Siga este enlace para ver otros tipos de publicaciones sobre el tema: Sediments.
Artículos de revistas sobre el tema "Sediments"
Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros
Consulte los 50 mejores artículos de revistas para su investigación sobre el tema "Sediments".
Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.
También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.
Explore artículos de revistas sobre una amplia variedad de disciplinas y organice su bibliografía correctamente.
1
Ooi, Jieun Lin, Lee Woen Ean, Bashar S. Mohammed, M. A. Malek, Leong Sing Wong, Chao Wei Tang y He Qing Chua. "Study on the Properties of Compressed Bricks Using Cameron Highlands Reservoir Sediment as Primary Material". Applied Mechanics and Materials 710 (enero de 2015): 25–29. http://dx.doi.org/10.4028/www.scientific.net/amm.710.25.
Texto completoResumen
This research is to investigate the properties of compressed building bricks producedfrom Cameron Highlands reservoir sediment. The particle size distribution of the sediments are graded as silt and sand. The sediments used were as total replacement of the normal soils used in the compressed soil bricks. This paper presents the compilation of experimental brick properties; compressive strength, water absorption, microstructure and heavy metal leachingof the compressed sediment bricks. The experimental results shows that increasing use of reservoir sediments decrease the compressive strength andincrease the water absorption. The heavy metal concentrations of the leachates from the leaching test are all within the regulatory limits. The optimum mix is derives from the compressive strength and the water absorption in which in this research is Mix 4, 70% sedimenta, 20% sedimentb and 10% cement,complying with ASTM C129 – Non Load Bearing Bricks [1].
2
Rosa, Kátia Kellem da, Rosemary Vieira y Jefferson Cardia Simões. "Identificação de Mudanças Ambientais Através da Caracterização Sedimentar e Investigação de Processos Glaciogênicos e Paraglaciais no Ambiente Glacial da Geleira Wanda, Ilha Rei George, Antártica (Identification of Environmental Change Through...)". Revista Brasileira de Geografia Física 6, n.º 1 (17 de julio de 2013): 029. http://dx.doi.org/10.26848/rbgf.v6i1.232807.
Texto completoResumen
Este estudo objetiva identificar as características sedimentares associadas aos depósitos glaciogênicos e sedimentos com modificação por processos não glaciais na área proglacial da geleira Wanda, Ilha Rei George, Antártica. A metodologia foi desenvolvida através de atividades de campo realizadas durante a estação de verão em 2007, 2010 e 2011. Os sedimentos foram analisados para determinar a distribuição granulométrica e características morfoscópicas. Este estudo apresenta resultados de interpretações dos sedimentos coletados na proglacial da geleira Wanda. A análise sedimentar possibilita a distinção de sedimentos glaciogênicos e dos sedimentos modificados por atividade paraglacial, podendo evidenciar mudanças ambientais em decorrência do aumento da temperatura atmosférica superficial e da precipitação líquida. AbstractThis study arms identify sediment characteristics related to glaciogenics deposits and modification with paraglacial processes in Wanda Glacier proglacial area, King George Island, Antarctica. The methodology was developed through field activities performed during summers in 2007, 2010 and 2011. The sediments were analyzed to determine the particle size distribution and morphoscopical characteristics. This study presents results of the samples sediment interpretation in Wanda Glacier proglacial area. The sediment analyses provided the discrimination of the glaciogenicssediments and paraglacial modified sediments, and was evidence for environment changes in the study area due to the increase surface atmospheric temperature and liquid precipitation.
3
Trenggono, Mukti, Roy Andreas, Amron Amron, Rizqi Rizaldi Hidayat, Hendrayana Hendrayana, Rr Diah Febri Astuti y Cristiana Manullang. "An Assessment of Cilacap Coast's Total Carbonate Sediment Content". Jurnal Kelautan Tropis 24, n.º 1 (12 de diciembre de 2020): 15–24. http://dx.doi.org/10.14710/jkt.v24i1.8849.
Texto completoResumen
Sediments are particles derived from the dismantling of rocks from the land and pieces of shell and remains of marine organisms that contain organic matter, included carbonate sediment. The total carbonate sediment content was influenced by many factors, such as sediment grain type. This study aimed to determine the carbonate content in sediments and to determine their relationship to the sediment grain characteristic on the Cilacap coast. The sediment's carbonate content used the titration method, while the sediment grain test used a dry filter. Statistical analysis was used to determine the sediment grain characteristic (mean, sorting, skewness, and kurtosis). The results showed that sediments' total carbonate content had a range of 1.93% - 6.23%, with an average of 4.21%. Sediments are dominated by fine sand with very well sorted, very platykurtic, and very fine skewed characteristics. The relationship between sediment grain characteristics and total sediment carbonate content showed a good correlation due to the sorting factor. Other parameters such as mean size and skewness have been shown a low correlation, whereas kurtosis has a shallow relationship with carbonate content.
4
Marinho, Rogério Ribeiro, Antonio Fábio Sabbá Guimarães Vieira y Feliciano De Souza Maciel. "Análise Montante-Jusante da Granulometria dos Sedimentos de Fundo e Suspenso do Rio Negro e Tributários (Bacia Amazônica, Brasil)". Revista Brasileira de Geografia Física 14, n.º 2 (14 de abril de 2021): 997. http://dx.doi.org/10.26848/rbgf.v14.2.p997-1008.
Texto completoResumen
O conhecimento das características físicas de sedimentos transportados por grandes sistemas fluviais possui significativa importância para o entendimento de processos geomorfológicos e hidrológicos. O nível de conhecimento dos grandes sistemas fluviais da Amazônia e sua relação com o transporte de sedimentos ainda é limitado, resultando em lacunas de conhecimento sobre a dinâmica da paisagem nesta complexa região. Este trabalho teve como objetivo avaliar a distribuição espacial da granulometria de sedimentos de fundo e suspenso do Rio Negro e tributários. Realizou-se análise da distribuição do tamanho dos sedimentos em seções amostrais localizadas no alto, médio e baixo curso do Rio Negro. Os resultados da análise granulométrica da carga de fundo indicam a predominância de sedimentos com tamanho variando de 0,25 a 1,0 mm (principalmente areia fina, areia média e areia grossa) enquanto no baixo curso as amostram oscilaram de areia fina a partículas lamosas (< 0,50 mm). No Rio Negro os sedimentos suspensos são compostos principalmente de partículas finas de silte (90% menor que 80 µm) com diâmetro mediano (D50) de 25 µm. As características granulométricas apresentadas neste trabalho fornecem subsídios para o entendimento de processos hidrodinâmicos de transporte e deposição dos sedimentos de fundo e suspenso neste gigante sistema fluvial. Upstream-downstream Granulometry Analysis of bed and suspended sediments in the Negro River Basin (Amazon Basin, Brazil)A B S T R A C TThe knowledge of the physical characteristics of sediments transported by large river systems has significant importance for the understanding of geomorphological and hydrological processes. The level of knowledge of the large rivers of the Amazon basin and their relationship with sediment transport is limited, resulting in gaps about the dynamics of the landscape in this complex region. This article analyzes the spatial distribution of granulometry of bed and suspended sediments in the Negro River and tributaries. An analysis of the sediment size distribution was carried out in sample sections located in the upper, middle and lower reaches of the Negro River. The results of the granulometric analysis of the bed load indicate the predominance of sediments with sizes ranging from 0.25 to 1.0 mm (mainly fine sand, medium sand and coarse sand) while in the low course they showed oscillated from fine sand to muddy particles (<0.50 mm). In the Negro River basin the suspended sediments are composed mainly of fine silt particles (90% less than 80 µm) with a median diameter (D50) of 25 µm. The granulometric characteristics presented in this work provide subsidies for the understanding of hydrodynamic processes of transport and deposition of bed and suspended sediments in this huge fluvial system.Keywords: sediment transport, Amazon floodplain, multichannel river, anabranching
5
Laut, Lazaro, Maria Virgina Alves Martins, Pierre Belart, Maria Lucia Lorini, Iara Clemente, Leandro Nogueira, Anna Juliace y Luiz Francisco Fontana. "ORGANIC COMPOUNDS AS PROXIES OF THE SEDIMENTARY ENVIRONMENTAL QUALITY OF THE MARICÁ-GUARAPINA LAGOON SYSTEM (SE, BRAZIL)". Journal of Sedimentary Environments 4, n.º 2 (15 de junio de 2019): 159–73. http://dx.doi.org/10.12957/jse.2019.43371.
