Tesi sul tema "Sediment"

This volume comprises ninety-one contributions to the Sediment 2011 conference of the Central European section of the Society for Sedimentary Geology (SEPM-CES) and the Geologische Vereinigung (GV) at the University of Leipzig held in June 2011. The central theme of this meeting was “Sediments: Archives of the Earth System” in order to bring together young and established researchers from all fields of soft-rock geology and beyond to shape a stimulating interdisciplinary program on the role of sediments in understanding the System Earth and the evolution of paleoenvironments and climate through time.

Several sediment characteristics were analyzed to determine their suitability for use as potential normalization factors for the bioavailability of neutral organic compounds sorbed to sediments. Percent organic carbon, cation exchange capacity and particle surface area were measured sediment characteristics that varied sufficiently to encompass the range in observed sediment toxicity. Laboratory sediment toxicity test data using fluoranthene suggest that there is no biologically significant correlation between sediment toxicity and sediment characteristics (organic carbon, cation exchange capacity, particle size distribution, particle surface area). Fluoranthene amended sediments with similar organic carbon contents do not yield similar toxicities due to sorbed fluoranthene and thus do not support the organic carbon normalization approach for evaluating sediment quality or for sediment criteria development.

Over the last decades, fast urban sprawl and accelerated land use change have drastically increased the pressure on water resources of the capital Brasília and its surrounding area. The water supply of the metropolitan region of Brasília depends largely on surface water collected in reservoirs. There are increasing concerns regarding water shortages due to sediment aggradations, and of water quality due to geochemical modification of sediments from human activities. The complexity of various socio-environmental problems, such as non-point source pollution, soil erosion or silting of water reservoirs within urban catchments evoked the need for more effective and sustainable strategies to use land and water resources. Accurate identification and management of sediment source areas, however, is hampered by the lack of reliable information on the primary sources of sediment and on sediment geochemistry. The fingerprinting approach and a multivariate mixing model have been proven to be a valuable sediment source tracing technique across the globe and for various environmental settings. A multi-component methodology, including geochemical and geophysical analyses of representative sediment source and alluvial sediment samples, statistical analyses and a multivariate mixing model, was utilized to obtain the impact of different anthropogenic activities on sediment and water quality and to identify the major sources of sediments within the Lago Paranoá catchment. However, sediment source appointment and geochemical signatures of sediments in urbanized tropical regions, such as the Lago Paranoá catchment in the DF, are hampered by severe challenges; (i) the presence of various types of land use and heavy urbanized areas, (ii) large differences between sub-catchments and (iii) model structural failures in representing the sediment source contribution within urban tropical river basins. The present cumulative thesis addresses the challenges in geochemical analyses of different types of source and alluvial sediments, and in sediment source appointment for the Lago Paranoá catchment and it´s five sub-catchments. The aim of the study was to assess the distribution of chemical elements and geochemical/physical properties of potential sediment sources in the Lago Paranoá catchment. Principal component analysis and hierarchical cluster analysis were used to investigate the influence of different land use types on the geochemistry of sediments. Geochemical fingerprints of anthropogenic activities were developed based on the results of the cluster analysis grouping. The anthropogenic input of land use specific geochemical elements was examined and quantified by the calculation of enrichment factors using the local geological background as reference. The existing findings suggest a strong relationship between land use and quantifiable features of sediment geochemistry, and identified the combined effects of specific anthropogenic activities and metal enrichment in source and alluvial sediments. Through comparison of the geochemical signature of potential sediment sources and alluvial sediments of the Lago Paranoá and sub-catchments, the relative contribution of land use specific sediment sources to the sediment deposition of the main water reservoir were estimated. This assessment indicated that urban land use had the greatest responsibility for recent silting in the Lago Paranoá. In fact, one of the most challenging issues within the scope of IWRM is to quantify the contribution of sediment sources within fast urbanizing, mixed used, tropical catchments. Therefore, statistically verified composite fingerprints and a modified multivariate mixing model have been used to identify the main land use specific sources of sediment deposited in the silting zones of the Lago Paranoá, Central Brazil. Because of the great variability of urban land use types within the Lago Paranoá sub-catchments, the fingerprinting approach was additionally undertaking for the Riacho Fundo sub-catchment. This sediment source tracing technique provides valuable information on the response of the main sediment sources in a fast growing agglomeration with respect to specific land uses and human activities and allowed to examine the uncertainty in model prediction. The main contributions from individual source types (i.e. surface materials from residential areas, constructions sites, road deposited sediment, cultivated areas, pasture, farm tracks, woodland and natural gullies) varied between the whole catchment and the Riacho Fundo sub-catchment, reflecting the different proportions of land uses. The sediments deposited in the silting zones of the Lago Paranoá originate largely from urban sources (85±4%). Areas with (semi-) natural vegetation and natural gullies contribute 10±2% of the sediment yield. Agricultural sites have only a minor sediment contribution of about 5±4 % within the whole catchment. However, there is no mechanism considered to reflect seasonality in the tropics, e.g. phenological change of the vegetation between wet and dry season, or and temporal changes in land use, e.g. construction sites, which influence model estimates. Nevertheless, the study reveals that even 58 % of the land remains in (semi-) natural state, the main sediment source are urban areas. Beside the analyses of sediments, it was found that metal concentrations in surface water of the main tributaries to the Lago Paranoá are generally low, but show seasonal variability. Terrestrial inputs of metals occur during the rainy season and depend largely on the influence of urban land use. The present thesis shows the great influence of anthropogenic activities on sediment generation, and at least to some degree, on sediment associated pollution loads. It depicts region specific challenges, but also provides essential information to guide management responses towards more effective sediment source-reduction strategies
Im Gebiet des Bundesdistrikts Brasilien ist ein erheblicher Druck auf die Wasserressourcen zu beobachten, der vorwiegend durch starkes Bevölkerungswachstum, ungeplante Suburbanisierung und Landnutzungsänderungen innerhalb der letzten Jahrzehnte ausgeübt wird. Die Wasserversorgung der jungen Hauptstadt Brasília und seiner suburbanen Räume wird im Wesentlichen durch in Stauseen gesammeltes Oberflächenwasser gewährleistet. Durch die voranschreitende Ausdehnung von urbanen und landwirtschaftlichen Flächen spielen insbesondere Sedimenteinträge in die Stauanlagen sowie sedimentgebundene Stoffbelastungen durch anthropogene Aktivitäten für die verfügbare Wasserquantität und Wasserqualität eine bedeutende Rolle. Damit verbundene negative Umweltauswirkungen sowie die daraus resultierenden sozioökonomische Konsequenzen erfordern daher dringend wirksame und nachhaltige Strategien im Land-und Wasserressourcenmanagement. Eine deutliche Minimierung der Sedimenteinträge und Stoffbelastungen in das Gewässernetz ist jedoch nur mit Kenntnis der Primärquellen von Sedimenten und der Sedimentgeochemie zu erreichen. Der "Fingerprinting"-Ansatz und der Einsatz eines "Multivariate Mixing-Modell", sind geeignete Werkzeuge um den Einfluss anthropogener Eingriffe in das landschaftsökologische Prozessgefüge der Sedimentgenerierung zu klären. Die vorliegende kumulative Dissertation zeigt dies anhand der Anwendung einer Multikomponenten-Methodik. Diese beinhaltet sowohl geochemische und geophysikalische Analysen repräsentativer Sedimentproben der Sedimentquellen und der finalen Senken (Auenbereiche und Bereiche der Zuflüsse zum Lago Paranoá) als auch umfassende statistische Analysen sowie die Anwendung eines modifizierten "Multivariate Mixing-Modells". Der Einsatzder "Fingerprinting" Methodik in urbanen Einzugsgebieten der wechselfeuchten Tropen, wie das des Lago Paranoá in Zentralbrasilien, ist jedoch mit erheblichen Herausforderungen verbunden. Das betrifft insbesondere die Heterogenität der Landnutzungstypen innerhalb einer Landnutzungsklasse (urban, landwirtschaftlich, semi-natürlich) und die Unterschiede der Landnutzungsanteile zwischen den einzelnen Teileinzugsgebieten als auch modelstruktureller Unzulänglichkeiten bei der Sedimentherkunftsberechnung für urbane Einzugsgebiete. Eine Hauptkomponentenanalyse und hierarchische Clusteranalyse wurden verwendet, um den Einfluss der verschiedenen Landnutzungstypen auf der Geochemie der Sedimente zu untersuchen. Geochemische Fingerprints verschiedener anthropogener Aktivitäten wurden auf der Grundlage der Ergebnisse der Clusteranalyse ("grouping") entwickelt. Die Berechnung von Anreicherungsfaktoren ("Enrichmentfactors") auf Basis der gemessenen Elementgehalte, mit dem lokalen geologischen Hintergrundwerten als Referenz, ermöglichte die Quantifizierung des Einflusses der verschiedenen Landnutzungen auf die Metalleinträge in die Sedimente. Die vorhandenen Ergebnisse legen nahe, dass eine direkte Beziehung zwischen Landnutzung und quantifizierbarer Merkmale der Sedimentgeochemie existiert. Ein Vergleich der geochemischen Signatur von potentiellen Sedimentquellen und mit jenen der alluvialen Sedimente unterstützt die Hypothese, dass urbane Gebiete einen beachtlichen Beitrag zur Sedimentgenerierung und letztendlich zur Sedimentablagerung in den Auen- und Zuflussbereichen des Lago Paranoá leisten. Da diese relative Betrachtung von Elementzusammensetzungen der Sedimente keine quantitativen Aussagen zur Bedeutung der einzelnen Sedimentquellen zulässt, wurden statistisch verifizierte "composite fingerprints" und ein an urbane Bedingungen modifiziertes multivariate mixing-Modell (Hybrid) entwickelt und angewendet. Die Modellberechnungen erfolgten für das gesamte Einzugsgebiet des Lago Paranoá und separat für das Riacho Fundo Teileinzugsgebiet, welches Die angepassten Modellschätzungen zeigten, dass die in den Verlandungszonen des Lago Paranoá abgelagerten Sedimente weitgehend aus urbane Räumen (85 ± 4%) generiert wurden. Dahingegen stammen nur 10 ± 2% der Sedimente aus Gebieten mit (semi-) natürlicher Vegetation, obwohl 58 % der gesamten Einzugsgebietsfläche des Lago Paranoá stets (semi-) natürliche Verhältnisse aufweist. Landwirtschaftliche Gebiete haben generell nur einen geringen Anteil von etwa 5 ± 4% am Sedimenteintrag. Die Unterschiede in den Sedimentbeträgen sowohl zwischen den verschiedenen Sedimentquelltypen als auch zwischen den einzelnen Teileinzugsgebieten scheinen maßgeblich von den Flächennutzungsanteilen (urban, landwirtschaftlich, semi-natürlich) in dem jeweiligen Teileinzugsgebiet abhängig zu sein. Trotz umfassender Probennahme, Probenanalytik, Modellanpassung und Unsicherheitsanalyse sind die Ergebnisse nur für den Beprobungszeitraum, für die analysierte Stoffgruppe (organische Stoffeinträge sind im Rahmen dieser Dissertation nicht erfasst) und für die ausgewählten Lokalitäten repräsentativ. Zeitliche Einflussgrößen wie die Saisonalität in den Tropen oder Änderungen der Landnutzung, wie z.B. temporäre Baustellen, konnten mit den hier verwendeten Methoden nicht erfasst werden. Um die hohe räumliche und zeitliche Variabilität der Sedimentdynamik und eine deutliche Minimierung der Sedimenteinträge in das Gewässernetz zu erzielen, sind demnach die Einrichtung und der Betrieb eines langfristigen Monitoring-Netzwerkes für Sedimente im Einzugsgebiet des Lago Paranoá von hoher Priorität. Die vorliegende Dissertation bringt neue Einsichten in verschiedene wichtige Aspekte der geochemischen Beeinflussung von Sedimenten durch anthropogene Aktivitäten und liefert erstmalig quantitative Aussagen zu den Sedimentquellgebieten im Einzugsgebiet des Lago Paranoá. Sie stellt regionsspezifische Herausforderungen heraus, liefert gleichzeitig aber auch wichtige Informationen zu Sedimentbelastungen und -Einträgen und damit einen wichtigen Beitrag als Entscheidungsunterstützung im Rahmen eines Sedimentmanagementplans

