Cement is one of the worlds most widely used building materials and as such great lengths have been taken over the years to further improve the mechanical properties and durability of cementitious materials in order to increase reliability and decrease maintenance costs. The mechanical properties of carbon microfibers (CF) have made them attractive candidates for the reinforcement of several matrices including cement. Technological advancements have led to the development of carbon nanofibers (CNF) with even more advantageous mechanical properties due to their smaller size and therefore show tremendous promise as reinforcement in cementitious materials. This research studied the effects of carbon fiber type (CF vs. CNF) and CNF loading on Portland cement pastes and silica fume Portland cement pastes. CNF loading up to 0.5 wt% had no significant effect on the compressive and tensile strength of the pastes. In contrast, 2 wt% CNF loading was found to decrease the compressive strength of the Portland cement paste. Addition of 2 wt% CNF enhanced the water penetration resistance of the cement pastes and improved the durability with respect to decalcification and leaching.

This work consists of constructing a model that combines an understanding of physical transport processes and the biological mechanisms involved in the uptake, transport and sequestration of contaminants by a hyperaccumulator, alpine pennycress (Thlaspi caerulesciens), a non-accumulator, field pennycress (Thlaspi arvense), and a maize. Specifically, the model uses a Michaelis-Menten formulation to describe uptake, and transpiration-driven translocation into aboveground biomass. Model simulations indicate that, despite its small biomass and slow growth, the hyperaccumulator alpine pennycress is a reasonable choice for phytoextraction due to the fast uptake rate as well as high metal tolerance, specifically in the aboveground biomass. In contrast, the field pennycress, which has a similar small biomass, but can only tolerate cadmium at much lower levels and does not translocate cadmium into aboveground biomass, is not an ideal candidate for phytoextraction. Although maize has a much larger biomass, phytoextraction using maize requires chemical treatment that mobilizes cadmium into the surrounding environment, and it has negative features similar to those of the field pennycress. Further studies that account for diurnal and seasonal variations in moisture and radiation may be required; however, the relative performance between those three species is not expected to change.

This research involved the development of a new information system to improve inland waterway spill response. A review of current decision-support tools used to aid in spill response suggested that improvements were needed. Based on an evaluation of demands faced by both water quality management and spill response personnel, an enhanced system design was developed and implemented, one that utilizes advanced modeling capabilities and provides information in a visual manner. The resulting product, Spill Management Information System, version 2.0 (SMIS 2.0), combines state-of-the-art hydrodynamic and spill impact models with a geographic information system (GIS) interface to create a user-friendly tool to assist in predicting spill propagation and the location of spill response resources. The system is successfully demonstrated in a case study application in which several spill scenarios are simulated on the Kentucky Lake portion of the Tennessee River.

Beneficial use involves the application of a secondary material from an industrial process, which otherwise may be considered a potentially hazardous waste, as a building block in another process. The application is considered to be beneficial in that the quantity of waste material remaining to be managed is minimized by its use. There are significant barriers to beneficial use projects; primarily, the environmental evaluation that determines whether the secondary material will be harmful to human health and the environment. The environmental evaluation is most challenging because there is no universally excepted methodology for evaluating secondary materials. The currently accepted testing methodologies (e.g., single batch tests such as the Toxicity Characteristic Leaching Procedure or TCLP) do not provide the level of mechanistic environmental assessment information required to adequately support the beneficial use determination process. The intent of this work is to address the issues surrounding beneficial use determinations and to move the field of beneficial use forward through enhanced communication by providing a uniform assessment approach. This thesis presents the use three laboratory leaching tests, under consideration for adoption by the United States Environmental Protection Agency as characterization procedures, as a basis for environmental evaluation of secondary materials for beneficial use. The leaching tests were performed on two mixtures of red mud and phosphogypsum. An initial screening of leaching data is made by comparing test results to documented water quality criteria. Since the leaching test results do not take into account dilution/attenuation factors (DAFs) that are built into water criteria, the screening assessment consisted of calculating the DAF that must be supplied by the release scenario in order to be protective of the environment. Examination of calculated DAFs show that constituent leaching from these two secondary materials would likely not exceed water quality limits under credible environmental scenarios. Although additional work is needed prior to acceptable application of red mud and phosphogypsum as alternative construction materials, the assessment approach of this study provides an indication that advanced leaching tests can facilitate evaluation of potential environmental impacts in a beneficial use scenario.

