Segui questo link per vedere altri tipi di pubblicazioni sul tema: Sediment salinity.
Tesi sul tema "Sediment salinity"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-34 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Sediment salinity".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Monabbati, Mehran. "Effect of salinity and organic matter content of sediments on the sediment-water exchange of arsenic". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0005/NQ41249.pdf.
Testo completo
2
Cakiroglu, Ayse Idil. "Salinity Inference In Inland Turkish Shallow Lakes On Paleoecology Using Sub-fossil Cladocera". Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615450/index.pdf.
Testo completoAbstract (sommario):
In the current study, sub-fossil Cladocera collected from the surface sediment of 44 shallow lakes spanning over five latitudes from north to south of Turkey using snap-shot methodology revealed strong impact of salinity on cladoceran community structure. To see the whole picture, sediment cores collected from six of the lakes and long-term monitoring data from two of the lakes were also investigated.
Contemporary cladocerans and sub-fossil assemblages were compared to reveal that their responses to salinity changes were highly similar. This lead us to use sub-fossil cladocerans and salinity data from water column together while generating the calibration data set using ordination techniques. Salinity transfer function models were developed utilising weighted averaging techniques. The developed salinity transfer function was applied to cladocera assemblages from dated sediment cores. Hindcasting of the salinity inference model was performed using monitoring data and the reconstructed salinities from two central Anatolian lakes and reflected good linear correlation with the known lake salinity history.
This thesis has confirmed that sub-fossil Cladocera is a valuable indicator of historical salinity change and marker for the monitoring of lakes. For the first time, the lake environmental variables and sub-fossil cladoceran species composition from the surface sediments of Turkish shallow lakes were studied and a salinity transfer function was developed to elucidate past salinity change. The approach of the current study has been proven to be reliable while interpreting past salinity conditions. Since monitoring programmes are scarce in Turkey, paleolimnological analyses would be beneficial especially when defining effective restoration strategies.
3
Yang, Hua. "Influences of tidal and subtidal currents on salinity and suspended-sediment concentration in the Delaware Estuary". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 105 p, 2008. http://proquest.umi.com/pqdweb?did=1459923351&sid=13&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Testo completo
4
Stephens, Christine Elizabeth. "Marine fish carbonates : contribution to sediment production in temperate environments". Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/26195.
Testo completoAbstract (sommario):
In the past, oceans have strongly influenced atmospheric CO2 levels through organic and inorganic carbon cycling. The inorganic carbon pump relies on the formation of calcium carbonate which releases CO2 into the surface ocean and traps alkalinity in solid form which sinks to deeper ocean layers and sediments. After sinking, calcium carbonate can either then become trapped in the sediments or dissolve increasing the alkalinity of deeper ocean layers. The net effect is of acidifying surface oceans and encouraging release of CO2 to the atmosphere. The present thesis focuses on marine teleost (bony) fish in temperate areas as previously poorly understood but potentially major producers of calcium carbonate in the ocean. Fish in temperate areas may be contributing to carbonate sediment production and as such the inorganic carbon pump. Prior to this thesis only tropical fish have been investigated as major piscine sediment producers. The present thesis describes the composition and morphology of carbonates produced by many different species of temperate fish providing a basis for the understanding the fate of these carbonates in the environments and their potential contribution to sediment production and the inorganic carbon cycle. Characteristics of carbonates produced by fish in the wild were fairly consistent within a species upon examination of carbonates produced by poor cod (Trisopterus minutus) over the course of a year. However, despite the likely consistent and distinct characteristics of fish carbonates, little evidence of them was found in temperate shallow sediments beneath pens of farmed Atlantic salmon (Salmo salar) where there theoretically should be very high production rates. Reduced salinity, often a feature of temperate areas compared to tropical areas, was found to reduce production rates of carbonate from fish compared to higher salinities. However, salinity reductions below the ocean average of 35 psu (practical salinity units) had less impact on production rates than increases above 35 psu. As such it is argued that production rates in temperate environments should still be relatively high considering high fish biomasses in some temperate regions and could still mean fish in temperate areas are an important source of carbonate production and potential sediment production.
5
Silva, Camila MagalhÃes. "Detection Aeromonas spp. in surface water samples and sediment along a salinity gradient in river estuary Cocà - CearÃ". Universidade Federal do CearÃ, 2009. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=13386.
Testo completoAbstract (sommario):
This research work was designed to detect the presence of Aeromonas in the Cocà River estuary, Fortaleza, Cearà State, Brazil. The database consisted of 30 samples of the riverâs surface water and 30 samples of the riverâs sooil, in the period from September, 2007 to April, 2008.. They were amenable, simultaneously, to counting of bacteria on Agar Gelatin Phosphate Salt (GSP) plus 20μg/mL of ampicilim (UFC/mL or UFC/g) The results showed dissemination of Aeromonas in the estuary. The counts for the water samples varied from 10 to 7,050 and from 25 to 38,500 UFC/mL at points A and B respectively; and from 100 to 37,500 UFC/g, and 1,200 to 43500 UFC/g at points A and B respectively. At point C, the counts for water and sediment were smaller than 10 UFC per ml or gram in all samples The occurrence of the greatest indices of Aeromonas in April, at the height of the rainy season, and the lowest in Septemer, at the height of the dry season, suggests there to be a probable seasonality of bacteria density in the studied environment. Among the 41 isolated strains were found the species A. caviae, A. sobria, A. trota, A. salmonicida and A. allossacharophyla. All the strains of Aeromonas sp. were found to be sensitive to cloranfenicol and ceftriaxona except for ampicillim, to which they showed 100% resistance.All the stirps showed resistance to two out of the nine tested antibiotics. After the Curingâ technique, the eritromicina resistance seems to be of plasmidian origin.Este projeto teve como objetivo principal a pesquisa de Aeromonas spp. em Ãgua de superfÃcie e sedimento em trÃs pontos distintos ao longo do rio CocÃ, CearÃ. Foram realizadas coletas no perÃodo de outubro de 2007 a abril de 2008 gerando um total de 30 amostras de Ãgua e 30 de sedimento. A quantificaÃÃo da comunidade bacteriana pertencente ao gÃnero Aeromonas foi feita atravÃs de plaqueamento direto sobre Agar Gelatina Fosfato Sal (Agar GSP acrescido de 20μg/mL de ampicilina). Nas amostras de Ãgua, os valores obtidos variaram de 10 a 7.050 UFC/mL e de 25 a 38.500 UFC/mL nos pontos A e B, respectivamente. Nas amostras de sedimento, as contagens variaram de 100 a 37500 UFC/g e 1.200 a 43.500 UFC/g nos pontos A e B, respectivamente. Nas amostras de Ãgua e sedimento do ponto C, os valores foram menores que 10 UFC (por mL ou g) em todas as coletas. As maiores contagens foram verificadas no mÃs de abril, perÃodo de chuva, e as menores no mÃs de setembro, perÃodo de estiagem. Foram feitos isolamentos e apÃs identificaÃÃo as estirpes foram submetidas à teste de antibiograma e à tÃcnica da âcuraâ do plasmÃdio. Dentre as 41 cepas isoladas, foram identificadas as espÃcies A. caviae, A. sobria, A. trota, A. salmonicida e A. allossacharophyla. Todas as cepas se mostraram sensÃveis ao cloranfenicol e ceftriaxona. Todas as estirpes apresentaram resistÃncia a, pelo menos, dois dos nove antibiÃticos testados. ApÃs a tÃcnica de cura, a maior parte da resistÃncia a eritromicina ficou caracterizada como de origem plasmidial.Conclui-se que o estuÃrio do Rio Cocà està contaminado por Aeromonas e que muitas delas apresentam resistÃncias a antibiÃticos denotando um ambiente poluÃdo e de risco para a populaÃÃo que usa suas Ãguas para lazer, pesca ou outra atividade qualquer.