Reservoir sediment flushing is increasingly considered beneficial to reduce sedimentation of reservoirs and maintain sediment supply downstream of impounded rivers. Nevertheless, flushing of the accumulated sediments downstream of the dam also bears numerous negative impacts. In this study, first the most important downstream impacts of fine sediment releases of flushing were identified based on previously published research of twenty case studies in eleven countries. The results showed that the long-term as well as short term biological and physical impacts decreased with distance from the dam. The temporal scale of impacts on macro-invertebrates could span from few weeks or a month to several months while the effect on fish could last for a number of years. The impacts on downstream vegetation dynamics is driven by many years of flushing activities. The study also enabled proposing generic management strategies aimed to reduce the impacts. Second, fine sediment transport in coarse immobile bed, which is a common phenomenon downstream of dams during flushing releases, dam removal and also in many mountain and canyon rivers, was investigated. Particularly, the dynamics of the downstream erosion and transport of fine sediments released during sediment flushing was investigated based on a series of flume experiments that were carried out in immobile gravel bed and using a one-dimensional (1-D) suspended sediment transport model developed in the present study. In the framework of the flume experiment, firstly gravel bed roughness, porosity and roughness density were exclusively extracted from gravel surface elevation data in which developing a spatial filter to overcome elevation errors was carried out. Secondly a new technique to acquire fine sediment erosion in immobile coarse bed in running water condition was developed. The method proved to be the back bone of all fine sediment erosion experiments conducted in the present study and could be used for similar studies. This study presents a first work of direct measurement of erosion rate and characterizing its spatial heterogeneity in gravel bed. The experimental data of erosion rate of fine sediments showed that it varied spatially with high erosion rate on the stoss side of gravels and less on the lee side conforming to sweeps and ejections characteristics in coherent flow structure of gravel bed flows. Erosion rate was significantly affected by increase in roughness of immobile gravel bed with high erosion rate noticed when sand level was reduced although the effect on stream-wise velocity was not significant. The vertical profile of erosion rate was found to decrease linearly and showed an exponential decay in time in the gravel matrix. Third, a new non-equilibrium erosion rate relation is proposed. Drag force profile in the interfacial sublayer of clean gravel bed was found to be scaled well with roughness density and allowed predicting the effective shear stress distribution available for fine sediment entrainment with an empirical equation. vi The new relation is a modified version of the pick-up rate function of van Rijn (1984b) in which the predicted shear stress in the roughness layer was implemented. The most important finding was that if the shear stress distribution in the interfacial sublayer is predicted, a relation for sand bed condition can be applied to predict fine sediment erosion rate in immobile gravel bed. This approach is conceptually superior to previous approaches where erosion rate in sand bed condition was scaled empirically for various fine sediment bed level within the interfacial sublayer. Finally, the effect of the interaction between hydrodynamic and sediment wave dynamics of sediment flushing on spatial pattern of sediment deposition was investigated. The 1-D model was developed to include major processes observed in sediment flushing: sediment wave celerity correction, variable bed roughness, bed exchange in immobile bed, hindered settling velocity and rough bed porosity. The proposed erosion rate relation showed encouraging results when implemented in the 1-D model. The wave celerity factor did not show significant effect on the spatial lag in immobile bed condition although was significant in sand bed condition. Variable bed roughness modified both the flow field and sediment deposition in which larger length of sediment deposit was noted. The immobile bed porosity allowed modelling clogged depth of fine sediments. The model was also found to be very valuable to investigate flushing scenarios that reduce significant deposition through the analysis of the dependence of deposition on peak-to-base flow and intermittence of releases. The highest peak-to-base flows produced the longest and thickest region of deposition while those with the lowest ratio produced the shortest and thinnest. A single flushing release followed by clear water release reduced area or length of sediment deposition more than intermittent flushing followed by inter- and post-flushing clear water releases. In the latter case, the peak of concentration reduced but remained higher for longer duration than the former, which suggests that a large quantity of clear water release has to be available. Overall, the present research represents a step forward in understanding relevant processes involved in the downstream transport of fine sediments released during sediment flushing and the associated impacts that can help the development of better management strategies and predictive tools.

