump Flow accuracy is checked at mL/min, with the column in place, by measuring the time required to fill a 20 mL measuring cylinder from the detector outlet. Water is used as a solvent to check the flow rate of the pump.

Calibration Using a Correlation Factor The principle is to establish a linear calibration response. A single standard concentration run can be used to calculate correlation factor, and thus can be applied to all sample peak areas to obtain concentration values. To use this 32 32 method, it is essential to confirm linearity by running a series of dilutions which must include a zero blank. Thereafter, it is necessary only to run the single standard periodically during the sequence to confirm that the correlation factor remains constant. Upon subsequent computation, if the detector gives a linear response to concentration, we get a straight line. Mechanical aspects affecting performance and sensitivity were also examined. The pressure with which the eluent is flown into the system was also checked in the presence of column. In addition to mechanical aspects, the effect of extraction solution pH on H2O2 production was also observed. Deviation in the pressure, flow rate, and eluent pH did not affect the performance of the HPLC, except for a slight change in the signal.

Sample Derivatization Sample derivatization method allows more sensitive transformation of higher volatile quinones to be detected by GC/MS analysis. Cho et al. described derivatization process in his study, to enhance the signals within the GC-MS for selected quinones including 1, 4-chrysenequinone, phenanthraquinone, 1, 2 - naphthoquinone, 1, 4-naphthoquinone. A certain amount of concentrated sample was transferred into a vial with 0.2mL of acetic anhydride and 0.1g zinc. The contents of the vial were sealed, mixed and incubated at 80oC for three 5-min intervals. The contents in the vial were vented, mixed and returned to the dry bath incubator. After the 15-min heating, a second portion of zinc was added and the same procedure was followed. After the final heating, the vials were allowed to cool to room temperature and 0.5mL of deionized water and 3mL of pentane was added. The contents were mixed and allowed to settle for 10 min before taking the top pentane layer for GC-MS analysis. 33 33 GC/MS An Agilent 6890 plus series with a Hewlett Packard 5973 mass selective detector was used to analyze the quinones that are responsible for H2O2 production. A GC column of measurements 30mx250µmx0.25µm made of HP- 5MS 5% Phenyl methyl siloxane capillary column (Model no: HP 19091S-433) was used. The data were analyzed using Chem station software. The modified GC has a programmable temperature vaporization (PTV) inlet technique that is used for large volume injections has many advantages over traditional split/splitless inlet. The injection volume can be 60µl or higher for PTV inlet, which increases the analytical sensitivity for low concentrations with higher volumes in comparison to 2-5µl for split/splitless inlet. The programmable temperature control system of a PTV inlet consists of a heating coil and a cooling jacket that uses liquid CO2 as coolants. The dimensions of a vaporizing chamber determine the maximum volume of each injection and are limited by the transfer of sample to the capillary column. The GC-Ms was modified from split/splitless inlet system to a programmed temperature vaporizing inlet which allows the introduction of high volume samples which in turn increases the sensitivity. The sample introduction starts with a high flow of Helium (He) carrier gas at the rate of 1.0 ml/min. The samples were injected into the solvent vent inlet, set o at 40 C and cooled with a CO2 cryogenic trap system that was set at a pressure of 7.62 psi. The temperature is adjusted below the solvent boiling point that allows the maximum retention of the analyte inside the liner by solvent trapping, and the majority of the solvent in the sample is released via a split exit. Multiple injections with appropriate time intervals between the injections is done for the injected solvent to evaporate. After a sufficient amount of sample is injected and solvent venting is complete, the split exit is closed and the injector temperature is rapidly 34 34 increased at 300oC/min to a final inlet of 300oC that initiates a splitless transfer of the sample to the GC column. Non-volatile matrix constituents tend to remain inside the liner and are unlikely to enter and contaminate GC column. After the sample transfer, the inlet temperature can be kept high to bake off the retained substances with a high split flow. The oven temperature is set at 50oC and held for 4 min then ramped 5oC/min over a period of 39 min until 310oC is reached. The total run time was 51 min for quinones. Underivatized and derivatized quinones were analyzed using two different selective ion monitoring methods (SIM). SIM allows the mass spectrometer to detect specific compounds with very high sensitivity and it also isolates and identifies molecular ions that possess selected mass fragments with monitored fragmentation patterns (M+, M-CO+ and M-2CO+) for underivatized samples and + + (M-CH2CO and M-2CH2CO ) for derivatized samples. SIM mode detects the masses of specific molecular ions at trace levels in comparison to a wide range of masses in full scan mode, where selectivity is not active.

Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) The HYSPLIT model, developed by the U.S. National Oceanic and Atmospheric Administration (NOAA) and Australia’s Bureau of Meteorology, is a system that is used to estimate dispersion and deposition of particulate pollutants. The model is used to compute air parcel trajectories from source location using the meteorological data. The model uses a Lagrangian solution of advection and diffusion equation as a transport model for chemicals to identify the air parcel trajectories within a given area. Chemical species can be simulated into this model 35 35 and the concentrations of pollutants at different locations can be determined at a particular point of time.2 RESULTS

Hydrogen Peroxide Calibration Hydrogen peroxide from three different suppliers (Macron, Fischer and Sigma-Aldrich) was used to build a suitable and perfect calibration curve of the standard as shown in Figure 6. Calibrations produced were used to determine fluorimetric response of H2O2 in analyzed samples and also to monitor its performance. The calibration curve was constructed for all the three stock solutions ranging using the results obtained from the titrimetric analysis.

