Theses/Dissertations - Environmental Science

Permanent URI for this collectionhttps://hdl.handle.net/2104/4483

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A stepwise approach to understanding nanomaterial transformations under situationally relevant conditions.
(2021-04-20) Mulenos George, Marina Rochelle, 1995-; Sayes, Christie M.
Given the increasing use of nanomaterials in various consumer products and industrial processes, it is of the utmost importance to better understand potential mechanisms of adverse effects to ensure human health and safety when developing regulations and standard operating procedure with newly developed materials, like nanomaterials. Nanomaterials are materials with one or more dimensions in the nanoscale range that are produced to advance industrial processes, used as an additive in consumer products, and produce novel drug delivery carriers. Standardized toxicological studies focus on newly produced nanomaterial products before they reach the market; however, most of these studies exclusively investigate pristine engineered nanomaterials. The issue with testing pristine engineered nanomaterials is that most environmental and/or human toxicities are induced after nanomaterials undergo transformations, e.g. release of metal ions. The goal of this dissertation was to conduct a comprehensive study of increasingly complex situationally relevant environments on organic and inorganic nanomaterials to understand important insights into nanomaterial transformations and the associated toxicity after exposures in vitro. Situationally relevant conditions occur when nanomaterials are used in products or processes and interact with the surrounding environment, where they then may undergo transformations. These transformations may include distribution with biomolecules or natural organic matter, lipid membranes in cells, high ionic conditions, or changes in temperature, salt concentration, etc. In this study, important physicochemical characterization methods were established for organic and inorganic nanomaterials. Additionally, these nanomaterials were transformed under simulated conditions and examined in increasingly complex environments. Next, the transformed nanomaterials were incubated with an established in vitro liver model to elucidate the relationship between nanomaterial transformations and the associated toxicity after exposure. Finally, transformed nanomaterials were exposed to an in vitro model for steroidogenic disruption to investigate further into adverse effects nanomaterial transformations may have on human health. Ultimately, the aim of this work is to advance the field of toxicology by improving our understanding of nanomaterial transformation mechanisms and to aid in risk assessment and regulations.
Accumulation of trifluralin and trinitrotoluene (TNT) in two aquatic invertebrates: formation and persistence of unextractable biotransformation products.
(2008-06-09T13:12:51Z) Dudley, Melissa B.; Chambliss, C. Kevin.; Environmental Science.; Baylor University. Dept. of Environmental Science.
Exposure to nitroaromatic compounds has been reported to result in unextractable residues, or residues not readily extracted by traditional techniques. However, limited information is available about the formation rate and biological half-life of unextractable residues in aquatic organisms. In this study, two aquatic invertebrates, Lumbriculus variegatus and Hyalella azteca, were exposed inaqueous media to ¹⁴C-labeled trinitrotoluene and trifluralin. Unextractable residues were formed in both organisms by both compounds. TNT formed a greater percentage of unextractable residues than trifluralin. L. variegatus accumulated more TNT-related unextractable residues compared to H. azteca, while the reverse was true for trifluralin. H. azteca eliminated unextractable residues moreefficiently than L. variegatus. Additionally, the biological half-life of unextractable residues was longer than that of the extractable residues. The presence and biological persistence of unextractable residues indicates that these compounds, and especially TNT, could cause subtle and chronic biological effectsand serve as indicators of exposure.
Age matters : developmental stage of Zebrafish (Danio rerio) influences bioconcentration, and survival and behavioral photomotor response thresholds.
(2017-08-03) Kristofco, Lauren A., 1989-; Brooks, Bryan W.
