Thesis (Ph. D.)--Indiana University, School of Public and Environmental Affairs, 2006. / Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0156. Adviser: Ronald A. Hites. "Title from dissertation home page (viewed Feb. 22, 2007)."

Bridges constitute key elements of the nation's infrastructure and are subjected to considerable threats from natural hazards including seismic events. A range of potential bridge retrofit measures may be used to limit seismic damage in deficient bridges, and help mitigate associated social and economic losses. However, since resources are often limited for investment in seismic upgrade, particularly in regions of intense but infrequent events, a risk-based approach for evaluating and comparing the cost effectiveness of different mitigation strategies is warranted. This thesis illustrates a method for evaluating the best retrofits for non-seismically designed bridges based on seismic life-cycle costs and cost-benefit analysis. The approach integrates probabilistic seismic hazard models, fragility of as-built and retrofitted bridges for a range of damage states, and associated costs of damage and retrofit. The emphasis on life-time performance and benefits, as opposed to initial retrofit cost alone, not only permits risk-wise investment, but also helps to align upgrade actions with highway agency missions for sustainable infrastructure.

Thesis (Ph.D.)--Lehigh University, 2009. / Advisers: Edward K. Levy; Harun Bilirgen.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3629. Advisers: Xinlei Wang; Yuanhui Zhang. Includes bibliographical references (leaves 86-98) Available on microfilm from Pro Quest Information and Learning.

Many current models that describe biodegradation and transport of contaminants in porous media do not include provisions for nonideal (nonlinear, rate-limited) sorption, microbial lag, inhibition, microbial community heterogeneity, and cell transport. Therefore, a more complete model was developed that incorporates bacterial lag, inhibition effects, and cell transport/elution, as well as nonlinear, rate-limited sorption. The performance of the new model was evaluated by using the model to simulate the results of a series of miscible-displacement experiments conducted using a range of porewater velocities, substrate concentrations, and initial cell densities. The results show that the model can simulate the substrate breakthrough curves very well. The model was also able to predict the total biomass growth. The calibrated values obtained for the maximum specific growth-rate coefficient, the mean lag time, and lag-time variance were within the range of values obtained from batch experiments. These results suggest that the model performed well and that it successfully describes the system. The model was used to investigate the coupled interactions among sorption, biodegradation, and transport, and the results show that biodegradation can significantly influence the first, second, and third spatial moment when sorption is nonlinear or rate-limited depending on initial/boundary conditions, residence time, biomass growth dynamics, and time-dependent sorption/desorption processes. The influence of heterogeneous microbial communities on biodegradation and transport of contaminants was investigated in the last part of the study. A one-dimensional mathematical model was developed that incorporates multiple populations, each subject to its own set of growth-related coefficients. Breakthrough curves produced for different combinations of growth rates, half-saturation constants and initial biomass concentrations for multiple species exhibit oscillatory behavior under certain conditions, which is attributed to competition between different species. The results suggest that the existence of heterogeneous microbial communities can have a significant influence on biodegradation and transport. The results presented herein illustrate the significant impact that factors such as microbial lag, microbial community heterogeneity, and nonideal sorption/desorption can have on the transport of biodegradable contaminants in porous media. One product of this dissertation is the development and evaluation of a more comprehensive model that represents many important processes involved in transport of biodegradable contaminants. The use of this type of model should enhance our ability to investigate and hopefully understand the complex systems inherent to the subsurface wherein multiple coupled processes influence contaminant transport and fate.

Subsurface drip irrigation was compared to sprinkler irrigation on bermudagrass turf during three consecutive years using tertiary treated wastewater. Irrigation amount required by each treatment, visual appearance of the grass, shoot biomass production, and soil salinity were measured, and potential management problems were identified. The amount of irrigation water applied via subsurface irrigation was similar or higher than that applied via sprinkler irrigation for a turf of similar quality. Shoot biomass production did not differ between both irrigation methods when similar amounts of water were applied. Soil salinity, measured as electrical conductivity, was monitored at the beginning and end of each season. The changes in electrical conductivity at the end of every irrigation season did not negatively affect the appearance of the turf in any of the years. Emitter clogging by root intrusion was identified as a potential problem in the subsurface drip irrigation system. A series of greenhouse experiments were conducted to evaluate the effect of different herbicides and acids at several concentrations on root intrusion into subsurface drip emitters. The first greenhouse experiment was a study intended to identify chemical concentrations that could inhibit bermudagrass root growth in soil without negatively affecting the visual appearance of the grass. As a result, two herbicides, trifluralin and thiazopyr, and one acid, phosphoric acid, were selected for a second greenhouse experiment. The second greenhouse experiment focused on the effects of the two herbicides and the acid on root intrusion into subsurface drip emitters. Only the emitters treated with thiazopyr at the highest dose were completely clean, root-free emitters.

Eleven series of replicated tests were conducted using 38.1 mm, 15.9 mm, and 9.5 mm gravel to determine the most effective soil surface cover to prevent soil erosion from rainfall. A sediment tray one meter square in size with an integrated rainfall simulator was used to generate data after initial trial runs had established test procedures. Various size gravels and a control with no cover were tested in a laboratory using simulated rainfall to evaluate their effectiveness in preventing erosion. Through thirty-three experiments, signature traits of specific rock sizes were identified. Experiments on 38.1 mm gravel indicated the usefulness of rock mulches in soil erosion prevention. Evaluations with 9.5 mm material indicated that erosion prevention varies inversely with particle size. Experiments with 15.9 mm gravel suggested that this material could increase erosion. This study reflects the ambivalence in the literature and points to the complexity of micro-interactions and erosion potential as influenced by gravel size. Six mechanisms governing rock mulch erosion were proposed.

