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Mercury cycling between the water column and surface sediments in a contaminated area

Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.87%
Mercury cycling in the water column and upper sediments of a contaminated area, the Largo do Laranjo, Aveiro (Portugal), was evaluated after determination of reactive and non-reactive mercury concentrations in the water column and pore waters of sediments, collected in several places of this bay. In the water column, reactive mercury concentrations varied between 10 and 37 pmol dm−3, the highest values being observed near the mercury anthropogenic source. However, reactive mercury was a narrowly constrained fraction of the total mercury, making up only 4–16% of the total, showing evidence of the importance of dissolved organic matter on mercury transport. In sediments, higher concentrations of mercury were also determined near industrial discharges. Results indicate the existence of an equilibrium between solid and liquid phases, determined by solid sediment/pore water distribution coefficients. Much of the mercury present in the solid fraction is associated with organic matter (r=0.837) and iron oxyhydroxides (r=0.919), but as oxides begin to dissolve in reduced sediments and organic matter decays, the adsorbed mercury is released. In fact, the mercury concentrations in pore waters of those contaminated sediments largely exceeded the values determined in the water column. As molecular diffusion may contribute to the dissolved mercury distribution in the overlying water column...

Meiobenthic communities of seagrass beds (Zostera capricorni) and unvegetated sediments along the coast of New South Wales, Australia

Fonseca, Gustavo Fernandes Camargo; Hutchings, Pat; Gallucci, Fabiane
Fonte: ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD Publicador: ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.97%
Seagrass beds have higher biomass, abundance, diversity and productivity of benthic organisms than unvegetated sediments. However, to date most studies have analysed only the macrofaunal component and ignored the abundant meiofauna present in seagrass meadows. This study was designed to test if meiobenthic communities, especially the free-living nematodes, differed between seagrass beds and unvegetated sediments. Sediment samples from beds of the eelgrass Zostera capricorni and nearby unvegetated sediments were collected in three estuaries along the coast of New South Wales, Australia. Results showed that sediments below the seagrass were finer, with a higher content of organic material and were less oxygenated than sediments without seagrass. Univariate measures of the fauna (i.e. abundance, diversity and taxa richness of total meiofauna and nematode assemblages) did not differ between vegetated and unvegetated sediments. However multivariate analysis of meiofaunal higher taxa showed significant differences between the two habitats, largely due to the presence and absence of certain taxa. Amphipods, tanaidacea, ostracods, hydrozoans and isopods occurred mainly in unvegetated sediments, while kinorhyncs, polychaetes, gastrotrichs and turbellarians were more abundant in vegetated sediments. Regarding the nematode assemblages...

A 2400-year record of trace metal loading in lake sediments of Lagoa Vermelha, southeastern Brazil

Oliveira, Sonia Maria Barros de; Ruiz Pessenda, Luiz Carlos; Teixeira Favaro, Deborah Ines; Babinski, Marly
Fonte: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD Publicador: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.87%
Sediments of the Lagoa Vermelha (Red Lake), situated in the Ribeira Valley, southeastern Brazil, are made of a homogeneous, organic-rich, black clay with no visible sedimentary structures. The inorganic geochemical record (Al, As, Ba, Br, Co,Cs, Cr, Fe, Mn, Ni, Rb, Sc, Sb, V, Zn, Hg and Pb) of the lake sediments was analyzed in a core spanning 2430 years. The largest temporal changes in trace metal contents occurred approximately within the last 180 years. Recent sediments were found to be enriched in Pb, Zn, Hg, Ni, Mn, Br and Sb (more than 2-fold increase with respect to the "natural background level"). The enhanced accumulation of Br, Sb, and Mn was attributed to biogeochemical processes and diagenesis. On the other hand, the anomalous concentrations of Pb, Zn, Hg and Ni were attributed to pollution. As Lagoa Vermelha is located in a relatively pristine area, far removed from direct contamination sources, the increased metal contents of surface sediments most likely resulted from atmospheric fallout. Stable Pb isotopes provided additional evidence for anthropogenic contamination. The shift of Pb-206/Pb-207 ratios toward decreasing values in the increasingly younger sediments is consistent with an increasing contribution of airborne anthropogenic lead. In the uppermost sediments (0-10 cm)...

