Browsing by Author "Farmer, Delphine, committee member"

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Open Access
Adsorptive separations of phytocannabinoids and pesticides in the liquid phase
(Colorado State University. Libraries, 2022) Cuchiaro, Jamie H., author; Reynolds, Melissa, advisor; Farmer, Delphine, committee member; Chung, Jean, committee member; Reardon, Ken, committee member
To view the abstract, please see the full text of the document.
Open Access
Analysis of multiple new-particle growth pathways observed at the US DOE Southern Great Plains Field Site
(Colorado State University. Libraries, 2016) Hodshire, Anna, author; Pierce, Jeff, advisor; Barsanti, Kelley, committee member; Farmer, Delphine, committee member; Kreidenweis, Sonia, committee member
New-particle formation (NPF) is a significant source of aerosol particles to the atmosphere. However, these particles are initially too small to have climatic importance and must grow, primarily through net uptake of low-volatility species, from diameters 1 nm to 30-100 nm in order to potentially impact climate. There are currently uncertainties in the physical and chemical processes associated with the growth of these freshly formed particles that lead to uncertainties in aerosol-climate modeling. Four main pathways for new-particle growth have been identified: condensation of sulfuric acid vapor (and associated bases when available), condensation of organic vapors, uptake of organic acids through acid-base chemistry in the particle phase, and accretion of organic molecules in the particle phase to create a lower-volatility compound that then contributes to the aerosol mass. The relative importance of each pathway is uncertain and may vary by geographic location and atmospheric conditions. Assessing the relative importance is the focus of this work. The 2013 New Particle Formation Study (NPFS) measurement campaign took place at the DOE Southern Great Plains (SGP) facility in Lamont, Oklahoma, during spring 2013. Measured gas-and particle-phase compositions during these new-particle growth events suggest three distinct growth pathways: (1) growth by primarily organics; (2) growth by primarily sulfuric-acid/ammonia; and (3) growth by primarily sulfuric-acid/bases/organics. To supplement the measurements, we used the particle-growth model MABNAG (Model for Acid-Base chemistry in NAnoparticle Growth) to gain further insight into the growth processes on these three days at SGP. MABNAG simulates growth from (1) sulfuric-acid condensation (and subsequent salt formation with ammonia or amines); (2) near-irreversible condensation from non-reactive extremely-low-volatility organic compounds (ELVOCs); and (3) organic-acid condensation and subsequent salt formation with ammonia or amines. MABNAG is able to corroborate the observed differing growth pathways, while also predicting that ELVOCs contribute more to growth than organic salt formation. However, most MABNAG model simulations tend to underpredict the observed growth rates between 10-20 nm in diameter; this underprediction may come from neglecting the contributions to growth from semi-to-low-volatility species or accretion reactions. Our results suggest that in addition to sulfuric acid, ELVOCs are also very important for growth in this rural setting. We discuss the limitations of our study that arise from not accounting for semi- and low-volatility organics, as well as nitrogen-containing species beyond ammonia and amines in the model. Quantitatively understanding the overall budget, evolution, and thermodynamic properties of lower-volatility organics in the atmosphere will be essential for improving global aerosol models.
Open Access
Applications of superatom theory in metal cluster chemistry
(Colorado State University. Libraries, 2016) Tofanelli, Marcus A., author; Ackerson, Christopher J., advisor; Prieto, Amy L., committee member; Shores, Mathew, committee member; Farmer, Delphine, committee member; Roberts, Jacob, committee member
One of the largest modern scientific debates is understanding the size dependent properties of a metal. While much effort has been performed on understanding metal particles from the top down to much less work has been accomplished from the bottom up. This has lead to a great deal of interest in metal clusters. Metal clusters containing 20 to 200 metal atoms are similar yet strikingly different to both to normal coordination chemistry and continuous bulk systems, therefore neither a classical understanding for bulk or molecular systems appears to be appropriate. Superatom theory has emerged as a useful concept for describing the properties of a metal cluster in this size range. In this model a new set of ‘superatomic’ orbitals arises from the valence electrons of all the metals in a cluster. From superatom theory the properties of a metal cluster, such as stability, ionization energy, reactivity, and magnetism, should depend on valence of the superatomic orbitals, similar to a normal atom. However superatom theory has largely been used to describe the high stabilities of metal clusters with completed electronic configurations. Thus many features of superatom theory have remained largely untested and the extent that the superatom model truly applies has remained in question for many years. Over the past decade increases in synthetic and analytical techniques have allowed for the isolation of a series of stable monodisperse gold thiolate monolayer protected clusters (MPCs) containing from 10 to 500 gold atoms. The wide range in sizes and high stability of gold thiolate clusters provides an instrumental system for understanding superatom theory and the transition from molecular-like cluster to bulk-like system. In the first part of this thesis the effects of the superatomic valence is investigated under superatomic assumptions. Au25(SR)18 (where SR= any thiolate) can be synthesized in 3 different oxidation states without any major distortions to the geometry of the cluster, thus it is possible to test 3 different superatomic configurations for a single cluster. These studies show that the superatom model correctly predicts changes observed in the stability, absorption spectrum, crystal structures, and magnetic susceptibility for each charge state of Au25(SR)18. In addition, the superatom model is shown to also apply to the isoelectronic PdAu24(SR)18 superatomic cluster. This work is discussed in Chapters 2, 3, and 4. The second part of this thesis focuses on the transition from superatomic metal clusters to metal nanoparticles. Au144(SR)60 is studied in order to understand this transition. Although the plasmon is not immediately apparent through linear absorption spectroscopy, a plasmonic feature is observed in transient absorption spectroscopy. This observation in combination with the absence of a HOMO-LUMO gap suggests that Au144(SR)60 can be treated with bulk assumptions. However Au144(SR)60 shows quantized behavior and powder x-ray diffraction reveals that symmetry of the metal core does not represent what is observed in the bulk. Au144(SR)60 appears to show both superatomic and bulk behavior making it an instrumental tool for understanding the transition from superatomic to bulk behavior. This work is discussed in Chapters 2, 5, and 6.