6
Cadaret, Erik M. "Vegetation Canopy Cover Effects on Sediment and Salinity Loading in the Upper Colorado River Basin Mancos Shale Formation, Price, Utah". Thesis, University of Nevada, Reno, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10001481.
Testo completoAbstract (sommario):
With future climate change and increased water demand and scarcity in the Colorado River Basin, the Bureau of Reclamation estimates that the costs of salinity damage will increase for Colorado River users and will exacerbate the current salinity challenges. This study focuses on saline and sodic soils associated with the Mancos Shale formation in order to investigate the mechanisms driving sediment and salinity loads in the Price-San Rafael River Basin of the upper Colorado River. A Walnut Gulch rainfall simulator was operated with a variety of slope angles and rainfall intensities at two field sites (Price, Dry-X) near Price, Utah in order to evaluate how the amount and spatial distribution of vegetation affects salinity in runoff. For each simulated rainfall event, the time-varying concentrations of major cations, anions, and sediment in runoff were measured. Principal component analysis revealed that the two field sites are generally different in runoff water chemistry and soil chemistry, likely due to the difference in parent material and soil indicative of their location on different geologic members. The Dry-X site also has substantially greater total dissolved solids (TDS) and sediment in runoff, soil sodium absorption ratio (SAR), and soil cation exchange capacity (CEC) than the Price site. Despite these differences, a consistent positive linear relationship between the plot-averaged sediment and TDS concentration was found across both sites. The Rangeland Hydrology Erosion Model (RHEM) was calibrated to provide unbiased estimates of sediment in runoff from 23 runs of the rainfall simulator. RHEM simulated the plot-plot variability best at Dry-X compared to Price. Sensitivity analysis of the RHEM input parameters showed that the splash and sheet erodibility coefficient (Kss) and the effective saturated conductivity coefficient (Ke) had the largest influence on the model’s sediment and discharge outputs, respectively. The regression that predicted TDS concentration from sediment was applied to RHEM outputs to show that the model could be used to provide salinity estimates for different storm intensities on this part of the Mancos Shale. The potential influence of vegetation canopy cover on sediment production from these two sites was inferred by running RHEM with canopy cover values ranging from 0% to 100%. This changed sediment output by 111% to -91% relative to the present vegetation cover. Measures of the geometry of soil and vegetation patches at Dry-X, such as fractal dimension index and proximity index, showed a relationship to error residuals from RHEM. As the vegetation becomes less isolated, more uniform, and the tortuosity of the bare soil area increases, observed sediment decreases relative to RHEM predictions. The results of this study will help land management agencies assess the feasibility of mitigation strategies for reducing sediment and salinity loads from the saline and sodic soils of the Mancos Shale formation and indicate a possible benefit to incorporating the parameters that describe the spatial pattern of vegetation in RHEM.
7
Josko, Troselj. "FLUVIAL INFLUENCE ON ESTUARINE SEDIMENT TRANSPORT PROCESSES AND LINKAGE OF ITS OUTFLOW DATA TO COASTAL MODELING". Kyoto University, 2016. http://hdl.handle.net/2433/217745.
Testo completo
8
Zaghmouri, Imen. "Impact des fluctuations de salinité sur le cycle de l'azote dans les sédiments de l'étang de berre". Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4007/document.
Testo completoAbstract (sommario):
Dans l'étang de Berre, les apports excessifs en eau douce entraînent souvent des variations brusques de la salinité et des apports en azote parfois abondants. Les processus de régénération sédimentaire et d'élimination d'azote constituent des phénomènes majeurs pouvant expliquer le développement phytoplanctoniques et contrôler l'eutrophisation. L'étude de ces processus a été réalisée dans 2 stations ayant subi des historiques de variations de salinité différents. RDNA et anammox étaient négligeables. La dénitrification (couplée à la nitrification) serait le principal processus de sortie de N2 de l'étang. La forte production primaire pélagique utilisant l'ammonium a pu être expliquée par les processus de régénération, contrairement au nitrate dont la demande pélagique serait soutenue par des apports externes. Comme la salinité est susceptible d'influencer les processus d'azote, des microcosmes ont été utilisés afin d'évaluer la sensibilité de ces processus (résistance, résilience, shift) face aux variations à court terme de la salinité. Les 2 stations ont présenté des réponses différentes (dénitrification et nitrate réduction plus résilientes que la nitrification), suggérant que les stress halins à long terme influencent les réponses à court terme. Une hypothèse serait que la diversité et la structure des communautés joueraient un rôle crucial dans le maintien des taux d'activité. Dans cette étude, seule la communauté nitrifiante (AO) a été étudiée. Les AO et leurs transcrits étaient spécifiques aux sites et leurs abondances changeaient faiblement entre les microcosmes (résistance plus forte dans le site fréquemment soumis à des fluctuations de salinité)The Berre lagoon receives excess freshwater leading to strong changes in the ecosystem salinity and in the nutrient inputs. Regeneration processes and the N2 removal of nitrogen are of a particular interest as they can explain the planktonic development and control the eutrophication state. These processes were studied in 2 stations with different patterns of long term stresses. DNRA and anammox were negligible. Denitrification (particularly the one coupled to nitrification) would be the main N2 removal in the lagoon. The high primary production based on N-NH4+ can be explained by the regeneration processes, while the primary production based on N-NO3- might be sustained by external inputs. As salinity susceptible to influence directly or indirectly the nitrogen processes, a microcosm approach was used in order to assess their sensitivity (resistance, resilience, shifts) to short term salinity fluctuations. Overall, towards the same kind of perturbations, the two stations responded differently (denitrification and nitrate reduction exhibited showed higher resilience than nitrification.), suggesting that long-term saline stresses would influence short-term responses. We suggest that the diversity and the structure of the communities would be crucial in their functional redundancy and thereby in the maintenance of the rates. In this study, we focused on the total structure of the nitrifying community (AO). AO and their transcripts were site-specific and their abundances changed slightly between microcosms (higher resistance in the site subject to frequent salinity fluctuations compared to the other site which is not affected by changes in the in situ salinity)
9
Benaouda, Abdelkader. "Dynamique saisonnière des sédiments en suspension dans l'estuaire de la Gironde : modélisation opérationnelle de la réponse aux forçages hydrodynamiques". Thesis, Bordeaux 1, 2008. http://www.theses.fr/2008BOR13618/document.
