Changes to the visual character of the landscape can become a key issue capable of influencing the outcome of an Environmental Impact Assessment (EIA). These changes are commonly referred to as visual impact, and it is recognised, unlike many other aspects of EIAs, that Visual Impact Assessment (VIA) relies less upon measurement than upon experience and judgement (IEATLI, 1995). Currently, there are very few quantitative techniques for the evaluation of visibility and it is mostly assessed qualitatively since it is concerned with the human appreciation of the landscape (Zewe and Koglin, 1995 and Wherrett, 2002). The main problem with qualitative techniques in assessing visual impact is that they may lead to bias due to their inherent subjectivity, hence there is a need for a more structured and consistent approach towards VIA. To reduce the subjectivity currently associated with VIAs, new quantitative techniques have been developed and existing spatial and qualitative techniques have been improved upon. The techniques developed in this research use Computer Graphics (CG) technology, including the field of Virtual Reality (VR). A quantitative method to calculate percentage view change has been developed that allows the accurate determination of the variation in any view, caused by an existing or proposed development. The method uses three dimensional (3D) CG models of an environment and software that has been developed using a scripting language from a 3D modelling software package. A new method has also been developed to create Fields of Visual Influence (FVIs) using standard 3D modelling techniques. The method improves upon the accuracy and efficiency of existing FVI techniques. A novel VR simulation technique has also been developed that attempts to reduce the subjectivity associated with simulations, by integrating quantitative and spatial techniques.

Photocatalytic NO decomposition and reduction reactions, using CO as a reducing gas, have been investigated over Ti02, Ag-Ti02 and Rh-Ti02 photocatalysts, using a purpose built continuous flow photoreactor. The transition metal modified Ti02 photocatalysts were prepared using wet impregnation techniques, and the effect of thermal processing parameters on their photocatalytic behaviour was studied. Prepared photocatalysts were characterised using a number of complementary techniques, including XRD, TEM, DSC, and XPS. The findings from these techniques were used to explain the observed photocatalytic properties. The activity and selectivity of the photocatalysts were found to be dependant on a number of factors; thermal pretreatment temperature, type and amount of the modifying element, chemical nature of the modifying element and the reaction conditions used. It was found, for Ti02 photocatalysts, that increasing the pretreatment calcination temperature resulted in lower NO conversion rates, due to removal of surface bound hydroxyl groups. A similar trend was observed for Ag-P25 photocatalysts, but the reduction in activity was greater due to the presence of larger silver clusters, which acted as recombination centres for photogenerated electron-hole pairs. The activity of the Ag-P25 photocatalysts decreased as the silver loadings increased, whilst the activity of the Rh-P25 photocatalysts remained largely unaffected by the metal concentration. Over Ti02 and Ag-Ti02 systems, the NO conversion rate was lower for the reduction reactions compared to decomposition reactions. This was attributed to the preferential adsorption of the CO molecules, blocking NO adsorption sites. Contrasting behaviour was observed over Rh-P25 systems and NO conversions as high as 87 % were recorded in the presence of CO. Silver modified catalysts were highly selective for N2 formation (90 %) whilst rhodium modified catalysts were more selective for N20 formation. These results are discussed with respect to the possible surface reactions and the chemical intermediates that may be formed.

In areas where heavy metals are introduced into or onto land where they would not normally be present at elevated concentrations, then that land could be considered to be contaminated. A simple way of determining the magnitude of contamination by heavy metals is to measure the total metal concentration in the soil. However, this simple measure is a poor way of assessing the potential risks to the environment and human health. A more effective risk assessment can be achieved by analysing the proportion of the total metal that exists in a mobile or bioavailable form, in other words, the metal solubility. Unfortunately metal solubility is more difficult and costly to measure than total metal concentration in the soil. This thesis examines the application of a metal solubility model to geochemical survey data consisting of pH and metal concentrations. The solubility predictions were interpolated in order to produce maps; however, the interpolated data had very high uncertainties. Further analysis showed that pH was the greatest source of uncertainty in the algorithm, contributing the most for lead, with 76% of the uncertainty being due to pH. pH was least influential for copper, contributing 49% of the uncertainty, but pH was the highest contributor in each metal. In order to examine the accuracy of the algorithm without geostatistical influences, a field work study was undertaken to measure metal solubility directly at the original survey sites. This showed that the algorithm was very good at predicting metal solubility at point sources. In order to assess the shortscale spatial variability of pH, and the errors in pH measurements, a second field work project was conducted, measuring the pH on 200 samples from a single field. This work showed that pH does vary across a field, but more importantly allowed a quantification of the uncertainty involved in sampling and measuring pH. Results show that despite the short-scale variability in pH, point predictions are accurate (the average difference between measured and predicted pZn2+ is 6%), xvi and might be of use to land managers. However, interpolating solubility predictions for mapping produces unacceptably high uncertainties (mean values were 188% for Pb, 417% for Cu and 153% for Zn) for land management or the development of policy measures related to soil. Further work could include calculating the measured Pb and Cu solubility and comparing these to the predictions. A study to investigate how pH and Zn2+ vary together across a field would also be of interest.