Open Access
Catalytic strategies for enhancing electrochemical oxidation of 1,4-dioxane: TiO2 dark activation and microbial stimulation
(Colorado State University. Libraries, 2016) Jasmann, Jeramy R., author; Borch, Thomas, advisor; Blotevogel, Jens, advisor; Farmer, Delphine, committee member; Neilson, James, committee member; Sanford, William, committee member; Elliot, Michael, committee member
1,4-dioxane, a probable human carcinogen, is an emerging contaminant currently being reviewed by the U.S. Environmental Protection Agency for possible health-based maximum contaminant level regulations. As both stabilizer in commonly used chlorinated solvents and as a widely used solvent in the production of many pharmaceuticals, personal care products, (PPCPs), 1,4-dioxane has been detected in surface water, groundwater and wastewater around the U.S. It is resistant to many of the traditional water treatment technologies such as sorption to activated carbon, air stripping, filtering and anaerobic biodegradation making 1,4-dioxane removal difficult and/or expensive. State-of-the art technologies for the removal of 1,4-dioxane usually apply advanced oxidation processes (AOPs) using strong oxidants in combination with UV-light and sometimes titanium dioxide (TiO2) catalyzed photolysis. These approaches require the use of expensive chemical reagents and are limited to ex situ (i.e. pump and treat) applications. Here, at Colorado State University’s Center for Contaminant Hydrology, innovative flow-through electrolytic reactors have been developed for treating groundwater contaminated with organic pollutants. The research presented in this dissertation has investigated catalytic strategies for enhancing electrochemical oxidation of 1,4-dioxane in flow-through reactors. Two types (abiotic and biotic) of catalysis were also explored: (1) dark, electrolytic activation of insulated, inter-electrode TiO2 pellets to catalyze the degradation of organic pollutants in the bulk solution by reactive oxygen species (ROS), and (2) adding permeable electrodes upstream of dioxane-degrading microbes, Pseudonocardia dioxanivorans CB1190, to pre-treat mixed contaminant water and provide O2 stimulation to these aerobic bacteria. For the abiotic form of catalysis, we characterized the properties of novel TiO2 inter-electrode material, and elucidated the properties most important to its catalytic activity, using 1,4-dioxane as the model contaminant. The TiO2 was novel in its use as an “inter-electrode” catalyst (not coated on the electrode and not used as a TiO2 slurry) and in the mechanism of its catalytic activation occurring in dark (not photocatalysis) and insulated (not typical electrocatalysis) conditions. Further studies were performed using electrochemical batch reactors and probe molecules in order to gain mechanistic insights into dark catalysis provided by detached TiO2 pellets in an electrochemical system. The results of our investigations show that electrolytic treatment, when used in combination with this catalytically active inter-electrode material, can successfully and efficiently degrade 1,4-dioxane. Benefits of catalyzed electrolysis as a green remediation technology are that (1) it does not require addition of chemicals during treatment, (2) it has low energy requirements that can be met through the use of solar photovoltaic modules, and (3) it is very versatile in that it could be applied in situ for contaminated groundwater sites or installed in-line on above-ground reactors to remediate contaminated groundwater. Although, 1,4-dioxane appears to be resistant to natural attenuation via anaerobic biodegradation, some aerobic bacteria have been shown to metabolize and co-metabolize 1,4-dioxane. For example, growth-supporting aerobic metabolism/degradation of 1,4-dioxane by Pseudonocardia dioxanivorans CB1190, has been demonstrated in laboratory studies. However, previous studies showed that this biodegradation process is inhibited by the presence of chlorinated solvents such as 1,1,1-trichlorethane (1,1,1-TCA) and trichloroethene (TCE). This could dramatically impact the success for in situ 1,4-dioxane biodegradation with P. dioxanivorans since chlorinated solvents are common co-contaminants of 1,4-dioxane. Our previous investigations into electrolytic treatment of organic pollutants both ex and in situ showed that effective degradation of chlorinated solvents like TCE was achievable. In addition, the electrolysis of water generates molecular O2 required by the CB1190 bacteria as well. This led us to hypothesize that the generation of O2 could enhance aerobic biodegradation processes, and the concurrent degradation of co-solvents could reduce their inhibitory impact on 1,4-dioxane biodegradation. In flow-through sand column studies presented here, we investigate the electrolytic stimulation of Pseudonocardia dioxanivorans CB1190, with the expectation that anodic O2 generation would enhance aerobic biodegradation processes, and concurrent degradation of TCE would reduce the expected inhibitory impact on 1,4-dioxane biodegradation. Results show that when both electrolytic and biotic processes are combined, oxidation rates of 1,4-dioxane substantially increased suggesting that aerobic biodegradation processes had been successfully stimulated. In summary, the results of this dissertation provide evidence of (1) efficient removal of recalcitrant 1,4-dioxane, especially with the addition of inter-electrode TiO2 catalysts, (2) elucidate possible mechanistic pathways for electro-activated dark TiO2 catalysis, and (3) provide evidence for successful synergistic performance for electro-bioremediation treatment during simulated mixed, contaminant plume conditions.