Texto completoResumen
Bottom sediment is a natural trap for organic matter and different kinds of pollutants. The accumulation of large amount of organic matter gives rise to the eutrophication of the aquatic ecosystems. The analyses of the quantity and quality of the organic matter (biopolymers) help to determine the trophic status of coastal ecosystems. The Maricá-Guarapina Lagoon System (MGLS) is located in Rio de Janeiro and is composed by four connected lagoons: Maricá, Barra, Padre and Guarapina. It has been suffering impacts due to the intense and uncontrolled property speculation. Based on this problem, this study aimed to characterize the organic matter (OM) amount and quality in sediments and the relation with the impacted areas in this lagoon system. The collected sediment samples were analyzed for geochemical data combined with grain size and physical-chemical environmental parameters of the bottom water. Statistical results evidenced that the sedimentary environment of the MGLS is heterogenous. The organic matter supplied to the MGLS is provided from different sources but the autochthonous contribution (phytoplanktonic productivity and vegetal detritus from the mangrove fringe) prevails. The anthropogenic contribution was more evident in Padre Lagoon, where the sediments had relatively low TOC contents (0.1-0.8%). The MGLS is accumulating mainly aged organic matter. The most impacted zones were found in Guarapina, Barra and Maricá lagoons, in bottoms of fine-grained sediments, with relatively high TOC and labile biopolymeric compounds (proteins, carbohydrates and lipids) contents, which should evolve into an ever-increasing stage of eutrophication. COMPOSTOS ORGÂNICOS USADOS COMO INDICADORES DA QUALIDADE AMBIENTAL SEDIMENTAR DO SISTEMA LAGUNAR MARICÁ-GUARAPINA (SE DO BRASIL)ResumoO sedimento de fundo constitui uma armadilha natural para a matéria orgânica e diferentes tipos de poluentes. O acúmulo de grande quantidade de matéria orgânica dá origem à eutrofização dos ecossistemas aquáticos. Estimativas de quantidade e qualidade da matéria orgânica (biopolímeros) podem ajudar a determinar o estado trófico dos ecossistemas costeiros. O Sistema Lagunar de Maricá-Guarapina (MGLS), localizado no Estado do Rio de Janeiro (SE do Brasil), é composto por quatro lagunas interconectadas: Maricá, Barra, Padre e Guarapina. Este sistema tem sofrido impactos devido à intensa e descontrolada especulação imobiliária. Neste contexto, este estudo teve como objetivo caracterizar a quantidade e qualidade de matéria orgânica (MO) dos sedimentos do MGLS. Foram obtidos dados geoquímicos e confrontados com resultados granulométricos em amostras de sedimentos coletados em 22 estações de amostragem e analisados parâmetros físico-químicos da água. Os resultados estatísticos evidenciaram que o ambiente sedimentar do MGLS é heterogêneo. Este sistema recebe matéria orgânica de diferentes fontes, sendo, porém, prevalecente a contribuição autóctone (produtividade fitoplanctônica e detritos vegetais dos manguezais existentes na região). A contribuição antropogênica de matéria orgânica foi mais evidente na Lagoa do Padre, onde os sedimentos apresentaram teores de COT relativamente baixos (0,1-0,8%). As zonas mais impactadas foram encontradas em fundos de sedimentos finos, com teores relativamente elevados de COT e de compostos biopoliméricos lábeis (proteínas, carboidratos e lipídios), nas lagunas de Guarapina, Barra e Maricá. Os resultados obtidos revelam também que o MGLS está acumulando principalmente matéria orgânica envelhecida e permitem prever que as referidas áreas podem evoluir para um estágio de cada vez maior grau de eutrofização.Palavras-chave: Lagunas Costeiras Tropicais. Biopolímeros. Eutrofização. Dinâmica Sedimentar.
6
Pinto, Anita Fernandes Souza, José Carlos Martins Ramalho, Leonardo Borghi, Thiago Gonçalves Carelli, Josiane Branco Plantz, Egberto Pereira, Denise Terroso et al. "BACKGROUND CONCENTRATIONS OF CHEMICAL ELEMENTS IN SEPETIBA BAY (SE BRAZIL)". Journal of Sedimentary Environments 4, n.º 1 (25 de marzo de 2019): 108–23. http://dx.doi.org/10.12957/jse.2019.40992.
Texto completoResumen
This study intends to evaluate baseline concentrations of chemical elements for unpolluted sediments of Sepetiba Bay (SE Brazil). It analyzes the concentrations of potentially toxic elements (PTE) and other chemical elements (by Inductively Coupled Plasma Mass Spectrometry and Inductively Coupled Plasma Emission Spectrometry) from the upper part of the SP2 drillcore (or 2-SPT-1-RJ; with 50.30 m length), collected on the margins of Sepetiba Bay (at latitude 22° 55'S and longitude 43° 46'W). This core was described and sampled. Textural, mineralogical and geochemical analyses were performed in 17 sediment levels. The sediment layers of interest were selected, considering the period in which they were deposited, before high anthropic influence in the area, and on sediment grain-size. Only the muddy levels were selected, since fine sediments generally tend to have higher elemental concentrations. Foraminiferal occurrence was also analyzed in the selected layers. The results indicate that the studied sediments were deposited in a transitional marine context, after being exposed to multiple sedimentary cycles and weathering. The baseline concentrations, related to natural sediment sources were estimated for As, Cd, Co, Cr, Cu, Ni, Pb, Zn) and P and for other chemical elements. These results are useful in environmental impact assessment not only in the study area, but also for other coastal regions of Rio de Janeiro State. TÍTULO: CONCENTRAÇÕES DE FUNDO DE ELEMENTOS QUÍMICOS NA BAÍA DE SEPETIBA (SE BRASIL) RESUMO:Este estudo pretende avaliar as concentrações de fundo de elementos químicos, em sedimentos não poluídos, na Baía de Sepetiba (Se Brasil). Analisa as concentrações de elementos potencialmente tóxicos (PTE) e outros elementos químicos (por Espectrometria de Massa Plasma Acoplada Indutivamente e Espectrometria de Emissão Plasma Acoplada Indutivamente) da parte superior do testemunho SP2 (ou 2-SPT-1 RJ; com 50,30 m de comprimento), coletado nas margens da Baía de Sepetiba (à latitude 22° 55'S e longitude 43° 46'W). Este testemunho foi descrito e amostrado a cada 5 cm. Análises estruturais, mineralógicas e geoquímicas foram realizadas em 17 níveis de sedimentos. Os níveis de interesse foram selecionados, considerando o período em que foram depositados, antes da alta influência antrópica na área, e no tamanho do grão do sedimento. Apenas os níveis de lama foram selecionados, uma vez que os sedimentos finos tendem geralmente a ter maiores concentrações de elementos quimicos. A ocorrência de foraminíferos foi também analisada nas camadas selecionadas. Os resultados indicam que os sedimentos estudados foram depositados num contexto marinho de transição, após serem expostos a múltiplos ciclos sedimentares e a intemperismo. As concentrações de fundo, relacionadas a fontes naturais de sedimento foram estimadas para As, Cd, Co, Cr, Cu, Ni, Pb, Zn) e P e para outros elementos químicos. Esses resultados são úteis para a avaliação de impacto ambiental, não apenas na área de estudo, mas também em outras regiões costeiras do Estado do Rio de Janeiro. PALAVRAS-CHAVE: Multi-indicadores. Sedimentos. Registros Holocénicos. Litoral. Atlântico Sul.