Figure 6. Calibration curve of H2O2 for Macron, Fischer and Sigma-Aldrich

The average peak area per H2O2 standard is plotted against H2O2 concentration as shown in the Figure 6.The linear fit indicates a strong correlation 2 (R >0.9) between peak area and H2O2 concentration. Table 2 represents the calibration response curve plot statistics for Figure 6. 37 37

Table 2. H2O2 Calibration Data for Different Lab Suppliers 2 H2O2 supplier Intercept Slope R

Macron 7.7E+05 6.9E+10 0.96 Fischer 1.9E+05 7.0E+10 0.94 Sigma-Aldrich 2.1E+03 7.7E+10 1

Production Rates of H2O2 for the Trial Filters A series of experiments were performed on the trial filters (Fresno 1, 2, 3). Trial filters were collected during the first day of the collection campaign and were not used for analysis along with the other filter samples. The air flow rate through the instrument during the first day of collection was in appropriate due to the power problems and instrumental settings that may alter the air mass collected on to the filters. Numerous trials were performed on each filter with different variations to give a brief idea of the tests to be performed on the filter samples. The formation rates of hydrogen peroxide were examined for trial filters among all three sampling periods (morning, afternoon, and overnight) as represented in Figure 7. Initial measurements of H2O2 with in the first 6 h were used to understand the rate of H2O2 formation using a linear fit. The slope of the linear fit represents the rate of H2O2 formation per hour. The initial formation rates -3 -1 -3 -1 of H2O2 were observed to be (2.9± 1.9) ng.m .hr , (2.7± 2.9) ng.m .hr , and (1.1 ±0.6) ng.m-3hr-1 for afternoon, morning, and overnight samples respectively which are represented as with EDTA in Figure 8. The uncertainties represent the standard deviation for the respective sampling periods. 38 38

Figure 7. Production rates of H2O2 per hour for the trial filters

Figure 8. H2O2 Production rates under variable conditions for Fs-02 39 39

Figure 8 represents the rate of production of H2O2 for the Fs-02 (afternoon) filter under variable conditions using a linear fit. The rate of formation of H2O2 in the absence of quinones is found to be increasing linearly for several hours and the production rate is observed to be (1.8± 2.9) ng.m-3hr-1. The quinones are removed from the extraction solution by using a solid phase extraction column (SPE). -3 -1 The rates of H2O2 formation are observed to be (-0.1 ±0.7) ng.m hr and (1.0 ±2.5) ng.m-3hr-1 in the absence and presence of filter in the extraction solution respectively.

Figure 9 represents the average production rate of H2O2 over 6 h under variable conditions. The error bars represents the standard deviation. The production rates of H2O2 in the presence of EDTA ranged in between (5.8± 3.2) ng.m-3hr-1 to (11.7± 7.4) ng.m-3hr-1 in between the sampling periods. The production rates for morning and afternoon filters are close to each other with relatively no statistical significance(p=0.38) between the samples. SPE in Figure 9 indicates solid phase extraction or the removal of quinones from the extraction solution. The production rates ranged in between (7.6± 4.7) ng.m-3 to (9.7± 6.5) ng.m-3 for the morning and afternoon filters. The production rates are found to be statistically insignificant between morning and afternoon (p=0.33) with the morning production rates very close to the afternoon.

The average production rates of H2O2 are found to be in the range of (0.1± 0.3) ng.m-3hr-1 to (0.3± 0.6) ng.m-3hr-1 in the absence of filter and (7.8± 2.8) ng.m- 3hr-1 to ( 5.5± 1.9) ng.m-3hr-1,when the filter is back in to the extraction solution, as observed form Figure 8. The statistical significance was found to be relatively high (p<0.05) in the presence and absence of filter in extraction solution. 40 40

Figure 9. Differences in the production of H2O2 under variable conditions for Fresno filters 1 and 2.

The statistical analysis for the Figure 9 shows that the average H2O2 production rates for the Fs-01 and Fs-02 remains unchanged with EDTA, without quinones (represented as SPE in Figure 9) and for the filter back in the extraction solution after 2 h. The statistical difference between the three tests (with EDTA, without quinones and filter back into extraction solution after 2 h) are found to be (p>0.05), for both the morning and afternoon filters which indicates a relatively low statistical significant difference in between the tests.

Production Rates of H2O2 for Fresno Samples: Fresno Filter 11 Numerous trials have been conducted on Fresno filter 11, in triplicates, to explore the possible source of H2O2. Figure 10 shows the production rates of hydrogen peroxide for 6 h under variable conditions. The rate of H2O2 production 41 41 varies under different experimental conditions. The error bar indicates the statistical error for each test.

Figure 10. Production rates of H2O2 under variable conditions for Fs-11

The production rates of hydrogen peroxide in the presence of EDTA was found to be (5.4 ± 0.7) and (4.2± 3.1) in the absence of EDTA. The statistical analysis indicates that the production rates of H2O2 for Fresno filter 11 (afternoon) with and without EDTA are statistically insignificant (p=0.18) as observed from t- test. The observation implies that the presence or absence of EDTA in the extraction solution has no effect on the production of H2O2. The metals, if present in the filter extract, are thought to chelate with EDTA of extraction solution, which further dissociates H2O2 to hydroxyl radicals leading to a decreased H2O2 content in the samples16. The metals, if present in the extraction solution, are also 46,47 thought to generate higher levels of H2O2 . But the results obtained showed no 42 42 statistical difference in the presence and absence of EDTA in the extraction solution.

SPE in Figure 10 represents the average H2O2 production rate (6.2± 3.9) ng.m-3hr-1 in the absence of quinones. This shows that EDTA, removal of quinones by SPE, and the filter back into the extraction solution after 2 h have no overall effect on the production rates of H2O2. A statistical t-test was also performed in between the tests, (with EDTA, without quinones, filter back into extraction solution after 2 h) which showed no statistically significant difference( p>0.05).

The production rates of H2O2 over 6 h for organic wash and residual aqueous filter extract were found to be (2.7± 1.0) ng.m-3hr-1 and (0.2± 0.1) ng.m-3hr-1 respectively. A relatively high statistically significant difference (p=0.013) was observed in between organic wash and residual aqueous filter extract.

Production Rates of H2O2 for Other Fresno Filter Samples

Figure 11 represents the average mass loadings of H2O2 for the Fresno samples that were collected from 1/16/13 to 1/19/13. Each bar representsts the average H2O2 mass loadings of a specific sample period in a day (morning,afternoon,overnight). Figure 12 represents weighed average of the three samples (morning,afternoon and overnight) per day. The error bars indicate the standard deviation. The rate of formation of H2O2 ranged in between (2.6±1.5) ng.m-3 to (15.7±11.2) ng.m-3.hr-1 from 16 to 19 January. 43 43

Figure 11. Rate of formation of H2O2 for Fresno samples grouped into morning, afternoon, and overnight samples

Figure 12. Average production rates of H2O2 for the filters collected from 16 to 19 January 2013 44 44

Table 3 represents the collection details of the Fresno samples which includes the sampling dates of the filters along with their respective collection periods (morning, afternoon and overnight). Table 3 represents the average 3 -1 production rates of H2O2 from respective filter samples in ng/m .hr and particulate mass loadings in µg/m3