Open Access
Characterizing the influence of anthropogenic emissions and transport variability on sulfate aerosol concentrations at Mauna Loa Observatory
(Colorado State University. Libraries, 2013) Potter, Lauren E., author; Kreidenweis, Sonia, advisor; Maloney, Eric, committee member; Farmer, Delphine, committee member; Cooley, Daniel, committee member
Sulfate aerosol in the atmosphere has substantial impacts on human health and environmental quality. Most notably, atmospheric sulfate has the potential to modify the earth's climate system through both direct and indirect radiative forcing mechanisms (Meehl et al., 2007). Emissions of sulfur dioxide, the primary precursor of sulfate aerosol, are now globally dominated by anthropogenic sources as a result of widespread fossil fuel combustion. Economic development in Asian countries since 1990 has contributed considerably to atmospheric sulfur loading, particularly China, which currently emits approximately 1/3 of global anthropogenic SO2 (Klimont et al., 2013). Observational and modeling studies have confirmed that anthropogenic pollutants from Asian sources can be transported long distances with important implications for future air quality and global climate change. Located in the remote Pacific Ocean (19.54°N, 155.58°W) at an elevation of 3.4 kilometers above sea level, Mauna Loa Observatory (MLO) is an ideal measurement site for ground-based, free tropospheric observations and is well situated to experience influence from springtime Asian outflow. This study makes use of a 14-year data set of aerosol ionic composition, obtained at MLO by the University of Hawaii at Manoa. Daily filter samples of total aerosol concentrations were made during nighttime downslope (free-tropospheric) transport conditions, from 1995 to 2008, and were analyzed for aerosol-phase concentrations of the following species: nitrate (NO3-), sulfate (SO42-), methanesulfonate (MSA), chloride (Cl-), oxalate, sodium (Na+), ammonium (NH4+), potassium (K+), magnesium (Mg2+), and calcium (Ca2+). An understanding of the factors controlling seasonal and interannual variations in aerosol speciation and concentrations at this site is complicated by the relatively short lifetimes of aerosols, compared with greenhouse gases which have also been sampled over long time periods at MLO. Aerosol filter data were supplemented with observations of gaseous radon (Rn222) and carbon monoxide (CO), used as tracers of long distance continental influence. Our study applied trajectory analysis and multiple linear regression to interpret the relative roles of aerosol precursor emissions and large-scale transport characteristics on observed MLO sulfate aerosol variability. We conclude that observed sulfate aerosol at MLO likely originated from a combination of anthropogenic, volcanic, and biogenic sources that varied seasonally and from year to year. Analysis of chemical continental tracer concentrations and HYSPLIT back trajectories suggests that non-negligible long distance influence from either the Asian or North American continents can be detected at MLO during all seasons although large interannual variability was observed. Possible influence of circulation changes in the Pacific Basin related to the El Niño-Southern Oscillation were found to be both species and seasonally dependent. We further found an increasing trend in monthly mean sulfate aerosol concentrations at MLO of 4.8% (7.3 ng m-3) per year during 1995-2008, significant at the 95% confidence level. Multiple linear regression results suggest that the observed trend in sulfate concentrations at MLO cannot reasonably be explained by variations in meteorology and transport efficiency alone. An increasing sulfate trend of 5.8 ng m-3 per year, statistically significant at the 90% confidence level, was found to be associated with the variable representing East Asian SO2 emissions. The results of this study provide evidence that MLO sulfate aerosol observations during 1995-2008 reflect, in part, recent trends in anthropogenic SO2 emissions which are superimposed onto the natural meteorological variability affecting transport efficiency.
Open Access
Constraining marine ice nucleating particle parameterizations in atmospheric models using observations from the Southern Ocean
(Colorado State University. Libraries, 2020) Moore, Kathryn A., author; Kreidenweis, Sonia, advisor; DeMott, Paul, advisor; Farmer, Delphine, committee member; Pierce, Jeffrey, committee member
The limited anthropogenic and terrestrial aerosol sources impacting the Southern Ocean (SO) make it a unique site to study the production of primary sea spray aerosols (SSA) and their role in modifying cloud properties. Previous observations of low ice nucleating particle (INP) concentrations and recent modeling work support the idea that the SO INP population is dominated by SSA. These marine INPs are hypothesized to strongly influence the lifetime, formation, and optical properties of the supercooled and mixed phase clouds that are common in the region, though direct observational evidence for this is lacking. This study focuses on improving our understanding of INP emissions in the marine boundary layer over the SO, with applicability to other ocean regions, and to provide in situ measurements with which to validate and improve INP parameterizations in global and cloud resolving models. Measurements of INPs and aerosols in the marine boundary layer were made during the Clouds, Aerosols, Precipitation Radiation and atmospherIc Composition Over the southeRN ocean 2 (CAPRICORN-2) study on the R/V Investigator during Jan. - March 2018. An initial focus of this thesis was on increasing speed and reproducibility of processing online INP measurements, as well as improving the determination of statistical significance and uncertainty bounds. Different approaches to parameterizing INPs in models are explored for SO aerosols, including the use of aerosol surface area and number concentrations. With an eye towards augmenting global datasets of INPs, a comparison of particle surface area measurements from four different techniques is presented, for use in developing and testing INP parameterizations for different sources and atmospheric conditions. Surface area concentrations derived from Wideband Integrated Bioaerosol Sensor (WIBS) and nephelometer observations are strongly correlated with direct particle size distribution measurements, and can be used in their stead. Uncertainty bounds for both techniques and a scaling factor for WIBS measurements are provided to aid in these estimates. INP concentrations observed during CAPRICORN-2 are very low across the entire temperature range measured (to -30 °C), even compared to previous measurements of marine-dominated airmasses. Unlike INPs from other sources, Southern Ocean marine INPs appear most correlated with accumulation, rather than coarse mode, particles, and are dominated by submicron particles. Commonly used relationships between coarse mode particle number and total aerosol surface area show no significant correlation with SO INP concentrations, indicating a different functional form or different independent variable may be needed to accurately parameterize marine INPs in models.