Bases técnico - científicas para a derivação de valores-guias de qualidade de sedimentos para metais: experimentos de campo e laboratório ; Technical - scientific basis for the derivation of values-guides of quality of sediments for metals: field and laboratory experiments

Silverio, Patrícia Ferreira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 11/12/2003 PT
Relevância na Pesquisa
36.94%
Este trabalho fez parte de um projeto FAPESP (Projeto QualiSed), onde foram envolvidas três instituições paulistas (UFSCar, UNICAMP, CETESB) e que teve como intuito levantar dados para a futura derivação Valores – Guias de Qualidade de Sedimentos (VGQS) para metais e compostos orgânicos xenobióticos. O objetivo específico deste trabalho é o de gerar dados para a derivação de VGQS para metais (Cd, Cu, Pb, Ni e Zn) em cinco represas do Rio Tietê, represas Billings, Rasgão, Barra Bonita, Bariri e Promissão. Os estudos foram direcionados à caracterização biogeoquímica dos sedimentos desses ambientes através das determinações das concentrações dos nutrientes totais e sulfetos volatilizáveis por acidificação (SVA), do estudo da partição de metais entre os sedimentos totais as águas intersticiais, e da determinação da fração de metais associada aos SVA nos sedimentos totais, denominada metais estraidos simultameamente ou MES. Os dados levantados foram interpretados em associação aos resultados da estrutura da comunidade bentônica e testes de toxicidade. Foi realizada também, uma avaliação e identificação da toxicidade (AIT) (do inglês, TIE: Toxicity Identification Evaluation) com sedimentos da Represa de Rasgão. Este procedimento se baseia na toxicidade causada após um esquema de fracionamento e manipulações químicas da matriz para caracterizar (Fase I)...

O papel dos sedimentos em suspensão no metabolismo de rios de micro e meso-escala no estado de Rondônia.; The role of suspended sediments in the metabolism of micro and meso scale rivers of Rondonia, Brasil.

Cogo, Michelle Cristine
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/05/2005 PT
Relevância na Pesquisa
36.94%
As águas superficiais da Amazônia, que englobam, dentre outros, rios das mais variadas ordens, desde pequenos igarapés, até o rio Amazonas, um dos maiores do mundo, são um componente importante do funcionamento deste ecossistema de escala continental. Um paradigma acerca dos sistemas fluviais é que estes integram os processos que ocorrem em suas bacias de drenagem e, portanto, alterações na cobertura vegetal e nos usos da terra, podem interferir diretamente nos parâmetros físicos e químicos dos compartimentos aquáticos. Algumas áreas da Amazônia, como o estado de Rondônia, por exemplo, têm sofrido alterações substanciais nas suas bacias de drenagem e as conseqüências destas nos sistemas fluviais ainda são pouco compreendidas. Sabe-se que a conversão de florestas em pastagens, o tipo de alteração mais comum nos ecossistema de Rondônia, resulta na compactação dos solos e no aumento da erosão. Ao mesmo tempo, diversos estudos têm demonstrado que os sedimentos em suspensão, carreados nos rios, podem ser importantes fontes de carbono e outros nutrientes limitantes para o metabolismo aquático. Com base nestas premissas, este estudo visou avaliar a importância dos sedimentos em suspensão grossos (maiores que 63 µm) e finos (menores que 63 µm e maiores 0...

Contribuição dos sulfetos volatilizados por acidificação no controle da biodisponibilidade de metais em sedimentos do rio Morrão, sistema estuarino de Santos-Cubatão (SP); Contribution of the acid volatile sulfide in the control of metal bioavailability in sediments of the Morrão river, estuary system of Santos-Cubatão (SP)