7
Hussain, Mazhar, Daniel Levacher, Nathalie Leblanc, Hafida Zmamou, Irini Djeran-Maigre y Andry Razakamanantsoa. "Testing the Feasibility of Usumacinta River Sediments as a Renewable Resource for Landscaping and Agronomy". Sustainability 15, n.º 22 (11 de noviembre de 2023): 15859. http://dx.doi.org/10.3390/su152215859.
Texto completoResumen
Fluvial sediment recycling in agronomy is a relatively recent development, as sediment fertilizing potential for crops is unexplored. Freshwater sediments can act as fertilizer and improve the aeration of soils to increase the yield of crops, support vegetation for landscaping, and provide protective cover against erosion. This study focuses on the investigation of the agronomic potential of Usumacinta River sediments. The pH of the sediments is around 8.5, which is slightly alkaline. The organic matter content is low (5.7%). The sodium absorption ratio is 1.2 and the electrical conductivity is low (0.02 mS/cm). These values indicate that sediments are nonsaline, which is essential for the growth of crops and vegetation. The environmental characteristics of sediments show that the heavy metals, polycyclic aromatic hydrocarbon (PAH), and polychlorinated biphenyl (PCB) pollutants in sediments are below the recommended thresholds. In addition, sediments from the Usumacinta River contain minerals such as potassium and iron oxides that are helpful in improving the biological and nutritional characteristics of the soil. Furthermore, the pH, granulometry, mineralogy, organic matter, and carbonate contents of the Usumacinta River sediments are similar to agronomic soils. The Usumacinta River sediment’s potential for agronomy was practically investigated by sowing ryegrass (Lolium perenne) in a greenhouse by using the local climatic conditions and mixing sediments with potting soil. Three soil compositions were used to evaluate the germination and growth of ryegrass. The soil compositions were 100% potting soil (C1), 50% sediments + 50% potting soil (C2), and 100% sediments (C3). The growth rate of ryegrass was evaluated by monitoring the increase in grass height and production of fresh biomass. The germination of ryegrass was similar in all three compositions. The growth of ryegrass and production of fresh biomass were the most significant with 100% potting soil (0.25 kg/m2), somewhat less with sediment mix (0.18 kg·m2), and were the least significant with 100% sediments (0.05 kg/m2). The mixture of potting soil and sediments shows similar growth to 100% potting soil. The ryegrass seed germination, growth, and production of fresh biomass with the mixture of sediments gave encouraging results, and underlined the potential of sediments for soil amendments for agronomy and protective developments, such as limiting riverbank erosion, gardening, and landscaping.
8
Alves Martins, Maria Virgínia, Márcia Andréia Da Silva Nunes, Marcio Inacio Alves, Marco Helenio de Paula Alves Coelho, Wellen Fernanda Louzada Castelo, Lucia Maria Lorini, Denise Terroso et al. "GEOCHEMICAL NORMALIZERS APPLIED TO THE STUDY OF THE PROVENANCE OF LITHOGENIC MATERIALS DEPOSITED AT THE ENTRANCE OF A COASTAL LAGOON. A CASE STUDY IN AVEIRO LAGOON (PORTUGAL) / NORMALIZADORES GEOQUÍMICOS APLICADOS AO ESTUDO DE PROVENIÊNCIA DE MATERIAIS LITOGÉNICOS DEPOSITADOS NA ENTRADA DE UMA LAGUNA COSTEIRA. UM ESTUDO DE CASO NA LAGUNA DE AVEIRO (PORTUGAL)". Journal of Sedimentary Environments 3, n.º 2 (9 de junio de 2018): 74–92. http://dx.doi.org/10.12957/jse.2018.34815.
Texto completoResumen
The use of geochemical normalizers has been applied in sedimentological studies in several study contexts, such as pollution, diagenetic and provenance assessment. Selected textural and mineralogical data of 137 surface sediment samples were compared by statistical analyses with geogenic elements concentrations normalized by the Al, Be, Ce, Fe, Fe+Al, Li, Rb and Sc aiming to identify the best normalizer to trace different sources of bottom sediments for the Aveiro Lagoon entrance (NW of Portugal). The study area is heterogenous in terms of hydrodynamics and sedimentary processes.The most commonly applied geochemical normalizer for the sediments elemental concentrations has been the aluminum. However, the statistical analyses evidenced that the best normalizer was the scandium, since Principal Components Analysis results have evidenced that the element/Sc values are largely independent of sediment granulometry and thus have allowed the identification of compositional differences not related to grain size. Statistical analyses have also allowed to discriminate groups of stations that: i) trace the entry and exit of mixed sources sediments of the lagoon due to the action of tidal currents; ii) contain materials provided from the erosion of granitoids present mainly along the Douro River basin, located to the north, and transported southward by coastal drift; iii) encompasse sediments provided from the erosion of the Schist–Greywacke Complex crossed by the Vouga River that drains into the inner central zone of the lagoon and; iv) represent an area of sediment accumulation located near the entrance of Mira Channel, where lithogenic materials, provided by mixed lithologies in addition to organic matter, are being deposited. The results of this work contribute to the knowledge of the sedimentary dynamics of the Aveiro Lagoon, a coastal system which is part of a littoral stretch that is being strongly eroded, due to natural and anthropic causes and should be applicable to other coastal systems with similar characteristics. ResumoO uso de normalizadores geoquímicos tem sido aplicado em estudos sedimentológicos em diversos contextos, como por exemplo, de poluição, avaliação diagenética e de proveniência de sediments. Dados texturais e mineralógicos selecionados de 137 amostras de sedimentos superficiais foram comparados através de análises estatísticas com concentrações de elementos geogênicos normalizadas por Al, Be, Ce, Fe, Fe + Al, Li, Rb e Sc. O estudo visou identificar o melhor normalizador para traçar diferentes fontes de sedimentos de fundo para a entrada da Lagoa de Aveiro (NW de Portugal), uma área heterogênea em termos de processos hidrodinâmicos e sedimentares.O normalizador geoquímico mais comumente aplicado em sedimentos tem sido o alumínio. No entanto, as análises estatísticas evidenciaram que o melhor normalizador foi o escândio, uma vez que os resultados da análise de componentes principal evidenciaram que os valores das razões elemento/Sc são amplamente independentes da granulometria sedimentar e permitiram a identificação de diferenças composicionais não relacionadas com o tamanho do grão. Análises estatísticas também permitiram discriminar grupos de estações que: i) traçam a entrada e saída de fontes mistas de sedimentos da laguna, devido à ação das correntes de maré; ii) contêm materiais provenientes da erosão de granitóides presentes principalmente ao longo da bacia do Rio Douro, localizada a norte, e transportados para sul por deriva litoral; iii) contêm sedimentos provenientes da erosão do Complexo Xisto-grauvaquico atravessado pelo Rio Vouga, que desagua na zona central interna da laguna e; iv) representam uma área de acumulação de sedimentos localizada perto da entrada do Canal Mira, onde materiais litogênicos, fornecidos por litologias diversificadas, além de matéria orgânica, estão sendo depositados.Os resultados deste trabalho contribuem para o conhecimento da dinâmica sedimentar da Laguna de Aveiro, um sistema costeiro que faz parte de um trecho litorâneo fortemente erodido, devido a causas naturais e antrópicas and may be applicable to other coastal systems with similar characteristics.