Open Access
Development of LC-MS and degradation techniques for the analysis of fungal-derived chitin
(Colorado State University. Libraries, 2020) Allison, Christopher L., author; Reynolds, Melissa M., advisor; Farmer, Delphine, committee member; Bailey, Travis, committee member; Popat, Ketul, committee member
The research contained within this dissertation began with the following question: Can liquid chromatography-mass spectrometry (LC-MS) be used as a screening method for fungal infections? The ensuing projects investigated various aspects of that question, taking a ground-up approach that started with the analysis of the simplest constituents of the biomarkers used, chitin and chitosan. The complexity of the systems investigated was gradually increased, culminating in the extraction and detection of these biomarkers from pertinent fungal cells. Chitin constitutes 10-30% of the mass of filamentous fungi. While not found endogenously, it is the second most abundant naturally-occurring polysaccharide, next to cellulose. Chitin is composed of >50% N-acetylglucosamine (GlcNAc) and D-glucosamine (GlcN). In nature and in numerous applications, chitin can be deacetylated to produce chitosan. Chitosan is the deacetylated (>50% GlcN) counterpart to chitin and is also found in some species of fungi. This dissertation began with the development of electrospray ionization mass spectrometry (ESI-MS) methods to analyze GlcN and GlcNAc, as well as oligomers composed of both residues. The optimization of methods to analyze the components of chitin served as the foundation on which to advance the applicability of these methods. Following method optimization, the ability of mass spectrometry to analyze polymeric chitosan was explored. Detecting polymeric chitosan was determined to be infeasible using ESI-MS; hence, the focus of subsequent studies was turned to the use of degradation studies to generate low molecular weight chemical fingerprints that could be correlated to the presence of chitin and chitosan. The first experiments performed to study the degradation of chitosan evaluated the impact nitrosating conditions have on the structure of chitosan. Both mass spectrometry and spectroscopic methods were used to track the formation of a degradation product, 2,5-anhydro-D-mannose (2,5-AM), to demonstrate that nitrous acid-based conditions induce degradation in polymeric chitosan. Following these experiments, degradation studies were expanded to include a wider range of starting materials. Chitosan polymer was used again, in addition to two chitin polymers with varied degrees of deacetylation. In addition to examining the effect of nitrosating conditions on these polymers, degradation methods were expanded to include hydrochloric acid (HCl), hydrogen peroxide (H2O2), and enzymatic degradation agents (lysozyme, lipase, and hemicellulase). The susceptibility of each polymer to degradation protocols was assessed by ESI-MS or LC-MS analysis of degradation products generated. Results from these studies indicated that HCl, H2O2, HNO2, and lysozyme generate distinct products from chitin and chitosan polymers. Identification of unique chemical fingerprints produced from chitin and its derivatives provided the necessary information to apply these studies to pertinent fungal cells. The final experiments in this dissertation apply cleanup, cell lysis, degradation methods, and LC-MS to identify GlcN produced from Aspergillus niger fungi. Cumulatively, the following research contains a thorough overview of degradation methods for chitin and its derivates, along with the characterization of low molecular weight fingerprints that each protocol generates. ESI-MS or LC-MS methods were used to identify low molecular weight products formed during degradation. Finally, both degradation and LC-MS methods were applied to Aspergillus niger to validate that representative fungal species can be detected using the proposed techniques.
Open Access
Diurnal and seasonal predictability of envelope pressures driving natural infiltration in residential buildings
(Colorado State University. Libraries, 2024) Bledsoe, Dominic, author; Bond, Tami, advisor; L'Orange, Christian, committee member; Farmer, Delphine, committee member
This study examines the dynamics of residential building envelope pressures by predicting and comparing time series site-specific weather conditions at minute-level resolution. Utilizing theoretically established relationships of both stack and wind effects, this research examines the predictability and accuracy of envelope pressures under different weather conditions. When high wind effects are removed, the Mean Absolute Error (MAE) in stack pressure predictions are minimized, typically falling below 0.24 Pa. The use of airport weather data, even after correcting for height difference and terrain, was found to be inconducive to prediction, highlighting the preference for site-specific measurements to enhance prediction accuracy. This research utilizes minute-level data for real-time environmental monitoring, aiming to inform pressurization or integrate predictive models for dynamic indoor air quality management. The findings contribute to the field by offering a practical approach to measuring and predicting residential air exchange rates, providing insights that could lead to improved health outcomes and energy efficiency in homes.