Table 3. Collection Details of Fresno Filters Formation rates 3 Date of Collected of H2O2(ng/m . PM2.5 Mass collection Filter period hr-1) loadings (µg/m3)

15-Jan FS13F-1 Morning 11.93 -

FS13F-2 Afternoon 17.26 -

FS13F-3 Overnight 9.24 - 16-Jan FS13F-4 Morning 5.34 16.96 FS13F-5 Afternoon 5.76 20.38 FS13F-6 Overnight 3.34 15.15 17-Jan FS13F-7 Morning 5.68 26.09 FS13F-8 Afternoon 6.91 17.92 FS13F-9 Overnight 2.79 16.72 18-Jan FS13F-10 Morning 2.60 22.83 FS13F-11 Afternoon 15.73 24.29 FS13F-12 Overnight 3.58 19.59 19-Jan FS13F-13 Morning 11.29 28.05 FS13F-14 Afternoon 10.85 27.41 FS13F-15 Overnight 4.52 24.97 45 45

Production Rates of H2O2 for Claremont Filters

H2O2 measurements have been studied for some of the Claremont samples which were collected for a period of 19 days during summer from July-August of 2012. The mass loadings for the Claremont filters are described in Table 4. Figure 13 represents the mass loadings of specific Claremont filters for each of the sampling period (morning, afternoon, and overnight). The error bars represent standard deviation calculated individually for each sample. The mass -3 -3 loadings of H2O2 ranged from (2.0±1.4) ng.m to (12.7± 10.9) ng.m .

Figure 13. Rate of formation of H2O2 for Claremont filters

H2O2 measurements have been studied for some of the Claremont samples which were collected for a period of 19 days during summer from July-August of 2012. The mass loadings for the Claremont filters are described in Table 4.

46 46 Table 4. Collection Data for Claremont Filters

Date Formation rates of PM2.5 Mass 3 -1 3 collected filter Time period H2O2(ng/m .hr ) loadings(µg/m ) 26-Jul CLMT12F-01 Morning 7.25 12.75 CLMT12F-02 Afternoon 7.28 16.59

CLMT12F-03 Over night 3.49 14.27

27-Jul CLMT12F-04 Morning 4.83 12.81 CLMT12F-05 Afternoon 6.02 11.33

CLMT12F-06 Over night 3.16 8.70

28-Jul CLMT12F-07 Morning 4.96 16.58 CLMT12F-08 Afternoon 2.99 9.77

CLMT12F-09 Over night 2.01 8.10

30-Jul CLMT12F-13 Morning 12.74 12.49 CLMT12F-14 Afternoon 8.51 13.36

CLMT12F-15 Over night 9.17 11.88

4-Aug CLMT12F-28 Morning 3.40 14.79 CLMT12F-29 Afternoon 3.71 12.79

CLMT12F-30 Over night 1.66 12.62

9-Aug CLMT12F-43 Morning 4.75 16.06 CLMT12F-44 Afternoon 4.68 17.91

CLMT12F-45 Over night 3.48 12.86

10-Aug CLMT12F-46 Morning 4.76 17.49 CLMT12F-47 Afternoon 4.53 19.70

CLMT12F-48 Over night 5.85 7.66

47 47

Rate of H2O2 Formation in Organic Extracts and Residual Filter Extracts for Specific Filter Samples

Figures 14 and 15 represent the production rates of H2O2 and the statistical differences under certain conditions for specific Fresno and Claremont samples, respectively. Organic wash in both the figures represents the DCM (dichloromethane) extract of the ROS.

Figure 14. Rate of formation of H2O2 for aqueous, organic and residual filter extracts for specific Fresno samples

The average H2O2 production rate over 6 h for the Fresno filter, which was collected on 1/18/13 was observed to be (2.9 ±2.0) ng.m-3hr-1 in the organic wash.

The weighed average production rates of H2O2 for the residual ROS in the aqueous -3 -1 extract is found to be (1.6 ±0.6) ng.m hr . The H2O2 production rates for the 48 48

Figure 15. H2O2 variations for aqueous, organic, and residual filter extract for specific Fresno samples organic wash are found to be statistically significant in between morning and afternoon and overnight samples (p<0.05). From the data, it can be observed that afternoon samples have the highest production rates for both organic wash and residual filter extracts for the Fresno samples. The variations for organic extracts, residual aqueous extracts, and aqueous extracts are observed for the Claremont filter that was collected on 7/30/12. The - average production rate of H2O2 for organic wash was found to be (3.5 ±1.7) ng.m 3hr-1 with a relatively high statistical significant difference observed in between the morning, afternoon and overnight samples (p<0.05). The production rates for ROS residual extract was found to be (2.5±1.0) ng.m-3hr-1 with relatively less or no statistical difference between the morning and afternoon samples, afternoon and overnight samples ( p>0.05). A relatively high statistical difference was observed between morning and overnight samples (p=0.014). The error bars represent the standard deviation. DISCUSSION

Ambient Mass Loadings Hydrogen peroxide levels ranged from 2.8 to 17.8 ng.m-3 in Fresno and 2 to -3 12.7 ng.m in Claremont. The average production rates of H2O2 are found to be 7.8± 4.7 ng.m-3.hr-1 for Fresno samples 5.2± 2.6 ng.m-3.hr-1 for Claremont samples.

Figure 16 represents the temporal variations in the production of H2O2 for specific Fresno and Claremont samples. The error bars represent the standard deviation.

The statistical analysis for the average rate of formation of H2O2 in between Fresno and Claremont samples showed a relatively less or no statistical difference

(p=0.105), which indicates that average mass loadings of H2O2 for both the samples are similar in same order of magnitude.

Figure 16. Variation between Fresno and Claremont samples

The average mass loadings of H2O2 were equivalent with few other studies -3 41 which reported the H2O2 levels in ng/m . Arellanes et al. reported H2O2 50 50 concentrations ranging from 4 to 8 ng. m-3. Hasson and Paulson et al.30 observed -3 even lower H2O2 levels with an average of 3.2ng.m . The obtained results in this study are found to be lesser than those of Taipei, Hung, and Wang36 with an average of 21 ng.m-3 and Venkatachari et al.37, who reported an average of 243ng.m-3 in Rubidoux. The extraction time was found to be 2 to 3 h for all the previous measurements.

