Dissertations / Theses on the topic 'Sediments'

The study examines sediments of the Productive Series from the western South Caspian Basin. The main goal of this work is to reconstract provenance of the sediments and its relation to the climatic variability during the deposition of the Productive Series. The Productive Series is divided into a lower and upper division. The Russian Platform was the main sediment source area for the Lower Division. Three different sediment source areas were determined for the Upper Division: the Russian Platform was sediment source area for the Absheron Peninsula; the Greater Caucasus was the main sediment source area for the South Absheron Offshore Zone and the Lesser Caucasus was the main sediment source area for the Baku Archipelago. The sediments of the Lower Division have variable smectite and illite concentrations which indicate climate change between humid and arid conditions in the Russian Platform. The Upper Division of the Productive Series from the Absheron Peninsula is characterised by high amounts of illite. It suggests physical weathering under arid climatic condition on the Russian Platform at the time of deposition. Variation of the smectite and illite assemblages of the Upper Division from the South Absheron Offshore Zone probably indicate that the climate alternated between humid and arid conditions in the Greater Caucasus. The low amount of the TOC ratios in the Productive Series are associated with arid climatic condition in the Russian Platform and the Greater Caucasus. The much higher TOC/TN ratios (>35) indicate that sediments of the Productive Series were impacted by oil. However the low TOC/TN ratios (<12) in some intervals of the Productive Series suggest an aquatic source for an organic matter.

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

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.

Experimentos em mesocosmos, por se tratarem de estudos in-situ, possibilitam extrapolar para o campo, investigações realizadas em menor escala, com maior seguridade. Em fevereiro de 2002, foram instalados às margens da represa do Lobo (22º15\'S e 47º49\'W) nove mesocosmos, construídos com plástico (PVC) em forma de hexágono com 2 metros de altura, com fundo aberto em contato com o sedimento e volume variando entre 4,5 e 5,1 m3, em função da declividade do terreno. De acordo com a resolução 20/86 do Conselho Nacional do Meio Ambiente, as concentrações máximas permitidas para os metais cobre (0,02 mg/L) e cromo (0,5 mg/L) em corpos d\'água Classe 2 foram adicionadas aos mesocosmos, originando-se triplicatas, adotando-se outros três mesocosmos como controles. O objetivo principal deste trabalho foi verificar as possíveis alterações no ambiente sedimento, particularmente o enriquecimento e a indução de toxicidade, em função da adição dos metais mencionados. Para tanto, amostras foram coletadas através de dragas e testemunhos nos tempos 0 dia (antes da contaminação), 10 dias, 20 dias e 30 dias após a contaminação (final do experimento). Em seguida, as amostras foram preparadas e submetidas às análises físicas e químicas, caracterização da macrofauna bentônica e diversos ensaios toxicológicos. A partir dos dados gerados, efetuou-se o estudo integrativo da tríade de qualidade de sedimentos. Os resultados obtidos mostraram um discreto aumento na concentração total dos metais cobre e cromo nos sedimentos dos mesocosmos contaminados em comparação aos controles, sendo verificada diminuição na abundância de organismos bentônicos e efeitos tóxicos sobre os organismos-teste submetidos a estes sedimentos. As respostas da tríade foram essenciais para a caracterização da qualidade dos sedimentos dos mesocosmos controle em relação aos dos mesocosmos contaminados.
In-situ mesocosms experiments allow the extrapolation of laboratory data to the field with high reliability. In the present study, nine hexagonal PVC mesocosms with 2 m height and 4.5 to 5.1 m3 volume were installed in contact with the sediment near the Lobo reservoir dam (22º15\'S e 47º49\'W) in february of 2002. In accordance with the National Environmental Council (CONAMA) 20/86 resolution for Class 2 water bodies, the maximum allowed concentrations of copper (0,02 mg/L) and chromium (0,5 mg/L) were added to the mesocosms (triplicate), and three other ones were used as controls. The main purpose of this study was to evaluate the possible changes in the sediment environment, particularly the enrichment and induction of toxicity, by the contamination of these metals. The sediment was sampled by means of Eckman-Birge and core samplers on the 0 (before the contamination), 10th, 20th and 30th days (end of the experiment). Afterwards, physical and chemical analyses, benthic macrofauna characterization and several toxicity assays were conducted with the samples. In order to better evaluate these results, the sediments quality triad was considered. A discrete increase in the total concentration of copper and chromium was observed in the sediments of the contaminated mesocosms when compared to the controls, as well as a reduction in the abundance of benthic organisms and toxic effects over the organisms tested with these sediments. The triad responses were essential for quality characterization of the control mesocosms sediments in comparison with the contaminated ones.

