Sediment control devices (SCDs) are critical to reducing the contamination of waterways from adjacent construction sites. Perimeter sediment controls retard the flow of surface runoff water originating on site and subsequently reduce solid, nutrient, and metal concentrations suspended in the flowing water. Silt fence is a commonly used SCD comprised of geotextile filter fabric, steel or wood support posts, and wire mesh reinforcement. The Georgia Department of Transportation (GDOT) uses an extensive amount of silt fence every year, and because of high degradation of geotextile in the field, the silt fence installations are rarely recycled. This research measures the performance of five SCDs (two types of silt fence, mulch berm, compost sock, and straw bales) at suspended solid, turbidity, nutrient, and metal reduction. A life cycle analysis (LCA) is performed to identify environmental impacts associated with material production, assembly, installation, use on site, and disposal. An impact analysis is performed according to for each SCD. Results of the impact analysis are compared to determine the SCD with lowest overall environmental impact. Results of the SCD performance study show that silt fence installations performed the best at reducing suspended solids and turbidity, mulch was best at reducing nutrients, and compost was the best at reducing metal concentrations. The life cycle impact analysis indicates that a mulch berm is the SCD with the lowest overall environmental impact. The impact analysis included global warming potential, acidification, eutrophication, and aquatic toxicity.

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.

Levels of selected metals and persistent organic pollutants (POPs) were investigated in sediment and fillet tissue of the sharptooth catfish (Clarias gariepinus), from sites along the Orange-Vaal River system, South Africa. A histological assessment was done on the livers, kidneys, and gills of the fish sampled to determine morphological changes. The sediment and fish sampling sites were selected up- and downstream of major pollution sources such as mining, industrial and agriculture. The concentrations of the metals in the fish and sediment was determined with an inductively coupled plasma mass spectrometry and the POPs with a high resolution gas chromatographyhigh resolution mass spectrometer. Indices were calculated to describe the quality of the sediment The enrichment factor (Ef) of individual heavy metals evaluated elevation in levels above natural geology. The geo-accumulation index (Igeo) determined the degree of pollution by the enrichment levels of the individual metals. The pollution effect of the total mixture of the heavy metals was investigated by the metal pollution index (MPI) and pollution load index (PLI). Ecological risk was determined by calculating the sediment quality guideline index (SQG-I) and a sediment quality index (SQI) to determine the quality of the sediment. For the SQG-I and SQI, international sediment quality guidelines were used, since South Africa does not have them. The bio-accumulation factor (BF) was calculated between sediment and fish. A limited human health risk assessment was done for the consumption of Clarias gariepinus. A semi-quantitative histopathological assessment was preformed and alterations found were numerically described with the aid of mean organ indices. The POPs values were very low. The Igeo and Ef of Se, Hg, Ag and Au were the highest at all the sites. Parys had the most metals that were enriched to different degrees, but Rooipoort had the highest MPI and PLI. The SQG-I indicated that the sites had a moderate chance of posing an ecological risk to its biota, except for Rooipoort that had a high toxic probability. The SQI classified Rooipoort as “fair” in terms of sediment quality and the rest of the sites as “good”. The semi-quantitative histology based assessment results showed that the mean organ and fish indices fell within class 1 (normal tissue structure with slight histological alterations) or class 2 (normal tissue structure with moderate histological alterations). The mean gill, -liver and kidney indices for all the sites fell in class 1. The mean fish index for all the sites however, fell in class 2. The human health risk assesment showed high risk for non-carcinogenic effects from Ag, Hg, As and Cr if fish from the sample sites were to be consumed. The results from this study identified that the river system is polluted by anthropogenic activities. Results showed that the pollutants of concern in the system were ultimately Ag, Hg and PFOS. Although the morphology of Clarias gariepinus was not altered, the results indicated that the Orange-Vaal River system is polluted and that these fish is unsafe for human consumption. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013.

