Browsing by Author "Farmer, Delphine K., committee member"
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Item Open Access Aqueous atmospheric organic processing: effects of fog and cloud composition(Colorado State University. Libraries, 2016) Boris, Alexandra Jeanne, author; Collett, Jeffrey L., advisor; Farmer, Delphine K., committee member; Kreidenweis, Sonia M., committee member; Pierce, Jeffrey R., committee memberCloud and fog droplets are well-suited venues for organic reactions leading to the formation of suspended particulate matter in the atmosphere. Suspended particulate matter formed through aqueous reactions is called "aqueous secondary organic aerosol" or aqSOA, and can interact with solar radiation and adversely impact human and ecosystem health. Although atmospheric observations and lab simulations have verified the formation of aqSOA, little is known about where and when it occurs in the atmosphere. The organic (carbonaceous) reactions leading to aqSOA formation also degrade chemicals in the atmosphere, impacting the potential health effects of fog water deposited to ecosystems and crops. In the present work, studies are described that approach these aqueous oxidation reactions from field and lab perspectives, capturing both complex and simple experiments. Some results will be presented that capture the dynamics of aqSOA formation from studies of in-situ fog chemistry, but the lack of control over environmental variables in these observations will be highlighted. Lab-based reactions of fog and cloud water will also be presented, which oppositely underscore the missing variables in such simplified lab experiments. Despite the need for more advanced experimental design to quantify aqSOA formation and identify its sensitivities to real atmospheric variables, these field and lab approaches have garnered new insight into some key aspects of aqueous oxidation. Fog at Baengnyeong Island (BYI) in the Yellow Sea of Korea was collected in July 2014. Fog chemistry was exemplary of aged atmospheric components: sulfur was almost entirely oxidized (98.9 to 99.8% was present as S(VI) versus S(IV)), and peroxides, which can serve as oxidants, were depleted. Organic acids at times accounted for >50% of the total organic carbon (TOC) by carbon mass, indicating that organic matter was highly oxidized. Although formic and acetic acids were the most abundant, concentrations of ten out of the 18 organic acids quantified were above 1 μM. Some organic sulfur and organic nitrogen species were additionally observed, which may have formed during aqueous reactions in the fog or in humid conditions as air traveled to BYI. Back trajectories demonstrated that the relative humidities of the air masses arriving at BYI were typically >80%, suggesting that oxidation could have taken place in the aqueous phase. The Southern California coast is frequently foggy during the summer months, but in contrast to BYI, is closer to many atmospheric chemical emissions sources. Fog water was collected at Casitas Pass (CP) near Ventura, California in June 2015. Regional oil drilling and/or refinery emissions influenced the composition of foggy air, as did biogenic and marine emissions. Only 20% of TOC on average was contributed by organic acids, suggesting influence of fresher organic emissions than observed at BYI. After 3-5 hours of foggy conditions, however, organic sulfur and organic nitrogen species were observed, suggesting possible in-fog oxidation. A contrast between the 2015 study and a 1985/6 study demonstrated improved air quality compared to 1985/6, with lower concentrations of anthropogenically derived species (NH4+, NO3-, SO42-, acetate, formate, and formaldehyde), but similar concentrations of naturally derived species (Na+, Cl-, Ca2+, and Mg2+). Lab work involving aqueous oxidation within real cloud water revealed that organic constituents of cloud water caused oxidation reactions to slow due to competition for oxidant. Inorganic species (NH4+, SO42- and NO3-) at concentrations relevant to polluted cloud water did not have a statistically significant effect on oxidation. Mechanisms of oxidation were also surprisingly unaffected by cloud water components: similar low molecular mass organic acids were observed as products of oxidation in pure and cloud water. Oxidation of real cloud water sample constituents in the lab revealed that organosulfate species were produced when sufficient SO42- and organic species concentrations were present. Four fog and cloud water samples were oxidized, demonstrating different oxidation regimes: a BYI fog was clearly more aged such that organosulfate esters were formed; cloud water from Mount Tai, China contained biomass burning and anthropogenic aromatic emissions and produced organic acids similar to those observed from nitrophenol chemical standard oxidations; and fog water from CP containing fresher emissions produced mainly low molecular mass organic acids. The aqueous oxidation of biomass burning emissions collected using a mist chamber resulted in the formation of a variety of low molecular mass organic acids. No apparent structure-activity relationship was observed: aliphatic and aromatic species were oxidized at similar rates when exposed to OH radicals. The degradation of potentially toxic organic nitrogen species as well as net production of semi-volatile organic acid products were observed, demonstrating that in-cloud oxidation of biomass burning emissions likely contributes to the chemical evolution and organic aerosol mass within smoke plumes. Overall, there is still a need for advanced experiment development in the field of aqueous organic atmospheric chemistry. The finding that physical processes obscured effects of aqueous reactions during fog field studies should, likewise, guide future field work toward the concurrent measurement of microphysical parameters and possible development of higher efficiency techniques for droplet collection and/or real-time chemical analyses. However, the combination of bulk reactions and fog studies employed within this thesis has allowed the effects of real fog and cloud water chemistry on aqSOA