Theses/Dissertations - Ecological, Earth, and Environmental Sciences
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Browsing Theses/Dissertations - Ecological, Earth, and Environmental Sciences by Author "Brooks, Bryan W."
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Item Advancing an understanding of ecological risk assessment approaches for ionizable contaminants in aquatic systems.(2010) Valenti, Theodore Walter.; Brooks, Bryan W.; Ecological, Earth, and Environmental Sciences.; Baylor University. Institute of Ecological, Earth and Environmental Sciences.Freshwater is increasingly becoming a finite resource in many regions of the world. Gaps between estimated water supply and demand continue to narrow and the prospects of acquiring additional sources of freshwater remain limited. Furthermore, economically efficient water resource management practices are perplexed by increasing urbanization and changing land-use in semi-arid regions. Although repeated use of water is a practical and effective means for easing strain on water supplies, there is concern that unnecessary contamination may diminish future value of this important resource. Some surface waters in semi-arid regions of the U.S. are effluent-dominated as flow is comprised of >90% treated wastewater. Ionizable compounds are chemicals often associated with urban development and examples include pharmaceuticals, agrochemicals, natural toxins, and other common contaminants (e.g. ammonia). Because continued population growth and urbanization are likely to increase contaminant release and alter dilution capacity of receiving systems, it is important that best management approaches are developed at the watershed scale to limit water quality degradation associated with ionizable compounds. Current methods for prospective and retrospective ecological risk assessments of ionizable compounds seldom consider site-specific conditions during the analysis of effects of phase. Ionization state is largely controlled by the acid/base dissociation constant (pKa) and pH of the solution where a compound resides. Stream water quality can therefore influence ionization state, which is important because the unionized forms a more lipophilic and have a greater propensity to cross cellular membranes. Consequently, the unionized forms are hypothetically more toxic. I completed toxicity tests in the laboratory using various contaminants as model ionizable compounds over a gradient of environmentally-relevant surface water pH and then related measured toxicological endpoints to observed pH of surface waters using both discrete and probabilistic ecological risk assessment approaches. The result of my studies clearly demonstrated that site-specific pH may influence the toxicity of ionizable contaminants. Potential modifications to conceptual frameworks of ecological risk assessment for ionizable contaminants are suggested so that uncertainty can be reduced.Item Development and application of high-throughput sample preparation methods for solid matrices.(2014-09-05) Aguilar Lázaro, Lissette.; Usenko, Sascha.; Ecological, Earth, and Environmental Sciences.; Brooks, Bryan W.; Oziolor, Elias M., 1990-; Matson, Cole W.; Robinson, Eleanor Marian.; Trumble, Stephen John.; Williams, E. Spencer.; Subedi, Bikram.; Bigorgne, Emilie.; Horstmann-Dehn, Lara.; Baylor University. Institute of Ecological, Earth and Environmental Sciences.This research presents the development and application of high-throughput sample preparation methods for the analysis of organic and inorganic contaminants from solid samples. The approach presented evaluates conventional methods to identify potential areas of improvement. In this sense, conventional methods serve as a framework for the development of high-throughput sample preparation methods. In general, improvements include expansion of target analyte list thereby increase the environmental applicability, reduction of sample preparation steps, and as a result, reduction of sample preparation time. The analytical bottleneck is often associated with sample preparation, especially in the analysis of organic contaminants from environmental samples. Many environmental analytical chemistry methods can be broken down into one or more sample preparation steps followed by one or more chemical analysis steps. Improvement of historical methods has focused on the development of advance instrumentation (i.e. focusing on the chemical analysis). However, recent efforts have focused on the overall reduction of time and/or steps associated with sample preparation. For example, post-extraction cleanup adsorbents can be incorporated into the pressurized liquid extraction step to perform a selective pressurized liquid extraction (SPLE). SPLE methods significantly reduced sample preparation time, solvent requirements, and waste production. Specific examples presented in this dissertation include: 1) the development and application of SPLE methods for the analysis of organic contaminants from sediments and biological tissues; 2) the