The importance of the cryosphere, and of sea ice in particular, for contaminant transport and redistribution in the Arctic was pointed out in the literature. However, studies on contaminants in sea ice are scarce, and entirely neglect the sea ice geophysical and thermodynamic characteristics as well as interactions between various cryospheric compartments. This thesis addresses those gaps. Ice formation was shown to have a significant concentrating impact on the levels of HCHs in the water just beneath the ice. Both geophysical and thermodynamic conditions in sea ice were shown to be crucial in understanding pathways of accumulation or rejection of HCHs. Although HCH burden in the majority of the ice column remains locked throughout most of the season until the early spring, upward migration of brine from the ice to the snow in the winter has an effect on levels of HCHs in the snow by up to 50 %. In the spring, when snow melt water percolates into the ice delivering HCHs to the upper ocean via desalination by flushing, levels of HCHs in the ice can increase by up to 2 %-18 % and 4 %-32 % for α- and γ-HCH, respectively. Brine contained within sea ice currently exhibits the highest HCH concentrations in any abiotic Arctic environment, exceeding under-ice water concentrations by a factor of 3 in the spring. This circumstance suggests that the brine ecosystem has been, and continues to be, the most exposed to HCHs. α-HCH levels were shown to decrease rapidly in the last two decades in the Polar Mixed Layer (PML) and the Pacific Mode Layer (PL) of the Beaufort Sea due to degradation. If the rate of degradation does not change in the near future, the majority of α-HCH could be eliminated from the Beaufort Sea by 2020, with concentrations in 2040 dropping to < 0.006 ng/L and < 0.004 ng/L in the PML and the PL, respectively. Elimination of α-HCH from sea water takes significantly longer than from the atmosphere, with a lag of approximately two decades.

The research involved determining the processes that occur during dye diffusion thermal transfer printing. Dye diffusion printing is a novel method of printing photo quality graphics from a personal computer. The process involves two polymer films coming into contact, one containing a dye, and the diffusion of the dye from this donor sheet onto the receiving sheet using heating elements to drive the diffusion process. In this high temperature, high pressure, and short time scale regime undesirable adhesion between the two polymer sheets is observed. It is this adhesion and its mechanisms that were investigated. Several types of homopolymers were used in.an attempt to obtain information on the processes involved in the adhesion of the two films during the printing stage. Initially dyes were absent from the polymer films to examine the polymer adhesion alone. It was hoped that the principal factors involved in the unusual joint forming conditions could be explained. The unusual conditions are high heat (250°C) and short time span (10-15 milliseconds). Polystyrene, poly (methyl methacrylate) and poly (vinyl acetate) were chosen to determine the effect of Glass Transition Temperature (T g), surface energies and molecular weight on the polymer adhesion. Initial results showed that the adhesion was a complex system. but it became clear that the t g of the polymers and the presence of small molecules and contaminants· were very important. Work with commercial polymers was undertaken to transfer the knowledge gained from the homopolymers to the more complicated commercial systems using poly (vinyl. chloride) and poly (vinyl butyral). To expand the understanding of the results small molecules and dyes were added to these commercial polymers to examine their effects. The surface of the samples were analysed using X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR). This was used to determine if there was any migration of the small molecules to the surface of the polymer films. It was also useful in indicating the location of the dyes and how much penetration into the polymers is achieved by them. Atomic Force Microscopy (AFM) was implemented to analyse the surface morphology and gave an insight into the mechanism of the small molecule migration. The conclusions drawn were that the presence of small molecules had significant affect on the adhesion of the polymers. Compatible small molecules would act as plasticisers and lower the T g of the polymers giving rise to higher adhesion. Small molecules that were incompatible were found to migrate to the surface in large quantities and would act as weak boundary layers, significantly reducing the adhesion. Work in this area has shown that an autolayering mechanism is occurring that may be useful in producing a release mechanism for the commercial products.

