<p> The coastal watersheds around Massachusetts Bay are home to millions of people, many of whom recreate in coastal waters and consume locally harvested shellfish. Epidemiological data on food-borne illness and illnesses associated with recreational water exposure are known to be incomplete. Of major food categories, seafood has the highest recorded rate of associated foodborne illness. In total, the health impacts from these marine-sourced risks are estimated to cost millions of dollars each year in medical expenses or lost productivity. When recorded epidemiological data is incomplete it may be possible to estimate abundance or prevalence of specific pathogens or toxins in the source environment, but such environmental health challenges require an interdisciplinary approach. </p><p> This dissertation is divided into four sections: (1) a presentation of two frameworks for organizing research and responses to environmental health issues; (2) an exploration of human population dynamics in Massachusetts Bay coastal watersheds from 2000 to 2010 followed by a review of, and identification of potential indicators for, five marine-sourced risks: <i>Enterococcus </i> bacteria, <i>Vibrio parahaemolyticus</i> bacteria, Hepatitis A Virus, potentially toxigenic <i>Pseudo-nitzschia</i> genus diatoms, and anthropogenic antibiotics; (3) an introduction to environmental health research in the context of a changing data landscape, presentation of a generalized workflow for such research with a description of data sources relevant to marine environmental health for Massachusetts Bay; and (4) generation of models for the presence/absence of <i>Enterococcus</i> bacteria and <i>Pseudo-nitzschia delicatissima</i> complex diatoms and model selection using an information-theoretic approach. </p><p> This dissertation produced estimates of coastal watershed demographics and usage levels for anthropogenic antibiotics, it also demonstrated that <i> Pseudo-nitzschia delicatissima</i> complex diatoms may be present in any season of the year. Of the modeling generation and selection, the <i> Enterococcus</i> model performed poorly overall, but the <i>Pseudo-nitzschia delicatissima</i> complex model performed adequately, demonstrating high sensitivity with a low rate of false negatives. This dissertation concludes that monitoring data collected for other purposes can be used to estimate marine-sourced risks in Massachusetts Bay, and such work would be improved by data from purpose-designed studies.</p>

The Lower Colorado River Giant Salvinia Task Force has tried a series of physical and chemical activities in an effort to control and eradicate giant salvinia (Salvinia molesta) since 1999. Because these efforts have not produced satisfactory results, biological control using the weevil Cyrtobagous salviniae (Coleoptera: Curculionidae) was applied on the Lower Colorado River by the Animal and Plant Health Inspection Service, United States Department of Agriculture offices in California and Arizona. They released the weevil at four sites in the summer of 2003, four sites in 2004, and eight sites in 2005.We monitored physico-chemical and biological parameters at release and 10 m and 1 km down stream from release sites. Weevils established their colony in the field, but control has not been determined. Integrated pest management (physical, chemical, and biological methods) will be essential for successful management of salvinia in the Lower Colorado River.The low temperature resistance and survival rates of the weevils were tested under three different diurnal temperature regimes (5 to 15 oC , 10 to 20 oC , and 15 to 25 oC ) and two different salvinia densities. At the low temperature range, the survival rate of the weevil was sharply decreased. The relationship between low temperature resistance of weevils and giant salvinia population was tested at the 5 to 15 oC range. The experiment was conducted at three different giant salvinia populations (0, 1, and 3 salvinia per container). The salvinia density had no significant effect on the survival of the weevil.To examine a more efficient method of biological control, we conducted a nitrogen fertilizer experiment on the river. Our goal was to demonstrate that plants fertilized with nitrogen would support a faster growing population of C. salviniae. In the Lower Colorado River, the weevil successfully survived winter and dispersed down the river.