Erico Casare Nizoli
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/05/2007 PT
Relevância na Pesquisa
36.9%
Os estuários são geralmente ambientes redutores, nos quais atividades antrópicas podem resultar em altos níveis de metais nos sedimentos. Nestes sedimentos o sulfeto é uma fase importante no controle da concentração de metais livres, sendo que a maioria dos sulfetos reativos em sedimentos ocorre como bisulfetos e monosulfetos de ferro, sendo estes últimos os mais reativos. Devido à maior insolubilidade dos sulfetos, elementos como Cd, Cu, Ni, Pb e Zn deslocam o Fé do FeS para formar seus respectivos sulfetos, mais estáveis. A razão entre SVA (sulfetos volatilizados por acidificação) e MSE (metais simultaneamente extraídos, extraídos a frio com uma solução diluída de HCl) é freqüentemente utilizada como um indicador do potencial de biodisponibilidade dos referidos metais em sedimento de ambientes anaeróbicos. Quando a concentração molar de SVA excede a concentração dos MSE, a biodisponibilidade não é considerada significativa. O sistema estuarino de Santos-Cubatão tem sido considerado um ambiente sedimentar seriamente poluído, devido à emissão não controlada de efluentes industriais e urbanos. Neste sistema, os sedimentos do rio Morrão contêm expressiva contaminação multi-elementar. Com o objetivo de quantificar a contaminação de metais e verificar o papel do SVA no controle de biodisponibilidade dos MSE no rio Morrão...

Sazonalidade geoquímica multi-elementar em diferentes frações granulométricas de sedimentos do sistema estuariano de Santos - Cubatão/SP; Multi-elemental geochemical seasonality in different granulometric fractions of sediments at the estuary system of Santos - Cubatão / SP

Ludimila Berno
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 31/08/2010 PT
Relevância na Pesquisa
36.9%
O sistema estuarino de Santos-Cubatão (SP) está localizado em uma das áreas mais industrializadas da América Latina. Os estuários são ambientes de grande complexidade, onde ocorrem interrelações entre componentes geológicos, físicos, biológicos e químicos. O histórico de contaminação desse ambiente estuarino, decorrente de diferentes atividades antrópicas, pode resultar em altos níveis de contaminação, e os sedimentos podem representar uma fonte latente de elementos-traço para o ambiente aquático. Com o objetivo de investigar a variabilidade geoquímica sazonal de elementos-traço, os sedimentos de superfície dos principais rios deste sistema estuarino (Casqueiro, Cubatão, Cascalho, Morrão e Capivari) foram amostrados no inverno e no verão. Concentrações químicas multi-elementares em diferentes granulometrias (<63 mm, <177 mm e total), obtidas por ICP-MS, e os níveis de matéria orgânica foram relacionados. As texturas dos sedimentos estudados apresentaram característica silto-argilosa (64 a 87%). Os maiores níveis de matéria orgânica foram encontrados nos sedimentos do rio Morrão (10,92 a 12,05%), porém não foi observada relação com a granulometria. Em geral, os metais e metalóides foram mais concentrados na textura silto-argilosa...

Assessment of mercury in sediments and in the benthic invertebrate micronecta scholtzi downstream an abandoned pyrite mine

Agra, AR; Abreu, SN; Barata, C; Soares, AMVM
Fonte: Parlar Scientific Publications Publicador: Parlar Scientific Publications
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.87%
The drainage of abandoned mines leads to several ecological problems, particularly the acidification of surface freshwater systems and heavy metal contamination. Mercury (Hg) is of particular interest because of its high toxicity and its ability for bioaccumulation. This work evaluates the magnitude and pattern of Hg dissipation from an abandoned pyrite mines to the local water ecosystem by testing of the stream bottom sediments and water invertebrate Micronecta scholtzi along the pyrite-cupric mine drainage system. Overall results showed a high significant correlation (Pearson coefficient = 0.82 at p<0.05) between mercury levels in biota and those in sediments for all the sampling sites. In the sediments Hg concentrations ranged from 14.4-32.4 mu g g(-1) dw decreasing downstream to 3.67-5.3 mu g g(-1) due to natural dilution. He, concentration in M. scholtzi showed a similar trend ranging from 3.6-12.6 mu g g(-1) dw at the mine pit and decreasing 5 Km downstream to 0.2-1.6 mu g g(-1) thus reflecting the significant Hg dissipation in surface sediments. Reported Hg levels in sediments were very high and significantly above threshold limits defined by the legislation for the protection of aquatic biota. The Hg in stream sediments derived from such mining areas is potentially hazardous to the environment adjacent to the abandoned mine and this work proves that Hg is mobilised from the mines and accumulated by local water biota...