Dans le cadre de l’initiative « Generation IV », les conséquences d’un accident grave (AG) sur un Réacteur à Neutrons Rapides refroidi au sodium (RNR-Na) doivent être étudiées. L’interaction entre le cœur chaud et le sodium liquide peut engendrer une explosion de vapeur qui pourrait créer une brèche dans le système primaire. Le sodium liquide contaminé pourrait être ainsi pulvérisé dans l’enceinte de confinement. Pour évaluer les conséquences d'une telle situation accidentelle en cas de perte du confinement, il faut au préalable pouvoir prévoir l'évolution de la quantité et de la spéciation chimique des radionucléides dans cette enceinte. / In the context of the Generation IV initiative, the consequences of a severe-accident (SA) in a sodium-cooled fast reactor must be studied. A SFR (Sodium cooled Fast Reactor) severe accident involves the disruption of the core by super-criticality involving the destruction of a certain number of fuel assemblies. Subsequently the interaction between hot fuel and liquid sodium can lead to a vapor explosion which could create a breach in the primary system. Some contaminated liquid sodium would thus be ejected into the containment building. In this situation, the evaluation of potential releases to the environment (the source term) must forecast the quantity and the chemical speciation of the radiocontaminants likely to be released from the containment building.

The use of manure from animal feeding operations (AFOs) as fertilizer on agricultural land may introduce contaminants to aquatic environments that can negatively affect the health of aquatic organisms. This study utilized a landscape-scale regression-based design to assess the effects of AFOs on contaminant concentrations and resident populations of a pleurocerid snail, Leptoxis carinata, in streams within the Shenandoah River watershed (Virginia, USA). Individual characteristics of L. carinata were also evaluated to provide further understanding of observed population characteristics. In streambed sediment and mollusk tissue, concentrations of the trace element arsenic, used as an additive in poultry feed, were not directly related to watershed densities of AFOs. In-stream concentrations of dissolved nutrients and estrogenic compounds, measured as estrogenic activity, were directly related to watershed densities of AFOs. Population sex ratios of L. carinata varied across study sites, from balanced to female-biased, but were not related to concentrations of estrogenic compounds. However, the spatial variation in population sex ratios, coupled with little variation in site-specific sex ratios across seasons and generations, suggest an influence of site-specific environmental conditions. Individual-level studies of L. carinata revealed that there is an eight month lag between hatching and gametogenesis which could allow disruption of sexual differentiation by environmental contaminants, but further study of the effects of specific contaminants on sexual differentiation in this species is needed. Population densities of L. carinata were related to in-stream nutrient concentrations and landscape sources of nutrients, including AFOs, but none of these factors were directly related to the infection prevalence of digenetic trematodes in L. carinata populations. Although trematode infection rates in L. carinata populations do not appear to be viable indicators of the influence of eutrophic conditions on disease incidence in aquatic organisms, the identification of five types of trematodes in L. carinata populations highlights the utility of this snail species for further investigation of transmission dynamics of trematode parasites in lotic systems. / Ph. D.

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No description available.

In environments characterized by low pH and/or high nitrate, the biomineralization of U(VI)-phosphate minerals represents a uniquely suited bioremediation method involving microbially-mediated hydrolysis of organophosphates coupled to a chemical precipitation of sparingly soluble U(VI)-phosphate minerals. In this study, the ability of natural microbial phytases to hydrolyze phytate, a naturally-occurring and abundant organophosphate, and precipitate uranium-phosphate minerals was investigated through a combination of sediment microcosms, soil slurries, and pure culture studies. In this study, biomineralization of U(VI)-phosphate minerals promoted by addition of glycerol-2-phosphate was shown to outcompete bioreduction in anaerobically-maintained sediment microcosms containing contaminated soils. Addition of phytate to aerobic soils slurries containing ORFRC soils also resulted in significant production of inorganic phosphate, and two microorganisms that efficiently hydrolyze phytate were isolated from these experiments. Overall, the results of this study demonstrate phytate hydrolysis by subsurface microorganisms coupled to precipitation of U(VI)-phosphate minerals for the first time, suggesting that phytate may represent an ideal organophosphate to promote this process.

Pharmaceuticals and personal care products (PPCPs) enter aquatic ecosystems through multiple pathways including human excretion into sewage systems, disposal of surplus drugs, and the therapeutic treatment of livestock. Because PPCPs are designed to have a physiological effect, it is likely that they may also influence aquatic organisms. The objectives of this research were to quantify PPCP abundance in near-shore habitats of Lake Michigan and identify factors related to PPCP abundance. Stratified sampling was conducted seasonally at four southern Lake Michigan sites. All sites sampled had measurable PPCP concentrations, but they varied significantly among time and location. Concentrations of PPCPs did not differ with site or water depth. Multiple regression analyses revealed that temperature, total carbon, total dissolved solids, dissolved oxygen, and ammonium controlled total PPCP concentrations. These data indicate PPCPs are ubiquitous in southern Lake Michigan with continued research needed to assess potential effects on aquatic organisms and humans. / Department of Biology

