Browsing by Author "Borch, Thomas, advisor"
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Item Open Access Assessment of water quality, toxicity and treatment strategies downstream of NPDES oil and gas produced water discharges intended for beneficial reuse(Colorado State University. Libraries, 2019) McLaughlin, Molly Cook, author; Borch, Thomas, advisor; Blotevogel, Jens, advisor; Argueso, Juan Lucas, committee member; Mouser, Paula, committee member; Sale, Tom, committee memberProduced water is the largest waste stream associated with oil and gas operations. This complex fluid contains petroleum hydrocarbons, heavy metals, salts, naturally occurring radioactive materials (NORMs) and any remaining chemical additives. In the United States, west of the 98th meridian, the federal National Pollutant Discharge Elimination System (NPDES) exemption allows release of produced water for agricultural beneficial reuse if it is of "good enough quality." Due to the complex and variable composition of produced water as well as the variations in permit effluent limits and treatment approaches, the downstream impacts of NPDES produced water releases are not fully understood. The goal of this dissertation was to determine if the current NPDES produced water permit effluent limits are adequate and if not, to identify additional steps that can be taken to improve water quality. As a first step towards this goal, a detailed chemical and toxicological analysis was conducted on a stream composed of produced water released for agricultural beneficial reuse. Over 50 geogenic and anthropogenic organic chemicals not specified in the effluent limits were detected at the discharge including hydrocarbons, halogenated compounds, and surfactants. Most were removed within 15 km of the discharge due to volatilization, biodegradation, and sorption to sediment. Additionally, the attenuation rate increased substantially in a wetland downstream of the discharge point. Tens of inorganic species were also detected in the watershed, including many sourced from produced water. In contrast to organic chemicals, the concentrations of most inorganic species increased downstream due to water evaporation. This included contaminants of concern such as boron, selenium and total dissolved solids (TDS). An assessment of regulatory health thresholds revealed that eight of the organic species detected at the discharge were listed by the U.S. Environmental Protection Agency (EPA) and the International Agency for Research on Cancer (IARC) to be known, probable or possible carcinogens. Mutagenicity of this water was assessed using a yeast mutation assay that analyzed copy number variation (CNV) duplications, CNV deletions, forward point mutations and reversion point mutations. These mutations are established as having a role in human disease, including cancer. Higher rates of mutation were observed at the discharge point and decreased with distance downstream. This correlated with the concentrations of known carcinogens detected in the stream including benzene and radium. Mutation rate increases were most prominent for CNV duplications and were higher than mutation rates observed in mixtures of known composition containing all detected organic carcinogens in the discharge. In addition, samples were evaluated for acute toxicity in Daphnia magna and developmental toxicity in zebrafish (Danio rerio). Acute toxicity was minimal, and no developmental toxicity was observed. Finally, in response to the observation that attenuation of organic chemicals increased in wetlands, constructed wetlands downstream of three different NPDES produced water discharges, including the discharge of focus in the chemical and toxicological analysis, were evaluated for their viability to polish produced water. The results showed that wetlands are effective at attenuating commonly used non-ionic surfactants, as well as a commonly used biocide. Attenuation was not only due to degradation, but also accumulation in sediments. Sediment accumulation has the potential to limit the lifetime of the wetlands or increase the frequency with which sediment must be excavated. The results of this dissertation identified multiple improvements that can be made to NPDES produced water regulations. Current regulations apply to the discharge site only. This dissertation shows that downstream changes in water quality must be considered to adequately evaluate potential impacts of produced water discharges, as exemplified by the increasing concentrations of inorganic species downstream. Secondly, toxicological results showed that chemical analysis alone is insufficient to assess impacts of these releases and that a thorough assessment of chronic toxicity is necessary to fully assess produced water for beneficial reuse. Current regulations require acute toxicity testing, but no assessment of chronic toxicity. Finally, prior to widespread implementation of constructed wetlands for produced water treatment, additional research is needed to assess the impact of oil and gas chemical additives on the maintenance schedules of these systems, as well as the long-term impact to soil health. If these waters can be reused safely and economically, many stakeholders stand to benefit. If this practice is expanded prematurely, the quality and health of water, soil, crops and downstream users could be negatively impacted. The research contained in this dissertation is one step in a life-cycle analysis of the costs, impacts and benefits associated with oil and gas extraction.Item 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 member1,4-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.Item Open Access Degradation and transport pathways of steroid hormones from human and animal waste(Colorado State University. Libraries, 2010) Yang, Yun-Ya, author; Borch, Thomas, advisor; Davis, J. G. (Jessica Gwyn), 1962-, committee member; Barbarick, Kenneth Arthur, committee member; Goodridge, Lawrence David, 1971-., committee memberSteroid hormones have been widely detected in various environmental matrices, including soils, groundwater, surface water, and sediments. Agricultural operations where manure and biosolids are applied as fertilizers and soil amendments are potential sources of steroid hormones to the environment. The aim of this research is to assess the potential for surface