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The preparation and reactivity of a range of model systems for the low temperature oxidation of CO by gold catalysts have been investigated with a view to assessing their feasibility for bridging the 'materials gap' between well-defined single crystalline models and practical supported catalysts. The studied systems included gold powder, electrochemically oxidized gold foil, gold nanoparticles prepared on Ti02 single crystal surfaces by spin-coating and gold nanoparticles prepared on Ti02 powder by deposition-precipitation. Particular attention was paid to the reduction of oxidised gold species, since these are the common precursors in the preparation of practical nanoparticular catalysts. Oxidised gold species may also be mechanistically relevant for the catalytic low-temperature CO oxidation. A low volume reactor was designed for studies of flat gold model catalysts. It was tested with in situ X-ray absorption spectroscopy (XAS). The design of the reactor cell allows the use of further techniques including UVNis spectroscopy, X-ray differaction (XRD), Raman scattering and Infrared (IR) Spectroscopy. The reactor was also designed to permit reaction rate measurements with a mass spectrometer. In comparison to other reactors reported in the literature, this design is very cost efficient, not only in its construction but also due to its compatibility with a wide range of spectroscopic techniques. In situ X-ray photoelectron spectroscopy (XPS) on gold particles supported on Ti02 powder indicated that different atmosphere could change the morphology of the gold particles. This change is more prominent for smaller particles. The formation of graphite like spices under a CO atmosphere was observed as well. X-ray photoelectron spectroscopy (XPS) and in situ Au L-edge XAS indicated that suitable gold nanoparticles could be prepared by spin coating of tetrachloroauric acid solutions onto rutile single crystals. Gold loadings as low as 0.1 and 0.03 monolayers could be achieved. The XAS data indicated the presence of low average Au-Au coordination numbers, suggesting the presence of very small nanoparticles. XA spectra taken under CO and O2atmosphere indicated that CO interacts with the gold particles.

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The spatial distribution of lead, zinc, cadmium, copper, iron and manganese was investigated in the soils of an abandoned lead mining and smelting complex near Priddy, in the Mendip Hills, Somerset. Soils were collected at 0-200 mm and 200-400 mm depths over the period February 1995 to April 1997. The study area was shown to be one of the most intensely Ph-enriched historic mining and smelting sites on a regional and national level. The concentration of Pb in the soils of the study area ranged from 1 394 to 138 800 J.lg g-1 at 0-200 mm, and from 180 to 171 688 J.lg g-1 at 200 to 400 mm. The concentration of Zn ranged from 28 to 10 349 J..tg g-1 at 0-200 mm, and from 36 to 8 089 J..tg g-1 at 200 to 400 mm. The concentration of Cd ranged from 1 to 12 J.lg g-1 at 0-200 mm, and from 1 to 1 1 J.lg g-1 at 200 to 400 mm. The concentration of Cu ranged from 7 to 182 J..tg g-1 at 0-200 mm, and from 5 to 206 J..tg g-1 at 200 to 400 mm. The concentration of Fe ranged from 5 060 to 59 754 J.lg g-1 at 0-200 mm, and from 10 465 to 67 035 J..tg g-1 at 200 to 400 mm. The concentration of Mn ranged from 2 500 to 3 769 J..tg g-1 at 0-200 mm, and from 66 to 3690 J..tg g-1 at 200 to 400 mm. The greatest concentrations ofPb, Zn, Cd, Cu, Fe and Mn were present in the study area in the wastes associated with the beneficiation processes carried out during the final stage of the Mendip lead industry ( 1857 -1908), when the wastes of Roman and Mediaeval operations were reworked. While most of the wastes from 1857-1908 were present as clearly identifiable tailings piles, previously unrecognised areas contaminated by beneficiation w;istes were identified. Based on the Greater London Council Contamination classification, 88.5% of the soil samples in the study area were contaminated to unusually heavily contaminated by Pb. Unusually heavy contamination by Pb was present in 44% of the soils (>10 000 J..tg g-1), and by Zn in 15% of the soils (>5 000 J..tg g-1). A ranking of the percentage of samples classified as contaminated showed that in terms of magnitude of contamination, the decreasing order for the study area was Pb>Zn>Cd>Mn>Cu. The five soil types present in the study site were identified as the Maesbury, Thrupe, Ashen and Nordrach Series and Tailings, the wastes associated with beneficiation processes. Representative soils of the five types at 0-200 mm and 200-400 mm depths were collected and analysed each month between September 1998 and August 1999 to assess the temporal variation in Pb, Zn, Cd, Cu, Fe and Mn concentration. The general trend for Pb, Zn, Cu, Fe and Mn in the Maesbury and Thrupe soils and the Tailings was an overall decrease in concentration over the sampling period. The concentration of soil Pb, Zn and surface Cu also decreased in the Ashen soil , and Pb, Fe and surface Cu in the Nordrach soil. A ranking o f the soil series by % Coefficient of Variance (% CV) in trace metal concentrations at 0-400 mm showed that the degree of variation ranged from 31% C V in the Maesbury series to 11.32% CV in the Nordrach Series, in the following order of magnitude : Maesbury>Ashen> Thrupe>Tailings>Nordrach. Variation in soil trace metal concentrations by % CV for all soil series in the surface horizons showed that the degree of variation ranged from 8.41% CV for Mn to 11.97% C V for Fe in the following order : Mn>Zn>Cd>Pb>Cu>Fe. The variation in soil trace metal concentrations by % C V for all soil series at depth showed that the degree o f variation ranged from 22.52% CV for C u to 14.05% C V for Fe i n the following order : Cu>Cd>Zn>Mn>Pb>Fe. When expressed as a percentage of the Total trace metal concentration, the percentage o f EDT A extractable metals were consistently higher in the surface horizons than at depth. The variation was thought to be related to the source of enrichment, the fraction of soil the trace metals were held in, soil pH and hydrology and the availability of trace metals in the surface horizons for plant uptake. The overall ranking of EDT A extractable trace metal concentration as a percentage of Total trace metal concentration for all soil series at both surface and depth was in the following order of magnitude : Pb>Cu>Cd>Mn>Zn.>Fe. The EDTA extractable Pb as a percentage ofthe Total Pb was remarkably high in the Thrupe, Ashen and Maesbury soils. In the surface soils, this ranged from 84% to 102%, and at depth (200-400 mm) from 65% to 101%. Possible reasons for anomalous results where EDTA extractable Pb as a percentage of Total Pb apparently exceeded 100% were discussed. In the Nordrach Series, EDTA extractable Pb ranged from 49% to 81% of Total Pb in the surface soil and from 52% to 69% of Total Pb at depth. The EDTA extractable Pb as a percentage of the Total Pb was lowest in Tailings at 20% to 41% at the surface to 14% to 38% at depth. The high EDTA extractability ofPb in the Thrupe, Ashen and Maesbury soils was thought to be related to the source of enrichment, the soil pH, soil redox reactions, mineral composition and texture and soil hydrology.

