<p> A detailed study of sponge boring morphotypes within the molluscan fauna of Upper Cretaceous estuarine sediments near Drumheller, Alberta provides information relevant to the depositional environment. Problems with regard to utilizing Entobia as a paleoenvironmental indicator and as an indicator of salinity do not appear to be insurmountable.</p> <p> Distributions and characteristics of associated marine organisms (phoronid worms, gastropods and encrusting bryozoa) suggest that sponge colonies were affected by salinity and sedimentation. Boring networks in Ostrea glabra suggest that more than one species of sponge were present. Sponge distribution patterns, changes in papilla and chamber sizes and preferential occurrence of sponge borings on certain shell thicknesses provide good evidence for responses to salinity and sedimentation.</p> / Thesis / Bachelor of Science (BSc)

Arbuscular mycorrhizal fungi, colonizing over 80% of all plants, were long thought absent in wetlands; however, recent studies have shown many wetland plants harbor arbuscular mycorrhizae (AM) and dark septate endophytes (DSE). Wetland services such as biodiversity, shoreline stabilization, water purification, flood control, etc. have been estimated to have a global value of $14.9 trillion. Recognition of these vital services is accompanied by growing concern for their vulnerability and continued loss, which has resulted in an increased need to understand wetland plant communities and mycorrhizal symbiosis. Factors regulating AM and DSE colonization need to be better understood to predict plant community response and ultimately wetland functioning when confronting natural and human induced stressors. This study focused on the effects of water quality, hydrology, sedimentation, and hurricanes on AM and DSE colonization in three wetland species (Taxodium distichum, Panicum hemitomon, and Typhal domingensis) and plant communities of coastal wetlands in Southeast Louisiana and effects of an antimicrobial biocide, triclosan (TCS), on AM (Glomus intraradices) spore germination, hyphal growth, hyphal branching, and colonization in fresh water wetland plants (Eclipta prostrata, Hibiscus laevis, and Sesbania herbacea) from bottom land hardwood forest in north central Texas. The former, mesocosm studies simulating coastal marsh vegetation ran for five years. In the latter studies, AM spores and wetland plants were exposed to 0 g/L, 0.4 g/L, and 4.0 g/L TCS concentrations in static renewal and flow through exposures for 21 and 30 days, respectively. AM and DSE colonization was significantly affected by individual and interactions of four independent variables in mesocosm experiments. Similarly, spore germination, hyphal growth, hyphal branching, and AM colonization in selected wetland plants were significantly lowered by exposure to the TCS at environmentally relevant concentrations. However, levels of effects were plant species and fungal propagules specific. My results showed that natural and human induced alterations in environmental factors and chemical contaminants can significantly impact levels of mycorrhizal spore germination, colonization, and spore density in coastal and freshwater wetland plants. The resulting impacts on plant community structure and ecosystem function require further study.

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No / Computational Fluid Dynamics (CFD) represents a useful tool to study natural currents in the rivers and estuaries with erosive materials; therefore, it is always in the keen interest for scientists to further study and advance it, especially when numerical model has the advantages compared to actual laboratory experiment in terms of cost, time, and restrictions on conditions of the physical models and field collections. The present study deals with the hydro-morphological investigation and numerical modeling of a group of vertically stationed parallel groynes using FLOW-3D commercial software. To validate the results of the FLOW-3D simulation, it has been compared to the experiments from literature. Besides, a SSIIM 2.0 software has also been employed to compare with some of the FLOW-3D results. It was found that the accuracy of the FLOW-3D model influenced by the approach Froude number and the critical velocity ratio (Uavg/Ucr). Even though it underestimated the measured scour depth (due to complex and intense vortices, which reduce the accuracy of the numerical models), but general results from the model have reproduced the measured data well.

Lakes and reservoirs exhibit a number of mixing and transport mechanisms. Understanding the transport is crucial to understanding and predicting constituent and density structures. Transport in waterbodies can be natural, such as seiche-induced boundary mixing or advectively-driven inflows. Hypolimnetic oxygenation using bubble-plumes also leads to enhanced mixing. Whether natural or plume-induced, increased mixing will alter the waterbody properties. Conversely, the density structure affects the behavior of plumes as well as inflowing and outflowing water. For example, stratification resulting from impounding a river can result in nutrient and suspended solids retention. Similarly, operation of plumes can induce mixing in the hypolimnion, resulting in warming, increased nutrient transport, and resuspension of settled particles. Modeling is extremely useful in determining the effects of dams on water quality constituents, enhanced transport, and the performance of mitigation techniques, such as hypolimnetic oxygenation. In this work, a variety of modeling techniques are used to evaluate natural and man-made mixing mechanisms. These include simple temperature and mass budgets, a two-dimensional lake model, and a two-phase plume model. A bubble-plume and plume-enhanced mixing was studied in Lake Hallwil. It was found that the plume-lake interaction was much more complex then previously expected, and knowledge of the seiche- and plume-enhanced near-field was necessary to accurately model the plume performance. A two-dimensional lake model was then coupled with a linear-plume model to accurately predict not only the plume performance, but also the plume-enhanced mixing in Spring Hollow Reservoir. The same two-dimensional lake model, used in conjunction with data analysis, demonstrated that the Iron Gate I Reservoir was not a significant sink for suspended solids, with only the large, adjacent side bay (Orsova Bay) thought to be the permanent sink. Furthermore, significant stratification did not develop, preventing substantial primary productivity. While the impoundment did change the water quality characteristics, the extent is much less than previously expected. The modeling methods presented here and the coupled plume-reservoir model should be useful tools for the design, modeling and greater understanding of bubble-plumes and other transport-related phenomena in lakes and reservoirs. / Ph. D.