9
Ding, Zhong Jun, Bao Hua Liu, Wei Gao y Xiang Mei Meng. "Analysis of Resistivity Characteristics of Sediments in Northwestern of South Yellow Sea". Applied Mechanics and Materials 568-570 (junio de 2014): 8–11. http://dx.doi.org/10.4028/www.scientific.net/amm.568-570.8.
Texto completoResumen
The resistivity characteristics of sediments are important to analyze marine sedimental environment and material source. A kind of penetration multiple parameter micro-probe which is designed to measure the resistivity of sediment sample in the northwestern of South Yellow Sea. In this paper, shelf sediment resistivity property off northwest of the South Yellow Sea is studied by analyzing the influence factors and relations, for providing valuable information to the marine sedimental environment around this area.
10
Vácha, R., J. Čechmánková, J. Skála, J. Hofman, P. Čermák, M. Sáňka y T. Váchová. "Use of dredged sediments on agricultural soils from viewpoint of potentially toxic substances". Plant, Soil and Environment 57, No. 8 (2 de agosto de 2011): 388–95. http://dx.doi.org/10.17221/105/2011-pse.
Texto completoResumen
A set of 29 pond sediments samples was collected. The sediments were separated into three groups, field, village, and forest pond sediments. The sediment samples were taken from pond bottoms and sediment heaps. The sediment characteristics (pH, CEC, Al-exchangeable, C<sub>ox</sub>, humus substances), the content of potentially toxic elements and persistent organic pollutants were analysed in the sediments and compared between sediment groups. The comparison of sediment contamination with Czech legislation for sediment use in agriculture was conducted. The village sediments were more loaded by potentially toxic elements and persistent organic pollutants than the others. The pH value of sediments was considered as the properties regulating the retention of potentially toxic elements and their mobility (Al, Cd, Zn). Polycyclic aromatic hydrocarbons (PAHs) were the most problematic POPs group in the sediments. The correlation showed poor dependency of POPs (especially PAHs) content on the content and quality of sediment organic matter.
11
Geersen, Jacob, Andrea Festa y Francesca Remitti. "Structural constraints on the subduction of mass-transport deposits in convergent margins". Geological Society, London, Special Publications 500, n.º 1 (19 de diciembre de 2019): 115–28. http://dx.doi.org/10.1144/sp500-2019-174.
Texto completoResumen
AbstractThe subduction of large and heterogeneous mass-transport deposits (MTDs) is discussed to modify the structure and physical state of the plate boundary and therewith exert an influence on seismicity in convergent margins. Understanding which subduction-zone architectures and structural boundary conditions favour the subduction of MTDs, primarily deposited in oceanic trenches, is therefore highly significant. We use bathymetric and seismic reflection data from modern convergent margins to show that a large landslide volume and long runout, in concert with thin trench sediments, increase the chances for an MTD to become subducted. In regions where the plate boundary develops within the upper plate or at its base (non-accretionary margins), and in little-sedimented trenches (sediment thickness <2 km), an MTD has the highest potential to become subducted, particularly when characterized by a long runout. On the contrary, in the case of a heavily sedimented trench (sediment thickness >4 km) and short runout, an MTD will only be subducted if the thickness of subducting sediments is higher than the thickness of sediments under the MTD. The results allow identification of convergent margins where MTDs are preferentially subducted and thus potentially alter plate-boundary seismicity.
12
Shaiek, Moez, Noureddine Zaaboub, Deniz Ayas, Maria Virgínia Alves Martins y Mohamed Salah Romdhane. "CRABS AS BIOINDICATORS OF TRACE ELEMENT ACCUMULATION IN MEDITERRANEAN LAGOON (BIZERTE LAGOON, TUNISIA) / CARANGUEJOS USADOS COMO BIOINDICADORES DE ACUMULAÇÃO DE METAIS NUMA LAGUNA MEDITERRÂNEA (LAGUNA DE BIZERTE, TUNÍSIA)". Journal of Sedimentary Environments 3, n.º 1 (25 de febrero de 2018): 1–11. http://dx.doi.org/10.12957/jse.2018.32950.
