Adsorption and desorption of naphthalene from C60 fullerene solids in different aggregation forms was studied in this work, where C 60 was used as purchased; or dispersed in water by magnetic mixing; or deposited as a thin film. Finally C60 colloidal dispersion was produced in water with the help of high-energy sonication probe. Sorptive properties of C60 colloidal particles were also studied with naphthalene. Sorption partition coefficients could vary by orders of magnitude and have been observed to be related to the different C60 aggregation forms. Sorption/desorption hysteresis, a common phenomenon observed in natural soils and sediments, was also observed in this work with naphthalene sorbed to well dispersed C60 aggregates. Data were fitted with dual-equilibrium desorption model and results were comparable to literature reported results for natural organic carbons.

The use of water-soluble fullerene-based compounds as sensitizers for reactive oxygen species (ROS) was investigated for the photodegradation of organic contaminants. A variety of conditions were evaluated to determine the production of ROS species by water soluble fullerene. Fullerol was an effective photosensitizer, particular under ultraviolet light. Fullerol produced a mixture of reactive oxygen species under both visible and ultraviolet irradiation. Evidence of both singlet oxygen and superoxide production was obtained. Water-soluble fullerene aggregates were not photocatalytic. Under dark conditions, fullerol appears to act as an antioxidant, while n-C60 had no antioxidant properties and under certain conditions may accelerate the production of ROS. Finally, it was demonstrated that membrane filtration can be used to separate the fullerene compounds from the process water. Nanofiltration membranes were used to remove fullerol from an aqueous solution. Fullerol rejection was approximately 98% and no fouling of the membrane was observed.

The premise that the structure of particle deposits can be predicted based on the knowledge of particle hydrodynamics, solution chemistry and surface chemistry of particles is explored in the framework of three environmental application areas: membrane filtration, in situ capping of contaminated sediments, and environmental sensing. The role of deposit morphology in membrane filtration was evaluated in bench-scale filtration experiments. Results from experiments were compared with theoretical expectations based on a mathematical model for permeate flux for limiting cases of dominant membrane and filter cake resistances. Microscopic examination of membrane cake cross-sections revealed a stratified structure and underscored the importance of coupling between hydrodynamic conditions and interparticle interactions for the permeate flux performance. The influence of suspension heterogeneity on the membrane cake structure was investigated in simulations of particle deposition. Particle Peclet number and collision efficiency were related to trends in colloidal deposit morphology as a function of particle transport and surface chemistry. The simulations identified potential limitations in modeling filter cakes as homogeneous material when suspensions are composed of several chemically distinct particulate fractions. The relationship between sediment cap morphology and transport characteristics across the cap were explored. Bentonite-cement composite is proposed as a new material for in situ capping of contaminated underwater sediments. In addition to being mechanically stable, such composites provide for a possibility to control cap microstructure through the fine-tuning of postdepositional hydration processes in the cap. Cement content and liquid-to-solid fraction were identified as two dominant factors that determine overall cap performance. Microscopic studies of composite structure, strength testing as well as numerical and laboratory modeling of diffusion across composite caps were used to establish formation-structure-performance links for the composites. Finally, the impact of variable deposit morphology on the efficiency of surface-enhanced Raman substrates was investigated. Ionic strength mediated silver nanoparticle deposition was explored as a route for the morphological design of optically active substrates for water quality monitoring. The critical dependence of the effect of surface-enhanced Raman scattering on the morphology of enhancing substrate was quantified as a basis for developing sensors with tunable sensitivity. Fractal analysis was used to quantify deposit morphologies and to correlate these to enhancement factors afforded by the substrates.

