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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Effect of heavy metal co-contamination on the biodegradation of polycyclic aromatic hydrocarbons in an urban soil with high organic carbon content

Ekumankama, Chinedu January 2015 (has links)
Biodegradation is a commonly used approach for the removal of organic contaminants from soil, relying on naturally present microorganisms that utilise the pollutants as an energy source. Often these sites are co-contaminated with heavy metals and the aim of the current research was to investigate how this affects the biodegradation of 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs), both in terms of removal rates and the overall functioning of the soil microbial community. Soil samples were obtained from a Greenfield site in Newcastle upon Tyne. The soil had a high organic content (11.0 %) and also contained elevated lead concentrations as a result of past atmospheric deposition from adjacent industrial activities. PAHs were applied to the soil using a coal tar source dissolved in acetone, giving a total PAH concentration in the spiked soil of 2166 mg kg-1. Individual PAH concentrations ranged from 1.44 mg kg-1 (acenaphthylene) to 325 mg kg-1 (benzo[b]fluoranthene); the benzo[a]pyrene concentration was 255 mg kg-1. The effect of heavy metal co-contaminants on the biodegradation was investigated using separate amendments of cadmium and lead to give respective total concentrations ranging from 133 to 620 mg kg-1 and 340 to 817 mg kg-1. Mercury amendment was used to give an abiotic control. The study was carried out over 40 weeks. For all treatments, the degradation of PAHs was observed to be biphasic. A novel kinetic model was developed to explain this dependence. In the absence of metal amendment, it was found that PAHs comprising two and three benzene rings generally degrade at a faster rate than four- five and six-membered rings. In the presence of metal amendments, overall % biodegradation after 40 weeks is relatively unaffected for two to four-ring PAHs but shows significant impairment for five and six-ring PAHs. Nevertheless, degradation rates generally decrease with increasing metal concentration, as do soil respiration rate, Shannon Diversity Index, and microbial biomass content. Lead appears to exert the greatest inhibitory effect. The novelty of this study arises from the integrated approach to investigating the effect of metal co-contaminants on the biodegradation of all 16 US EPA priority PAHs together with parameters relating to the functioning and diversity of the soil microbial community.
12

Landscape and ecological modelling : development of a plant community prediction tool for Estonian coastal wetlands

Ward, Raymond January 2012 (has links)
Estonian coastal wetlands are of international importance as they support characteristic biological diversity. Their limited extent and distribution mean that these wetlands are of high conservation concern, and as such have been identified as a priority in the European Union Habitats Directive. These wetlands are typified by a flat, extensive landscape, situated between the micro-tidal «0.02m), brackish Baltic Sea and a forest interior. Due to the low relief these wetlands may be under threat from sea level rise. This research consisted of four studies: (i) to determine and quantify the relationship between a range of coastal wetland plant community types, elevation and edaphic conditions. Results demonstrated that plant community distribution was significantly affected by micro-topography and edaphic variability. The majority of the plant communities were discernible in the field by elevation alone and elevation was found to be the factor that could distinguish the greatest number of plant communities. (ii) to determine an appropriate method of interpolating LiDAR elevation data and assess the use of LiDAR data in creating a static correlative model to determine plant community type based on elevation. Results showed that with dGPS calibration the model could accurately predict plant community location. Validation of the model in two further sites showed that the correlative model was able to predict plant community with almost perfect (K 0.81) and moderate agreement (K 0.53) dependent on the site. (iii) to determine sediment accretion rates to complete the dynamic model by analysing the level of radionuclides, 137CS and 210Pb, in discrete core sections. Results showed that during periods of greater storminess sediment accretion increased almost threefold. These sensitivity data were included in the dynamic correlative model. (iv) to assess the effects of sea level rise on plant communities in Estonian coastal wetlands under five sea level scenarios, two accretion rate scenarios and factoring in isostatic uplift rates. Results showed that local sea level will rise in some sites and decrease in others dependent on location and SLR scenario. This study has indicated that in many instances Estonian coastal wetlands will increase in extent in the future due to high rates of sediment accretion, particularly in a scenario with more frequent storms, and isostatic uplift. The study has shown that following validation, calibration and sensitivity analysis LiDAR data can be used to accurately predict plant community type in microtopographical ecosystems. The model developed in this study of Estonian coastal wetlands is likely to be transferable to other appropriate habitats such as tidal, estuarine, and floodplains wetlands.
13

