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Fine and coarse particles were collected for eight weeks during the summer of 1991, at a coastal site (Yaquina Head) and a non-industrial site (Corvallis) in Western Oregon to characterize the aerosol composition and evaluate whether the sites are appropriate for sampling "background" marine air. Concentrations of up to 11 species (S0₄²⁻, NO₃⁻, Cl⁻, Na, Fe, Ni, Pb, Cr, Co, Sb, and CH₃SO₃H) for 95 samples were determined using four chemical analysis techniques. The influences of seasalt and soil dust were identified by analyzing concentrations of Na and Fe in the aerosol samples. Relative elemental composition in fine and coarse fractions indicated that the aerosol composition at Yaquina Head was greatly affected by seasalt. "Seasalt" enrichment factors (relative to Na) indicated that seasalt is the only source of Cl⁻ and SO₄²⁻ in coarse particles at Yaquina Head. In contrast, the seasalt influence was relatively weak at the Corvallis site. "Crustal" enrichment factors suggested that soil dust was not a major source of Na⁺, Cl⁻, or S0₄²⁻ at either site. A simple conceptual model that relies on meteorological conditions was used to identify sampling periods with long range transport from either marine or continental areas as well as local influences. This model suggested that during 61% of the experiment period the aerosols were advected from marine areas. At Yaquina Head, 52% of the sampling periods are associated with the "clean" background air (marine air with no local influences). Thus, Yaquina Head represents a useful location for collecting marine background air from the Pacific Ocean. The chemical composition of the marine background air collected at the Yaquina Head site is similar to that for other remote sites around the world. At Corvallis, "clean" marine background air can occasionally (21%) be collected even though Corvallis is located 64 km from the ocean. / Graduation date: 1993

Given the rapid rise in global mean temperature as a direct consequence of increasing levels of greenhouse gases (GHGs) emissions, various climate geoengineering techniques, for example, solar radiation management (SRM), have been suggested. Often criticized as a distraction from global efforts of removing and reducing GHGs, most notably carbon dioxide (CO2), SRM involves both marine cloud brightening (MCB) and stratospheric aerosol injection (SAI), both of which are based on increasing the Earth’s albedo by seeding aerosols in the marine boundary layer and in the lower stratosphere, respectively. SAI has been explored more extensively in various modeling studies following observations of major volcanic eruptions. A significant loading of sulfate particles, a byproduct of the eruptions, were monitored to cool the Earth’s surface temperature temporarily, albeit with some significant consequences including increasing stratospheric ozone (O₃) depletion and reducing precipitation. For our studies, we solely focused on the application of SAI by studying relevant heterogeneous chemistry of alternative aerosols to sulfate, specifically, calcite (CaCO₃) aerosols, to better understand the aerosols’ unintended impact on stratospheric O3 level. CaCO₃ aerosols, often serve as an idealized proxy for calcium-rich mineral dust, have been modeled to have minimal negative impact on both stratospheric O₃ level, through heterogeneous chemistry, and stratospheric temperature. However, only a few laboratory studies have been done on the heterogeneous chemistry of CaCO₃ aerosols with relevant stratospheric trace gases, such as HNO3 and HCl. These gases play a significant role in O₃ catalytic loss cycles in the stratosphere. Since HNO₃ is a common oxidation product of nitrogen oxides which contribute significantly to urban air pollution, a handful of ambient laboratory studies of CaCO₃ heterogeneous reaction with HNO₃ have been conducted. However, very little is known about CaCO₃ heterogeneous chemistry with HCl. Thus, the modeled impact of CaCO₃ aerosols on stratospheric O₃ so far may not be reliable given the lack of experimentally measured kinetics data. Here we report the results of an experimental study of the uptake of HNO₃ and HCl onto submicron CaCO₃ particles in two different flow reactors. Products and reaction kinetics were observed by impacting aerosolized CaCO₃ onto ZnSe windows, exposing them to the reagent gases at a wide range of concentrations, at 296 K and under dry conditions, and analyzing the particles before and after trace gas exposure using Fourier transform infrared spectroscopy (FTIR). A Ca(OH)(HCO₃ termination layer