Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 136-138).

Thesis (M.S.) in Chemical Engineering--University of Maine, 2001. / Includes vita. Includes bibliographical references (leaves 77-79).

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 194-200). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.) in Physics--University of Maine, 2001. / Includes vita. Includes bibliographical references (leaves 122-128).

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The first study focused on the magnitude and rate of sorption of hydrophobic organic compounds by two, well-characterized soils. The composition of organic matter had a small effect on the magnitude of the organic carbon normalized equilibrium distribution coefficients. The sorbates sorbed more strongly to the humic-coated soil, most likely due to the organic matter's less polar nature as compared to the fulvic material. The molecular solute descriptor, ¹Xᵛ, performed slightly better than the empirical solute descriptor, K(ov), in evaluating equilibrium sorption coefficients. Thus, sorbate structure may have a secondary influence on the overall magnitude of equilibrium sorption. Sorbate structure exhibited a greater influence on sorption kinetics than on sorption equilibrium. Distinct differences in the magnitudes of mass transfer coefficients for the humic and fulvic soils were observed when relating them to the molecular solute descriptor, ¹Xᵛ. The differences in mass transfer coefficients were attributed to both sorbate structure and the quantity and morphology of soil organic matter. The intrasorbent diffusion coefficients were believed to be the same for both the humic and fulvic material. The second study focused on using a biodegradable solute to measure processes that affect in-situ biodegradation during well-controlled field and laboratory experiments. Specifically, this study investigated how residence time and scale influence the extent and rate of in-situ biodegradation of an organic solute undergoing transport. The transport of the biodegradable solute was compared to that of bromide and/or pentafluorobenzoic acid, which are conservative, non-degradable tracers. Laboratory experiments were conducted to simulate both the flow velocity and residence time conditions existent in the field. Mass recovery the biodegradable solute decreased as the residence time increased, ranging from 14 to 95 percent for the field sites. Mass recoveries in the laboratory experiments were approximately 30% to 40 % less than in the field experiments. The first-order biodegradation rate constants did not vary with residence time for either field site. In addition, the average rate constant value for both field sites was very similar (0.21 d⁻¹).

In this thesis two studies of reactive metal adsorption upon a low index single crystal silicon dioxide surface are presented in addition to a study of sulphur adsorption upon a low index single crystal nickel surface. Chromium growth upon the a-quartz Si02(0001) (J84xJ84) Rll 0 surface is studied at three coverages, 0.25±O.08 ML, 0.5±O.16 ML and 1.0±0.33 ML, using surface extended x-ray absorption fine structure (SEXAFS). SEXAFS measurements, from the chromium K-edge, recorded at both grazing and normal incidence show that chromium growth proceeds via the formation of mesoscopic particles with a body centred cubic (b.c.c.) like structure having an average nearest neighbour Cr-Cr distance of 2.36±O.03 A. This represents a contraction of 5.6 % from the bulk b.c.c. lattice spacing of 2.49 A. There is no evidence of a surface reaction between chromium and the surface oxygen. SEXAFS was used to study titanium reactional growth on a-quartz (0001) (J84xJ84) Rll 0 and (lx1). Three nominal coverages were studied, 0.25±O.08 ML, 0.5±O.16 ML and 1.0±O.33 ML. Both normal and grazing incidence SEXAFS data were recorded and show the formation of a spatially extensive region in which an interfacial reaction has occurred between surface oxygen and adsorbate titanium atoms. Coupled with this is the formation of subnanometre titanium clusters. The metal oxide has nearest neighbour Ti-O distances close to those of both the anatase and rutile forms of titania with the metallic titanium clusters having a Ti-Ti distance within experimental error that of bulk hexagonal close packed (h.c.p.) titanium, 2.89 A. A re-examination of the surface geometry of Ni(1l0)c(2x2)S using SEXAFS has been performed. Data out to an electron wavevector of 9 A-I are analysed with a new code to assess the influence of multiple scattering. The first shell S-Ni distance is determined to be 2.20±O.02 A with the next nearest neighbour distance being 2.29±O.02 A, giving a top-layer Ni expansion of 14±3% relative to the bulk. The influence of multiple scattering does not significantly alter these values from earlier studies.

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