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The primary objective of this research was to investigate multicomponent transport of five major cations, Ca2+, Mg2+, NH4+, K+ and Na+, in laboratory soil columns. The soil columns were packed with soils from two different sites and were equilibrated with fresh groundwater from each respective site. Experimental data was obtained by flushing a simulated contaminant through the soil columns. The soil columns were then flushed with fresh groundwater to simulate decommissioning activities. The breakthrough data and soil exchange capacities obtained from both tests were used to identify key processes affecting the transport of the geochemical species. During the simulated contaminant flushing stage, NH4+ and K+ replaced Ca2+ and Mg2+ on the soil exchange sites. Breakthrough of NH4+ was attenuated by factors of 3.2 and 6 for Sites 1 and 2 soils, respectively. Breakthrough of K+ was attenuated by factors of 3.2 and 5.4 for Sites 1 and 2 soils, respectively. Generally, ions with higher valency will exchange for those of lower valency, but in this case the majority of the ions (NH4+ and K+) in the solution has a lower valency and will exchange with those of higher valency by mass action. Ca2+ was the first to be replaced, followed by Mg2+ once the ionic strength of the solution increased. The displacement of calcium and magnesium created a concentration pulse of these cations that coincides with the chloride breakthrough curve. Calcium and magnesium concentrations reached up to approximately 275% and 2000%, respectively, higher than the freshwater originally in the column. During the freshwater flushing stage, freshwater infiltrated the soil columns to assess the permanency of contaminant attenuation and to identify the geochemical mechanisms of contaminant release. Concentrations of NH4+ and K+ declined quickly. Ninety-five percent of attenuated NH4+ was released by the soil. Therefore, the attenuation of NH4+ is reversible but this occurs over several pore volumes at concentrations lower than those in the simulated contaminant and therefore would not result in a mass loading to the environment. Cation exchange was identified as the mechanism responsible for the release of the adsorbed ammonium and potassium into the soil pore water.

The primary objective of this research was to investigate multicomponent transport of five major cations, Ca2+, Mg2+, NH4+, K+ and Na+, in laboratory soil columns. The soil columns were packed with soils from two different sites and were equilibrated with fresh groundwater from each respective site. Experimental data was obtained by flushing a simulated contaminant through the soil columns. The soil columns were then flushed with fresh groundwater to simulate decommissioning activities. The breakthrough data and soil exchange capacities obtained from both tests were used to identify key processes affecting the transport of the geochemical species. During the simulated contaminant flushing stage, NH4+ and K+ replaced Ca2+ and Mg2+ on the soil exchange sites. Breakthrough of NH4+ was attenuated by factors of 3.2 and 6 for Sites 1 and 2 soils, respectively. Breakthrough of K+ was attenuated by factors of 3.2 and 5.4 for Sites 1 and 2 soils, respectively. Generally, ions with higher valency will exchange for those of lower valency, but in this case the majority of the ions (NH4+ and K+) in the solution has a lower valency and will exchange with those of higher valency by mass action. Ca2+ was the first to be replaced, followed by Mg2+ once the ionic strength of the solution increased. The displacement of calcium and magnesium created a concentration pulse of these cations that coincides with the chloride breakthrough curve. Calcium and magnesium concentrations reached up to approximately 275% and 2000%, respectively, higher than the freshwater originally in the column. During the freshwater flushing stage, freshwater infiltrated the soil columns to assess the permanency of contaminant attenuation and to identify the geochemical mechanisms of contaminant release. Concentrations of NH4+ and K+ declined quickly. Ninety-five percent of attenuated NH4+ was released by the soil. Therefore, the attenuation of NH4+ is reversible but this occurs over several pore volumes at concentrations lower than those in the simulated contaminant and therefore would not result in a mass loading to the environment. Cation exchange was identified as the mechanism responsible for the release of the adsorbed ammonium and potassium into the soil pore water.

Accurate modeling of contaminant transport and sorption processes in the soil and landfill liners is a prerequisite for realistic model simulations of contaminant fate and transport in the environment. These studies are also important for the remediation of soil and groundwater contamination. Modeling of contaminant transport through soils and landfill liners consists of either solving the direct/forward problem or the inverse problem. In this thesis, an automated time-stepping implicit procedure is developed from the convergence and error studies of explicit and implicit finite-difference solutions for the advection-dispersion transport of contaminants through soil with different sorption mechanisms. This study is further extended for transient through-diffusion (TTD) transport of contaminant in landfills by considering linear sorption mechanism. To validate the numerical solution and also to study the behavior of finite-difference numerical solutions for TTD transport problem, closed-form analytical solution is derived. Further, a new interface condition is proposed based on the finite-volume procedure for stratified soil or landfill liner system. Solvers are developed for the parameter estimation of inverse problem by integrating the developed procedures for the above forward problem with different optimization procedures. Solvers based on Simulated Annealing (SA) and Genetic Algorithm (GA) are developed for TTD transport in the landfill liners and verified with the existing methods of parameter estimation. Novel swarm intelligence based solver is developed for the first time for parameter estimation in contaminant transport inverse problem to overcome some of the limitations of the classical optimization methods and evolutionary methods such as GA. Additionally, the proposed swarm intelligence based algorithms and a new variant is applied to solve ill-posed problem of contaminant source characterization. The presented work in this dissertation can be unswervingly applied for modeling the contaminant transport in laboratory through-diffusion tests and contaminant transport through landfill liners where the transport is usually considered to be one-dimensional and also diffusion-dominated. Similarly, the advection-dispersion transport through laboratory soil columns can also be modeled with the developed, fast, automated, implicit numerical procedure with very good accuracy. The present study can be applied further for contaminant transport through stratified soil/liner system using fast converging numerical algorithms. Finally, the problems of design parameter estimation and source characterization can be handled accurately by the use of developed automated nature-inspired solvers.