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.

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.

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.

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.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.
Committee Co-Chair: Joseph B. Hughes; Committee Co-Chair: Kurt D. Pennell; Committee Member: Danny D. Reible; Committee Member: Frank E. Loeffler; Committee Member: Jim C. Spain; Committee Member: Martial Taillefert; Committee Member: Terry W. Sturm.

O conhecimento dos processos que envolvem o transporte, deposição e suspensão de sedimentos em rios é de vital importância na conservação, desenvolvimento e utilização dos recursos hídricos e do meio ambiente. Entretanto, no Brasil, que possui como base energética a hidroeletricidade, não se tem dado a devida atenção no que se refere à sedimentação em virtude da dificuldade na aquisição desses dados e custos envolvidos. Sendo assim esta pesquisa teve como objetivo definir as necessidades relativas à precisão, facilidade, custo e freqüência de aquisição dos dados referentes ao aporte de sedimentos em rios, identificando as tecnologias atuais e as tecnologias promissoras que estarão disponíveis em curto prazo para satisfazer essas necessidades.
The knowledge of the processes involving the transport, deposition and suspension of sediment in rivers is of vital importance in the conservation, development and utilization of water resources and the environment. Meanwhile, in Brazil, which has based the hydropower energy, has not given proper consideration with regard to sedimentation due to the difficulty in acquiring such data and costs involved. So this research aimed to define the needs on the accuracy, ease, cost and frequency of data acquisition for the supply of sediment in rivers, identifying current technologies and promising technologies that will be available on short notice to meet those needs.

The profundal sediment of many lakes is contaminated by heavy metals and persistent organic pollutants (POPs) deposited from the atmosphere, yet there has been little assessment of the biological effects of these toxicants. A Tier I sediment ecological risk assessment of profundal lake sediment that covers the range of contamination in the UK and Ireland was completed. Three laboratory sediment bioassays were used, Daphnia magna 7-day survival and reproduction, Gammarus pulex 14-day survival and growth and Chironomus riparius 10-day survival and growth/reproduction, and the concentrations of seven heavy metals and four groups of POPs (polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, organochlorine pesticides and polybrominated diphenyl ethers) were determined.

Mineral dissolution is an inherent chemo-hydro-mechanical coupled diagenetic process in sediments. This ubiquitous geological phenomenon affects all properties in sediments, however, its engineering impact remains largely unknown. This research centers on the effects of mineral dissolution on sediment behavior with emphasis on dissolution modes in nature and their engineering implications. Five different dissolution modes are identified: homogeneous, pressure-dependent, and localized dissolution, and the dissolution of shallow and deep dissolvable inclusions. The consequences of each dissolution mode are investigated through experiments and discrete element methods. While each dissolution mode triggers unique consequences, it is observed that in all cases 1) significant displacement takes places during dissolution, 2) there is a pronounced effect of internal friction and the extent of dissolution on the evolution of the sediment, 3) the sediment has higher compressibility and exhibits a more contractive tendency after dissolution, 4) a porous honeycomb-shaped internal fabric develops accompanied by contact force concentration along dissolved inclusions, and 5) horizontal stress reduction takes place during dissolution and shear localization may develop under zero lateral strain conditions. Mineral dissolution has important engineering implications, from soil characterization to slope stability and shallow foundations. Pre- and post-dissolution CPT studies show that dissolution decreases the tip resistance proportional to the extent of dissolution. Dissolution in sloping ground induces global settlement as the prevailing deformation pattern, and prominent lateral movements near the slope surface; sudden undrained shear failure may take place during otherwise quasi-static dissolution. While footings experience larger settlements during post-dissolution loading, subsequent dissolution beneath a previously loaded footing causes displacements that are greater than the sum of dissolution-induced and load-induced settlements.