formation to be demonstrated. The common oxidation products identified under most aqueous atmospheric regimes, including low molecular mass organic acid species, but specific environmental requirements for other products such as organosulfates, should guide future research in identifying molecular tracers of aqSOA and sensitivity studies of aqSOA formation to environmental factors.Item Open Access Assay development for pathogen detection at the point-of-need(Colorado State University. Libraries, 2020) Carrell, Cody S., author; Henry, Charles S., advisor; Farmer, Delphine K., committee member; McNally, Andrew, committee member; Reardon, Kenneth F., committee memberInfectious diseases are responsible for roughly one third of worldwide deaths, which disproportionately occur in low- and middle-income countries. Government health agencies recognize high quality diagnostics as a key tool to slow the spread and reduce the burden of disease in these countries. The same diagnostics that have minimized deaths from infectious disease in developed nations, however, cannot simply be implemented in all locations. Low- and middle-income countries lack the financial resources and infrastructure required to use the sophisticated instruments found in modern hospital laboratories. Instead of relying on current diagnostic technologies to reduce the burden of infectious disease, there is an urgent need to develop new technologies suited for the resource-limited settings they will be used in. The work described in this thesis aims to advance the capabilities of diagnostic sensors for use at the point-of-need. Microfluidic devices have been used for decades to perform complex analysis using compact devices with small sample and reagent volumes. Their portability and low-cost make them ideal candidates for analysis in resource limited settings, but their fabrication is tedious and expensive. To improve the fabrication process, Chapter Two of this thesis describes two methods for simplified 3D-printing of microfluidic devices. The 3D printer and resin used are inexpensive and commercially available and the fabrication process is not limited by the need to remove uncured resin from enclosed channels. Instead, open-faced channels in 3D-printed pieces were silanized and sealed to a secondary substrate. Common microfluidic devices including a droplet generator and herringbone mixer were created with the new fabrication method to demonstrate the strength of the seal and ability for the printer to create microfluidic channels. We envision this method being used for rapid prototyping and increased innovation in the field of microfluidic sensors. Traditional polymer microfluidics are limited in their usefulness in point-of-need situations because they require a pump to drive flow. Paper-based microfluidics use capillary action to drive flow instead of a pump and have emerged as an easy-to-use and inexpensive alternative to traditional microfluidics in situations where a power source is not available. However, paper-based microfluidics often suffer from poor analytical performance, and efforts to improve result in increased complexity. Chapter Three of this thesis describes a paper-based device that increases the sensitivity of a Salmonella assay while retaining ease-of-use. The device combines paper-pads for reagent storage with a 3D-printed rotational manifold to perform an enzyme-linked immunosorbent assay (ELISA). Typically, this assay requires dozens of complex pipetting steps, but the rotary device simplifies this process into four semi-automated steps. A detection limit of 440 colony forming units/mL was found using the paper-based device. As demonstrated in Chapter Three, common issues with paper-based microfluidics can be solved by integrating paper with other inexpensive components like 3D-printed polymer. In the final study in Chapter Four, we created a device to further simplify the steps of an ELISA using a combination of paper, polyester transparency film, and double-sided adhesive. The device, termed a disposable ELISA (dELISA), automatically performed the sequential reagent delivery and washing steps required for a traditional ELISA and require only two end user steps. The dELISA was then used to perform a serology assay for SARS-CoV-2 antibodies from whole-blood. The detection limit of the assay was 2.8 ng/mL for the dELISA, which was nearly identical to the detection limit found using a tradition well-plate assay (1.2 ng/mL).Item Embargo Design and synthesis of metal-organic frameworks for applications in catalyzing organic chemical reactions(Colorado State University. Libraries, 2022) Thai, Jonathan E., author; Reynolds, Melissa M., advisor; Henry, Charles S., committee member; Farmer, Delphine K., committee member; Zabel, Mark D., committee memberMetal-organic frameworks (MOFs) are versatile materials that possess a lot of potential for use as heterogeneous catalysts. Their crystalline structure creates a uniform, well-defined, highly porous framework that has a high density of active sites. Furthermore, their unprecedented tunability has allowed scientists to create several thousands of unique MOF structures. This has made MOFs a prominent area of research as they provide a clear path to move from homogeneous catalysis into heterogeneous catalysis. Heterogeneous catalysts are of utmost importance in the modern chemicals industry, playing key roles in the production of both organic and inorganic compounds. Heterogeneous catalysts help create lower energy pathways that allow for the catalysts to be more easily recovered and recycled (relative to homogeneous catalysts) and can enable more efficient production on large scale chemical production. However, MOFs have yet to be seen in widespread use for this purpose despite the many advantages they possess and the large variety of available MOFs due to their limitations, typically their lack of stability at high temperatures (most MOFs are typically only stable up to temperatures around 350-400°C). This dissertation works towards improving current MOFs for heterogeneous catalysis and using MOFs as heterogeneous catalysis in a continuous flow