Since mankind's adoption of fossil fuels as its primary energy carrier for heating, elec- tricity and transportation, the release of greenhouse gases into the atmosphere has increased constantly . A potential replacement energy carrier is hydrogen. Current industrial techniques for dissociating hydrogen from its common substances are con- ventionally reliant on fossil fuels and thus greenhouse gases are still released. As a mechanism to develop a hydrogen economy current industrial techniques will suffice; however, a long-term sustainable solution to hydrogen mass production that does not release greenhouses gases is desired. The United States of America Government be- lieves that the Sulphur-Iodine thermochemical hydrogen production cycle, thermally powered by a nuclear source, is the most likely long-term solution. A critical part of the Sulphur-Iodine cycle is the point of interaction between the thermal source and sulphuric acid used within the cycle. A novel bayonet heat exchanger made from silicon carbide is theoretically applied to the point of interaction. Through a combination of experiments and theoretical modelling, the bayonet heat exchanger is characterised. The bayonet model is then modified to simulate the intended nuclear reactor favoured by the United States Department of Energy. In addition, the bayo- net heat exchanger is analysed for a solar thermal application. An advanced design of the bayonet is also presented and theoretically analysed for its increased thermal efficiency.

The disruption of physiological and morphological aspects of osmoregulatory processes in freshwater-adapted 0-group European flounders, Platichthys flesus (L.), caused by exposure to environmental concentrations (150 ng triorganotin g"1 dry weight sediment) of sediment-associated tri-o-butyltin chloride (TBTCl) and triphenyltin chloride (TPhTCl), was examined and quantified. Radiotracers were used to measure hydromineral fluxes, the water balance and passive sodium efflux of chronically (35 days) exposed fish. The water permeabilities of exposed flounders varied during the course of the experiment and were significantly lower than the corresponding controls, that did not change significantly with time. It was found that the maximum change in water permeability of TBTCl- and TPhTClexposed fish occurred after 14 days and 21 days, respectively; thereafter there was an increase towards control values, suggesting adaptation to compensate for the effects of the organotin exposure. Drinking rates increased significantly in both organotin groups but urine production rates did not change. The effects of organotin exposure on the passive sodium efflux and Na+/K+-ATPase activity showed an inverted relationship in the TBT group, where the Na7K+-ATPase activity was reduced and the passive sodium efflux was increased. TPhT had no inhibitory effect on Na7K+-ATPase activity and the passive sodium efflux increased only gradually. The overall effect of these changes in these components of hydromineral regulation was to reduce the mean blood osmolalities of the organotin groups compared to the control values. The effects of chronic exposure to sediment-associated triorganotin compounds during sea water adaptation was examined and quantified by measuring the active sodium efflux, Na+/K+-ATPase activity and structural changes to the gill epithelium usually encountered in euryhaline fish during adaptation to sea water. Following the transfer to sea water, the Na+/K+-ATPase activity and the active sodium efflux were decreased in the TBT group but increased significantly in both the TPhT and control groups. Similarly, the morphological changes to the gill epithelium, involving chloride cell distribution, associated with sea water adaptation, took place in the control group and only partially in the TPhT group but were significantly inhibited or delayed in the TBT group. The exposure to organotin caused the mean blood osmolalities in fish of the TBT and TPhT to rise beyond the expected values that were observed in the control group. The results presented in this study lead to the conclusion that tri-tt-butyltin chloride and triphenyltin chloride in sediments are capable of significantly disrupting both the physiological as well as morphological components of osmoregulatory functions of an estuarine fish, at concentrations currently found in local sediments.

In the UK, the domestic sector accounts for around 30% of fuel-use and energy related carbon emissions, and therefore has the potential to deliver significant reductions in carbon dioxide emissions. The purpose of this work is to form and examine various heat and electricity supply scenarios at the street-level and identify which of these scenarios offer the most potential to reduce consumption of resources and carbon dioxide emissions. The path to realisation of a reduction in carbon emissions from the domestic sector incorporates three consecutive steps: (1) saving energy, (2) use of renewables and (3) use energy as efficiently as possible, including fossil fuels. In reality, there is a strong interaction between all three steps and often they take place simultaneously. The first two steps tend to minimise the use of fossil fuels, but not to eliminate them. In this work it is recognised that in mature urban regions fossil fuels cannot be readily displaced completely, but can be used in a more efficient way. This research considers what can be achieved by applying at or near to market technologies at the street level microgrid scale, such as Combined Heat and Power (CHP). The renewable energy technologies considered were photovoltaics (PV) for electricity generation, solar thermal for domestic hot water heating and ground source heat pumps (GSHP) for space heating. For the development of the models, the transient simulation package TRNSYS was used and a residential area in Southampton that represents a typical UK area, was chosen as a case study. The notion of combining a number of houses to form a local microgrid proved to be beneficial for all the technologies examined in this research. It was shown that renewable energy microtechnologies can improve their carbon performance up to 10% when operating as a microgrid, whilst estimated benefits were even greater for CHP systems. Parallel operation strategies were also investigated and it was shown that they have the potential to deliver further savings from microgrid schemes. Microgrids, although their high capital costs, were estimated to have better financial performance compared with the single house level for many of the cases examined. Increased generation and lower heating demand were the key outcomes due to the impact of change in climate