Reservoir sediment flushing is increasingly considered beneficial to reduce sedimentation of reservoirs and maintain sediment supply downstream of impounded rivers. Nevertheless, flushing of the accumulated sediments downstream of the dam also bears numerous negative impacts. In this study, first the most important downstream impacts of fine sediment releases of flushing were identified based on previously published research of twenty case studies in eleven countries. The results showed that the long-term as well as short term biological and physical impacts decreased with distance from the dam. The temporal scale of impacts on macro-invertebrates could span from few weeks or a month to several months while the effect on fish could last for a number of years. The impacts on downstream vegetation dynamics is driven by many years of flushing activities. The study also enabled proposing generic management strategies aimed to reduce the impacts. Second, fine sediment transport in coarse immobile bed, which is a common phenomenon downstream of dams during flushing releases, dam removal and also in many mountain and canyon rivers, was investigated. Particularly, the dynamics of the downstream erosion and transport of fine sediments released during sediment flushing was investigated based on a series of flume experiments that were carried out in immobile gravel bed and using a one-dimensional (1-D) suspended sediment transport model developed in the present study. In the framework of the flume experiment, firstly gravel bed roughness, porosity and roughness density were exclusively extracted from gravel surface elevation data in which developing a spatial filter to overcome elevation errors was carried out. Secondly a new technique to acquire fine sediment erosion in immobile coarse bed in running water condition was developed. The method proved to be the back bone of all fine sediment erosion experiments conducted in the present study and could be used for similar studies. This study presents a first work of direct measurement of erosion rate and characterizing its spatial heterogeneity in gravel bed. The experimental data of erosion rate of fine sediments showed that it varied spatially with high erosion rate on the stoss side of gravels and less on the lee side conforming to sweeps and ejections characteristics in coherent flow structure of gravel bed flows. Erosion rate was significantly affected by increase in roughness of immobile gravel bed with high erosion rate noticed when sand level was reduced although the effect on stream-wise velocity was not significant. The vertical profile of erosion rate was found to decrease linearly and showed an exponential decay in time in the gravel matrix. Third, a new non-equilibrium erosion rate relation is proposed. Drag force profile in the interfacial sublayer of clean gravel bed was found to be scaled well with roughness density and allowed predicting the effective shear stress distribution available for fine sediment entrainment with an empirical equation. The new relation is a modified version of the pick-up rate function of van Rijn (1984b) in which the predicted shear stress in the roughness layer was implemented. The most important finding was that if the shear stress distribution in the interfacial sublayer is predicted, a relation for sand bed condition can be applied to predict fine sediment erosion rate in immobile gravel bed. This approach is conceptually superior to previous approaches where erosion rate in sand bed condition was scaled empirically for various fine sediment bed level within the interfacial sublayer. Finally, the effect of the interaction between hydrodynamic and sediment wave dynamics of sediment flushing on spatial pattern of sediment deposition was investigated. The 1-D model was developed to include major processes observed in sediment flushing: sediment wave celerity correction, variable bed roughness, bed exchange in immobile bed, hindered settling velocity and rough bed porosity. The proposed erosion rate relation showed encouraging results when implemented in the 1-D model. The wave celerity factor did not show significant effect on the spatial lag in immobile bed condition although was significant in sand bed condition. Variable bed roughness modified both the flow field and sediment deposition in which larger length of sediment deposit was noted. The immobile bed porosity allowed modelling clogged depth of fine sediments. The model was also found to be very valuable to investigate flushing scenarios that reduce significant deposition through the analysis of the dependence of deposition on peak-to-base flow and intermittence of releases. The highest peak-to-base flows produced the longest and thickest region of deposition while those with the lowest ratio produced the shortest and thinnest. A single flushing release followed by clear water release reduced area or length of sediment deposition more than intermittent flushing followed by inter- and post-flushing clear water releases. In the latter case, the peak of concentration reduced but remained higher for longer duration than the former, which suggests that a large quantity of clear water release has to be available. Overall, the present research represents a step forward in understanding relevant processes involved in the downstream transport of fine sediments released during sediment flushing and the associated impacts that can help the development of better management strategies and predictive tools.

Reservoir sediment flushing is increasingly considered beneficial to reduce sedimentation of reservoirs and maintain sediment supply downstream of impounded rivers. Nevertheless, flushing of the accumulated sediments downstream of the dam also bears numerous negative impacts. In this study, first the most important downstream impacts of fine sediment releases of flushing were identified based on previously published research of twenty case studies in eleven countries. The results showed that the long-term as well as short term biological and physical impacts decreased with distance from the dam. The temporal scale of impacts on macro-invertebrates could span from few weeks or a month to several months while the effect on fish could last for a number of years. The impacts on downstream vegetation dynamics is driven by many years of flushing activities. The study also enabled proposing generic management strategies aimed to reduce the impacts. Second, fine sediment transport in coarse immobile bed, which is a common phenomenon downstream of dams during flushing releases, dam removal and also in many mountain and canyon rivers, was investigated. Particularly, the dynamics of the downstream erosion and transport of fine sediments released during sediment flushing was investigated based on a series of flume experiments that were carried out in immobile gravel bed and using a one-dimensional (1-D) suspended sediment transport model developed in the present study. In the framework of the flume experiment, firstly gravel bed roughness, porosity and roughness density were exclusively extracted from gravel surface elevation data in which developing a spatial filter to overcome elevation errors was carried out. Secondly a new technique to acquire fine sediment erosion in immobile coarse bed in running water condition was developed. The method proved to be the back bone of all fine sediment erosion experiments conducted in the present study and could be used for similar studies. This study presents a first work of direct measurement of erosion rate and characterizing its spatial heterogeneity in gravel bed. The experimental data of erosion rate of fine sediments showed that it varied spatially with high erosion rate on the stoss side of gravels and less on the lee side conforming to sweeps and ejections characteristics in coherent flow structure of gravel bed flows. Erosion rate was significantly affected by increase in roughness of immobile gravel bed with high erosion rate noticed when sand level was reduced although the effect on stream-wise velocity was not significant. The vertical profile of erosion rate was found to decrease linearly and showed an exponential decay in time in the gravel matrix. Third, a new non-equilibrium erosion rate relation is proposed. Drag force profile in the interfacial sublayer of clean gravel bed was found to be scaled well with roughness density and allowed predicting the effective shear stress distribution available for fine sediment entrainment with an empirical equation. The new relation is a modified version of the pick-up rate function of van Rijn (1984b) in which the predicted shear stress in the roughness layer was implemented. The most important finding was that if the shear stress distribution in the interfacial sublayer is predicted, a relation for sand bed condition can be applied to predict fine sediment erosion rate in immobile gravel bed. This approach is conceptually superior to previous approaches where erosion rate in sand bed condition was scaled empirically for various fine sediment bed level within the interfacial sublayer. Finally, the effect of the interaction between hydrodynamic and sediment wave dynamics of sediment flushing on spatial pattern of sediment deposition was investigated. The 1-D model was developed to include major processes observed in sediment flushing: sediment wave celerity correction, variable bed roughness, bed exchange in immobile bed, hindered settling velocity and rough bed porosity. The proposed erosion rate relation showed encouraging results when implemented in the 1-D model. The wave celerity factor did not show significant effect on the spatial lag in immobile bed condition although was significant in sand bed condition. Variable bed roughness modified both the flow field and sediment deposition in which larger length of sediment deposit was noted. The immobile bed porosity allowed modelling clogged depth of fine sediments. The model was also found to be very valuable to investigate flushing scenarios that reduce significant deposition through the analysis of the dependence of deposition on peak-to-base flow and intermittence of releases. The highest peak-to-base flows produced the longest and thickest region of deposition while those with the lowest ratio produced the shortest and thinnest. A single flushing release followed by clear water release reduced area or length of sediment deposition more than intermittent flushing followed by inter- and post-flushing clear water releases. In the latter case, the peak of concentration reduced but remained higher for longer duration than the former, which suggests that a large quantity of clear water release has to be available. Overall, the present research represents a step forward in understanding relevant processes involved in the downstream transport of fine sediments released during sediment flushing and the associated impacts that can help the development of better management strategies and predictive tools.

[Truncated abstract] With rapidly increasing population densities along coastlines and rising global sea levels, coastal protection has become a major concern for coastal communities. Predicting sediment transport in nearshore regions, however, is one of the most challenging tasks faced by coastal researchers in designing coastal structures or beach nourishment schemes. Although nearshore sediment transport mainly occurs in the longshore direction, cross-shore sediment transport is crucial in determining the shoreline evolution and beach morphology . . . This study investigated the factors influencing sediment re-suspension and cross-shore suspended sediment flux in the frequency domain through a series of field measurements conducted at several different locations and a numerical model. Only oscillatory flow components were examined and the mean flow components were not considered. Although many different factors such as cross-shore location with respect to breaker line, significant wave height to water depth ratio (Hs/h), normalised horizontal velocity skewness (/‹u²›³/²), median grain size (d50), breaker type, and wave groupiness appeared to influence the magnitude of cross-shore suspended sediment flux, bed ripples was identified as the major contributing factor in changing the direction of suspended sediment flux due to incident swell waves. Moreover, the direction changed significantly with ripple type. High frequency measurements, obtained to examine the influence of turbulent kinetic energy (TKE) on higher sediment suspension events observed under wave groups indicated that higher TKE was generated at the seabed by approaching wave groups, which in turn resulted in higher suspension events.°1

Bottom water hypoxia and its influence on the environment have been topics of increasing concern for many coastal regions. This research addresses both spatial and temporal variability in sediment biogeochemistry at the southeastern region of Corpus Christi Bay, TX, where seasonal (summer) hypoxia occurs. Traditional techniques for determination of a variety of dissolved and solid components, benthic oxygen demand, and sulfate reduction rates were augmented by measurements using solid state microelectrodes to simultaneously determine concentrations of dissolved O2, Mn2+, Fe2+, and [sigma]H2S in multiple small - interval (1 mm) depth profiles of sediment microcosms. Oxygen concentrations in the overlying water were manipulated in the sediment microcosms and electrode depth profile measurements were made over ~ 500 hours of experimentation. Laboratory and field microelectrode results were in good agreement for both norm - oxic and anoxic time periods. Results indicated that iron (Fe2+) and sulfide ([sigma]H2S) were the redox reactive species in these sediments. During hypoxic conditions an upward migration of dissolved Fe2+and [sigma]H2S through the sediment column and, at times, into the overlying water was observed as the dissolved oxygen concentrations decreased. A corresponding decline in the vertical extent of these redox species occurred when the overlying water was re-oxidized. When both dissolved iron and sulfide coexisted, FeS minerals were formed in the sediment, preventing sulfide diffusion into the overlying water. However, after a long duration of hypoxia (> 200 hours) this buffering capacity was exceeded and both iron and sulfide penetrated into the overlying waters. Results indicated that iron may have a greater influence on hypoxia than sulfide because its concentration in the overlying waters during induced hypoxia was an order of magnitude greater than those of sulfide. Moreover, in the southeastern region of the Bay, where mixing was minimal and the water column was shallow, the sediments alone may have caused the onset of the hypoxic event in a relatively short time period (< 5.5 days). These results demonstrated that in shallow marine environments where seasonal hypoxia occurs, such as Corpus Christi Bay, the associated major changes that take place in the sediment biogeochemistry must be included in benthic - pelagic models for overlying water hypoxia.