Texto completoResumen
Nine crab species samples, males and females, were collected after homogeneously prospection of sediment surface of Bizerte Lagoon. Crabs were caught by dip net from Bizerte Lagoon during spring 2012. Concentrations of metals (Zn, As, Cd, Cr, Cu, Fe, Ni, Pb and Zn) were evaluated in the carapace and muscle tissue of crabs and in surface sediment samples. Concentrations of metals accumulated in the benthic crabs tissues were compared to the reactive metals content that constitute the bioavailable fraction of the sediments. Total organic carbon and carbonate contents were also determined, since they are principal requirements associated with crab development.Results of this work indicate that, in the study area, the metals that reach the highest concentrations in the sediments-water interface are by decreasing order Zn, Cr and Pb. The reactive concentrations of these metals are also the highest. However, the trace elements that are being accumulated in the carapace and muscle of crabs are mainly As and Cu.Continental waters flowing into the Bizerte Lagoon are the main source and the principal cause of the enrichment of trace elements in sediment. Results highlight that the reactive concentrations of metals in sediments were the principal cause of their bioaccumulation in the crabs tissues.The important results of this work highlight that cabs can be very useful on studies of monitoring and evaluation of environmental quality in addition to data obtained from the sediment as they also give information about the bioaccumulation of metals through the oceanic food webs. ResumoNove amostras de espécies de caranguejos, machos e fêmeas, foram coletadas na superfície do sedimento da Laguna de Bizerte. Os caranguejos foram capturados com uma rede na Laguna de Bizerte, na primavera de 2012. Foram avaliadas nas carapaças e no tecido muscular dos caranguejos e em amostras de sedimentos superficiais, concentrações de metais (Zn, As, Cd, Cr, Cu, Fe, Ni, Pb e Zn). As concentrações de metais acumuladas nos tecidos de caranguejos bênticos foram comparadas com o teor de metais reativos que constituem a fração biodisponível dos sedimentos. Os teores totais de carbono orgânico e carbonato também foram determinados, uma vez que são requisitos principais associados ao desenvolvimento dos caranguejos.Os resultados deste trabalho indicam que, na área de estudo, os metais que atingem as maiores concentrações na interface sedimentos-água são, por ordem decrescente, Zn, Cr e Pb. As concentrações reativas desses metais também são as mais elevadas. No entanto, os metais que estão sendo acumulados nas carapaças e nos músculos dos caranguejos são principalmente As e Cu. As águas continentais que desembocam na Laguna Bizerte são a principal fonte e a principal causa do enriquecimento de metais nos sedimentos. Os resultados sugerem que as concentrações reativas de metais nos sedimentos foram a principal causa de sua bioacumulação nos tecidos dos caranguejos.Os resultados deste trabalho revelam que para além dos dados sedimentológicos, os caranguejos podem ser muito úteis em estudos de monitoramento e avaliação da qualidade ambiental, pois fornecem informações sobre a bioacumulação de metais através das cadeias alimentares oceânicas.
13
Chang, Chang Shen, A. H. Yusoff, C. A. R. Mohamed, S. F. Liu, N. F. Shoparwe, N. A. Husain y M. N. Azlan. "Geochemistry of Rare Earth Elements in Pahang River Sediment, Malaysia". Kompleksnoe Ispolʹzovanie Mineralʹnogo syrʹâ/Complex Use of Mineral Resources/Mineraldik Shikisattardy Keshendi Paidalanu 331, n.º 4 (25 de enero de 2024): 42–50. http://dx.doi.org/10.31643/2024/6445.37.
Texto completoResumen
Rare earth elements (REE) are a set of 17 chemically similar metallic elements including 15 lanthanides, scandium and yttrium. The current status of REE as a global strategic commodity has encouraged the identification of REE ore deposits. This research is carried out to identify the mining feasibility of fluvial sediment REE and to understand the sediment's physical and chemical characteristics and effects on the geochemical behaviour of REE in the longest river of Peninsular Malaysia namely Pahang River. Surface sediment samples were collected along Pahang River (n=44) in approximately 10 km distance intervals. The sediment samples were analyzed using XRF to determine the major oxide content. Meanwhile, REE content in the sediment samples was extracted using the Total Digestion method and analysed using ICP-MS. The results show the average value of ΣREE at surface sediments of the Pahang River is 42.58 ppm and can be considered too low to be economically mined. Each area shows higher fractionation of light REE than heavy REE with negative europium anomalies, suggesting sediments in this area were derived from felsic rocks. The concentration of REE in Pahang River surface sediments was controlled by the porosity and organic matter as showed by the correlation of ΣREE with porosity (R2=0.65) and organic matter content (R2=0.71). In conclusion, this research's findings are generally useful for further REE mineral exploration and fluvial sediment environmental monitoring.
14
Dewi, Alindya Eka Puspita, Zainul Hidayah, Akhmad Farid y Dwi Budi Wiyanto. "Karakteristik dan Distribusi Spasial Bahan Organik Pada Sedimen Dasar Perairan Teluk Pacitan Jawa Timur". Journal of Marine and Aquatic Sciences 8, n.º 2 (1 de febrero de 2023): 267. http://dx.doi.org/10.24843/jmas.2022.v08.i02.p11.
Texto completoResumen
Pacitan Bay is one of the semi-enclosed waters on East Java's south coast. This area is well-known for having a large fishing port as well as a beach tourism area. The dynamics of Pacitan Bay's waters due to the influence of currents, waves, and the input of water masses from the mainland are thought to affect the characteristics of the waters' bottom sediments. The objective of this study was to map the characteristics of bottom sediments and the distribution of organic substance. This research also analyzed the relationship between sediment characteristics and the concentration of organic subtance in the sediment. The sediment's characteristics were determined using granulometric analysis, and the organic matter content was determined using the Loss of Ignition (LOI) method. The analysis results show that sandy substrates dominate the bottom sediments of Pacitan Bay by an average of 82.22%. The distribution of sandy substrate dominates the bay's north and west. Distance from the shoreline has a significant effect on organic subtance distribution (One Way ANOVA, F = 6.05; p 0.05). The organic matter content of sediments dominated by sand is lower (R2 = 0.76) compared to substrates with softer grain size (silt or mud) and tighter pores, making organic matter efficient to precipitate.
15
Locat, Jacques y Serge Leroueil. "Physicochemical and geotechnical characteristics of recent Saguenay Fjord sediments". Canadian Geotechnical Journal 25, n.º 2 (1 de mayo de 1988): 382–88. http://dx.doi.org/10.1139/t88-039.
Texto completoResumen
In the spring of 1985 the first goetechnical reconnaissance of recent Saguenay Fjord sediments took place, in which were recorded the two Saint-Jean-Vianney slides of 1663 and 1971. Cores from the upper part of the fjord were tested onboard the ship and in the laboratory. The mineralogy of the recent sediments is like that of the raised marine deposits of the area, except for the organic content, which is higher. The microstructure of the sediment is quite typical of flocculated marine soils. The freshly sedimented soil, in its sedimentary environment, has gained strength and sensitivity (up to 12) in excess of what is usually expected for such material. It has been concluded that the physicochemical characteristics of the sediment, such as depicted by its initial plasticity (before leaching), are first-order parameters in the source of apparent overconsolidation and structuration. Key words: recent sediments, shear strength, sensitivity, consolidation, structuration, microstructure, landslide, physicochemistry, mineralogy.
16
Inamdar, Shreeram, Nathan Sienkiewicz, Alyssa Lutgen, Grant Jiang y Jinjun Kan. "Streambank Legacy Sediments in Surface Waters: Phosphorus Sources or Sinks?" Soil Systems 4, n.º 2 (11 de mayo de 2020): 30. http://dx.doi.org/10.3390/soilsystems4020030.
Texto completoResumen
Streambank legacy sediments can contribute substantial amounts of sediments to Mid-Atlantic waterways. However, there is uncertainty about the sediment-bound P inputs and the fate of legacy sediment P in surface waters. We compared legacy sediment P concentrations against other streambank sediments and upland soils and evaluated a variety of P indices to determine if legacy sediments are a source or sink of P to surface waters. Legacy sediments were collected from 15 streambanks in the mid-Atlantic USA. Total P and M3P concentrations and % degree of phosphorus saturation (DPS) values for legacy sediments were lower than those for upland soils. % DPS values for legacy sediments were below the water quality threshold for P leaching. Phosphorus sorption index (PSI) values for legacy sediments indicated a large capacity for P sorption. On the other hand, equilibrium phosphorus concentration (EPC0) for legacy sediments suggested that they could be a source or a sink depending on stream water P concentrations. Anoxic conditions resulted in a greater release of P from legacy sediments compared to oxic conditions. These results suggest that legacy sediment P behavior could be highly variable and watershed models will need to account for this variability to reliably quantify the source-sink behavior of legacy sediments in surface waters.
