The toxicity of ammonia has become an issue in recent years, especially in the Chesapeake Bay watershed. Currently, the EPA has set a chronic criterion of 0.035 mg/L (unionized ammonia). The chronic criterion is a four-day average concentration that cannot be exceeded more than once every three years. However, a lack of data exists on the toxicity of ammonia to saltwater organisms. Prior to this research, the chronic criterion was based on two saltwater and four freshwater organisms. This research was conducted to add additional data so more appropriate criteria may be set. Two saltwater fish, the Summer Flounder (Paralichthys dentatus), and the Atlantic Silverside (Menidia menidia) and one invertebrate, the Quahog Clam (Mercenaria mercenaria) were tested for acute toxicity to ammonia. The acute tests performed on the Summer Flounder (2 months old) were 48 and 96-hour tests performed in both synthetic seawater and natural seawater. Seven-day chronic tests were also performed on the Summer Flounder using synthetic seawater. Both 48 and 96-hour acute tests were performed on the Atlantic Silverside (10-14 days old.) using natural seawater. Both 48 and 96-hour acute tests were performed on the Quahog Clam (5mm shell height) using synthetic seawater. The 48-hour LC50s for the Summer Flounder in synthetic and natural seawater were 1.22 mg/L and 1.09 mg/L, respectively. The 96-hour LC50s for the Summer Flounder in synthetic and natural seawater were 1.07 mg/L and 0.889 mg/L, respectively. The 7-day chronic NOEC was 1.37 mg/L. The 48 and 96-hour LC50s for Atlantic Silverside in natural seawater were 1.52 mg/L and 1.18 mg/L, respectively. The 48 and 96-hour LC50s for Quahog Clam in synthetic seawater were 216 mg/L and 36.6 mg/L, respectively. The acute-chronic ratio for the Summer Flounder was 2.27. The refined chronic criterion was 0.081 mg/L based on this research and the research of others. Summer Flounder were more sensitive to ammonia in natural seawater than synthetic seawater. However, Atlantic Silverside showed no difference in sensitivity. / Master of Science

Ammonia is known to be toxic to aquatic organisms. The national water quality criteria for ammonia in the marine environment have been established to protect aquatic organisms from the toxicity of ammonia. Discharge into Chesapeake Bay has not yet been regulated under this criteria. Ammonia limits of 1-2 mg/L total ammonia have been proposed for the marine waters in Virginia based on the national criteria of 0.035 mg/L of un-ionized ammonia. The limits have been questioned because the criteria were calculated using toxicity data from both freshwater and saltwater species, rather than solely from saltwater species. More ammonia toxicity tests need to be conducted to expand the database with saltwater species in order to develop a reliable and appropriate limits for ammonia discharge. Two saltwater species, one marine fish, Atlantic silverside (Menidia menidia), and one marine invertebrate, ghost shrimp (Palaemonetes pugio), were tested in acute and 7-day chronic tests. The acute tests for the Atlantic silverside were performed at three levels of salinity in order to develop a better understanding of the relationship between ammonia toxicity and salinity levels. The acute LC50values for both species were determined and compared to values in the literature. The 48-hour LC50 values for the Atlantic silverside were 1.50, 1.17, and 1.08 NH3 mg/L at salinities of 14, 22, and 30 ppth, respectively. The 96-hour LC50 for the ghost shrimp was 1.66 NH3 mg/L. The species mean acute values (SMAVs) for the Atlantic silverside (2% difference) and the ghost shrimp (31% difference) were compared to previous test results. The no-observed-effect-concentration (NOEC) was 0.48 NH3 mg/L for the Atlantic silverside based on growth, and 0.33 NH3 mg/L for the ghost shrimp based upon growth. The acute-chronic ratio for the ghost shrimp was 7.56. The refined national chronic criterion of un-ionized ammonia was 0.056 mg/L according to the test data from this research. / Master of Science