Os sedimentos marinhos são receptores finais de vários compostos da coluna de água, possuindo uma participação ativa nos ciclos biogeoquímicos. Comunidades microbianas possuem um papel crucial nestes ciclos, sendo responsáveis por grande parte da remineralização da matéria orgânica em sedimentos superficiais. Foram realizados dois experimentos com simulações de processos oceanográficos em microcosmos: Enriquecimento Orgânico, testando a diferença entre a chegada de fitoflagelados e diatomáceas no sedimento e Ressuspensão, simulando a passagem de frente fria. Foram analisados os compostos referentes à qualidade e quantidade da matéria orgânica sedimentar, assim como o fluxo de nutrientes da interface água-sedimento. No Experimento Enriquecimento, as diferentes algas causaram respostas distintas nos processos de degradação da matéria orgânica, aumentando a qualidade e o metabolismo das comunidades presentes, além de modificar os fluxos de nutrientes, sendo notada uma resposta mais rápida nos mecanismos de degradação devido à adição do fitoflagelados. No Experimento Ressuspensão, o distúrbio físico ocasionou uma resposta imediata e significativa na liberação dos nutrientes do sedimento para a interface água-sedimento e alterações nas concentrações de ácidos graxos, principalmente nos dois primeiros dias após a simulação. Logo, os diferentes eventos oceanográficos simulados comprovaram sua influência frente aos processos biogeoquímicos, principalmente na disponibilidade de ácidos graxos e na liberação de nutrientes para a água sobrejacente
Marine sediments are the final receivers of many organic compounds from the water column, playing an important role in biogeochemical cycles. Microbial communities are important to these cycles as they remineralize organic matter within surface sediments. Microcosm experiments were conducted to simulate two important oceanographic processes: Organic Enrichment, to test differences between sinking patterns of phytoflagellates and diatoms and Resuspension, simulating the passage of a cold front. The quality and amount of the organic matter was assessed, as well as the nutrient flow between the sediment-water interface. In the Enrichment Experiment, distinctive responses in the degradation processes were noted between treatments where the addition of phytoflagellates increased the quality of the organic matter, caused faster metabolism communities present in the sediment, and modify the patterns of nutrient flux rates. In the Resuspension Experiment, the physical disturbance caused an immediate and significant release of nutrients from the sediment to the sediment-water interface and changed the in the concentrations of fatty acid content most notably during two days after the resuspension event. Thus, the different simulated oceanographic events influenced biogeochemical processes, particularly in the availability of fatty acids and the release of nutrients to the overlying water

In 2016 the Panama Canal expansion is set to open, allowing a new class of ships to call on east coast ports. The dredging involved in deepening navigation channels to ensure safe passage of these vessels will place an increased amount of pressure on containment facilities up and down the coast. With limited disposal space, and increasing volumes, many ports have begun to rethink the treatment of this excess material. This thesis explores the prospect of dredge material being more than engineered fill. It suggests that dredge processing can become the basis for a new form of productive recreational landscape, one that can engage the public in a conversation of the spatial and material operations that sustain our lives. It works blur and dissolve the boundaries that have been erected between working landscapes and the public realm, and seeks to create a landscape that establishes a new sense of place prepared to mark the future of the new working urban waterfront; one where industrial operations generate new ecological substrates, and where productive frameworks become recreation networks.
Master of Landscape Architecture

Three separate but related aspects of sediment allocation in a river/estuarine system were examined. The main purpose was to compare sediment budgets for a series of eleven nested sub-watersheds as a function of watershed size, ranging from 65 to 6900 km2. The approach quantified six budget components: upland erosion; stream bank erosion; colluvial storage; wetland storage; stream channel erosion and storage; and sediment flux at the outlets. Three budgets were developed for each sub-watershed to examine the relative proportions of budget components, budget sensitivity (the influence of individual components on the overall budget), and the uncertainty of budget components. The study area was the rural, forested, low relief York River watershed in southeastern Virginia. The relative proportions of budget components do not change with sub-watershed size. Budgets are more influenced by the tributary system than by the sub-watershed size. The budget is sensitive to most components because they are large in size and are highly variable. The uncertainties of budget components are proportional to the magnitude of the best estimates. Management efforts should focus on locally-derived sediment to improve water quality because little sediment from the upper parts of the watershed reaches the estuary. Sediment loads were needed in the sediment budgets for three estuarine sampling stations. The loads were estimated by separating the gravitational circulation, tidal pumping, and river input components of long-term total suspended solids data. The load for the station closest to the river mouth was somewhat larger than literature values. The contribution to the estuary of the two tributary stations was previously unknown. Tidal pumping, rather than gravitational circulation, is the dominant process moving suspended sediment up the estuary. The potential supply and storage of sediment in wetlands at the watershed level was examined by quantifying the areal extent of wetland type and location in the watershed, and surrounding land use, slope, and soil type. Results showed that these landscape characteristics are unevenly distributed within the York River watershed and its subdivisions. The differences in landscape characteristics between subdivisions suggest that wetland performance and its impact on water quality may vary within a watershed. Separate management approaches may be needed to accommodate these differences.

Aquesta tesi estudia la dinàmica hidro-sedimentària de rius mediterranis, tant ‘naturals’ com regulats per preses. Amb aquest objectiu, s’ha realizat un estudi a escala multi-temporal i multi-espacial, que inclou treball de camp en trams de riu representatius, l’anàlisi de dades a nivell de conca, i experiments en canals de laboratori. L’alteració hidrològica aigües avall dels embassaments s’ha observat a diferents escales temporals, afectant notablement la magnitud i freqüència de les crescudes. A nivell sedimentari, s’observa un dèficit de sediments, fet que facilita l’establiment de biofilm i que, a la vegada, afavoreix l’estabilització del llit del riu. A més, l’emmagatzematge temporal de sediments a la llera modula el balanç i regula l’entrada de sediments en embassaments. La tesi mostra els efectes d’un conjunt d’activitats antròpiques en procesos fluvials i com això altera les interaccions bio-físiques del riu, i posa èmfasi en la necessitat d’una gestió contínua per la preservació dels ecosistemes fluvials.
Esta tesis estudia la dinámica hidro-sedimentaria de ríos mediterráneos, tanto ‘naturales’ como regulados por presas. Con este objetivo, se ha realizado un estudio a escala multi-temporal y multi-espacial, que incluye trabajo de campo en tramos de río representativos, análisis de datos a nivel de cuenca, y experimentos en canales de laboratorio. La alteración hidrológica aguas abajo de los embalses se ha observado a diferentes escalas temporales, afectando notablemente la magnitud y frecuencia de las crecidas. A nivel sedimentario, se observa un déficit de sedimentos, lo que facilita el establecimiento de biofilm y, a la vez, favorece la estabilización del lecho del río. Además, el almacenamiento temporal de sedimentos en el lecho modula el balance y regula la entrada de sedimentos en embalses. La tesis muestra los efectos de un conjunto de actividades antrópicas en procesos fluviales y en la alteración en las interacciones bio-físicas del río, y enfatiza la necesidad de una gestión continua para la preservación de los ecosistemas fluviales.
This PhD thesis studies hydro-sedimentary dynamics in Mediterranean rivers, both in ‘natural’ and in dammed rivers. For this purpose, a multi-temporal and spatial research was carried out, including field measurements in representative river reaches, data analysis at the basin scale, and experiments in artificial streams. The hydrological alteration downstream from dams was documented at different temporal scales, notably affecting the magnitude and frequency of floods. Regarding sediments, a severe deficit was observed below dams, a fact that facilitates the establishment of biofilm which, in turn, favours river bed stabilisation. Moreover, the study shows how in-channel storage influences the river sediment budget and regulates sediment input in reservoirs. The thesis examines the effects of a suit of human activities on fluvial processes and how this alter rivers’ bio-physical interactions, and emphasises the need of continuous monitoring of all these processes to achieve a sound management of fluvial ecosystems.