Figure 17 illustrates the temporal variations in the average H2O2 mass loadings for the specific Fresno filter samples that were collected during the period (1/15/13-1/19/13). The filters were grouped to their respective sampling periods to morning, afternoon, and overnight.

From Figure 17, it can be observed that the average H2O2 formation rates for Fresno were higher in afternoon samples (p=0.017) when compared to the overnight samples. The formation rates of H2O2 for morning samples are very close to the afternoon samples with relatively less or no statistical significant difference (p=0.184). The overnight H2O2 production rates are slightly lower than the morning samples (p=0.097). Figure 18 represents the temporal variations for specific Claremont samples. Each bar represents a weighed average of the three samples (morning, afternoon, and overnight) per day.The error bars indicate the standard deviation of the formation rates of H2O2. The average mass loadings of H2O2 are statistically insignificant ( p>0.05) in between the sampling periods (morning, afternoon, and overnight), but a relatively high statistical difference is observed between morning and overnight samples (p=0.020).

51 51

Figure 17. Temporal variations of H2O2 formation rates for specific Fresno samples

Figure 18. Temporal variation of mass loadings for Claremont filters 52 52

From the data, it can be observed that the average H2O2 mass loadings for Fresno samples are higher in afternoon, which are closely followed by morning samples. The production rates of H2O2 in Claremont are highest in the morning followed by afternoon samples with no statistical significance in between the two sampling periods. The diurnal results obtained were consistent with the results reported by a similar study in Rubidoux37, which measured the concentrations of ROS during different time intervals of a day. The observations concluded that, with the increased ozone concentrations, the rate of production of ROS increased during the early afternoon period (12-3 p.m.). The intensity of photochemical reactions is found to be highest during the afternoon. Another study conducted at Taipei36 reported that concentration of photchemical reactions is the key factor that affects the ROS production.

The night time production rates of H2O2 are lower than the day time. The increased activity of H2O2 in the afternoon for the Fresno filters might be due to reactivity of chemicals in the assay, which are formed photochemically. The particulate emissions may not be uniform throughout the day and the higher production rates of H2O2 in the morning for the Claremont filters might be due to the vehicular emissions during the rush hour, which generate chemicals that lead to the production of H2O2. Although there is no statistical significance between morning and afternoon samples, the pattern of temporal variation suggests that photo chemically generated compounds are one of the main sources of ROS and the results obtained are consistent with the previous studies.36,37 Further studies are needed to find the origins and also the sources that are responsible for H2O2 production. 53 53

The SPE results (removal of quinones) indicates that there exists no difference in the production rates of H2O2 in the presence and absence of quinones, which might be due to the oxidation of organic aerosol within the particles that increase the water solubility and number of polar functional groups and leads to H2O2 dissolution in water. The H2O2 production rate from residual filter is found to be lesser than organic extract due to the removal of organic species by DCM. The production of ROS from residual filter may be due to water soluble and non-volatile organic species left over on the filter.

Parallel Studies

Correlation Between Particle Mass and H2O2 Production Parallel studies were conducted by a UCLA group in order to find the ambient PM2.5 mass loadings for both Fresno and Claremont samples. Correlation 3 between the ambient PM2.5 mass loadings and H2O2 formation rates in µg/m were observed for both the locations. Figure 19 and Figure 20 represent the correlation between PM2.5 loadings and H2O2 mass loadings for Fresno and Claremont samples, respectively. Table 5 represents the statistical data for the correlation between PM2.5 loadings and H2O2 formation for Fresno and Claremont samples.

From the data, it can be observed that H2O2 generation for both Fresno and

Claremont samples showed no significant correlation with PM2.5 mass loadings (p>0.05). The linear fit of Figures 19 and 20 implies that particle mass is a weak indicator of aerosol-phase H2O2 and the chemical composition of particulate matter,chemical reactions within the particles play a major role in the formation of

H2O2 than the particle mass. The correlation results obtained were not consistent with the previous studies like Arellanes et al.,41which showed a significant positive 54 54

Figure 19. Correlation between PM2.5 Particle mass and H2O2 mass loadings in (µg/m3) for Fresno filters

Figure 20. Correlation between PM mass loadings and H2O2 mass loadings in (µg/m3) for Claremont filters. 55 55 Table 5. Statistical Data for Correlation Between PM 2.5 Mass Loadings and H2O2 Formation Correlations between PM2.5 and H2O2 Mass Intercept Standard Slope Standard R2 P-value loadings for error error

Fresno 0.0093 ±0.0078 -8.25E-05 ±0.00035 0.0053 0.821

Claremont 0.0046 ±0.0026 2.87E-05 ±0.00019 0.0013 0.883

correlation between PM2.5 mass loadings and H2O2 production. This might be due to season, temperature of the sampling period and loacation of sampling (Riverside,CA), where the aged, fresh aersols and secondary organic aerosols are emitted from nearby industries and dairy farms. Also, particles originating form Los Angeles are thought to travel to Riverside. As the particles travel, their physical and chemical properties alter depending on the regional meteorological conditions, photochemical activity and the presence of other gas-phase pollutants present.

Role of Quinones and Metals One of the major aims of this study is to identify the role of quinones and transition metals in the formation of H2O2. To answer objectives 4 and 5 (see p.

20), a correlation was performed between H2O2 and quinones, transition metals.

Correlation with Quinones Parallel studies were conducted in California State University, Fresno on the Fresno filter extracts in order to identify the role of quinones in the formation of ROS. The concentrations of quinones in Claremont filters were very less, so it was difficult to identify the relationship between the quinones and the rate of formation of H2O2 in Claremont samples. 56 56

Filter extracts were extracted in to the surrogate lung fluid and the residual organics on the filter medium were extracted in to the organic solvent. SLF is an aqueous, buffered extract solution prepared by adding 114mM of sodium chloride, 7.8mM of Disodium phosphate and 2.2mM of Potassium Dihydrogen phosphate to deionized water. Figure 21 represents the determination of correlation between the average mass loadings of H2O2 for each sample period plotted against the respective quinone mass loading averaged for the same time for the Fresno samples. A linear regression analysis was performed to identify the correlation between H2O2 and quinones. Table 6 represents the statistical data, results, and the associated correlation.

Table 6 represents the correlation of H2O2 with phenanthraquinone (PQ) (p=0.057) and anthraquinone (AQ) (p=0.34). The data from Table 6 imply that there exists no correlation between rate of production of H2O2 and anthraquinone but, a partial correlation is observed between phenanthraquinone and H2O2 production.