Toxicology information for the tens of thousands of compounds in commerce is severely lacking, and with continual introduction of new substances, this global chemical space is only increasing in complexity. Thus, generating data pertinent to legislation, regulation and risk assessment has become paramount. Significant hurdles exist for the production of such data sets as traditional whole organism studies have exorbitant costs, are time intensive, and are low throughput. To meet these goals alternative methods have been developed that shift the focus from a traditional, high dose, apical endpoint, based study design to a higher throughput, systems-biology, based design, however, as this is realized, critical evaluations of the newly introduced methodologies are warranted. Transitioning to high throughput screening (HTS) and predictive methodologies will further require focused efforts to not only identify these assays but also their intrinsic uncertainties. This novel dissertation employed two of the proposed alternative methodologies, probabilistic environmental hazard assessment and the fish embryo toxicity (FET) test, and probed their efficacy with an understudied class of contaminant, antihistamines. In Chapter 2, global hazards of antihistamines in surface waters were assessed with a probabilistic environmental hazard approach (PEHA) to identify global trends in occurrence. Subsequently, the capacity of the FET method to examine mixture interactions with a comparative pharmacology and toxicology approach (Chapter 3), and to extend to include behavioral observations (Chapter 4), was evaluated. Finally, to further elucidate the applicability domain of the FET, Chapter 5 investigated the driver for the age specific shifts in sensitivity evidenced in Chapters 3 and 4. These observations demonstrate the utility of both methods, and underline the importance of method selection and application.
Aquatic toxicology of salinity and silver in Daphnia magna : a comparative study of standardized chronic endpoints and progeny Phototaxis.
(2011-12-19) Kolkmeier, Mark A.; Brooks, Bryan W.; Environmental Science.; Baylor University. Dept. of Environmental Science.
Behavioral bioassays with the model freshwater cladoceran Daphnia magna have the potential to serve as nontraditional but sensitive endpoints of sublethal stress in the field of ecotoxicology. However, few studies have examined the comparative sensitivity of phototaxis perturbations to standardized endpoints in chronic toxicity testing protocols. D. magna 21 d chronic toxicity studies were conducted with model stressors of salinity (NaCl) and dissolved silver (Ag+). Phototaxis assays of progeny response to relative light changes in small water columns were conducted of each brood. Results indicated predominantly decreased phototactic behavior in comparison to control brood performance at common ecotoxicological thresholds. Phototaxis assays showed effects at treatment levels below the 21-d adult reproduction LOEC value in broods 2, 3, 5 and 6 in the salinity study and broods 2, 5, and 6 in the silver study. Future refinement of robust and potentially highly ecologically relevant behavioral assays such as phototaxis in combination with traditional and nontraditional endpoints may prove useful in characterization of assessment factors.
Assessing interactions between nutrients and aquatic toxicity : influences of nitrogen and phosphorus on ionic silver toxicity to the aquatic macrophyte Lemna gibba.
(2011-05-12T15:18:27Z) Bian, Jingyi, 1985-; Brooks, Bryan W.; Environmental Science.; Baylor University. Dept. of Environmental Science.
Though nutrients and silver often co-occur in aquatic ecosystems, the combined effects of these environmental stressors on aquatic plants are poorly understood. Such coexposures are important because nanosilver is increasingly released to the environment, and recent studies indicate that the dissolved fraction of nanosilver appears to be more acutely toxic to aquatic life. The primary objective of this study was to understand the effects of nitrogen (N) and phosphorus (P) concentrations and N : P ratios on the toxicity of ionic silver toxicity to the model aquatic macrophyte Lemna gibba over 7-d study periods. The experimental results indicated that L. gibba were more sensitive to silver (e.g., lower EC50 values) when N and P concentrations were higher. In addition, greater ionic silver toxicity occurred under higher P-availability (e.g., lower N : P ratios) conditions. L. gibba frond number and fresh weight were also differentially affected and showed variable sensitivity to different nutrient x silver treatment combinations, which highlights the importance of considering site-specific nutrient conditions during the prospective and retrospective assessment and management of silver impacts to primary producers.
Atmospheric concentrations of organophosphate esters in Delhi, India.
(2018-04-27) Stephensen, Marie, 1992-; Usenko, Sascha.