GONÇALVES, Jeamylle Nilin. Avaliação da qualidade do sedimento do estuário do rio Ceará. 2008. 93 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Engenharia de Pesca, Fortaleza-CE, 2008
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The evaluation of sediment quality has been seen as a consistent and necessary extension of assessment programmes for water resources. Sediments are the most concerning of the compartments due characteristics that favour the deposition and accumulation of contaminants. Previous studies showed that the estuary of Ceará River is suffering contamination by industrial and domestic effluents, and that toxicity was observed in embryos of sea urchin exposed to water of the estuary. The objective of the present study was to evaluate the environmental quality of sediment samples from the estuary of Ceará River, through sediment characterization, quantification of metals and bioassays in several compartments of the sediment. Three Campaigns were conducted (Oct/06, Jan/07 and May/07) at four stations along the estuary. As reference, sediments of the estuaries of Malcozinhado and Pacoti rivers were sampled. Analysis of granulometry, carbonate, organic matter and of the metals Zn, Cu, Pb and Cr served to characterize the stations. Toxicity of the whole sediment was evaluated in bioassays with the amphipod Tiburonella viscana and the copepod Nitokra sp.; whilst embryos of the sea urchin Lytechinus variegatus were used in tests at the interface sediment/water and with aqueous elutriates. The characterization of the toxicity of elutriates was accomplished through chemical and physical manipulation for the Evaluation and Identification of Toxicity (TIE). We observed a gradient on percentages of mud, organic matter and metals with values decreasing toward the mouth. In general, the samples from the estuary of Ceará River were toxic on all routes of exposure. The test with amphipods showed good reproducibility, whilst the reproduction of copepods showed large variations in the control, amongst the campaigns. Toxicity was high for both tests with sea urchin embryos. Ammonia seems to have contributed to the toxicity observed in samples of elutriate, however, manipulation of addition of EDTA, Sodium thiosulfate, aeration, filtration and the macroalgae Ulva sp. reduced the toxicity. This suggests that apart from ammonia, other factors such as metals, and oxidizable volatile and particulated compounds contribute to the toxicity. Linear correlation and principal components analysis between abiotic parameters, metals and toxicity demonstrated that the parameters investigated do not fully explain the toxicity observed in this study. Despite the values of metals found in the Ceará River were low relative to other impacted estuaries, high levels of toxicity were identified in samples of sediment from the region
A avaliação da qualidade do sedimento tem sido vista como a extensão coerente e necessária de programas de avaliação dos recursos aquáticos. Os sedimentos apresentam-se como o mais preocupante dos compartimentos devido às características que favorecem a deposição e acúmulo de contaminantes. Estudos anteriores mostraram que o estuário do rio Ceará vem sofrendo contaminação por efluentes industriais e domésticos e que foi observada toxicidade a embriões de ouriço do mar expostos as águas do estuário. O objetivo do presente trabalho foi avaliar a qualidade ambiental de amostras de sedimento do estuário do Rio Ceará, através de análises sedimentológicas, quantificação de metais e através de bioensaios em vários compartimentos do sedimento. Foram realizadas três Campanhas (Out/06, Jan/07 e Mai/07) em quatros estações ao longo do estuário. Como local de referência foram amostrados sedimentos dos estuários dos rios Malcozinhado e Pacoti. Análises de granulometria, carbonatos, matéria orgânica e ainda a análise de Zn, Cu, Pb e Cr serviram para caracterizar as estações. A toxicidade do sedimento integral foi avaliada em bioensaios com o anfípodo Tiburonella viscana e o copépodo Nitokra sp.; enquanto que embriões do ouriço do mar Lytechinus variegatus foram utilizados em testes na interface sedimento/água e com elutriatos. A caracterização da toxicidade de elutriatos foi realizada através de manipulações físicas e químicas para Avaliação e Identificação de Toxicidade (AIT). Foi observado um gradiente em relação às porcentagens de finos, matéria orgânica e metais com valores decrescendo na direção da foz. De forma geral, as amostras coletadas no estuário do rio Ceará foram tóxicas em todas as rotas de exposição. O teste com anfípodos mostrou boa reprodutibilidade, enquanto que a reprodução de copépodos teve grandes variações no controle, entre as Campanhas. Para ambos os testes com embriões de ouriço do mar, a toxicidade foi elevada. A amônia parece ter contribuído para toxicidade observada em amostras de elutriato, contudo manipulações de adição de EDTA, Tiossulfato de sódio, aeração, filtração e Ulva sp. reduziram a toxicidade das amostras sugerindo que além da amônia, metais, compostos oxidáveis, voláteis e particulados contribuam para a toxicidade. A correlação linear e a análise dos componentes principais entre os parâmetros abióticos, metais e toxicidade demonstraram que os parâmetros pesquisados não explicam totalmente a toxicidade observada nesse estudo. E apesar dos valores de metais encontrados no rio Ceará serem baixos em relação a outros estuários impactados, níveis elevados de toxicidade foram identificados em amostras de sedimento da região.

Thesis (M.S.)--University of Nevada, Reno, 20007.
"December 2007." Includes bibliographical references (leaves 122-124). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

Detailed knowledge from physical properties of sediment such as erosion and settling velocity are crucial for modelling as well as for water protection planning and management. The main purpose of this research was to determine the critical shear stress (τcr) and settling velocity of the organic sediments in different peatland drainage areas and headwaters in Finland. Further, KINEROS2 erosion model was applied to peatland forestry and peat extraction conditions to simulate runoff hydrograph and suspended solid yield from two experimental catchments. To determine mean τcr and settling velocity totally 119 undisturbed sediment samples were taken from the natural streams, ditches and brooks across Finland. The samples covered main peatland uses, peatland forestry and peat extraction sites. Furthermore, to determine the effect of peat soil properties on sediment erosion and settling, peat soil samples were collected from 9 peat extraction areas. These samples were used to prepare sediments in laboratory setting. Cohesive strength meter (CSM) was applied to measure the τcr and settling velocity in laboratory and in-situ conditions. Results were compared against physical properties of sediment or peat soils and further compared against different peatland uses. The critical shear stress over all samples ranged from 0.0057 to 0.428 N m⁻² (mean value 0.116 ± 0.07 N m⁻²). τcr in peatland forestry ditches ranged from 0.0057 to 0.428 N m⁻² (mean value 0.07 ± 0.1 N m⁻²), and in peat extraction sites from 0.006 to 0.421 N m⁻² (mean value 0.12 ± 0.06 N m⁻²). Similarly, τcr of artificially prepared samples from peat extraction area ranged from 0.012 to 0.112 N m⁻² (mean value of 0.059 ± 0.028 N m⁻²). At Koivupuro peatland forestry site, measurements were done in laboratory as well as in-situ. Results gave slightly different values; in-situ τcr ranged from 0.005 to 0.305 N m⁻² with the mean value of 0.03 ± 0.075 N m⁻², and the laboratory results ranged from 0.008 to 0.310 N m⁻² with the mean value of 0.125 ± 0.06 N m⁻². Degree of humification (DOH) and dry bulk density were found to be positively related to critical shear stress. The settling velocity results for Koivupuro catchment ranged from 0.0004 to 0.131 m h⁻¹ (mean value 0.016 ± 0.034 m h⁻¹) and 0.0004 to 0.456 m h⁻¹ (mean value 0.144 ± 0.134 m h⁻¹) for other organic peat samples. Degree of humification (DOH) and settling velocity showed no correlation while dry density of settled sediment was found inversely proportional to settling velocity. This study showed that CSM can be used to determine τcr and settling velocity from organic sediment samples. Results can be applied in modelling purposes, and in dimensioning of water protection methods such as settling basins. Eleven rainfall-runoff events from two different catchments were selected for the study to simulate runoff hydrographs and associated sediment yields in different conditions. When properly calibrated for each event, KINEROS2 model produced sufficient estimations of runoff hydrographs for peatland forestry and peat extraction sites but failed to produce reliable estimations of suspended sediment yields. Moreover, unrealistic parameter values sometimes had to be used in model calibration due to model inability to simulate groundwater or soil water response in ditch flow. Thus the model could not be validated for varying initial conditions and rainfall events.

A method to infer sediment concentrations from acoustic backscatter levels has been implemented for a prototype acoustic sediment flux probe. This required calibrations of the acoustic transceiver systems and direct measurements of the system response to typical sediment size distributions over a wide range of concentrations. The sensitivities of the 1.3 MHz and 5.2 MHz transducers of an acoustic sediment probe were measured using the backscatter amplitudes from stainless steel wires of four different radii. A two-frequency inversion algorithm estimating the geometric mean radius and variance about the mean of suspended sediment with an assumed lognormal size distribution and the sediment mass concentration was developed and tested in a laboratory setting. The sensitivity of the 5.2 MHz transducer for each wire was consistent within 10%. The sensitivity of the 1.3 MHz transducer calculated for each wire was not consistent and is believed to be due to a strong angular dependence between the wire orientation and the 1.3 MHz transducer face. The sensitivities of each of the four transducers were, however, inferred from the system's response to the controlled sediment backscatter measurements.