There are many circumstances where lateral flows in the upper soil layers above the regional groundwater table are important for hillslope and catchment hydrology, and in particular for the transport of contaminants. Perched water tables frequently occur in Quaternary drift sequences, reducing rates of recharge to the underlying aquifers and altering contaminant migration pathways; recent experimental and modelling studies have demonstrated the potential importance of lateral flows in the unsaturated zone, even in homogeneous soils; and lateral interflow at the hillslope scale, and its role in generating storm runoff, is the subject of intense current debate amongst hydrologists. A numerical model for simulating transient three-dimensional variably-saturated flow in complex aquifer systems (the Variably-Saturated Subsurface flow, or VSS, model), capable of representing these conditions, is presented in this thesis. The VSS model is based on the extended Richards equation for saturated as well as unsaturated conditions, and also includes capabilities for modelling surface-subsurface interactions, stream-aquifer interactions, prescribed head and flow boundary conditions, plant and well abstractions, and spring discharges. A simple but novel approach is taken to solving the three-dimensional non-linear Richards equation on a flexible-geometry finite-difference mesh, using Newton-Raphson iteration and an adaptive convergence algorithm. The VSS model is implemented as a module of the catchment flow and transport modelling system, SHETRAN. The reliability of the full SHETRAN modelling system is demonstrated using verification and validation tests, including comparisons against analytical solutions for simple cases, and simulations of storm runoff in a small Mediterranean catchment. Simulations of flow and contaminant transport in complex sequences of Quaternary drift deposits demonstrate the full capabilities of the modelling system under real-world conditions.

Cytochrome P4501A (CYP1A), a xenobiotic metabolizing enzyme found in allvertebrates, is highly induced following exposure to a number of organic contaminants.Several populations of teleosts residing in highly contaminated areas have been found toexhibit resistance to the toxic effects of contaminants, a condition characterized byreduced expression of CYP1A.Within this work I demonstrated that expression of CYP1A mRNA, protein, andactivity in caged rainbow trout (Oncorhynchus mykiss) was an effective biomarker ofpolychlorinated biphenyl (PCB) contamination. Furthermore, through the use of bothlaboratory and field studies, I demonstrated that several species inhabiting a PCBcontaminated site exhibited either acquired (Ameiurus natalis) or natural (Lepomiscyanellus) resistance to the CYP1A inducing effects of PCBs. Further studiescharacterized the response of several other Lepomis species to CYP1A inducingcompounds, demonstrating that the natural resistance of L. cynaellus is a characteristicshared by at least two other members of the genus. Lepomis species were relativelyinsensitive to CYP1A induction following PCB exposure yet exhibited highly inducedCYP1A levels following exposure to another CYP1A inducer, the model polyaromatichydrocarbon benzo[a]pyrene (BaP), suggesting a number of species within the genusLepomis may display natural resistance to certain classes of CYP1A inducingcompounds.Additional studies using responsive and resistant populations of killifish wereused to examine the consequences of resistance on fish physiology. Thyroid hormones,known to be altered by PCBs in mammals, were variable but did not differ significantlybetween responsive and resistant fish following PCB exposure. Treatment with PCBssuppressed production of the egg yolk precursor protein vitellogenin in primaryhepatocytes of responsive fish. Studies examining the developmental impacts of toxicantexposure demonstrated altered aspects of development in PCB responsive but notresistant Fundulus heteroclitus embryos exposed to polybrominated diphenyl ethers(PBDEs), compounds structurally related to PCBs. PBDE exposure in juvenile Ictaluruspunctatus failed to induce CYP1A or uridine diphosphate glucuronyltransferase(UDPGT) activity indicating PBDEs do not impact these commonly measuredtoxicological endpoints. The findings of this work describe novel pollutant responses in anumber of species with varying degrees of pollutant sensitivity and contribute to theunderstanding of toxicant induced alterations in teleost physiology.