Poor salmonid spawning habitat due to excessive fine sediment inputs has been identified as a major factor limiting survival in chalk rivers. A lack of knowledge about the complex processes and factors affecting survival was the driver for this study and gaps in the research were identified concerning the sources of fine sediment and the impact organic material had on salmonid survival in chalk streams. Consequently the main objectives of this study were to characterise spawning habitat quality of a chalk catchment, assess the sources of sediments accumulating within artificial redds, describe the composition of organic sediments using emerging technology and to create a novel method to assess the sediment oxygen consumption of those sediments. Methods were based around a catchment wide field based monitoring programme, consisting of artificially constructed spawning gravels which allowed hyporheic measurements to be taken, and sediment analysis and sediment oxygen consumption methods were carried out using different laboratory methods. Spawning habitat characteristics of the chalk catchment were found to exhibit; low sediment accumulation rates although original levels of fine sediment were high, high organic matter content, variable intra-gravel flow and intra-gravel oxygen concentrations and groundwater influences. Primary sources of fine sediment accumulating in spawning gravels and suspended sediments were found to be attributed to catchment surface sources, namely pasture (50-68%) and arable (32-50%) using inorganic and organic parameters. Organic composition of redd gravels was found to be dominated by protein material rather than humic substances, the more commonly found fluorescent compound in freshwater systems and the sediment oxygen consumption of sediments varied throughout the catchment and was found to consume the greatest oxygen in <63μm size fraction. Application of sediment oxygen consumption rates to existing parameter based models that predict salmonid survival, highlighted the need to address the sensitivity of current models to rivers experiencing low sediment accumulation rates. Outcomes of this study further the knowledge of the sources, organic composition and sediment oxygen consumption capacity of fine sediments accumulating in spawning gravels which can lead to appropriate mitigation on chalk rivers to improve salmonid spawning habitat.

Anthropogenic use of waterways is reducing connectivity at a rate faster than any time in geological history, sometimes causing serious declines in fish populations. Free passage of fish throughout the watercourse is necessary for species utilising different habitats for e.g. residing, spawning and feeding. Fish passes are employed to mitigate for impoundments, but are historically biased in design towards upstream migrating salmonids. Driven partly by more holistic environmental legislation, there is now an increasing interest in other species and life-stages, requiring development of fish passage criteria for multiple species during up- and down-stream migrations. To address these knowledge gaps this research programme undertook laboratory experiments with upstream migrant river lamprey, Lampetra fluviatilis, and downstream migrating European eel, Anguilla anguilla, and brown trout, Salmo trutta. The use of a large open-channel flume allowed control of the motivational state of, and stimuli encountered by the fish. The fish responses to a variety of model weirs and screens placed in the flume were assessed, allowing attainment of species and life-stage specific swimming capability and behavioural information. This research demonstrated that using large flumes where volitional swimming allows natural compensatory behaviours to be undertaken, provides more realistic swimming capability information for fish pass criteria than some traditional methods (i.e. confined swim chambers). Dependent on species and direction of movement, all structures tested had some level of impediment to migration, with small gauging weirs almost completely impeding movement of upstream migrant river lamprey under the conditions presented. Downstream migrant anguilliforms were seen to demonstrate structure oriented, thigmotactic behaviour compared to salmonids which responded to flow fields. Under high velocities, this lack of reaction to hydraulic cues may result in a higher probability of damage and mortality at facilities traditionally designed to protect salmonids. The information provided by this research, e.g. accurate swimming speeds and fish response to associated hydraulic conditions, will aid the production of effective multi-species fish pass facilities