U radu je ispitana distribucija metala u sistemu sediment/voda na najugroženijim vodotocima uAP Vojvodini. Na osnovu dobivenih podataka urađena je procena rizika na osnovu analizeporne vode, kiselog volatilnog sulfida i simultano ekstrahovanih metala i sekvencijalneekstrakcione procedure. Procena mobilnosti metala u sistemu sediment/voda određena jepromenom fizičko-hemijskih uslova u realnom sistemu (vodotok) i u laboratorijskim uslovima.Ispitana je efikasnost in-situ (aeracijom sistema sediment/voda) i ex-situ remedijacijesedimenta metodama termičkog tretmana i solidifikacije/stabilizacije.Rezultati su ukazali da u svakom vodotoku i zaštićenoj zoni postoji lokacija u kojoj je sedimentbarem po jednom metalu klasifikovan (holandski sistem klasifikacije sedimenata) kao zagađen(klasa 3) ili izuzetno zagađen sediment (klasa 4). Generalno, kvalitet sedimenta manjihvodotoka (Krivaja, Nadela, Kudoš, Veliki Bački kanal i Begej) je lošiji u odnosu na ostaleispitivane vodotoke.Procena dostupnosti metala u sedimentu Velikog Bačkog kanala ukazala je da na svakomispitivanom profilu postoji minimum jedan metal i jedna metoda koja definiše sediment kaovisoko rizičan. Takođe je zaključeno da je sediment na delu od 2+000 do 4+900 km zagađeniji,jer postoji veći broj metala i metoda koji ga definišu kao visoko rizičnim. Ovako dobijenirezultati ukazuju da nije dovoljan jednostavan i samo jedan pristup u oceni kvaliteta sedimentai proceni rizika koji metali mogu da ispolje u akvatičnom ekosistemu.Ukazano je da pomeranje sedimenta (npr. otvaranja ustave), dovodi do promene fizičkohemijskihuslova u sistemu sediment/voda, resuspenzije i transporta sedimenta. Usled ovihpromena povećava se dostupnost metala i dolazi do povećanja njihove koncentracije u vodenojfazi čime se znatno povećava rizik i mogućnost ispoljavanja negativnih efekata na akvatičniekosistem.U slučaju resuspenzije sedimenta u sistemu sediment/voda pronađena je zavisnost izmeđukoncentracije metala u suspendovanim materijama i vodi od sadržaja određenih frakcija ususpendovanim materijama (sadržaj organskih materija i frakcije do 63 μm).Remedijacione tehnike često su ekonomski neprihvatljive zbog velike zapremine zagađenogsedimenta. Ukazano je da primena in-situ aeracije, omogućava smanjenje količine sedimenta(čime se smanjuju troškovi eventualno naknadnog tretmana sedimenta), a da je tretmansolidifikacije/stabilizacije sedimenta sa glinom i termičke remedijacije zadovoljavjući saaspekta izluživanja metala. Dobijeni rezultati izvedenih testova izluživanja ukazali su namoguću primenu ovih tretmana u pogledu rešavanja problema sedimenta koji je zagađenmetalima, bilo u pogledu sigurnog odlaganja na deponiju ili u smislu njegove upotrebe kaododatka pri proizvodnji građevinskog materijala (opeke), osnove za puteve, uređenje obale(nasipa) itd. Na taj način mogu se znatno umanjiti troškovi izmuljivanja i manipulacijekontaminiranog sedimenta, a sama remedijacija učiniti mnogo prihvatljivijom
This work investigates the distribution of metals in the sediment / water systems of the most endangered rivers in Vojvodina. Utilizing the data obtained, risk assessments are carried out based on analysis of pore water, acidic volatile sulphides and simultaneously extracted metals and sequential extraction procedure. The assessment of metal mobility in the sediment / water system is determined by the changing physical and chemical conditions in real systems (waterways) and under laboratory conditions. The effectiveness of in-situ (aeration of sediment / water) and ex-situ remediation of sediment by thermal treatment methods and solidification / stabilization are investigated. The results show that in each waterbody and protected area, certain locations have sediment which for at least one metal, is classified (by the Dutch system of sediment classification ) as polluted (class 3) or highly polluted (class 4). In general, the quality of sediment in smaller rivers (Krivaja, Nadela, Kudoš, Veliki Bački canal and Begej) is inferior to the other rivers studied. Assessment of the metals availability in the sediments of the Veliki Bački canal indicates that in each profile examined, at least one metal and one method defines the sediment as very hazardous. It is also shown that the sediment at the section from 2 +000 to 4 +900 km is the most polluted, with a number of metals and methods that define it as a high risk. The results indicate that it is inadequate to have a simple singular approach to sediment quality assessment and the assessment of the risks posed by metals detected in aquatic ecosystems. This work shows that sediment movement (e.g. from opening a sluice gate) leads to changes in the physical-chemical conditions of the sediment / water system, with resuspension and sediment transport. These changes increase metals availability and increase their concentrations in the aqueous phase, significantly increasing the posed risk and the possibility of adverse effects on aquatic ecosystems. In the case of sediment resuspension in the sediment / water system, a relationship was found between the concentration of metals in suspended matter and the concentration in the water for certain fractions of suspended matter (organic matter content and the fraction up to 63 μm). Remediation techniques are often not economically viable due to the large volume of contaminated sediments involved. It is shown that the implementation of in-situ aeration reduces the amount of sediment (which reduces the costs of subsequent sediment treatment), and that solidification / stabilization treatment with clay and thermal remediation results in satisfactory remediation with respect to metals leaching. Leaching test results show the potential of these treatments to solve the problem of sediments which are contaminated with metals, either in terms of safe disposal in landfill or in terms of its use as a supplement in the production of building materials (brick), as road foundation, or for river bank reinforcement (dams), etc.. Thus, the costs of dredging and manipulating contaminated sediments can be significantly reduced, making remediation itself much more applicable.

A erosão do solo tem sido extensamente estudada dentro do ponto de vista agrícola, pois está relacionada a sérias perdas em termos de produtividade das mais variadas culturas e conseqüentemente, é causa de prejuízos econômicos. Recentemente tem-se dado atenção especial aos problemas ambientais relacionados à erosão, transporte e deposição de sedimentos, já que são, provavelmente, os mais significativos de todos os poluentes em termos de sua concentração na água e dos seus impactos e efeitos no transporte de substâncias químicas, entre elas o nitrogênio aplicado na forma de fertilizantes. O foco central do presente trabalho foi a investigação dos padrões de transporte de sedimentos por erosão hídrica e suas influências na transferência de nitrogênio aos cursos d\'água. A fonte de nitrogênio avaliada foi o sulfato de amônio aplicado superficialmente como fertilizante em um latossolo vermelho amarelo, em diferentes preparos do solo, sem cobertura vegetal e sob chuva simulada em diferentes intensidades. Os resultados permitiram identificar a fração argilosa dos sedimentos erodidos transportados em suspensão na água da enxurrada como a principal via de transporte/transferência de nitrogênio proveniente do fertilizante. Este processo de transferência deu-se mais intensamente nas primeiras chuvas. Constatou-se que os valores de perdas de solo e água não influenciam a capacidade de transporte de nitrogênio entre a área de cultivo e os cursos d\'água. O preparo do solo influenciou as concentrações de nitrogênio transportadas pela enxurrada. As concentrações de nitrogênio nos sedimentos são altas mesmo com baixo volume e intensidade de chuva.
Soil erosion has been extensively studied from the agricultural point of view, because it is related with serious damages in terms of a huge variety of plantations productivity and its consequent economic detriments. Currently, special attention is given to the environmental problems caused by erosion processes and the transport and deposition of the sediments, since they are, probably, the most significant pollutants in terms of its concentration in the water and its impacts and effects in the chemical substances transport, such as nitrogen which is applied in the form of fertilizer. The central focus of the present work was the research of the standards sediment transport origined by the water erosion and their influences in the transference of nitrogen to the water bodies. The evaluated nitrogen source was the ammonium sulphate applied superficially as a fertilizer in a latossolo vermelho amarelo soil, under different soil tillage systems, without vegetal covering and under different intensities of simulated rain. The results allowed to identified that the argillaceous fraction of the eroded sediments carried in the runoff suspension was the main way of the nitrogen transport/transference derived from the fertilizer. This transference process was more intensely observed in the first rains. It was evidenced too, that the losses values of soil and water did not influence the nitrogen transport capacity between the planted areas and the water bodies. Aditionally, soil tillage influenced in nitrogen concentrations carried by the runoff. The nitrogen concentrations in the sediments were high, in spite of the low volumes and low intensities of the rain.

The main objective of this thesis is to investigate the impact of microbial extracellular polymeric substances (EPS) on sediment stability and the related factors which influence “biogenic stabilisation” as a basis to the prediction of sediment erosion and transport. The ability to make direct and sensitive measurements of the physical properties of the biofilm is a critical demand to further understanding of the overall biostabilisation processes. Therefore, attention has been focused on developing a new technique, Magnetic Particle Induction (MagPI) for measuring the adhesive properties of the biofilm. MagPI determines the relative adhesive properties or “stickiness” of the test surface, whether a biofilm, a sediment or other submerged material. The technique may have future applications in physical, environmental and biomedical research. Newly developed Magnetic Particle Induction(MagPI) and traditional techniques Cohesive Strength Meter (CSM) for the determination of the adhesion/cohesion of the substratum were used to assess the biostabilisation capacity of aquatic microorganisms. Whilst these devices determine slightly different surface properties of the bed, they were found to complement each other, increasing the range of measurements that could be made and presented a strong correlation in the overlapping portion of the data. It is recognized that microorganisms inhabiting natural sediments significantly mediate the erosive response of the bed (“ecosystem engineers”) through the secretion of naturally adhesive organic material (EPS: extracellular polymeric substances). Interactions between main biofilm consortia microalgae, cyanobacteria and bacteria in terms of their individual contribution to the EPS pool and their relative functional contribution to substratum stabilisation were investigated. The overall stabilisation potential of the various assemblages was impressive, as compared to controls. The substratum stabilisation by estuarine microbial assemblages was due to the secreted EPS matrix, and both EPS quality (carbohydrates and proteins) and quantity (concentration) were important in determining stabilisation. Stabilisation was significantly higher for the bacterial assemblages than for axenic microalgal assemblages. The peak of engineering effect was significantly greater in the mixed assemblage as compared to the bacterial and axenic diatom culture. This work confirmed the important role of heterotrophic bacteria in “biostabilisation” and highlighted the interactions between autotrophic and heterotrophic biofilm components of the consortia. An additional approach, to investigate the impact of toxins on biostabilisation capacity of aquatic organism was performed on cultured bacterial and natural freshwater biofilm. The data suggest a different mode of triclosan (TCS) action ranging from suppressing metabolisms to bactericidal effects depending on the TCS concentration. The inhibitory effect of triclosanon bacterial and freshwater biofilms was confirmed. This information contributes to the conceptual understanding of the microbial sediment engineering that represents an important ecosystem function and service in aquatic habitats.