Polystyrene latices of particle diameter 0.97 ~, 1.41 ~ and 1.92 ~, at an electrolyte concentration of 0.5 mol dm- 3 sodium chloride, were' sterically stabilised by the adsorption of a monolayer of a monodisperse nonionic surface active agent, C12E6• Optical microscopy showed that the resultant systems were weakly flocculated, with only slight agitation required to destroy the flocs. Calculations showed that the van der Waals attractive potential dominated the highly screened electrostatic repulsive potential; the particles were prevented from coagulating into the primary minimum through the presence of the steric barrier. Potential energy well depths of 7 - 15 kT were obtained. Rapid sedimentation of the systems occurred by consolidation of r..he aggregated structure after an induction period which increased with increasing volume fraction to give a final sediment volume fraction of approximately 0.4 - 0.45. Constant stress viscometry demonstrated that the suspensions were shear thinning with a limiting Newtonian viscosity at low stresses. At high stresses the viscosity was similar to that expected for a dispp.rsion of hard spheres as calculated from Krieger's equation~2 Shear wave propagation experiments were performed to measure the high frequency limit of the shear modulus as a function of volume fraction. The values obtained were compared with a theoretical model due to Zwanzig and Mountain79 and based on a statistical mechanical description of the microstructure combined with the pair interaction potential of the particles. Parameters required for the model were the suspension volume fraction, the Stern potential, the Hamaker constant and the extent of the adsorbed layer, all of which were determined independently of the rheological measurements. Good agreement was obtained between theoretical and experimental data when using a Barker Henderson perturbed hard sphere potential model to calculate the pair distributionfunction. The model thus provided a strong test of the use of liquid state theory for the prediction of the transport properties of colloidal suspensions. Predictions of the zero shear viscosity were made using a similar model.

The leakages of metals from acid sulfate soils and their potential toxicity to benthic invertebrates were studied in the sediment profiles of Lillkvasjön and Lövselefjärden - a lake and an estuary known to be affected by acid sulfate soils - in Västerbotten, northern Sweden. The concentrations of 25 different elements were analyzed throughout both sediment profiles through X-Ray Fluorescence (XRF) Spectrometer analysis. Organic matter was measured through loss-on-ignition (LOI). By performing correlation analysis and normalizations to LOI on all sediment variables, Cu, Fe, Ni, Pb, S and Zn were found to be leached from acid sulfate soils to both sites, while Mg and Mn were related to leakages from acid sulfate soils in Lövselefjärden. The concentrations of Cu (195 mg kg-1), Ni (55 mg kg-1), Pb (90 mg kg-1) and Zn (398 mg kg-1) in the surface sediment of Lövselefjärden were classified as potentially toxic to benthic invertebrates. In Lillkvasjön, Cu (210 mg kg-1) and Ni (87 mg kg-1) were classified to have an increased risk of negative impacts on benthic invertebrates, while the concentrations of Pb (121 mg kg-1) and Zn (329 mg kg-1) were likely to low to have any negative effects. These results strengthen previous finds of impacts from acid sulfate soils in the two catchment areas and elucidate the importance of further studies on the impact of acid sulfate soils on benthic invertebrates.

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.

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

The dissertation deals with clogging of reservoirs and ponds by redundant sediments which penetrate water system by erosion. It describes methods of extracting pond sediments. It contains measurement of dewatering of sediments on hydrocyclone and design of laboratory hydrocyclone and filter unit. In the conclusion there is design of technology of dewatering sediments which were extracted by wet method by drainage excavator. Numerical simulation of flowing in hydrocyclones is simulated in the CFX programme and dewatering technology is simulated in the CHEMCAD programme.