Increasing atmospheric levels of carbon dioxide (CO2) and the potential impact on climate change has caused an increased effort to more accurately quantify terrestrial sources and sinks. Semiarid grasslands cover a significant portion of the Earth's land surface and may be an important sink for atmospheric CO2. This study was conducted to examine the role semiarid grasslands play in the carbon cycle. The relation between surface reflectance and temperature obtained from satellite imagery was used to determine a Water Deficit Index (WDI) to estimate distributed plant transpiration rates for a point in time. Due to the relationship between transpiration and plant CO2 uptake, WDI was directly related to CO2 flux. Satellite images were acquired for a five-year period (1996-2000) during which transpiration and net CO2 flux were measured for a semiarid grassland site in southeastern Arizona. Manual and automatic chamber data were also collected in 2005 and 2006 and used to assess the spatial variability of nighttime soil respiration. Spatial analysis showed the most influential factor affecting nighttime respiration was aspect, where flux from North-facing slopes was significantly (P < 0.05) higher than on South-facing slopes. A strong linear relationship (R2 = 0.97) existed between WDI-derived instantaneous net CO2 flux and daytime net CO2 flux estimates, and was used to generate maps of distributed daytime net CO2 flux. A linear relationship (R2 = 0.88) was also found between daytime and nighttime net CO2 flux, and used in combination with maps of daytime net CO2 flux to create maps of daily net CO2 flux. This study indicated that remote sensing offers an operational, physically-based means of obtaining daily net CO2 flux in semiarid grasslands.

Nanoparticles are an emerging contaminant of concern. They are used in many products and industries and, due to a lack of regulation, are entering the natural environment through our waste streams. Studies examining the transport of nanoparticles in porous media have observed divergences between data and theory. Transport data also varies greatly across studies, adding complexity to the determination of the important factors in nanoparticle transport. These main factors and key areas of deviation from theory were determined by comparing and contrasting various studies of nanoparticle transport. To further examine behavior and retention mechanisms of nanoparticles in porous media, nano-sized titanium dioxide (nano-TiO₂) was used in miscible-displacement transport experiments, followed by force measurements by Atomic Force Microscopy (AFM) between the same nanoparticles and porous media. Ionic strength ranged from 0.0015 - 30 mM, and solution chemistries were varied from pH 4.5 (favorable attachment) to 8 (unfavorable attachment). To determine the possible presence of secondary minima attachment, detachment transport experiments were performed for the unfavorable attachment conditions. Calculations were performed using DLVO theory, which is often used to describe colloid and nanoparticle retention, and compared to measured force profiles. Mass recoveries for the transport experiments ranged from 28-80%. Retention under favorable conditions was much greater than under unfavorable conditions, as was anticipated. Detachment was observed, indicating the potential presence of secondary minima. Large adhesive forces were measured by AFM and were affected by solution chemistry. Force profiles were highly variable, especially under unfavorable attachment conditions. Secondary minima were observed, even at a 0.0015 mM ionic strength. DLVO theory, while qualitatively accurate, largely under-predicted attractive and repulsive forces and their range of influence. Variability in the force profile and potential conformational changes of nanoparticle aggregates were postulated to be influential in nanoparticle transport. Retention of the nanoparticles under unfavorable conditions was postulated to involve secondary minima and the effects of surface roughness. These mechanisms, which are not represented in DLVO theory, are likely causes of the observed divergence of experimental results from theory. Improved understanding of retention mechanisms will hopefully enhance our understanding of the potential impacts of nanoparticles on the natural environment.