The findings of this report were thought to be a useful contribution to the current knowledge of the quality of Aberdeen Harbours marine environment, and has resulted in a further round of scientific research into the effects of pollution on marine organisms. An integrative approach was used which combined chemical, biological and ecotoxicological indicators to provide evidence of pollution-induced degradation known as Sediment Quality Triad approach . The use of a Sediment Quality Triad approach to develop a single numerical index to describe the condition of the benthic ecosystem is a useful methodology in demonstrating spatial and temporal variability in marine sediment quality. The appropriate graphic representation of the Triad data can be effective in displaying relationships between patterns of toxicity, biology and chemistry. However the selection of the weighting tool for normalisation does effect the components and subsequently its use as a screening tool should be site or region specific, and not generic. There is a further need to be evaluating the use of sub-lethal toxicity tests and responses relative to changes the benthic community structure and sensitivity to contaminants, particularly in relation to interactions between multiple chemicals. These results show the value of using multi-component parameters for evaluating sediment quality. The combination of field and laboratory studies of sediment quality therefore can an important measure of the relationship between sediment and food-web magnification, and are therefore crucial signposts for hazard identification in marine sediments.

This is the first study undertaken in a controlled environment to understand the kinetics of the release of soluble reactive phosphorus and copper from sediments of natural systems with an associated biofilm, and to identify which of the size compartments affected those fluxes most. It was found that of the sediment size fractions in the system, the stones that had a substantial biofilm growth attached had the greatest influence. Differences in the responses were observed between the sediment size fractions and the two sites, where contaminant concentrations varied. The equilibrium phosphate concentration and a phosphorus transfer index were used to establish if there was a net uptake or release of phosphorus by the sediment size at the time of sampling. The sediment having a biofilm and associated particulate material resulted in a greater flux than fine sediment, which does not support a filamentous biomass. The kinetic results imply a different mechanism than diffusion being involved. It was demonstrated that both gravel and stone substrates can have an important control over the release of soluble reactive phosphorus due to their role as firm substrate for a biofilm growth. Changes in the steady-state concentration of dissolved copper suggest that the bed sediment is responding to reduced river water concentration and setting a new steady-state. The kinetics of the reaction of the sediment to copper were of a similar order, and rate constants increased through the season, but were of a similar magnitude for both sites. The differences in the n and rate constant values indicate a difference in the mechanisms (i.e. the order of the kinetics) of uptake of copper through the seasons. The kinetics are described by a rate law which yields a method of estimating the flux to the sediment for recovery time after a pollution incident and how far downstream the copper concentration would remain elevated after a pollution incident or sediment.

A sediment transport model within the Regional Ocean Modeling System (ROMS) was used to examine how repeated cycles of deposition, erosion, and bioturbation influence flood and storm event bed character offshore of a significant fluvial source. Short-lived radioisotopes Beryllium-7 (7Be) and Thorium-234 (234Th) can be used as tracers of deposition and reworking on the continental shelf, and modeled profiles of these radioisotopes, along with simulated profiles of sediment bed grain size distributions, were analyzed for various model runs.The presence of an atmospherically derived radionuclide,7Be, in seafloor sedimentindicates terrestrial (riverine derived) sediment deposition offshore of a fluvial source.In contrast,234Th naturally occurs in seawater through the decay of its generally conservative parent, 238U, and its presence in the seabed indicates the recent suspension of sediment in oceanographic water. Simulated profiles of 7Be and 234Th weredirectly related to the flood and storm sequences used as model input.The model results showedthat the radioisotopic profiles are sensitive to the timing of 7Be input, phasing of wave and current energy, and intensity of bioturbation; complicating the relationship between simulated profiles andmodel input of flood and hydrodynamic forcing. Sediment grain size and geochronological tracers were used as markers of event beds for flood and storm deposition scenarios.

Tidal inlets on sandy shorelines separate barrier islands and serve as a conduit for transport of sand and water between embayments and oceans, seas, or other tidally influenced waterbodies. Tides and waves induce currents along the coastline that transport sediment across-shore and alongshore. Coastal managers must optimize barrier-inlet system stability while conserving limited sediment resources, and often base management decisions and engineering design upon geomorphic and numerical models that predict the morphological behavior of tidal inlets on short-to-medium timescales (years to decades). The overall goal of this study was threefold. First, to provide science-based practical guidance for regional sediment management in the vicinity of tidal inlets. Secondly, to enhance the understanding of the temporal and spatial scales of sediment pathways in these regions through numerical simulation of traced sediment transport. And, third, to combine these lessons learned in both regional sediment management and analysis of morphodynamic and sediment bypassing pathways with application to a common practical management practice of inlet shoal mining and adjacent beach placement. The temporal and spatial scales controlling the morphodynamics of barrier-inlet systems were reviewed within a regional sediment management context. Next, the application of regional sediment management methods to case studies of multiple barrier-inlet systems in West-Central Florida led to the development of a decision-support tool for regional sediment management (RSM) as applied to barrier-inlet systems. Connecting multiple barrier islands and inlets at appropriate spatio-temporal scales is critical in developing an appropriately scoped sediment management plan for a barrier-inlet system. Evaluating sediment bypassing capacity and overall inlet morphodynamics can better inform regional sand sharing along barrier-inlet coastlines; particularly where sediment resources are scarce and a close coupling between inlet dredging and beach placement is vital to long-term sustainable management. Continued sea-level rise and anthropogenic activities may intensify the need for investigating longer-term processes and expanding regional planning at a centennial timescale, and are acknowledged as challenging tasks for RSM studies going forward. A regionally focused, multi-inlet study was necessary to improve the management plans for the case study inlets (from north to south): John’s Pass, Blind Pass, Pass-a-Grille Inlet, and Bunces Pass. Key recommendations based on the case studies include: 1) allow the natural sediment bypassing to be re-established at Blind Pass inlet through reduced ebb-tidal delta mining, 2) reduce the interruption to sediment bypassing at John’s Pass and Pass-a-Grille inlets through an improved design of the dredged mining areas located along sediment bypassing pathways, 3) allow for continued natural sediment bypassing at Bunces Pass, and, 4) incorporate the cyclic sediment bypassing through swash-bar attachment into the management plan at Bunces Pass and adjacent barrier-islands. Similar systems in other regions may benefit from the lessons derived in this case study of an adaptively managed multi-inlet system. A numerical model that computes hydrodynamics, sediment transport, and morphodynamics including bed layering was incorporated in this study to analyze sediment transport pathways between littoral sources from adjacent beaches and the geomorphic features of an idealized tidal inlet designed to imitate the John’s Pass tidal inlet in West-central Florida, USA. This study developed a methodology to numerically trace sediment transport, deposition and erosion. This method was applied to investigate sediment-bypassing pathways under varying temporal and spatial scales. The analyses of the adjacent beach’s contribution to tidal inlet sediment bypassing demonstrated variable temporal scales on sediment transport and exchange. High-energy wave events dominated the temporal scale for sand to be transported from the updrift beach to the ebb-tidal delta, whereas cyclical tidal processes had a significant influence on the spatial pattern of exchange between the shoals and channel features of the tidal inlet. The ability to simulate burial and erosion of tracers allowed identification of offshore sedimentation hotspots such as terminal lobe as well as zones of deposition and active transport in shallow water, such as the updrift channel margin linear bar and the downdrift platform of the ebb-tidal delta. The general sediment-bypassing pathway reflected a tidal-driven redistribution following event-driven pulses of wave-induced sediment mobilization. Sediment was transported along the beach during these energetic wave events. Flood- and ebb-tidal currents transported the sediment mobilized by high waves into the inlet channels. This was followed by subsequent gradual redistribution of the deposited channel sediments over the ebb-tidal delta features during fair-weather conditions. The modeling methods were then applied to investigate the sediment pathways and bypassing processes for three validated numerical models of coastal tidal inlets that span a range of forcing conditions. The processes that influence sediment transport along various pathways between the several morphological features of each inlet and its adjacent beaches were examined. The sediment tracing methodology employed in this study allowed for an evaluation of the sediment transport pathways between the various morphologic features of a tidal inlet, as well as their respective processes that drive the exchange of sediments. Characterizing and correlating the sediment pathways between tidal inlet morphologic features can improve the inlet reservoir model, which is a predictive model of inlet shoal volumes based on empirical formulae. The results of this study illustrate the value of including sediment-tracking techniques in simulating sediment bypassing and the potential of this application to inform coastal engineering and design modifications to sediment reservoirs of tidal inlets. And, finally, the spatial patterns of transport and erosion and deposition of traced, littoral source sediment, were investigated using the same modeling framework to evaluate the design of ebb-tidal delta mining on sediment bypassing dynamics of a tidal inlet system based on an idealized model of John’s Pass, Florida. Seven mining areas were simulated with traced sediment sources from the updrift beach, downdrift beach, and adjacent shoals. The tracers’ migration pattern and mining area infilling were analyzed to depict the sediment bypassing pathways and their contributions to mining area infilling. Mining area recovery rates were highest along the channel margin linear bar, and decrease offshore and downdrift. Updrift sand sources contributed more to mining area infilling than downdrift sand sources. The position of the mining area in relation to the updrift or downdrift morphological features dictates whether it will receive primarily updrift- or downdrift-originating littoral sediment from the beach. The source of sedimentation within the mining areas is a combination of inlet-ward transport of beach sediment and nearby shoal sediment. Proximity to the inlet channel determined the degree to which sedimentation had originated from longshore transported beach sediment. This methodology can improve confidence in management decisions concerned with the sand-sharing capacity of barrier-inlet systems in a local and regional context.