runoff and to elucidate biodegradation pathways of steroid hormones from human and animal waste, respectively. A field-scale study was conducted to assess the potential for runoff of seventeen different steroid hormones from an agricultural field applied with biosolids at an agronomic rate and the major runoff mechanisms. Steroid hormones were present in runoff from the biosolids amended agricultural field, and high concentrations of androgens and progesterone were observed in the runoff even after multiple rainfall events and up to one month after biosolids application. The observed correlation between rainfall amount and hormone mass flux suggests that intense rainfall promotes hormone runoff. Hormones were found to be transported primarily in the aqueous phase or by particles smaller than 0.7 µm. The potential for biodegradation of testosterone, 17β-estradiol and progesterone by swine (Sus scrofa) manure-borne bacteria was examined, and the impact of different environmental factors on testosterone degradation kinetics was determined. Testosterone, 17β-estradiol and progesterone were rapidly degraded under aerobic conditions, and testosterone has the potential for degradation by manure-borne bacteria under a wide range of environmentally relevant conditions. Finally, a study was conducted to enrich manure-borne bacteria capable of testosterone degradation and to elucidate the testosterone mineralization pathway by the enriched bacteria under aerobic conditions. Six DNA sequences of bacteria from the Proteobacteria phylum were identified in a testosterone-degrading enriched culture, suggesting that Proteobacteria may play an important environmental role in the degradation of testosterone and other similar structural compounds. The microbial enrichment caused 48% of the added 14C-testosterone to be mineralized to 14CO2 within 8 days of incubation. The findings in this dissertation contribute important information that will help improve our current understanding of the environmental fate of steroid hormones as well as assist in the development of best management practices for biosolids and manure.Item Open Access Determination of spatial distribution, dissipation, and efficacy of insecticides used for control of citrus greening disease(Colorado State University. Libraries, 2022) Rehberg, Rachelle Anne, author; Borch, Thomas, advisor; Henry, Chuck, committee member; Bailey, Travis, committee member; Trivedi, Pankaj, committee memberCitrus greening disease has devastated citrus production globally. While Florida growers explore management strategies, Asian citrus psyllids (ACP) continue spreading this detrimental disease. Determining the efficacy of insecticides applied in citrus groves is a necessity. In these field studies, the efficacies of foliar insecticide treatments to citrus trees were investigated with liquid chromatography tandem mass spectrometry. Insecticide spatial distribution, dissipation, degradation, and effectiveness at reducing ACP were quantified over time after commercial application at a field site in Florida. Citrus leaves, and sample discs attached to leaves, were collected at specific times and locations within individual citrus trees. ACP were inspected before and after treatments to quantify reductions associated with insecticide concentrations over time. We investigated several insecticides commonly used against ACP including malathion, imidacloprid, dimethoate, and one newer insecticide, afidopyropen. Our findings showed highly variable spatial distribution of insecticides throughout individual trees and rapid dissipation within 24 hours after application. Inadequate distribution to different sides of the leaf and tree canopy areas was observed for all aerial and ground spraying methods tested. Fast degradation rates were observed in sampling discs and citrus leaves with half-lives ranging from 0.6 to 4.0 hours while metabolite concentrations increased. Results showed faster dissipation rates during warmer months (July) and in younger-aged trees ground sprayed with the speed-sprayer. A wide range of insecticide efficacy was observed, with ACP reductions of 63 to 100%. When ACP remained after treatment, effectiveness decreased over time and ACP increased (e.g. from 6 to 172% after afidopyropen treatment). The observed variable spatial distribution, rapid insecticide dissipation, and inadequate efficacy allow remaining ACP or ACP from surrounding groves to continue spreading citrus greening disease, leaving citrus trees unprotected. For contact, or semi-systemic insecticides like afidopyropen, full coverage to both sides of the leaves and tree canopy is crucial to effectively manage ACP populations. ACP regeneration suggests lower metabolite toxicity or pest resistance development and reveals ineffective pest management. This research not only helps inform citrus growers of actual insecticide efficacy in the field, which may influence their pest and disease management strategies, but also provides better understanding of insecticide dissipation from citrus leaves, which assists those advancing predictive models for agricultural applications. Additionally, these results help inform insecticide manufacturers of their products' performance in field conditions which can be compared to laboratory studies. Lastly, this work reveals information on the fate of insecticides in the field which could be used to evaluate its impact on other species and the environment.Item Open Access Developing paper-based devices for mapping agricultural pesticides and environmental contaminants(Colorado State University. Libraries, 2021) Menger, Ruth F., author; Henry, Charles S., advisor; Borch, Thomas, advisor; Ravishankara, A. R., committee member; Neilson, James R., committee member; Trivedi, Pankaj, committee memberThe detection of environmental contaminants is important to ensure the health of both humans and the environment. Currently, detection is done by instrumentation like liquid or gas chromatography coupled with mass spectrometry. While sensitive and selective for multiple analytes, these instruments suffer from disadvantages like large size, high sample cost, and the need for a trained analyst to run the samples. As an alternative, microfluidic paper-based analytical devices (µPADs) are becoming more common as inexpensive, fast, easy to use devices to detect and