<p>Bioremediation has gained considerable attention over the past few decades as an effective and relatively inexpensive method of cleaning up contaminated environmental sites. Specific methods for bioremediation could involve ex situ pump-and-treat processes or in situ treatments that add either nutrients and substrates to stimulate microbial degradation of contaminants (biostimulation) or microbes that have high degradation potentials (bioaugmentation). Although in situ bioremediation processes generally offer more advantages than ex situ methods, there are concerns with the current in situ methods that limit their effectiveness. For example, a major concern in bioaugmentation is the effect of the addition of large quantities of microorganisms that are foreign to the site. This may lead to significant changes in microbial community structure and a long-term instability in ecosystem integrity. Furthermore, the degradative activities of such foreign microbes may be compromised when introduced into an unfamiliar environment during bioaugmentation, thereby resulting in a lower bioremediation potential. </p><p>Horizontal gene transfer (HGT) is a widespread phenomenon in the prokaryotic kingdom that occurs readily under harsh environments where genetic adaptation is required for the survival of microorganisms. HGT could be useful for bioremediation to shift microbial communities in favor of degrading xenobiotics, persistent organic compounds, and emerging contaminants. In fact, it has been noted that HGT has repeatedly occurred naturally in contaminated sites to aid in bacterial adaptation to organic pollutants. Therefore, instead of introducing large quantities of foreign microbes capable of degrading the contaminant as seen in conventional bioaugmentation, we can introduce small amounts of bacteria harboring genes encoding for enzymes that degrade the contaminant of interest and stimulate in situ HGT of those degradative mobile genetic elements to the native bacterial community. This proposed method is termed genetic bioaugmentation and may provide a safer way of bioaugmentation than using genetically engineered microbes. However, the mechanisms and effects of HGT must be extensively characterized prior to this application with a focus on how to enhance HGT occurrences and improve the resulting degradation potential. This method should be especially useful for the bioremediation of emerging anthropogenic contaminants.</p><p>In this study, the TOL plasmid, which includes genes for the degradation of xylenes, toluene, and related species, is used as a model system with toluene as the model contaminant. While toluene is not considered a persistent emerging organic contaminant, the TOL plasmid is an ideal model HGT system because it falls under a diverse family of degradative plasmids that frequently undergo HGT and its degradation pathways are well documented. Using a green fluorescent protein expression system, we have demonstrated that the TOL plasmid from Pseudomonas putida BBC443 has been successfully transferred to several &#947;-proteobacteria strains, e.g. Pseudomonas fluorescens, Serratia marcescens, and Escherichia coli DH5&#61537;. However, some transconjugants that harbor the TOL plasmid do not have the ability to degrade and utilize toluene as the sole carbon source even though all of the necessary genes have been successfully transferred. Further investigations have shown that such transconjugants require additional external factors for toluene degradation such as alternative carbon sources. For example, the effects of glucose addition on the toluene degradation rates of the various strains are shown in Figure 1. The addition of glucose at most concentrations resulted in significant enhancement of the toluene degradation rates in all transconjugants while its effect on the donor strain, P. putida, was not as pronounced. Similar results were obtained when varying dilutions of the nutrient-rich Luria-Bertani medium was added. Furthermore, exposure of transconjugants to different pH values and nitrogen sources indicated that pH 8 and ammonia were the most favorable conditions for gene functionality. The mechanisms of enhancement by such changes in environmental conditions are currently being studied. </p><p>While other parameters should be studied in depth prior to the field application of genetic bioaugmentation, the results from this study indicate that successful HGT events coupled with the desired degradative phenotype can be promoted by small changes in environmental conditions. With further research, there is potential for genetic bioaugmentation to be applied towards remediating emerging contaminants in various environments such as groundwater and soil. Overall, this study will illustrate that genetic bioaugmentation may provide an effective but safer, cheaper and less invasive method for bioremediation.</p> / Dissertation

<p> Metals such as arsenic, cadmium, beryllium, and nickel are known human carcinogens; however, other transition metals, such as tungsten, remain relatively uninvestigated with regard to their potential carcinogenic activity. Tungsten production for industrial and military applications has almost doubled over the past decade and continues to increase. This work demonstrates tungsten&rsquo;s ability to induce carcinogenic-related endpoints including cell transformation, increased migration, xenograft growth in nude mice, and the activation of multiple cancer related pathways in transformed clones as determined by RNA sequencing. Human bronchial epithelial cell line (BEAS-2B) exposed to tungsten developed carcinogenic properties. In a soft agar assay, tungsten-treated cells formed more colonies than controls and the tungsten-transformed clones formed tumors in nude mice. RNA sequencing data revealed that the tungsten-transformed clones altered the expression of many cancer-associated genes when compared to control clones. Genes involved in lung cancer, leukemia, and general cancer genes were deregulated by tungsten. </p><p> In order to examine the epigenetic mechanisms that mediate tungsten&rsquo;s tumorigenicity, we investigated if tungsten alters the levels of global histone methylation and if these changes are due to tungsten influencing the histone demethylases. We found that cells acutely treated with tungsten displayed significantly increased numbers of H34me3 and H3K9me2 histone marks on a global scale. This increase was due to down-regulation in the protein levels of the histone demethylases JMJD1A and JARID1A. The increase in global histone methylation remained when cellular SAM levels were depleted. The decrease in histone demethylase proteins was found to be due to a reduction in their gene expression. Epigenetic alterations induced by tungsten in the histone demethylase genes caused the repression. </p><p> We also evaluated insoluble tungsten, tungsten oxide (WO₃). WO₃ is an occupational exposure hazard. The primary route of WO₃ exposure is inhalation and WO₃ is known as a pulmonary irritant. WO₃ exposure led to stochastic results, which were likely due to the random effects of the particles. </p><p> Given the carcinogenic potential of other metals, it is likely that tungsten will exert carcinogenic outcomes. This study evaluates cancer-associated endpoints induced by tungsten exposure in both <i>in vitro</i> and <i> in vivo</i> models. To evaluate the mechanisms that underlie tungsten-induced carcinogenesis, alterations to the epigenome are assessed. Arsenic, cadmium, nickel, and chromium (VI) are poor mutagens; however, they exert their carcinogenic potential via epigenetic mechanisms. The literature is currently void of investigations examining the epigenetic effects of tungsten. Given the evidence characterizing metals as epimutagens, it is likely that tungsten toxicity and carcinogenesis is mediated via epigenetic mechanisms.</p>