was detected in the form of a HCO₃¯ peak in the FTIR spectra, indicating a hydrated surface even under dry conditions. The results demonstrate the reaction of HNO₃ with Ca(OH)(HCO₃) to produce Ca(NO₃)2, water, and CO₂. HCl reacted with Ca(OH)(HCO₃) to produce CaCl₂ and also water and CO₂. The depletion of the Ca(OH)(HCO₃)/Ca(CO₃) signal due to reaction with HNO3₃ or HCl followed pseudo-first order kinetics. From the FTIR analysis, the reactive uptake coefficient for HNO₃ was determined to be in the range of 0.013 ≤γ_(HNO₃) ≤0.14, and that for HCl was 0.0011 ≤γ_HCl ≤0.012 within the reported uncertainty. The reaction of HCl with airborne CaCO₃ aerosols was also studied in an aerosol flow tube (AFT) coupled with a quadrupole chemical ionization mass spectrometer (CIMS) under similar conditions to the FTIR study, and γ_HCl was determined to be 0.013  0.001. However, the heterogeneous chemistry of CaCO₃ aerosols at stratospheric conditions is still underexamined. We studied the kinetics of HCl uptake on airborne CaCO₃ aerosols at stratospheric temperature, 207 ± 3 K, by performing experiments under dry conditions. Using the same aerosol generation and characterization method, we coupled a low-temperature flow tube with the CIMS for HCl detection. The reactive uptake coefficient for HCl was measured to be 0.076 ± 0.009. This exceeds the reactive uptake coefficient of 0.013 ± 0.001 that we previously reported for this system at 296 K, consistent with the expected negative temperature dependence of gas uptake on solid surfaces. This finding suggests an initial strong reactive uptake of HCl gas on CaCO₃ aerosol surfaces in the stratosphere. Following the most recent modeling studies, our initial kinetic results suggest that the reactions of HCl and HNO₃ with CaCO₃ in the stratosphere could lead to a O₃ column change between -5% and +25%. This wide range of O₃ impact highlights the high uncertainties in estimating the true atmospheric impact of CaCO₃ aerosols, the most well-studied proposed SAI aerosols after sulfate, upon its release into the stratosphere. Nevertheless, our kinetic study establishes a good experimental standard for studying airborne aerosol heterogeneous chemistry under stratospheric conditions as a necessary step to evaluate SAI as a realistic method to battle global warming.

This thesis characterizes the ambient fine organic carbon aerosol and investigates its sources through the development and deployment of new measurement techniques. The focus is on organic compounds that are soluble in water (WSOC), which comprise a large fraction of the organic aerosol, yet little has been known about its chemical nature. A method was developed for quantitative on-line measurements of WSOC by using a Particle-into-Liquid Sampler (PILS) to capture ambient particles into a flow of purified water, which is then forced through a liquid filter and the carbonaceous content quantified by a Total Organic Carbon (TOC) analyzer. This system allows for a continuous 6 minute (ground-based) or 3 s integrated measurement (airborne) with a limit of detection of 0.1 microgramsC/m3 and uncertainty of 10%. Furthermore, a new quantitative method was developed to group speciate the WSOC. In the first step, WSOC is separated by use of XAD-8 resin into its hydrophilic (WSOCxp) and hydrophobic (WSOCxr) fractions. This separation can be performed on-line by coupling the XAD-8 column with the PILS-TOC or off-line on WSOC extracted from integrated filter samples. If off-line, a second step involving size-exclusion chromatography (SEC) is used to chromatographically separate by organic functional groups the WSOCxp and recovered hydrophobic fraction (WSOCxrr). During this step, the WSOCxp is further separated into aliphatic acids with less than four carbons, neutrals, and bases. The WSOCxrr can be separated into acids and neutrals. Results showing the capabilities of the PILS-TOC both on the ground at the St. Louis Midwest Supersite and when airborne during the New England Air Quality Study/Intercontinental Transport and Chemical Transformation 2004 mission conducted in the northeastern U.S. will be presented. Ambient results from urban sites where a PILS-TOC was coupled with a XAD-8 column will be discussed. Data from the two-step speciation performed on samples collected from urban Atlanta summer and winter, and biomass burning in rural Georgia in a region of prescribed burning are presented. Finally, WSOC measurements obtained in Atlanta and its surrounding regions from both the speciation measurements and PILS-TOC will be used to investigate the sources of WSOC in the southeastern U.S.