The thermal properties of hydrate bearing sediments remain poorly studied, in part due to measurement difficulties inside the hydrate stability envelope. In particular, there is a dearth of experimental data on hydrate-bearing sediments, and most available measurements and models correspond to bulk gas hydrates. However, hydrates in nature largely occur in porous media, e.g. sand, silt and clay. The purpose of this research is to determine the thermal properties of hydrate-bearing sediments under laboratory conditions, for a wide range of soils from coarse-grained sand to fine-grained silica flour and kaolinite. The thermal conductivity is measured before and after hydrate formation, at effective confining stress in the range from 0.03 MPa to 1 MPa. Results show the complex interplay between soil grain size, effective confinement and the amount of the pore space filled with hydrate on the thermal conductivity of hydrate-bearing sediments.

Reservoirs in areas with a high sediment yield will without mitigation sooner or later be filled up with sediments, reducing the volume available for regulation for electric generation. Flushing of sediments is a management strategy used in many reservoirs in the world, with varying degree of success. The Angostura reservoir is a shallow reservoir located on an inundated river, making it extra vulnerable to sedimentation. It is estimated a yearly inflow of 1.5 million tons of sediment. Other reservoirs are located upstream, and the flushing of these leads to large quantities of sediment inflow in a short period of time. In September every year, the water level in Angostura is partially drawn down to route this sediment through the reservoir. In November, the water level is drawn down completely, and a full sediment flushing is performed. The RESCON model is a spreadsheet program designed to find a technically feasible sediment management strategy that maximizes the economical benefits of the project. Flushing is modeled with a simple algebraic model. SSIIM is a three-dimensional computational fluid dynamics program designed for hydraulic engineering. Sediment erosion, transport and sedimentation can be modeled in a complex reservoir geometry using an adaptive grid with a moveable bed. The main objective of this thesis is to test the performance of the RESCON and SSIIM models. The RESCON model was tested on the November flushing to see if it can reproduce the measured volume of flushed sediments. SSIIM was used for simulation of sediment concentration distribution in the reservoir, and to model the September flushing. The results are compared to measured values. The reservoir geometry is based on bathymetry data from September 2011. Inflow series are from logged values at the hydropower plant. Depth-averaged concentration values are used to present the longitudinal concentration distribution, and Hunter Rouse profiles to present the vertical distribution. Using known reservoir values and the recommended coefficients, the RESCON model was not able to get close to the actual volume of flushed sediments. Although the model has given promising results in other cases, the complex reservoir geometry in Angostura sets heavy restrictions on the flushing processes in the reservoir, which an algebraic model of this type cannot reproduce. The steady state simulation was successful in explaining previously unexplained variations in the concentration in the lateral and longitudinal direction of the reservoir. The simulation reproduces the longitudinal and vertical concentration distribution well. A bug in the implementation of the second-order scheme in SSIIM was discovered, which has later been fixed, giving more similar results for the first-order and second-order schemes. The time allocated for the flushing simulation was not enough to get satisfactory results. The erosion in the upstream end is modelled well, but the measured sedimentation in the downstream area is much larger than in the simulations. With more time for this simulation, it would have been possible to increase the quality of the results.

Differential compaction within alluvial sediments results from the inherent juxtaposition of sand, si It, clay and peat on the floodplain. Differential compaction is primarily dependent on (a) the nature of overbank mudstone compaction, and (b) the relative timing of channel and adjacent overbank sediment deposition. Results from the analysis of modern overbank sediments indicate that the near-surface porosity of alluvial overbank sediment Is controlled by the complex interaction of grain shape, grain size, clay content, groundwater fluctuations, evaporation and transpiration, suggesting that the subsequent compaction of these sediments would be an extremely heterogeneous process, with n'o single controlling parameter. Porosity-depth curves derived from modern sediment analysis indicate that a significant amount of compaction occurs during the first few metres of burial. Examination of samples suggest that ·porosity loss may be due to the expulsion of water from the sediment pores, and the rearrangement of grains from an unstable packing arrangement to a more stable one. Early differential compaction will affect floodplain topography, and therefore directly influence the subsequent pattern of facies distribution. However, as significant amounts of compaction have occurred during very early burial, later stages of compaction will have a less marked effect on alluvial stratigraphy than has been previously suggested. In particular, simulation models such as Bridge & Leeder (1979) which suggest that channel "packing" increases with depth may not be entirely correct. If, within an alluvial sequence, there is no compactional deformation of features such as alluvial channel wings, it is unlikely that channel packing will have increased with depth. Studies of the Middle Jurassic alluvial sediments of North Yorkshire and the Cretaceous of the Isle of Wight, illustrate that the effects of differential compaction can be observed on several scale~: (a) channel belt, (b) individual channel or bedform, and (c) microscopic