Testo completoAbstract (sommario):
L’objectif de ce travail est d’étudier la dynamique du bouchon vaseux, ainsi que la dynamique saline, dans l’estuaire de la Gironde. La stratégie adoptée consiste à examiner, par le biais du modèle de simulation SIAM-3D, l’impact du paramétrage hydro-sédimentaire, du débit fluvial et de la bathymétrie, sur le comportement des sédiments et sur l’évolution de la salinité. L’effet de la vitesse de chute sur la dynamique sédimentaire est l’un des cas étudiés ; son impact sur la distribution des suspensions est considérable. Ainsi, la diminution de ce paramètre entraîne l’homogénéisation de la concentration sur la verticale, mais aussi l’étalement du bouchon vaseux et l’évacuation d’une masse de sédiment hors de l’estuaire. Nous avons également mis en évidence lors d’une période de débits moyens ou faibles précédée par une crue, la partition du bouchon vaseux simulé en deux masses turbides, l’une remonte l’estuaire alors que l’autre se maintient en aval. La dynamique saline a été étudiée, entre autres, par l’analyse des gradients de salinité, calculés dans l’estuaire aval et en situation de forts débits. On observe, la diminution de ces gradients avec l’augmentation de l’intensité de la marée à l’échelle des cycles vives-eaux/mortes-eaux, toutefois, de fortes valeurs sont maintenues lors de la phase d’augmentation de cette grandeur à l’échelle de la marée. D’autres résultats ont permis de vérifier la capacité du modèle à simuler des dynamiques sédimentaires observées in-situ ; on peut citer entre autres, le détachement du bouchon vaseux de la rive gauche dans l’estuaire aval et son transfert vers la rive droite, en situation de forts débits. Afin d’évaluer l’impact de l’évolution du fond des fleuves de 1959 à 2002 sur l’hydrodynamique et les dynamiques sédimentaire et saline, nous avons comparé deux simulations, l’une effectuée avec l’ancienne bathymétrie de 1959, l’autre avec la nouvelle bathymétrie de 2002. Les résultats montrent l’augmentation de la masse sédimentaire dans les fleuves avec la bathymétrie de 2002 comparée à celle de 1959, ainsi que la hausse de la salinité dans la Garonne et l’amplification de la marée dans la Dordogne. Ces résultats sont en accord avec les mesures et observations in-situThe aim of this work is to study the turbidity maximum dynamics as well as the salinity dynamics in the Gironde estuary. The adopted strategy consists in analysing, by means of the SIAM-3D simulation model, the impact of hydro-sedimentary parameters, the fluvial flow and the bathymetry on sediment behaviour and salinity evolution. The effect of settling velocity on sediment dynamics is one of the studied cases; its impact on suspended sediment distribution is goodly. Thus, the diminution of this parameter leads to homogenisation of concentration in water column, but also spreading the turbidity maximum and evacuation of a sediment mass outside the Gironde estuary. We gave also prominence to the division of the turbidity maximum into two parts during low or mean water flow preceded by peak high water discharge, one of the parts migrates upstream whereas the other remains downstream. We studied the salinity dynamics, among others things, by means of analysing the calculated salinity gradients in the lower estuary during high water discharge. We observe the decrease of these gradients with increase of the tide intensity on a scale of spring tides/neap tides cycles, however, on a scale of tide, these gradients reach high values during the augmentation phase. Others results indicate the model capacity to simulate in-situ observations of the sediment dynamics; for example, the detachment of turbidity maximum from the left bank in the lower estuary and its transfer to the right bank during high water discharge. In order to evaluate the impact of the bed river evolution from 1959 to 2002 on hydrodynamics, sediment and salinity dynamics, we compared two simulations performed using the former (1959) and recent (2002) bathymetries. The results demonstrate that the sediment mass increase in the rivers with recent bathymetry, as well as, the salinity in the Garonne river and the tide amplitude in the Dordogne river. These results are in accordance with the in-situ measures and observations
10
Gao, Chan. "Devenir des substances per et poly-fluoroalkylées (PFAS) dans les estuaires : focus sur les interactions avec les sédiments en suspension". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0409.
Testo completoAbstract (sommario):
Les substances per et poly-fluoroalkylées (PFAS) constituent un vaste groupe hétérogène de micropolluants émergents. Du fait de leur structure physico-chimique très stable, les PFAS sont persistantes et largement répandues dans l'environnement et posent de nombreux problèmes environnementaux. Ces dernières années, le devenir des PFAS a fait l'objet d'une attention croissante. Dans le cycle des PFAS, l'air, l'eau, le sol et les sédiments sont différents compartiments impliqués. À l'exutoire des grands bassins versants et à l’interface terre-mer, les estuaires sont considérés comme la principale voie d’entrée des PFAS vers le milieu océanique, puits ultime des PFAS. Les conditions estuariennes complexes affectent le comportement des PFAS dans les sédiments et déterminent le sort final des PFAS. Les estuaires jouent par ailleurs un rôle écologique majeur et sont soumis à une forte pression chimique, générant des risques environnementaux. Il est donc important d'étudier le devenir des PFAS dans les estuaires.Les sédiments estuariens constituent un réservoir important pour les PFAS, où la sorption et la désorption se produisent et contrôlent la distribution des PFAS. Les conditions géochimiques jouent un rôle essentiel dans ce processus. D'une part, les flux fluviaux apportent d'énormes quantités de particules en suspension qui absorbent les PFAS et se déposent finalement dans les sédiments estuariens. D'autre part, au cours des cycles de marée, les particules sont remises en suspension, transportées et remises en place, désorbant ou réabsorbant les PFAS. La distribution des PFAS entre les particules et l'eau est la clé de l'étude du devenir des PFAS dans les estuaires. Les conditions contrastées de salinité et de turbidité des estuaires peuvent influencer la distribution des PFAS entre les particules et l'eau en facilitant ou en entravant la sorption/désorption, ce qui complique l'interaction entre les sédiments et l'eau pour les PFAS. Il est donc très important de réaliser des études approfondies sur la distribution des PFAS entre les particules et l'eau dans les conditions estuariennes.Ces travaux sont divisés en deux parties : 1) détermination des cinétiques d'adsorption et de désorption des PFAS seuls ou mélange (compétition) sur un substrat modèle, la kaolinite et 2) étudier l'influence de la salinité et de la turbidité sur la distribution particules-eau des PFAS en conditions estuariennes. Ces travaux fournissent des éléments importants pour paramétrer les modèles de devenir des PFAS et estimer les bilans de masse à l'interface terre-merTo understand the fate of legacy and emerging PFAS at the land-sea interface, this work focused on the interactions with estuarine sediments. More precisely, we mainly studied the influence of co-existing PFAS, salinity (S) and suspended particulate matter (SPM) on the sediment-water partitioning of PFAS. First, to investigate the effect of coexisting PFAS on their adsorption and desorption, competitive adsorption and desorption experiments were conducted using single and mixed PFAS solutions at low concentrations, using kaolinite as model sorbent. Selected PFAS include eight perfluoroalkyl carboxylates (PFCAs), two perfluoroalkyl sulfonic acids (PFSAs) and one zwitterionic PFAS (8:2 fluorotelomer sulfonamide alkylbetaine (8:2 FTAB)), which were studied in three single-solute solutions and two mixture solutions. A pseudo-second-order kinetic model was used to fit in the adsorption and desorption kinetics data correctly. Their sorption and desorption on kaolinite were quite fast, with equilibrium reached within 2h. Sorption processes appeared to be influenced by the PFAS molecular structure: sorption increased and desorption decreased with increasing fluoroalkyl chain length, characterized by the increase of log Kd. Besides, PFSAs (i.e, PFHxS and PFOS) had greater sorption and weaker desorption than PFCAs (i.e, PFHpA and PFNA) with similar fluoroalkyl chain. The zwitterionic 8:2 FTAB showed stronger sorption and smaller desorption than anions (i.e., PFOS or PFNA) with a similar fluoroalkyl chain. Sorption and desorption data obtained for single and multi-solute experiments indicated that there was no significant statistical difference between such conditions. Thus, the influence of competitive adsorption and desorption was negligible at low concentrations. To study the influence of salinity and SPM on the sorption of PFAS, we used a sediment sample collected in the fluvial sector of the Garonne-Gironde system. We performed sorption kinetics and sorption isotherms tests for the same PFAS, under 35 combination of salinity and turbidity. Based on response surface methodology (RSM) modelling approach, results indicated the sorption kinetics of PFAS onto sediment can be described by pseudo-second-order model and 24h is the equilibrium time for targeted PFAS. Besides, PFAS sorption can be well fitted by linear model and Freundlich model, the linear sorption range for PFAS studied was in the range of 0.12 to 1.31 nM (equilibrium concentration). Moreover, based on RSM modelling approach, we found that Kd varied between 0.62 and 55271 L/kg and that both S and SPM were significant factors, i.e. the Kd of PFAS was positively related to S due to salting-out effect while it was negatively related to SPM concentration. Moreover, SPM had a stronger effect than salinity (S) for PFHxA and PFHpA, whereas S was the more dominant factor for most other compounds. For PFUnDA and 8:2 FTAB, S and SPM displayed nearly equivalent weights as drivers of Kd. In addition, a negative interaction between both factors was observed, i.e. if SPM increases, the effect of S on Kd is weaker. Overall, this work provides original results to model the sorption of legacy and emerging PFAS on estuarine sediments based on RSM modelling approach. It provides a new perspective to investigate the fate of PFAS at the land-sea interface
11
Dale, Ryan. "Salinity, temperature, and macroinfaunal communities in groundwater seeps". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 9.34 Mb., p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1435921.