reactor. Chapter 1 of this dissertation provides a discussion on the background of MOFs, how they are made, their limitations as heterogeneous catalysts, the advantages they bring to the field of heterogeneous catalysis, and some of the key techniques used to characterize MOFs. Chapters 2 and 3 focus on the synthesis and development of CuBDTri (where H2BDTri = 1,4-1H-1,2,3-triazol-5-yl)benzene), the first Cu-based MOF nanosheet (MOFN) that is water stable and shown to be more catalytically active for the release of nitric oxide from S-nitrosoglutathione relative to CuBTTri (where H3BTTri = 1,3,5-tris(1H-1,2,3-triazol-5- yl)benzene). Chapter 2 focuses on how CuBDTri was originally designed, synthesized, and confirmed to be a newly created MOF. Chapter 3 then focuses on the work done to optimize the synthetic process used to make CuBDTri so that the resulting MOFN particles are as thin as possible, maximizing their efficiency as heterogeneous catalysts on a per-total-Cu-atom basis. Chapter 4 originally aimed to develop a continuous flow process using the MOF CuBTC (where BTC = benzene-1,3,5-tricarboxylate) to catalyze the Friedländer synthesis. However, over the course of this work, it was found that the conditions being used to perform the Friedländer synthesis resulted in the breakdown of the CuBTC and so efforts were redirected to determine what caused this breakdown and the identity of the active catalyst in this reaction system. The data provided in this chapter track the breakdown of CuBTC by the Friedländer synthesis and provide evidence towards what the catalyst identity is. Chapter 5 takes what was learned from Chapter 4 to transfer a condensation reaction to produce xanthene derivatives under continuous flow conditions, catalyzed by CuBTC. The results from the work completed here suggest that the reaction is being successfully performed under continuous flow conditions and is producing the desired xanthene. Furthermore, the success of this system provides further insight and understanding towards why CuBTC breaks down in the conditions used for the Friedländer synthesis in Chapter 4 but is stable under the conditions used to perform the condensation reaction in this chapter.Item Open Access Development of mass spectrometry techniques for analysis of biomedical systems(Colorado State University. Libraries, 2020) Tapia, Jesus B., author; Reynolds, Melissa M., advisor; Henry, Charles S., committee member; Farmer, Delphine K., committee member; Kipper, Matthew J., committee member; Zadrozny, Joseph M., committee memberThe advances of modern mass spectrometry (MS) have allowed MS to become one of the essential analytical tools for biological and biomedical research. Mass spectrometry's ability to provide rapid and sensitive analysis of many types of analytes made it an excellent candidate to study the polysaccharide dextran, biodegradable poly(organophosphazene) and polyester derived polymers, as well as interfering species in commonly used cell viability studies. Electrospray ionization time-of-flight mass spectrometry (ESI-TOF MS) was used to analyze the polysaccharide dextran. Polysaccharides, including dextran, are difficult to ionize due to their inherent neutrality. Ionization efficiency is poor in negative polarity ESI because they lack acidic groups typically needed for proton abstraction, and ionization efficiency in positive polarity ESI is poor because polysaccharides have low proton affinity. In efforts to circumvent the issue of low ionization efficiency, dextran was derivatized to try mimicking protein-like ionization. Dextran was derivatized using a one-pot derivatization procedure with ethylenediamine, thus, giving dextran free terminal amine groups. The derivatization procedure attached up to four ethylenediamine groups and allowed dextran to have up to four protonations (or positive charges). The ability to carry up to four charges shifted the molecular weight of dextran to a lower m/z, similar to protein supercharging ionization. Mass spectrometric analysis was successfully applied to identify potential degradation products during the catalytic release of nitric oxide (NO) from S-nitrosoglutathione (GSNO) when it was exposed to metal-organic frameworks (MOFs) embedded onto chitosan polymer support systems. Oxidized glutathione (GSSG) was confirmed to be the reaction byproduct of the release of NO from GSNO, and glucosamine and N-acetylglucosamine were identified as the degradation products from the chitosan polymer support system. In a similar use of MS, potential interferences in the commonly used CellTiter Blue and MTT cell viability assays were studied. When the UV-vis spectroscopic assays suggested interferences or produced inconclusive results, mass spectrometric analyses accurately determined whether selected small molecules were responsible for conversion of resazurin to resorufin, MTT to formazan, or if they were responsible for severe signal suppression on the UV-vis spectroscopic assays. MS was also successfully used to study the biodegradable poly(phosphazene), polyester polymers and their nitrosated analogues. The purpose of the studies was to investigate the potential degradation products from the degradation of these polymers. In-depth understanding of the degradation products from these polymers may aid in determining potential unwanted side effects that may render the polymeric devices unusable. A combination of direct flow injection MS, liquid chromatography mass spectrometry (LC-MS), and tandem mass spectrometry (LC-MS/MS) were successfully applied to identify the degradation products from each polymer system investigated. Identification of each degradation product from these polymers strongly suggests the implementation of LC-MS/MS when biodegradable polymers are developed for biomedical applications. Particularly because these methods can be used when a device intended for medical use undergoes the ISO 10993 series Biological Evaluation of Medical Devices. Additionally, in a highly collaborative effort, a chiral metal-organic framework (MOF) was used as a chiral stationary phase (CSP) for chiral resolution. The chiral-MOF (TAMOF-1) was packed in-house into an empty HPLC column and successfully used to resolve chiral compounds efficiently using normal and reversed phase solvent systems, highlighting the versatility of the chiral-MOF.Item Open Access Development of methods for assessing oxidative stress caused by atmospheric aerosols(Colorado State University. Libraries, 2012) Sameenoi, Yupaporn, author; Henry, Charles S., advisor; Rovis, Tomislav, committee member; Farmer, Delphine K., committee member; Van Orden, Alan K., committee member; Kipper, Matthew J., committee memberExtensive epidemiological studies show strong associations between the exposure to atmospheric aerosol particulate matter (PM) in the size range of 0.1- 10 µm and health problems, including respiratory, atherosclerosis and cardiovascular diseases. However, the mechanisms of PM-induced toxicity are poorly understood. A leading hypothesis states that airborne PM induces harm by generating reactive oxygen species in and around human tissues, leading to oxidative stress. To improve understanding of this effect, methods including biological assays and chemical assays for assessing oxidative stress caused by atmospheric aerosols have been developed and are described in this dissertation. For biological assays, a cleavable tag immunoassay (CTI) was developed with an ultimate goal of measuring multiple oxidative stress biomarkers in a single run. As a proof-of-concept, the multianalyte analysis system CTI was performed in competitive, non-competitive, and mixed formats for detection of small molecules and protein biomarkers simultaneously. For chemical assays, a microfluidic electrochemical sensor and a microfluidic paper-based analytical device (µPAD) have been developed for assessing aerosol oxidative stress in an area-based exposure study and a personal exposure study, respectively. The microfluidic electrochemical sensor was used for assessing aerosol oxidative stress by measuring the oxidative activity. The sensor was coupled directly to a Particle-into-Liquid-Sampler (PILS) to create an on-line aerosol sampling/analysis system. The system offers analysis with 3 minute temporal resolution, making it the best available temporal resolution for aerosol oxidative activity. The sensor was also used to analyze the ability of aerosols to generate hydroxyl radicals as another parameter for assessing aerosol oxidative stress. The ultimate goal of this system is to create an on-line monitoring system using a similar approach for oxidative activity analysis. As a first step toward this goal, assay optimization and system characterization in an off-line format employing flow injection analysis and amperometric detection, were carried out and presented in this dissertation. A microfluidic paper-based analytical device (µPAD) was developed for measuring oxidative activity of aerosol collected by a personal sampler. The system allows analysis with minimal sample preparation and requires 100-fold less particulate matter mass than existing analysis methods.Item Open Access Extreme ultraviolet laser ionization mass spectrometry: probing materials at the micro and nano scales(Colorado State University. Libraries, 2023) Rush, Lydia Alexandra, author; Menoni, Carmen S., advisor; Duffin, Andrew M., advisor; Farmer, Delphine K., committee member; Marconi, Mario C., committee member; Rocca, Jorge J., committee memberThe focus of this dissertation is the use of 50 to 10 nanometer wavelength extreme ultraviolet (EUV) laser light as a next generation probe for mass spectrometry analyses at the micro (>100 nanometers) and nano (≤100 nanometer) spatial scales. While the unique properties of EUV light have revolutionized the semiconductor industry through nanoscale lithography fabrication, the use of EUV lasers with analytical instruments, like mass spectrometers, for high spatial resolution chemical analyses is a relatively untapped area. This unexplored territory is owed partly to only recently bringing EUV lasers to an accessible "bench-top" scale. Herein I show how EUV laser ionization can be used with different types of mass spectrometers as a new route for interrogating nuclear and geologic materials with micro and nano scale lateral spatial resolution. I focus on the application of a compact capillary discharge EUV laser operating at a wavelength of 46.9 nanometers connected to a time-of-flight (TOF) mass spectrometer, called the EUV TOF. I also show for the first time how the 46.9 nm EUV laser ionization source can be connected to a commercial magnetic sector mass spectrometer, called the EUV magnetic sector. Specifically, I demonstrate that the EUV TOF instrument can measure the 235U/238U isotope ratio in 100 nm sized pixels in a heterogeneous uranium fuel pellet that was made by blending different feedstocks together. The results show that the EUV TOF maps similar micrometer sized areas of 235U/238U heterogeneity as nanoscale secondary ionization mass spectrometry (NanoSIMS), indicating that EUV laser ionization can be used to accurately probe complex nuclear materials within the scope of the study. I also show that the EUV TOF can be used to measure 206Pb/238U and 232Th/238U isotope ratios at the 8 µm scale in select geologic matrices of silicates, zircons, monazites, and iron manganese within error (±2σ) using a single non-matrix matched calibration standard. However, the precision on the ratio measurements was low for useful geologic applications, ranging between 1-10% at elemental concentrations exceeding hundreds of ppm because of the limitations of using a TOF for isotope ratio measurements. To this end, I show the current development of the new EUV magnetic sector instrument that uses the EUV laser ionization source with a commercial double-focusing sector-field multi-collector mass spectrometer with the aim of achieving more precise (<1%) and sensitive (≤ppm) isotope ratio measurements at high spatial scales (<10 µm down to the nanoscale). The EUV magnetic sector is being developed to probe more complex isotopic systems in nuclear and geologic materials that was not possible with the TOF mass spectrometer. The work here shows that the 