Ever-growing discharges of various emerging chemical contaminants are imposing a great threat of pollution to the coastal environment. Adsorption by sediment plays an essential role in the transport and fate of pollutants in the aquatic system. The sorption of emerging contaminants onto sediment is believed to be largely dependent on the sediment organic matter (SOM). In the present study, laboratory experiments were carried out on the changes of the adsorption behavior of sediment during the sediment aging and diagenesis process. A few EDCs and antibiotics were selected as the model emerging compounds for the adsorption tests. The results demonstrated that both the quantity and the quality of the SOM affected the adsorption of the model pollutants, such as 17α-ethinyl estradiol (EE2) and bisphenol A (BPA), onto the marine sediment collected from Victoria Harbour, Hong Kong. The adsorption isotherms can be well described by the linear partition model. Natural and artificial sediment with a high SOM content was incubated for 4-6 months to simulate the natural diagenesis process. The most rapid degradation of labile SOM occurred in the first 1 month or so and afterward, SOM reduction became slower. Microbial activity played an important role in SOM degradation and transformation. A rapid initial bacterial growth was observed in the sediment, followed by a slow endogenous decay. The dynamics of biomass growth and decay first transformed the labile SOM into biomass and microbial byproducts. After the exhaust of readily biodegradable SOM, the biomass decay produced humic-like substances, resulting in more refractory and condensed SOM residues in the sediment. More importantly, the degradation and transformation of SOM displayed a profound impact on the adsorption behavior of the sediment. For the selected EDCs and antibiotics, including BPA, EE2, nonylphenol (NP), phenanthrene (PHE) and tetracyclines (TCs), the adsorption capacity indicated by the partition coefficient, Kd, decreased at the beginning of SOM diagenesis. The Kd values for different chemicals recovered lately to different extents as the result of the SOM condensation and humification. All of the organic matter normalized partition coefficients, KOM, of the concerned pollutants increased considerably in the late phase of SOM diagenesis. Based on the experimental results, a general conceptual model was established to describe SOM diagenesis and its impact on chemical adsorption by the sediment. According to the model prediction, the SOM profile would become more dominated by the condensed and refractory fractions during sediment diagenesis with an increasing affinity and partition capacity for organic contaminants. Moreover, the release of adsorbed contaminants from marine sediment in the simulated digestive fluids was investigated. In general, the presence of gastric pepsin and bile salts helped the desorption of hydrophobic pollutants from the sediment into the digestive solutions. The influence of the SOM diagenetic status on chemical desorption from the sediment varied between EDCs of different chemical properties. It is apparent that aged sediment could bring more emerging pollutants into the digestive system of receiving organisms, imposing a potential risk to human health through the food chain.
published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy

Sewers have been designed on the concept of self-cleansing where sediments are expected to move continuously without deposition. Due to the intermittent nature of the flow, deposition of solids in sewers could still occur especially at low flows such as during the receding flow or dry weather flow. The study of sediment movement in sewers will therefore need to cover both rigid (no-deposition) and loose (some deposition) boundary conditions. The present study extended the available data in rigid boundary conditions (clean pipes) to include the effects of surface roughness and pipe size. A complimentary study on the effect of sediment deposits (pipes with deposited beds) was also carried out. Extensive experiments on bed load transport of non-cohesive sediments without deposition were carried out in pipe channels of 154mm, 305mm and 450mm dia. covering wide -ranges of flow depths (0.15 < ya/D < 0.80), sediments (0.46 < dso (mm) < 8.3) and three different bed roughness values (0.0 < ko (mm) < 1.34). Supplementary data on transport over loose beds were collected in a 450mm dia. channel with various bed thicknesses up to 23% of pipe diameter. New transport equations based on all variables involved in the process were derived. Extensive uses of data from other relevant studies were made. The combination of the present and other data for both rigid and loose boundary conditions in pipes produced equations which could be applicable over wide range of conditions in sewers. A complimentary study on the rigid bed rectangular channels was also carried out. Using the newly derived equations, appraisals of the traditional concept of constant velocity criterion were made. The results show the inadequacy of the present design practice for diameters, pipe larger than 300mm. The comparisons made between the newly derived equations for rigid and loose boundaries in pipes suggest that sewers can be designed with clean inverts for diameters up to 1.0m while sewers with larger diameters should be designed allowing for an "optimum" depth of sediment deposits. Design charts based on the newly derived equations were devised.

Hypolimnetic oxygen diffusers increase sediment oxygen demand (SOD) and, if not accounted for in design, can further exacerbate anoxic conditions. A study using extracted sediment cores, that included both field and laboratory experiments, was performed to investigate SOD kinetics in Carvinâ s Cove Reservoir, a eutrophic water supply reservoir for Roanoke, Virginia. A bubble-plume diffuser is used in Carvinâ s Cove to replenish oxygen consumed while the reservoir is thermally stratified. The applicability of zero-order, first-order, and Monod kinetics to describe transient and steady state SOD was modeled using analytical and numerical techniques. Field and laboratory experiments suggested that first-order kinetics characterize Carvinâ s Cove SOD. SOD calculated from field experiments reflected diffuser flow changes. Laboratory experiments using mini-diffusers to vary dissolved oxygen concentration and turbulence were conducted at 4°C and 20°C. Similar to field observations, the laboratory results followed changes in mini-diffuser flow. Kinetic-temperature relationships were also observed in the laboratory experiments. A definitive conclusion could not be made on the broad applicability of first-order kinetics to Carvinâ s Cove SOD due to variability within field experiments. However, in situ experiments are underway that should assist in the overall understanding of the reservoirâ s SOD kinetics.
Master of Science

The sediment transport process for non-uniform mixtures involves a complex dynamic interaction between the material transported, the surface texture and the flow regime. However, the respective influence of each of these on the other, and on the transport rate is not well understood. The primary objective of this experimental study, was to consolidate and extend the understanding of these processes by investigating sediment transport, near bed flow structures and surface texture simultaneously, as various sediment mixtures were input upstream at differing feed rates, onto mobile mixed grain sediment beds. Three sets of laboratory experiments were completed. The first set of experiments were not fed with material, and acted as reference for later experiments. The second set, fed on two separate occasions, onto an already mobile gravel bed, two different sized uniform materials. Material was fed at a fixed rate that was similar in both runs. The third set of runs, fed material mixtures (again onto an already mobile gravel bed) at a rate that was fixed during each experiment, periodic measurements were made of bedload transport rates, bedload composition, bed surface texture and the near bed flow regime. Results showed that the stability of mixed grain bed was strongly influenced by the feed rate and composition of the upstream sediment supply. A relationship between the surface texture and the moving grain triggered a grain interaction process, which was thought to be as important as the fluid forces in governing the sediment transport rate. The interaction process either enhanced bed stability or promoted sediment movement. How the system responded was determined by the flow regime, the extent of surface texturing and the grain size distribution of the moving grains.

Lake sediments have been identified as an alternative to contemporary stream monitoring to establish catchment sediment yields and infer erosion rates. This is due primarily to the longer time period over which the former is based, which makes established yields and rates more representative of means or trends in sedimentation. Studies using lake sediments to establish sediment yields have generally assumed that all the sediment contained within a lake is derived from erosion of the catchment under investigation. This study undermines this assumption by constructing a comprehensive lake sediment budget to asses the relative contributions from various sources. Late Holocene (the last 2350 years) rates of sediment yield and erosion are established for 3 small (<1 km²) catchments that straddle timberline (1620 - 1850 m above sea level) in the Coast Mountains of British Columbia. Due to the temporal and spatial variability of sedimentation in lakes, sediment cores for each lake were taken using a multiple-core approach. Chronology was established by the presence of a dated tephra layer. Once the cores were extracted, corrections were made for sediment derived from aquatic productivity (organic matter and biogenic silica), regional aeolian dust input, the erosion of lake banks and for outflow losses. These sources of sediment could account for between 55 and 99% of the sediment contained within the 3 lakes. Lake trap efficiency ranges from low to >70%. Once corrected, estimates of sediment yield range from 4 and 244 kg km⁻²yr⁻¹. The rate of regional aeolian deposition indicates that, in certain areas, these catchments are undergoing net deposition and not net erosion. The implications for lake sediment-based sediment yields and erosion rates are examined. When placed in a regional context sediment yields are more than 1 order of magnitude lower than larger scale basins due to changes in sediment storage. The spatial and temporal representativeness of the data are also evaluated.
Arts, Faculty of
Geography, Department of
Graduate