Floodplain geomorphology and topography in large rivers

Strick, Robert John Paul January 2016 (has links)
Rivers are essential components of the earth surface. The world’s largest rivers have been studied much less than to smaller rivers. They are dominated by meandering channels – whether these are individual km-wide meander bends or ‘accessory’ meandering channels in an anabranching system. Large rivers, specifically ones with laterally migrating bends, can build a variety of floodplain elements that are represented by a complex surface topography, the dynamics and characteristics of which are not yet fully understood. This research brings a greater understanding to, and quantification of, the floodplain topography and geomorphology of large rivers. The project uses remote sensing imagery of the World’s largest rivers, LiDAR datasets of meandering scroll bar topography, and global coverage elevation data. Novel analytical methods are created, involving image manipulation and GIS processing, to quantify these landforms in a way that was not possible until recent technological and computational advancements. A new hierarchical classification schema of meandering floodplain deposits is presented and applied to quantify meandering deposits for two large rivers, the Amazon and the Ob. Both floodplains show similar downstream morphological changes to their floodplains despite their different sizes and locations. The new classification schema works well to describe meandering floodplain deposits. The geomorphology of scroll bars is investigated for the Mississippi River, revealing the heterogeneity of these deposits and that local meander bend conditions are important in determining scroll bar formation and preservation on the floodplain. The periodicity of scroll bars from a range of rivers is investigated and it is shown that scroll bars are intrinsically linked with the width of the adjacent river channel and respond to local planform changes. Floodplains of large rivers have complex overbank sedimentation processes that create spillage sedimentation phenomena. Spillage sedimentation was quantified down a 1700 km reach of the Amazon River and a 1400 km reach for the River Ob, revealing spatial discontinuities in spillage phenomena. Spillage dominance depends on diverse sediment loadings, hydrological sequencing, and morphological opportunity. Understanding spillage dynamics is important in quantifying overbank sedimentation rates and the spatial distribution of fine-grained deposits. The findings of this thesis highlight that despite the incredible complexity and heterogeneity of large river floodplains, order can be inferred via classification schemas and fundamental relationships identified. The thesis uses novel methods and conceptual models to bring a greater understanding and quantification to this complex floodplain geomorphology.
14

The sedimentology of the Ashdown formation and the Wadhurst Clay formation, southeast England

