The impact of aging in the presence of reactive gases (i.e., carbon dioxide and oxygen) on the physical and chemical microstructure of microconcretes and cast stone cementitious waste forms prepared with different fly ash types was investigated. Geochemical speciation with reactive transport modeling was also performed for the microconcretes to better understand and predict the leaching behavior of cementitious materials after aging. The alkalinity of microconcrete materials due to the fly ash replacement type was found to impact the rate and extent of carbonation and the relative changes in the pore structure within the bulk and interfacial transition zone regions. Migration and deposition of constituents was observed within the microstructure of microconcrete materials in response to changes in constituent solubility due to carbonation. A common mineral and solid solutions reaction set can be used in the geochemical speciation with reactive transport modeling to describe the leaching behavior of non-carbonated and carbonated microconcretes with different fly ash replacement types, with some identified limitations. A multi-ionic diffusion approach and consideration of the minerals controlling solubility at a low liquid-to-solid ratio was required. For cast stone cementitious waste forms, the changes in the mineralogy and the microstructure that occur as a result of carbonation are different from what has been observed for cementitious materials with larger amounts of Portland cement. Oxidation and carbonation were also found to influence the mass transport of constituents due to changes in constituent solubility, material pH, and porosity.

Cesium (137Cs) and technetium (99Tc) are two radionuclides of significant concern in spent nuclear fuel because of their long half-life, high decay energy, and high solubility. Cementitious materials are considered as potential candidates for nuclear waste immobilization. The study of the interaction of radionuclides with the cement matrix is thus essential to determine the capability of cementitious materials to immobilize radioactive isotopes such as 137Cs and 99Tc. Calcium-silicate-hydrate (C-S-H) and calcium-aluminate-sulfate hydrate (ettringite) are two main products of cement hydration in Portland Cement (PC). The interactions of CsCl solution with different crystalline C-S-H structures (9Ã tobermorite, 14Ã tobermorite and jennite) and the interactions of KTcO4 solution with crystalline C-S-H structures (14Ã tobermorite and jennite) and ettringite were studied using Molecular Dynamics (MD) simulations. MD simulation results indicated that Cs+ ions were mainly adsorbed as inner-sphere complexes at the tetrahedral SiO4 surface ((0 0 1) plane) of 9Ã tobermorite, 14Ã tobermorite, and jennite. The tobermorites showed higher adsorption capacity of Cs+ ions than jennite. Jennite had weak affinity to Cs+ ions. MD simulation results indicated that TcO4- ions can be adsorbed on the surfaces of 14Ã tobermorite and ettringite. On the octahedral CaO6 surface ((0 0 -1) plane) of 14Ã tobermorite, inner-sphere Tc complexes coexisted with outer-sphere Tc complexes. Co-ion adsorption affected the adsorption of outer-sphere Tc complexes and pushed outer-sphere complexes further away from the surface. On the octahedral CaO6 surface ((0 0 -1) plane) of ettringite, TcO4- ions were mainly adsorbed as outer-sphere complexes. Two types (i.e. type 1: tetragonal geometry and type 2: tetrahedral geometry) of outer-sphere Tc complexes were predicted on both surfaces of 14Ã tobermorite and ettringite. Jennite had no affinity to TcO4- ions. In conclusion, 9Ã tobermorite and 14Ã tobermorite were better candidates for the immobilization of Cs+ ions than jennite. Ettringite and 14Ã tobermorite also showed better affinity to TcO4- ions than jennite. Ca2+ ions on the surface played an important role and formed complexes with TcO4- ions.

Water is an important resource for various societal needs, with agriculture accounting for 70% of global freshwater withdrawals and 90% of global water consumption. Due to increasing constraints from climate change (among other factors), improved and efficient management of current resources will be critical to continued growth. Given that agriculture production is embedded in a coupled natural and human system, sustainable management analysis of water-related decision making requires incorporation of economic and psychological factors in addition to natural resource factors. Using Sri Lanka as a case study, this dissertation research combines physical insights with social knowledge about crop cultivation to inform assessments of climate change adaptations. Specifically, we characterized spatiotemporal patterns of agricultural drought in the country over the last 130 years, identified the value of shifting the planting date for rice (the staple food of the country), and evaluated the use of seasonal weather forecasts to guide farmer crop selections. Our analysis highlights that while policies and programs that promote production of certain crops may ensure food security in the short-term, the long-term implications of these dynamics need careful evaluation.

Advances in technologies associated with hydraulic fracturing and horizontal drilling in the first decade of this century have enabled a massive energy transformation in the United States. For the first time, carbon emissions in the U.S. have decreased steadily while economic growth has increased, largely because of the switch from coal to natural gas made possible by hydraulic fracturing and horizontal drilling. Also because of hydraulic fracturing, the U.S. is now the worldâs largest producer of oil and natural gas. The rapidity with which the nation experienced these changes saw communities grappling with oil and gas operations on a scale many had never experienced, bringing lucrative economic opportunities as well as challenges, especially to local and rural transportation infrastructure. Tools and methodologies are needed to assist communities, and newly emerging tools need data-driven analyses of their utility. This work represents the first comprehensive national survey of state regulators on the effectiveness of FracFocus, a tool developed by regulators to address chemical disclosure in hydraulic fracturing operations. The study provided needed visibility to the (often novel) ways states were using FracFocus to augment state regulatory programs with important potential for sharing valuable approaches between states. Important data and information emerging from the FracFocus study was then leveraged to develop a methodological approach for local planners addressing impacts from oil and gas development. With a focus on local transportation infrastructure, the methods developed were applied in a case study to the Tuscaloosa Marine Shale Oil Play in Mississippi, and included the views of local operators, a perspective largely missing from the literature. Finally, this work provides a legal and policy framework for local planners to better understand potential approaches and challenges to maintaining transportation infrastructure in the face of large scale hydraulic fracturing. Local communities have met with significant obstacles when attempting to regulate oil and gas development from an environmental or policy perspective, but local regulations tailored to address infrastructure impacts are more likely to be successful.