Unresolved complex mixtures (UCMs) of aromatic hydrocarbons have been found in a wide range of environmental matrices at high concentrations. However, limited consideration has been given to the potential detrimental effects of the accumulation of these compounds in the marine environment. In particular, there is a need to evaluate these compounds in the light of recent evidence that points to the long term effects of oil in the marine environment. The overall aim of this work was therefore to investigate unresolved complex mixtures of aromatic hydrocarbons in the marine environment with particular emphasis on assessment of toxicity, aqueous solubility and photodegradation behaviour. A previously established link between the reduced Scope for Growth (SFG) of mussels with the concentration of 2-3 ringed aromatic hydrocarbons in mussels from petroleum impacted sites was found also to correlate well with concentrations of aromatic hydrocarbon UCMs in mussel tissues found at the same sites. This suggests that aromatic hydrocarbon UCMs or components within may be responsible for the observed effects. To determine whether an aromatic hydrocarbon UCM was capable of eliciting a toxic response in mussels, a monoaromatic UCM was isolated from a Gullfaks (North Sea) produced crude oil. At the highest nominal aqueous concentration tested, mussel feeding rate was reduced by -40 % in the 24 hour exposure period, during which the mussels accumulated a body burden similar to the body burden of monoaromatic UCM hydrocarbons in wild mussel populations, previously shown to exhibit reduced SFG. Recent studies of hydrocarbon UCM composition using chemical degradation methods have led to the proposition of alkylcyclohexyltetralins as 'average' structures for some monoaromatic UCM hydrocarbons. The aromatic hydrocarbon 7-cyclohexyl-lmethyltetralin was synthesised herein in good yield and purity. This compound reduced mussel feeding rate by 50% during the 24-hour exposure period. The aqueous solubility of a compound is an important physicochemical parameter that influences behaviour within the marine environment and is thought to be a limiting factor in the onset of measurable toxicological response. The aqueous solubilities of three 'model' aromatic UCM hydrocarbons were determined in distilled water at 25°C using a generator column set-up. The effects of salinity and temperature on aqueous solubility were also investigated. An aqueous solution comprising an aromatic UCM was also generated. Another influence on the fate of aromatic hydrocarbons in the environment is the action of sunlight (phototransformation). Therefore aqueous solutions of three model aromatic UCM hydrocarbons were exposed to light simulated under environmental conditions. The halflives of these compounds suggested that if these compounds are indeed representative of the aromatic UCM phototransformation may influence its fate in the marine environment. The results of this study have furthered knowledge on the environmental behaviour of unresolved aromatic hydrocarbons, and suggest that these compounds should be considered in the long term impacts of oil in the environment and also warrant further study. Parts of this work have been published and the author (Smith, E. L. ) was awarded the Procter and Gamble Eurorcar prize at the 3'd World Congress of the Society of Environmental Toxicology and Chemistry, 21-25 May 2000, Brighton, for the best presentation by a young scientist.

The studies reported herein cover two main areas of research. The distribution of lead through the plant has been monitored using histochemical and quantitative techniques, and physiological responses of the plant to lead contamination have been examined. In seeds the testa prevents lead contamination of the embryo prior to germination. In seedlings root-applied lead is capable of essentially unrestricted movement through the plant, although anomalies in distribution exist. The metal is sequestered during its passage through the plant, and the endodermis offers a partial barrier to lead movement, restricting contamination of the aerial parts of the plant. In cotyledon leaves local accumulations may occur, causing necrotic lesions. Subcellular lead contamination again diminishes with distance from the root, but extensive exposure causes heavy contamination of cell walls, increasing wall fragility. Lead deposits occur in association with several cell organelles, but the primary response of plant cells to lead contamination lies in the formation of vesicles, apparently from the endoplasmic reticulum. These fuse into vacuoles and may totally disrupt cell ultrastructure. Lead distributions observed have been verified by X-ray microanalysis. Responses to lead pollution occur in numerous physiological processes, but the most obvious effect lies in the reduction of plant growth. In the root this is at least partially attributable to reduced cell division, but in the stem growth inhibition results primarily from interferences in cell elongation. This inhibition of elongation arises from lead-induced cell wall changes which increase wall rigidity. At high supply levels lead also influences water uptake, possibly via changes in membrane permeability. Endogenous IAA levels increase in response to lead contamination, and may partly alleviate the toxic effects of lead. The metal also promotes changes in chlorophyll synthesis, membrane permeability, ion uptake, water stress and respiration. Possible reactions and interactions involved in these responses are discussed.

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