The rise of organophosphate esters (OPEs) as ubiquitous global air pollutants is in part associated with their high-production volume, physical and chemical properties, and heavy use in consumer products, including many electronics. The current study investigates the composition and seasonal variability of atmospheric OPEs in Delhi, India. Atmospheric PM2.5 (particulate matter with an aerodynamic diameter ≤ 2.5 microns) samples were collected from April to November 2009 in downtown Delhi. PM2.5 samples were extracted using pressurized liquid extraction and the extracts were analyzed for twelve OPEs, including TPhP, using gas chromatography-mass spectrometry. The sum of atmospheric OPE concentrations ranged from 2.71 to 61.4 ng m^-3 abd were up ~600 times that of concentrations reported in the US. Findings from a study were similar to those reported from e-waste recycling areas in Pakistan, where TPhP was the dominant OPE. This may suggest that e-waste recycling is a major source of atmospheric OPEs in Delhi.
A baseline assessment of local mercury deposition from coal-fired power plants in Central Texas.
(2006-10-02T15:11:58Z) Furl, Chad Van.; Lehr, Larry L.; Van Walsum, G. Peter (Gerard Peter), 1963-; White, Joseph Daniel.; Environmental Science.; Baylor University. Dept. of Environmental Science.
Coal-fired power plants represent the largest source of anthropogenic mercury in the world. The Central Texas region as represented by the Heart of Texas Council of Governments contains two coal-fired power plants located in Freestone and Limestone Counties. A third plant, Sandy Creek, is currently being proposed for McLennan County. The primary objective of the study is to estimate the amount of mercury being deposited via wet deposition in 2003 from two existing power plants in Central Texas, Big Brown and Limestone, and predict deposition from a proposed plant, Sandy Creek. The Industrial Source Code Short-Term model was used to estimate wet deposition, and empirical data was collected to determine the mercury levels in environs near the plants. According to the research and statistical analyses, the Central Texas power plants studied appear to be having no impact on the water quality of area surface waters.
Bioaccumulation of contaminants of emerging concern in dynamic ecosystems.
(2018-11-14) Haddad, Samuel Perry, 1990-; Brooks, Bryan W.
The aquatic environment includes complex systems on which society relies to provide ecosystem services and support biodiversity. In recent years, the demand for aquatic-ecosystem commodities has greatly increased due to rapid population growth and industrialization. This burgeoning population stresses the global water cycle in many ways including increased fossil-fuel consumption promoting climate change, altered snowpack decreasing instream flows, multiple cities utilizing the same waterways, and increased nutrient loading due to agricultural expansion. And poorly treated sewage Such alterations to aquatic systems leads to unique exposure scenarios of contaminants of emerging concern such as pharmaceuticals and cyanotoxins. Thus, an understanding of exposure, hazards, and bioaccumulation of contaminants of emerging concern in dynamic aquatic systems in necessary to support sustainable management of aquatic resources. In this dissertation, the first study examined bioaccumulation of diphenhydramine, an ionizable weak base pharmaceutical, across different life stages in an organism that demonstrated ontogenetic diet changes in an urban estuary. The findings of this study demonstrated that ontogenetic dietary shifts do not affect the bioaccumulation of diphenhydramine, but exposure difference in water does. The second study investigated whether ionizable weak base compounds with differing properties demonstrated trophic dilution within the food web of urbanizing rivers receiving runoff from snowmelt. This study observed that multiple ionizable weak base pharmaceuticals trophicly diluted with increasing trophic position and that inhalational uptake was the main driver of bioaccumulation in rainbow trout. The third study examined the spatial and temporal fate and transport of ionizable pharmaceuticals within a dynamic aquatic system that shifted from being influenced by spring snowmelt to effluent-dominated conditions. The findings of the third study reported decreasing concentrations with increasing distance downstream regardless of season and the presence of secondary inputs from onsite waste-water systems. The fourth study developed a novel analytical method and then investigated the bioaccumulation potential of various cyanobacterial toxins in a highly eutrophic Texas reservoir. The fourth study identified several novel methodological approaches to analytically identify cyanotoxins and reported the presence of cyanotoxins in Lake Waco, Texas, USA for the first time. These observations collectively provided novel environmental assessment approaches to support an advanced understanding of bioaccumulation within dynamic aquatic ecosystems.
Biological responses from contaminants accumulated in seafood using an in vitro human intestinal and liver co-culture.