Increased salinization of inland freshwater resources is present on a global scale, but is pro- gressing rapidly in the densely populated Mid-Atlantic United States. This phenomenon threatens aquatic health, ecosystem services and functionality, and can alter the percep- tion of potable drinking water. The Occoquan watershed, located in Northern Virginia has experienced rapid urbanization across recent decades and is now confronted with rising salinization. Various stakeholders in the area have focused efforts to quantify the drivers of salinization in order to take corrective action to preserve this resource. To aid these efforts, urbanization's relationship with in-stream salinity was analyzed, where its exerted influence was found to be dependent upon overland hydrologic flowpaths which connect urban areas to stream networks. The analysis was then broadened to Multiple Linear Regression models of urban and climatological drivers to statistically quantify each driver's relative influence on in-stream salinity. The models demonstrated that urbanization is the primary driver, where rainfall and roadway deicer application were also found to be significant. The model was then used to predict the magnitude of salinization in the Occoquan watershed to a time horizon of 2040 based on expected population growth as well as two anticipated climate scenarios. Finally, the analytical framework produced in this research was generated with scalability in mind, such that it can potentially be utilized as a watershed-scale screening tool accross the Mid-Atlantic, to inform proactive, regionally appropriate management decisions. / Master of Science / Increased salinization of inland freshwater resources is present on a global scale, but is progressing rapidly in the densely populated Mid-Atlantic United States. Driven by the engineered systems that define our modern world, this phenomenon threatens aquatic health, ecosystem services and functionality, and can alter the perception of potable drinking water. The Occoquan watershed, located in Northern Virginia has experienced rapid urbanization across recent decades and is now confronted with rising salinization. Various stakeholders in the area have focused efforts to quantify the drivers of salinization in order to take corrective action to preserve this resource. The analyses completed in this body of work act to model and statistically analyze the drivers which foster salinization in the Occoquan. The analyses demonstrated that while climatological factors drive salinity in the Occoquan, urbanization is the primary driver, where its exerted influence is dependent upon overland hydrologic flowpaths which connect urban areas to stream networks. Further analyses were completed to project salinization to a time horizon of 2040 based on expected population growth as well as two anticipated climate scenarios to predict the magnitude of salinization in the Occoquan watershed in decades to come. These results indicated that anticipated levels of in-stream salinity will increase across most sampling stations in coming years. Finally, the analytical framework produced in this research was generated with scalability in mind, such that it can potentially be utilized as a watershed-scale screening tool accross the Mid-Atlantic, to inform proactive, regionally appropriate management decisions.

Bitumen extraction in the Athabasca oil sands causes significant disturbance of landscapes originally rich in wetland and forest ecosystems, which now require reclamation as mandated by the Alberta Government. However, most research to date has focused on upland-forest ecosystems with little attention on wetland-peatland ecosystems, which are considered more challenging to construct due to salinization potential from ubiquitous salts used in the oil sands extraction and treatment processes; with particular focus on elevated Na+ due to its detrimental ecological effects. Syncrude Canada Ltd. (SCL) has constructed an upland-wetland system, the Sandhill Fen Watershed (SFW), to advance the understanding of wetland reclamation in the oil-sands region. The SFW is a highly engineered and managed system. Water is supplied from an artificial fresh water source and drainage is enhanced through a constructed surface outlet and an under-drain system intended to provide a downward hydraulic gradient to inhibit the upward movement of salts from the underlying waste material. The objective of this research is to understand the hydrochemical response of the SFW to variations in hydrological management with respect to sources, flow pathways and major chemical transformations of water as it moves throughout SFW. Through surface and pore water sampling, the electrical conductivity and major ions were measured throughout the growing season of 2013 and 2014. Results indicate that the combination of freshwater inflow, flushing of the system with the outflow pump and open underdrains in 2013 kept the overall salinity within the SFW relatively low, with most lowland sites under 1000 µS/cm. Major ion results indicate that most water throughout the SFW classified as Ca-HCO3 or Ca-SO4 in 2013, with higher concentrations in the uplands however Na+ concentrations did not exceed 250 mg/L at any sampling sites. With minimal management in 2014 and consequent limited freshwater input and flushing of the system, the overall salinity of the SFW increased considerably and EC at most sites in lowlands exceeded 1000 µS/cm. Na+, Ca+2, SO4-2 and HCO3- concentrations increased across the SFW, with higher concentrations in the uplands than the lowlands. Although most sites classified as Ca-SO4, the most notable change in 2014 was the presence of several Na+ “hotspots” along the southern hummocks in the SFW, where water samples classified as Na-SO4 and Na+ concentrations reached as high as 886 mg/L. Results provides evidence of modelled upward movement of Na+ from underlying waste materials and subsequent seepage from hummocks with limited pump management in the SFW. / Thesis / Master of Science (MSc)

<p> Flows in channels or estuaries may exhibit variations in density arising· from differences in temperature, salinity or suspended solids. In the absence of significant vertical mixing, stable, discrete layers may form with distinct density interfaces. </p> <p> This thesis presents a computational approach for the analysis of two-layer, vertically stratified, one-dimensional horizontal flows in open channels. A variety of such problems are identified and a critical survey of the existing literature is presented. A framework is defined against which these problems are classified and decomposed into analytical problems of the simplest possible scope. Based on the conditions that lead to changes in flow characteristics, four research areas are examined. These are energy balance, interfacial hydraulic jump, lock exchange flows, and long transitions. Although restricted to essentially one-dimensional flows, the analytical study of these four areas is extended to allow for non-uniform velocity distribution the introduction of boundary-layer displacement thicknesses and correction factors for kinetic energy and momentum. Also, a significant feature of the study is the ability to handle channels of arbitrary cross-sectional geometry. </p> <p> The basic philosophy of the approach followed in this study is to develop a relatively simple and computationally econaoical procedure which is applicable to a wide variety of problems involving channels systems of arbitrary geometry and boundary conditions. A library of computer subroutines provides a convenient means of developing an open-ended system of computational techniques for the solution of a wide range of problems. Such a library of computational algorithms may also promote. cooperation and collaboration among researchers and engineers concerned with stratified flow hydraulics. Such algorithms should provide solutions for frequently recurring problems, should be mutually compatible and allow the construction of relatively complex analytical models in a modular fashion. A comprehensive library of routines is developed which consists of fourty-four subroutines and functions. This evolves as a well-defined hierarchy of algorithms in which the most basic algorithms are nested within the more sophisticated ones to the sixth or seventh level. </p> <p> The computational algorithms are tested for theoretical and computational performance. Numerical predictions are compared with available experimental and field data. Moreover, an experimental program is described which is designed and carried ·out to verify the numerical predictions obtained for the first of the above-mentioned four topics. </p> <p> An important aspect of the study is the illustration of the application of the routines in the solution of typical practical problems such as selective withdrawal from stratified water bodies and recirculation of cooling water from power plants. In addition, to facilitate utilization of the programs by others, complete documentation and listings are provided. </p> / Thesis / Doctor of Philosophy (PhD)