quantify a variety of analytes. My research has been focused on developing µPADs for three different analytes: pesticides, PFAS, and heavy metals. In order to ensure proper crop protection and pest management, it is important to manage and optimize pesticide application. Currently, this is done by water-sensitive papers, which often inaccurately portray the presence of pesticide due to humidity and extraneous water droplets that are not pesticide. In Chapter 2, I have developed a method that uses filter paper to capture a fluorescent tracer dye that has been mixed with the pesticide and then sprayed over the crop. The filter papers are imaged with a lightbox and Raspberry Pi camera system and then analyzed to determine percent coverage. After optimization and validation of the method to WSP, the filter paper method was used to evaluate pesticide distribution in a citrus grove in Florida (Chapter 3). The data from these field studies was used to make recommendations for which application method is best for the different types of pesticides. Paper-based devices are inherently limited by the inability to control fluid properties like mixing. In order to incorporate mixing but also retain a small device that does not require external power to initial flow, a microfluidic device was fabricated out of two glass slides. A staggered herringbone pattern is laser ablated into the slides, and a channel is formed by double-sided adhesive (Chapter 4). Mixing was quantified using blue and yellow dyes. A reaction between horseradish peroxidase and hydrogen peroxide was used as a representative enzymatic reaction and also to determine enzyme kinetics. Since the microfluidic device is made of glass, it is also compatible with non-aqueous solvents. Paper-based devices do not work well with organic solvents because the hydrophobic wax on the paper is dissolved by the solvent. In Chapter 5, the dissertation returns to traditional µPADs for environmental contaminants. Per- and polyfluoroalkyl substances (PFAS) are class of compounds that are highly persistent, toxic, bioaccumulative, and ubiquitous. While multiple instrument-based methods exist for sensitive and selective detection in a variety of matrices, there is a huge need for a fast, inexpensive, and easy-to-use sensor for PFAS detection. This would enable widespread testing of drinking water supplies, ensuring human health. A µPAD was developed for the detection of perfluorooctane sulfonate (PFOS) where the ion-pairing of PFOS and methylene green forms a purple circle. The diameter of the purple circle can be measured by the naked eye with a ruler or with the help of a smartphone to correlate the diameter back to PFOS concentration. At a cost of cents per sample, this µPAD enables fast and inexpensive detection of PFOS to ensure safe drinking water. A common issue with environmental µPADs is the relatively high limits of detection compared to what is needed for regulatory purposes. It can be challenging to lower the limits of detection without incorporating an external pretreatment and/or preconcentration step. As µPADs are small and handle only a small volume of sample (<120 µL), there is the possibility of increasing the sample capacity of the device but without significantly increasing the device size or analysis time. By adding multiple layers of absorbent filter paper underneath radial device for heavy metal detection, the sample volume increased to 1 mL, decreasing the limit of detection for a radial copper detection card from 100 ppb to 5 ppb (Chapter 6). The research presented here achieves the goal of developing µPADs for environmental contaminants. They can be used in different ways to visualize the presence of the contaminant for monitoring and management purposes, ultimately ensuring human and environmental health.Item Open Access Environmental fate of hydraulic fracturing fluid additives after spillage on agricultural topsoil(Colorado State University. Libraries, 2016) McLaughlin, Molly C., author; Blotevogel, Jens, advisor; Borch, Thomas, advisor; DiVerdi, Joseph, committee memberInadvertent releases of hydraulic fracturing fluid may occur at many different stages, with surface spills being the most commonly reported cause of contamination. Hydraulic fracturing (HF) frequently occurs on agricultural land, where surface spills have the potential to impact soil, groundwater and surface water quality. However, the extent of sorption, transformation, and interactions among the numerous organic HF fluid and oil & gas wastewater constituents upon environmental release is hardly known. Thus, this study aims to advance our current understanding of processes that control the environmental fate and toxicity of commonly used hydraulic fracturing chemicals with a specific focus on co-contaminant effects. Hydraulic fracturing fluid releases were simulated using aerobic batch studies conducted with a topsoil collected from Weld County, Colorado, an area where reservoirs are frequently stimulated. Each batch reactor contained varying combinations of the biocide glutaraldehyde (GA), polyethylene glycol (PEG) surfactants, and a polyacrylamide (PAM)-based friction reducer, three widely used hydraulic fracturing fluid components. Furthermore, the presence of salt was investigated in the experiments, often present at high concentration in produced water from hydraulic fracturing operations. Results showed that aqueous GA concentrations decreased by as much as 40% in the first three days of the experiment as a result of sorption to soil. Complete biodegradation of this biocide occurred in all reactors in 33 to 57 days, with the slowest removal occurring in the reactor containing salt. The fastest removal of GA was observed in the reactors containing PAM friction reducer, where degradation rates increased by 50% as compared to reactors without PAM. This increase in removal is attributed to the cross-linking reaction between GA and primary amine functional groups in the friction reducer. In the absence of GA and salt, PEG surfactants were completely biodegraded in agricultural topsoil within 42 to 71 days. Their transformation was impeded, however, in the presence of the biocide GA, and completely inhibited in the presence of 30 g/L sodium chloride, a concentration in the typical range for oil and gas wastewater. No aqueous removal of PAM was observed