(2019-06-10) Sutherland, Grace E., 1995-; Lavado, Ramon.
In vitro bioassays have been useful in predicting mechanisms of toxicity; however, conventional cell-based assays grown in monolayers are unavoidably poor models for human tissues due to the lack of complexity and physiological interplay observed in vivo. To address these limitations, the present study utilizes a combination of human intestinal and hepatic cells in a co-culture model. The purposes of these projects are to evaluate the differences between mono- and co-culture systems related to cytotoxicity and enzyme activity, and apply the co-culture model in the screening of seafood samples collected from the Galveston Bay. It was observed that the co-culture model had greater antioxidant enzyme activity compared to that of the monoculture, suggesting that hepatocytes grown in co-culture may be better suited to facilitate the expression of enzymes in response to xenobiotic metabolism in intestinal cells. This emphasizes the importance of adequate model selection to facilitate assessment of risk.
Community needs assessment among the Gujjars in Northern India.
(2002) Dorrell, Janet C.; Alexander, Sara E.; Baylor University.
The perceived needs of the Gujjars of northern India were investigated in the Gurdaspur District of Punjab, India. The purpose of this study was to provide baseline data on the Gujjars who migrate to and from the states of Punjab to Himachal Pradesh by assessing their basic human needs within Johan Holmberg's sustainable development framework. These baseline data were gathered using a Needs Assessment Survey that represents approximately seventy-five Gujjar families who suffer problems of under-representation and social, economic and geographic marginalization. The analysis encompassed in the approach, defined as advocacy anthropology, suggested that the Gujjars do perceive a need for development and advocacy, specifically in the areas of education, land distribution, medical access, freedom from exploitation, political empowerment, and relief from poverty.
Designing quantitative structure activity relationships (QSAR) to predict specific toxic endpoints for polybrominated diphenyl ethers (PBDE) in mammalian cell culture systems.
(2011-12-19) Rawat, Swati, 1984-; Bruce, Erica Dawn.; Environmental Science.; Baylor University. Dept. of Environmental Science.
Polybrominated diphenyl ethers (PBDEs) are becoming increasingly known as effective flame retardants and have vast industrial application in products like plastics, building materials, and textiles. They are found to be structurally similar to thyroid hormones that are responsible for regulating metabolism in the body. Structural similarity with the hormones poses a threat to human health because once in the system, the PBDEs may change thyroid hormone transport and metabolism. This study is aimed at designing QSAR models for predicting toxic endpoints for PBDEs in mammalian cells. QSAR modeling uses the known chemicals’ activity, which serve as surrogates to study unknown chemicals belonging to the same family. This research is a threefold process including running in-vitro bioassays to collect data on the toxic endpoints, modeling the evaluated endpoints using QSARs and validating the models using compounds of interest from the same family (PBDEs).
Detailed molecular and isotopic characterization of carbonaceous aerosols to assess air quality issues in urban areas : the San Francisco Bay Area and the Houston metropolitan area.
(2020-07-20) Yoon, Subin, 1989-; Sheesley, Rebecca Jacobs.
The objective of this dissertation is to provide detailed characterization of carbonaceous organic aerosols to better understand major sources of particulate matter (PM) and their atmospheric formation in an oxidizing and highly complex urban atmosphere. For this dissertation, optimized radiocarbon (14C) and source characterization techniques were applied to PM samples from the Houston Metropolitan Area and the San Francisco Bay Area. The San Francisco Bay area study was focused on identifying seasonal trends (winter and non-winter) and sources of elemental carbon (EC). The study required isolation of EC for 14C-based source apportionment. Chemical mass balance model (CMB) of EC and 14C-based total organic carbon (TOC; OC + EC) were also included for comparison of source apportionment methods and different carbonaceous aerosol fractions, respectively. Sources of EC and TOC were similar at most of the sites while a few sites (e.g. San Francisco and Napa) were distinctively more impacted by fossil fuel or contemporary/biomass burning sources. The winter season had significantly larger TOC concentration due to meteorological conditions and changes in emissions (e.g. increased residential wood smoke). Relatively good agreement between the 14C-EC- and CMB-EC- was observed for both seasons. The first and second Houston studies focused on identifying diurnal and temporal trends of aerosols using both fine and coarse PM and contribution of secondary organic carbon during periods of poor air quality (i.e. high ozone and PM), respectively. The largest concentrations of fine EC and BC concentrations occured during the mornings while periods of enhanced TOC was driven by an increase in the fine PM. Interestingly, a relatively large contribution of coarse EC was measured in Houston. Based on the 14C and CMB analysis, Houston’s carbonaceous aerosols are largely from secondary biogenic sources while secondary fossil contribution was highly variable. Furthermore, the poor air quality period in the Houston metropolitan area was driven by favorable meteorological conditions (i.e. Bay Breeze) providing stagnant atmospheric conditions, allowing for accumulation and photooxidation of fossil fuel emissions. Overall, the study results provided up-to-date characterization and source apportionment of less studied carbonaceous aerosols fractions at two major U.S. urban coastal regions.
