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The research reports on the potential for CO2 pressurisation as a means of enhancing biogas production in the anaerobic digestion of co-settled sewage sludge, a technique reported in the commercial literature as showing great benefits. The possibility of using this technique to reduce the number of faecal indicator bacteria is also explored, as an alternative means of complying with the UK water industry's Safe Sludge Matrix. Initial research using pure cultures of both E. coli (a strain isolated from sewage sludge) and Salmonella enterica showed that the results from different methods for isolating, recovering, resuscitating and enumerating E. coli were comparable. Further testing using heat stressed and unstressed E. coli showed the advantages of resuscitation and the MPN technique with 2-stage incubation was therefore used in the experiments to maximise the recovery of damaged but viable cells. The results for pure cultures showed conclusively that under the conditions of time and pressure used CO2 pressurisation and rapid depressurisation could cause irreversible cell damage and loss of viability in both test strains. The effect was reproducible and a time-pressure relationship was established for the apparatus used. It was shown, however, that the sanitising effect was influenced by culture volume, probably as this affected mass transfer of CO2 and hence its penetration into the cells. This finding may limit the practical application of the approach and further work is needed to establish design parameters and develop reactor systems to overcome this issue. Even under the favourable conditions used, exposure times required for 6 log reduction were too long for commercial application. Optimisation of the pressurisation vessel design may improve this and should be a focus of any future investigations. Batch and semi-continuous anaerobic digestion tests with co-settled sewage sludge were carried out to ascertain the effect of pressurised CO2 treatment on biogas production. These showed conclusively that the treatment did not improve either biogas productivity or specific methane yield. Experimental work also showed that even treatment conditions which gave an 8 log reduction in E. coli in pure culture were ineffective in reducing the number of indigenous E. coli in the sludge, or of S. enterica when added to a sewage sludge matrix. These findings led to further investigation of the effects of the size of pressure vessel and sample used. The results showed that this was an important factor, but could not fully explain the lack of performance in comparison with pure culture. It was concluded that the sludge matrix itself must play a role in protecting the microbial consortia from the effects of pressurised CO2. The exact reasons for this were not discovered but may be due to the effect of dissolved compounds present in the sludge and/or the structure and nature of the sludge flocs themselves.

Many of the great challenges of our age are ultimately challenges of complexity. Anthropogenic climate change threatens to destabilise the ecological connections that span the biosphere as well as the delicate geopolitical functioning of our globalised civilisation. It seems a push towards developing an understanding of the seemingly unpredictable behaviour of such highly connected complex systems could hardly come at a more critical time. It is the spontaneous emergence of macroscopic phenomena from these complex systems that forms the core of this thesis. Complexity generally results from the multiplicity of system components and is ubiquitous in natural systems. Developing an understanding of how macroscopic structures emerge from microscopic dynamics is central to furthering our understanding of complex systems. However, there exists a gulf between our capacity to formulate complex models and our ability to predict their behaviour. Additionally, large and complicated models require vast computational resources and will remain out of reach for many years, even when considering Moore's law, the observation that the increase of computing power is approximately exponential with time. This thesis contributes to building the bridge between model formulation and prediction with multiple directions of attack. We begin by analysing Watson and Lovelock's (1983) Daisyworld model by making explicit the relationship between the various model time scales, laying the foundation for our own conceptual ecosystem model with an arbitrarily diverse biota and a multidimensional environment. We make the important step of providing a framework to translate the model formulation and determine the collective behaviour of the biota. Cellular automata and networks are methods for modelling discrete complex systems and are widely considered a staple of the complex systems simulator's toolbox. We go on to develop the analytical tools available to these models with a real space renormalisation of two dimensional non-equilibrium cellular automata along with demonstrating the utility of a master equation approach by analysing the properties of a new algorithm for growing complex networks. Lastly we investigate the utility of thermodynamic principles in predicting self-organisation in dissipative systems.

When oil and gas pipelines cross rivers they are often buried in the ground beneath the floodplain and river bed. There is a risk that river will expose the pipe by lateral bank erosion, as well as bed erosion, and then there is a risk that the pipe will break. Pipe failure can cause loss of revenue, repair and reparation costs, political difficulties and adverse environmental impacts. Buried pipeline crossings correctly located and engineered do not affect the flow hydraulics and river regime. Therefore, pipeline crossing projects should be based on the study of natural processes including those which lead to lateral movement of the channel. This study deals with the scientific knowledge of a variety of channel types and their evolution by lateral movements. The literature review and statistical analysis reveal that the rates of bank erosion depend on the type of river channel pattern. Data from different channel types are obtained from the literature with reference to a variety of parameters which are then grouped depending upon the scale of the problem under consideration (catchment, reach and local scales). These data for bank erosion rates are analyzed to develop general relationships with such factors as size of river system, shape of channel, bed type, gradient, riparian vegetation etc. Statistical examinations show that there is strong correlation between bank erosion rate and the catchment area and with channel geometry. Weak correlations with water discharge and with flow variability suggest that bank erosion rates will not be changed significantly in the near future if discharge and/or its variability alter under climate change. Results are used to provide science-based recommendations to estimate lateral activity applicable to many regions of the world.