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Salinization has been identified as an increasing threat to freshwater mussel diversity in recent years. Native mussels have been observed to display reduced salinity tolerance in comparison to some invasive bivalve species, but methods by which organismal tolerance is achieved are not well understood. This study was designed to compare the behavioral and physiological responses of the native Lampsilis ovata to that of the invasive Corbicula fluminea. Lampsilis were found to exhibit strong behavioral avoidance to salinity exposure, whereas Corbicula displayed very weak avoidance to comparable salinity concentrations followed by indications of osmotic conformation through physiological mechanisms. Prolonged valve closure in Lampsilis could translate to adverse consequences related to feeding, waste removal, and energetics. Alternatively, while physiological osmotic conformation in Corbicula is associated with increased energetic costs, it allows continued respiration and feeding. These differences could convey a competitive advantage with the increasing prevalence and severity of freshwater salinization events.

Salt stress is a global problem that limits agricultural production. The early responses to salinity, independent of toxic shoot-ion accumulation, are still largely unknown. Here, optimised salt treatment and high-throughput phenotyping protocols were developed and used to examine the natural variation in the early responses to salt stress of 191 Arabidopsis thaliana accessions. Common and novel traits of plants grown under salt treatment were captured through time using RGB and chlorophyll fluorescence imaging. Phenotypic data was combined with the Arabidopsis 10M SNP markers for genome-wide association studies to identify genetic components underlying the early responses to salt stress. The most promising candidate loci were selected based on association strength, allele frequency and number of traits associating to the same locus. In silico analysis highlighted interesting allelic variations across the identified loci, and by phenotypically characterising the candidate gene mutants under salt stress, the associations were experimentally validated. This work comprises a detailed study of the natural variation in the early responses to salt stress, which can give insights into the mechanisms contributing to salinity tolerance and provide the fundaments for crop improvements under saline conditions across the globe.

<p>The synthetic estrogen 17α-ethynylestradiol (EE2), an endocrine disruptor originating from birth control and hormone replacement therapy, is discharged in wastewater treatment plant (WWTP) effluents. The present study employed radio-labeled EE2 to examine the impact of temperature and salinity on the uptake of EE2 in male killifish (<em>Fundulus heteroclitus</em>), a model euryhaline teleost. Fish were exposed to a nominal concentration of 100 ng/L EE2 for 2 h. Actual concentrations were lower due to EE2 adsorption to the exposure system, but uptake rates were normalized to 100 ng/L. Oxygen consumption rates (MO₂), whole body EE2 uptake rates, and tissue-specific EE2 distribution were monitored. EE2 uptake by freshly killed fish was negligible. In killifish acclimated to 18^OC at 16 ppt (50 % seawater), MO₂ and EE2 uptake were both much lower after 24-h exposure to 10^OC and 4^OC, and increased after 24-h exposure to 26^OC. Transfer of killifish to fresh water for 24 h tended to lower EE2 uptake rate, and long-term acclimation to fresh water reduced it by about 70 %. Long-term acclimation to 100 % sea water (32 ppt) also reduced EE2 uptake rate by about 50 % relative to 16 ppt. However this was not seen in juvenile rainbow trout (<em>Oncorhynchus mykiss</em>) where uptake rates were the same in FW- and 16 ppt-acclimated trout. The tissue-specific accumulation of EE2 was found to be the highest (40-60 % of the total) in the liver plus gall bladder across all exposures, and the great majority of this was in the bile in killifish, regardless of temperature or salinity, whereas in trout accumulation was the highest in the carcass at 70 % of the total. The carcass was the next highest accumulator (30-40 %) in killifish, followed by the gut (10-20 %) with only small amounts in gills and spleen. Drinking rate, measured with radio-labeled polyethylene glycol-4000, was about 25-times greater in 16 ppt-acclimated killifish relative to freshwater-acclimated animals. However, drinking accounted for less than 30 % of gut accumulation, and therefore a negligible percentage of whole body EE2 uptake rates. In general, there were strong positive relationships between EE2 uptake rates and MO₂, suggesting similar pathways for uptake across the gills of these lipophilic molecules. These data will be useful in developing a predictive model of how variations in key environmental parameters (salinity, temperature, dissolved oxygen) affect EE2 uptake in estuarine fish, so as to determine optimal timing and location of WWTP discharges.</p> / Master of Science (MS)