This thesis is the result of an investigation of the effectiveness of incorporating risk education into the curriculum of early adolescents, notably students enrolled in fifth grade. As these students explore different aspects of environmental and human health risks that affect their everyday lives, it is important that they learn how to access objective information and utilize it in acting more responsibly. Studies have shown that people are unlikely to engage in healthy behaviors if they perceive the associated risk to be unsafe. Rather than have fear be the motivator of risk perception, if the appropriate education is provided to these students, knowledge will instead guide risk perception. This will allow the student to make more rational decisions involving risky behaviors. The study began by reviewing existing risk-related curriculums, so as to identify those educational techniques that have proven to be successful, as well as to determine where educational material was lacking in its treatment of risk-related subject matter. A modified risk education curriculum was subsequently developed, building on the best practices observed in reviewing previous initiatives. This risk education module was subsequently offered to five fifth grade classes affiliated with two different public school systems in northern Alabama. The effectiveness of the risk education module was evaluated by administering a risk exam to the students. One-half of the students in each class was randomly chosen and given this exam prior to the introduction of the risk education module (control group). The remaining students were given the same exam after receiving the risk education module. Based on the exam results, it was found that the group receiving the risk education module scored at statistically significantly higher levels than the control group, an improvement of more than 20%. Based on these results, it can be concluded that introducing risk education curriculum to early adolescents can be an effective means to providing students with an improved knowledge base and thought process upon which to exhibit more responsible risk behavior.

Elevated groundwater arsenic in Southeast Asia is a problem, as it is not unusual for wells spaced several meters apart from one another and drilled to the same depth to have dramatically different concentrations of arsenic (i.e., 7-321 ìg/L). This is a compendium of sedimentological, geochemical, and geochronological methods, investigating why Asian aquifers evolve such heterogeneous arsenic distributions. Making use of preliminary arsenic data from sites in Van Phuc, Vietnam; Parasi, Nepal; and Araihazar, Bangladesh, ~1km high-resolution needle- and OSL- sampling transects were conducted between known areas of high and low groundwater arsenic. Results show that arsenic varies predictably with aquifer deposits of differing sources and ages, with groundwater arsenic decreasing in all locations as the age of the aquifer increases. This is important because the results show the degree to which aquifer deposits vary and define the local (i.e., sediment facies and fluvial history) and regional (i.e., sediment source and fluvial history) geomorphic processes that govern arsenic distributions in the region, such as the rates in which these aquifers ingrow and then, possibly, attenuate arsenic.

In arid environments, spatiotemporal variations in the processes of erosion and deposition are strongly coupled with the structure and dynamics of plant communities as well as the specific life behavior of individual plants. Understanding how physical transport processes affect the evolution of the land surface on geomorphic time-scales therefore requires considering how long-term changes in plant dynamics may in turn impact such processes. The development of this desert shrub population dynamics model is therefore motivated by the need to link rain-splash induced mound building at the shrub-scale with the unfolding biological play occurring on a hillslope. Using the Master Equation to conserve shrub age, probabilistic and biologically informed statements for recruitment and mortality are formulated to function as source and sink terms respectively. This simple accounting framework, by tracking the number of individuals entering and leaving a population, captures the changes in shrub count that can be expected in time as the key variables driving the dynamics of these plant communities (i.e. precipitation) also change in time. The result is a tool through which it is possible to statistically describe the aggregate spatiotemporal behavior of different shrub populations, with their own characteristic life-cycles and physical dimensions, under different external forcing scenarios. This model features inputs that have a solid biophysical basis and insofar as it has the capacity to mimic key features of real processes, leads to outputs which appear consistent with findings reported in the literature.