Speciation of rare earth elements in surface sediments of Lagoon of Aveiro (N Portugal)

Martins, V.; Dias, J. A; Laut, L. M.; Sobrinho, F.; Santos, J. F.; Rodrigues, M. A.; Frontalini, F.; Miranda, P.; Terroso, D.; Fernández-Fernández, S.; Ferreira, B.; Bernardes, C.; Figueira, R.; Sousa, S.; Amaral, P.; Mahiques, M.; Bernabeu, A.; Rey, D.
Fonte: Coastal Education & Research Foundation (CERF) Publicador: Coastal Education & Research Foundation (CERF)
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.9%
Ria de Aveiro (N Portugal), a coastal lagoon connected with the Atlantic through an artificial inlet, receives the input from several rivers and streams that flow into inland areas eroding rocks of the Variscan basement. The goal of this work is to know the distribution of the rare earth elements in the surface sediments. Concentrations of REE (La, Ce, Nd, Sm) and related elements (Th, Y and Sc) were evaluated by total digestion of sediments in the fine fraction of 33 grab-samples of surface sediments. The same method was followed for Al, Ca, S and Zr, related to terrigenous sources, but also, in the cases of Ca and S, to biogenic and quimiogenic processes. Concentrations of REE and related elements were additionally assessed by a three-step sequential chemical extraction (E1-3) procedure coupled with ICP–MS determination. The geochemical results were processed by statistical analysis combining textural and mineralogical data (XRD techniques). The results show that mobile La, Ce, Nd, Sm and Y are mostly adsorbed by amorphous Mn hydroxide (E3), secondly associate with organic matter (E2) and only in a very small extent are adsorbed on clay mineral structural sheets or associated with carbonates (E1). Thorium and Sc are almost exclusively linked with E2. Ytrium shows a very high percentage of availability...

Erosion and accretion in the Ria de Aveiro inlet (N Portugal) and exportation of fine-grained sediments to the shelf; Erosión y acumulación en la entrada de la Ría de Aveiro (N Portugal) y la exportación de sedimentos de grano fino a la plataforma

Martins, V.; Grangeia, C.; Jesus, C. C.; Martins, P.; Laut, L. M.; Sequeira, C.; Dias, J. M.; Silva, P. A.; Abrantes, I.; Silva, E. Ferreira da; Rocha, F.
Fonte: Universidad Complutense de Madrid Publicador: Universidad Complutense de Madrid
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.9%
Harbours are important man made economic structures that are usually constructed in hydrodynamic complex settings. Their life/service cycle, integrity and maintenance are highly dependent on the knowledge of these settings and the capability to predict future changes and thus their economic impact. In this paper, data regarding bottom and suspended sediments of the Aveiro Harbour inlet were gathered and analysed. Measurements of suspended sediment concentrations (SSC) in the Aveiro inlet were taken during eight tidal cycles in 2007, including spring and neap tides throughout winter and summer oceanographic regimes. Results suggest significant temporal variability. Sediments were imported from the ocean sink, mostly near the south jetty and the western side of the Mira Channel, as textural, mineralogical, compositional, geochemical and microfaunal data of bottom sediments suggest. Higher stabilization of the Aveiro Harbour structures is achieved on these accretional areas. The high tidal-current velocities contribute to the erosive character which dominates the central area of the entrance channel, which is located between both breakwaters and close to the north jetty; thus some segments of the north jetty could become damaged through erosion. This is evidenced as much bottom sediments characteristics as patterns of SSC. SSC are in general higher during the winter...

Mercury cycling between the water column and surface sediments in a contaminated area

Ramalhosa, E.; Segade, S. R.; Pereira, E.; Vale, C.; Duarte, A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.87%
Mercury cycling in the water column and upper sediments of a contaminated area, the Largo do Laranjo, Aveiro (Portugal), was evaluated after determination of reactive and non-reactive mercury concentrations in the water column and pore waters of sediments, collected in several places of this bay. In the water column, reactive mercury concentrations varied between 10 and 37 pmol dm−3, the highest values being observed near the mercury anthropogenic source. However, reactive mercury was a narrowly constrained fraction of the total mercury, making up only 4–16% of the total, showing evidence of the importance of dissolved organic matter on mercury transport. In sediments, higher concentrations of mercury were also determined near industrial discharges. Results indicate the existence of an equilibrium between solid and liquid phases, determined by solid sediment/pore water distribution coefficients. Much of the mercury present in the solid fraction is associated with organic matter (r=0.837) and iron oxyhydroxides (r=0.919), but as oxides begin to dissolve in reduced sediments and organic matter decays, the adsorbed mercury is released. In fact, the mercury concentrations in pore waters of those contaminated sediments largely exceeded the values determined in the water column. As molecular diffusion may contribute to the dissolved mercury distribution in the overlying water column...