<p> Flow regime, the magnitude, duration and timing of streamflow, controls the development of floodplain landforms on which riparian vegetation communities assemble. Streamflow scours and deposits sediment, structures floodplain soil moisture dynamics, and transports propagules. Flow regime interacts with environmental gradients like climate, land-use, and biomass-removing disturbance to shape riparian plant distributions across landscapes. These gradients select for groups of riparian plant species with traits that allow them to establish, grow, and reproduce on floodplains &ndash; <i>riparian vegetation guilds.</i> Here I ask, <i>what governs the distributions of groups of similar riparian plant species across landscapes?</i> To answer this question, I identify relationships between riparian vegetation guilds and communities and environmental gradients across the American West. In Chapter One, I discuss guild-based classification in the context of community ecology and streams. In Chapter Two, I identified five woody riparian vegetation guilds across the interior Columbia and upper Missouri River Basins, USA, based on species&rsquo; traits and morphological attributes. I modeled guild occurrence across environmental gradients, including climate, disturbance, channel form attributes that reflect hydrology, and relationships between guilds. I found guilds&rsquo; distributions were related to hydrology, disturbance, and competitive or complementary interactions (niche partitioning) between co-occurring guilds. In Chapter Three, I examine floodplain riparian vegetation across the American West, identifying how hydrology, climate, and floodplain alteration shape riparian vegetation communities and their guilds. I identified eight distinct plant communities ranging from high elevation mixed conifer forests to gallery cottonwood forests to <i>Tamarisk</i>-dominated novel shrublands. I aggregated woody species into four guilds based on their traits and morphological attributes: an evergreen tree guild, a mesoriparian shrub guild, a mesoriparian tree guild, and a drought and hydrologic disturbance tolerant shrub guild. Communities and guilds&rsquo; distributions were governed by climate directly, and indirectly as mediated through streamflow. In Chapter Four, I discuss the utility of guild-based assessments of riparian vegetation, current limitations to these approaches, and potential future applications of the riparian vegetation guild concept to floodplain conservation and management. The classification of vegetation into functional trait-based guilds provides a flexible, framework from which to understand riparian biogeography, complementing other models frameworks for riparian vegetation.</p>

Due to the history of hardrock mining in the southwestern United States, environmental contamination at legacy mine sites is an ongoing problem. Mine wastes, the primary source of contamination, particularly tailings are the uneconomical byproducts of hardrock mining that are generally deposited near a mine. Due to the geochemistry of sulfide orebodies (the source of many valuable metals including Zn, Pb, and Cu), the residues of sulfide ore extraction often have high concentrations of toxic contaminants such as As, Pb and Cd, which are released into the environment due to chemical and mineralogical changes following exposure of the tailings to oxygen and water. The secondary precipitates formed by tailings oxidation are primarily fine particles and due to the dry climate of desert southwestern US, the lack of soil moisture and structure, and the lack of vegetative cover on the tailings surface, contaminated dusts consisting of these secondary precipitates can be generated and spread to nearby communities by wind erosion of the tailings surface. Ingestion or inhalation of these wind-borne dusts can cause health problems resulting from contaminant exposure that depend on the lability of the contaminants in the biofluids that the dust particles come into contact with, a parameter that can be determined using in vitro bioaccessibility assays. This research project concentrated on a tailings pile at the Iron King Mine and Humboldt Smelter Superfund site (IKMHSSS), a disused mine site located in the town of Dewey-Humboldt, AZ. Previous studies at IKHMSSS have revealed that the top meter of the tailings pile encompasses the entirety of a general pyrite (FeS₂) weathering sequence, with the lower levels dominated by pyrite and other minor sulfide minerals (e.g. ZnS, FeAsS, PbS), an intermediate layer dominated by sulfate salts, ferrihydrite and other amorphous Fe(III) oxyhydroxides, and a surface layer dominated by crystalline tertiary precipitates such as jarosite (KFe₃(SO₄)₂(OH)₆). Samples were taken from seven distinct layers differentiated by color, texture and morphological characteristics, and the PM₁₀ fraction of each sample was isolated using a cyclone dust generator. The PM₁₀ samples were then treated with synthetic biofluids designed to mimic physiological conditions present in the human respiratory system and gastrointestinal tract, and the aqueous concentations of As, Fe, Pb and SO₄ were measured at successive time points to determine the chemical kinetics of contaminant release into the synthetic interstitial fluids. The solution data was complemented by x-ray diffraction and x-ray absorption spectroscopy experiments performed at the Stanford Synchrotron Radiation Laboratory. These studies found that the in vitro bioaccessibility of both Pb and As was highest for the unweathered deep tailings samples and lowest for the partially-oxidized transition zone samples. The primary factors found to control bioaccessibility were the presence of labile Fe³⁺ and SO₄²⁻ in the samples, both of which are required to drive the precipitation of secondary minerals capable of incorporating trace elements such as As and Pb into their structure.