The Saline Valley Conservancy District (SVCD) formed in 1980 to provide a stable source of water to many communities in Southern Illinois. The SVCD well field located in the thickest, most productive region of the Saline Valley Aquifer lies directly adjacent to a reclaimed coal mine. Subsurface movement and surface discharge from the mine has been shown to be responsible for deterioration of water quality in the surrounding area, including the aquifer. Previous studies conducted in the region have addressed water supply issues and simulated contaminant transport from the reclaimed mine. The limited scope of these models did not extend to natural hydrogeological boundaries. This study extended the model boundaries to natural boundaries including the Saline River to the south, the Wabash and Ohio Rivers to the east, and the bedrock high pinch-out and fining valley textures to the west. The flow model uses parameters from each study as a base then calibrated to 18 discrete head measurements. Initial contaminant transport runs using values from previous studies show successful mine reclamation except for surface discharge to a nearby ditch from well pumping. An analysis was performed that varied parameters to determine if any likely scenarios may cause the plume to travel farther than anticipated. These scenarios include things such as cessation of surface discharge, increasing contaminant source load, and altering recharge and hydraulic conductivity. In all cases sulfate concentrations in the SVCD production wells modeled up to 155mg/L which is under the EPA drinking water guideline for sulfate. Three wells in particular, SVCD-1, SVCD-4, and SVCD-7 never model higher than 7mg/L indicating that several wells lie outside the influence of the sulfate plume. Based on the results of the scenario analysis, the mine can shut off remediation pumping without overly contaminating the SVCD water supply.

The kinetic energy density, k, and lifetime, t, of a turbulent eddy, volume V, are shown to be related to a characteristic length scale, 2, by: 13 =vk= c2/3e2/3 t-C 1/312/3 where c is the energy dissipation rate. A self similar cascade of discrete eddy sizes is derived, each size related to the next larger by: P 22 CC i+l i where C= 81'2. With some simple assumptions as to the turbulent production process the mean logarithmic velocity profile is derived. The relationship between the friction velocity and Reynolds stress is explained in terms of the large eddy intermittency, n. Below a critical free stream velocity, U', n is proportional to the free stream velocity. The dissipation rate, e, is then constant and given by: e U'3/N3L where N is the number of discrete eddy sizes in the boundary layer. When the boundary layer has reached the surface N- 11. The observed turbulent spectral characteristics are derived from the eddy equations without using dimensional reasoning and an explanation of the mechanism behind surface layer similarity scaling is proposed. An experiment was carried out in the North Sea to test the model predictions. Correlations showed that, except at slack water, the largest eddies were approximately cubic, occupying the whole flow depth, and were advected with the mean flow. Frequency spectra provided evidence that the cascade formulation was correct. The turbulent intermittency was proportional to the current speed and the value of c, calculated by several methods, was found to be constant with a value: C=0.3 cm2/s3 The characteristics of the largest eddies were isolated using a spectral cropping technique and plotted as a phase portrait of the turbulent strange attractor. This demonstrated that the boundary layer sat at preferred, discrete energy levels. The levels observed could be related to the discete cascade model. A computer code based on the model equations was tested against a series of large scale oil and dye releases in the North Sea. The observed intermittency, meandering, and dispersion were well simulated with the value of c given above.

In recent years there has been growing environmental concern regarding ‘microplastics’: microscopic plastic granules, fibres and fragments, categorised as <1 or <5 mm diameter. Microplastics are manufactured to be of a microscopic size, or derive from the photo- and mechanical degradation and subsequent fragmentation of larger plastic litter. Microplastics debris has been identified in the water column and sediments of marine and freshwater ecosystems across the globe, although difficulties in sampling and isolating smaller particulates has resulted in the abundance of <333 µm microplastics being under-reported. Microplastics are bioavailable to a range of aquatic organisms, including fish, seabirds and benthic invertebrates, and can be trophically transferred. The consumption of plastic debris can result in gut blockages, heightened immune response and a loss of lipid reserves. The potential risk to food security, and thereby human health, has led regulators to call for better understanding of the fate and effects of microplastic debris on marine life. Here I tested the hypothesis that microplastics can be ingested by and may negatively impact upon zooplankton. Zooplankton encompass a range of aquatic animals that form a key trophic link between primary producers and the rest of the marine food web. I used a suite of feeding experiments, bio-imaging techniques and ecotoxicological studies to explore the interactions and impacts of polystyrene microplastics on marine zooplankton. My results demonstrate that a range of filter-feeding zooplankton taxa, including copepods and bivalve and decapod larvae, have the capacity to ingest microplastics. Microplastics significantly reduced algal feeding in the copepods Centropages typicus and Calanus helgolandicus. With prolonged microplastic exposure C. helgolandicus produced smaller eggs with reduced hatching success, and had reduced survival owing to declining energetic reserves. Microplastics egested by copepods significantly altered the properties and sinking rates of faecal pellets, with potential repercussions for marine nutrient flux. This investigative work highlights that microplastics pose a significant risk to the health of animals at the base of the marine food web.