The oxidation kinetics and mechanisms of commercial dyes by H202 and iron powder system were investigated in a well-mixed batch reactor. The three dyes studied are Reactive Red 120, Direct Blue 160 and Acid Blue 40. There are three major processes involved in the oxidation: iron powder dissolution to Fe2+, dye adsorption by iron powder and dye oxidation by Fenton's reagent. Dissolution of iron powder was the initial step of adsorption and oxidation of the dyes. Dye adsorption obeyed the Langmuir adsorption isotherm. Both dissolution and adsorption were favorable at pH 2.0 to 2.5. Oxidation by Fenton's reagent was the major process contributed to decolorization. The optimal pH ranged from 3.0 to 3.5. The optimal ratio of H202 to iron metal was 0.001 M to 1.0 g/L. The initial oxidation rate followed pseudo-first-order kinetics. The mechanisms of iron dissolution, dye adsorption and oxidation were proposed in order to explain the experimental phenomena.

A water quality model was developed to analyze the impact of hydrological events on mercury contamination of the Upper East Fork Poplar Creek, Tennessee. The model simulates surface and subsurface hydrology and transport (MIKE SHE and MIKE 11) and it is coupled with the reactive transport of sediments and mercury (ECOLAB). The model was used to simulate the distribution of mercury contamination in the water and sediments as a function of daily hydrological events. Results from the model show a high correlation between suspended solids and mercury in the water due to the affinity of mercury with suspended organics. The governing parameters for the distribution of total suspended solids and mercury contamination were the critical velocity of the stream for particle resuspension, the rates of resuspension and production of particles, settling velocity, soil-water partition coefficient, and desorption rate of mercury in the water. Flow and load duration curves at the watershed exit were used to calibrate the model and to determine the impact of hydrological events on the total maximum daily load at Station 17. The results confirmed the strong link between hydrology and mercury transport.

The focus of this research is to determine if a relationship exists between the stability constant and the initial uptake rate of a mercury species by bacteria. Cultures of the sulfate-reducing bacteria (SRB) strain Desulfovibrio desulfuricans G20 were washed with a bicarbonate buffer solution containing either lactate and sulfate or pyruvate and fumarate. The washed cell solutions were then spiked with either mercury bound to natural organic matter (Hg-NOM) or neutral mercury chloride (HgCl2), followed by sampling over time to provide kinetic data. Despite the significantly different stability constants for Hg-NOM and HgCl2, the calculated initial rate constants for mercury uptake for these two types of complexes appeared to be comparable. Uptake of mercury sulfide species was inconclusive due to possible formation of cinnabar. A simple model that is based on assumptions of passive diffusion and facilitated uptake of mercury by bacteria was evaluated for its potential to simulate the uptake. The model results only agreed with experimental data for HgCl2 uptake.

It is well established that trihalomethanes, in drinking water are byproducts of chlorine disinfection. A method to predict the distribution and concentration of trihalornethanes is important because of health risks associated with chronic exposure to these compounds. A literature review has provided information on the chemistry of water chlorination and a data base developed in the laboratory has provided data on trihalomethane formation under various conditions. These data were used to generate rate constants for the formation of trihalomethanes. Trihalornethane formation kinetics appeared to be influenced primarily by the presence of ammonia. The influence of pH is not as profound as indicated in literature. The rate of formation is low at and before breakpoint, whereas it increases after breakpoint.

This project investigated the accuracy of laboratory results of urine samples collected from cotton balls as compared with samples collected from catheterization, preemie pampers and newborn pampers. Also, it examined the cotton ball's effect on the infant's skin upon its removal. Comparisons in test results were made concerning the Directigen test for Group B strep (GBS) and labstick analysis, using descriptive and inferential statistical analysis. The infants (21) who were tested for GBS using catheter and cotton ball samples yielded the same results. Urine samples subjected to labstick analysis were obtained from 30 infants, the urine being extracted from preemie pampers, newborn pampers, and cotton balls placed in preemie pampers. Samples obtained from cotton balls and preemie pampers yielded equivalent results. However, significant differences were found in pH and specific gravity between newborn pamper samples and samples obtained from cotton balls or preemie pampers. No redness or skin breakdown was observed.

The impact of ultrasound on improving the performance of a granular iron Permeable Reactive Barrier (PRB) in the degradation of Trichloroethylene (TCE) was evaluated. Two treatment columns made of clear Plexiglas with a height of 1ft and a diameter of 2 inches and filled with granular iron were used. One was fitted with 25Khz ultrasound probes. A solution of TCE was run through at constant flow rate. Samples obtained from the column at different residence times before and after sonication were analyzed for concentrations of TCE and used to generate concentration profiles to obtain rate constants, which were compared. An improvement of 23.4% in the reaction rate of TCE degradation was observed after sonication of the iron media suggesting that ultrasound may contribute to improving the performance of PRBs in the degradation of TCE in contaminated groundwater.