Perfluorinated compounds (PFCs) are a class emerging contaminants that have been implicated in bladder cancer and other human health problems. Due to the widespread exposure to humans, persistence in the environment, and their negative effects on human health, we need to develop a treatment method to degrade these chemicals into harmless species. Perfluorooctanoic acid (PFOA, C₈HF₁₅O₂) is one of the top representatives of PFCs commonly reported to be found in water sources, hence it was chosen as the model compound and focus in this project. We examined an iron-activated persulfate oxidation (IAPO) method to decompose aqueous PFOA, and tested the reaction under various conditions, including: oxic, anoxic, and anoxic/dark conditions. We observed 𝑐𝑎. 64% of PFOA (beginning with solution phase concentration fo 𝑐𝑎. 1.64*10⁻⁶ mol L⁻¹) was transformed after four hours under anoxic conditions. This was about seven times higher than measured under oxic conditions, and about five times higher than anoxic/dark conditions. Therefore, we concluded that IAPO can decompose PFOA at 25 °C, the ambient condition temperature. This method can potentially be used as an inexpensive and environmentally-friendly PFOA remediation method, with potential application to other PFCs in groundwater and soil. In addition, this method may be applicable for surface water sources such as potable water reservoirs, waste water effluent, and extracted groundwater.

<p> This study assed the impacts of 17&alpha;-ethinylestradiol in Heterandria formosa. These impacts were addressed through chronic, life-cycle exposures of individuals and populations of least killifish to 0, 5, or 25ng/L EE2. Development, growth, reproduction, survival, and population dynamics were monitored and evaluated for EE2 effects on their health, reproductive success, and population sustainability. </p><p> Exposing pairs of least killifish to EE2 resulted in similar increases in time-to-sexual maturity for both sexes. The EE2-exposure had a sex-dependent effect on body size, with standard lengths and wet weights of females significantly reduced and standard lengths of males markedly increased. Offspring production decreased by 50% and 75% for fish exposed to 5 and 25ng/L EE2 respectively. Sexual development was even further delayed in EE2-exposed offspring of exposed fish. EE2-exposure also affected the gonadal and liver development in least killifish. Males exposed to EE2 had delayed sperm maturation and severe intersex (a phenomenon in which eggs and sperm are produced within the same male). These effects were more severe at the 5ng/L than at the 25ng/L EE2 concentration. Exposing females to EE2 resulted in delayed egg maturation. Furthermore, EE2 exposure resulted in changes in liver morphology in both males and females. For both the delay in egg maturation and the changes in liver morphology, the effects were strongest at the higher EE2 concentration. </p><p> Effects of chronic EE2-exposure on populations were assessed at the 5ng/L concentration. EE2-exposure caused significant reductions in population size and population growth rates, and caused other changes in population dynamics. Exposed populations had a pronounced female-biased sex ratio and significantly reduced abundances of males and newborns. These responses were observed within one breeding season. </p><p> This is the first report demonstrating a variety of negative impacts resulting from chronic EE2-exposure in least killifish at both the individual and population levels. Effects were evident in all stages of development and in all life history stages. This study demonstrated that, similar to the case for other fish, live-bearing fish are likely to be severely affected when their environment becomes contaminated by EE2 and that steps are needed to prevent exposure to this endocrine disrupting chemical.</p>