Levels of selected metals and persistent organic pollutants (POPs) were investigated in sediment and fillet tissue of the sharptooth catfish (Clarias gariepinus), from sites along the Orange-Vaal River system, South Africa. A histological assessment was done on the livers, kidneys, and gills of the fish sampled to determine morphological changes. The sediment and fish sampling sites were selected up- and downstream of major pollution sources such as mining, industrial and agriculture. The concentrations of the metals in the fish and sediment was determined with an inductively coupled plasma mass spectrometry and the POPs with a high resolution gas chromatographyhigh resolution mass spectrometer. Indices were calculated to describe the quality of the sediment The enrichment factor (Ef) of individual heavy metals evaluated elevation in levels above natural geology. The geo-accumulation index (Igeo) determined the degree of pollution by the enrichment levels of the individual metals. The pollution effect of the total mixture of the heavy metals was investigated by the metal pollution index (MPI) and pollution load index (PLI). Ecological risk was determined by calculating the sediment quality guideline index (SQG-I) and a sediment quality index (SQI) to determine the quality of the sediment. For the SQG-I and SQI, international sediment quality guidelines were used, since South Africa does not have them. The bio-accumulation factor (BF) was calculated between sediment and fish. A limited human health risk assessment was done for the consumption of Clarias gariepinus. A semi-quantitative histopathological assessment was preformed and alterations found were numerically described with the aid of mean organ indices. The POPs values were very low. The Igeo and Ef of Se, Hg, Ag and Au were the highest at all the sites. Parys had the most metals that were enriched to different degrees, but Rooipoort had the highest MPI and PLI. The SQG-I indicated that the sites had a moderate chance of posing an ecological risk to its biota, except for Rooipoort that had a high toxic probability. The SQI classified Rooipoort as “fair” in terms of sediment quality and the rest of the sites as “good”. The semi-quantitative histology based assessment results showed that the mean organ and fish indices fell within class 1 (normal tissue structure with slight histological alterations) or class 2 (normal tissue structure with moderate histological alterations). The mean gill, -liver and kidney indices for all the sites fell in class 1. The mean fish index for all the sites however, fell in class 2. The human health risk assesment showed high risk for non-carcinogenic effects from Ag, Hg, As and Cr if fish from the sample sites were to be consumed. The results from this study identified that the river system is polluted by anthropogenic activities. Results showed that the pollutants of concern in the system were ultimately Ag, Hg and PFOS. Although the morphology of Clarias gariepinus was not altered, the results indicated that the Orange-Vaal River system is polluted and that these fish is unsafe for human consumption. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013.

Hydrophobic organic contaminants (HOCs) often reside in sediments sorbed to particles, most tightly to particles with high content of organic carbon. If persistent, such pollutants can accumulate in the sediment for many years and constitute a contamination risk for sediment-living organisms and organisms at higher trophic levels, including humans. Since traditional remediation techniques are associated with complications (e.g. release of contaminants during dredging operations, disturbance of benthic faunal communities), or constraints (handling of large amounts of contaminated sediment and water, limitations due to depth and size of the area, high costs), there is a need for new alternative methods. In situ remediation through thin-layer capping (a few centimeter cover) with a sorbing material such as activated carbon (AC) has been proposed as an alternative remediation method. Compared to traditional remediation techniques, AC amendment in a thin layer means less material handling and lower costs and is assumed to be less disruptive to benthic communities. The objectives of this thesis were to investigate the ecological effects from thin layer capping as well as the efficiency in contaminant retention. Thin layer capping amended with AC proved to reduce availability of HOCs to the tested organisms, the gastropod Nassarius nitidus (Paper II), the clam Abra nitida (Paper III) and to polychaete worms  (Paper II and III). The remediation technique also decreased the sediment-to-water fluxes of the contaminants (Paper II and III). However, AC amended thin-layer capping was also found to cause negative biological effects. In laboratory studies with only a few species the negative effects were minor, or difficult to discern with the endpoints used (Paper II and III). In a larger multi-species mesocosm (boxcore) study, on the other hand, the negative effects were more prominent (Paper I) and in a large scale field study the benthic community was found to be profoundly disturbed by the AC amendment, with the effects persisting or even worsening ca one year (14 months) post amendment (Paper IV). / <p>At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 3: Manuscript; Paper 4: Manuscript.</p> / Carbocap / Opticap / Thinc