46.9 nm wavelength EUV laser ionization source can be interfaced with Thermo Fisher's commercial sector-field multi-collector mass spectrometer called the Neptune by removing its inductively coupled plasma (ICP) region. The Neptune's ion optics, electric sector, and magnetic sector were modified for acceptance of the pulsed EUV-generated ions. These modifications resulted in ions from ≤2 µm diameter craters created by EUV laser ablation and ionization being successfully focused, separated by mass, and detected using the Neptune's electron multipliers. However, further system upgrades to the Neptune's detectors are needed for accurate isotope ratio measurements at high spatial scales because the 10 to 30 nanosecond wide EUV-generated ion pulses are on the order of the electron multipliers' dead time. With proper detectors, the EUV magnetic sector's accuracy, precision, sensitivity, efficiency, and spatial resolution can be measured in future experiments. The demonstration of the EUV magnetic sector instrument here represents the first time that an EUV laser ionization source has been used with a sector-field mass spectrometer, paving the way for future high spatial resolution isotope ratio analyses.Item Open Access From forests to the remote ocean to smoke plumes: aerosol microphysics in diverse environments(Colorado State University. Libraries, 2020) Hodshire, Anna Lily, author; Pierce, Jeffrey R., advisor; Jathar, Shantanu H., advisor; Collett, Jeffrey L., committee member; Farmer, Delphine K., committee member; Kreidenweis, Sonia M., committee memberTo view the abstract, please see the full text of the document.Item Open Access Investigating contributions to elevated surface ozone in the Colorado Front Range during summer 2015(Colorado State University. Libraries, 2018) Lindaas, Jakob, author; Fischer, Emily V., advisor; Farmer, Delphine K., committee member; Ravishankara, A. R., committee memberTropospheric ozone (O3) is a significant pollutant in the Colorado Front Range. The northern Front Range metropolitan area (NFRMA) has exceeded the U.S. EPA national ambient air quality standard for O3 since 2008. While many regions in the country have experienced downward trends in ground-level O3, the NFRMA O3 mixing ratios have remained stagnant despite efforts to reduce precursor emissions. Rapid population growth and a boom in oil and natural gas development over the past 15 years have changed the quantity and spatial distributions of many important O3 precursors. O3 precursors may also be transported into the NFRMA, such as during wildfire smoke events. Here I use in situ measurements of O3, a suite of volatile organic compounds (VOCs), and reactive oxidized nitrogen species collected during summer 2015 at the Boulder Atmospheric Observatory (BAO) in Erie, CO, to investigate the contribution of different VOC sources to elevated surface O3 in the NFRMA. The first analysis combines observations of acyl peroxy nitrates (APN) and a previously described positive matrix factorization of the VOCs to investigate the contribution of different VOC sources to high O3 abundances at BAO. Based on the ratio of PPN to PAN, I find that anthropogenic VOC precursors dominate APN production when O3 is most elevated. Propane and higher alkanes, primarily from oil and natural gas emissions in the Colorado Front Range, drive elevated PPN to PAN ratios during high O3 events. The percentage of OH reactivity associated with oil and gas emissions is also positively correlated with O3 and PPN/PAN. Lastly, idealized box model simulations are used to probe the chemical mechanisms for these observations. I find that VOC precursor mixtures dominated by oil and gas emissions create abundant and more efficient peroxy radical intermediates compared to mixtures dominated by traffic or biogenic emissions. This work may help guide efforts to control O3 precursors in the NFRMA. The second analysis examines the impact of wildfire smoke on O3 abundances via a case study. Aged wildfire smoke impacted BAO during two distinct time periods during summer 2015: 6 – 10 July and 16 – 30 August. The smoke was transported from the Pacific Northwest and Canada across much of the continental U.S. Carbon monoxide and particulate matter increased during the smoke-impacted periods, along with acyl peroxy nitrates and several VOCs that have atmospheric lifetimes longer than the transport timescale of the smoke. During the August smoke-impacted period, nitrogen dioxide was also elevated during the morning and evening compared to the smoke-free periods. There were nine empirically defined high O3 days during our study period at BAO, and two of these days were smoke-impacted. I examined the relationship between O3 and temperature at BAO and found that for a given temperature, O3 mixing ratios were greater (~10 ppbv) during the smoke-impacted periods. Enhancements in O3 during the August smoke-impacted period were also observed at two long-term monitoring sites in Colorado: Rocky Mountain National Park and the Arapahoe National Wildlife Refuge near Walden, CO. Given that the relative importance of wildfire smoke for air quality over the western U.S. is expected to increase as the climate warms and anthropogenic emissions decline, this case study offers important insights into how aged wildfire smoke can influence atmospheric composition at an urban site.Item Embargo Marine ice nucleating particles: sources, composition, emissions, and model parameterizations(Colorado State University. Libraries, 2023) Moore, Kathryn A., author; Kreidenweis, Sonia M., advisor; DeMott, Paul J., advisor; Farmer, Delphine K., committee member; Pierce, Jeffrey R., committee member; van den Heever, Susan C., committee memberSea spray aerosol has received increasing attention over the last decade as a source of ice nucleating particles (INPs) to the atmosphere. Sparse measurements in remote marine regions indicate both marine INP concentrations and ice nucleating efficiency are several orders of magnitude lower than those of mineral or soil dusts, which dominate the INP budget on a global scale. The Southern Ocean (SO) surrounding Antarctica is thought