Table 6. Statistical Data for the Correlation Between H2O2 Formation and Specific Quinones Correlations observed Intercept Standard Slope Standard R2 P- between error error value

H2O2 Vs 5.76 ±1.59 2.48 ±1.17 0.29 0.057 Phenanthraquinone

H2O2 Vs 8.51 ±1.42 -8.84 ±9.10 0.067 0.34 Anthraquinone

The results obtained in this study showed that the removal of quinones using a solid phase extraction column (SPE) does not affect the rate of production of H2O2, which implies that quinones are not responsible for the production of 57 57

Figure 21. Correlation between H2O2 against anthraquinone and phenanthraquinone 58 58

H2O2. The partial correlation of PQ against the production of H2O2 may not prove that PQ is responsible for generating ROS. PQ, which is found in the particle phase of the ambient air, is thought to be emitted directly by vehicular exhaust and is mostly formed in the atmosphere by photochemical reactions of parent polycyclic aromatic hydrocarbons (PAHs). Wang and co-workers53 reported that the formation of 9, 10-phenanthraquinone by the oxidation of phenanthrene occurs during the day when OH radical initiation is prominent.

Correlation with Metals Parallel studies were conducted at University of California, Davis, which measured the average metal concentrations for the Fresno and Claremont filter extracts using ICP-MS. The obtained Cu concentrations were compared against the mass loadings of H2O2 performed at California State University, Fresno to test the relationship between them. At UC Davis, transition metals in PM samples were measured using inductively coupled plasma mass spectrometer (ICP-MS). Also, colleagues at UC Davis were only able to measure copper accurately, but not other transition metals due to the interference from the chemical species present in the SLF. The average concentrations of Cu obtained were plotted against the mass loadings of the H2O2 obtained. Figure 22 represents the correlation determinations between the H2O2 and respective average copper concentrations for Fresno samples and Figure 23 represents the correlation determinations between rate of formation of H2O2 and Cu concentrations for Claremont samples.

59 59

Figure 22. Correlation between the average copper concentration and rate of formation of H2O2 for Fresno samples

Figure 23. Correlation between H2O2 production rates and average copper mass loadings for Claremont samples 60 60

The average copper concentrations for each sampling period were plotted against the respective H2O2 formation rates that were averaged for the same time.

The p-value for rate of formation of H2O2 against the Cu concentrations for Fresno (0.12) and Claremont (0.51) samples indicates that there exists no correlation between the Cu concentration and rate of formation of H2O2.

The correlation results observed between Cu and H2O2 are inconsistent to the results reported in the previous studies. The lack of correlation between the two does not rule out the fact that Cu may not be responsible for the production of

H2O2. Cu has been shown to be capable of converting free radicals (HO2/OH) to 33 H2O2 and thus increases the formation rate of H2O2. Arellanes et al. showed that a strong correlation exists between H2O2 generation and Cu in the fine PM, but also reported a possibility of metal contamination with bear fittings, which were used to connect the sampling lines during the collection. See et al. reported that a strong correlation (r=0.80) was observed between water soluble Cu and ROS levels produced. Charrier et al.49 also reported a good correlation between production of ROS and soluble Cu (R2=0.59) under the SLF conditions. The inconsistency may be due to the study involving only a small subset of samples or due to the involvement of unknown measured constituents that resulted in the less reactivity of the samples.

Back Trajectories The Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) software from NOAA was used to investigate the source locations using backward trajectory analysis. HYSPLIT is designed for air pollution and dispersion applications. All the back trajectories were computed to end at Fresno sample location (36.48 N, 119.44 W) and at Claremont sample location (34.11N, 61 61

117.71W). The back trajectories are computed with final altitudes of 250, 500, 1,000, and 1,500 meters above the ground level for Claremont samples and 250 to 3,500 m above the ground level for Fresno samples. The backward trajectories for a 24-h period included 6 to 12 back trajectories, one inserted for every hour to the final end time for morning, afternoon and overnight samples respectively. Figure 24 represents the source location of the air mass for the Fresno samples with higher production rates of H2O2. The average production rates of -3 -1 H2O2 from the higher source locations are found to be 11.9ng.m hr . Figure 25 represents the source location of the air mass for the Fresno samples that showed lower production rates of H2O2. The average production rates of H2O2 from the lower source locations of air mass are found to be 4.0ng.m-3.hr-1. The source locations for both the higher and lower H2O2 production rates are found to be similar, which is mostly from national forests in and around California. This indicates that biomass burning that includes emissions from wildfires and wood combustion might be a possible source of origination of H2O2 in Fresno samples. The wind direction in Claremont samples is seen to be originating from NW and SW as shown in the Figures 26 and 27 during the three sampling periods (morning, afternoon, and overnight), which indicates that the possible source for

H2O2 might be from the LA basin. Figure 26 indicates the source location of air mass for the Claremont samples that has higher formation rates of H2O2 and the average production rates are found to be 7.1ng.m-3.hr-1 from the source location that has higher H2O2 formation rates. Figure 27 indicates the source location of air mass for the Claremont samples that has lower formation rates of H2O2 and the average production rates of H2O2 for the lower source locations is found to be 3.2ng.m-3.hr-1. The source locations for both the higher and lower production rates are found to be similar to the LA surroundings. The source locations for the high 62 62 signals are seen to be more from the port and downtown directions, while the source locations for the lower production rates seem to be originating from foothills, national forests, and Long Beach along with LA surroundings. The higher production rates observed in the morning might be due to higher vehicular emissions during the rush hour from the nearby highways.

Figure 24. Backward trajectory of airmass for Fresno samples with higher production rates of H2O2

63 63

Figure 25. Backward trajectory of airmass for Fresno samples with lower production rates of H2O2 64 64

Figure 26. Backward trajectory of airmass for Claremont samples with higher H2O2 formation rates 65 65

Figure 27. Back trajectory of airmass for Claremont samples with lower H2O2 formation rates CONCLUSION

-3 The concentration of H2O2 is found to be 5.2± 2.6ng.m for Fresno samples -3 and 7.8± 4.7 ng.m for Claremont samples. The rate of formation of H2O2 is found to be similar for both the samples with relatively less statistical difference in between them. The production rates of H2O2 are found to be higher during morning and afternoon periods for both Fresno and Claremont samples and the

H2O2 rates are found to be decreasing during the nights for the both the samples. This might be due to the presence of a chemical compound that contributes to the production of H2O2 at both the sampling locations.