Testo completo
12
Vinson, Joshua S. "Role of oxygen and salinity on biogeochemical processes controlling mercury and monomethylmercury flux from estuarine sediments". View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-2/r1/vinsonj/joshuavinson.pdf.
Testo completo
13
Lancaster, Nicole N. M. "Effects of salinity on biogeochemical processes and methylmercury production in freshwater wetland sediments". View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-3//r1/lancastern/nicolelancaster.pdf.
Testo completo
14
Gilmour, Fiona Louise. "The effect of salinity and ammonia on nitirifier function and distribution in estuarine sediments". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=59375.
Testo completo
15
Moate, Benjamin D. "Optical Remote Sensing of Sediments and Phytoplankton Pigments in an Estuary: towards retrieving eDOM and Salinity". Thesis, Bangor University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485826.
Testo completoAbstract (sommario):
In recent years, remote sensed measurements of sea surface salinity have been identified as a key requirement in mixing and pollution studies. Existing methods of remote sensing salinity are largely limited to microwave radiometry, which operates on the principle that the microwave emissivity of the sea is strongly salinity dependent. Orbiting microwave radiometry sensors (SMOS) however, lack the spatial resolution to adequately resolve most estuaries, whilst airborne microwave radiometry is subject to radio frequency interference, and is therefore often unreliable in estuarine regions that are near cities. In many estuaries, the concentration of coloured dissolved organic matter (CDOM) shows a strong, linear relationship with salinity, since it mainly enters estuaries through land runoff. The aim of this study, was to develop a method by which the concentration of CDOM, and hence salinity, could be derived from remote sensed water colour in the optically complex Conwy Estuary. To achieve this aim, measurements of the specific inherent optical properties of the dominant optically active in-water constituents (OICs) were made, and in-situ measurements of water colour collected to enable both forward and inverse modelling of water colour. Airborne remote sensed water colour was obtained in the estuary during spring, summer, and autumn months to test the success of the developed inversion technique. Specific eDOM absorption was determined spectrophotometrically, whilst specific absorption coefficients (a*) of mineral suspended solids (MSS) and phytoplankton pigments (PIG) were measured for particles concentrated on filter papers, using the Qualitative Filter Pad (QFP) technique. Measurements collected over two years showed a clear seasonal variation in the shape of the a*PlG spectra, with an exponential shaped spectra present in winter months and a twin peaked shaped spectra, typical of chlorophyll a, present in summer. A simple time varying model of a*PIG was thus developed, and enabled the forward modelling of pigment absorption to within an RMS error of 0.07 mol. Multivariate linear regression was employed to retrieve a*.\[55, which along with the time varying model of a*PlG was used to forward model total particle absorption to within an RMS error of 0.37 mol for an independent dataset. Backscattering in the Conwy Estuary was found to be dominated by MSS, and was relatively wavelength independent. FOI'\vard modelled water colour showed close agreement to the in-situ values, within measurement uncertainties, and revealed that whilst MSS significantly affected all colour ratios, the irradiance reflectance at far-red wavelengths was dominated by water and MSS alone. In addition, modelled far-red/red colour ratios were seen to be dominated by MSS and pigments, whilst far-red/green colour ratios were dominated by MSS and CDOM. Theoretical water colour inversion methods were tested using an in-situ dataset, and included both solving simultaneous equations of water colour and over-determined matrix inversion. The results of both techniques were inadequate, and analysis using synthetic data showed both techniques were highly susceptible to small measurement uncertainties in the measured colour ratios. An alternative spectral windowing inversion technique was therefore developed, in which the far-red irradiance reflectance was used to obtain the concentration of MSS, the far-red/red colour ratio was used to obtain the concentration of pigments, and the far-red/green colour ratio used to obtain the concentration ofCDOM. Remote sensed estimates ofMSS concentration were in excellent agreement with values determined in-situ, and showed the presence of a turbidity maximum in the upper reaches of the estuary. The axial gradients of remote sensed pigment concentration were also in close agreement to those observed in the in-situ values, and both showed a twin peaked phytoplankton maximum was also present in the Conwy Estuary, slightly seaward of the turbidity maximum. Remote sensed estimates of eDOM concentration were less accurate, with the most successful estimates overestimating high concentrations, whilst underestimating low concentrations. This was largely attributable to inaccuracies in the atmospheric correction of the remote sensed data. Nevertheless, the remote sensed CDOM concentrations were used to produce remote sensed salinities that revealed a very similar axial variation in salinity from the mouth to the head of the estuary as that observed in-situ.
16
Theobald, Kylie. "Comparative tolerances of non-indigenous bridled goby and native exquisite goby to salintiy, temperature and sediment". The University of Waikato, 2007. http://hdl.handle.net/10289/2370.
Testo completoAbstract (sommario):
The Australian bridled goby (Arenigobius bifrenatus) has been in New Zealand since 1996, and has subsequently spread to thirteen estuaries and the coastal Otara Lake. The native exquisite goby (Favonigobius exquisitus) may be displaced or threatened by the bridled goby as they share estuarine habitat. The ecophysiological tolerances and sediment preferences for both goby species were examined to determine the potential for niche overlap and habitat selection. The results of acute salinity and temperature tolerance tests supported the hypotheses that bridled gobies are more tolerant than exquisite gobies to extremes of salinity and temperature. The incipient ten day LT50 values were 6.7 C and 11.8 C for bridled and exquisite gobies, respectively, however, both tolerated temperatures up to 35 C. Both species showed some mortality at low salinities, but mortality did not exceed 50% for either species at the lowest salinity tested (2.2 ppt) after 96 h. Bridled gobies displayed a strong preference for fine sediment (less than 63 um), whereas exquisite gobies were less selective, accepting a broad range of sediment grain sizes (63-250 um). Bridled gobies have successfully established and dispersed in New Zealand, and their ecophysiological adaptations that allowed them to survive harsh conditions in ballast water, their presumed introduction vector, will likely aid their future spread throughout New Zealand. Their increasing abundance is likely to see them encounter and possibly encroach on the habitat of exquisite gobies. Bridled gobies may displace the smaller exquisite gobies from optimal habitats, as exquisite gobies are unlikely to survive competition from and predation by bridled gobies. However, exquisite gobies should be able to relocate to adjacent habitat with coarse sediment that is unsuitable for burrow construction by bridled gobies. Additionally, acclimatisation to local environmental conditions may extend the tolerance limits determined in this thesis, and may allow bridled gobies to spread to upstream zones in estuaries and occupy freshwater. New Zealand presently has eight recognised gobiid species of which one is endemic, two are native, two are not recorded in mainland waters and three are proposed as non-indigenous. Additionally, several tropical and subtropical gobies exist in the aquarium trade. Similar ecophysiological tests of tolerance and preference may determine the possibility that these species could establish in the wild following accidental release.