Developing an understanding of behavioral and transcriptional implications for the chiral cyanotoxin anatoxin-a and caffeine in common larval fish models.
(2023-08) Lovin, Lea M., 1994-; Brooks, Bryan W.
Neuroactive compounds are widely and routinely detected aquatic contaminants. With multitudes of chemicals having known and unknown neuroactivity and the sensitivity of early neurodevelopment to contaminant insults, early life stage assays are crucial for understanding hazards of these chemicals to public health and the environment. However, one of the most widely used developmental in vivo assays, the OECD fish embryo toxicity test with zebrafish (Danio rerio), an increasingly common alternative vertebrate model, has been shown to be insensitive to many neuroactive chemicals. Therefore, complimentary approaches such as behavioral and gene expression assays have been used to increase sensitivity, but robust and standardized methods for these endpoints are uncommon. This dissertation primarily focuses on the chiral cyanobacterial neurotoxin anatoxin-a, and considers the neurostimulant caffeine, aiming to elucidate behavioral and transcriptional effects while heeding efficiency of compound and animal use. It further considers environmental relevance, stereospecific effects, species sensitivity, and variability of behavioral assays based on arena size. Specifically, a meta-analysis of the current state of anatoxins research in aquatic systems was performed using environmental exposure distributions (EEDs), and collating bioaccumulation and toxicity data, for which quality was inconsistent. Applying EED information, two alternative vertebrate models, zebrafish and fathead minnows, were exposed to environmentally relevant and higher levels of the commonly studied, synthetic (±) anatoxin-a to compare photolocomotor and gene expression responses, with caffeine as a positive methodological control. Whereas zebrafish were highly insensitive to the racemate, the toxin caused significant hypoactivity and transcriptional changes in fathead minnows. This design was repeated with the naturally produced (+) enantiomer. Mortality was caused by multiple treatment levels in fathead minnows and zebrafish, along with behavioral and gene expression changes, with fathead minnows again being more sensitive to several response variables. To further examine comparative behavioral methods used here and previously, the influence of arena size on behavioral responses of naïve and caffeine exposed zebrafish was investigated to understand inherent variability of the experimental observation arena. This dissertation identified novel anatoxin-a consequences, how effects may be underestimated by studies employing racemic mixtures, and the importance of behavioral methodologies in comparative studies with common fish models.
Evaluating paraben and paraben transformation product release in effluent following wastewater treatment and their movement into river water and fish tissues in the surrounding environment.
(2023-12) Penrose, Michael T., 1994-; Cobb, George P.