Spatial and temporal information on catchment sediment sources and sinks can provide an improved understanding of catchment response to human-induced disturbances. This is essential for the implementation of well-targeted catchment-management decisions. This thesis investigates the nature and timing of catchment response to human activities by examining changes in sediment sources and sinks in a dry-tropical subcatchment of the Great Barrier Reef (GBR) catchment area, in northeastern Australia. Changes in catchment sediment sources, both in terms of spatial provenance and erosion type, are determined using sediment tracing techniques. Results indicate that changes in sediment source contributions over the last 250 years can be linked directly to changes in catchment land use. Sheetwash and rill erosion from cultivated land (40???60%) and channel erosion from grazed areas (30-80%) currently contribute most sediment to the river system. Channel erosion, on a basin-wide scale, appears to be more important than previously considered in this region of Australia. Optically stimulated luminescence and 137Cs dating are used to determine pre-and post- European settlement (ca. 1850) alluvial sedimentation rates. The limitations of using 137Cs as a floodplain sediment dating tool in a low fallout environment, dominated by sediment derived from channel and cultivation sources, are identified. Low magnitude increases in post-disturbance floodplain sedimentation rates (3 to 4 times) are attributed to the naturally high sediment loads in the dry-tropics. These low increases suggest that previous predictions which reflect order of magnitude increases in post-disturbance sediment yields are likely to be overestimates. In-channel bench deposits, formed since European settlement, are common features that appear to be important stores of recently eroded material. The spatially distributed erosion/sediment yield model SedNet is applied, both with generic input parameters and locally-derived data. Outputs are evaluated against available empirically-derived data. The results suggest that previous model estimates using generic input parameters overestimate post-disturbance and underestimate pre-disturbance sediment yields, exaggerating the impact of European catchment disturbance. This is likely to have important implications for both local-scale and catchment-wide management scenarios in the GBR region. Suggestions for future study and the collection of important empirical data to enable more accurate model performance are made.

L'évolution des caractéristiques des particules en suspension au cours de leur transfert au sein des bassins versants est encore mal connue. Ceci limite actuellement notre aptitude à prédire correctement l'érosion ou les flux de matières en suspension (MES) et rend difficile la proposition de pratiques de gestion adaptées aux réglementations en vigueur. A partir d'expériences en milieu contrôlé, nous avons montré que les particules de sols ont tendance à se désagréger en milieu turbulent. Il semble de plus qu'une augmentation de la concentration en suspension accélère cette désagrégation et conduise à des particules plus fines. Même si l'évolution des particules à l'échelle horaire semble rester de second ordre derrière les caractéristiques des sols sources, il est indispensable de pouvoir vérifier si les particules en suspension se comportent de la même manière en conditions naturelles où des interactions complexes entre processus peuvent avoir lieu. Cependant l'absence de méthode de mesure permettant le suivi des propriétés de transport des sédiments en écoulements très concentrés (de 1 plusieurs centaines de grammes par litre) dans les bassins élémentaires limite notre capacité à hiérarchiser les processus à considérer pour modéliser le transfert sédimentaire ou améliorer la gestion opérationnelle des sédiments. Afin de répondre à ce besoin instrumental, nous avons développé un Système de Caractérisation des Agrégats et des Flocs (SCAF). Cet instrument est conçu pour être incorporé dans les stations de suivi hydro-sédimentaire. La mesure est réalisée immédiatement après prélèvement d'un échantillon de la suspension à caractériser par une série de capteurs optiques qui suivent l'évolution de l'absorbance optique durant la sédimentation de l'échantillon. Nous proposons une méthode de traitement des données optiques donnant accès à la distribution des vitesses de chute de la suspension ainsi qu'à un indice de floculation qui renseigne sur la capacité des MES à floculer durant leur sédimentation. Les distributions de vitesses de chute mesurées sont validées sur une large gamme de matériaux et de régimes de sédimentation, afin de couvrir la variabilité des types de matériaux et des concentrations observées en milieu naturel. Pour des sédiments non cohésifs