17
Owens, Stephanie Anne. "Advances in measurements of particle cycling and fluxes in the ocean". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79284.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2013.Cataloged from PDF version of thesis.
Includes bibliographical references.
The sinking flux of particles is an important removal mechanism of carbon from the surface ocean as part of the biological pump and can play a role in cycling of other chemical species. This work dealt with improving methods of measuring particle export and measuring export on different scales to assess its spatial variability. First, the assumption of ²³⁸U linearity with salinity, used in the ²³⁸U-²³⁴Th method, was reevaluated using a large sample set over a wide salinity range. Next, neutrally buoyant and surface-tethered sediment traps were compared during a three-year time series in the subtropical Atlantic. This study suggested that previously observed imbalances between carbon stocks and fluxes in this region are not due to undersampling by traps. To assess regional variability of particle export, surface and water-column measurements of ²³⁴Th were combined for the first time to measure fluxes on ~20 km scales. Attempts to relate surface properties to particle export were complicated by the temporal decoupling of production and export. Finally, particle export from ²³⁴Th was measured on transects of the Atlantic Ocean to evaluate basin-scale export variability. High-resolution sampling through the water-column allowed for the identification of unique ²³⁴Th features in the intermediate water column.
by Stephanie Anne Owens.
Ph.D.
18
Björk, My, e Linn Månsson. "Mikroplasters spridning längs den svenska västkusten - En studie om koncentration och distribution av mikroplaster i marina sediment". Thesis, Malmö högskola, Fakulteten för kultur och samhälle (KS), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-22550.
Testo completoAbstract (sommario):
På senare år har ett nytt forskningsområde kring mikroskopiska plastfragment i marin miljö,kallat mikroplaster, vuxit fram. Mikroplaster härstammar från antropogena källor somavloppsreningsverk och vid fragmentering av makroplast. Det finns ett begränsat antal studierinom området, särskilt vad gäller svenska vatten, vilket innebär att det finns utrymme för merforskning. För att bidra till forskningen har föreliggande studie undersökt sedimentprover frånlitoralen vid sju olika platser längs svenska västkusten samt ett sedimentprov från djupt vattenvid en av platserna. För att undersöka koncentration och distribution av mikroplaster utfördeskorrelationsanalys längs den svenska västkusten mellan mikroplaster och två variabler;kornstorlek och salinitet. Resultatet visade att högst koncentration av mikroplaster återfannsvid Sveriges västkust norra delar och minskade ju längre söderut proverna togs.Förklaringsgraden R2 = 0, 61 visade stark korrelation mellan koncentration mikroplaster ochhög salinitet, samt fanns en korrelation mellan mikroplaster och grov sand medförklaringsgraden R2 = 0,38. Resultaten bidrar till ökad förståelse för hur mikroplasterdistribueras i marin miljö vid den svenska västkusten. Forskarna uppmanar till flerprovtagningar i havets alla zoner för att bättre förstå hur mikroplaster koncentreras ochdistribueras i marin miljö.In recent years, a new research field regarding microscopic plastic fragments in the marineenvironment, called microplastics, have emerged. Microplastics derives from anthropogenicsources such as sewage treatment plants and the fragmentation of macro plastic. There are alimited number of studies regarding micro plastics, especially concerning Swedish waters,indicating the need for more research. In this study sediment samples were collected from thelittoral area at seven different locations as well as one sediment sample from a deep sea at oneof the sites. The aim is to investigate the concentration and distribution of microplastics alongthe Swedish west coast. A correlation analysis was performed between microplastics and twovariables; grain size and salinity. The results showed that the highest concentration of microplastics were found at the north part of the Swedish west coast and decreased the farther souththe samples were taken. The results showed a strong correlation between microplastics andhigh salinity R2 = 0, 61, and a correlation was seen between micro plastics and coarse sandwith a R2 = 0.38. The results contribute to the understanding of how micro plastics aredistributed in marine environment along the Swedish west coast. The researchers behind thisstudy calls for sampling of all marine zones to further understand how microplastics areconcentrated and distributed in the marine environment
19
Al, Mallah Maha. "Biodegradation des hydrocarbures dans les milieux sursales". Aix-Marseille 2, 1988. http://www.theses.fr/1988AIX22040.
Testo completo
20
Lee, Wen-Hsiung. "The effect of salinity on nutrient release from riverine and tributary estuarine sediments to the Chesapeake Bay under oxidizing and reducing conditions". Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/80053.
Testo completoAbstract (sommario):
The primary objective of this study was to determine the salinity effect on nutrient release and the denitrification rate in a sediment-water system. To accomplish this objective, bench-scale microcosm studies of York River sediments and Occoquan Reservoir sediments were conducted. Seawater and freshwater were mixed in various ratios to simulate seasonal, salinity-varying environments in the Chesapeake Bay and its tributary estuaries.
Experiments were conducted under aerobic, anaerobic, and anoxic conditions. The results showed that high salinity can cause flocculation of particles and result in lower concentration of phosphate under aerobic conditions, but the flocculation effect was not obvious under anaerobic conditions. The release of ammonia was governed by the salinity; the increasing salinity accelerated the release of ammonia by ion exchange. The denitrification rate under anoxic conditions in the system was not influenced by the salinity.Master of Science
21
Monteiro, Maria Rovisco Correia Gonçalves. "Dynamic of estuarine prokaryotic communities and the nitrogen cycle". Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/12738.
Testo completoAbstract (sommario):
Mestrado em MicrobiologiaEstuaries are highly dynamic aquatic systems, having steep physical and chemical gradients, such as salinity, influencing microbial communities in terms of their abundance and diversity. The analysis of microbial responses and adaptations to those environmental fluctuations became essential to understand the biogeochemical cycles that regulate these ecosystems, which have been undergoing progressive anthropogenic pressures. In this study, we investigated the dynamics of Archaea and Bacteria diversity along the salinity gradient of the Douro River estuary (NW Portugal). Samples were collected at four locations covering the salinity gradient, ranging from 4.9 - 21.7 ppt. The application of denaturing gradient gel electrophoresis (DGGE) showed a variation of Bacteria and Archaea diversity along the salinity gradient. The diversity of ammonia oxidizing Archaea (AOA) was also assessed by the analysis of amoA diversity. Simultaneously, were measured net fluxes of inorganic nitrogen (NH4+, NO3-, NO2-) and nitrification rates by using acetylene and 15N isotope analysis. The results showed that although there was an increase in the diversity of AOA with the decrease of salinity, the highest magnitudes of nitrification rates were registered at intermediary saline sites, where there was a higher availability of NH4+. This study revealed important insights on the effect of salinity on estuarine prokaryotic diversity structure as well on the dynamics of key processes of the nitrogen cycle.
