No description available.

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

This study presents the results from laboratory investigations of the capacity of kaolinite to adsorb heavy metals including copper, nickel, cadmium, and lead. Kaolinite is a clay commonly found in suspended solids and sediments in natural water systems. The purpose of the study was to evaluate the validity of the competitive adsorption equation presented by weber in describing metal adsorption on kaolinite. This equation describes adsorption competition among the components of a mixture of solutes. Adsorption studies were conducted for single and mixed metal systems. Controlling factors considered include solution pH, clay dosage, and cation competition. The investigation demonstrated that the competitive adsorption equation is a valid and useful equation for describing the adsorption of mixed metal systems on kaolinite. The equation may be used to predict equilibrium metal concentrations in mixed metal systems. The results of the study also indicated that the rate of adsorption of the metals on kaolinite was very rapid. Equilibrium was complete within thirty minutes of the addition of the metals to the clay. / Master of Science

Hydrophobic organic contaminants released into the subsurface can become sorbed to the soil matrix. The sorbed compounds may slowly leach into the groundwater, providing a long-term source of contamination. Bioremediation has been cited as a potential clean-up strategy for residual organics in soils. At present, factors which control biological utilization and retention of organic contaminants in the subsurface are poorly understood. The purpose of this study was to investigate how the adsorption/desorption and biodegradation processes interact to control the distribution and biological fate of subsurface contaminants. Batch soil microcosms were used to evaluate the sorption of a chlorinated aromatic compound [2,4,6-trichlorophenol (TCP)] to mineral soils, organic soils, and dissolved macromolecules (humic acid). Microbial utilization of 2,4,6-TCP was then evaluated after addition of a bacterial culture previously acclimated to the substrate. Biodegradation was evaluated by production of ¹⁴CO₂ and disappearance of 2,4,6-TCP from the sorbed and solution phases. Size exclusion chromatography was used to distinguish between free 2,4,6-TCP in solution and 2,4,6-TCP bound to humic acid in solution. Sorption of 2,4,6-TCP to mineral surfaces was rapid but sorption to organic soils varied with contact time. Most 2,4,6-TCP sorption to organic soils occurred during the first few days of contact with the soil. However, the sorption rate gradually decreased with time and 2,4,6-TCP continued to sorb for weeks at a reduced rate. The amount of 2,4,6-TCP which sorbed at the slower rate was dependent upon the organic matter content of the soil. Desorption of 2,4,6-TCP from organic soils was similar to adsorption; however, it appeared that slow desorption took longer than slow adsorption. Humic acid in solution formed an additional phase to which 2,4,6-TCP sorbed. The sorption capacity of dissolved humic acid was a function of the humic acid concentration. Higher concentrations of humic acid had lower sorption capacities when normalized for total organic carbon content. The mineralization rate of 2,4,6-TCP by Pseudomonas aeruginosa was dependent upon the initial substrate concentration. Total mineralization of 2,4,6-TCP by P. aeruginosa decreased in the presence of organic soils. However, mineralization rates were elevated in organic soils compared to mineral soils after 5 days of incubation. This was attributed to an influx of substrate into solution from an initially sorbed state. Total mineralization of 2,4,6-TCP in humic-containing solutions was reduced by 5-10 % over humic-free solutions. The bioavailability of 2,4,6-TCP was greatly reduced in the sorbed state. Biodegradation of unbound 2,4,6-TCP in solution was very rapid while biodegradation of 2,4,6-TCP sorbed to organic soil or to dissolved humic acid was much reduced. Desorption of most 2,4,6-TCP from soil was rapid, thereby becoming available to acclimated bacteria. However, a small quantity of 2,4,6-TCP desorbed from organic soil and dissolved humic acid very slowly and became available for biodegradation at a rate limited by desorption. / Ph. D.

Thesis (M.S.)--Oregon State University, 1996. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Graduation date: 1994

An infiltration-wetting agent study, using the wetting agent "WATER-IN", was conducted in the ponderosa pine forest type of east central Arizona, near McNary, Arizona. An application rate of 10 gallons of wetting agent per surface acre was used both on bare mineral soil and on ponderosa pine litter. The infiltration rate was measured by a modified North Fork infiltrometer. It was found that "WATER-IN" significantly increased water runoff, when applied to litter, but when applied to bare mineral soil, "WATER-IN" caused a significant increase in water infiltration. The wetting agent did not significantly affect antecedent moisture, soil particle distribution, litter water holding capacity, or litter bulk density. It is presently hypothesized that the increase in water infiltration on treated bare mineral soil is due to a decrease in the average bulk density of the surface inch of soil. The data strongly suggests this hypothesis to be correct. The increase in runoff when litter is treated is probably due to an interaction, either physical, chemical, or both, between the humus layer and "WATER-IN", creating a hydrophobic condition where one did not exist before.

No description available.

It was found that Azotobacter vinelandii grown in a dialyzed soil medium did not fix nitrogen and had a much lower rate of respiration than when grown in Burk's nitrogen-free medium. When para-hydroxybenzoic acid served as the added oxidizable organic carbon source in dialyzed soil medium, the azotobacter grown in it were found to be unable to fix nitrogen. On the other hand, A. vinelandii fixed nitrogen when grown in soil supplemented with glucose. It was concluded that natural conditions in the soil are not conducive to nitrogen fixation by A. vinelandii.