ou floculant peu durant leur sédimentation les mesures du SCAF s'ajustent sur celles issues des autres méthodes. Pour les suspensions qui floculent durant leur sédimentation, la plupart des méthodes de mesure classiques conduisent à des vitesses de chute non représentatives de la suspension. Nous avons montré que les variations des propriétés optiques des matières en suspension lors de leur floculation impactent nos mesures. La méthode proposée permet cependant de quantifier l'augmentation des vitesses de chute avec la floculation, et d'encadrer l'incertitude des mesures. Pour les mesures à forte concentration (>10 g/l), un front d'entravement peut se former durant la sédimentation, le SCAF mesurant alors précisément les vitesses de chute du front. La mesure des distributions des vitesses de chute et de la cohésion des particules en suspension peut permettre d'identifier différentes populations de particules formant une suspension (grains de sables, flocs, matières fines...). Le suivi de telles informations au sein de bassins versants ouvre de nouvelles perspectives pour aborder la connectivité sédimentaire et s'orienter vers une gestion optimale des flux de MES. / Little is known about the processes that govern the evolution of suspended particle characteristics during their transport through a river basin. This is a main limitation for modelling erosion severity or suspended solids (SS) fluxes. It also leads to difficulties to propose management policies adapted to environmental legislation. Based on experiments in controlled environments, we have shown that soil particles tend to disaggregate in turbulent flows. The increase in SS concentration was associated to an increase of the disaggregation of SS particles, leading to smaller final particle sizes. Laboratory experiments also showed that the variability of the particle sizes due to their evolution over one hour was smaller than the variability due to the soil type from which the particles originated. However it is important to ensure that the suspended particles behave in the same way in natural conditions, where complex interactions between hydraulic, chemical and biological processes can influence their evolution. Up to now no measurement method allows measuring continuously the suspended sediment properties in highly concentrated fluids (from one to hundreds grams per liter), such as those observed in headwater catchments during runoff events. This severely limits the possibility to identify the processes that are important to consider in numerical models. The Aggregate and Floc Characterization System (SCAF) has been developed in order to measure SS properties for a wide range of SS concentrations. It was designed to be easily incorporated into sequential samplers. Immediately after the collection of a sample from the river, the sedimentation of the suspension is recorded by continuous measurements of the absorbance by a series of optical sensors. A method was proposed to processes the raw optical data in order to obtain the settling velocity distribution of the suspension. It also provides a flocculation index representing the tendency of the particles to flocculate during their sedimentation. The calculated settling velocity distributions were validated on a large range of materials and settling regimes in order to cover the natural variability of suspended sediments. For sediments that hardly flocculate during their sedimentation or are non-cohesive, the measurements of the SCAF were similar to those from other methods. In the case of suspensions that strongly flocculate during sedimentation, most of the classical methods give non-representative falling velocities. In this case, the optical property of the particles may vary during settling, affecting the optical measurement. The proposed method allowed quantifying the increase of settling velocity induced by flocculation, and provided confidence intervals for the settling velocities. For high SS concentrations ( > 10 g/l), a settling front can be formed during the sedimentation, which is well characterized by the SCAF. The measurement of the settling velocity distributions and of the flocculation index can be used to identify different particle populations (sand grains, flocs, individual particles) forming a suspension. Monitoring these properties in watersheds offers new insights to explore sediment connectivity within river basins and to optimize water management strategies.