Using a dual approach of wind tunnel experimentation and the development of an analytical model, the dispersion of pollutants from road vehicles has been investigated. A series of novel tests were conducted in an environmental wind tunnel which looked at the dispersion of propane in the wake of a 1=50th scale model of a lorry which was fired across the wind tunnel using a special rig. Time histories of concentration and air flow were taken as the lorry sped across the tunnel. Two experimental scenarios were investigated. The first, a simulation of a typical rural boundary layer, confirmed the existence of a wake behind the moving lorry. Concentration measurements revealed that the dispersion was largely Gaussian in nature and that at low cross wind speeds the vehicle-induced turbulence was the dominant mixing effect. Measurements were taken as the lorry passed along a model of an idealized urban street canyon. Time histories for individual firings exhibited two peaks as the propane was swept around the canyon in the resident vortex. Ensemble averages of several firings allowed a quantitative assessment of the rate of dispersal from the canyon to be made. A computer model has been developed which predicts the dispersion of vehicular pollutants in both the rural and the urban street canyon environments. The model, based around the Gaussian Puff Method, extends the range of applicability of earlier models in several areas. It is a transient model which enables the investigation of traffic congestion and non-steady above canyon wind fields. It is also the first model to include individual vehicles as sources of both pollutant and turbulence. A detailed sensitivity study is presented, followed by an application of the model which attempts to predict probability distributions of pollutant in a street canyon. Finally, a comparison between the analytical model and the experimental program is presented which demonstrates that the model is capable of modelling a real situation to a good degree of accuracy but also demonstrates that further validation is required.

Analytical techniques applicable to the assay and remediation of cutting/mud matrices have been developed, utilising soxhlet extraction with dichloromethane and a drying agent followed by analysis using Gas Chromatography (FID). Calibration curves of oil content were produced for Novatec and Versaplus coated cuttings that were also sized by wet and dry sieving techniques, demonstrating their variable nature. The oil in each size fraction was assessed and showed that the finer fractions preferentially adsorbed the oil. Bacteria were isolated from the cuttings, muds and the pure oils to see if any indigenous species could, with optimum conditions, remediate the oil they contained. The resulting isolates were batch-tested in the laboratory in a minimal medium, with the drill cuttings providing the sole carbon source. Each isolate was scored for remediation performance, with reduction in oil varying from 50% to 6% within one week. Subsequently three bacteria (A,D & J) were identified using 16SrRNA sequencing; they were Bacillus Thuringiensls (A&D) and a novel species related to Bacillus oleronius. These were then tested slurry-phase in a rotating drum bioreactor designed and fabricated for the research against a known remediator, Rhodococcus 9737, and a non-inoculated control for four weeks. All the reactors remediated, but Rhodococcus 9737 reduced the oil to 35% of the original, A, D and other isolates as a consortium to 83% and J, 90%. Further tests in the bioreactors, after a modification to improve the air supply gave reductions of around 50% after four weeks. The high clay content of the cuttings was detrimental to significant levels of bioremediation in a slurry-phase bioreactor. Manures were added to the drill cuttings and tested in the bioreactors as a solid-phase system. These degraded the cuttings oil to 2% (v/v), a 96% reduction. Composting was thus more applicable for a high clay content drilling waste bioremediation system.