over a period of six months. However, adenosine triphosphate (ATP) concentrations were consistently higher in reactors containing PAM friction reducer, suggesting this additive supplied an easily accessible source of nitrogen to the microbial soil community. The findings of this study highlight the necessity to consider co-contaminant effects when we evaluate the risk of frac fluid additives and oil and gas wastewater constituents in agricultural soils in order to fully understand their human health impacts, likelihood for crop uptake, and potential for groundwater contamination.Item Open Access Evaluating the effects of fire on carbon and nitrogen biogeochemistry in forested ecosystems(Colorado State University. Libraries, 2023) Roth, Holly, author; Borch, Thomas, advisor; Henry, Chuck, committee member; Reynolds, Melissa, committee member; Prenni, Jessica, committee member; Wilkins, Mike, committee memberForests provide ecosystem services (e.g., carbon storage, nutrient processing, and water filtration) valued at ~$5 trillion per year which are vulnerable to disturbances such as wildfire. Although fires are a natural component of healthy forests, climate change has begun to increase the size, frequency, and severity of wildfires outside of their historic range. Expected increases in burn severity have implications for carbon (C) and nitrogen (N) cycling, with the potential to shift forests from C sinks to C sources due to long delays in tree re-establishment. There is great interest in resolving changes to soil organic matter (SOM) composition, especially organic nitrogen, to predict how forests respond to wildfires. Therefore, the purpose of the work included in this dissertation was to improve nitrogen analysis in fire-impacted forest systems and apply these methods to soil and water samples. In the following work, a suite of advanced analytical approaches were used to determine the molecular composition of SOM, which was evaluated for the impacts of severe wildfires on microbially-mediated SOM processing and water quality in fire-impacted watersheds. Field-based soil and water samples were collected from subalpine forests in the Colorado Rocky Mountains and investigated for shifts in the water-soluble and solid fractions of SOM in lodgepole pine-dominated forests and their influence on microbial processing and water quality was determined. The objectives of this study were to leverage ultrahigh mass spectrometry to improve N analysis in fire-impacted systems (Objective 1), determine the post-fire changes to surface water C and N chemistry in reducing conditions (Objective 2) and to characterize how fire severity influences SOM composition along soil burn severity gradients (Objective 3). Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) currently achieves the highest mass resolving power in the world, which allows for the study of complex mixtures with tens of thousands of compounds that are separated by the mass of an electron across a wide molecular weight range. The most widely used FT-ICR MS analytical approach uses negative-ion mode electrospray ionization (-ESI) to selectively ionize highly abundant carboxylic acids in SOM. The application of this approach has allowed for rigorous analysis of C composition; however, -ESI FT-ICR MS vastly underestimates N-dense species which are formed during combustion. The biases associated with ionization are propagated in chemical property calculations that are determined by elemental compositions and which must be fully understood for proper use in C and N cycling models. We compared traditional -ESI with positive-ion mode electrospray ionization (+ESI) of burned soil extracts and found that +ESI increased compositional coverage by 87%, including nearly 10,000 additional N species (Objective 1). We applied our +ESI FT-ICR MS findings on a burn severity gradient (low, moderate, and high severity) to evaluate the compositional changes to SOM with increasing severity, with a specific focus on organic nitrogen. We collected soils from burned lodgepole pine forests along the Colorado-Wyoming border from two depths to characterize changes to organic N chemistry. Since organic N is the most abundant form of soil N in conifer forests, a better understanding of post-fire organic N will help address a critical gap in our understanding of fire severity-induced changes in the molecular composition of soil organic nitrogen. Nuclear magnetic resonance spectroscopy and FT-ICR MS analysis showed that N content and aromaticity of water-extractable SOM (0-5 cm depth) increased with burn severity, while minimal changes to the 5-10 cm depth were observed. Heterocyclic N species are generally higher in toxicity compared to their non-nitrogenated counterparts, which prompted soil toxicity measurements. We used Microtox ® to determine that soil toxicity increased with increasing burn severity, which may be partly attributed to newly formed N-species (Objective 2). In conjunction with increased fire activity, North American beaver (C. canadensis) populations have steadily increased since the early 1900s. The ponds that beavers create slow or impound hydrologic and elemental fluxes, increase soil saturation, and have a high potential to transform redox active elements (e.g., oxygen, nitrogen, sulfur, and metals). While surface water runoff composition has been studied in many environments, the effects of reducing conditions (i.e., beaver ponds) on these products are not well known. We collected surface water and sediment samples to investigate the impact of beaver ponds on the chemical properties and molecular composition of dissolved forms of C and N, and the microbial functional potential encoded within these environments from a combination of FT-ICR MS and metagenomics. We found that N-containing compounds and aromaticity increased in the surface water of burned beaver ponds, and that C/N and O/C ratios decreased. Microbial communities within the ponds did not have the capacity to process aromatic species, but they did have the potential for anaerobic metabolism and the potential to respire on microbial necromass (Objective 3). Fires burn heterogeneously across the landscape, and overstory vegetation likely plays a large role both in the way fires burn and how soils recover post-fire. Site factors such as soil type affect the interactions