Sediments serve as the ultimate sink for many hydrophobic organic compounds and thus present a residual environmental risk many years after sources of contamination are eliminated. Monitored natural attenuation and ex situ treatment processes are often ineffective for treatment; as such in situ remediation technologies (i.e., capping) are under review. A conventional in situ remediation technology for refractory sediment contaminants is placement of a clean layer of material as a cap. A series of design models was developed to predict the performance of caps composed of the traditional material, sand. A passive sampling method using polydimethylsiloxane (PDMS) fibers for evaluating the performance of caps was developed and tested in the laboratory. The results of the laboratory analysis showed the ability to measure pore water concentration profiles in caps, the consistency of profiles with design model predictions, and correlation of PDMS-derived concentrations with contaminant uptake in test organisms. Potentially more effective caps composed of permeable adsorptive materials (to retard contaminant migration) and impermeable materials (to divert groundwater flow) were placed along with a conventional sand cap in the Anacostia River in Washington DC in 2004. Field tests of this site showed the ability to measure in situ pore water concentration profiles in caps using a field-deployable version of the PDMS passive sampling device and demonstrated the necessity of pore water-based approaches for analyzing caps. A model for assessing the uptake rates of HOCs within PDMS fibers was developed and shown to predict the kinetics of HOC sorption into fibers. The model is based on external-mass transport processes, which through a series of analyses were shown to be more significant than internal diffusion in PDMS fibers. Using the PDMS approach, field bioaccumulation tests at the Anacostia site as well as at San Diego Bay and Hunters Point Naval Shipyard showed stronger correlation of PDMS-based pore water concentrations than solid-phase concentrations with observations of bioaccumulation in the field. The overall conclusions suggest that pore water concentrations can often be a better indicator of risk than bulk solid concentrations. / text

Mercury has been an element of great industrial importance since early times.This wide utilization of the element has led to pervasive mercury contamination in theglobal environment. Due to mercury's high toxicity, this is a matter of great concern. Anumber of methods, includ ing phytoremediation, filtration, and precipitation/chelation,have been investigated to remove mercury from the environment. Unfortunately, thesemethods are not entirely satisfactory for the in-situ remediation of mercury from aqueousenvironments.The hypothesis of this dissertation is that this can best be accomplished by theaddition of a large and flexible sulfur-based chelate, that will bind mercury in atetracoordinate and presumably tetrahedral environment, to mercury-contaminatedwaters. Although this proved difficult due to the tendency of these ligands to decomposeinto smaller, sulfur-containing rings, the synthesis and characterization of such a chelatewas achieved. Several potential mercury-binding ligands were eventually synthesizedsignificant amounts of mercury (91-100%) from the contaminated solutions, in one caselowering the mercury levels in the water to below the CVAF detection limits. Theresulting solids lost little (andlt;15 ppb) of their mercury during leaching studies.This work demonstrates the use of tetradentate chelates in precipating Hg2+ fromwater to produce stable mercury- ligand precipitates. A calculation for the quantification ofthe geometry of a four-coordinate compound was also developed and applied to aluminum,gallium, and mercury compounds. This calculation could also be applied to the mercurycompounds described in this thesis once X-ray structures become available

Residues of 2,4,6-trinitrotoluene (TNT) in soil and groundwater near former production and processing plants generate large environmental concerns. A cyclodextrin (CD) mediated Fenton remediation of TNT contaminated water and sand (soil analogy) is presented. Kinetic studies were performed to elucidate the role of cyclodextrin in Fenton remediation of TNT contaminated water. The rate and extent of TNT degraded by Fe2+- CD-H2O2 systems were significantly enhanced as compared to the classic Fenton method. Further, in water system with interfering substance - humic acid, which tends to associate with TNT, the addition of cyclodextrin helped to improve the efficiency of Fenton degradation. This technique has also been successfully applied to remediate TNT contaminated soil systems (sand). Four systems were investigated: clean sand, sand and humic acid, sand and fulvic acid, sand and natural organic matter. This technique has shown superior performance than classic Fenton method in all of the four above systems.