Salt-marsh sediments can provide important achives of past sea levels if they can be securely dated. This thesis investigates eight methods for dating salt-marsh sediments. These include traditional and established dating methods (¹⁴C dating and the radionuclides ¹³⁷Cs and ²¹ºPb) and more novel approaches to dating the deposition of salt-marsh sediments (palaeomagnetic dating, the use of' atmospheric stable lead deposition, tephra chronologies, pollen markers, SCP analysis and the use of atmospheric ¹⁴C 'bomb spike' and high-precision AMS ¹⁴C measurements). Sites were selected to provide contrasting sediment sequences that differed both in lithology and accumulation rates and included salt marshes from the Taf estuary (southwest Wales), the Arne Peninsula (southern England) and Vioarholmi (western Iceland). The investigations in the Taf estuary produced the first palaeomagnetic chronology from a salt marsh. From the Arne Peninsula this thesis reports the first successful use of bomb-spike calibrated ¹⁴C analyses in a salt marsh as well as high-precision AMS ¹⁴C ages for the 'problem' period AD 1700-1950. Stable Pb analysis at all three sites produced a number of chronological markers that signalled the timing of increases in industrial Pb emissions, and the later use of Pb petrol additives during the 20th century. In addition, a unique isotopic signal, attributed to the working of Pb metal during the height of the Roman Empire in Europe, was found in the Icelandic sediments. The radionuclides ²¹ºPb and ¹³⁷Cs produced precise chronologies for the last 100 yr in the Taf estuary. However, post-depositional mobility of ¹³⁷Cs on the Arne Peninsula and low ²¹ºPb concentrations at Vioarholmi prevents the construction of reliable ²¹ºPb and ¹³⁷Cs chronologies. In contrast, the use of tephra at Vioarholmi, and pollen and spheroidal carbonaceous particle markers on the Arne Peninsula, showed great potential as independent unique-event dating tools that could be used to constrain conventional ¹⁴C calibrations. Finally, the chronological information produced by all the individual methods was combined to construct an integrated chronology for each site. This approach significantly reduced age uncertainties and produced higher resolution, and more robust, salt-marsh sedimentation histories