In excess of 1,000 million tyres are manufactured worldwide every year. The average tyre lasts for approximately 50,000 kilometres before it must be replaced. Each year in the UK approximately 37 million tyres reach the end of their useful life. The used tyre, which is almost identical to the replacement, then requires disposal. As the volume of road traffic increases alternative disposal routes are required to take up the resulting shortfall in capacity. SITA Tyre Recycling operate an incinerator in the West Midlands which solely burns scrap tyres. The plant receives a significant proportion of UK scrap tyre waste stream as well as reject tyres from manufacturers. The main waste stream generated is disposed to landfill. The objective of this research was to determine if the waste had potential for recycling which would reduce the burden on landfill and possibly generate revenue through the sale of products. By developing methods to sample and characterise the waste stream it was found to consist of multiple phases that could be individually treated to generate valuable products. Products based on carbon and steel were derived from the combusted rubber and bead wire respectively. Detailed examination of the carbon phase using a range of techniques revealed that many compounds used in the manufacture of the tyre rubber were highly dispersed in a carbon dominated matrix. The success of physical separation processes was limited by the difficulties associated with liberation of the valuable carbon from contaminating elements. The post-combustion steel was found to have an unacceptable sulphur concentration, which was mainly associated with surface coatings of the carbon phase. Through the application of traditional attrition scrubbing the surface coatings were removed and a reduced sulphur content steel product generated. Pilot scale trials were used to generate large samples for industrial assessment and process optimisation purposes.

This research aimed to investigate the distribution, mobility and potential bioavailability of mercury in the Medway Estuary, Kent, UK, and the impact of feeding regimes on mercury concentrations in the food web, as well as the importance of liver as a storage organ for mercury within fish. Surficial sediment mercury concentrations were typical of an industrialised estuary, ranging between 18-1302 µg kg-1 (dry weight). Three sediment hotspots contained mercury concentrations which are likely to cause adverse affects to organisms. Porewater mercury concentrations ranged between <0.01-1.75 µg L-1, and were not correlated with mercury in the solid phase. The lowest partition ratio between mercury concentrations in sediment and porewaters was observed at four locations in the mid-stream and towards the mouth of the estuary (log Kd = <2). At these locations a greater fraction of total sediment mercury (sediment plus porewater) is likely to remobilise and potentially become more bioavailable. Mercury porewater concentrations are elevated in comparison with overlying waters, suggesting a diffusive release of mercury from the bottom sediments to the water column. The calculated diffusive flux was 6 kg year-1, demonstrating that mercury is mobile in this system. Mercury in sediment core samples ranged between 382-1888 µg kg-1 (dry weight). Dredging the Medway would release mercury from these more contaminated deeper sediments into overlying water, thus having potentially ecotoxic consequences. Within the cores, methylmercury concentrations ranged between 0.3-0.8 µg kg-1 (dry weight) and organomercury ranged between 2-48 µg kg-1 (dry weight). Mercury concentrations in fish flesh ranged between 0.01-0.63 mg kg-1 (wet weight), with all specimens being within the EU limit for human consumption.

This research presents the development of CityZoom UP, the first attempt to extend existing urban planning software in order to assist in modelling urban scenarios and setting up simulation parameters for Gaussian dispersion and CFD models. Based on the previous capabilities and graphic user interfaces of CityZoom to model and validate urban scenarios based on Master Plan regulations, new graphic user interfaces, automatic mesh generation and data conversion algorithms have been created to seamlessly generate input data for dispersion model AERMOD and CFD packages CFX and OpenFOAM. A key feature of CityZoom UP is the introduction of vehicular pollution source parameters in dispersion and CFD models, allowing the urban designer to assess the local impact of adding or modifying a building or group of buildings on the street air quality. Traffic emissions are modelled as sequence of point sources. CityZoom UP uses Atmospheric Dispersion model AERMOD to assess the dispersion of pollutants in large scale urban environments for strategic planning, quickly providing results for different alternatives of urban scenarios, meteorological and traffic profiles. Sensitivity and validation tests are performed and the results are compared to wind tunnel and real world tracer experiments from the DAPPLE campaign. For the first time in the available literature AERMOD is used to perform dispersion simulation using tracer emission data from mobile vehicular sources in a complex urban scenario, considering building wake effects. CityZoom UP also provides automated 3D meshing, including mesh refinement, identification of physical boundaries in the mesh, and automatic setup of CFD simulations of urban scenarios, for the detailed calculation of air flow and dispersion of pollutants in specific areas inserted in urban environments. These capabilities can greatly reduces the time necessary for the setup CFD cases, even if it does not affect the computational time needed to run the CFD simulations. Tests show how CityZoom UP can be used to model alternative scenarios for a given location, e.g. present situation and future scenario including a new tall building, and to easily automate the generation of different meshes for each scenario, based on boundary layer and size function refinement parameters. The present and possible future situations of a real world scenario in Porto Alegre are modelled as a show case for CityZoom UP. The capabilities to assist in modelling alternative urban scenarios and setting up AERMOD and CFD simulations based on those scenarios is demonstrated.