Akinlotan, Oladapo Odunayo January 2015 (has links)
Detailed sedimentological studies, using coastal and inland exposures, were carried out at formation and bed levels on the Ashdown and Wadhurst Clay formations (Late Berriasian-Valanginian) in the Weald, southeast England. Field descriptions of outcrops were conducted at seven sites and supplemented by borehole and 2D seismic data. Field samples were studied in detail using hand specimen analysis. The sandstones were described in hand specimen and via optical microscopy. Clay mineral and geochemical analyses on mudstones, shales, and ironstones were conducted using XRD, XRF, and SGR methods while SEM analyses were conducted on selected sandstones and ironstones. Porosity and permeability of selected sandstones were measured using pycnometry and gas permeametry respectively. The dominance of quartz arenites and kaolinite and the presence of thorium and Zr in the sediments suggest that they were sourced mainly from granitic and/or gneissic rocks. Materials from metamorphic sources appear to be secondary in abundance. The mineralogical and textural maturity of the sediments coupled with relatively short travel distance (~300km) suggests reworking from secondary or matured sources. The two formations received sediments from at least two sources. The clay mineral assemblage, sandstone composition, and gamma-ray data confirm that the main source of the sediments is the London Massif in the north and north east while sediments were also sourced from Armorica in the south based on the presence of detrital zircon. The palaeoclimatic conditions at the source area as revealed by the dominance of quartz arenites and kaolinite and the presence of thorium were warm and humid which led to intensive weathering. The mineralogy and geochemistry of the sediments suggest that they may have been directly or indirectly sourced from a stable craton. The lithology (sandstones, siltstones, mudstones, shales and ironstones); facies (channel and floodplain/overbank); sedimentary structures (channels, cross stratification, flaser bedding, ripples and planar laminations); sedimentary architecture (repeated cycles and vertically stacked multi-storey successions), and gamma ray data (more radioactive sandstone facies) confirm that the sediments within the two formations were deposited in predominantly fresh water environments although tidal and lagoonal conditions were clearly evident in the Ashdown Formation and Wadhurst Clay Formation respectively. The lithology and sedimentary facies show that deposition occurred in both braided and meandering river systems although meandering facies are more prominent in the lower Ashdown Formation. The presence of abundant load and slump structures and fresh green glauconite in the sandstones provide evidence that deposition was rapid while the water depth was shallow and not beyond 2 metres based on the widespread occurrence of colour mottling and frequent exposure of the sediments to the air. Early diagenesis was confirmed by the precipitation of sideritic ironstones while diagenetic alteration is minimal based on the clay mineral assemblage. Evidence from the shallow burial nature of sideritic ironstone, the proportion of illite-smectite and the nature of diagenesis confirm that the sediments have experienced shallow burial not beyond 2km. Enrichments in redox sensitive trace elements such as Mo, U, V and Co suggest anoxic conditions in the sediments. The highest levels of anoxia were in the lower sections of the formations. Palaeosalinity as indicated by sideritic ironstone indicates a pH between 6 and 10. Porosity ranges from 6.8% to 13. 2% with an average of 9.9% while permeability ranges from 0.4mD to 11.9mD with an average of 3.1mD. The main controls on porosity and permeability are grain sizes, grain shapes, and sorting and the porosity is mainly primary. The main control on sedimentation is the local tectonics at the source areas while palaeoclimatic conditions, sea level, river dynamics, and subsidence are secondary. The proximal part of the modern Niger Delta is proposed as an analogue for the palaeoenvironments of the Ashdown and Wadhurst Clay formations. More generally, the results presented in this thesis highlight the usefulness of integrating field, petrographic, mineralogical, and geochemical data, and the use of modern analogue to fully assess the depositional environments, stratigraphic variability, post depositional changes and controls on deposition within sedimentary basins.
15

Karst-associated bauxite deposits of Parnassos-Ghiona, Central Greece : ore genesis and structural evolution

Williams, Richard James January 2014 (has links)
The karst-associated bauxites of the Parnassos-Ghiona zone in Central Greece are part of the large Mesozoic age Mediterranean Karst Bauxite belt. Greece is responsible for around 50% of European bauxite production, and has an estimated 600 million tonnes of bauxite reserves. This investigation focuses on the bauxites of Mount Iti and Mount Ghiona, two mountains in the west of the Parnassos-Ghiona zone that are currently being explored and mined by Greek bauxite producer, Elmin S.A. The aim was to develop a better geological understanding of the ore genetic history and regional structural evolution to aid ore deposit science and bauxite exploration. Within the Parnassos-Ghiona zone the bauxites were deposited as three separate ore horizons intercalated with thick limestone layers during the early Jurassic, late Jurassic and late Cretaceous. Only the upper two bauxite horizons are economic and therefore formed the focus of this investigation.
16

Influence of stratigraphy and heterogeneity on simulated microwave brightness temperatures of shallow snowpacks