to be the only region where marine INPs are the predominant INP type due to its remoteness from continental and anthropogenic aerosol sources and persistent strong westerlies, although several recent studies have suggested this may also be true of the high Arctic seasonally or intermittently. INPs are critical for initiating cloud glaciation at temperatures warmer than ~-36 °C and can thus have an outsize effect on cloud phase and related climate feedbacks due to their relative scarcity. This is particularly true over the polar oceans, where low and mid-level mixed phase and supercooled clouds are ubiquitous and especially sensitive to aerosols due to the generally low background particle concentrations. The research presented here aimed to improve our understanding of the factors influencing marine INP emissions and the sources and composition of INPs in remote marine regions, as well as to evaluate and improve current INP model parameterizations. This was accomplished using observations made in the Southern Ocean, one of the few remaining pristine aerosol environments, during the Southern Ocean Cloud Radiation Aerosol Transport Experimental Study (SOCRATES) aircraft campaign on the NSF/NCAR G-V, and the second Clouds, Aerosols, Precipitation, Radiation and atmospherIc Composition Over the southeRN ocean (CAPRICORN-2) ship campaign on the R/V Investigator in 2018. Ambient observations were supplemented by measurements from the CHaracterizing Atmosphere-Ocean parameters in SOARS (CHAOS) mesocosm experiment in the new Scripps Ocean-Atmosphere Research Simulator (SOARS) wind-wave channel. CHAOS measurements allowed for isolation of the role of wind speed in marine INP production, which had not previously been characterized through controlled experiments. SOCRATES and CAPRICORN-2 are notable for collecting the first vertically resolved INP measurements over the Southern Ocean, including the first in situ observations in and above cloud in the region. Both aerosol and INP concentrations showed excellent agreement between G-V and R/V Investigator observations during overflights of the ship, supporting the use of such a multi-platform measurement approach for future campaigns interested in aerosol and INP vertical profiles. New techniques for estimating marine aerosol surface area and the number of particles >0.5 μm, key quantities often used in INP parameterizations, were developed based on lidar and nephelometer measurements. An additional parameterization for marine INPs is proposed, which uses both wind speed and activation temperature, and reduces bias compared to the existing parameterization based solely on temperature. Marine boundary layer (MBL) and above cloud INP concentrations from the same SOCRATES flight support the hypothesis suggested by several modeling studies that marine INPs dominate at low altitudes, and mineral dust becomes increasingly important with height. Unexpectedly, enhanced INP and aerosol iron concentrations, but low iron solubilities, were observed for samples collected south of 60 °S during CAPRICORN-2. Antarctica is suggested as a potential source of both biological and inorganic INPs to the Southern Ocean marine boundary layer through the emission of mineral and soil dusts from ice-free areas. Similar high latitude dust sources in Iceland and Svalbard have been observed to contribute to INPs in the Arctic atmosphere, and are anticipated to increase in importance as the climate warms.Item Open Access The downhole behavior of the chemicals of hydraulic fracturing - an insight to the nature of biocides and surfactants underground(Colorado State University. Libraries, 2016) Kahrilas, Genevieve A., author; Borch, Thomas, advisor; Farmer, Delphine K., committee member; Henry, Charles S., committee member; Blotevogel, Jens, committee memberIn a time period and society surrounded by a surplus of information, there is currently mystery and confusion surrounding the organic chemicals added to hydraulic fracturing ("fracking") fluids. Not only is it unclear what chemicals specifically are being used in some instances, but there is little to no information existing about the transformations these chemicals may undergo once underground ("downhole") and subjected to elevated heat and pressure for the duration of a fracturing operation. Several kilometers downhole, these organic chemicals are exposed to temperatures up to 200 °C, pressures above 10 MPa, high salinities, and a pH range from 5 - 8. Despite this, very little is known about the fate of HFF additives under these extreme conditions. Chemical transformations may directly affect the toxicity of the chemicals as they emerge from the downhole environment with the rest of the "flowback" wastewater. Therefore the following chapters of this dissertation serve to classify existing information and to probe the basic effects of the downhole fracturing environment on chemical stability and transformation. Chapter 1 provides a brief introduction to and rationale for the research presented in the following pages. Some of the general purposes for chemicals within hydraulic fracturing fluids (HFFs) are discussed, as well as some of the reason for the controversy which exists today. Additionally, chapter 1 outlines the research objectives which inspired the original research presented afterwards. Chapter 2 of the dissertation servers as the first existing literature review on the biocides utilized in hydraulic fracturing. Biocides are critical components of hydraulic fracturing ("fracking") fluids used for unconventional shale gas development. Bacteria may cause bioclogging and inhibit gas extraction, produce toxic hydrogen sulfide, and induce corrosion leading to downhole equipment failure. The use of biocides has spurred a public concern and debate among regulators regarding the impact of inadvertent releases into the environment on ecosystem and human health. Chapter 2 provides a review of the potential fate and toxicity of biocides used in hydraulic fracturing operations. Physicochemical and toxicological aspects will be discussed as well as knowledge gaps that should be considered when selecting biocides: (1) uncharged species will dominate in the aqueous phase and be subject to degradation and transport whereas charged species will sorb to soils and be less bioavailable; (2) many biocides are short-lived or degradable through abiotic and biotic processes but some may transform into more toxic or persistent compounds; (3) understanding of biocides' fate under downhole conditions (high pressure, temperature, salt and organic matter concentrations) is limited; (4) several biocidal alternatives exist, but high cost, high energy demands, and/or formation of disinfection byproducts limit their use. Chapter 3 serves as the first research experiment outlining a model for testing the behavior of HFF additives downhole. Here, stainless steel reactors are used to simulate the downhole chemistry of the commonly used HFF biocide glutaraldehyde (GA). The results show that GA rapidly (t1/2 < 1 hr) autopolymerizes, forming water-soluble dimers and trimers, and eventually precipitates out at high temperatures (~140 °C) and/or alkaline pH. Interestingly, salinity was found to significantly inhibit GA transformation. Pressure and shale did not affect GA transformation and/or removal from the bulk fluid. Based on experimental second-order rate constants, this chapter provides a working kinetic model for GA downhole half-life predictions for any combination of these conditions (within the limits researched) was developed. The findings outlined in chapter 3 illustrate that the biocidal GA monomer has limited time to control microbial activity in hot and/or alkaline shales, and may return along with its aqueous transformation products to the surface via flowback water in cooler, more acidic, and saline shales. Chapter 4 builds upon the framework set by chapter 3 to analyze another chemical commonly used in HFFs: nonylphenol ethoxylates (NPEs). NPEs are commonly used as surfactants and corrosion inhibitors in hydraulic fracturing fluids. While known to biodegrade to nonylphenol (NP), a known endocrine disrupting compound, little is known about the fate and mobility of NPEs under the extremes (temperatures, pressures, and salinities) in unconventional reservoirs. Chapter 4 presents evidence of abiotic NPE degradation directly into NP by means of hydrolysis under simulated downhole conditions (100 °C, 20 bar), revealing a previously unrecognized transformation pathway. The effects of both salinity and shale interactions were also studied, indicating that salt (NaCl) drastically accelerated hydrolysis kinetics resulting in a faster and increased production of NP, while shale induced significant sorption. Sorption to colloidal shale may result in transport of the downhole-generated NP to the surface along with the flowback and produced water. The findings presented in chapter 4 suggest that hydraulic fracturing fluids may return via flowback-produced water in a form that is more toxic than what was originally injected. Chapter 5 of the dissertation presents the conclusions of the work presented here as well as future directions for research about downhole behavior of organic chemical additives to HFFs, using this body of work as a platform.Item Open Access The impact of pine beetle infestation on monoterpene emissions and secondary organic aerosol formation in western North America(Colorado State University. Libraries, 2012) Berg, Ashley R., author; Heald, Colette L., advisor; Collett, Jeffrey L., committee member; Farmer, Delphine K., committee memberOver the last decade, an extensive beetle outbreak has impacted western North America resulting in the mortality of over 100,000 km2 of forest throughout British Columbia and the western United States. Climate change has aided the expansion and continuation of this beetle infestation for more than a decade as beetles survive milder winters and expand northward and to higher elevation areas. Studies have been conducted to investigate the impact of this disturbance on forest carbon stocks, beetle-fire interactions, and meteorological variables, as well as to affirm the importance of including beetle infestation in models. In recent years there has been increased interest in the impact of beetle mortality and attack on atmospheric composition. Numerous studies have demonstrated that insect attack can prompt elevated emissions of volatile organic compounds (VOCs) in a variety of plant and tree species, including mountain pine beetle attacking lodgepole pine, the main beetle-host combination in the current outbreak. These enhanced VOC emissions are likely a defense mechanism of the tree, consisting of increasing emissions of compounds that are toxic to the beetles and attract predators of the beetles as well as increasing sap flow to help remove beetles from the trunk. This impact has not yet been modeled; however, beetle attack may have a significant impact on atmospheric composition and air quality in western North America. In this study, we use 14 years of beetle mortality data for 13 beetle species and beetle-induced monoterpene concentration data in the NCAR Community Earth System Model (CESM) to investigate the impact of beetle mortality and attack on monoterpene emissions and secondary organic aerosol (SOA) formation in western North America. Needleleaf vegetation is decreased each year based on the annual mortality data while emissions of certain compounds in needleleaf trees under attack are scaled-up based on recent beetle-induced VOC data for lodgepole pine (pine scenario) and Engelmann spruce (spruce scenario). As the mountain pine beetle has had the most extensive impact on mortality, we compare changes in emissions of VOCs and subsequent SOA formation caused by the mountain pine beetle to changes caused by the other 12 beetles combined. Beetle infestation impacts monoterpene emissions through both decreased emissions as trees are killed off (mortality effect) and increased emissions in trees under attack (attack effect). Regionally, beetle infestation may have a significant impact on monoterpene emissions and SOA concentrations with up to a 4-fold increase in monoterpene emissions and up to a 40% increase in SOA concentrations in some