Synthetic nanomagnetite has been suggested as a potential reactant for the in-situ treatment of contaminated groundwater. Although the application of nanomagnetite for environmental remediation is promising, a full understanding of its reactivity has been deterred by the propensity of the nanoparticles to aggregate and form clusters. To characterize the factors responsible for this aggregation behavior, we determined the magnetic properties of magnetite using a superconducting quantum interference device (SQuID). Importantly, because magnetite readily reacts with O2 to produce maghemite, we analyzed the effect of oxidation on its magnetic properties. We observed that oxidation caused a decrease in the saturation magnetization and the anisotrophic barrier of magnetite resulting in less significant magnetic interactions between particles. Consequently, a decrease in the aggregation of magnetite clusters and a potential increase in stability are expected after oxidation. To support these findings, an extended series of experiments to measure the aggregation and the sedimentation of clusters of unoxidized and oxidized magnetite nanoparticles were conducted. Although the individual particle diameter remained constant after oxidation, the cluster size and the aggregation and sedimentation kinetics of magnetite were determined to be different. Oxidized samples of magnetite tended to have lower aggregation rates and were more resistant to sedimentation. These findings can be used to have a better understanding of the overall fate, transport, and reactivity of nanomagnetite, and to gain new insights on its role as a remediation agent in the subsurface environment. / Ph. D.

While release of contaminants during dredged material disposal operations has long been the subject of environmental concern, the potential release of pollutants during the dredging process has recently come under the scrunity of federal and state regulatory agencies. The mechanical action of a dredging operations causes resuspension of sediment particles and release of soluble contaminants to the water column. A predredging test is essential to estimate the amount of soluble release at or near the point of dredging to ascertain potential water quality impact. The Standard Elutriate Test has proven to be a good estimator of soluble contaminant release for dredged material disposal operations and researchers have recognized that the processes involved at the point of dredging are similar to those involved with the open-water disposal of dredged material. This research is an evaluation of the Standard Elutriate Test as an estimator of soluble contaminant release at the point of dredging. Data and field studies were conducted by the U.S. Army Corps of Engineers Waterways Experiment Station at five sites around the United States. A direct comparison was made between elutriate test data from predredging bottom sediment and water sample analysis taken at or near the point of dredging. The Standard Elutriate Test satisfactorily predicted the release of soluble contaminants at or near the point of dredging in four out of the five sites in this study. The fifth site had extenuating circumstances that may account for the failure at this site. In this investigation, the elutriate test appears to overestimate the release of organics, nutrients and some heavy metals (Hg, Mn, Fe, and Cr). Statistical analysis provided a predictive equation that can be used to estimate the upper-bound value a constituent concentration will approach based on elutiate test data and a specified confidence level. / M.S.

Sediment and microplastic accumulation in stream systems occur when particulates entrained in overbank flow are retained by the floodplain. Despite overbank flow conditions dictating sediment and microplastic accumulation, the spatial distribution of accumulation within floodplains remains poorly understood. Difficulty quantifying hydraulic flow conditions is due to spatial variation introducing erroneous error. This study hypothesized floodplain sediment and microplastic accumulation would be closely correlated with topographic, vegetative, and hydraulic conditions. To test this hypothesis, sediment and microplastic accumulation were measured along a 1.25 km stretch of Stroubles Creek in Blacksburg, Virginia. Sediment accumulation was measured using tiles with a surface area of 144cm² at 75 locations. Tiles accumulated 4,782g over their two-year deployment. Microplastic accumulation was assessed by taking 15cm3 soil grab samples from 40 locations. Microplastics were identified using FTIR spectroscopy and were found to have a concentration of approximately 7MPm-3. Topographic and vegetative variables were measured using digital elevation and canopy height models, while hydraulic variables were calculated with an unsteady flow model in HEC-RAS. Sediment and microplastic accumulation were both found to be significantly influenced by terrain and hydraulic conditions. Sediment accumulation yielded an MLR model with an R2 of 0.72, with a confidence level between 97% - 99%, while the microplastic model yielded an R2 of 0.26 and with a confidence level between 95% - 98%. Differences in sediment and microplastics particle density resulted in hydraulic conditions being more influential on microplastic accumulation with an R2 81.5% greater than any its terrain components. This research identified floodplain accumulation process drivers which could help to guide future management decisions regarding sediment storage and monitoring microplastic accumulation. / Master of Science / Streams act as natural thoroughfares, with the potential to transport materials beneficial and harmful to biological and environmental processes. During flood events, the material carried by stream flow is often deposited in areas adjacent to the main channel. These adjacent areas are called floodplains and contribute to the accumulation of sediment and small pieces of plastic in stream systems. Spatial patterns in floodplain accumulation are believed to be the result of site-specific terrain, vegetation, and flow conditions within a stream system. In the context of a stream system, descriptive characteristics of terrain, vegetation, and flow conditions are heavily confounded making their relationship with floodplain accumulation difficult to interoperate. This study aims to understand the accumulation of sediment and plastics in the Stroubles Creek floodplain by evaluating the terrain, vegetative, and flow conditions believed to influence systematic patterns in accumulation. Floodplain sediment and plastic accumulation were measured along a 2 km reach of Stroubles Creek at 75 and 40 sampling locations. Terrain, vegetative, and flow conditions at each of the sediment (75) and plastic (40) sampling locations were determined to be the characteristics driving their relative accumulation process. The distance and change in elevation of the sampling locations from the channel, flow velocity of water, arrival time and duration of time each location experienced floodwaters were observed to have the most significant impact on accumulation processes. However, the degree to which each of these variables affected sediment and plastic accumulation differed. These findings suggest that sediment and plastic accumulation are both heavily influenced by terrain and flow conditions; however, the processes by which sediment and microplastics accumulate in the floodplain are likely to differ.