Open Access
Exploration of nitric oxide generation from S-nitrosoglutathione for the advancement of anti-fouling glucose biosensor membrane materials
(Colorado State University. Libraries, 2022) Melvin, Alyssa C., author; Reynolds, Melissa M., advisor; Zadrozny, Joseph, committee member; Farmer, Delphine, committee member; Chen, Thomas, committee member
Blood-contacting medical devices such as implantable glucose sensors suffer from biofouling which limits the lifetime of the device and puts the patient at risk of arterial embolism and infection. Researchers have been developing medical device coatings to address the two causes of surface biofouling: thrombus and biofilm formation. One promising strategy is surface-localized production of nitric oxide (NO), a biomolecule with antithrombotic and antibacterial physiological functions, as a multifunctional therapeutic for biofouling prevention. Because NO is a gaseous free radial with a very short physiological half-life, achieving localized NO generation presents a clear challenge. An innovative approach that will be explored herein is incorporating catalysts on the medical device surface that release NO from endogenous NO sources, S-nitrosothiols (RSNOs). A water stable copper-based metal–organic framework (MOF) CuBTTri, Cu(II) benzene-1,3,5-tris(1H-1,2,3-triazoy-5-yl), has been shown to be an effective catalyst for the generation of NO from RSNOs. Two RSNOs, S-nitrosoglutathione (GSNO) and S-nitroso-N-acetylpenicillamine (SNAP), are commonly used in the development of new NO-generating materials. It is known that RSNOs are susceptible to decomposition by stimuli including heat, light, and trace metal ions which can inadvertently be introduced through basic handling, storage conditions, and experimental setups. Despite their frequent use, there is limited and conflicting literature examining the comparative stability of GSNO and SNAP. In order to accurately characterize and quantify the behavior of NO-generating materials, reliable and robust methods must be developed to prevent spontaneous RSNO decomposition under the desired experimental conditions. In Chapter 2, the comparative stability of GSNO and SNAP was thoroughly examined to inform subsequent experiments in the development of CuBTTri-based anti-fouling materials with RSNOs as the NO source. Though CuBTTri is an effective catalyst for this reaction, solid state material must be immobilized into a flexible, processable scaffold for coating devices. In Chapter 3, the effects of incorporating CuBTTri into a medical grade polyurethane composite material on NO generation is explored. In Chapter 4, the effects of three key parameters of CuBTTri composite materials, MOF particle size, MOF loading, and polymer concentration, on NO generation are evaluated to assess the tunability of these next-generation materials. In Chapter 5, the effects of the CuBTTri/polyurethane composite material on the enzyme function and analytical performance of a glucose biosensor are examined. Though metal ion-promoted NO release from RSNOs is promising strategy for the development of NO-generating materials, the majority of studies focus on copper, and few have surveyed the ability of other common metal ions to produce this effect. Finally, in Chapter 6, NO generation from GSNO by Cu2+ and twenty transition and post-transition metal ions was monitored using NO-selective chemiluminescence-based detection to expand the range of potential metals for the development of NO-based anti-fouling materials.
Open Access
Fire and ice: analyzing ice nucleating particle emissions from western U.S. wildfires
(Colorado State University. Libraries, 2019) Barry, Kevin Robert, author; Kreidenweis, Sonia, advisor; DeMott, Paul, advisor; Barnes, Elizabeth, committee member; Farmer, Delphine, committee member
Wildfires in the western U.S. can have impacts on health and air quality and are forecasted to increase in the future. Some of the particles released from wildfires can affect cloud formation through serving as ice nucleating particles (INPs). INPs are necessary for heterogenous ice formation in mixed-phase clouds at temperatures warmer than about -38 °C and can have climate implications from radiative impacts on cloud phase and by affecting cloud lifetime. Wildfires have been shown to be a potential source of INPs from previous ground-based measurement studies, but almost no data exist at the free tropospheric level that is relevant for cloud formation. The Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) campaign that was conducted in summer 2018 utilized the NSF/NCAR C-130 to sample many smoke plumes of various ages in the free troposphere and aged smoke in the boundary layer. INP measurements were made with the CSU Continuous Flow Diffusion Chamber (CFDC) and with aerosol filter collections to analyze offline with the CSU Ice Spectrometer (IS). The results presented in this thesis indicate a contribution of smoke to the INP number concentration budget over the plume-background air, but much variability exists in concentrations and in INP composition among fires. Treatments of the filter suspensions show a dominant organic influence in all plume filters analyzed while a biological INP population is evident in several cases. For the South Sugarloaf fire, which had a primary fuel of sagebrush shrubland, the highest INP concentrations of the campaign were measured, and the unique INP temperature spectrum suggests lofting of material from uncombusted plant material. Normalization of INP concentrations measured in WE-CAN confirms that smoke is not an especially efficient source of ice nucleating particles, however emissions impacts may still occur regionally. The determination of a Normalized Excess Mixing Ratio (NEMR) of INP emissions for the first time will permit modeling of such impacts, and possible INP in-plume production will be explored in future research.