of SOM with abiotic soil components and can have cascading effects on soil C storage, including SOM partitioning between particulate organic matter (POM) and mineral associated organic matter (MAOM). POM is generally considered to have a faster turnover time than MAOM, which is physically protected from microbial degradation. Soil under two common trees in Colorado (lodgepole pine and aspen) are known to differ in SOM quantity and composition, including their relative proportions of POM and MAOM but post-fire products in these soils are relatively uncharacterized. To determine the differences in post-fire SOM between aspen and pine soils, we collected soils from under aspen and pine stands and burned them in open-air pyrocosms to minimize environmental variables which confound field-based studies. We concluded that fire influenced the dissolved fraction of the soils, with higher concentrations of dissolved organic carbon, dissolved total nitrogen, ammonium-N, and nitrate-N in burned aspen soil extracts. To determine the implications for less bioavailable carbon fractions, we will determine %C and %N in soils that have only been dried and sieved, as well as separated into POM and MAOM. We will also characterize the dissolved fractions using FT-ICR MS and NMR to evaluate differences in soil functional groups. Complementary microbiome analyses will be performed to determine the implications of shifts in soil functionality for microbial processing and C and N sequestration. The novel application of +ESI in this dissertation allowed for the identification of increasingly N-dense species at high burn severities which were not previously observed in field samples. N-dense species are enriched under reducing conditions as they are unable to be processed by local microbial communities. In total, these findings contribute to our understanding of newly formed organic C and N species in soils, with implications for microbial activity in fire-affected watersheds.Item Open Access Impact of iron and redox chemistry on the environmental fate and transport of metalloids and radionuclides(Colorado State University. Libraries, 2014) Troyer, Lyndsay D., author; Borch, Thomas, advisor; Ladanyi, Branka M., committee member; Levinger, Nancy E., committee member; Henry, Charles S., committee member; Kelly, Eugene F., committee memberMillions of cubic meters of uranium (U) mine tailings worldwide and millions of gallons of contaminated groundwater are the result of U mining and milling activity. Arsenic can occur at up to 10 weight percent in U ore, so both U and As can be released during U mining. Although these elements commonly occur together, little research into their redox behavior when present in the same environmental system has been performed. The goal of this research is to gain an improved understanding of how redox chemistry affects U and As speciation and complexation when the two elements are present together as co-contaminants. The North Cave Hills in Harding County, South Dakota is an abandoned U mine where overburden has been left open to weathering and transport since mining began in 1955. The exposed overburden has resulted in above-background level concentrations of U and As in sediments and groundwater in the surrounding wetlands. We conducted a field-scale study to investigate U and As redox chemistry at the North Cave Hills by taking sediment samples from the tailings pile and the down gradient watershed in order to assess U and As fate and transport. As sediments pass through anoxic zones at the field site, U is immobilized as reduction takes place but As can simultaneously be released into surface waters as reductive dissolution of Fe minerals also occurs. A laboratory-based study was conducted in order to examine the redox chemistry of U and As in North Cave Hills sediments under controlled conditions. Upon microbial reduction of sulfate and formation of mackinawite in batch systems, U(VI) and As(V) were reduced to nano- UO2 and a reduced As-sulfide mineral phase respectively during biostimulation by three different electron donors. When these systems were exposed to air for 24 hours, mackinawite protected U and As from oxidation and little change in their solid-phase speciation was observed. While mackinawite was shown to play a role in reduction, we could not determine if direct microbial reduction of U and As was also taking place in the systems. In order to further explore the reduction of U(VI) and As(V) by mackinawite, an experiment was set up to determine if As(V) prevented U(VI) reduction, especially following the formation of uranyl arsenate precipitates. As(V) only had an impact on the extent of U reduction at concentrations higher than would occur in most environmental systems. When As(V) concentrations were high, U(VI) was shown to be resistant to reduction because of the precipitation of a uranyl arsenate mineral phase. The findings in this dissertation contribute important information that will improve our current understanding of U and As redox behavior that will lead to improved remediation strategies to effectively prevent the mobilization of both elements in environmental systems.Item Open Access Photodegradation of selected endocrine and pharmaceutically active compounds under environmentally relevant conditions - processes and products(Colorado State University. Libraries, 2014) Young, Robert B., author; Borch, Thomas, advisor; Davis, Jessica G., committee member; Gray, James L., committee member; Henry, Charles S., committee memberTo view the abstract, please see the full text of the document.Item Open Access Quantum chemical modeling of redox reactivity, degradation pathways and persistence for aqueous phase contaminants(Colorado State University. Libraries, 2010) Blotevogel, Jens, author; Borch, Thomas, advisor; Sale, Thomas C., committee member; Barbarick, Kenneth Arthur, committee member; Bernstein, E. R. (Elliot R.), committee memberModels used to predict the fate of aqueous phase contaminants are often limited by their inability to address the widely varying redox conditions in natural and engineered systems, as well as by their dependence on existing experimental data for structurally similar compounds. Here, a novel approach based on quantum chemical calculations is developed, which can be applied to assess the environmental fate of any contaminant