Sunlight in the ocean water is important for primary productivity, however, in coastal seas, suspended sediments (SPM) limit the availability of sunlight. The suspended sediments scatter and absorb light. Some of the scattered light travel back (backscattered light) to space and can be used in remote sensing of suspended sediments. The absorption of light by suspended particles gives coastal seas their characteristic green colour (suspended sediments in coastal water absorb blue light and only green light of the visible spectrum left in the water column). In this thesis, we evaluate two very different optical methods for measuring the suspended sediment concentration: (i) a standard remote sensing algorithm that relies on backscattering light, and (ii) a colour scale in which perceived colour of the sea is given a number (the Forel-Ule index). Satellite measurements of the mineral component of suspended solid (MSS) have been compared to measurements at a mooring in Liverpool Bay over the period 2003-2010. The mooring is equipped with an optical backscatter sensor (OBS), which has been calibrated against filtered samples to provide estimates of SPM at 10-minute intervals. There are generally good agreement between MSS from the satellite and SPM from the mooring, however, there is a clear seasonal variation in the ratio of MSS/SPM, from about 1.5 in January to 0.5 in June. Part of this variation can bee explained by the sediment being more organic in summer but effect is unlikely to explain the change by a factor of 3 in the ratio of satellite to insitu suspended materials. We interpret most of the observed variation as being due to seasonal changes in the backscattering to total scattering ratio. This ratio is high in winter when the particles are mostly mineral. The satellite, being most sensitive to backscattered light, over-estimates SPM in winter and the reverse is true in summer. Allowing for seasonal changes in mass-specific backscattering coefficient (bb*) which found in this study (higher in winter with 0.0074 m2 g-1 and lower during summer with 0.0031 m2 g-1 will lead to improvements in remote sensing of SPM (satellite SPM algorithm), which assuming a constant bb* value (0.0058 m2 g-1) by Gohin et al ., 2005 over a year. The colour of the sea expressed by the Forel-Ule index (FUI) has been calculated from MODIS satellite imagery of northwest Europe over the period 2003 to 2014. The calculations have been successfully tested against a small observational data set. The measurements of FUI and associated water properties have been made at a coastal location (the Menai Strait), for a period of one year. There is a consistent relationship in these data sets between the FUI and the concentration of SPM, which can best be represented by (for example in the Irish Sea) FUI =6.025log (SPM)+1.99. The colour of the sea, observed from space undergoes seasonal changes consistent with the known variation of SPM in these waters. The sea is greenest in winter when storms increase the SPM concentration. Spatial variation in FUI largely follows water depth. A quantitative comparison between SPM from the satellite (based on backscattering) and that based on the FUI (based on water colour) in Liverpool Bay is in a good agreement in a low concentration but not in higher concentration (more than 15 mg l-1) with the RMS is 3.69.

In dieser Dissertation wurden das Auftreten und die ökologische Bedeutung Vivianits in Süßwassersedimenten erforscht. Vivianit ist das am weitensten verbreitete reduzierte Eisenphosphatmineral, das sich in Gewässersedimenten bildet. Über die Mechanismen der Vivianitbildung in Sedimenten und die quantitative Rolle des Minerals für die Speicherung von Phosphor ist bisher wenig bekannt. Die neuen Erkenntnisse dieser Arbeit basieren auf der Entwicklung einer neuartigen Methode, die eine direkte Identifikation Vivianits mittels Röntgendiffraktometrie in Sedimenten erlaubte. Es gelang erstmalig, Vivianit in Oberflächensedimenten zu quantifizieren. Die vorliegende Arbeit zeigt, dass Vivianit signifikant, mit 10-40 %, zur Phosphorretention in Süßwassersedimenten beitragen kann. Die Untersuchung der Bildungsbedingungen Vivianits in unterschiedlichen Gewässersedimenten Norddeutschlands zeigte, dass das molare Schwefel zu Eisen Verhältnis des Sediments als ein wichtiger Indikator für die Bedingungen identifiziert, welche die Triebkräfte für die An- und Abwesenheit Vivianits darstellen. Eine Eutrophierung von Gewässern und der damit verbundene Anstieg der Sulfidproduktion kann dabei die Bildung Vivianits beeinträchtigen, und eine Abnahme des Phosphorbindungsvermögens des Sediments zur Folge haben. Die vorliegende Arbeit macht deutlich, dass eine artifizielle Erhöhung des Eisengehaltes des Sediments im Rahmen einer Seenrestaurierung eine Vivianitbildung induzieren kann und so langfristig zu einem erhöhten Phosphorrückhalt führt. Sättigungsberechnungen ergaben, dass ein hinsichtlich Vivianits übersättigtes Porenwasser kein sicheres Indiz für die Anwesenheit des Minerals ist. Die Berechnungen sind nicht in der Lage die kleinskaligen chemischen Bedingungen im Porenraum des Sediments abzubilden. Die Untersuchungen zeigen, dass die Bildung von Vivianit einen wichtigen Prozess der Phosphorbindung in Gewässersedimenten darstellt, der bislang jedoch weitestgehend vernachlässigt wurde.
In this thesis, the occurrence and environmental relevance of vivianite in freshwater sediments were explored. Vivianite is the most common reduced iron phosphate mineral which forms in sedimentary environments. Not much is known about the mechanisms which lead to vivianite formation in surface sediments, and about the quantitative role of vivianite in phosphorus sequestration. The development of a novel sediment preparation technique allowed the direct identification of vivianite by powder X-ray diffraction. Notably, for the first time, vivianite was quantified in surface freshwater sediments. The study examplifies that vivianite can significantly contribute to the phosphorus retention in surface freshwater sediments, accounting for 10-40 % of total sedimentary phosphorus. The exploration of vivianite in different surface freshwater sediments located in northern Germany revealed that the sedimentary sulphur to iron ratio is a valuable indicator for the conditions that are important drivers behind the formation or absence of vivianite. It has been demonstrated that eutrophication and the accompanied increase in sulphide production hampers vivianite formation, leading to a decreased phosphorus binding capacity of sediments through increased sediment sulphidization. The present study also revealed, that an iron addition as a measure of lake restoration can trigger vivianite formation, and significantly increases the long-term phosphorus retention of sediments. Pore water equilibrium calculations demonstrated that supersaturated pore water is not sufficient to predict the occurrence of the mineral in situ. Those calculations often fail to predict the occurrence of vivianite because they do not adequately represent chemical conditions within sediment microenvironments. In summary, the formation of vivianite in aquatic sediments constitutes an important process in phosphorus sequestration which has so far largely been ignored.