Open Access
Low-cost analytical tools for compositional analysis of particulate matter
(Colorado State University. Libraries, 2018) Mettakoonpitak, Jaruwan, author; Henry, Charles, advisor; Farmer, Delphine, committee member; Barisas, George, committee member; Volckens, John, committee member
Particulate matter (PM) represents a major health problem to people worldwide, contributing to 4 million deaths annually as reported by the Global Burden of Disease (GBD) study (http://www.healthdata.org). PM toxicity is linked to its chemical composition. The toxic chemical components of PM include trace metals, reactive oxygen species, and organic compounds that cause DNA oxidative damage and/or carcinogenesis in the respiratory and cardiovascular systems. The advanced laboratory instrumentation, normally used for the compositional analysis in PM, hinders people in remote area accessing PM monitoring on time due to large, complicated, and expensive features. Microfluidic paper-based analytical devices (mPADs) allow people in developing countries and remote area get an access to analytical testing in wide-ranging application from pharmaceutical analysis to environmental monitoring. However, analytical performance of mPADs needs to be improved. Electrochemistry, integrated into an mPAD, is able to improve limits of detection (LOD) and selectivity. This dissertation presents two efforts towards developing low-cost, portable, and disposable electrochemical analytical devices for chemical characterization of PM. First, simple electrochemical devices for analyzing trace metals including Zn, Cd, Pb, Co, and Ni in PM are presented. The device was fabricated using stencil-printing on a low-cost polyethylene transparency (PET) sheet to create carbon stencil-printed electrode (CSPE). For simultaneous Zn, Cd, and Pb detection, electrospray deposition of silver nanoparticles (AgNPs) was chosen for electrode modification to enhance electrode performance. An enhanced dispersion of AgNPs on the electrode surface was observed resulting in increase of surface area and better electrochemical performance. In addition, Bi and Nafion were used as co-modifiers to enhance peak current. Finally, acetate buffer (pH 5.0) was found to be suitable to obtain the best limit of detection (LOD) and longest linear operating range. The AgNP/Bi/Nafion-modified CSPE provided LODs of 5.0, 0.5, and 0.1 μg L-1 for Zn, Cd, and Pb detection, respectively. The proposed method was used to measure Zn, Cd, and Pb in PM samples including incense, fly ash, cigarette, and solder. The results from the proposed method for Zn, Cd, and Pb detections were not significantly different from the results measured using ICP-MS (at 95% confidence). Besides the method developed for Zn, Cd, and Pb detection, CSPEs were also used for Co and Ni analysis because these metals can produce reactive oxygen species via Fenton-like reactions. The CSPE for Co and Ni determination was modified with Bi to improve signal. Furthermore, dimethylglyoxime (DMG) was used as a Co(II) and Ni(II) chelator with highly selective chemical precipitation for adsorptive stripping voltammetry. The approach gave LOD of 1.0 and 5.0 μg L-1 for Co and Ni, respectively. Finally, Bi-modified CSPEs were used to determine Co and Ni in aerosol samples. The amount of Co and Ni in the samples determined using the proposed method was not significantly different from the results obtained using ICP-MS at 95% confidence. In addition to metals, other components in PM such as organic compounds are prevalent in PM but their analysis is normally restricted to complicated separation methods. To address this need, the last part of this dissertation focuses on developing a low-cost, high resolution electrophoretic laminated Parafilm-paper devices for further analysis of complicated compositions in PM samples. The essential electrophoretic parameters including Joule heating, electroosmotic flow, and electrophoretic mobility were studied. Colorimetry and fluorescence were used as the detection methods. Method viability was first established using chlorophenol red and indigo carmine dyes. The parameters affecting the separation included paper type, channel width, and applied potential. Addition of an injection valve into the device improved resolution and reduced peak broadening. Moreover, the separation of fluorescein isothiocyanate (FITC) and glutamic acid labeled with FITC was used to demonstrate fluorescence detection. In conclusion, the low-cost methods for PM analysis were proposed with using CSPE to detect Zn, Cd, Pb, Ni and Co and using electrophoresis separation on mPAD prepared for effective complicated compounds analysis in the future.
Open Access
Modeling the formation and composition of secondary organic aerosol from diesel exhaust using parameterized and semi-explicit chemistry and thermodynamic models
(Colorado State University. Libraries, 2017) Eluri, Sailaja, author; Jathar, Shantanu, advisor; Volckens, John, committee member; Pierce, Jeffrey, committee member; Farmer, Delphine, committee member
Laboratory-based studies have shown that diesel-powered sources emit volatile organic compounds that can be photo-oxidized in the atmosphere to form secondary organic aerosol (SOA); in some cases, this SOA can exceed direct emissions of particulate matter (PM); PM is a criteria pollutant that is known to have adverse effects on air quality, climate, and human health. However, there are open questions surrounding how these laboratory experiments can be extrapolated to the real atmosphere and how they will help identify the most important species in diesel exhaust that contribute to SOA formation. Jathar et al. (2017) recently performed experiments using an oxidation flow reactor (OFR) to measure the photochemical production of SOA from a diesel engine operated at two different engine loads (idle, load), two fuel types (diesel, biodiesel) and two aftertreatment configurations (with and without an oxidation catalyst and particle filter). In this work, we will use two different SOA models, namely the volatility basis set (VBS) model and the statistical oxidation model (SOM), to simulate the formation, evolution and composition of SOA from the experiments of Jathar et al. (2017). Leveraging recent laboratory-based parameterizations, both frameworks accounted for a semi-volatile and reactive POA, SOA production from semi-volatile, intermediate-volatility and volatile organic compounds (SVOC, IVOC and VOC), NOx-dependent multigenerational gas-phase chemistry, and kinetic gas/particle partitioning. Both frameworks demonstrated that for model predictions of SOA mass and elemental composition to agree with measurements across all engine load-fuel-aftertreatment combinations, it was necessary to (a) model the kinetically-limited gas/particle partitioning likely in OFRs and (b) account for SOA formation from IVOCs (IVOCs were found to account for more than four-fifths of the model-predicted SOA). Model predictions of the gas-phase organic compounds (resolved in carbon and oxygen space) from the SOM compared favorably to gas-phase measurements made using a Chemical Ionization Mass Spectrometer (CIMS) that, qualitatively, substantiated the semi-explicit chemistry captured by the SOM and the measurements made by the CIMS. Sensitivity simulations suggested that (a) IVOCs from diesel exhaust could be modeled using a single surrogate species with an SOA mass yield equivalent to a C15 or C17 linear alkane for use in large-scale models, (b) different diesel exhaust emissions profiles in the literature resulted in the same SOA production as long as IVOCs were included and (c) accounting for vapor wall loss parameterizations for the SOA precursors improved model performance. As OFRs are increasingly used to study SOA formation and evolution in laboratory and field environments, there is a need to develop models that can be used to interpret the OFR data. This work is one example of the model development and application relevant to the use of OFRs.