A method to treat contaminated land is stabilisation/solidification (S/S), which physically encapsulates and chemically stabilises the contaminants. The current knowledge on the behaviour of S/S systems is based upon scarce and incomplete data, mostly obtained from laboratory simulations or small scale trials of the technology. The field performance of S/S soils is largely unknown. The aim of this research was to improve the understanding of the long-term performance of S/S soils, by examining samples retrieved from eight full-scale remedial operations. The sites were selected to encompass a broad range of contaminants, binder systems, environmental exposures, and ages since the remediation. Conceptual models for each site were developed, based upon historical information from the literature. The models were used to identify the environmental loads, acting at the sites, and to predict their likely impact on the S/S soils. These impacts were considered by examining the microstructure, mineralogy, leaching behaviours and mechanical properties of the aged soils. Risk indicators for the performance of S/S soils were identified and they included reactions involving sulfates, carbonation, microcracking and the presence of weathered minerals. There was no link between the age of the S/S soils and degradation. The performance of the S/S soils was site specific and was influenced by the design of the remediation formulation, the implementation of the treatment and not least the environment of exposure. The behaviour of S/S soils is commonly compared to that of concrete. However, whilst the results suggested that some degradation mechanisms occur, properties such as permeability and unconfined compressive strength differed. The S/S soils were two orders of magnitude weaker and five orders of magnitude more permeable than normal concretes. Microstructural investigations revealed that although expansive phases developed with time in the SIS soils, there was no damage associated with them. According to their mechanical properties seven out of eight soils performed to their design criteria, up to 16 years after remediation. However, three sites failed to meet the limits following pass/fail leaching tests. This was due in part to the choice of leaching test carried out for the evaluation and the use of inappropriate remedial leaching limits, such as Drinking Water Quality values. However, the pH dependent leaching test showed that the contaminants were well immobilised in the old SIS soils and their release, at the natural pH of these soils did not exceed 1 mg/1. The acid resistance of the aged SIS soil was low to moderate and was mainly assured by the carbonates present. This fact will impact on the durability of SIS soils; however, estimates from the literature indicate that the acid resistance of carbonated materials would be exhausted in thousands of years. Based upon these results, the integrity of the soils had endured, and no obvious signs of impending failure were observed.

Accelerated carbonation involves exposing a material to a concentrated atmosphere of carbon dioxide, and can be used to treat hazardous wastes and soils and create new construction materials. The present work examines the use of accelerated carbonation to reduce the hazardous properties of wastes as a means of reducing the costs of disposal to landfill, and then develops the process to manufacture aggregate from the waste removing it from landfill disposal completely . A range of thermal wastes, including those from cement, metallurgical and paper processes, were found to be reactive with carbon dioxide. Many of these wastes are hazardous on account of their alkaline pH, which carbonation partially neutralizes, effectively allowing reclassification of the materials as stable non-reactive hazardous wastes under the Landfill Regulations. Cement and paper wastes were highly reactive with carbon dioxide, and were considered for use as cement substitutes to reconstitute non-reactive wastes into aggregate. Previous work had suggested that carbonation and pelletising were not compatible due to differing optimum conditions. This issue was investigated by considering the effects of the mix formulations and machinery parameters. The pelletising and carbonation processes require widely different moisture contents. The disparity is due to the need for total saturation of the material to form bonds between grains during pelletising, and an open pore network for carbon dioxide to penetrate. To achieve the two simultaneously, several methods were investigated. Chemical catalysts including sodium hypochlorite and sodium sulfite increased carbonation in a saturated material. However, curing the formed aggregates in carbon dioxide was found to be the most economic solution. A pilot scale process was developed based upon the laboratory results. A bespoke rotary carbonation reactor was developed to produce aggregate in bulk for commercial testing. Aggregate which was subjected to accelerated carbonation, has enhanced strength and durability compared to aggregate exposed to natural carbonation. The aggregate was successfully used to produce lightweight concrete with comparable strength to concrete made from commercial lightweight aggregate. Aggregate was also supplied for a research project to investigate the use of recycled materials as a horticultural growing medium.