of interest without previous knowledge of the compound. It identifies the thermodynamic conditions necessary for redox-promoted degradation, and predicts degradation pathways as well as contaminant persistence. Hexamethylphosphoramide (HMPA), a widely used solvent and poorly characterized groundwater contaminant, is used as a test case. The development of an analytical technique based on liquid chromatography / time-of-flight mass spectrometry enables the detection of various degradation products that are reported here for the first time. The oxidation of HMPA is estimated to require at least iron-reducing conditions at low to neutral pH, and nitrate-reducing conditions at high pH. Furthermore, the transformation of HMPA by permanganate, a common groundwater remediation agent, is predicted to proceed through sequential N-demethylation. Experimental validation confirms the predicted pathways of HMPA oxidation by permanganate to phosphoramide via the formation of less methylated as well as singly and multiply oxygenated reaction intermediates. Pathways predicted to be thermodynamically or kinetically unfavorable are similarly absent in the experimental studies. Theoretical and experimental investigations, using 18O-labeled water to determine the source of oxygen in the products of HMPA oxidation, reveal a novel mechanism in addition to the one reported in the literature for methyl oxidation. The strategy of calculating Gibbs free energies of activation can be generally used to determine the primary degradation pathway when two or more pathways are thermodynamically favorable. In this study, however, the determined kinetic parameters show that both HMPA oxidation pathways proceed at similar reaction rates. Hydrolysis of the P-N bond in HMPA is the only thermodynamically favorable reaction that may lead to its degradation under strongly reducing conditions. Through calculation of aqueous Gibbs free energies of activation for all potential reaction mechanisms, it is predicted that HMPA hydrolyzes via an acid-catalyzed A2@P mechanism at pH < 8.2, and an uncatalyzed concerted backside SN2@P-b mechanism at pH 8.2 - 8.5. The estimated half-lives of thousands to hundreds of thousands of years over the groundwater-typical pH range of 6.0 to 8.5 indicate that HMPA will be persistent in the absence of suitable oxidants. At pH 0, where the hydrolysis reaction is rapid enough to enable measurement, the experimentally determined rate constant and half-life are in excellent agreement with the predicted values. The newly developed methodology will enable scientists, regulators, and engineers to estimate the favorability of contaminant degradation at a specific field site, suitable approaches to enhance degradation, and the persistence of a contaminant and its reaction intermediates.Item Open Access Reuse of oil and gas produced water for irrigation of spring wheat (Triticum aestivum L.): plant physiological and immune system response(Colorado State University. Libraries, 2019) Qiu, Yuheng, author; Borch, Thomas, advisor; Blotevogel, Jens, committee member; Young, Robert, committee memberWater resources for agricultural irrigation in the semiarid western United States are challenged due to increased oil and gas (O&G) activity and increasing water scarcity. Produced water (PW) generated from the O&G industry has been considered as an alternative source for crop irrigation, but there are few studies on the topic. Thus, here a greenhouse study was conducted to evaluate the impacts of PW irrigation on spring wheat (Triticum aesticum L.) with respect to plant morphology, physiology, and immunity to bacterial and fungal pathogens. Plants were irrigated with the following types of water: 100% tap water (TW), 10% and 50% PW (PW10 & PW50) and a salt (NaCl) solution (SW50 control; NaCl concentration is equal to PW50). Furthermore, pathogen treatments containing bacteria (Xanthomonas campestris) and fungi (Septoria tritici) were applied to the wheat plants to test plant immune response. In comparison with the TW control, plants irrigated with PW50 exhibited developmental delay and premature senescence, significant loss of yield, and significant decline in photosynthetic efficiency and immune function. The PW10 and SW50 control both resulted in reduced plant yield and photosynthesis, but PW10 was more damaging than SW50 to plant immune system, despite the high salt contents in SW50. These findings indicate that constituents (e.g., organic contaminants) other than NaCl in PW are contributing to plant stress, and they may play a far greater role in affecting plant immune function than salt stress.Item Open Access Soil degradation and water scarcity: the importance of soil organic matter and reuse of non-traditional water sources within agricultural systems(Colorado State University. Libraries, 2023) Stokes, Sean, author; Borch, Thomas, advisor; Trivedi, Pankaj, committee member; Ippolito, Jim, committee member; Fonte, Steve, committee memberOur exponentially growing world will demand approximately 70% more agriculture production by 2050, yet according to the Food & Agriculture Organization of the UN, ~33% of land worldwide is experiencing soil degradation and by 2050, over 90% of soils could be degraded. Exacerbating problems with soil degradation are droughts that are becoming more common with a warming climate. According to the National Oceanic and Atmospheric Administration, ~60% of the USA experienced drought in 2022 and over 90% of the Western US is under drought conditions, including one of the largest agricultural regions in the world, California. Therefore, in order to address these urgent issues of soil degradation and water scarcity, agriculture needs to adapt to more sustainable management practices that emphasize the importance of maintaining soil health, specifically, soil organic matter (SOM), and implement treatment processes to utilize non-traditional water sources (i.e., wastewater from various sectors). This dissertation is a combination of two different research projects that focus on these topics. Two chapters are focused on soil degradation in agriculture in collaboration with an industry partner, Cutrale Citrus, and two chapters are focused on the reuse/treatment of non-traditional water sources in collaboration with the Department of Energy's National Alliance for Water Innovation (NAWI).Our scope within the NAWI project was to develop a baseline paper (i.e., a review) for this concept within agriculture, specifically the reuse of agricultural wastewater and the treatment of produced water (PW) for use as irrigation water. Since agricultural water quality has large regional variability, we focused on two agricultural regions, the Midwest and California. The Midwest has runoff primarily contaminated with nutrients that lead to eutrophication in the major water bodies of this region, while California has saline runoff that in some cases is too toxic to be released to the environment. California's agricultural runoff requires advanced treatment techniques while the Midwest could use existing tile drainage systems to capture runoff and re-apply it to cropland since the main contaminants are nutrients. The reuse of PW is more complicated since its often highly saline and contains other toxic organic compounds or metals. Kern County, CA has been reusing PW for over 20 years but only because their PW has low salinity, this allows them to implement low-cost treatments focused on dilution, but this reuse has been controversial. Our analysis showed there are many unknowns related to the toxicity of PW, so we also develop a path forward through the implementation of an "Adverse Outcomes Pathway" approach that could be utilized to minimize any risks associated with the reuse of this water for irrigation. The research focused on soil health utilizes soil from a citrus grove in SW Florida managed by Cutrale Citrus. The first study focused on why tree size varied between areas of the grove with identical management practices and trees of the same age. Based on these observations it was clear that soil health varied between these areas, so we endeavored to understand what components of the soil, including both physiochemical parameters and biological indicators, were showing significant differences between the productivity regions. The results showed that SOM concentrations, enzyme activity, and microbial diversity were the components of the soil that were significantly different between these areas. Additionally, these trees were all infected with Citrus Greening disease, so we developed a hypothesis based on how this phloem-limiting infection could also be impacting soil health or conversely, how soil health could impact the progression of this disease. Based on these results, the second study focused on how we could regenerate the SOM in this soil and improve soil health through the addition of different organic amendments (biochar and compost). A 400-day greenhouse study was conducted to look at changes to the SOM; we combined typical soil science analysis of SOM such as concentration and mineralization rate with molecular level analysis using high-resolution mass spectrometry (FT-ICR MS). Analysis of microbial diversity was also conducted but those results will not be finished in time to be included in the dissertation and will be included only in the published paper. The soils showed clear differences in molecular composition at both the start and finish of the study depending on which amendment was added. Overall, the compost soil showed an initial spike in activity followed by degradation and loss from the system while the biochar showed slower increases in activity and more stability in the soil. The molecular analysis clearly showed the shift of compost towards more oxygenated molecules and a decrease in the number of different chemical formula present, while the biochar soils had transformation occurring without much loss and contained molecules that were more reduced. Overall, this study showed how biochar is an effective amendment when considering the long-term impacts that one application could have compared to compost which has greater stimulation of the soil in the short term but quickly degrades and needs to be reapplied frequently. When considering the issues facing agriculture in the 21st century it is important to take an all-inclusive approach because agriculture is comprised of interconnected systems. For example, if soil health and SOM are not properly considered then that soil might have less ability to store and absorb water so more erosion or nutrient leaching might occur. Or conversely, if water of poor quality is applied to a field, then salts could build up and degrade the soil. However, if we continue to have devastating droughts in the Western US then we might need to consider reusing alternative water sources to irrigate our fields and we should begin to prepare for that possibility as our high-quality freshwater supplies dwindle.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 role of organic matter chemistry in iron redox transformations, sorption to iron oxides, and wetland carbon storage(Colorado State University. Libraries, 2018) Daugherty, Ellen E., author; Borch, Thomas, advisor; Barisas, George, committee member; Conant, Richard, committee member; Neilson, James, committee memberOrganic carbon comprises a versatile and complex class of compounds that influence water quality, soil health, fate and transport of environmental contaminants, biogeochemical cycles, and climate change. Key to predicting the responses of these systems and processes to environmental change is a molecular-level understanding of how organic carbon reacts with other components of soil and water. Yet due to its complexity and that of the systems in which it is found, organic carbon dynamics remain poorly understood. In both terrestrial and aquatic environments, the reactivity and biological necessity of iron and carbon link the biogeochemical cycling of these elements. Complexation of iron by dissolved organic carbon molecules alters its solubility and oxidation-reduction behavior and may explain the persistence of reduced iron (Fe(II)) in oxic aquatic environments. By examining the coordination environment of Fe(II) complexed by dissolved organic matter (DOM) and evaluating the effects of complexation on Fe(II) oxidation, I determined that the majority of Fe(II)–DOM complexes were characterized by coordination with citrate-like ligands, which were unlikely to inhibit oxidation by molecular oxygen. Nonetheless, association with reduced organic matter could extend the lifetime of Fe(II) in oxic environments by several hours. In soils and sediments, iron