Estuários são ecossistemas aquáticos altamente dinâmicos, possuindo grandes gradientes físicos e químicos, como é o caso da salinidade, influenciando as comunidades microbianas em termos de diversidade e abundância. A análise das respostas e adaptações destas comunidades às flutuações ambientais torna-se essencial para a compreensão dos ciclos biogeoquímicos que regulam estes ecossistemas, que tem vindo nos últimos anos a sofrer pressões ambientais devido à crescente atividade antropogénica. Neste estudo, investigámos a dinâmica da diversidade de Archaea e Bacteria ao longo de um gradiente de salinidade no estuário do Rio Douro (NW, Portugal). As amostras foram recolhidas em quatro locais cobrindo um gradiente de salinidade que variou entre 4.9 - 21.7 ppt. A aplicação da técnica de electroforese em gel com gradiente desnaturante (DGGE), revelou uma variação na diversidade de Bacteria e Archaea ao longo do gradiente salino. A diversidade das comunidades de Archaea com a capacidade de oxidar a amónia (AOA) foi também avaliada através da análise de diversidade do gene funcional amoA. Paralelamente, foram avaliados os fluxos líquidos dos compostos de azoto inorgânico (NH4+, NO3-, NO2-) bem como as taxas de nitrificação através da utilização do método do acetileno e da análise isotópica de 15N. Os resultados mostraram que apesar de ter ocorrido um aumento da diversidade das AOA com a diminuição da salinidade, as maiores magnitudes das taxas de nitrificação foram registadas nos locais com salinidades intermédias, onde se registou maior disponibilidade de NH4+. Este estudo permitiu-nos obter importantes conhecimentos sobre o efeito da salinidade na estrutura das comunidades procariotas estuarinas bem como na dinâmica de processos chave do ciclo do azoto.
22
Wu, Tai Hsiao, e 吳岱曉. "Salinity Influence on Heavy Metal Remobilizaation from Estuarine Sediment". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/01584090849716645113.
Testo completoAbstract (sommario):
碩士嘉南藥理科技大學
環境工程與科學系暨研究所
91
With the laboratory control, the aim of this study is to realize the effect of salinity on the distribution of heavy metal between dissolved and five heavy-metal binding fractions in river sediment as well as on the remobilization of metals from different size of particles. Heavy metals could be adsorbed onto suspended particulate and sediments with different particle sizes when they were discharged into the river. When sediment flowed through estuary and mixed with overlying water containing different salinity, the remobilized metals (Cd, Co, Cr, Cu, Ni, Pb, and Zn) concentration from different size of particles increased with the increase of salinity. The smaller the particle size was, the lower concentration of metals remobilized. Cd was remobilized from fractions of exchangeable and carbonates with the action of salinity. Similarly, Co and Cu was remobilized from carbonates fractions; Cr from Fe and Mn oxides fractions; Ni and Pb from Fe and Mn oxides and organic matters fractions; Zn from carbonates and Fe and Mn oxides fractions. The partitioning coefficients (KF1DSP, KF2DSP, KF3DSP, KF4DSP, and KF5DSP) of heavy metals between dissolved phase and five heavy-metal binding fractions were affected by salinity in sediment particles. The increase of salinity induced the decrease of KDSP, when the equilibrium of metals existed between particle and dissolved phases. The significant variation of one KDSP value with salinity means the easier release of heavy metals from one binding fraction to the dissolved phase. From the results the more significant variations of KDSP value were from KF1DSP and KF2DSP for Cd; from KF2DSP, KF3DSP, and KF4DSP for Co and Pb; from KF3DSP for Cr; from KF2DSP, and KF4DSP for Cu; from KF3DSP, and KF4DSP for Ni; and from KF2DSP,and KF3DSP for Zn. The amounts of heavy metals remobilized from sediment with larger particle sizes and higher salinity were larger than these from sediment with smaller particle sizes and lower salinity environment.
23
Hong, Yongseok. "Experimental and mathematical investigation of dynamic availability of metals in sediment". Thesis, 2009. http://hdl.handle.net/2152/24031.
Testo completoAbstract (sommario):
Contaminated sediments are periodically subjected to resuspension processes during either storm events or due to dredging. In sediments, metals are often contained in insoluble low bioavailability forms. Upon resuspension, however, biogeochemical processes associated with the exposure to more oxic conditions may lead to transformation and release of the metals, giving rise to exposure and risk in the water column. Batch experiments suggested that oxidation of reduced species and corresponding pH decrease were the most importance processes controlling metals release upon sediment resuspension. A mathematical model was implemented to better understand the complex underlying biogeochemical reactions that affect metals release. The model described the metals dynamics and other inter-related important biogeochemical factors well and was successful at predicting the metals release from different sediment reported in the literature. Tidal and other cyclic variations in oxygen, pH and other relevant parameters in the overlying water may also lead to cyclic transformations and release of metals from surficial sediments. In simulated estuarine microcosm experiments, cyclic variations in pH and salinity due to freshwater/saltwater exchange were shown to lead to cyclic variations in metal release. Both pH and salinity were important factors controlling interstitial dissolved metals concentrations, however, in terms of freely dissolved metals concentrations, which have been considered to be more related with toxicity and bioavailability, pH was the single most important parameter. The mathematical model was extended to the conditions of the cyclic behavior in an estuary and successfully described metals release under such conditions. It is believed that the model can be used to predict the metals behavior in other sediments and conditions by model calibration with a similar experimental approach to that used in this study.text
24
Theobald, Kylie. "Comparative tolerances of non-indigenous brindled goby and native exquisite goby to salinity, temperature and sediment". 2007. http://adt.waikato.ac.nz/public/adt-uow20070510.130422/index.html.
Testo completo
25
Lee, Chun-Hsien, e 李俊賢. "Modeling Salinity and Suspended Sediment in Tidal River of Danshuei River Estuarine System with Three-Dimensional Model". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/y8qv5u.
Testo completoAbstract (sommario):
碩士國立中央大學
水文所
94
Estuaries and tidal rivers are the primary conduit between river and coastal ocean. Estuaries are the semi-enclosed coastal water body which connects with the open sea, and they have the characteristics of inland river, such as flood and dry seasonal variations due to runoff. They also exhibit the characteristics of ocean, such as the flood and ebb tides. Therefore, the hydrodynamics and salinity characteristics of the estuary and tidal river are extremely complicated, and they also affect the transport processes of suspended sediment. The Danshuei River system is the largest estuary system in Taiwan and consists of three major tributaries: Tahan Stream, Hsintien Stream and Keelung River. In this study, the measured salinity and suspended sediment data including slackwater and intense surveys were collected in the periods of 2002 to 2004. The measured stations along the Danshuei River to Tahan Stream and Danshuei River to Keelung River were conducted, respectively, from 2002 to 2003, and in 2004. A real-time, three-dimensional Hydrodynamic-Eutrophication Model (HEM-3D) was performed and applied to simulate salinity distribution and transport of suspended sediment distributions in Danshuei River estuarine. The boundaries of upstream (i.e. the Tahan Stream, Hsintien Stream, and Keelung River) are specified with constant freshwater discharge, salinity (with zero), and suspended sediment concentration. The downstream boundary is extended to the adjacent coastal sea and specified with tidal elevation, salinity, and suspended sediment concentration. Governing Equations are formulated in curvilinear-orthogonal horizontal coordinates and a sigma vertical coordinate. The comparisons of simulated result and field measurement in salinity and suspended sediment distributions were used to investigate and analyze the salinity stratification phenomenon and estuarine turbidity maximum (ETM) in the estuarine system. Moreover, the model sensitivity analyses were used to identify the vital parameter in the suspended sediment transport model. Finally, the numerical experiments were conducted with no saline effect, no sediment supply from the sediment bed, wind stress effect, and the influence by mean freshwater discharge to comprehend the influence on residual current and suspended sediment distribution in the Danshuei River estuarine system.
26
(9875186), S. Vinochandra. "Stochastic dynamic programming for salinity management in reservoir testing". Thesis, 1995. https://figshare.com/articles/thesis/Stochastic_dynamic_programming_for_salinity_management_in_reservoir_testing/13425257.