Parabens are a class of compound used as preservatives in personal care products and foodstuff. Because of their widespread usage, parabens are ubiquitous, being found in surface waters across the globe. Parabens have received attention due to findings that suggest that they are weakly estrogenic. However, there is a general lack of information on the release and impact of the paraben transformation products that are formed during treatment. This dissertation emphasizes the transformation of parabens in wastewater treatment and the effect release of these compounds in wastewater effluent has on river reaches and fish tissues following wastewater input. Two wastewater facilities were evaluated, one larger facility located along the Brazos and a second smaller facility located along Bull Hide Creek, a tributary that flows into the Brazos. The larger facility utilized chlorination as a tertiary treatment while the smaller treatment plant used UV disinfection. Treatment effectively removed parent paraben concentrations, with removal rates of over 90% for all parent parabens. Chlorinated transformation products resulted from both treatments. Analysis along the river found that the release of effluent had an impact on analyte concentrations in river water with increases in dichlorinated species directly downstream of effluent release. Analysis of fish muscle tissues found that the two most commonly used parent parabens as well as the dichlorinated parabens are accumulated at higher concentrations in the larger fish at a higher trophic level. Luminescence assays were used to determine if any of the evaluated transformation products retained the estrogenicity of the parent compounds and evaluate ecotoxicity based on the concentrations found in fish muscle tissues. Only some of the hydroxylated paraben species retained the estrogen agonist activity of the parent.
Evaluating the cytotoxicity and adverse effects of diesel exhaust particle exposure on the brain’s first line of defense, the blood-brain barrier and microglia, in vitro.
(2023-08) Aquino, Grace V., 1993-; Bruce, Erica Dawn.
Combustion-derived particulate matter (PM) such as diesel exhaust particles (DEP) is a public health concern because chronic exposure is associated with neurodegenerative diseases (NDs) like Alzheimer’s (AD). When inhaled, fine/ultrafine DEP can travel through systemic circulation or via the olfactory bulb to the central nervous system (CNS), where it can exert adverse effects on the blood-brain barrier (BBB) and perivascular microglia. In the healthy brain, the BBB (i.e. cerebrovascular endothelial cells; ECs) and microglia function as the brain’s first line of defense, and the BBB-microglia interaction is essential in maintaining CNS health. Notably, the underlying mechanisms of PM-induced CNS disease are multifactorial and complex, rendering mechanistic inquiry in pathophysiological and toxicological studies a significant challenge. Of such mechanisms, BBB dysfunction and microglial activation are heavily implicated in NDs. While several studies have evaluated DEP exposures on BBB ECs, no study had previously evaluated DEP exposures on EC-microglia co-cultures, despite the microglia’s dual role in protection against or promotion of cerebrovascular damage and neuroinflammation. Therefore, the overall goal of this dissertation was to investigate how DEP exposure affects BBB function using cerebrovascular ECs and microglia in vitro. Chapter One (published) evaluated the effects of acute (24 hr.) DEP exposure on the cellular health, oxidative stress, and inflammation of rodent cerebrovascular ECs with and without microglia. Chapter Two (published) then evaluated the effect of acute DEP exposure on a critical, clinically- relevant drug efflux transporter (i.e. P-glycoprotein), barrier permeability, and inflammation in human immortalized cerebrovascular ECs with and without microglia. Finally, Chapter Three presents data collected using an improved, human iPSC-derived BBB model (iBMEC), and preliminary data on changes in the Amyloid-β transport system (LRP-1, RAGE, and P-gp) and in the activation state of microglia under exposure to DEP. Overall, this work is novel because it is the first to evaluate DEP’s effect on BBB-microglia co-cultures, and on the Amyloid-β transport system. Ultimately, this work improves our understanding on DEP’s adverse effects in the BBB, and highlights the potential role of PM in the etiology of AD.
Examining aquatic hazards of cylindrospermopsin, a cyanobacterial toxin, in common larval fish models.
(2023-12) Scarlett, Kendall R., 1992-; Brooks, Bryan W.
