Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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2016 - 20182

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    Effects of Salinization on Base Cation, Nutrient, Carbon, and Trace Metal Biogeochemistry in Human-Impacted Rivers in the Eastern US
    (2018) Haq, Shahan; Kaushal, Sujay S; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Urbanized watersheds in colder climates experience episodic salinization due to anthropogenic salt inputs and runoff from impervious surfaces. We conducted laboratory experiments and analyzed high-frequency sensor data to investigate the water quality impacts of freshwater episodic salinization across 12 watersheds draining two major metropolitan regions along the U.S. East Coast. Sediments from watersheds spanning land use gradients were incubated across a range of replicated salinity treatments (0–10 g/L sodium chloride). Our results suggested that episodic salinization can mobilize base cations, nutrients, and trace metals to streams through accelerated ion exchange and biogeochemical processes induced by shifting pH ranges and ionic strength. The response of dissolved carbon concentrations to experimental salinization varied between sites, and dissolved silica did not show any significant response. The growing impacts of freshwater salinization syndrome on nutrient mobilization, shifting acid–base status, and augmenting eutrophication warrant serious consideration in water quality management.
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    GEOTECHNICAL AND ENVIRONMENTAL IMPACTS OF STEEL SLAG IN EMBANKMENTS
    (2016) Yalcin Dayioglu, Asli YALCIN DAYIOGLU; AYDILEK, Ahmet H; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Steel slag is a byproduct of iron and steel production by the metallurgical industries. Annually, 21 million tons of steel slag is produced in the United States. Most of the slag is landfilled, which represents a significant economic loss and a waste of valuable land space. Steel slag has great potential for the construction of highway embankments; however, its use has been limited due to its high swelling potential and alkalinity. The swelling potential of steel slags may lead to deterioration of the structural stability of highways, and high alkalinity poses an environmental challenge as it affects the leaching behavior of trace metals. This study seeks a methodology that promotes the use of steel slag in highway embankments by minimizing these two main disadvantages. Accelerated swelling tests were conducted to evaluate the swelling behavior of pure steel slag and water treatment residual (WTR) treated steel slag, where WTR is an alum-rich by-product of drinking water treatment plants. Sequential batch tests and column leach tests, as well as two different numerical analyses, UMDSurf and WiscLEACH, were carried out to check the environmental suitability of the methods. Tests were conducted to study the effect of a common borrow fill material that encapsulated the slag in the embankment and the effects of two subgrade soils on the chemical properties of slag leachate. The results indicated that an increase in WTR content in the steel slag-WTR mixtures yields a decrease in pH and most of the leached metal concentrations, except aluminum. The change in the levels of pH, after passing through encapsulation and subgrade, depends on the natural pHs of materials.