Testo completoAbstract (sommario):
Project develops a stochastic dynamic programming technique for the optimal operation of a reservoir, to control salinity in the reservoir and thereby also in releases. These procedures are to meet irrigation and municipal demands.. A stochastic dynamic programming technique for the optimal operation of a reservoir to control salinity in the reservoir and thereby also in the releases, and to meet irrigation and municipal demands is developed. The technique defines the optimal policy for releases to meet salinity and irrigation water supply requirements. The problem for which the approach was specifically developed is characterised by the presence of a strongly stratified, essentially two-layer, condition in a reservoir used to supply irrigation water. The two-layer condtion exists over the winter months when cold and heavy saline flows enter the reservoir and flow to the bottom of the reservoir. The two-layer condition continues until mixing of the reservoir occurs in early summer. While the reservoir is stratified, it is possible to flush the saline water out of the reservoir by low level intakes. This flushing reduces the overall salinity level in the reservoir when mixing occurs at end of winter, and thereby reduces the salinity of reservoir summer. However, removing the saline bottom layer also reduces the volume of water available for irrigation. Hence there are limitations on the amount that can be withdrawn to reduce the salinity. The technique is an approach to optimising the performance of the reservoir to meet irrigation demands, while minimising salt concentration in the irrigation water. Stochastic dynamic programming is used to reflect the uncertainty in the inflows while chance-constraints are reservoir beginning of the irrigation season. Three different probabilistic nature of the salt inflows to the reservoir: 1) salt load is directly related to the volume of inflow, 2) salt load is independent of the volume of the inflow, and 3) salt load is conditioned on the volume of inflow. The model is demonstrated by application to the Wellington Reservoir in Western Australia for the case in which the salt load is conditioned on the inflow. The results of the application of the model for a range of different combinations of maximum allowable saltconcentration and probability of exceeding that are compared to each other and to the release policy generated in an earlier simulation analysis undertaken to manage the salinity question.
27
WEI, ZHI-RONG, e 魏志榮. "The effects of photosynthetic bacteria (Rhodopseudomonas capsulatus) on sediment and water under various temperature, salinity and light intensity regime". Thesis, 1990. http://ndltd.ncl.edu.tw/handle/10058397371848666409.
Testo completo
28
Bringué, Manuel Alain. "High resolution dinoflagellate cyst sedimentary records of past oceanographic and climatic history from the Northeastern Pacific over the last millennium". Thesis, 2015. http://hdl.handle.net/1828/6407.
Testo completoAbstract (sommario):
This thesis contributes to the development of dinoflagellate cysts as indicators of past environmental change in the Northeastern Pacific coastal ocean, and investigates past variations in sea-surface temperature, salinity and primary productivity encoded in dinoflagellate cyst sedimentary records from the Santa Barbara Basin (SBB, southern California) and Effingham Inlet (Vancouver Island, British Columbia) over the last millennium. The dinoflagellate cyst records extracted from the SBB and Effingham Inlet predominantly laminated sediments and analysed at sub-decadal resolutions, constitute some of the most detailed records of cyst-producing dinoflagellate populations in the world.
A two year-long sediment trap study from the SBB documents the seasonality in dinoflagellate cyst production for the first time on the Pacific coast of the United States. The study shows that dinoflagellate cyst data can be used as indicators of changes in sea-surface temperature and primary productivity associated with seasonal upwelling in the SBB. In particular, several dinoflagellate cyst taxa such as Brigantedinium spp. and Lingulodinium machaerophorum are identified as indicators of “active upwelling” (typically occurring in spring and early summer) and “relaxed upwelling” conditions (fall and early winter) at the site, respectively.
Analysis of a dinoflagellate cyst record from the SBB spanning the last ~260 years at biannual resolution documents the response of cyst-producing dinoflagellates to instrumentally-measured warming during the 20th century, and reveals decadal scale variations in primary productivity at the site that are coherent with phases of the Pacific Decadal Oscillation (PDO). The cyst assemblages are dominated by cysts produced by heterotrophic dinoflagellates (in particular Brigantedinium spp.), but the turn of the 20th century is marked by an abrupt increase in concentrations of L. machaerophorum and Spiniferites ramosus, two cyst taxa of autotrophic affinity. Their increasing abundances during the 20th century are interpreted to reflect warmer conditions and possibly stronger stratification during summer and fall. The dinoflagellate cyst data suggest a warming pulse in the early 1900s and provide further evidence that persistently warmer and/or more stratified conditions were established by the late 1920s.
The dinoflagellate cyst record from Effingham Inlet, spanning the last millennium, is characterized by the proportionally equal contribution of cysts produced by autotrophic and heterotrophic dinoflagellates in most samples. The cyst data indicate variations in sea-surface temperature, salinity and primary productivity that are associated with local expressions of the Medieval Climate Anomaly (from the base of the record to ~1230), the Little Ice Age (from ~1230 to ~1900) and warming during the second half of the 20th century.
Both dinoflagellate cyst records reveal that since the beginning (in the SBB) and mid-20th century (in Effingham Inlet), autotrophic dinoflagellates contribute to a greater portion of the primary production in the region, whereas heterotrophic dinoflagellates, as indicators of diatom populations, decline. Variability in the dinoflagellate cyst data is coherent at both sites and suggest a reduced expression of decadal scale variability associated with the PDO during the 19th century.Graduate
0416
0427
mbringue@uvic.ca
29
Hancock, Gary J. "The effect of salinity on the concentrations of radium and thorium in sediments". Master's thesis, 1993. http://hdl.handle.net/1885/116106.
Testo completoAbstract (sommario):
The effect of salinity on the sorption behaviour of radium and thorium has
been studied with the aim of assessing the suitability of the 226Ra/232Th
activity ratio (AR) as a tracer in saline waters. Radium has been reported
in the literature as being highly mobile in saline water, and easily
desorbed from sediments, whereas thorium is believed to remain tightly
bound. Results of analyses of bed sediments from an inland river system
with a record of past regimes of high dissolved salt concentrations were
consistent with this behaviour. Radium-226 activity in the bed sediments
was shown to be deficient with respect to its parent, 23°Th, indicating a
loss of radium from the sediments.
A more detailed field study examined the extent of radium loss as a
function of salinity in an estuary. Desorption of ²²⁶Ra from freshwater
suspended sediment increased to a maximum value (58% ±7 of the total
sediment concentration) as the salinity of the estuary rose. Maximum
radium desorption was reached in the 6-10 ppt salinity range. Net
desorption then remained unchanged despite further rises in salinity.
Laboratory experiments indicated that the kinetics of radium desorption is
rapid, with maximum desorption from river sediments reached within 1 h of
contact with saline water. The net radium loss from freshwater sediment
occurs as a result of the competition effects from other dissolved cations
for ion-exchange sites on the sediment. Cation exchange is probably the
dominant mechanism of radium release, although alpha recoil appears to be
at least partly responsible for the higher losses of ²²⁴Ra and ²²³Ra by
increasing their accessibility for ion-exchange reactions.