The increase of harmful algal blooms (HABs) within recent decades has led to increasing risks for public health and the environment. Along with the general nuisances of bad odors and scummy waters, these blooms can produce a series of secondary byproducts that can cause a wide variety of adverse outcomes. Cyanotoxins are among the naturally produced byproducts that can cause a variety of ailments (e.g., nausea, headaches, gastrointestinal distress, etc.). Comparatively to other environmental contaminants (e.g., pharmaceuticals, pesticides), cyanotoxins are difficult to study due to the various factors that influence cyanobacterial species to produce toxins across environmental gradients. Previous early life in vivo assays with larval model species have proven to be useful in understanding the hazards associated with these various anthropogenically introduced contaminants; however, additional work is needed to study natural toxins as they become more prevalent in various surface waters. In addition to these well used assays to assess potential toxicity, additional approaches examining behavioral and transcriptional changes can be useful for understanding for providing a more wholistic approach for understanding potential adverse outcomes. The current dissertation focuses on cylindrospermopsin, a protein inhibitor and tricyclic cyanotoxin, that is found in various surface waters around the globe. A meta-analysis for environmentally detected cylindrospermopsin in various aquatic systems was performed through the development of probabilistic environmental exposure distributions (EEDs) and probabilistic environmental hazard assessments, along with further critical evaluation of aquatic toxicity and bioaccumulation data. To examine potential toxicity of cylindrospermopsin to aquatic species, the model vertebrate species Danio rerio and Pimephales promelas were exposed to environmentally relevant concentrations of cylindrospermopsin based on the previously developed EED. Additional behavioral and transcriptional assays were performed to examine sublethal effects of cylindrospermopsin, and compared to a positive control, another known protein inhibitor, cycloheximide. Further, both species were exposed to sublethal concentrations of sodium chloride to represent potential impacts that could occur after exposure to increasing fluctuations of salt due to inland salinization. This dissertation identified novel behavioral and molecular consequences after cylindrospermopsin exposure, examined cycloheximide as a model contaminant, and explored potential outcomes after sodium chloride exposure on common fish models. Future research is needed to understand the toxicology of cylindrospermopsin across the freshwater to marine continuum, in addition to inter-species variations.
The fate of phosphate in the MixAlco process and its applicability to a Central Texas watershed.
(2007-01-19T16:21:19Z) Doyle, Erin E.; Van Walsum, G. Peter (Gerard Peter), 1963-; Environmental Studies.; Baylor University. Dept. of Environmental Studies.
The MixAlco process is proposed as a means to reduce phosphorus concentrations in dairy cow manure in order to help improve water quality in the Lake Waco watershed. Numerous dairy farms and intensive agricultural practices are located in this Central Texas watershed, and dairy manure is a major source of nutrients, particularly phosphorus. Nutrients, such as nitrogen and phosphorus, are the main causes of eutrophication. The MixAlco process, which can use dairy manure as a source of biomass to produce a mixed alcohol fuel, may reduce phosphorous levels in manure wastes. The dairy manure filtrate was analyzed for soluble reactive phosphorous (SRP) before and after the first two steps of the MixAlco process. An average reduction of 86 percent was observed from beginning to end. A reduction in SRP may ease the impact dairy manure has on eutrophication in the Lake Waco watershed to help improve water quality.
Hydrology of non-riverine freshwater wetlands of the upper Texas coast.
(2010-06-23T12:31:20Z) Clapp, Adam G.; Yelderman, Joe C.; Environmental Science.; Baylor University. Dept. of Environmental Science.
Coastal Prairie Freshwater Wetlands (CPFWs) are characterized by depressions and flats that occur in the Galveston Bay area. Studies estimate that over 9,000 acres of CPFWs were lost between 1992 and 2002. The cumulative loss of water quality and flood storage function may have detrimental effects on water quality and flood attenuation. There are few quantitative data available to explain the hydrologic processes of palustrine (freshwater) wetlands. This study monitored six individual CPFWs with a combination of weirs, piezometers and rain gages; each with data loggers to record wetland, groundwater and nearby surface water levels. Data were collected for approximately 18 months with some gaps due to the effects of Hurricane Ike. Water budgets were calculated to evaluate storage volumes, discharge, and potential “nexus” with receiving waters. All the monitored wetlands discharged during the study, stored significant amounts of the annual water budget and were affected by seasons.
Impacts of long-range transport of biomass burning on air quality in Texas.
(2023-08) Shrestha, Sujan, 1992-; Sheesley, Rebecca Jacobs.