Sze Sai-tim. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 77-82). / Abstracts in English and Chinese. / Acknowledgment --- p.i / Abstract (English) --- p.ii / Abstract (Chinese) --- p.iii / List of Figures --- p.iv / List of Tables --- p.v / Chapter 1. --- INTRODUCTION / Chapter 1.1 --- Air pollution in Hong Kong --- p.1 / Chapter 1.2 --- Chemical speciation of carbon in air particulates --- p.3 / Chapter 1.3 --- Carbonaceous compounds in air and their harmful effects --- p.6 / Chapter 1.4 --- Review of analytical techniques for carbon determination --- p.14 / Chapter 1.5 --- Research objective --- p.18 / Chapter 1.6 --- Brief description of the project --- p.20 / Chapter 2. --- INSTRUMENTATION AND THEORY / Chapter 2.1 --- Thermal-optical-FID method --- p.21 / Chapter 2.2 --- Combustion-NDIR method --- p.27 / Chapter 2.3 --- Comparison between two methods --- p.28 / Chapter 2.4 --- Materials used for preparing standards --- p.30 / Chapter 2.5 --- Filter media for thermal analysis of carbon containing aerosols --- p.31 / Chapter 3. --- EXPERIMENTAL / Chapter 3.1 --- Instrumentation --- p.33 / Chapter 3.2 --- Apparatus --- p.33 / Chapter 3.3 --- Reagents --- p.35 / Chapter 3.4 --- Analysis time and operation temperature --- p.36 / Chapter 3.5 --- Procedures --- p.38 / Chapter 4. --- RESULTS AND DISCUSSION / Chapter 4.1 --- Particulate matter concentration in air --- p.43 / Chapter 4.2 --- Calibration --- p.43 / Chapter 4.3 --- Recovery study of total carbon in Standard Reference Material --- p.47 / Chapter 4.4 --- Study of filter deposit homogeneity --- p.50 / Chapter 4.5 --- Determination of total carbon in air particulates --- p.52 / Chapter 4.6 --- Further comparison of two methods by determination of total carbon in different sample type (river suspended solids) --- p.61 / Chapter 4.7 --- Repeatability of time of evolution and quantity of carbon determined by thermal optical-FID --- p.70 / Chapter 4.8 --- Reproducibility of measuring total carbon in PM2 5 and PM10 --- p.73 / Chapter 5. --- CONCLUSION --- p.75 / Chapter 6. --- REFERENCES --- p.77

Poon Lok-man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 126-128). / Abstracts in English and Chinese. / ABSTRACT --- p.ii / ACKNOWLEDGEMENT --- p.v / LIST OF TABLES --- p.vi / LIST OF FIGURES --- p.vii / GLOSSARY --- p.viii / Chapter CHAPTER 1: --- INTRODUCTION --- p.1 / Chapter CHAPTER 2: --- AIR POLLUTANTS AND ENVIRONMENTAL MONITORING --- p.8 / Chapter CHAPTER 3: --- PRINCIPLE OF LEAD FINGERPRINTING --- p.15 / Chapter CHAPTER 4: --- INSTRUMENTATION AND THEORY --- p.20 / Chapter CHAPTER 5: --- OPTIMIZATION OF ANALYTICAL PERFORMANCE IN LEAD ISOTOPE ANALYSIS --- p.29 / Chapter CHAPTER 6: --- DETERMINATION OF LEAD CONTENTS AND ISOTOPIC RATIOS IN POTENTIAL AIRBORNE LEAD SOURCES --- p.55 / Chapter CHAPTER 7: --- DETERMINATION OF LEAD CONTENT IN PARTICULATES COLLECTED ONTO HV-FILTERS --- p.69 / Chapter CHAPTER 8: --- ENVIRONMENTAL SURVEY --- p.74 / Chapter CHAPTER 9: --- "CONCLUSIONS, LIMITATIONS AND FURTHER DIRECTION" --- p.97 / APPENDICES --- p.105 / BIBLIOGRAPHY --- p.126