Nitroaromatic explosives, such as trinitrotoluene (TNT), are of particular environmental concern due to their recalcitrance in soils and their potent toxicity and mutagenicity to both aquatic and mammalian species. TNT was the most widely used military explosive through the era encompassing both the First and Second World Wars. As a result, there is widespread contamination of soils by TNT around weapons manufacture, testing, and disposal facilities. Fenton chemistry (ferrous ion catalyzed generation of hydroxyl radicals) has shown utility in the remediation of TNT in soils but it suffers from non-specificity and the need for acidic conditions to prevent loss of iron as iron hydroxides. Cyclodextrins (CDs) have demonstrated the ability to increase the efficiency of Fenton degradation of aromatic pollutant species. The increase in degradation efficiency observed in the CD Fenton reaction systems has been credited to the formation of a pollutant/CD/ferrous ion ternary complex which has the ability to produce hydroxyl radicals at the site of bound ferrous ions during Fenton reactions. This results in an increase in hydroxyl radical concentration near the target guest molecule relative to the bulk solution, leading to a targeted degradation of the complexed guest molecule. In order to assess the viability of CD assisted Fenton reactions for the remediation of TNT, a thorough knowledge of the kinetics, degradation products, and role of binary and ternary complexes is required. Research presented in this dissertation examined the role of CDs in the Fenton oxidation of TNT, specifically: 1) the kinetics of TNT degradation in the presence of CDs for a Fenton reaction system, 2) the products of these reactions through chromatographic and mass spectrometric methods, and 3) NMR and binding studies of binary and ternary complexes.

Semiconductor photocatalysis degrades phenolic pollutants to carbon dioxide and water, but the mechanisms of this potentially attractive method of environmental remediation remain unclear. This study aimed to elucidate the primary molecular events by HPLC analysis of the initial products of degradation in water or aqueous acetonitrile. The position of substituents relative to the hydroxyl group were found to influence the reaction rate and also primary oxidation steps, and hence the intermediate profile. 2,6- Dialkylated phenols reacted fastest and showed high conversion to dehydrodimeric products as a prelude to degradation. In contrast, 3,5-dialkylated phenols and 4-tertbutylphenol reacted more slowly and appeared to degrade directly to small polar compounds with little accumulation of primary carbocyclic intermediates. The rate of photocatalytic degradation of two isomeric dibromohydroxybenzonitriles was also influenced by substitution pattern. 3,5-Dibromo-2-hydroxybenzonitrile, however, is itself photolabile in daylight giving 3-bromo-2,5-dihydroxybenzonitrile in aqueous solution. The analogous reaction does not occur for 3,5-dibromo-4-hydroxybenzonitrile, the difference in behaviour being attributed to differences in the electronic spectra of the two compounds. The mechanism of photocatalysis appears to be influenced by the orientation of the substrate on the catalyst surface. For the alkyl phenols, particularly those with tert-butyl substitution, minimisation of disturbance to the polar network of the solvent directs the more hydrophobic parts of the molecule towards the oxidising surface of the catalyst. In addition, this effect encourages clustering of molecules with the subsequent formation of aggregated products. While part of the behaviour observed may be attributable to the presence of acetonitrile in the solvent, the hydrophobic profile of a substrate undergoing heterogeneous photocatalytic oxidation in water would seem to be a significant determinant of the molecular pathway selected in the first phase of its degradation.

No description available.

In the development of a non-aqueous bitumen extraction process, a major obstacle is solvent loss due to hydrocarbon attachment to the reject sand grains. A proposed solution to this problem is to wash (i.e. remediate) the oil-contaminated sand grains with water and surfactants. This research is focused on developing a protocol to evaluate the performance of particular surfactant types and water chemistry; emphasis was placed on using minimal amounts of water to recover the residual oil. To start, a series of jar tests were conducted (using heptane and hexadecane as solvents)to study the phase behaviours of oil-water-surfactant ternary systems. This was followed by the development of a new washing protocol for the purpose of evaluating remediation performance. Finally, the correlation between overall remediation performance and the oil-water interfacial tension was discussed.