The processes by which magma is transported into, stored within, and expelled (erupted) from the upper crust are critical to understanding volcanism and crustal construction. Recent studies suggest that magmatic systems may be generally long-lived and highly variable in composition, temperature and melt fraction (hence rheology) in both space and time. Petrologic studies of young volcanoes, however, generally suggest short timescales between magma production and eruption. System longevity and spatial and temporal fluctuations are in part a consequence of repeated recharge and can be either cause or consequence of eruption. Understanding how individual systems operate, or drawing general conclusions about and predicting magmatic behavior, hinges on monitoring and comparing the time-temperature-composition histories of both intruded and erupted products. The mineral zircon provides unique opportunities for such monitoring by combining high precision in situ radiometric dating with new methods of analysis and interpretation of elemental zoning. We have tested and applied this new combined methodology (U-Pb and U-Th disequilibria dating and elemental analysis, including Ti-in-zircon thermometry) at the Spirit Mountain Batholith, Nevada and Mount St. Helens volcano, Washington. The Spirit Mountain batholith is a well-characterized intrusive system which we use to better understand the trace element record of zircon in magmas. Zircon from Mount St. Helens provides critical insights into the volcanos long term history and magmatic plumbing system, aspects of the otherwise well-characterized volcano that remained poorly understood. Current data and models for Mount St. Helens suggest relatively rapid transport from magma genesis to eruption, with no evidence for protracted storage or recycling of magmas. However, we show here that complex zircon age populations extending back hundreds of thousands of years from eruption age indicate that magmas regularly stall in the crust, cool and crystallize beneath the volcano, and are then rejuvenated and incorporated by hotter, young magmas on their way to the surface. Estimated dissolution times suggest that entrained zircon generally resided in rejuvenating magmas for no more than about a century. Zircon elemental compositions reflect the increasing influence of mafic input into the system through time, recording growth from hotter, less evolved magmas tens of thousands of years prior to appearance of mafic magmas at the surface or changes in whole rock geochemistry and petrology and providing a new, time-correlated record of this evolution independent of the eruption history. Zircon data thus reveal the history of the hidden, long-lived intrusive portion of the Mount St. Helens system, where melt and crystals are stored for up to hundreds of thousands of years and interact with fresh influxes of magmas that traverse the intrusive reservoir before erupting.

Water quality modeling is being used increasingly by decision-making agencies, such as the United States Army Corps of Engineers (USACE), as a tool to predict the behavior of changing water systems. This study documents an effort to develop and calibrate a CE-QUAL-W2 version 3.6 model for the Cheatham Reservoir portion of the Cumberland River, near Nashville, TN. The model was calibrated to data from the year 2009. Model setup, calibration, and results are explained in detail to include a section on a mathematical technique for estimating daily water temperature from local daily air temperature. The study concludes with an example use of the calibrated model that analyzes the use of a fixed-cone valve, installed in the J. Percy Priest Reservoir to improve dissolved oxygen levels from reservoir releases.

A common approach used to isolate contaminants in the environment and mitigate associated human and ecological risks is to apply engineered covers over landfills used for disposal of radioactive, hazardous chemical and municipal solid waste. The degradation of engineered covers over time is a complex process that is influenced by site specific characteristics, the structure and dynamics of the indigenous plant community, and the interplay of physical and biological factors at contaminated sites. This research includes a review of long term monitoring and performance assessment of engineered covers, an evaluation of key ecological principles in the context of cover performance, the identification of important ecological processes for performance confirmation, and a case study in the use of event tree analysis (ETA) to evaluate risks to performance of ET and conventional covers. Ultimately, the goal of this research is to develop a performance-assessment approach for selection, design, modeling, and monitoring ecological components of covers.