Watts, Tom January 2015 (has links)
Snow accumulation has potential climatological, hydrological and ecological impacts at a global scale. Satellite passive microwave radiometers have the potential to provide snow accumulation data with a historical record of over 30 years, however, current data products contain unknown uncertainty and error. Snowpack stratigraphy is the spatial variation in snowpack properties caused by the layered nature of the snowpack. Snowpack stratigraphy influences the accuracy and increases uncertainty in simulations of microwave emission from snow which in turn increases uncertainty in satellite derived estimates of snow water equivalent using microwave radiometers. Two methods were developed to help better quantify snowpack stratigraphy. An improved technique for characterising snowpack stratigraphy within a snow trench was developed. Secondly a new method was developed to quantify the density of ice layers that form in snowpacks with known error and uncertainty. Snowpack stratigraphy was characterised using the improved technique across the Trail Valley Creek watershed in the Canadian Northwest Territories. Two 50 m trenches and eleven 5 m trenches were dug across the range of landcover types found in the watershed. This dataset allowed layer boundary roughness to be characterised and the properties of snow layers to be mapped with an unprecedented level of accuracy. Ice lens density was measured 60 times at three locations in the Arctic and midlatitudes at locations with coincident ground based radiometer measurements. The impact that accurate parameterisation of density has on modelled estimates of brightness temperature was quantified. Simulations of microwave brightness temperatures were conducted using snow emission models at all locations. The output of these simulations, and comparison to ground based observations where available, allowed for the characterisation of variability in brightness temperature simulations caused by stratigraphic heterogeneity. The findings presented in this thesis will inform research aiming to better characterise the satellite error budget. Improvements in this area helps improve global snow mass and snow accumulation estimates.
17

Modelling of building performance under the UK climate change projections and the prediction of future heating and cooling design loads in building spaces

Du, Hu January 2012 (has links)
New climate change projections for the UK were published by the United Kingdom Climate Impacts Programme in 2009. They form the 5th and most comprehensive set of predictions of climate change developed for the UK to date. As one of main products of UK Climate Projections 2009 (UKCP09), the Weather Generator, can generate a set of daily and hourly future weather variables at different time periods (2020s to 2080s) and carbon emission scenarios (low, medium and high) on a 5 km grid scale. In a radical departure from previous methods, the 2009 Projections are statistical-probabilistic in nature. A tool has been developed in Matlab to generate future Test Reference Year (TRY) and Design Reference Years (DRY) weather files from these Projections and the results were verified against results from alternative tools produced by Manchester University and Exeter University as well as with CIBSE’s Future Weather Years (FWYs) which are based on earlier (4th generation) climate change scenarios and are currently used by practitioners. The Northumbria tool is computationally efficient and can extract a single Test Reference Year and 2 Design Reference Years from 3000 years of raw data in less than 6 minutes on a typical modern PC. It uses an established ISO method for generating Test Reference Year data and an alternative method of constructing future Design Reference Years data is proposed. Fifteen different buildings have been identified according to alternative usage, thermal insulation, user activity and construction details. Besides these variants, the buildings were chosen specifically because they either exist, or have received planning consent and so represent ‘real’ UK building examples. Two investigations were then carried out based on the 15 case study buildings. The first involved applying TRYs generated for London, Manchester and Edinburgh for a variety of carbon emission scenarios at time horizons of 2030, 2050 and 2080. The TRYs were developed into a weather data format readable by the EnergyPlus energy simulation program to simulate summertime internal comfort (operative) temperatures, cooling demands and winter heating demands. All results were compared with a control data set of nominally current weather data, together with the same results produced using the alternative weather data generators of Manchester University, Exeter University and the CIBSE FWYs. Results revealed a good agreement between the various methods and show that significant increases in internal summer operative temperatures in non-air-conditioned buildings can be expected as time advances through this century, as well as increased air conditioning cooling energy demands and small reductions in winter heating energy demand. The second investigation involved generating time series of design internal peak summertime operative temperatures, design cooling demands and design winter heating demands for the same conditions as the first investigation. The results were then used to develop a simplified estimation method to predict future design cooling loads using multiple regressions fitting to selected data from the DRY simulation inputs and outputs. The simplified estimation method forms a useful tool for estimating how future cooling design loads in buildings are likely to evolve over time. It also provides a basis for designers and practitioners to determine how buildings constructed today will need to be adapted through life to cope with climate change.
18