Reaeration, or the diffusion of O2 through the unsaturated zone and into an aquifer system, is a mechanism that influences the extent of hydrocarbon contaminant bioattenuation in ground water. A series of laboratory and numerical modeling experiments were completed to determine the amount of O2 supplied to an anaerobic aquifer by reaeration under various unsaturated zone conditions and to quantify the impacts of reaeration on the migration of hydrocarbon plumes in ground water. Results from laboratory experiments indicated that reaeration flux rates exhibited a bimodal distribution and either approached 12,000 Mg/M2-day or were less than 2,000 Mg/M2-day. Soil water content significantly affected the reaeration flux rate while soil type, soil O2 utilization rate, and unsaturated zone thickness did not influence the reaeration rate. In some cases, the capillary rise impeded O2 transport into the bulk ground water due to high water content near the base of the capillary region. An unsaturated zone transport model was developed to predict reaeration flux based on the effective diffusion coefficient of soil (Ds), liquid-side mass transfer coefficient (KL), Soil O2 utilization rate (Rsoil), and unsaturated zone thickness (z). Good agreement was generally found between the predicted and experimental flux results. Results from numerical modeling experiments indicated that reaeration reduced the steady-state length of hydrocarbon plumes in ground water for aquifer hydraulic conductivities of K = 10--2 cm/s and K = 10--4cm/s. Important groundwater reaeration parameters having an influence on the steady-state hydrocarbon plume length included the concentration of O2 in the overlying soil gas (C O2(g)), the ground water mass transfer coefficient (KL,GW), the vertical dispersivity in the saturated zone (alphav), and the zone of reaeration or the thickness of the top model layer (ZR). The relative importance of each of these parameters was on the order of alphav > > KL,GW > CO2(g) > ZR.

The Rice University Fine Particulate Matter Air Sampling Study (1999--2000) identified and quantified the fine particulate matter (PM2.5) in an urban setting in Houston, Texas. The study lasted over two time periods to characterize the seasonal changes; the summer period was between August 16, 1999 and October 1, 1999 and the winter period was between December 18, 1999 and January 31, 2000. PM2.5 was isolated with a cyclone separator and quantified through gravimetric analysis. The major gaseous species (SO 2, gaseous NO3, NH3) and chemical species (organic carbon, elemental carbon, SO42--, NO3 --, NH4+, Na +, K+, and Cl--) were collected by multiple types of filter media and analyzed by ion chromatography, gas chromatography, mass spectrometry, and thermal/optical carbon analysis. PM 2.5 concentration during the summer and winter periods was 8.2 +/- 0.6mug/m3 and 6.2 +/- 0.6mug/m3 respectively and did not exceed the NAAQS PM2.5 standard. The major particulate species (in terms of mass fractions in the summer/winter) were OC (39%/36%), SO4 (20%/9%), NH4 (8%/4%), EC (3%/3%), and NO3 (1%/7%). In both time periods, a large mass fraction was attributed to unknown materials (28%/38%). The OC, SO4, and NH4 mass fraction decreased from the summer to the winter while the NO3 and EC mass fraction increased. The organic fraction of the particulate matter contained n-alkanes and polycyclic aromatic hydrocarbons.

There is often a fraction of contaminants in the subsurface which is observed to persist for long periods of time and resist removal. The phenomenon of incomplete or slow desorption has been shown in the laboratory for many different soil and sediment types and chemicals and a model was developed known as irreversible sorption. Hydrocarbon data from several field sites are compared to the linear and irreversible sorption isotherms and it appears that field data are described by a combination of the linear and irreversible models. A one-dimensional transport model which includes a linear or irreversible term for sorption generally predicts significantly lower concentrations with the linear term than the irreversible term. However, estimates of risk through groundwater and air exposure pathways decrease when sorption is described by the irreversible model. The combination of these factors with the uncertainties that remain presents a complicated problem for site management.

In industrialized countries, many aquatic environments are polluted with contaminants, such as metals. Metals can be found in the particulate matter of the sediment [1, 2]. Metals could be potentially dangerous to biota, if released. The metals can be released to the environment by oxidation due to resuspension (dredging). Neither the water column metal concentrations nor the sediment metal concentrations are good indicators of the amount of metals that will be available during a resuspension. A new method was developed, the new DRET test, to predict the amount of metals available during a six hour resuspension of anoxic sediment using an in-situ ChelexRTM resin as a constant adsorption-potential sink. This method was adapted from DiGiano's et al. [3] DRET test for use with metals instead of organic contaminants. The new DRET test could be used in the field to predict the possible metals available before a resuspension event occurred.

Thesis (Ph.D.)--York University, 2005. Graduate Programme in Political Science. / Typescript. Includes bibliographical references (leaves 294-322). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:NR19786

Submitted to the Fletcher School of Law and Diplomacy. Thesis (Ph.D.)--Tufts University, 2003. / Adviser: William R. Moomaw. Includes bibliographical references (leaves 271-277). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (M. Ed.(Environmental Education) -- University of Pretoria. / Includes bibliographical references. Available on the Internet via the World Wide Web.