17
Saanei, Saba, Khalil Rezaei, Mehran Arian, Seyed Mohsen Al Ali y Pantea Giahchi. "Changes in particle sizes and geochemistry of Siyah Keshim lagoon sediment of Gilan province to determine origin and tectonic position of sediment". Journal of Geology, Geography and Geoecology 29, n.º 3 (11 de octubre de 2020): 562–71. http://dx.doi.org/10.15421/112051.
Texto completoResumen
Useful information was obtained about the environmental condition of this region such as energy, sediment location, origin, sediment carrying path, pond evolutionary process, and tectonic conditions and origins of sediments by studying physical and geochemical sediment changes processes in place and time, distribution of sediments and elements in lagoon bed, and also identification the effective factors on sediment distribution model. In this regard, 59 sediment samples were taken from Siyah Keshim lagoon and were analyzed chemically and aggregation by XRF and ICP-MS technic. Adaptation of data by Folk diagrams showed that this region is placed in a range of sand, muddy sand, sand with a little gravel, muddy sand with a little gravel, and silty sand. Weak to medium sorting and negative tilting shows sediment in a coastal area. Geochemical evidence shows that SiO2/Al2O3 ratio in these sediments is 2.6-3.7. In addition, Na2O value shows relatively low sediment investigation for sediments of this lagoon. Moreover, determination of the weathering effect in origin place by the chemical index of alteration (CIA) and chemical weathering index (CWI) shows intensive chemical alternation on sediments. Index of combined variety was averagely 1.54 in the studied sediments and show that sediments resulted from the first cycle sediment. Using tectonic separating diagrams based on the primary and secondary oxidants percentage show the sediment in the active continent margin (ACM), continent-island arc (CIA), and oceanic island arc (OIA) and shows that the studied sediments are related to subduction margin.
18
Ferreira, Ana Margarida y Carlos Coelho. "Artificial Nourishments Effects on Longshore Sediments Transport". Journal of Marine Science and Engineering 9, n.º 3 (24 de febrero de 2021): 240. http://dx.doi.org/10.3390/jmse9030240.
Texto completoResumen
Serious erosion problems related to significant negative sediments budgets in the coastal systems are referred worldwide. Artificial nourishments are a coastal erosion mitigation strategy that allow for a decrease in those negative budgets by adding sediment to the coastal system. Thus, it is essential to understand and adequately model the shoreline response after a nourishment operation, in order to support the definition of the best intervention scenarios. The main goal of this work was to study the artificial nourishment effects on the longshore sediment transport and consequently on the morphological evolution at the intervention site and nearby areas, in a time horizon of 5 years. The longshore transport of the nourished sediments was evaluated, aiming to contribute to the evaluation of the sediment’s permanence at the deposition site and the frequency required for new nourishments. The shoreline evolution numerical long-term configuration (LTC) model was applied in order to evaluate the spatial and temporal distribution of the nourished sediments along the coast, considering different types of beaches and incident wave climates. The adopted approach is generic and supported by simple numerical models, which can be useful for preliminary site-specific evaluations. The results show that the nourishment impact is mainly observed nearby the intervention site. It is highlighted that higher longshore sediment transport rates are associated with more energetic wave climates, but not necessarily with incident waves more oblique to the shoreline.
19
James, William F., John W. Barko y Harry L. Eakin. "Impacts of sediment dewatering and rehydration on sediment nitrogen concentration and macrophyte growth". Canadian Journal of Fisheries and Aquatic Sciences 61, n.º 4 (1 de abril de 2004): 538–46. http://dx.doi.org/10.1139/f04-018.
Texto completoResumen
River sediments were experimentally dewatered via exposure to air from an initial moisture content of 75% to 61% (~20% dewatered), 32% (~60% dewatered), and 4% (~95% dewatered). Sediments dewatered by 20% and 60% and rehydrated exhibited a lower exchangeable ammonium-N (NH4-N) concentration and a lower rate of nitrate/nitrite-N and NH4-N release from sediments compared with controls. In contrast, sediments dewatered by 95% and rehydrated exhibited a marked increase in exchangeable sediment NH4-N and a much higher rate of nitrate/nitrite-N (under oxic conditions) and NH4-N (under oxic and anoxic conditions) release from sediments. Sediment dewatered by 60% and 95% and rehydrated lost total N (18%), suggesting denitrification. Growth of Potamogeton pectinatus responded to changes in the exchangeable sediment NH4-N concentration; it was lower on partially dewatered and rehydrated sediments that exhibited lower exchangeable sediment NH4-N and elevated on sediment that was dewatered by 95%. Our results suggest that sediment N may be altered via sediment dewatering and rehydration to affect macrophyte growth.
20
Sirqueira, Evellynn Sato, Frederico Terra de Almeida, Handrey Borges de Araújo, Cornélio Alberto Zolin, Glauber Altrão Carvalho, Rhavel Salviano Dias Paulista, Apoliano Francisco da Silva y Daniela Roberta Borella. "VAZÃO LÍQUIDA, SEDIMENTOS EM SUSPENSÃO E TURBIDEZ NA MICROBACIA DO RIO CAIABI, NO ECOTÓNO CERRADO-AMAZÔNIA". Nativa 10, n.º 4 (28 de noviembre de 2022): 525–32. http://dx.doi.org/10.31413/nativa.v10i4.13961.
Texto completoResumen
Objetivou-se determinar as vazões líquidas, as concentrações de sedimentos em suspensão e a turbidez em uma seção fluviométrica, na região central da microbacia hidrográfica do rio Caiabi (MBHRC), localizada na transição da floresta Amazônica e do Cerrado. Foram estabelecidas curvas-chaves para as vazões líquidas e sólidas, além de estimativas da turbidez. O monitoramento a campo ocorreu entre dezembro de 2020 e dezembro de 2021, com mensuração mensal de vazões líquidas e coletas de amostras de água e sedimentos. Os resultados adquiridos possibilitaram ajustes da curva-chave líquida com índice de Nash-Sutcliffe (NSE) de 0,9928, coeficiente de determinação (R²) de 0,9964 e do desvio médio absoluto (D%) de 3,7264. Por meio de ajuste de relações entre as variáveis avaliadas, observou-se que a descarga líquida pode explicar cerca de 80% da descarga de sedimentos na MBHRC, enquanto, a concentração de sedimentos em suspensão pode explicar cerca de 70% da descarga total de sedimentos. Os valores de turbidez medidos por turbidímetro foram correlacionados com a concentração de sedimentos em suspensão e com as descargas sólidas em suspensão, resultando em valores de R² de até 0,8807 (NTU x Css) e R² de até 0,7185 (NTU x Qss). Palavras-chave: hidrossedimentologia; turbidímetro; concentração de sedimentos; correlação. Net flow, suspended sediments and turbidity in the Caiabi River microbasin, in the Cerrado-Amazon ecotono ABSTRACT: The objective was to determine the liquid flows, the suspended sediment concentrations and the turbidity in a fluviometric section, in the central region of the Caiabi River microbasin (MBHRC), located in the transition between the Amazon forest and the Cerrado. Key curves were established for liquid and solid flows, in addition to turbidity estimates. Field monitoring took place between December 2020 and December 2021, with monthly measurement of liquid flows and collection of water and sediment samples. The acquired results made it possible to adjust the net key curve with a Nash-Sutcliffe index (NSE) of 0.9928, coefficient of determination (R²) of 0.9964 and absolute mean deviation (D%) of 3.7264. By adjusting the relationships between the variables evaluated, it was observed that the net discharge can explain about 80% of the sediment discharge in the MBHRC, while the concentration of suspended sediments can explain about 70% of the total discharge. of sediment. The turbidity values measured by Turbidimeter were correlated with the concentration of suspended sediments and with the total solid discharges, resulting in R² values up to 0.8807 (NTU X Qss) and R² values up to 0.7185 (NTU x Css). Keywords: hydrosedimentology; turbidimeter; sediment concentration; correlation.