Open Access
Observations of acyl peroxy nitrates during the Front Range air pollution and photochemistry éxperiment (FRAPPÉ)
(Colorado State University. Libraries, 2016) Zaragoza, Jake, author; Fischer, Emily V., advisor; Collett, Jeffrey L., committee member; Farmer, Delphine, committee member
The Colorado Front Range is an ozone (O3) nonattainment region. The photochemistry of the region is influenced by emissions from the urban and oil and gas sectors, the complex terrain, and the meteorology. The Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) was a field intensive carried out in the Colorado Front Range during summer 2014 to characterize the regional chemical environment. Acyl peroxy nitrates (PANs) play important roles in atmospheric chemistry, acting as either sinks or sources for nitrogen oxides (NOx) depending on conditions. PANs and other trace gas species were measured at the Boulder Atmospheric Observatory (BAO) during FRAPPÉ. Situated at the southwestern edge of the Denver-Julesburg Basin and 35 km north of Denver, BAO has been the site of multiple field studies aiming to characterize the influence of emissions from the oil and gas sector. Here we focus on an analysis of the PANs measurements from BAO during FRAPPÉ. In particular, we focus on peroxyacetic nitric anhydride (PAN, CH3C(O)O2NO2), peroxymethacrylic nitric anhydride (MPAN, CH2C(CH3)C(O)O2NO2) and peroxypropionic nitric anhydride (PPN, CH3CH2C(O)O2NO2). Mean and maximum PAN mixing ratios (5-minute point) were 275 and 1519 pptv respectively. There were four days during FRAPPÉ where the observed PAN abundance exceeded 1 ppbv. These days were examined using FLEXible PARTicle dispersion model (FLEXPART) back trajectories in order to determine air mass origin. The high PAN days occurred when air masses were recirculating in the region, often under Denver Cyclones. However, a visual inspection of FLEXPART trajectories throughout FRAPPÉ showed that recirculation events in the region occurred on days with high (>1 ppbv), moderate (500 pptv − 1 ppbv), and low (<500 pptv) afternoon PAN mixing ratios. The PPN/PAN ratio observed at the BAO tower during the summer of 2014 was 21%, which suggests anthropogenically enhanced photochemical activity. The ratio was very consistent (R2 = 92%) and not dependent on wind direction, potentially reflecting a lack of variability in regional non-methane volatile organic compound (NMVOC) chemistry. The MPAN/PAN ratio was <5%, indicating that isoprene oxidation had very little influence on photochemistry compared to many other regions in the U.S. The relative abundances of PPN and MPAN were used to estimate the contribution of isoprene oxidation to local O3 production. It was found that the contribution to local O3 from isoprene oxidation was consistently less than 20%. The findings of this study suggest that anthropogenic emissions are the key drivers of PANs and O3 formation in the region.
Open Access
The application of carbon composite electrodes for the analysis of environmental and biological pathogens
(Colorado State University. Libraries, 2023) McMahon, Catherine J., author; Henry, Charles S., advisor; Prieto, Amy L., committee member; Farmer, Delphine, committee member; Geiss, Brian, committee member
Fast, reliable, and accurate detection of heavy metals is crucial in preventing adverse health effects. Heavy metal contamination comes from various human anthropological endeavors, and can leach into water, food, and consumer products such as cosmetics. Electrochemical detection of heavy metals has become a popular alternative to traditional analysis, using highly sensitive spectroscopic techniques. Carbon composite electrodes have been used for electrochemical sensors due to their chemical inertness, large potential window, and resistance to fouling. However, they can often suffer from poor electrocatalytic behavior, resulting in the need for extensive surface modifications. Moreover, traditional carbon composite electrodes have been limited in their pattern-ability and difficultly in fabrication. Thermoplastic electrodes were developed in 2017 to address these needs and are further discussed and characterized in this dissertation for applications towards heavy metal analysis. Overall, this dissertation seeks to use carbon composite electrodes to improve detection efforts for both environmental pollutants (i.e heavy metals) and biological analytes. Chapter 2 introduces the use of stencil-printed carbon electrodes (SPCEs) for the analysis of heavy metals in cosmetic samples from Nepal, Ghana, and Uganda. The approach utilizes a previously developed method and adapts it, expanding its utility. The goal of the work is to develop a method that is capable of screening for heavy metal pollutants outside of traditional laboratory settings. An alternative sample extraction approach is detailed as well as the development of a laboratory standard for heavy metal analysis in cosmetics. In addition to the electrochemical analysis, extensive analysis using inductively coupled plasma optical emission spectroscopy is conducted on the cosmetics samples, to better understand the Pb contamination and matrix complexity of the samples. Chapter 3 focuses on the use of TPEs for the detection of heavy metals. Six formulations of TPEs, with different graphites and polymer binders, are characterized to better understand how the unique surface properties impact the analysis of heavy metals. The detection of Pb is used as a proof-of-concept model. The results illustrate that both the polymer and graphite can have intensive impact on the application of TPEs. Of the various formulations tested, polystyrene and polymethyl methacrylate show promise in detecting heavy metals within relevant ranges. Chapter 4 pivots from heavy metal analysis and investigates the use of SPCEs for the detection of SARS-CoV-2 nucleocapsid protein. With the onset of the COVID-19 pandemic in 2020, my research focus pivoted to address the need to develop reliable, accurate, and fast point-of-care diagnostics for SARS-CoV-2 to help manage the spread of the virus. SPCEs are modified based on an ELISA (enzyme-linked immunosorbent assay) for the electrochemical detection of the N-protein. The assay developed sets the framework for a potential POC diagnostic, while meeting the industry need for fewer false negatives and lower limits of detection. In summary, this dissertation seeks to implement and expand the utility of different kinds of carbon composite electrodes for the detection of heavy metals and biological analytes. The work described in this dissertation sets the framework for improving upon carbon-based electrochemical sensors for environmental and biological sensors. This work provides materials, methods, and fundamental characterization of carbon composite electrodes, and how different surface treatments and modifications can expand their utility in electrochemically sensing applications.