Le normative sull'ambiente in vigore in una Nazione vengono costantemente aggiornate, sia per l'arrivo sul mercato di nuovi composti (la cui tossicità deve essere prontamente testata) sia per le nuove conoscenze che si acquisiscono quotidianamente nel campo della salute. In Italia, un importante traguardo nella gestione ambientale è stato rappresentato dal Decreto Ministeriale n. 173/2016, che ha finalmente riconosciuto l'importanza dei test Ecotossicologici. Questi sono indispensabili e devono essere integrati con le analisi chimiche, al fine di definire la qualità dei sedimenti marini dragati. Questo studio mirava a sviluppare un nuovo approccio per classificare i sedimenti qualora vi fosse stata, in un sedimento, una "non-corrispondenza" tra il rischio chimico e il rischio ecotossicologico. Spiegare questo disallineamento potrebbe trovare terreno fertile nell'evidenza che alcune molecole inquinanti non sono state prese in considerazione dal D.M. 173, come ad esempio gli ftalati. Dal punto di vista ecotossicologico, invece si deve ricordare che l'uso di test biologici era inizialmente finalizzato alla definizione di una perturbazione che si era già verificata nell'ambiente; invece oggi i test ecotossicologici vengono utilizzati insieme ai parametri chimici per avere un approccio predittivo: ovvero utilizzando le analisi come strumento di previsione per la valutazione del rischio ambientale e la classificazione delle diverse matrici. Sebbene l'uso di organismi viventi nei test di tossicità sia ben riconosciuto e ampiamente considerato da metodologie e protocolli sviluppati da numerose organizzazioni internazionali nel campo ambientale (es. EPA, ISO, ...), dovrebbe essere presa in considerazione la presenza di alcuni limiti di una certa rilevanza. La valutazione della tossicità è uno degli argomenti di discussione più attuali non solo nel mondo della ricerca, ma anche in quello politico-amministrativo: infatti, il problema di definire la tossicità di un campione è cruciale per stabilire criteri qualitativi e applicare programmi di risanamento e sanzioni amministrative. Per tutti questi motivi, i dati chimici ed ecotossicologici dovrebbero essere supportati da dati molecolari. In questo studio, i risultati ottenuti hanno chiaramente dimostrato l'idoneità dell'embrione di Crassostrea gigas quale eccellente modello sperimentale per ottenere prove chiare sulla tossicità degli elutriati di sedimento marino. Infatti, nonostante la mancanza di corrispondenza tra i dati chimici ed ecotossicologici per i tre sedimenti selezionati, che consentono di ipotizzare una differente tossicità, i risultati molecolari ottenuti suggeriscono fortemente la capacità di tutti i sedimenti di causare stress ossidativo nello sviluppo embrionale dell'ostrica. L'identificazione di biomarcatori molecolari nelle larve di C. gigas esposte a elutriati di sedimenti, potrebbe aiutare nella classificazione della qualità dei sedimenti e i risultati potrebbero essere l'integrazione con il comune approccio chimico ed ecotossicologico, migliorando significativamente il sistema di valutazione di qualità dei sedimenti. Inoltre, nonostante non richiesto dal decreto, è stata posta un'attenzione particolare alla rilevazione degli ftalati, esplorandone gli effetti - dovuti alla loro presenza ambientale - nell'orata, analizzando in modo particolare cosa causano sul metabolismo dei pesci: maschi adulti di Sparus aurata sono stati esposti, attraverso la dieta, a due dosi di DiNP, mostrando la capacità di questo composto di influenzare sia il metabolismo dei pesci che il sistema antiossidante. Le prove ottenute in questo studio suggeriscono fortemente alle agenzie ambientali che dovrebbe essere implementato l'elenco dei composti da monitorare e considerare, al fine di avere una migliore gestione ambientale. Infine, i risultati ottenuti in questo studio usando un approccio integrativo hanno permesso di acquisire una conoscenza più approfondita della tossicità dei sedimenti, sia dal punto di vista chimico che biologico.