21
Kumari, Anupama, Chandrajit Balomajumder, Amit Arora, Gaurav Dixit y Sina Rezaei Gomari. "Physio-Chemical and Mineralogical Characteristics of Gas Hydrate-Bearing Sediments of the Kerala-Konkan, Krishna-Godavari, and Mahanadi Basins". Journal of Marine Science and Engineering 9, n.º 8 (27 de julio de 2021): 808. http://dx.doi.org/10.3390/jmse9080808.
Texto completoResumen
The characteristics of the hydrate-bearing sediments affect the formation and dissociation of gas hydrate in sediments. The mineral composition, their dispersion, and chemical composition of hydrate-bearing sediment samples plays a dominant role in the hydrate stability condition and its economic development. In this paper, the physical properties of hydrate-bearing sediment of India are compared with each other. The sediment samples are taken from the Krishan-Godavari basin (Depth—127.5 and 203.2 mbsf), Mahanadi basin (Depth—217.4 mbsf), and Kerala-Konkan basin (Depth—217.4 mbsf). The saturation of the gas hydrate observed at these sites is between 3 and 50%. Particle size is an important parameter of the sediments because it provides information on the transportation and deposition of sediment and the deposition history. In the present study, we investigated the mineralogy of hydrate-bearing sediments by chemical analysis and X-ray Diffraction. XRD, FTIR, and Raman Spectroscopy distinguished the mineralogical behavior of sediments. Quartz is the main mineral (66.8% approx.) observed in the gas hydrate-bearing sediments. The specific surface area was higher for the sediment sample from the Mahanadi basin, representing the sediments’ dissipation degree. This characterization will give important information for the possible recovery of gas from Indian hydrate reservoirs by controlling the behavior of host sediment. SEM analysis shows the morphology of the sediments, which can affect the mechanical properties of the hydrate-bearing sediments. These properties can become the main parameters to consider for the design of suitable and economic dissociation techniques for gas hydrates formed in sediments.
22
Spencer, K. L. y C. L. MacLeod. "Distribution and partitioning of heavy metals in estuarine sediment cores and implications for the use of sediment quality standards". Hydrology and Earth System Sciences 6, n.º 6 (31 de diciembre de 2002): 989–98. http://dx.doi.org/10.5194/hess-6-989-2002.
Texto completoResumen
Abstract. Total metal concentrations in surface sediments and historically contaminated sediments were determined in sediment cores collected from three estuaries (Thames, Medway and Blackwater) in south-east England. The partitioning behaviour of metals in these sediments was also determined using a sequential extraction scheme. These data were then compared with sediment quality values (SQVs) to determine the potential ecotoxicological risk to sediment dwelling organisms. When total metal concentrations in surface sediments are examined, no risk to biota in any of the estuaries is indicated. However, when historically contaminated sediments at depth are also considered, risks to biota are apparent and are greatest for the Thames, followed by the Medway and then the Blackwater. This suggests that regulatory authorities should examine vertical metal profiles, particularly in estuaries that are experiencing low sediment accumulation rates where historically contaminated sediments are in the shallow sub-surface zone and where erosion or dredging activities may take place. When metal partitioning characteristics are also considered, the risk to biota is comparable for the Medway and the Blackwater with the potentially bioavailable fraction presenting no ecotoxicological risk. Conversely, over 70% of metals are labile in the Thames Estuary sediments and toxic effects are probable. This suggests that the application of SQVs using total sediment metal concentrations may over- or under-estimate the risk to biota in geochemically dissimilar estuarine sediments. Keywords: sediment quality values, estuarine sediments, metal contamination, partitioning, sequential extraction
23
Cook, Nancy H. y Peter G. Wells. "Toxicity of Halifax Harbour Sediments: an Evaluation of the Microtox® Solid-Phase Test". Water Quality Research Journal 31, n.º 4 (1 de noviembre de 1996): 673–708. http://dx.doi.org/10.2166/wqrj.1996.037.
Texto completoResumen
Abstract Subtidal sediments were collected in Halifax Harbour, Nova Scotia, in July and August, 1992, to study sediment toxicity and hazards near the proposed location of a sewage treatment plant and outfall. A set of 110 samples from eight stations was evaluated. Interstitial water from surface (0-2 cm) and subsurface (2-4 cm) sediments was analyzed by the Microtox® 100% toxicity test protocol. The sediment particles were analyzed using the Microtox® solid-phase test. Interstitial water from surface and subsurface sediments from all stations was usually non-toxic, compared to a phenol standard. The mean 5 min-EC50 of surface sediments (n=57) was 5,433mg/L; the mean 5 min-EC50 of subsurface sediments (n=50) was 804 mg/L. Toxicity thresholds for the harbour sediments were compared with National Research Council marine analytical sediment reference materials and a selection of natural sediments, and ranked. An experiment with the marine reference sediments (certified for PAHs and trace metals) and their mixtures showed the ability of the solid-phase test to discriminate among different levels of contaminated sediments. Intra- and inter-sample variability in toxicity at different locations in relation to time, sediment depth, sediment properties, and types and concentrations of contaminants was evaluated by multivariate and PCA tech-niques. This laboratory-field study provided insights into the sensitivity, repro-ducibility, significance and discriminatory ability of the Microtox® solid-phase bioassay and its value in the study of complex natural sediment mixtures.
24
Suryono, Chrisna Adhi, Ibnu Pratikto y Ajeng Rusmaharani. "Logam Berat Anthropogenik Pb dan Cu pada Lapisan Sedimen Permukaan dan Dasar Muara Sungai di Kota Semarang, Jawa Tengah Indonesia". Jurnal Kelautan Tropis 22, n.º 1 (13 de abril de 2019): 87. http://dx.doi.org/10.14710/jkt.v22i1.3223.