Open Access
Transformation of soil organic matter in forest fire impacted watersheds elucidated by FT-ICR mass spectrometry
(Colorado State University. Libraries, 2022) Bahureksa, William, author; Borch, Thomas, advisor; Farmer, Delphine, committee member; Ackerson, Chris, committee member; Heuberger, Adam, committee member
Soils provide numerous ecosystem services that are essential to life on Earth, including food security, water filtration and purification, and infrastructure for biodiversity. Soil properties (e.g., soil productivity, moisture retention, structure and aggregation, and nutrient supply) that facilitate these services depend on the soil organic matter (SOM), which can be dramatically impacted from ecosystem disturbances such as wildfires. Wildfires can provide benefits to an ecosystem through the cleaning of the forest floor, soil nourishment, and the removal of competitive underbrush. However, wildfires have grown in frequency and severity around the world, and there is great interest in resolving changes to SOM composition under wildfire conditions to secure water resources and recover fire-affected areas. In the following work, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was critically evaluated for the analysis of SOM. Data processing methods for FT-ICR MS were investigated to improve compositional analysis. Laboratory-simulated and field-based burn samples were collected and used to investigate changes to water-soluble fractions over progressive series of fire intensity, burn severity, and burn extent gradients. FT-ICR MS currently achieves the highest mass resolving power in the world, which makes it suitable for the study of complex mixtures with tens of thousands of compounds that are separated by mass on the order of a few electrons. Recent strategies for SOM characterization by FT-ICR MS are critically reviewed, with emphasis on SOM sample collection, preparation, analysis, and data interpretation. Importantly, the range of structures, functionalities, and mass means no technique achieves "complete" characterization, and methods used for processing and visualizing FT-ICR MS spectra can influence representation and interpretation of data. The complexity of DOM and influence of post-data processing was demonstrated by studying the effect of peak-picking threshold (3σ, 4σ, 5σ, and 6σ) on a Suwannee River Fulvic Acid standard measured by a custom 21 tesla FT-ICR mass spectrometer. Applying a 3σ peak-picking threshold revealed an additional 13,000 peaks that could be assigned compared to a 6σ peak-picking threshold with a difference of only 12 ppb root-mean-square mass error. Furthermore, isobaric overlaps differing by as little as the mass of an electron are identified up to m/z 1000, and 18O and 17O isotopologues were assigned for the first time in DOM at 3σ. Ecosystem recovery after wildfires in forested watersheds depends on revegetation and soil microbial communities and is therefore limited by the availability of nutrients. The remaining nutrients and substrate available for microbes depends on specific wildfire intensities and are poorly understood. To investigate SOM byproducts during heating and mechanisms that contribute to pyrogenic organic matter (pyOM) formation and mobilization, water-extractable organic matter was extracted from soils heated at discrete temperatures using laboratory microcosms. Relative to the unburnt control, dissolved organic carbon and nitrogen increased at ≥150°C and decreased when ≥450°C. Nitrogen-containing species predominated mass spectra at temperatures >150°C, and mass difference-based analysis suggested that products formed during heating could be used to model transformations along the Maillard reaction pathway. To investigate the short-term impacts of burn extent on water chemistry and dissolved organic matter (DOM) in fire-affected watersheds, streams originating from catchments of low, moderate, and high burn extent within the area of the Cameron Peak Fire of 2020 were sampled before, during, and after the first large rainstorm following the fire. Water chemistry parameters (DOC, TDN, turbidity) for moderate and high burn extents streams tended to increase during the storm and decrease following the storm in high burn extent streams. Fluorescence indices indicated that low/moderate burn extent streams exhibited an increase in microbially-derived residues compared to high burn extent. While a substantial portion of DOM species between every stream were common between each event and included labile and aromatic residues during the storm, the low burn extent exhibited the most unique aromatic features after the storm. When chlorinating stream samples to simulate drinking water treatment, the total DBPs were greater in streams of moderate/high burn extents compared to low burn extent. When DBP concentrations were normalized to DOC, the DOM introduced during the storm resulted in fewer DBPs, suggesting the increase in DBP formation is due to increased DOM loading overall rather than increased reactivity of the DOM. In total, the work presented here contributes to the mechanistic understanding of the residues produced during SOM heating that can be mobilized and impact water chemistry in fire-affected watersheds.