This research investigated the adsorption mechanisms of hydrophobic chlorinated contaminants in mineral micropores and on iron metal surfaces. Activated adsorption and desorption of trichloroethylene (TCE) in mineral micropores was studied using experimental and molecular modeling techniques. Adsorption of TCE on a silica gel adsorbent was measured using a frontal analysis chromatography technique at atmospheric and elevated fluid pressures. The results showed that the increase in pressure was able to rapidly induce the formation of a desorption resistant fraction. Grand Canonical Monte Carlo (GCMC) modeling was used to elucidate the nature of water and TCE behavior within silica micropores. TCE adsorption was energetically most favorable in pores that were minimally large enough to accommodate one TCE molecule. A molecular level study of the interactions between hydrophobic chlorinated contaminants and sediments was performed. GCMC simulations were preformed to investigate water and TCE adsorption in slit micropores confined by charged and uncharged silica surfaces. Gas-phase single-sorbate simulations with water or TCE were performed as well as mixture simulations of bulk water containing TCE at 1% of its saturation concentration. Aqueous-phase TCE at a concentration equal to 1% of its saturation concentration was able to completely displace adsorbed water in uncharged pores. In highly hydrophilic pores, TCE at this concentration was able to displace up to 50% of the adsorbed water. Metallic iron filings are becoming increasingly utilized as reactive agents for reductive dechlorination of solvents in contaminated groundwaters. This research also used molecular modeling to study chemical adsorption of TCE and PCE to iron surfaces. Quantum mechanical calculations were performed to determine the thermodynamic favorability and resulting structures for chemical adsorption of TCE and PCE to iron surfaces. Molecular mechanics modeling was used to study the effects of atomic hydrogen on the thermodynamic favorability for chemically adsorbed TCE and PCE. Because TCE and PCE react with iron surfaces, their adsorption to iron cannot be investigated experimentally. This makes molecular modeling approaches a useful complement to experimental investigations of chemical reaction phenomena.

One attractive technology for restoration of hydrocarbon-contaminated groundwater is in situ bioremediation, a process where the degradative capacity of biological systems, usually bacteria, is harnessed to facilitate clean-up of environmental pollutants. However, the successful implementation of in situ bioremediation is contingent upon understanding how physicochemical and microbial factors affect the formation and dynamics of microbially active regions, known as bioactive zones (BAZs), in porous media. In this study, a novel, laboratory-scale fiber optic detection system was developed and employed to monitor real-time, in situ BAZ formation and dynamics during naphthalene transport in saturated porous media. Biological activity was measured non-destructively by detecting in situ bioluminescence from Pseudomonas putida RB1353, a naphthalene degrading, lux reporter organism. The first investigation focused on examining the impact of temperature, pH and initial cell number on P. putida RB1353's peak luminescence and V max during naphthalene catabolism. Statistical analyses based on general linear models indicated that temperature, pH, and initial substrate concentration accounted for 99.9% of the variability in luminescence during naphthalene catabolism. These results demonstrated that with careful characterization and standardization of measurement conditions, attainment of a reproducible luminescence response and an understanding of the response are feasible. The second investigation evaluated several potential limitations of the fiber optic detection system and the ability of the detection system to capture BAZ dynamics. The results indicated that the system is not adversely affected by biofilm formation on the optical fiber tips or by bioluminescence attenuation in the porous medium. Additionally, the utility of the detection system was demonstrated by effectively capturing the dynamics of in situ bacterial activity during naphthalene catabolism under changing physicochemical conditions. The third investigation employed the detection system to monitor real-time, in situ BAZ formation and dynamics during naphthalene transport in saturated porous media containing defined physicochemical and microbial heterogeneities. Despite successful transport of bacteria into sterile regions, BAZ formation was limited by local physicochemical conditions. Furthermore, bacterial transport against the advective flow enabled BAZ formation upgradient of inoculated regions. Ultimately, such investigations will improve the utility of in situ bioremediation by enhancing our understanding of BAZ dynamics in complex, heterogeneous systems.

Two of the biggest uncertainties in understanding and predicting climate change are the effects of aerosols and clouds. NASA's satellite mission, CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations, will provide vertical, curtain-like images of the atmosphere on a global scale and assist scientists in better determining how aerosols and clouds affect the Earth's radiation budget. The data from a previous space shuttle mission, LITE (Lidar In-space Technology Experiment, launched in Sept., 1994), have been employed to develop algorithms (e.g., spaceborne lidar system calibration and aerosol retrievals) in support of CALIPSO. In this work, a new calibration approach for 1064 nm lidar channel has been developed via comparisons of the 532 nm and 1064 nm backscatter signals from cirrus clouds. Some modeling analyses and simulations have also been implemented for CALIPSO's narrow bandwidth receiver filter to quantitatively distinguish Cabannes scattering from the full bandwidth Rayleigh scattering and correct the calibration of 532 nm channel. LITE data were also employed in some analyses with the aim of recovering the estimates of the backscatter ratio, R, of clean air regions. The uncertainties in aerosol retrieval due to different error sources, especially the bias and random errors of the extinction-to-backscatter ratio, Sa, have been investigated. A revised Sa table look-up approach is incorporated with two notable revisions for improved S a selection, which, as a consequence enable more bounded aerosol retrievals. Approximate but quantitatively useful multiple-scattering corrections are reported using a modeled multiple scattering factor, eta, which approximates the reduced attenuation caused by multiple scattering. Assessment of multiple scattering effects for a reasonable range of eta values is included for a combination of retrieval approaches.