The possible sources for the H2O2 production are not clear and a source apportionment study needs to be done in order to find the exact sources for higher levels of H2O2 in the atmosphere. The rate of formation of H2O2 is not found to be in correlation with PM mass loading, which indicates that the chemical composition of the particulate matter and chemical reactions within the particles play an important role than the PM mass loadings.

The production of H2O2 is not correlated with anthraquinone and partially correlated with phenanthraquinone but, the SPE study (removal of quinones) proves that quinones are not responsible for the production of H2O2. The partial correlation of phenanthraquinone with H2O2 might be due to the emission of H2O2 from the same source as PQ-like vehicular emissions. The lack of correlation between H2O2 and Cu may not prove that Cu is not responsible in the formation of

H2O2. The observation proves that transition metals and quinones may not be responsible for the formation of H2O2 in the aerosol particles. The formation of 67 67

H2O2 in the particulate matter filter samples might be due to the presence of organic soluble, non-polar compounds present within the particles.

Future Work Future work will include the continuation of quantifying and identifying the source of H2O2 in the filter samples. Existence of metals in their free or complex form needs to be analyzed using electrochemistry, which will help in determining the role of metals in formation of H2O2. Further work on organic species needs to be done as they are believed to generate majority of H2O2 in the filter extracts. A solid phase extraction column (SPE) that separates polar compound from non- polar compounds can be used for fractionation and detected using specific instrumentation like GC/MS. REFERENCES

1. Tao, F.; Gonzalez-Flecha, B.; Kobzik, L., Reactive Oxygen Species in Pulmonary Inflammation by Ambient Particulates. Free Radical Bio. and Med., 2003, 35(4), 327-340.

2. Seinfield, J. H.; Pandis, S. N. Atmospheric Chemistry and Physics: From Air Pollution to Climate Change. John Wiley & Sons: New York, 2006.

3. EPA, U. S. National Ambient Air Quality Standards (NAAQS). http://www.epa.gov/air/criteria.html (16 April 2013)

4. USEPA, U., National Ambient Air Quality Standards. Accessible online at http://www.epa.gov/air/criteria.html 1990.

5. Watson, J. G.; Visibility: Science and Regulation. J. of the Air & Waste Management Assoc. 2002, 52(6), 628-713.

6. Watson, J. G.; Visibility: Science and Regulation. J. of the Air & Waste Management Assoc. 2002, 52(6), 628-713.

7. Harrison, R. M.; Yin, J. Particulate matter in the atmosphere: Which particle properties are important for its effects on health? The Science of the Total Environment 2000, 249, 85-101.

8. Kim, E.; Hopke, P. K. Source characterization of ambient fine particles in the Los Angeles basin. J. of Environ. Engineering and Sci. 2007, 6(4), 343- 353.

9. Finalyson-Pitts, B. J.; Pitts, J.N. Chemistry of the upper and lower atmosphere: Theory, experiments, and applications. Academic Pr: 2000.

10. Holmes, N. S. A review of particle formation events and growth in the atmosphere in the various environments and discussion of mechanistic implications. Atmos. Env. 2007, 41(10), 2183-2201.

11. Rudich, Y. Laboratory perspectives on the chemical transformations of organic matter in atmospheric particles. Chem. Rev. 2003, 103(12), 5097- 5124.

12. Eliason, T. L.; Aloisio, S.; Donaldson, D. J.; Cziczo, D. J.; Vaida, V. Processing of unsaturated organic acid films and aerosols by ozone. Atmos. Env. 2003, 37(16), 2207-221. 69 69 13. Pöschl, U.; Rudich, Y.; Ammann, M. Kinetic model framework for aerosol and cloud surface chemistry and gas-particle interactions–Part 1: General equations, parameters, and terminology. Atmos. Chem. and Phys. 2007, 7(23), 5989-6023.

14. Jacobson, M. C.; Hansson, H. C.; Noone, K. J.; Charlson, R. J. Organic atmospheric aerosols: Review and state of the science. Rev. of Geophysics, 2000, 38(2), 267-294.

15. Robinson, A. L.; Donahue, N. M.; Rogge, W. F. Photochemical oxidation and changes in molecular composition of organic aerosol in the regional context. J. of Geophys. Res.: Atmospheres 2006, 111(D3).

16. Jimenez, J. L.; Canagaratna, M. R.; Donahue, N. M.; Prevot, A. S. H.; Zhang, Q.; Kroll, J. H.; Decarlo,P. F.; Allan.J. D.; Coe, H.; Shimono, A. Evolution of organic aerosols in the atmosphere. Science 2009, 326(5959), 1525-1529.

17. Zhang, Q. J.; Jimenez, J. L.; Canagaratna, M. R.; Allan, J. D.; Coe, H.; Ulbrich, I.; Alfarra, M. R.; Takami, A.; Middlebrook, A. M.;Sun, Y. L. Ubiquity and dominance of oxygenated species in organic aerosols in anthropogenically‐influenced Northern Hemisphere midlatitudes. Geophys. Res. Lett. 2007, 34(13), 1-6.

18. Volkamer, R.; Jimenez, J. L.; San Martini, F.; Dzepina, K.; Zhang, Q.I.; Salcedo, D.; Molina, L. T.; Worsnop, D. R.; Molina, M. J. Secondary organic aerosol formation from anthropogenic air pollution: Rapid and higher than expected. Geophys. Res. Lett. 2006, 33(17), 1-4.

19. Herndon, S. C.; Onasch, T. B.; Wood, E. C.; Kroll, J. H.; Canagaratna, M. R.; Jayne, J. T.; Zavala, M. A.; Knighton, W. B.; Mazzoleni, C.; Dubey, M. K. Correlation of secondary organic aerosol with odd oxygen in Mexico City. Geophys. Res. Lett. 2008, 35(15), 1-6.

20. Lanz, V. A.; Alfarra, M. R.; Baltensperger, U.; Buchmann, B.; Hueglin, C.; Prévôt, A. S. H. Source apportionment of submicron organic aerosols at an urban site by factor analytical modelling of aerosol mass spectra. Atmos. Chem. and Phys. 2007, 7(6), 1503-1522.