Environmental laws in force in a country, constantly updated, both for the new materials presented in the market - of which non-toxicity must be proved - and for the new knowledge acquired in the field of health. In Italy, an important milestone in environmental management has been represented by the Ministerial Decree n. 173/2016, which finally recognized the importance of ecotoxicology in addition to chemical analysis. The necessity of integrating ecotoxicological data with chemical ones, in order to define the quality of marine dredged sediments deeply emerged. In fact, this study aimed at developing a novel approach to classify sediments when non correspondence between the chemical and ecotoxicological risk, identified by Decree n. 173, was found. From the chemical point of view, it could be done the fact that some polluting molecules have not been taken into consideration by D.M. 173, such as phthalates. On the ecotoxicological side, it must be remembered that the use of biological assay was initially aimed at defining a perturbation that had already occurred; instead today, in the D.M. 173, they are used together with the chemical parameters to have a predictive approach, using the analyses as a forecasting tool for the evaluation of the environmental risk and the classification of the different matrices. Although the use of living organisms in toxicity tests is well recognized and widely considered by methodologies and protocols developed by international environmental organization (ex. EPA, ISO, …), the occurrence of some limitation, also of ecological relevance, should be considered. The evaluation of toxicity is one of the most current topics of discussion not only in the world of research, but also in the political-administrative one: in fact, the problem of defining the toxicity of a sample is crucial to establish qualitative criteria and apply remediation programs and administrative sanctions. For all these reasons, chemical and ecotoxicological data should be supported by molecular data. In this study, the results obtained clearly demonstrated the suitability of C. gigas embryo as an excellent experimental model to obtain clear evidence about elutriated toxicity. In fact, despite the lack of correspondence between chemical and ecotoxicological data for the three selected sediment, which let hypothesize their different toxicity level, the molecular results obtained strongly suggest the ability of all sediments to cause oxidative stress in developing oyster. The identification of molecular biomarkers in oyster larvae exposed to sediment elutriates, could help in the classification of sediment quality and the results could be to integrate with the common chemical and ecotoxicological approach, significantly improving the evaluation system. In addition, despite not requested by the decree, an additional focus on phthalate detection was laid, and the effects of their environmental presence was explored in seabream analysing the effects of their dietary administration on the fish metabolism: adult males of S. aurata were exposed, through the diet, to two doses of DiNP, showing the ability of this compound to affect both the fish metabolism and antioxidant system. The evidence obtained in this study, strongly suggest to environmental agencies that the list of compounds to be monitored and considered for a better environmental management should be implemented. At the end, the results obtained in this study using an integrative approach allowed to gain a deeper knowledge on sediment toxicity, both from a chemical and a biological point of view.