L’érosion hydrique est un processus majeur de dégradation des sols dans le monde avec des conséquences multiples : perte de terres agricoles, envasement des cours d’eau, coulées boueuses. En France, la région Hauts-de-France est la zone la plus touchée par ces pertes en terres qui peuvent dépasser les 10 t ha-1 an-1. Si les processus à l’origine de ces transferts sédimentaires ont été largement étudiés par la communauté scientifique ces dernières années, il reste néanmoins des verrous liés aux variabilités spatio-temporelles. De plus, l’efficacité des politiques récentes de lutte contre l’érosion n’est pas quantifiée. Cette étude propose une analyse de la variabilité spatio-temporelle des transferts sédimentaires selon plusieurs échelles (1-1000 km²), et une première évaluation de l’efficacité des politiques d’aménagement au sein d’un bassin du Nord de la France (la Canche ; 1274 km²). Une station de mesure haute-fréquence, a été implémentée à l’exutoire d’un sous-bassin versant de la Canche (la Pommeroye ; 0,54 km²) pour quantifier les transferts hydro-sédimentaires sur deux années hydrologiques contrastées. Selon nos résultats, les transferts varient de 29,4 à 70 t km-2 an-1. 40% du flux est exporté au cours de 3 épisodes érosifs majeurs (sur 48 enregistrés) et les paramètres forçants sont liés à la durée d’un épisode pluvieux et la quantité de précipitations. Sur ce même bassin, la prédiction spatiale à l’échelle centimétrique des transferts hydro-sédimentaires a pu être effectuée via le nouveau modèle d’érosion des sols WATERSED (BRGM) et l’efficacité d’un plan d’aménagement de lutte contre l’érosion a été quantifiée. Nos résultats permettent de valider l’opérabilité du modèle sur ce territoire. Les transferts sédimentaires à l’échelle du parcellaire agricole peuvent atteindre les 76 t km-2 pour un évènement donné et sont influencés par l’état de surface du parcellaire agricole. Une réduction significative (jusqu’à 84%) des transferts par les aménagements d’hydraulique douce est également observée. A l’échelle du bassin de la Canche, l’utilisation de traceurs chimiques et spectrocolorimétriques dans un modèle de mélange (Sed_Sat ; USGS) a permis d’évaluer d’une part les contributions des affluents de la Canche et d’autre part les contributions des sols et des berges (respectivement 30-70%). Des variations spatio-temporelles significatives ont pu être observées et les résultats tendent à montrer un potentiel impact positif des politiques récentes d’aménagement du territoire. Cette étude montre également que de nouveaux traceurs liés à la signature spécifique des particules magnétiques sont particulièrement prometteurs dans ce contexte pour tracer un signal d’érosion des sols. A terme, ces données pourraient être incluses dans des approches sediment fingerprinting. L’analyse selon plusieurs modalités spatio-temporelles et le couplage expérimentation/modélisation améliore donc notre compréhension de la dynamique des transferts sédimentaires sur le bassin versant de la Canche. Cela fournit des résultats essentiels pour orienter les futures politiques de lutte contre l’érosion des sols. / Water erosion is a serious concern in global land degradation leading to multiple consequences: loss of arable lands, siltation of streams, mudflows. In France, the Hauts-de-France region is the most affected area, and soil loss can exceed 10 t ha-1 yr-1. Although hydro-sedimentary processes have been widely studied by the scientific community, there is still a lack of knowledge in the understanding of the spatio-temporal variabilities. Additionally, the effectiveness of recent erosion control policies so far cannot be quantified. This study proposes an analysis of the spatio-temporal variability of sedimentary transfer at different scaling (1-1000 km²), and an initial assessment of the effectiveness of management policies within a northern France catchment (the Canche river, 1274 km²). A high-frequency monitoring station was implemented at the outlet of a Canche sub-catchment (the Pommeroye, 0.54 km²) to quantify the hydro-sedimentary transfer over two contrasted hydrologic years. According to our results, sediment yield varies from 29.4 to 70 t km-2 yr-1. 40% of the flux is exported during 3 major erosive events (out of 48 recorded) and the forcing parameters are related to the duration and the amount of rainfall. In this sub-catchment, the centimeter-scale spatial prediction of the hydro-sedimentary transfer was carried out using the new soil erosion model WATERSED (BRGM) and the effectiveness of an anti-erosion management plan was quantified. Our results validate the operability of the model in this context. For a given event, sediment transfer can reach 76 t km-2 yr-1 in agricultural plots and are strongly depending on the soil surface state. A significant reduction (up to 84%) of sedimentary transfer by the anti-erosion plan was also observed. At the scale of the Canche catchment, the use of chemical and spectrocolorimetric tracers in a mixing model (Sed_Sat tool; USGS) evaluated the contributions of the Canche tributaries and sediment sources contributions (i.e. channel banks and soils; 30-70% respectively). Significant spatio-temporal variations have been observed and the results show a potential positive impact of the recent management policies. This study also shows that new tracers related to the specific signature of magnetic particles are promising in the context to trace soil erosion. For further analyses, this data could be included in sediment fingerprinting approaches. Thus, this study based on several spatio-temporal modalities and the coupling of experimentation and modelling improves our understanding of the Canche hydro-sedimentary dynamics. It provides essential results to guide the future erosion control policies.