21. Ulbrich, I. M.; Canagaratna, M. R.; Zhang, Q.; Worsnop, D. R.; & Jimenez, J. L. Interpretation of organic components from positive matrix factorization of aerosol mass spectrometric data. Atmos. Chem. and Phys. 2009, 9(9), 2891-2918. 70 70 22. Vlasenko, A.; George, I. J.; Abbatt, J. P. Formation of volatile organic compounds in the heterogeneous oxidation of condensed-phase organic films by gas-phase OH. J. of Phys. Chem. A. 2008, 112(7), 1552-1560.

23. Eliason, T. L.; Gilman, J. B.; Vaida, V., Oxidation of organic films relevant to atmospheric aerosols. Atmos. Env. 2004, 38(9), 1367-1378.

24. Valavanidis, A.; Fiotakis, K.; Bakeas, E.; Vlahogianni, T. Electron paramagnetic resonance study of the generation of reactive oxygen species catalysed by transition metals and quinoid redox cycling by inhalable ambient particulate matter. Redox Report 2005, 10(1), 37-51.

25. Chung, M.Y.; Lazaro, R. A.; Lim, D.; Jackson, J.; Lyon, J.; Rendulic, D.; Hasson, A. S. Aerosol-borne quinones and reactive oxygen species generation by particulate matter extracts. Environ. Sci. & Tech. 2006, 40(16), 4880-4886.

26. Reeves, C. E.; Penkett, S. A. Measurements of peroxides and what they tell us. Chem. Rev. 2003, 103(12), 5199-5218.

27. Sipilä, M.; Berndt, T.; Petäjä, T.; Brus, D.; Vanhanen, J.; Stratmann, F.; Patokoski, J.;Mauldin, R. L.; Hyvärinen, A.-P.; Lihavainen, H.; Kulmala, M. The role of sulfuric acid in atmospheric nucleation. Science 2010, 327(5970), 1243-1246.

28. Jackson, A. V.; Hewitt, C. N., Atmosphere hydrogen peroxide and organic hydroperoxides: A review. Crit. Rev. in Environ. Sci. and Tech. 1999, 29(2), 175-228

29. Hewitt, C. N.; Kok, G. L. Formation and occurrence of organic hydroperoxides in the troposphere: Laboratory and field observations. J. of Atmos. Chem. 1991, 12(2), 181-194.

30. Atkinson, R. Gas-phase tropospheric chemistry of volatile organic compounds: 1. Alkanes and alkenes. J. of Phys. and Chem. Ref. Data 1990, 26(2), 215-290.

31. Hasson, A. S.; Paulson, S. E. An Investigation of the relationship between gas-phase and aerosol-borne hydroperoxides in urban air. J. of Aerosol Sci. 2003, 34(4), 459-468. 71 71 32. Hasson, A. S.; Chung, M. Y.; Kuwata, K. T.; Converse, A. D.; Krohn, D.; Paulson, S. E. Reaction of Criegee Intermediates with water vapor: An additional source of OH Radicals in alkene ozonolysis. J. of Phys. Chem. A 2003, 107(32), 6176-6182.

33. Becker, K. H.; Bechara, J.; Brockmann, K. J. Studies on the formation of H2O2 in the ozonolysis of alkenes. Atmos. Environ. Part A. General Topics 1993, 27(1), 57-61.

34. Faust, B. C. Photοchemistry of clouds, fogs, and aerosols. Environ. Sci. & Tech. 1994, 28(5), 216A-222A.

35. Faust, B. C.; Zepp, R. G. Photochemistry of aqueous iron (III)- polycarboxylate complexes: Roles in the chemistry of atmospheric and surface waters. Environ. Sci. & Tech. 1993, 27, (12), 2517-2522.

36. Zuo, Y.; Hoigne, J., Formation of Hydrogen Peroxide and Depletion of Oxalic Acid in Atmospheric Water by Photolysis of Iron (III)-Oxalato Complexes. Environ. Sci. & Tech. 1992, 26, (5), 1014-1022

37. Hung, H.; Wang, C., Experimental Determination of Reactive Oxygen Species in Taipei Aerosols. J. of Aerosol Sci. 2001, 32(10), 1201-1211.

38. Venkatachari, P.; Hopke, P. K.; Grover, B. D.; Eatough, D. J. Measurement of particle-bound reactive oxygen species in Rubidoux aerosols. J. of Atmos. Chem. 2005, 50(1), 49-58.

39. Chameides,W. L.; Davis,D. D. Aqueous-phase source of formic acid in clouds. Nature 1983, 304(5925), 427-429.

40. Sauer, F.; Limbach, S.; Moortgat, G. K. Measurements of hydrogen peroxide and individual organic peroxides in the marine troposphere. Atmos. Environ., 1997, 31(8), 1173-1184.

41. Hellpointner, E.; Gab, S. Detection of methyl, hydroxymethyl and hydroxyethyl hydroperoxides in air and precipitation. Nature 1989, 33(6208), 631-634.

42. Arellanes, C.; Paulson, S. E.; Fine, P. M.; Sioutas, C. Exceeding of Henry's law by hydrogen peroxide associated with urban aerosols. Environ. Sci. & Tech. 2006, 40(16), 4859-4866. 72 72 43. Sander, R. Compilation of Henry's Law Constants for Inorganic and Organic Species of Potential Importance in Environmental Chemistry 1999. http://www.mpch-mainz.mpg.de/ sander/res/henry.html.

44. Chung, M. Y.; Muthana, S.; Paluyo, R. N.; Hasson, A. S. Measurements of effective Henry's law constants for hydrogen peroxide in concentrated salt solutions. Atmos. Environ. 2005, 39(16), 2981-2989.

45. Lind, J. A.; Kok, G. L. Henry's law determinations for aqueous solutions of hydrogen peroxide, methylhydroperoxide, and peroxyacetic acid. J. of Geophys. Res.: Atmospheres (1984-2012) 1986, 91(D7), 7889-7895

46. Beltz, N.; Jaeschke, W.; Kok, G. L.; Gitlin, S. N.; Lazrus, A. L.; McLaren, S.; Shakespeare, D.; Mohnen, V. A. A comparison of the enzyme fluorometric and the peroxyoxalate chemiluminescence methods for measuring H2O2. J. of Atmos. Chem. 1987, 5(3), 311-322.

47. Faust, B. C., Allen, J. M. Aqueous-phase Photochemical formation of hydroxyl radical in authentic cloudwaters and fogwaters. Environ. Sci. & Tech., 1993, 27(6), 1221-1224.