Foodborne illnesses respresent a serious threat to health. The World Health Organisation (2000) recently passed a Resolution stating that "... foodborne illness associated with microbial pathogens, biotoxins and chemical contaminants in food present a serious threat to the health of millions of people in the world (p.1)". Overall notifications of foodborne illness and food poisoning have risen significantly and many outbreaks have been associated with the food industry. The Hospitality and Catering industry is of special concern because of it's size, diversity, individual characteristics, and direct interface with customers. This thesis focuses upon the Hospitality and Catering industry in Wales, a largely unexplored area of research. It applies an investigate approach to issues relating to the management and implementation of food safety in the industry across a range of industry sectors to be found in the Principality. Information was gathered by utlising a range of secondary and primary sources. Data collection instruments included questionnaires, structured interviews, and audit checklists and observations. These were administered by way of three discrete but interlinked primary data collection investigations. Both quantitative and qualitative data were obtained. Participating industry personnel included proprietors, managers and food handlers. Via a literature review, the key issues of knowledge, attitudes and behaviour related to food safety are discussed and evaluated within the contexts of the inherent characteristics of the Hospitality and Catering industry and food safety legislation. There three investigations are presented individually and the findings are consolidated in a synoptic discussion in relation to the Aims of the thesis. The findings indicated that within the Welsh Hospitality and Catering industry levels of knowledge and attitudes with regard to food safety and food safety legislation were variable and in some instances, unsatisfactory. In many instances, intentions to act in a positive manner towards the implementation of food safety precautions were not reflected in actual behaviour. It was further found that in establishments of all sizes and ownership categories, food handling practices were variable and in many cases, unsafe. Recommendations are made based upon the results obtained and discussed in this thesis.

With a view to establishing a model system for examining toxicity in skin, primary lingual keratinocyte cultures , a keratinocyte cell line and freshly isolated keratinocytes all derived from rat sub-lingual epithelium, were partially characterized both morphologically and enzymically and the toxicity and metabolism of the mycotoxin T-2, studied therein. A number of techniques for obtaining pure suspensions of sublingual keratinocytes (NCK) were examined and dispase is recommended for completely separating the epithelium from its dermis prior to trypsinization. Existing methods for the culture of PLK cells were improved to reduce the number of rats used and minimize the fibroblast contamination and a technique for culturing the epithelium associated with human hair follicles was also examined. The follicle technique was found to produce primary cultures which were 100% epithelial but considerable time and resources were required to generate relatively few cells. The keratinocyte cultures, PLK and RTE5, were shown to produce keratin and undergo stratification like the epithelium in vivo, Using a series of specific enzyme inhibitors, both the cultured and non-cultured epithelial cells were found to possess the same characteristic forms of acetylcholinesterase, butyrylcholinesterase and carboxylesterase. The effect of T-2 on protein synthesis in the keratinocyte cells was examined and a dose-related inhibition was evident. The primary and freshly isolated cells appeared to be the most resistant to synthesis inhibition. The rate of recovery from this inhibition was greatest in the cell line which also lost T-2 at the fastest rate. The uptake into and loss of T-2 from the keratinocyte cells was chiefly by simple diffusion, but studies using rotenone demonstrated that an active process may have been involved in reducing the rates of uptake and loss. The total amount of T-2 absorbed was likely to be dependent on the number of binding sites while the overall rate of loss was dependent on the strength of that binding. The possible nature of these binding sites is discussed. T-2 was metabolized in all the keratinocyte preparations to the same products found in mammalian skin, in vivo, and studies with specific enzyme inhibitors showed that a carboxylesterase was most likely to be involved in its hydrolysis. The greater metabolism of T-2 in the primary cells, which contained the most carboxylesterase, is likely to have been one of the factors involved in reducing the levels of protein synthesis inhibition in these cells. Rat sublingual epithelium and the cultures derived from it have a similar morphology and esterolytic capability to that of skin in viva. The PLK cells were most similar to NCK cells in terms of protein synthesis and esterolytic capability, so if it is assumed that NCK cells are representative of the sublingual epithelial cells in viva and hence skin, then the primary cultures might prove to be the best model culture system for studying toxicity in skin. Nevertheless, the RTE5 cell line was most similar to the NCK cells in respect of T-2 metabolism, and if it shown to have other characteristic skin metabolism systems then it too might prove useful for studying skin toxicity. In addition, the cell line would probably prove to be a more convenient, simpler, reproducible and cheaper means of examining skin toxicity on a large scale.