Transition metal nanomaterials are used to catalyze many chemical reactions, including those key to environmental, medicinal, and petrochemical fields. Improving their catalytic properties and lifetime would have significant economic and environmental rewards. Potentially expedient options to make such advancements are to alter the shape, size, or composition of transition metal nanocatalysts. This work investigates the relationships between structure and catalytic properties of synthesized Au, Pd-on-Au, and Au-enzyme model transition metal nanocatalysts. Au and Pd-on-Au nanomaterials were studied due to their wide-spread application and structure-dependent electronic and geometric properties. The goal of this thesis is to contribute design procedures and synthesis methods that enable the preparation of more efficient transition metal nanocatalysts. The influence of the size and composition of Pd-on-Au nanoparticles (NPs) was systematically investigated and each was found to affect the catalyst’s surface structure and catalytic properties. The catalytic hydrodechlorination of trichloroethene and reduction of 4-nitrophenol by Pd-on-Au nanoparticles were investigated as these reactions are useful for environmental and pharmaceutical synthesis applications, respectively. Structural characterization revealed that the dispersion and oxidation state of surface Pd atoms are controlled by the Au particle size and concentration of Pd. These structural changes are correlated with observed Pd-on-Au NP activities for both probe reactions, providing new insight into the structure-activity relationships of bimetallic nanocatalysts. Using the structure-dependent electronic properties of Au NPs, a new type of light-triggered biocatalyst was prepared and used to remotely control a model biochemical reaction. This biocatalyst consists of a model thermophilic glucokinase enzyme covalently attached to the surface of Au nanorods. The rod-like shape of the Au nanoparticles made the thermophilic-enzyme complexes responsive to near infrared electromagnetic radiation, which is absorbed minimally by biological tissues. When enzyme-Au nanorod complexes are illuminated with a near-infrared laser, thermal energy is generated which activates the thermophilic enzyme. Enzyme-Au nanorod complexes encapsulated in calcium alginate are reusable and stable for several days, making them viable for industrial applications. Lastly, highly versatile Au nanoparticles with diameters of ~3-12 nm were prepared using carbon monoxide (CO) to reduce a Au salt precursor onto preformed catalytic Au particles. Compared to other reducing agents used to generate metallic NPs, CO can be used at room temperature and its oxidized form does not interfere with the colloidal stability of NPs suspended in water. Controlled synthesis of different sized particles was verified through detailed ultraviolet-visible spectroscopy, small angle X-ray scattering, and transmission electron microscopy measurements. This synthesis method should be extendable to other monometallic and multimetallic compositions and shapes, and can be improved by using preformed particles with a narrower size distribution.

For one hundred years, the mighty blast furnaces of Stelco have burned, melted, and forged the identity of Hamilton, Ontario, into the epitomic Steeltown of Canada. Now US Steel Canada, its recently announced closure has silenced the operation that once defined Hamilton itself, leaving in its wake an array of ruined machines upon a toxic wasteland. But is it really a wasteland? Could the energy latent in the site, its architecture, and its history be recovered? In order to propel the city towards a more sustainable future, could its degradation be used as an agent for change, to transform the site and even provide the basis for a new hybrid industry? This thesis proposes an architectural design for a recalibrated steel industry on the site whose excess energy output is used to fuel a new industry of greenhouses. These greenhouses nurture plants to be used in the gradual bioremediation of the contaminated landscape into a site of both active industry and civic amenity. Through the re-ignition of the blast furnace and the subsequent design opportunities it creates, the site becomes an extension of the civic realm rather than an obstruction to it. Three areas of focus define this thesis proposal. The first is an exploration into the opportunities latent in ruination, both architecturally through entropy and in landscape through toxic contamination. This is followed by an investigation into the century-old relationship between Stelco and Hamilton, and how this history has created the current state of tension between industry and city. Finally, through the re-imagination of the blast furnace and its output, this thesis positions the site as part of an energy flow that links industry with its landscape, and both with the city in which they reside.

Perchlorate is a threat to public health through water but also food. However, there is no effective chemical treatment process which can destroy perchlorate found in groundwater and surface water. Thus, there is growing interest in developing effective technologies, especially chemical treatments, to completely destroy trace levels of perchlorate present in drinking and groundwater. The research on perchlorate reduction by zero-valent titanium (Ti(0)) showed that perchlorate was effectively reduced to chloride using electrochemically developed pitting corrosion on Ti(0). Perchlorate reduction was believed to be caused by an active reductant (dissolved Ti(II)) during the pitting corrosion of Ti(0). The rate of perchlorate reduction was independent on the imposed potential as long as the potential was maintained above the pitting potential of Ti(0), but it was proportional to the applied current. The perchlorate reduction on the pitting developed Ti(0) was inhibited by the presence of chloride and bromide. Inhibition mechanism of perchlorate reduction inhibition was believed to be caused either by competitive adsorption of aggressive anions on bare Ti(0) surface or Ti(II) consumption by electrochemically produced chlorine. Kinetic models were developed based surface coverage of aggressive anions on bare Ti(0) and Ti(II) oxidation by chlorine. These kinetic models supported the perchlorate concentration change in the solution, but Ti(II) consumption model was not able to predict chloride concentration due to insufficient information describing complex nature of pitting on Ti(0). These results shown in this research demonstrate that pitting corrosion developed Ti(0) has the capability to chemically reduce perchlorate present in natural water and engineered systems as well as possible problems associated with electric input. This research may be a starting point for development of a new treatment process that applies titanium or titanium metal ions as a chemical reductant to abate contaminants present in natural and engineering systems. Further developments can be achieved by alloying titanium metal with other metals such as iron and aluminum, and finding a methodology producing stable Ti(II) in ambient conditions.