48. Wang, Y.; Arellanes, C.; Curtis, D. B.; Paulson, S. E. Probing the source of hydrogen peroxide associated with coarse mode aerosol particles in Southern California. Environ. Sci. & Tech. 2010, 44(11), 4070-4075.

49. Faust, B. C.; Allen, J. M. Aqueous‐phase photochemical sources of peroxyl radicals and singlet molecular oxygen in clouds and fog. J. of Geophys. Res. 1992, 97(D12), 12913-12926.

50. Zepp, R. G.; Faust, B. C.; Hoigne, J. Hydroxyl radical formation in aqueous reactions (pH 3-8) of Iron (II) with hydrogen peroxide: The photo-fenton reaction. Environ. Sci. & Tech. 1992, 26(2), 313-319.

51. Squadrito, G. L.; Cueto, R.; Dellinger, B.; Pryor, W. A. Quinoid redox cycling as a mechanism for sustained free radical generation by inhaled airborne particulate matter. Free Radical Bio. and Med. 2001, 31(9), 1132- 1138.

52. Dellinger, B.; Pryor, W. A.; Cueto, R.; Squadrito, G. L.; Hegde, V.; Deutsc, W. A. Role of free radicals in the toxicity of airborne fine particulate matter. Chem. Res. in Toxicology 2001, 14, 1371-1377. 73 73 53. Borg, D. C.; Schaich, K. M.; JJ Jr, E.; Bell, J. A. Cytotoxic reactions of free radical species of oxygen. Photochemistry and Photobiology 1978, 28(4‐5), 887-905.

54. Wang, Y.; Arellanes, C.; Paulson, S. E. Hydrogen peroxide associated with ambient fine-mode, diesel, and biodiesel aerosol particles in Southern California. Aerosol Sci. and Tech. 2012, 46(4), 394-402.

55. Cho, A. K.; Sioutas, C.; Miguel, A. H.; Kumagai, Y.; Schmitz, D. A.; Singh, M.; Eiguren-Fernandez, A.; Froines, J. R. Redox activity of airborne particulate matter at different sites in the Los Angeles basin. Environ. Res. 2005, 99(1), 40-47.

56. See, S.W.; Wang, Y.H.; Balasubramanian, R. Contrasting reactive oxygen species and transition metal concentrations in combustion aerosols. Environ. Res. 2007, 103(3), 317-324.

57. Valavanidis, A.; Salika, A.; Theodoropoulou, A. Generation of hydroxyl radicals by urban suspended particulate air matter. The role of iron ions. Atmos. Environ. 2000, 34(15), 2379-2386.

58. Charrier, J.; McFall, A.; Richards-Henderson, N.; Anastasio, C. Hydrogen peroxide formation in a surrogate lung fluid by transition metals and quinones present in particulate matter. Environ. Sci. & Tech. 2014, 48(12), 7010-7017.

59. Chow, J. C.; Watson, J.G.; Fujita,E.M.; Lu, Z.; Lawson, D.R.; Ashbaugh, L. L. Temporal and spatial variations of PM2.5 and PM10 aerosol in the Southern California air quality study. Atmos. Environ. 1994, 28, 2061-2080.

60. Singh, M.; Jaques, P. A.; Sioutas, C. Size distribution and diurnal characteristics of particle-bound metals in source and receptor sites of the Los Angeles Basin. Atmos. Environ. 2002, 36, 1675-1689.

61. Rashid, M. A., Role of quinone groups in solubility and complexing of metals in sediments and soils. Chem. Geol. 1972, 9(1), 241-247.

62. Vu, K. T. Measurements of redox-active organics in fine particulate matter. California State University, Fresno, 2013.

63. Lyon, J. C. The toxicity of quinones in particulate matter through the production of hydroperoxides under lung-like conditions. California State University, Fresno, 2008. 74 74 64. Kok, G. L.; McLaren, S.E.; Stafflbach, T. A. HPLC determination of atmospheric organic hydroperoxides. J. of Atmos. and Oceanic Tech. 1995, 12(2), 282-289.

65. Lee, M.; Noone, B. C.; O'sullivan, D.; Heikes, B. G. Method for the collection and HPLC analysis of hydrogen peroxide and Cl and C2 hydroperoxides in the atmosphere. J. of Atmos. and Oceanic Tech. 1995, 12(5), 1060-1070.

66. Tisch Environmental. Operations manual PM10 and less high volume air sampler. Tisch Env. http://www.tisch-env.com/.2010

67. Lee, M., Heikes, B. G.; O’Sullivan, D. W. Hydrogen peroxide, organic hydroperoxide, and formaldehyde as primary pollutants from biomass burning. J. Geophys. Res. 1997, 102, 1301-1309. Fresno State

Non-Exclusive Distribution License (to archive your thesis/dissertation electronically via the library’s eCollections database)

By submitting this license, you (the author or copyright holder) grant to Fresno State Digital Scholar the non-exclusive right to reproduce, translate (as defined in the next paragraph), and/or distribute your submission (including the abstract) worldwide in print and electronic format and in any medium, including but not limited to audio or video.

You agree that Fresno State may, without changing the content, translate the submission to any medium or format for the purpose of preservation.

You also agree that the submission is your original work, and that you have the right to grant the rights contained in this license. You also represent that your submission does not, to the best of your knowledge, infringe upon anyone’s copyright.

If the submission reproduces material for which you do not hold copyright and that would not be considered fair use outside the copyright law, you represent that you have obtained the unrestricted permission of the copyright owner to grant Fresno State the rights required by this license, and that such third-party material is clearly identified and acknowledged within the text or content of the submission.

If the submission is based upon work that has been sponsored or supported by an agency or organization other than Fresno State, you represent that you have fulfilled any right of review or other obligations required by such contract or agreement.

Fresno State will clearly identify your name as the author or owner of the submission and will not make any alteration, other than as allowed by this license, to your submission. By typing your name and date in the fields below, you indicate your agreement to the terms of this distribution license.

Embargo options (fill box with an X).

Make my thesis or dissertation available to eCollections immediately upon X submission.

Embargo my thesis or dissertation for a period of 2 years from date of graduation.

Embargo my thesis or dissertation for a period of 5 years from date of graduation.

Sowmya keerthi Tummala

Type full name as it appears on submission

January 27, 2014

Date