Thesis (Ph. D.)--Drexel University, 2004. / Includes abstract and vita. Includes bibliographical references (leaves 161-172).

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 64-72).

Thesis (PH. D.)--Michigan State University. Civil Engineering, 2008. / Title from PDF t.p. (viewed on Sept. 2, 2009) Includes bibliographical references (p. 267-278). Also issued in print.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006. / Dr. Kurt Pennell, Committee Member; Dr. Jim Spain, Committee Member; Dr. Joseph Hughes, Committee Chair

The comprehensive environmental dynamics of the heterocyclic Benzimidazole fungicides, Benomyl and Thiabendazole was investigated. This included examining their fate and distribution in the terrestrial and aquatic phases of a laboratory microcosm comprised of silty clay loam soil and plants. The soil component constituted a major relocation site, with approximately 45 and 75% of initial Benomyl (recovered as MBC) and Thiabendazole concentrations being recovered from the soil component of the microcosm, respectively, while 53 and 27% translocated into corn plants. The adsorption mechanism/s of these fungicides onto soil components were investigated using silty clay loam, silty loam and sandy soils as well as Ca-bentonite. These studies indicated that both fungicides were adsorbed to the highest degree on silty clay loam, followed by silty loam and sandy soils. Their adsorption on Ca-bentonite was found to be a function of the pH of the suspension, suggesting that in the presence of increasing ll *activity on the clay surfaces, Benomyl and Thiabendazole become protonated to form positively charged molecules. These may then react with the clay surfaces forming Fungicide-clay complexes. The effect of different CaCl, concentrations on the adsorption process demonstrated that an increase in the salt concentration, at a constant pH resulted in a decrease in the amounts of adsorbed fungicide. The transport of the fungicides (adsorbed onto soil particles) as a consequence of scdiment runoff into aquatic systems was also estimated. Results of the simulation of overland sediment runoff from sections of the Chowan river basin into the Meherrin river following a rainstorm, indicate that significant quantities of Benomyl and Thiabendazole could be transported into aquatic systems. Adsorption studies also indicated that the adsorption process is reversible. Thus, any significant increases in the pH of receiving bodies of water could result in the release of Benomyl and Thiabendazole from sediment causing a contamination of the aquatic system. / Master of Science

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Swelling attributable to intracrystalline water adsorption by montmorillonite (MT) and vermiculite (VR) saturated with cations which limit interlayer expansion were calculated as the product of one-half the change in interlayer spacing determined by x-ray diffraction and the difference between total surface area taken as 800 m²/g and external crystal surface area measured by N₂ gas adsorption. Swelling directly attributable to osmotic adsorption was calculated as the product of external surface area and theoretical double layer thickness. In homoionic, monomineralic systems of Ca- and Al-MT and Na-, Ca- and Al-VR, intracrystalline expansion accounted for 60, 70, 21, 56 and 44%, respectively, of total expansion during saturated vapor-wetting and 15, 50, 4, 12 and 13% during submersion in 0.01 N electrolyte solutions. Osmotic adsorption of these systems accounted for < 10% of the expansion on submersion in all cases. Dry, static compaction of Ca-MT resulted in an increase in expansion with increasing initial density which was not explained by changes in predicted osmotic or intracrystalline expansion. This was attributed to expansion caused by gaseous pressures developing ahead of advancing wetting fronts. An inverse relationship was found between pore size and swelling caused by entrapped air pressures. Slow wetting ameliorated this expansion by allowing dissipation of entrapped air. Relaxation of crystal strains during wetting was also implicated as contributing to expansion. Electron microscopy revealed crystal strain decreased in the order: Na-MT > Ca-HT > Al-MT > Na-VR ≃ Ca-VR ≃ Al-VR. Greater expansion by freeze-dried than oven-dried Ca-MT was explained by greater crystal strain observed in the former clay. Greater strain broadening of the (060) x-ray diffraction peak was observed for the freeze-dried clay and its mean b-dimension was slightly smaller than the oven-dried clay. Crystal strain relaxation is suggested to explain the relationship between b-dimension and swelling reported in the literature. Predicted osmotic expansion for two soils was greater than in the pure clay systems and intracrystalline expansion smaller, due to a greater ratio of external to internal surface area in the soils. Osmotic adsorption accounted for 30-70% of the soil swelling during submersion in 0.0lM electrolyte solutions, while intracrystalline expansion accounted for < 10%. The magnitude of swelling due to entrapped air pressures was evaluated from the difference between expansion of atmospheric pressure-wet and vacuum-wet clods. This component accounted for 10-60% of the expansion of undisturbed and compacted samples during the second cycle of wetting from the air-dry state, but did not appear to be directly related to pore size. Changes in structure accompanying air-drying appeared to enhance expansion, especially for the high MT Iredell soil. It was suggested that this may be the result of increases in crystal strain during drying. / Ph. D.

Soils and groundwaters face an influx of contaminants, many of which are known to be hazardous to the public's health. Several remediation technologies have been developed to clean-up contaminated soils, but additional information on the behavior of organic chemicals in the subsurface environment is needed for effective remediation. The purpose of this study was to investigate the relationship between sorption and biodegradation on the ultimate fate of subsurface contaminants. Sorption and biodegradation of phenanthrene, a hydrophobic polycyclic aromatic hydrocarbon, were modeled using soil and water microcosms. The soils were prepared in the laboratory from a parent soil to obtain sorbents that were similar in all respects except for soil organic matter content. Biodegradation was evaluated by production of CO2 and disappearance of phenanthrene from the sorbed and aqueous phases. The sorption of phenanthrene to each soil occurred in two distinct stages. The majority of phenanthrene mass sorbed during the first few days. After the initial rapid sorption period, the sorption rate continually decreased. The time required for complete sorption varied according to soil organic matter content, with soils having higher organic matter contents requiring more time for complete adsorption. Desorption of phenanthrene from soils was hysteretic, although it appeared that phenanthrene would completely desorb. Phenanthrene desorption rates decreased as the chemical exposure time increased. The biodegradation of phenanthrene also occurred with a fast and slow phase. The slowly degradable fraction increased with soil organic matter content. The data suggest that the biodegradation of phenanthrene is desorption controlled. / Master of Science