This thesis addresses the problem of estimating rainfall rates from satellite imagery. The potential for using cloud motion and texture to estimate rain rates has been examined. The main types of textural information, i.e. statistical, structural, frequency and spatio-temporal, have been used to derive features from the satellite measurements and then used to determine a relationship to the radar-observed rain rates. These features were ranked by two scoring functions that were devised to assess their relationship to rain rates. The first scoring function selected a feature set for classifying samples into three rain rate classes. The selected features successfully classify rain rates of a mid-latitude cyclone seen on Meteosat7 with 84.8-99.3 % accuracy with a significant Hanssen-Kuipers discriminant score when a probabilistic neural network was used. A similar accuracy was found when a support vector machine (SVM) was used. Another scoring function was used for the selection of the features for estimating rain rates of each class. A Gaussian-kernel SVM that has been trained by these features produced visually agreeable rain estimates, which were much better than those produced by other methods that used only spectral information. Using the same types features at different time also achieved the similar accuracy. The method was robust and continuous rain estimates were obtained. Unlike other techniques in which additional information has always been required, the results showed that textural information alone can be used for rain estimation. This is preferable when only satellite measurements are available. Frequent updating of the observed rain rates can be done to improve the accuracy of the estimation. The potential for using cloud motion to predict rain rates was also examined. It was found that a combination of the maximum cross correlation and optical flow techniques provided the best estimate of the velocity of clouds. A cloud’s displacement derived by the maximum cross correlation technique was used for the approximation of the future location of its corresponding rain and the final velocity derived by the optical flow technique predicts how the rain rates would change. The rain rates predicted by this novel method provided good correlation to the observed rain rates at an hour later.

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Humans have interacted with their surroundings for over one million years, and researchers have only recently been able to assess the geomorphic impacts indigenous peoples had on their landscapes prior to the onset of European colonialism. The history of human occupation of Australia is noteworthy in that Aboriginal Australians arrived ~50 ka and remained relatively isolated from the rest of the world until the AD 1788 when Europeans established a permanent settlement in Sydney, New South Wales. The southeastern Australian Tablelands landscape, west of Sydney, has seemingly undergone drastic geomorphic change since European arrival. The introduction of European grazing practices reportedly led to the occurrence of deep erosional incisions, gullies, into valley bottoms and hillslopes, releasing sediment, which is subsequently deposited over downstream wetland environments – swampy meadows. This sediment is often called post-settlement alluvium (PSA); however, the age and genesis of PSA in Australia are debated. Questions regarding the geomorphic features and processes in the Tablelands remain unanswered because few studies quantify the timing of gully incision, PSA deposition, or the pre-human rate of landscape change. Erosion rates inferred from concentrations of in situ 10Be measured in fluvial sediment (n = 11) and bedrock outcrops (n = 6) range from 2.9–11.9 mm/kyr and 5.2–13.8 mm/kyr, respectively. The two sample populations are statistically indistinguishable, suggesting no relief has been generated since 600–110 ka. The overall erosion rate in the Tablelands is 7.5 mm/kyr, equal to long-term denudation rates integrated since ~20 Ma. Aboriginal Australians have been present in the Tablelands for at least 30 kyr, ~12–26% of the cosmogenic integration time, yet widespread Aboriginal fire use did not measurably affect landscape erosion until ~5.5 ka, in sync with increased charcoal in the sediment record. Portable optically stimulated luminescence (OSL) reader data from poly-mineral and poly-grain size samples collected from gully wall profiles of PSA and swampy meadow sediment show that swampy meadow environments were buried by PSA and that PSA is alluvium derived from upstream gully erosion. No relationships between bulk OSL and sample grain size or mineralogy exist, and inferences about bulk sediment mineralogy or grain size cannot be determined from portable OSL reader data. Large variability in adjacent PSA sample replicates, however, reveals incomplete sediment bleaching conditions during PSA deposition during floods. Greater bleaching efficiency is inferred from the small variability of bulk OSL data in the uppermost 10s of cm of PSA profiles. Measured concentrations of meteoric 10Be and bulk OSL in two PSA deposits in Birchams Creek show that initial gully incision eroded into weathered sandstone regolith and not swampy meadow environments, as previously believed. Initial gully incision was shallow (<15 cm) and PSA filled ponds in the lower reaches of the catchment. Continued erosion upstream led to a second depositional episode of PSA before headward gully incision from the mouth of Birchams Creek eroded through PSA deposits. Headward erosion of this gully created the continuous gully present at the site today. Initial gully incision was likely the result of livestock trampling in valley bottoms during droughts, creating localised slopes greater than the critical slope threshold required to erode the valley bottom. OSL burial ages of six PSA deposits collected throughout the Tablelands range from 195.1 ± 17.8 to 90.4 ± 8.9 a, corresponding to AD 1800–1932. The OSL burial ages are younger than European arrival in the Tablelands, and the term, PSA, is redefined as post-European settlement alluvium in Australia, recognising the earlier settlement of the region by Aboriginal Australians whose land use did not lead to PSA deposition. PSA burial ages agree with existing quantitative and anecdotal gully incision data. Contrary to previous assertions that gully incision began asynchronously in the Tablelands, three periods of synchronous gully erosion in localised areas within the Tablelands are recognized: 185 a, 158 a, and 94 a (AD 1828, 1855, and 1919, respectively) – in the southern, northern, and central Goulburn Plains, respectively. The AD 1828 and AD 1919 periods of gully incision correspond to the transition from drought-dominated climate regimes to flood-dominated regimes, and the AD 1855 period of gullying corresponds to a flood-dominated regime. Gully incision in the Tablelands is thus a result of European-introduced grazing practices, which primed the landscape for further erosion and degradation during climatic shifts. PSA deposits in the southeastern Australian Tablelands are some of the most recent examples of anthropogenic sedimentation in human history. The earliest preserved examples of PSA-type sediments are ~8,000 years old and found throughout the world. The establishment of an onset date for the Anthropocene is currently debated, and I believe the oldest PSA and PSA-type sediments around the world can define this modern epoch.