Southern high-latitude vegetation and climate change during the Holocene (South Georgia) and Oligocene (Wilkes Land, Antarctica)

Strother, Stephanie January 2016 (has links)
Significant climate and vegetation changes have occurred during the Cenozoic era (66 Ma - present), particularly in the southern-high latitudes. The terrestrial record in Antarctica is fragmentary and available successions are limited due to remoteness and thick ice cover. The aim of this study is to provide new insights into what changes occurred during available successions in two epochs of the Cenozoic, the Holocene (11.7 ka - present) and the Oligocene (33.9 - 23.03 Ma) in the sub- Antarctic and East Antarctic region. This thesis begins on South Georgia Island in the sub-Antarctic region, where a 5.8-m long high-resolution pollen record covering the last 7000 years was taken from Fan Lake on Annenkov Island. Palynological and sedimentological analyses indicated warm late Holocene conditions between 3790 and 2750 cal. yr BP transitioning to a cooler and wetter environment. Increases in long-distance pollen grains from South America between c. 2210 and 1670 cal. yr BP and after 710 cal. yr BP suggested strong Southern Hemisphere Westerly Winds over South Georgia during the late Holocene. These results question previous studies which proposed highest wind intensity during the warmer mid-Holocene climate optimum. Little is known about how Antarctic vegetation changed from the subtropical and temperate rainforests of the warm Eocene to the cold tundra shrubs which dominated during the Miocene. Oligocene assemblages from site U1356 Wilkes Land, East Antarctica (IODP 318) covering ~33-30 and ~25-23 Ma are characterised by lowland fragmented cool forests and tundra/shrubland. Temperature reconstructions derived from the fossil pollen assemblages using the Coexistence Approach suggest mean annual temperatures between 5.8-13.7°C during the Oligocene. A decline in warmer taxa (e.g. Dacrydium praecupressinoides and Phyllocladidites mawsonii) and high abundance of reworked sporomorphs and Leiosphaeridia sp. indicate the progression towards cooler/glaciated conditions between ~25-23 Ma. The Wilkes Land assemblage shows a warmer palaeoflora compared to previous Antarctic palaeorecords and the regional vegetation differences may be explained by the palaeotopography of Wilkes Land which has a lower altitude and reduced glacial influence in contrast to other sites. After the formation of the cryosphere at the Eocene-Oligocene transition glacial reworking is a major component in Antarctic marine and terrestrial sedimentary deposits. Uncertainty as to whether Cenozoic sporomorphs were reworked or in situ has previously restricted palaeoenvironmental reconstructions. This thesis presents a new red fluorescence approach to differentiate reworked and in situ sporomorphs over relatively short geologic timescale (e.g. Paleogene and Neogene). The establishment of an in situ palaeoflora assemblage from Wilkes Land enables a robust interpretation of Oligocene environments without the influence of reworking.
19

Mainstreaming disaster risk reduction into community development in the Windward Islands