The tidal stream industry has seen large growth in recent years, and the number of pre-commercial scale devices currently being tested reflects this development. However, commercialising this technology whilst showing that their environmental impacts is minimal remains a challenge. The impact on benthic communities is not considered to be a key strategic consenting issue, yet it is anticipated that the benthic habitat will change as a result of the presence of tidal turbines. To date, only single tidal turbine devices have been installed to demonstrate the application of tidal stream technology but despite successful tests there are still uncertainties surrounding the quantitative impacts these turbines have on local benthic communities. Unlike the wind industry, where physical effects of wind turbines have been catalogued through deployment of thousands of turbines, the tidal stream industry lacks these array scale quantitative data. Local impacts are known, but understanding the scale of the impacts and their relative significance of large arrays remains unknown. Tidal turbines (both single and arrays) interact with the hydrodynamics by decreasing the near field current flow directly in its wake through energy extraction and the drag caused by the physical structure. However, turbines may also affect the far field hydrodynamics, altering bed characteristics, sediment transport regimes and suspended sediment concentrations. As benthic habitats are closely linked to the physical seabed composition and the hydrodynamic conditions, the benthic environment is affected by to changes in the current flow. This thesis presents a series of studies investigating the interaction between tidal turbines and the benthic environment. Based on the hydrodynamic modelling software, TELEMAC2D, a numerical model has been developed to investigate the hydrodynamic impact of a single tidal array at Ramsey Sound, Pembrokeshire as well as the cumulative impact of multiple tidal developments in the Irish Sea. Based on the results of the models, the hydrodynamic outputs were used as inputs to drive a species distribution model, based on the software MaxEnt, to investigate how the distribution of benthic species altered in the presence of a 10MW tidal array at Ramsey Sound. Results of the study showed the development would have a minimal negative impact on the benthic environment.

Este trabalho teve como objetivo principal a utilização de duas variantes da técnica analítica de fluorescência de raios X, dispersiva em energia - EDXRF e reflexão total TXRF, na determinação de Pb em amostras de águas superficiais e subterrâneas, e em sedimentos em suspensão e de fundo. Cinco amostras de cada matriz foram coletadas em uma área contaminada, nas proximidades da desativada fábrica de baterias Indústria Acumuladores Ajax Ltda., localizada no km 229 da rodovia Jaú-Ipaussu, em Bauru, SP. As variantes EDXRF com pré-concentração com APDC e medida direta por TXRF mostraram resultados satisfatórios na determinação de Pb em soluções-padrão e amostra certificada de água natural SRM1640, produzida pelo NIST, obtendo-se concentrações compatíveis com os valores esperados. A primeira técnica resultou em limite de detecção da ordem de 0,70 mg L-1, com tempo de análise de 300 s, melhor que a segunda técnica (4,46 mg L-1), em 200 s. Estas duas variantes também foram utilizadas para outros elementos químicos, como o Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn e Br, onde a EDXRF mostrou também melhores limites de detecção para todos os elementos. Para Ni, Cu e Zn, importantes na indústria de baterias, foram encontrados os limites de 0,34 - 0,27 e 0,24 mg L-1, respectivamente, enquanto que por TXRF foram encontrados os valores ao redor de 1 mg L-1. Na validação destas duas metodologias para análise de água, a EDXRF mostrou resultados mais próximos aos valores esperados, enquanto que por TXRF foram superestimados na maioria das vezes, com exceção para As, Se e Pb. Este erro foi devido a uma interferência espectral ocasionada provavelmente pela presença dos elementos Ti ao Zn nos componentes metálicos do arranjo experimental, ausentes no suporte refletor de quartzo, colimador do detector ou solução do padrão interno. Sem a eliminação dessa interferência, os resultados obtidos por TXRF para estes elementos, com exceção para As, Se e Pb, só podem ser utilizados como qualitativos. Para análise de sedimentos em suspensão foi utilizada a técnica de EDXRF, assumindo a amostra como filme fino, atingindo limite de detecção da ordem de 2 mg g-1 para Pb, enquanto que para o Cu e Zn o limite de detecção foi da ordem de 5 mg g-1, em 300 s. Para sedimento de fundo foi utilizada a mesma técnica, mas admitindo a amostra como espessa, corrigindo-se o efeito matriz através do fator de absorção, validando-a pela análise de amostras certificadas de sedimento (SRM1646a/NIST) e solo (SRM2711/NIST). O limite de detecção para Pb ficou em