This thesis explores the factors behind national CO2 emissions trends. It highlights four instrumental – economic, social, political and environmental - explanations that scholars have posited to account for emissions behaviour and subsequently demonstrates that the artificial segregation of these approaches in the literature poses a major problem for the field. Since all of these factors matter some of the time, it argues that the research program needs to identify when each factor matters more than others and why. This thesis proposes that ideas play a key role in bringing instrumental factors to bare on climate policy. Fusing together social constructivism and the concepts of worldviews and problem representations from cognitive psychology, it proposes that instrumental factors will only have their alleged effects on emissions when a country, or the policymakers who act on its behalf, believes that the factor is of importance to world politics more broadly. Drawing on three of the leading schools of international thought, it proposes three ideal worldviews and problem representations, each of which envisages a different set of instrumentalist drivers and strategic response to climate change. Specifically, the neo-realist worldview upholds that emissions policy should maximise the gains of the state relative to others. The neo-liberal worldview, on the other hand, suggests that a state should design climate policy to minimise the domestic cost-benefit ratio of emissions behaviour. Painting a very different picture, the structuralist worldview prescribes that emissions policy should serve a state’s transnational class interests. The thesis tests these explanatory approaches by conducting a large-N study of 3,381 country-years, spanning eight supranational regions and 147 countries from 1990 to 2012. It builds a three-level model that accounts for (country and regional) clustering in emissions behaviour, thus reducing the potential for type I errors. The findings confirm that instrumental factors are indeed significant drivers of emissions trends. However, unlike previous quantitative work in the field, the results of the multilevel analyses suggest that most of these factors have heterogeneous effects between countries. The findings also suggest that worldviews play a critical role in determining what these effects are in two of the cases examined in the thesis: (i) democratization has a positive effect on emissions reduction in countries that subscribe to the neo-liberal worldview while (unexpectedly) inhibiting emissions reduction in countries that do not and (ii) a structuralist mind-set makes countries prioritise economic growth over a clean climate, thereby inhibiting emissions reduction.

No description available.

Review of animal and epidemiological studies suggest that exposure to nitrates in drinking water is associated with thyroid disorders, including mild - to - moderate iodine deficiency; hyperthyroidism; hypothyroidism; thyroid hypertrophy (goitre) and thyroid cancer. However, the weight of evidence following a meta – analysis is strongest for goitre; weak for subclinical hypothyroidism and weakest for clinical hypothyroidism and hyperthyroidism (clinical and subclinical). The effect estimate for goitre is, OR = 3.13 (95%Cl: 2.35-4.16); I2 = 24.9%, p = 0.28. Although causality was not firmly established between nitrates in drinking water and goitre, the risk assessment framework was used to estimate lifetime excess risk of thyroid cancer in East Anglia given widespread nitrate contamination of drinking water sources in the region. Thyroid cancer was used as a proxy for goitre given that malignancy can result from goitre which is usually benign and there is no register for goitre and/or benign thyroid tumours in the UK. Risk estimates suggests that 20 cases or 13 per cent of the 154 thyroid cancer cases calculated in a population of 2,849,918 in East Anglia in 2014, can be attributable to nitrates in drinking water and this would have been eliminated from the population if there was no nitrates in drinking water. The lifetime excess risk of thyroid cancer at nitrate levels below and equal to the drinking water standard of 50mg/l, is 0.02 – 0.28. This is above the range (1x10-6 to 1x10-5) considered negligible and suggests that the current drinking water standard for nitrates, originally set to protect against infantile methaemoglobinemia is unlikely to protect against thyroid cancer and warrants a review. The review should include a consideration of lowering the drinking water standard; reduction of nitrates in drinking water sources and/-or introducing iodine prophylaxis in the UK given that the effect of nitrates on the thyroid gland is dependent on the amount of dietary iodine intake. Although there were a lot of uncertainties and assumptions in the risk assessment process, the recommendation is based on the precautionary principle.