minerals act as effective sorbents of organic matter, preserving substantial amounts of carbon from microbial decomposition. These interactions have increasingly been recognized as important components of carbon sequestration, yet the effects of temperature on sorption behavior remain unknown. Through several batch and continuous flow experiments, I demonstrated a positive relationship between temperature and sorption of DOM on iron oxide surfaces. The temperature sensitivity of sorption behavior varied among riverine, peat, and soil DOM types, with riverine natural organic matter sorbing and desorbing the most at all temperatures. Analyses of effluents also revealed preferential sorption of aromatic compounds during the initial stages of sorption. In soils, organic matter quantity and composition are determined primarily by the balance between plant productivity and microbial decomposition, which are in turn dependent upon climate, temperature, hydrology, nutrient availability, and soil composition. Wetlands store disproportionately large amounts of carbon, yet the processes controlling storage are poorly understood. I investigated how different environments created by the hydrology and geomorphic setting of two wetland types, depressional and slope, impacted soil organic carbon storage and composition. Results showed a prevalence of aliphatic structures in depressional wetlands, especially in deeper soils, suggestive of anaerobic decomposition processes. By comparison, carbon in slope wetlands was dominated by labile plant carbohydrates in surface soils and aromatic compounds at depth, a likely indication of less anaerobic conditions. These results demonstrate divergent pathways of organic matter processing in different hydrogeomorphic environments. In total, this work contributes to more mechanistic understandings of important carbon dynamics that influence carbon and iron cycling, climate change, and environmental health.Item Open Access Tracking ammonia volatilization and fate from emission source to pristine ecosytem(Colorado State University. Libraries, 2014) Stratton, Joshua James, author; Borch, Thomas, advisor; Prieto, Amy, committee member; Bernstein, Elliott, committee member; Fisher, Ellen R., committee member; Collett, Jeffrey L., committee memberAmmonia has been widely documented as a contributor to negative impacts on natural ecosystems. Agricultural related management has been closely tied to ammonia emission and therefore negative impacts of ammonia pollution. The aim of this research is to improve our current understanding of how ammonia is lost from native and agricultural soils and if nitrogen isotopes can be used to elucidate what sources of ammonia pollution affect native ecosystems the most. Rocky Mountain National Park (RMNP) has undergone ecosystem changes due to excessive nitrogen deposition in the forms of ammonium, nitrate and organic nitrogen. Due to uncertainty in source apportionment; the efficacy of nitrogen isotopes of ammonia to distinguish sources of ammonia deposited in RMNP was investigated. This study shows average δ¹⁵N isotopes of certain sources (beef cattle, dairy cattle production, wastewater treatment, cropland, urban) were distinguishable at this study's emission sites; however, the average δ¹⁵N isotope values measured at a RMNP site were not useful for identification of specific ammonia sources. Supplemental information (weekly integrations of gaseous and particulate reduced nitrogen, oxidized nitrogen, sulfur measurements, and HYSPLIT modeling) was needed to help pinpoint the likely sources of ammonia, such as agriculture and biomass burning, affecting RMNP. Moreover, this supplemental information was used to support the most likely reasons δ¹⁵N isotope values observed in gaseous ammonia and wet deposition were indistinguishable compared to emission sources. Little is known about the potential local contribution of ammonia from soils within RMNP. Thus, the goal of this study was also to develop a method for analysis of ammonia emissions from intact soil cores sampled from a sub-alpine grassland and forest within RMNP. Nitrogen wet deposition was monitored at the sampling location to investigate possible impacts on soil emissions of ammonia. Lastly, method development and analysis of formation of ammonia (urea hydrolysis), pH speciation (ammonia and ammonium), and vapor pressure (Henry constant) were investigated in beef and dairy feedlots to reveal important controls on ammonia emission. This research provides new information on the importance of post emission physical and chemical processes, such as source mixing, isotopic fractionation, and dry deposition, preventing the use of δ¹⁵N isotopes for source tracking without the use of complementary techniques, such as atmospheric modeling. Moreover this work provides further evidence indicating that natural emissions within RMNP are not major sources of reduced nitrogen in the RMNP airshed. Lastly, this work provides new chemical values for the Henry constant, acid dissociation constant, and urea hydrolysis rate constants in animal production systems and can be used to better estimate ammonia emissions from animal production to improve our current emission inventories.Item 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 memberSoils 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.Item Open Access Urbanized nutrient enrichment of the Klina River in Kosovo: impact on surface water and drinking water quality in a developing country(Colorado State University. Libraries, 2012) Hefley, Roger Daniel, author; Borch, Thomas, advisor; Sharvelle, Sybil, committee member; Bauder, Troy, committee memberUrban development is a present and future challenge for water managers, with one of those challenges being nutrient enrichment. While the ecological and health impacts of nutrient enrichment are well documented and understood, the challenge still remains in helping developing countries initiate a sustainable water quality program that will address nutrient enrichment and other water quality problems. The Klina River in Kosovo has shown evidence of eutrophication in multiple locations. The goal of this research was to quantify the nutrient concentrations and loads of NH4, NO3, and PO4; and determine what level influence urban development was having on the Klina River's water quality.