The objective of this dissertation is to (1) provide a detailed analysis of the concentration, trends, and emission ratios of volatile organic compounds (VOCs) and trace gases in major cities in Texas: San Antonio, and Houston, and (2) investigate the physical and chemical properties of transported biomass burning (BB) smoke and their impact on background air quality in Port Aransas, an industrialized coastal site in Texas. To achieve these objectives, mobile and stationary field experiments were conducted to measure the impact of local emissions and transported pollution on air quality in Texas cities. The inter-site comparison of VOCs and trace gases across the San Antonio metropolitan area revealed significant geospatial and temporal variabilities in emissions and processing within this metropolitan area. Further, VOCs concentrations and emission sources were compared for two growing Texas locations in San Antonio and Houston. The results indicate that Texas cities have complex emission scenarios and that future efforts to mitigate ozone (O3) and particulate matter may require various emission reduction strategies. Two long-range transport BB events (BB1 and BB2) were identified at Port Aransas. Several aerosol- and gas-phase BB tracers were evaluated to identify and characterize these long-range transported BB events in an industrialized location. The aerosol composition and optical properties exhibited good agreement with the BB designation, while acetonitrile and carbon monoxide (CO) trends were less specific for identifying dilute BB plumes. The air pollutant measurements in Texas Commission on Environmental Quality (TCEQ) Continuous Ambient Monitoring (CAMS) and Black and Brown Carbon (BC2)- aerosol optical monitoring networks in Texas revealed potential regional impacts of these transported BB events on urban O3 levels. Overall, this chapter supports implementing an extended network of aerosol optical measurements to identify the influence of BB plumes, especially in cities designated as nonattainment or marginal nonattainment of criteria air pollutants.
Individual and interactive influences of low dissolved oxygen and calcium channel blockers in inland aquatic systems.
(2018-08-31) Saari, Gavin N., 1988-; Brooks, Bryan W.
Understanding and managing influences of multiple stressors represents a major water quality challenge, particularly in urbanizing regions. Because aquatic hazard assessments with chemical and nonchemical stressors can identify the global trends in occurrence and hazards of stressors for the protection of aquatic life, probabilistic aquatic hazard assessments were performed to examine whether water quality guidelines for dissolved oxygen (DO) are protective of aquatic life in inland waters. My analyses indicate that adverse effects of low DO to freshwater invertebrates and fish have been underestimated in inland waters. Additional low DO threshold information, including sublethal toxicity, for additional species such as warm water fish and mollusks across multiple life history stages is necessary to support environmental assessment and management of ecosystem protection goals. Similar techniques were used to examine the occurrence of calcium channel blockers (CCBs), a common class of vasodilators and cardio suppressants, in environmental matrices, and to predict hazards to non-target aquatic organisms in multiple environmental matrices and geographic regions. Whereas environmental occurrence of CCBs in freshwater and effluent have predominantly been reported from North America and Europe, data is lacking from many developing regions around the world and hazards and risks of CCBs to non-target biota remains poorly understood. Therapeutic hazard values (THVs), a comparative pharmacology and toxicology approach, employed during probabilistic hazard assessments with environmental exposure distributions revealed that amlodipine and verapamil in effluent and freshwater exceeded THVs 28% of the time. Diltiazem exceeded minimum human therapeutic thresholds in fish plasma ~18% of the time in surface waters. This approach demonstrated the utility of global assessments to identify specific CCBs and geographic regions where environmental assessments appear necessary. Subsequently, to understand adverse effects of individual and multiple stressors influencing cardiac function (DO, diltiazem, or DO x diltiazem), toxicity studies were performed using a comparative toxicology and pharmacology approach in fathead minnows (Pimephales promelas) across larval and adult life stages. DO x diltiazem toxicity studies with larval fish revealed acute lethality increased with decreasing DO levels and altered burst swimming behavior at DO water quality criteria levels deemed protective of aquatic life. In adult fathead minnows, low DO (3.0 mg DO/L) increased uptake of diltiazem and altered physiological responses (e.g., hematocrit, plasma lactate) at and above human therapeutic plasma levels. Failing to consider low DO influences with chemical exposure during toxicological studies of cardioactive medications and potentially other cardiotoxicants underestimates adverse outcomes in fish.

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