Stonemeal of amazon soils with sediments from reservoirs: a case study of remineralization of the tucuruí degraded land for agroforest reclamation

THEODORO,SUZI H.; LEONARDOS,OTHON H.; ROCHA,EDUARDO; MACEDO,IRIS; REGO,KLEYSSON G.
Fonte: Academia Brasileira de Ciências Publicador: Academia Brasileira de Ciências
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2013 EN
Relevância na Pesquisa
36.87%
This study suggests the employment of accumulated sediments in the reservoir of Tucuruí (Pará /Brazil) to remineralize the surrounding degraded soils. The approach was based on the principles of stonemeal technology. It suggests that the soil can be rejuvenated by crushed rocks rich in macro and micronutrients. Removal of the sediments for agricultural use will bring benefits to family farmers and increase the life cycle of the reservoir and, therefore, energy generation. Geochemical data on retained sediments, soils and rocks in the area of influence of the reservoir were evaluated regarding nutrient transport mechanisms and soil-fertility potential. Results show that sediments from the reservoir contain nutrients levels at least one order of magnitude greater than average Amazon region soils. Our data on soil use and occupation in the region show the degradation areas which could be recovered by stonemeal techniques. Thence, an Agroforestry System was installed, with 12 plots where different mixtures of sediments removed from the reservoir were used, along with crushed rock with or without the addition of NPK and manure. The experiments showed that maximum crop yield and plant growth were attained in the plots where a mixture of sediments...

Urban activity and mercury contamination in estuarine and marine sediments (Southern Brazil)

Mirlean, Nicolai; Calliari, Lauro Julio; Baisch, Paulo Roberto Martins; Loitzenbauer, Ester; Shumilin, Evgueni
Fonte: Universidade Federal do Rio Grande Publicador: Universidade Federal do Rio Grande
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.87%
The distribution of mercury in sediments of the Patos Lagoon estuary and nearby coastal marine deposits has been investigated for the period 1998???2008. Polluted urban soils and coastal reclamation fills are the principal sources of high mercury concentrations for shallow estuarine sediments. The shallow sediments that form near the urban area enter the navigation canal and are transported into the ocean. The mercury concentration in sediments of the navigation canal has considerably increased since 2004, due to intense reconstruction activity in the urban area. Periodic dredging of the canal strengthens the preconditions for coastal marine sediment contamination by mercury. However, this does not occur because the resuspended dredged sediments are significantly diluted by natural suspended particulate matter.

DNA strand breaks in grass shrimp embryos exposed to highway runoff sediments and sediments with coal fly ash

Lee, Richard; Niencheski, Luis Felipe Hax; Brinkley, Karrie
Fonte: Universidade Federal do Rio Grande Publicador: Universidade Federal do Rio Grande
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.87%
Embryo production was reduced in female grass shrimp exposed to sediments with added coal fly ash and to sediments collected from an estuarine station containing high PAH concentrations due to its proximity to a highway storm drain. Grass shrimp embryos exposed to pore water from the high PAH and high metal sediments showed both reduced hatching and increases in DNA strand breaks (comet assay). Sediments with added coal fly ash had high concentrations of vanadium and selenium which may have contributed to effects similar to those observed with sediments with high PAH. The embryo pore water bioassay (hatching/DNA strand breaks) gave results comparable to those observed for reproduction effects (reduced embryo production/embryo hatching) with female grass shrimp exposed to whole sediment.