The effects of solid/liquid ratio and particle size of the sediment on
radium sorption in saline water were also investigated. The results
indicate that, when exposed to saline water, the greatest radium loss from
freshwater sediments will occur from clay sized particles when they are
present in the water column at low concentrations. Proportionally less
radium is desorbed from coarse-grained bed sediments. There was no evidence of any net loss of thorium from sediment as salinity
is increased. In fact, laboratory experiments indicate that the transfer
of dissolved or colloidal thorium onto sediment particles is enhanced in
saline water. From the differing sorption behaviour of radium and thorium
it is concluded that the ²²⁶R a / ²³²Th AR is not a suitable sediment tracer
in saline water. However, the 23° T h / ²³²Th AR can provide a stable tracer
of sediment movement in estuaries and is the preferred sediment tracer in
saline rivers. In some circumstances the ²²⁸R a/²²⁶Ra AR may also be
useful. The dissolved concentrations of all radium isotopes show strongly
non-conservative increases in the Bega estuary. The shorter-1 ived
isotopes, ²²⁴Ra, ²²³Ra and ²²⁸Ra are particularly highly enriched. The
most likely source of these isotopes is the pore water of bottom sediments.
This work has shown that radium isotopes may give information on the rates
and extent of surface-pore water mixing in an estuary.
30
Guido, Adriano, e Franco Russo. "Il calacare di base e la materia organica associata: un approcio multidisciplinare per la caretterizzazione dei sedimenti precursori della crisi di salinità messiniana". Thesis, 2013. http://hdl.handle.net/10955/244.
Testo completo
31
Lin, Zih-An, e 林子安. "Influence of Salinity to the Internal Phosphorus Release and Distribution in Sediments under Aerobic and Anaerobic Environment". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/pu34fj.
Testo completoAbstract (sommario):
碩士國立中興大學
土壤環境科學系所
107
Phosphorus (P) is an essential macromineral for plant growth, but the excessive application of P fertilizer transport large amount of P from agricultural land into rivers, lakes and oceans. The transportation process of P also cause the water pollution. Moreover, the P storage is only sufficient for a few decades, so it is important to estimate the P solubility and understand the transportation and transformation of P between agricultural land and the sea. This study investigated the surrounding area of Kaomei wetland, including farmland land and sediment, and used and sequential extraction method (SEDEX) experiment to understand the species transformation in aerobic and anerobic environment with various salinities. In the field investigation, the total calcium, phosphate and iron concentration in the upstream sediment are the highest. First part of incubation result showed that the dissolved inorganic phosphate concentration would increase with the increasing water salinity under aerobic environment with different water salinity, especially for the iron adsorbed phosphate (Fe-P) are the major phosphate species in the sediment. On the species distribution result by SEDEX, in the higher salinity treatment, the Fe-P species would decrease and exchangeable phosphate (Ex-P), organic phosphate (Org-P) and calcium bound phosphate (Ca-P) species would increase. It not only caused the liable phosphate species percentage elevate but also made the sediment could be the internal pollution source of phosphate. Moreover, the Fe-P species percentage of the sediment by SEDEX had the agreement with the LCF result by P K-edge X-ray absorption spectroscopy. Second, in the anaerobic experiment, after the Eh value decreased, the total dissolved phosphate concentration increased due to the reduction of the Fe3+ on the sediment. Under the salinity treatment, the more phosphate is released from detrital inorganic phosphate (Detri-P) and Fe-P. Otherwise, by the S K-edge XANES result, the intensity of the higher valence sulfur species (+6) enhanced with the higher salinity, we assumed that the addition of sulfate in the salinity caused it bind to the sediment. To sum up the above experiment, when the sediment transported in the river and finally deposit in the estuaries or wetlands, the dissolved phosphate concentration would exceed the standard of water eutrophication (0.02 mg L-1) and the Fe-P species are the main source, in the anaerobic environment, the Detri-P viewed as the structure stable species also could release the phosphate, calcium and Fe2+. The results could be used in the future to estimate the solubility of phosphorus and sulfate addition in agricultural soil which could perform management strategies to reduce P pollution in agriculture production and evaluate the potential internal phosphate pollution risk in the river or estuaries.
32
Weston, Nathaniel B. "Biogeochemistry in the coastal zone changing land use, salinity intrusion, porewater stoichiometry and the mineralization of organic matter in estuarine sediments /". 2005. http://purl.galileo.usg.edu/uga%5Fetd/weston%5Fnathaniel%5Fb%5F200508%5Fphd.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Georgia, 2005.Directed by Samantha B. Joye. Includes articles submitted to Water research, Global biogeochemical cycles, Biogeochemistry, and Proceedings of the National Academy of Sciences. Includes bibliographical references.
33
Chou, Ping-I., e 周秉毅. "Effects of Dissolved Oxygen, pH, Salinity and Natural Organic Matter on the Kinetics of Oxidative Dissolution of Sedimental Metal Sulfides". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/59527196464711185105.
Testo completoAbstract (sommario):
碩士國立臺灣大學
環境工程學研究所
103
Metal sulfides can stabilize toxic soluble heavy metals in anaerobic sediments. However, sediments may suspend and expose to aerobic conditions during storm events or in the estuary with tidal effects. This may cause oxidative dissolution of metal sulfides and increase metal bioavailability that can harm the ecosystem. The objective of this research is to investigate the effects of dissolved oxygen (DO), pH, natural organic matter (NOM) and salinity on the kinetics of oxidative dissolution of copper sulfide (CuS), lead sulfide (PbS) and zinc sulfide (ZnS). Batch experiments were conducted using a continuous aeration setup that can control the dissolve oxygen concentrations (0 mg/L, 5mg/L and 8.4 mg/L) for a period of 3 d. Results demonstrated that oxidative dissolution of CuS, PbS and ZnS truly occur in the presence of DO and the rate showed the following sequence: PbS >CuS>ZnS. Low pH and high salinity generally cause more and faster metal release. Humic acid can inhibit the metal release of CuS and PbS but promote the metal release of ZnS. FE-SEM analysis showed that the morphology of three metal sulfides became rounded and aggregated in the 10mg/L HA reaction, morphology change of CuS also found in brackish water reaction but PbS and ZnS had no changed.
34
O'Brien, Mary C. "Physical processes and biogeochemistry of particle fluxes over the Beaufort slope and in Canada Basin". Thesis, 2009. http://hdl.handle.net/1828/1669.
Testo completoAbstract (sommario):
Sedimentation rates and compositions of sinking particles were investigated at three sites on the Beaufort slope and one in Canada Basin during the period 1990-1994 using moored sequential sediment traps. A method was developed to identify the terrigenous and biogenic components of the fluxes. The physical context including ice cover, ocean currents, river inputs, winds, air temperature, incident light, and nutrient availability provide essential information to the interpretation of the particle fluxes and to the understanding of shelf-basin sediment transport in this area. Eddies, internal waves, upwelling and downwelling, and the state of the ice cover all played important and overlapping roles in the pattern of observed fluxes. A peak in the flux of highly terrigenous material under complete ice cover in mid-winter to the northwest of Mackenzie Trough was associated with predominantly downwelling conditions and the passage of a series of eddies and internal waves. A prolonged spring diatom bloom occurred in the mid-slope area and was clearly associated with an early opening of the ice on the east side of the shelf. Higher fluxes at the Canada Basin site were associated with a large eddy clearly identifiable from the current-T-S record and also from the composition of the suspended material carried with it. At the base of the slope (2700 m), the composition was highly terrigenous and remarkably consistent. Higher up the slope (700 m), biogenic peaks in the summer diluted the terrigenous material briefly, but it appears that there is a constant background of highly terrigenous material. There was a high degree of variability between sites and over the slope there was not enough data to asses the inter-annual variability. In Canada Basin, the inter-annual variability was closely linked to the extent of open water in the summer period. At all sites, lateral transport is clearly indicated by the increase in flux with depth. The data robustly demonstrate the need for detailed knowledge of physical processes for informed interpretation of particle fluxes and sediment transport in this area.