Ferdinand, Idelia January 2013 (has links)
The Windward Islands are vulnerable to a number of natural hazards. This thesis examines the possibilities for Disaster Risk Reduction (DRR) in the Windward Islands. The Windward Islands offer a special case of “Island Vulnerability”. Island vulnerability is essentially defined as an increased probability in disaster events against what would be expected if vulnerability were to be measured against international levels of poverty, defined as Gross National Product per capita. There are three reasons for this namely the topography of islands, the site characteristics and the socio-economic setting. The topography is one where islands, largely of volcanic or coral origins, face multi-hazard experience particularly from flooding and storm surge. The site issue is that islands usually have a high ratio of coastline to land mass implying a relatively higher exposure to extreme events. The socio-economic conditions are peculiar to island including isolation, mono-agriculture and mono-industry essentially laid down by colonial experience, an absence of formal employment opportunities and weak capacity in local governance including the absence of NGOs. Though DRR has evolved over the last 20 years, some islands and communities remain more vulnerable than others. This research investigates the mainstreaming of DRR in the Windward Islands of Dominica, Grenada, Saint Lucia and St Vincent and the Grenadines. The key issue researched was whether DRR could be effectively implemented at the community level. To address this issue, the research investigates the vulnerability and capacity of communities to hazards in the Windward Islands and suggests ways to reduce risk and build community resilience. The factors affecting vulnerability and capacity to hazards in the Anglophone Windward Islands were identified as a means of determining how to reduce risks and build resilience to hazards in the Windward Islands. Efforts to enhance community development and build resilience are not effective as they fail to address fully community needs. This research concluded that some communities are more vulnerable than others and a major contributor to their vulnerability is poverty. None of the methods used in this research are unique to island vulnerability analysis as they have been applied elsewhere in DRR. What is unique is the scoping of the application of these methods to gain an overview of DRR possibilities. What emerges as a conclusion is the limited impact of top down interventions, especially those interventions that try to address poverty alleviation to lower risk. This is essentially because the poor themselves barricade their own coping mechanisms against external interventions, thus building a wall against external help. Building on local organisational capacity, including religious groups, can help address this problem. Research in this area is limited for the Anglophone Windward Islands and this thesis on vulnerability of household and communities will contribute to knowledge in this field.
20

Englacial stratigraphy, debris entrainment and ice sheet stability of Horseshoe Valley, West Antarctica

Winter, Kate January 2016 (has links)
Despite the importance of ice streaming to the evaluation of West Antarctic Ice Sheet (WAIS) stability, we know little about mid-to long term changes in grounding line migration, ice streaming and ice accumulation in the upper Institute Ice Stream (IIS) catchment. In this thesis ground penetrating radar (GPR) and airborne radio-echo sounding (RES) methods have been employed to investigate the subglacial topography, internal stratigraphy and Holocene flow regime of the upper IIS catchment, in and around Horseshoe Valley. High resolution step-andcollect mode GPR was employed to assess the continuity of a Blue Ice Area (BIA) horizontal ice core climate record at Patriot Hills, where analysis has revealed two unconformities in the otherwise conformable 30,000 year climate sequence. By combining these data with airborne RES returns and pre-existing ice sheet models it is suggested that these unconformities represent periods of erosion, occurring as the former ice surface was scoured by katabatic winds in front of Liberty and Mable Hills. Snow_Blow simulations suggest that katabatic winds have scoured the leeward slopes of these mountain ranges for over 10,000 years. This temporal stability can account for the large volume of BI moraine deposits in Horseshoe Valley, where compressive BI flows promote glacial erosion and near-surface debris entrainment through freeze-on processes at the ice/bed interface and compressive thrust faulting. By investigating thicker ice flows in the upper IIS catchment and the Evans Ice Stream, this thesis has also analysed debris entrainment mechanisms at depth, where clasts are incorporated into the ice flow by englacial stratigraphic folding and shearing at the glacial thermal boundary, governed by spatial and temporal changes in ice flow, ice temperature and sediment availability. Mid-to long term changes in ice flow in the wider IIS catchment have been investigated from airborne RES transects, revealing internal layer buckling, and therefore former enhanced ice-sheet flow in three distinct tributaries of the IIS. Buckled ice layers throughout the slow flowing ice in the Independence Trough and the fast-flowing ice in the Ellsworth Trough suggest that enhanced ice flow through these topographically confined regions was the source of ice streaming and iceflow reconfiguration during the mid-to-late Holocene. Although buckled layers also exist within the slow-flowing ice of Horseshoe Valley, a thicker sequence of surface-conformable layers in the upper ice column suggests slowdown more than 4000 years ago, indicating that enhanced flow switch off here cannot be attributed to late-Holocene ice flow reorganisation. The dynamic nature of ice flow in the IIS and its tributaries suggests that ice stream switching and mass change may have been regular during the Holocene, and that these changes may characterise the decline of the WAIS in this area. These results have important implications for our understanding of ice-sheet dynamics and the response of the ice sheet to climate change and provides explanations for fluctuations in debris entrainment and transportation processes in Antarctica.

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