torno de 2 mg g-1, e para outros elementos os limites foram de 3,07 mg g-1 para Ni, 2,12 mg g-1 para Cu e 1,50 mg g-1 para Zn, em 500 s. Com base nos valores máximos permitidos para Pb, estabelecidos pela Portaria 1469/00 e Resolução 20/1986 CONAMA, duas amostras de água mostraram-se contaminadas pelos resultados obtidos pela variante EDXRF, e quatro pelos resultados da TXRF. Para os outros elementos, apesar da interferência na TXRF, por esta técnica uma amostra de água ultrapassou o limite permissível para Cu e todas as cinco para Zn, e pela EDXRF uma amostra para Ni e Cu em água, e três para Zn. Na legislação brasileira não há limite máximo permitido para Pb e outros elementos em solos e sedimentos, e portanto foram adotados os limites TEL (Threshold Effect Level, nível limiar do efeito) e PEL (Probable Effect Level, nível provável do efeito), utilizados pela Agência Ambiental Canadense. As amostras de sedimento em suspensão mostraram concentrações de Pb menores que o limite de detecção, e das cinco amostras de sedimento de fundo, uma amostra apresentou valor acima do limite TEL, e outra, coletada num ponto bem ao lado da fábrica, acima do limite PEL. Para os outros elementos Ni, Cu e Zn, nenhuma das amostras de sedimento em suspensão ou de fundo não ultrapassaram os limites TEL. / This study had as main objective the use of two variants of the analytical technique of X-ray fluorescence, energy dispersive - EDXRF and total reflection - TXRF, for the determination of Pb in superficial and underground water and in suspended and bottom sediment samples. Five samples of each matrix were collected in a contaminated area near the closed battery plant, Indústria de Acumuladores Ajax Ltd., located on km 229 of the Jaú-Ipaussu highway, near the city of Bauru in São Paulo State, Brazil. The two variants – EDXRF with preconcentration with APDC and TXRF direct measurement – had shown satisfactory results in the determination of Pb in standard solutions and certified natural water sample SRM1640/NIST, obtaining compatible concentrations with the expected values. The first technique resulted in a 0.70 mg L-1 limit of detention, with 300 s analysis time, and the second one 4.46 mg L-1 in 200 s. These two variants were also used for other chemical elements, such as Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn and Br. EDXRF also showed better limits of detection for all the elements. For Ni, Cu and Zn, important in the industry of batteries, the limits of 0.34, 0.27 and 0.24 mg L-1, respectively, were found, while with TXRF the values of around 1 mg L-1 were achieved. In the validation of these two methodologies for water analysis, the EDXRF showed results nearer to the expected values, while with TXRF the results were overestimated most of the times, with the exceptions of As, Se and Pb. This error was due to a spectral interference caused probably by the presence of the elements Ti to Zn in the metallic parts of the experimental arrangement, absent in the quartz reflecting support, detector collimator or internal standard solution. Without the elimination of this interference, the results for TXRF for these elements, with the exceptions of As, Se and Pb, can only be used as qualitative results. For analysis of suspended sediments, the EDXRF technique was used, assuming the sample as thin film, the limit of detection of around 2 mg g-1 for Pb was reached, while that for Cu and Zn was around 5 mg g-1, in 300 s. For bottom sediments the same technique was used, but admitting the sample as thick, the matrix effect through the absorption factor was corrected, validating it for the analysis of certified samples of sediment (SRM1646a/NIST) and soil (SRM2711/NIST). The limit of detention for Pb was around 2 mg g-1 and for other elements the limits were 3.07, 2.12 and 1.50 mg g-1 for Ni, Cu and Zn, respectively, in 500 s. On the basis of the Brazilian allowed maximum values for Pb, established by Decree 1469/00 and Resolution 20/1986 CONAMA, two water samples were shown to be contaminated by the results gotten with variant EDXRF, and four by the results of TXRF. For the other elements from the TXRF results (despite the interference) one water sample exceeded the permissible limit for Cu and all the five for Zn, and for the EDXRF results one sample for Ni and Cu and three for Zn. In the Brazilian legislation there is no maximum limit allowed for Pb and other elements in soils and sediments; therefore, TEL (Threshold Effect Level) and PEL (Probable Effect Level) limits from the Canadian Environment Agency were adopted. The suspended sediment samples showed Pb concentrations lesser than the limit of detection. From the five bottom sediment samples, one sample presented a value above the TEL limit, and another one, collected in a point very close to the plant, above the PEL limit. For the other elements, Ni, Cu and Zn, none of the suspended or bottom sediment samples exceeded the TEL limits.