years. Responses to beetle attack can vary greatly over space and time as the areas affected as well as the magnitude of the impact depend on the extent of previous mortality and the number of trees under attack in a year. The model captures highly localized impacts on smaller-scales, while on larger-scales, the cumulative mortality effect often mutes the ongoing attack effect. The mountain pine beetle alone has an impact similar to that of the other 12 beetles combined, and the spruce scenario has an impact 3-4 times greater than the pine scenario due to differences in the magnitude of the observed enhancement in monoterpene emissions. In North America, the pine scenario would likely dominate since lodgepole pine is the main species impacted; however, smaller regions of spruce may see higher localized impacts on monoterpene emissions and SOA concentrations. Placed in the context of OM and PM2.5 IMPROVE network measurements, the changes in SOA concentrations due to beetle attack are in most cases small compared to the large annual and interannual variability in the measurements of total organic aerosol, indicating that most beetle-induced SOA changes are not likely detectable in current observation networks. However, in areas with especially large emissions enhancements (e.g. areas of spruce under attack) and lower variability in measurements of OM, beetle-induced changes in SOA may be observable. Due to the large potential impacts that beetle infestation may have on monoterpene emissions, SOA formation, and degradation of air quality, it is important that beetle infestation be included in future models.Item Open Access Trifluoromethylated fullerenes and polycyclic aromatic hydrocarbons and anaerobically milled silicon nanoparticles(Colorado State University. Libraries, 2015) Castro, Karlee P., author; Strauss, Steven H., advisor; Reynolds, Melissa M., committee member; Farmer, Delphine K., committee member; McCullagh, Martin J., committee member; Ramsdell, Howard S., committee memberWell characterized molecules and materials are essential to understand trends and predict future performance. Fundamental studies provide information about molecular properties which may be useful in other applications such as electronic devices. The focus of this dissertation is the characterization of three different classes of molecules/materials with the goal of understanding the fundamental underlying reasons for any trends observed. The first chapter of this dissertation examines the photophysical properties of C70(CF3)n (n = 8 or 10) molecules. Four of the compounds exhibited quantum yields higher than for any previously reported C70 derivative and three exceeded 0.24, the highest fluorescence quantum yield for any fullerene or fullerene derivative. A difference in the location of only one CF3 group in C70(CF3)8 and C70(CF3)10 isomers resulted in 200-fold and 14-fold increases in fluorescence quantum yields respectively. The isomer of C70(CF3)10 with the highest fluorescence quantum yield (0.68 in toluene) also exhibited the longest fluorescence lifetime (51 ns). Formation of the S1 state in one of the C70(CF3)10 isomers occurred within 0.6 ps and its nanosecond-long decay was monitored by ultrafast transient absorption spectroscopy. Time-dependent density functional theory calculations provide a physically meaningful understanding of the photophysical properties. High fluorescence quantum yields are correlated with high oscillator strengths for the S0→S1 transition, large ΔS1−T1 energy gaps, and small spatial extension of the S0→S1 excitation. The second chapter of this dissertation explores trifluoromethyl derivatives of polycyclic aromatic hydrocarbons (PAH(CF3)n). First, the effects of PAH size and shape on the product distribution are examined. Second, the electronic properties, including reduction potential and gas-phase electron affinity, are examined. Third, the influence of number and orientation of the CF3 groups on the crystalline morphologies of these compounds is explored. Finally, charge-transfer complexes made with PAH(CF3)n molecules mixed with PAHs are prepared and examined spectroscopically and crystallographically. From this work it was determined that when PAHs with 8–10 substitutable carbons are reacted with at least 10 equivalents of CF3I gas the PAH(CF3)n products had n values of 4–6 regardless of the size or shape of the PAH core. The reduction potential and gas-phase electron affinity exhibit a regular, incremental increase as a function of the number of trifluoromethyl groups. The number and position of CF3 groups influences the π-π stacking and crystalline morphologies and typically the more CF3 groups added, the lower the intermolecular overlap. Charge-transfer complexes made from mixing PAH(CF3)n and PAH form mixed stacks in the solid-state and exhibit weak association constants in solution. The third chapter of this dissertation examines the effects of oxygen and aromatic molecules on stirred media milling of silicon. Metallurgical-grade silicon was wet-milled in a stirred media mill to produce nanoparticles. Several milling fluids, additives, and milling parameters have been tested and compared between aerobic and anaerobic milling. It was determined that oxygen and aromatic molecules serve as surface passivating additives and lead to higher specific surface areas, indicating smaller particles. Particle amorphization occurs rapidly in a stirred media mill, within two hours crystallite size is on the order of 2-50 nm regardless of whether surface passivating additives are present. In all milling experiments, even in the presence of oxygen, new Si–C bonds are formed, the most Si–C bonds are formed when aromatic molecules are present during the milling process.Item Open Access Understanding the photochemical evolution of organic aerosol from mobile sources and wildfires(Colorado State University. Libraries, 2021) Akherati, Ali, author; Jathar, Shantanu H., advisor; Pierce, Jeffrey R., advisor; Bond, Tami C., committee member; Volckens, John, committee member; Farmer, Delphine K., committee memberTo view the abstract, please see the full text of the document.