Coastal defences reduce sediment input and modify the sediment budget, usually resulting in a sediment deficit down-drift and an accumulation up-drift. This process results in set-back adjacent to defences. Three types of set-back were identified and these occur due to the: • terminal groyne effect, where defences stop or dramatically reduce erosion, induce a sediment deficit down-drift and cause an increase in retreat rate; • perceived terminal groyne effect, where defences stop or dramatically reduce erosion, and down-drift retreat rates remain the same or decrease; • initial groyne effect, where defences stop or dramatically reduce erosion, induce sediment accumulation up-drift and cause a decrease in retreat rate. Set-backs are found on defended coasts world-wide, and are complex evolving features dependent on numerous natural and anthropogenic factors. 200 set-back sites were identified in England and Wales, half on cliffed coasts. The terminal groyne effect theory was investigated on 17 sites on the soft cliffs of Holderness, Christchurch Bay and north-east Norfolk, UK, all of which erode naturally at 0.5m/yr-2.0m/yr. Historical shoreline analysis and a history of human intervention was undertaken for each study region and site. For 13 out of the 17 case studies, a terminal groyne effect appeared to have occurred. As time passed and the magnitude of set-back increased, the terminal groyne effect became increasingly apparent. Where increased retreat resulted, the coast was affected for tens to thousands of metres down-drift. For the remaining case studies, a perceived terminal groyne effect occurred. An initial terminal groyne effect occurred at all sites. Longshore, the continued set-back caused outflanking of defences prompting emergency works, such as repeated defence extensions up and down-drift. Over several decades of set-back, the defences formed an artificial headland and created a crenulate shaped embayment down-drift. The planform of an embayment expanded rapidly, then reduced to a steadier retreat rate. As shoreline management evolves from a highly defended to a less heavily managed coast, defence abandonment will result in rapid retreat. Set-backs may be created due to the juxtaposition of maintained and abandoned defences, as illustrated at Happisburgh, Norfolk. In the coming decades, set-backs, artificial headlands and the terminal groyne effect will remain important issues for shoreline management.

Landfill leachates contain a wide range of pollutants including potentially toxic metal(loids) e.g. arsenic. Current landfill risk assessment models predict the fate and transport of these pollutants in the environment, however they consider all species below 0.45 μm to be dissolved, thus the presence of these pollutants in colloidal form is not considered. In order to investigate the presence and distribution of metal(loids) within the nanocolloidal fraction (<100 nm), AF4 coupled with HR-ICP-MS was selected (alongside AFM and DLS) and optimised for use with landfill leachates. UV254 and Fluorescence spectroscopy were also used as detectors for AF4 to detect organic colloids. AF4-HR-ICP-MS analysis was carried out both offline (fraction collecting and subsequent HR-ICP-MS analysis) and online (interfacing the AF4 output directly with the HR-ICP-MS) with parameters optimised for lower MW particles. Online coupling provided a higher resolution analysis than the offline method. The concentration of elements within the AF4 system was found to be in flux and therefore baseline concentrations were established for each sample injection. Method repeatability and a recovery mass balance of each element were also established. The method was validated by fractionation of a MSW, an aged MSW and a MBT leachate. All three leachates were found to show the same nanocolloidal distribution with two distinct nanocolloid populations present: a low MW organic rich fraction; and a larger, less organic rich fraction consisting of a mixture of organic and inorganic particles. Metals predominated in the lower MW fraction associated with humic or fulvic-like particles. The similarities between the leachate metal distributions showed that treatment of leachate prior to landfill did not alter the colloidal characteristics. Preliminary results examining the effects of pH and ionic strength of metal distribution showed that pH had no effect; however the lowering of ionic strength appeared to cause aggregation of colloidal Fe particles, presumably due to the lower organic content, which appears to control the distribution of metals in this size fraction. This research highlights the importance for landfill risk assessments to be updated to include the presence of colloidal facilitated transport and the necessity for further particle transport studies to be conducted.

The work investigates if fly ash from Ekibatuz Power Plant can stabilise low concentrations of mercury in the environment and prevent it from becoming soluble in water and in preventing it transforming into the methylated form. The work demonstrates that mercury bound to fly ash from the coal fired 4,000 Mwatt Ekibatuz Power Plant in Kazakhstan is fairly stable at pH levels that are found in most natural water bodies. The adsorption behavior followed the Freundlich adsorption model. The adsorption capacity of the fly ash for Hg (II) was found to be 3.0 mg.g-1 of dry ash, the adsorption equilibrium being reached after 96 hours. The adsorption kinetic and studied at pHs between 6 and 8. The study showed that between the pH range of 6.0 and 8.0 bound mercury on wet and air dried ash was fairly resistant to leaching with the maximum leaching being 0.292 mg.l-1 and 0.14 mg.l-1 for the wet and air dried fly ash, respectively, with leachate at pH 7.0. Laboratory studies of the stability of the adsorbed mercury on fly ash when mixed with organic rich sediments in an anaerobic environment at pH 7.0 showed that despite ideal conditions for methylation to take place after 8 weeks, the concentration in solution was less than 2 μg.l-1. The studies showed that unburnt carbon contained in raw fly ash was the key factor for adsorption reaction. The results indicated that fly ash from the 4,000 Mwatt Ekibatuz Power Plant in Kazakhstan fired with high ash medium volatile coal can be used to stabilise low concentration of mercury in the natural aquatic environment

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