Textual characteristics of coarse sediments in selected streams of the Niagara Peninsula, Ontario

Fisher, James Edward.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
ENG
Relevância na Pesquisa
36.87%
The streams flowing through the Niagara Escarpment are paved by coarse carbonate and sandstone sediments which have originated from the escarpment units and can be traced downstream from their source. Fifty-nine sediment samples were taken from five streams, over distances of 3,000 to 10,000 feet (915 to 3050 m), to determine downstream changes in sediment composition, textural characteristics and sorting. In addition, fluorometric velocity measurements were used in conjunction with measured -discharge and flow records to estimate the frequency of sediment movement. The frequency of sediments of a given lithology changes downstream in direct response to the outcrop position of the formations in the channels. Clasts derived from a single stratigraphic unit usually reach a maximum frequency within the first 1,000 feet (305 m) of transport. Sediments derived from formations at the top of waterfalls reach a modal frequency farther downstream than material originating at the base of waterfalls. Downstream variations in sediment size over the lengths of the study reaches reflect the changes in channel morphology and lithologic composition of the sediment samples. Linear regression analyses indicate that there is a decrease in the axial lengths between the intial and final samples and that the long axis decreases in length more rapidly than the intermediate...

An investigation of geological and geochemical characteristics of late-Quaternay sediments in the Georgian Bay Region, Southern Ontario

Chen, Chang-Sen.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
ENG
Relevância na Pesquisa
36.9%
Core samples of postglacial sediments and sediment surface samples from Shepherd Lake on the Bruce Peninsula, Harts Lake on the Canadian Shield, and two cores from Georgian Bay (core P-l in the western deep part and core P-7 in the eastern shallow part) have been analyzed for pH, grain size distribution, water content, bulk density, loss on ignition at 4500C and 11000 C, major oxides (Si02 ,A1203,!FeO,MgO,CaO, Na20,K20,Ti02 ,MnO and P205) and trace elements (Ba,Zr,Sr,y,S, Zn,Cu,Ni,Ce and Rb). The sediment in Georgian Bay are generally fine grained (fine silt to very fine silty clay) and the grain size decreases from the Canadian Shield (core p-7) towards the Bruce Peninsula (core P-l) along the assumed direction of sediment transport. This trend coincides with a decrease in sorting coefficient and an increase in roundness. Other physical characteristics, such as water content, bulk density and loss on ignition are positively correlated with the composition of sediments and their compaction, as well as with the energy of the depositional environment. Analyses of sediment surface samples from Shepherd Lake and Harts Lake indicate the influence of bedrock and surficial deposits in the watershed on pH condition that is also influenced by the organic matter content and probably I ! I man's activities. Organic matter content increases significantly in the surface sediment in these small lakes as a result of either natural eutrophication or anthropogenic organic loading. The extremely high organic matter content in Shepherd Lake sediment indicates rapid natural eutrophication in this closed basin and high biological productivity during postglacial time...

Concentrations et flux d'azote dans les sédiments hypoxiques de l'Estuaire Maritime du St-Laurent.

Kowarzyk, Jacqueline
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
36.94%
Les sédiments sont des sites importants d’élimination d’azote (N) puisqu’ils possèdent des gradients d’oxydoréduction leur conférant les conditions idéales pour les réactions microbiennes de transformation de N. L’eutrophisation des régions côtières peut altérer ces gradients, par des changements dans la concentration d’oxygène (O2) de l’eau interstitielle, et modifier l’importance relative des processus transformant le N. Afin de mieux comprendre comment l’O2 pourrait influencer les transformations de N, nous avons mesuré les flux diffusifs de diazote (N2), nitrate (NO3-), oxygène et ammonium (NH4+) dans les sédiments de l’Estuaire Maritime du St-Laurent (EMSL), et nous avons estimé les taux de dénitrification. L’importance du couple nitrification-dénitrification en fonction d’un gradient de concentrations d’O2 dans la zone d’hypoxie de l’EMSL fut aussi évaluée. La concentration des gaz dissous fut mesurée en utilisant une nouvelle approche développée dans cette étude. Les flux diffusifs de N2, O2, NO3- et NH4+ variaient de 5.5 à 8.8, de -37.1 à -84.8, de -4.0 à -5.8 et de 0.6 à 0.8 μmol N m-2 h-1 respectivement. Les concentrations de N2 et NO3- dans l’eau porale et les flux de NO3- et de N2 des sédiments...