development and application of a simplified acid digestion method for the analysis of mercury and selenium in rare samples of Pacific walrus (Odobenus rosmarus divergens) muscle (L. dorsi). These examples illustrate the approach for the development of high-throughput sample preparation methods that have successfully combined techniques into a single method, and/or eliminated post-extraction cleanup steps. The availability of these methods increases laboratory’s capacity and preparedness to analyze rapidly large volumes of samples. These methods could find use in routine analysis and monitoring studies of environmental samples, food and pharmaceutical industries, agriculture, toxicology studies, and forensic sciences among others. Lastly, this dissertation discusses a few opportunities that lay ahead for improvement and development in sample preparation.Item Influence of pH and total dissolve solids on harmful algal blooms of Prymnesium parvum.(2013-05-15) Prosser, Krista Noel.; Brooks, Bryan W.; Environmental Science.; Baylor University. Dept. of Environmental Science.Harmful blooms of Prymnesium parvum in inland waters continue to expand, in part, due to anthropogenic influences and climate change. This thesis examines influences of pH and total dissolved solids (TDS) on P. parvum blooms, growth, and toxicity to aquatic life. Chapter 1 evaluated pH effects on P. parvum bloom development and toxicity by manipulating in situ limnocorrals during 21 d pre-bloom and bloom development experiments. Though neutral pH levels preempted P. parvum bloom development, higher pH resulted in bloom formation and ambient toxicity. Chapter 2 examined whether TDS with major ionic composition associated with hydraulic fracturing influenced P. parvum growth and toxicity across nutrient conditions. Though no growth was observed at 130 mg/L, higher treatment levels of TDS stimulated P. parvum growth and increased acute toxicity to fish. Such novel observations provide pH and TDS thresholds for potentially supporting management of P. parvum growth and acute toxicity in inland waters.Item Towards an understanding of pharmaceutical exposure and bioaccumulation in effluent-dependent systems.(2014-09-05) Du, Bowen.; Brooks, Bryan W.; Chambliss, C. Kevin.; Ecological, Earth, and Environmental Sciences.; German Environmental Specimen Bank; TCEQ; Snyderville Basin Water Reclamation District; Carollo Engineers; City of Waco; CRASR at Baylor; Baylor Stable Isotope Lab; U.S. EPA; SETAC NA; USDA; Baylor University. Institute of Ecological, Earth and Environmental Sciences.Environmental risks of pharmaceuticals and other contaminants of emerging concern (CECs) are not well understood due to relatively limited information on fate, transport, exposure, bioaccumulation and effects. The objective of this research was to improve understanding of the relationships among CEC accumulation in aquatic organisms through developing robust analytical methods and studying exposure and bioaccumulation. In chapter 2, an isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was successfully developed and applied to identify 15 pharmaceuticals and 2 pharmaceutically-active metabolites in fish tissues. The method was successfully applied to trout samples collected from different river locations in Utah, USA. In chapter 3, occurrence, removal and discharge of selected CECs were compared between municipal and on-site treatment systems receiving a common wastewater influent. Such a unique study design was conducted at the Baylor Wastewater Research Program site at the Waco Municipal Area Sewerage System, Waco, Texas, USA. This novel comparative examination of centralized and decentralized effluent quality also employed a fish plasma model approach to estimate the therapeutic hazards of pharmaceuticals in each effluent discharge. Within investigated treatment systems, the septic system consistently possessed the lowest water quality and therapeutic hazards. Coupling a constructed subsurface wetland may lower ecological risks associated with effluent discharge from septic systems. Occurrence and bioaccumulation of pharmaceuticals and other CECs were then examined in a common snail (Planorbid sp.) grazer and periphyton from the North Bosque River in central Texas, USA, during a historic drought when stream flow was effluent-dependent. Limited observations of pharmaceuticals in periphyton compared to water and snail samples suggested that water exposure represented the primary route of pharmaceutical exposure to Planorbid sp. in the North Bosque River. In chapter 5, a fish plasma model, initially developed from laboratory studies and applied in chapter 3 to assess effluent quality, was tested to examine observed versus predicted internal doses of select pharmaceuticals in the North Bosque River. In addition, characterization of trophic transfer for select pharmaceuticals suggested that uptake of ionizable pharmaceuticals by aquatic organisms in this effluent-dependent wadeable stream more likely resulted from inhalation than dietary exposure.