Numerical modelling of cohesive sediments transport in the Ria de Aveiro lagoon, Portugal

Lopes, J. F.; Dias, J. M.; Dekeyser, I.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.9%
The main goal of this work is to implement a cohesive sediments transport model for the Ria de Aveiro and study the dynamics of the suspended cohesive sediments of the lagoon. It is carried out in the scope of the project Eicos, which main objective is to study the interaction between fine cohesive sediments and chemical and biological contaminations of the lagoon waters. Ria de Aveiro is a very shallow and well-mixed lagoon dominated by tidal currents. It presents a complex network structure composed by several sub-systems, dominated by tidal asymmetries, resulting in areas of ebb and flood dominance and weak gravitational circulation. Tidal currents are the main forcing in the transport of suspended sediments of the lagoon. The effects of the Vouga river input on the suspended concentration in the lagoon are enhanced during the spring tides and high rivers runoff. Wind stress enhances the bottom erosion and the advection of sediments when the induced residual current is in phase with the tidal current but may contribute to a decrease of sediments concentration in the case of phase opposition as can occur in the S. Jacinto channel. The S. Jacinto and the Espinheiro channels as well as C. Bico, are the most important areas of the lagoon...

Petrologia i diagènesi en sediments de l'Oligocè superior i del Miocè inferior i mitjà de la depressió del Vallès i del Pla de Barcelona evolució de l'àrea font i dinàmica dels fluids /

Parcerisa i Duocastella, David
Fonte: Bellaterra : Universitat Autònoma de Barcelona, Publicador: Bellaterra : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis Formato: application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf;
Publicado em //2003 CAT; CAT
Relevância na Pesquisa
37.03%
Consultable des del TDX; Títol obtingut de la portada digitalitzada; En aquesta tesi s'han estudiat sediments d'edat entre l'Oligocè superior i el Miocè mitjà que estan en relació amb la formació de les Serralades Costaneres Catalanes (SCC). Els sediments d'edat oligocena (Catià de Montgat) es van formar en un context compressiu, quan les SCC encavalcaven vers la Conca de l'Ebre, probablement com a part integrant d'una conca de tipus piggy back. Els sediments d'edat miocè inferior i mig es van formar en un context distensiu, reomplint dues de les conques de tipus semigraben que provocaren el col·lapsament de gran part de les SCC i la formació del Solc de València. Concretament, els sediments més basals del Miocè inferior (Aquitanià? i Burdigalià inferior del Vallès) pertanyen a l'etapa de syn-rift miocena i la resta de sediments del Miocè inferior i mitjà (Burdigalià superior-Languià del Vallès i Languià?-Serraval·lià de Montjuïc) pertanyen a l'etapa de post-rift. Després de l'estudi detallat dels materials del Catià de Montgat, del Burdigalià del Vallès i del Serraval·lià de Montjuïc, es poden identificar tres etapes en l'evolució de l'àrea font, les quals es poden relacionar amb l'evolució tectono-sedimentària d'aquesta zona i...

Spatial distribution of heavy metals in sediments from the Gulf of Paria,Trinidad

Norville,Wendy
Fonte: Revista de Biología Tropical Publicador: Revista de Biología Tropical
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2005 EN
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The Gulf of Paria receives heavy metal input from urban runoff,industrial and agricultural activity, sewage and domestic wastes:both from the west coast and from inland areas of Trinidad.Non-residual concentrations of nine metals,as well as total mercury concentrations,were used to determine spatial distributions of heavy metals in sediments in the Gulf of Paria.Surficial sediment samples were collected at 37 stations,which included the mouths of 11 major rivers that flow into the Gulf of Paria.Stations were sampled twice during the wet season (July 1998 and November/December 1998)and twice during the dry season (March 1999 and April 1999).Sediments were analyzed for aluminium (Al),cadmium (Cd),chromium (Cr),copper (Cu),iron (Fe), lead (Pb),manganese (Mn),nickel (Ni),zinc (Zn)and mercury (Hg).Total Organic Carbon (TOC)and grain size analyses were also performed on the sediments.Principal component analysis showed that sediments from river mouths subject to greatest land use and anthropogenic input,were distinct from other sediments in the Gulf of Paria.This was due to higher Pb,Zn,Cu and Hg concentrations (3.53-73.30 µg g-1 ,45.8-313.9 µg g-1 ,8.43-39.71 µg g-1 and 0.03-0.10 µg g-1 ,respectively).Sediments further from the coast were also distinct due to their higher Al...