Texto completoResumen
Semarang coastal areas as specially on river down stream have been develop to industrial, dumpping areas and human settlement. Its will be caused increasing sedimentation and anthropogenic heavy metals accumulation in sediments. In order to assess Pb, and Cu on diferent layers of sediments on three down stream rivers on Semarang, samples of surface and bed sediment were collected for analyzed by ICPMS. The result showed that the heavy metal of Pb on bed layer was higher than Pb on surface sediment, on the other hand Cu on surface sediment was higher than Cu on bed sediments. Unfraternally the heavy metal concentration on surface and beds sediments they do not correlation with totals organic carbon and combination silt and clay in sediment on three down stream rivers on Semarang. Wilayah pesisir Semarang terutama di daerah muara sungai telah berkembang menjadi kawasan industri, penimbunan dan hunian. Hal tersebut menyebabkan peningkatan sedimentasi dan akumulasi antropogenik logam berat dalam sedimen. Untuk mengetahui logam berat Pb dan Cu dalam permukaan dan dasar sedimen di tiga muara sungai Semarang. Maka sampel pada permukaan dan dasar sedimen diambil dan dianalisa dengan ICPMS. Hasil pengukuran menunjukan bahwa konsentrasi logam Pb pada lapisan dasar lebih tinggi dari pada lapisan permukaan sedimen, sebaliknya konsentrasi logam Cu pada lapisan permukaan lebih tinggi dari pada lapisan dasar sedimen. Namun keseluruhan antropogenik logam berat Pb dan Cu pada lapisan permukaan maupun bawah sedimen tidak ada korelasinya dengan kandungan total bahan organik karbon dan kombinasi antara silt dan clay dalam sedimen di ketiga mura sungai di Semarang.
25
Culp, Joseph M., Frederick J. Wrona y Ronald W. Davies. "Response of stream benthos and drift to fine sediment deposition versus transport". Canadian Journal of Zoology 64, n.º 6 (1 de junio de 1986): 1345–51. http://dx.doi.org/10.1139/z86-200.
Texto completoResumen
Field experiments were conducted to investigate the responses of benthic macroinvertebrate communities to experimental additions of fine sediments into riffles having a flow with either low tractive force so the sediments were deposited or sufficient tractive force to transport the added sediments. Sediment deposition had no measurable impact on most taxa, the only negative effects being significantly higher drift rates and lower benthic densities for Paraleptophlebia. Sediment transport by saltation created a physical disturbance that reduced total benthic densities by >50% in 24 h and significantly influenced macroinvertebrate community composition. Changes in the benthic community were the result of catastrophic drift, and distinct immediate and delayed responses of diurnal drift to the saltating sediments were evident. Taxa with the immediate drift response resided predominantly at the substrate surface and were instantaneously exposed to scouring as sediments were added. Macroinvertebrates showing the delayed response initially avoided the saltating sediments because of their deeper distribution, but an apparent diel shift in vertical distribution exposed these taxa to saltating sediments 6–9 h after sediment additions. Thus, even when tractive forces were insufficient to suspend fine sediments, catastrophic drift was initiated by fine sediments that slid and bounced along the surface of the stony substrate. Sediment saltation, therefore, has the potential to act as a community-level disturbance early in the storm hydrograph or at lower discharge magnitudes than required to suspend sediments.
26
Shuman, Tyler C., Peter C. Smiley, Robert B. Gillespie y Javier M. Gonzalez. "Influence of Physical and Chemical Characteristics of Sediment on Macroinvertebrate Communities in Agricultural Headwater Streams". Water 12, n.º 11 (23 de octubre de 2020): 2976. http://dx.doi.org/10.3390/w12112976.
Texto completoResumen
Agricultural land use leads to changes in physical and chemical characteristics of sediment that influence macroinvertebrate community diversity and abundance in streams. To the best of our knowledge the joint influence of sediment’s physical and chemical characteristics on stream macroinvertebrates has not been assessed. We measured sediment’s physical and chemical characteristics and sampled macroinvertebrates in eight agricultural headwater streams in Indiana, Michigan, and Ohio, United States, in 2017 and 2018 to determine the physical and chemical conditions of the sediment, to evaluate the relationships between physical and chemical characteristics of the sediment, and the relationship of macroinvertebrate communities with the sediment’s physical and chemical characteristics. Sediments within most sites were dominated by sand or silt. pH was suitable for macroinvertebrates and nitrate, herbicide, and trace metal concentrations were below concentration levels anticipated to affect macroinvertebrate survival. Linear mixed effect model analysis results indicated that a physical gradient of percent small gravel and percent silt was positively correlated (p < 0.05) with a chemical gradient of potassium concentrations, magnesium concentrations, and percent total nitrogen in the sediments. Our linear mixed effect model analysis results also indicated that Invertebrate Community Index scores were negatively correlated (p < 0.05) with a chemical gradient of simazine and calcium concentrations and were negatively correlated (p < 0.05) with physical gradient of grain size diversity and percent sand. Our results suggest that watershed management plans need to address physical and chemical degradation of sediment to improve macroinvertebrate biotic integrity within agricultural headwater streams in the Midwestern United States.
27
Mwamburi, Job. "Chromium Distribution and Spatial Variations in the Finer Sediment Grain Size Fraction and Unfractioned Surficial Sediments on Nyanza Gulf, of Lake Victoria (East Africa)". Journal of Waste Management 2016 (17 de mayo de 2016): 1–15. http://dx.doi.org/10.1155/2016/7528263.
Texto completoResumen
Surficial sediments collected from the Nyanza Gulf of Lake Victoria (East Africa) were used to determine spatial concentrations of Cr and determine differences in contents of the unfractioned (whole sediment) and the finer grain size sediments, establishing any changes in Cr enrichment and potential ecological risks using sediment quality guidelines. A single pollution index was also used to evaluate level of Cr contamination. The spatial mean Cr contents in the <63 µm (silt-clay) fraction were found to be significantly lower than those in the unfractioned sediments, but with a strong linear positive correlation. The study results show decreasing spatial amounts of Cr in surficial sediments of the Nyanza Gulf, when compared to a study done 20 years earlier. However, the 95% confidence limits of the overall mean Cr in unfractioned sediments exceed the threshold effect concentration (TEC), indicating the potential for Cr remobilization from sediments. In general the sediment enrichment is evidence of possible dominance of lithogenous sources of Cr in the surface lake sediments, with potential anthropogenic sources from the drainage system and nearshore urban areas. The sediments are unpolluted with respect to geoaccumulation index, and sediment enrichment factors suggest a minor to moderate enrichment of Cr in surficial sediments of three sites around the Nyanza Gulf zones and around the river mouth in the main lake.
28
Tretjakova, Rasma y Andris Karpovičs. "MINERAL COMPOSITION OF SOME LATGALE LAKE SEDIMENTS". ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference 1 (20 de junio de 2019): 304. http://dx.doi.org/10.17770/etr2019vol1.4146.
Texto completoResumen
Our research is focused on sedimentological conditions and postdepositional changes of recent fine grained lake sediments. We used bulk sediment mineralogical composition and grain size distribution as indicators to identify sediment source areas and possible changes during Holocene. We analysed fine grained (clayey) sediments from three Latgale lakes - Zeili, Pauguļi and Plusons, situated in Latgale upland. Lake sediments cover Late Pleistocene glacial deposits – loam and sandy loam. Bulk mineral composition of 6 sediment samples was determined by X-ray diffraction (XRD). Sediments contained typical minerals found in surrounding glacial sediments: rock-forming minerals as quartz, plagioclase, albite, enstatite, dolomite, calcite, and clay minerals - illite, kaolinite. To identify postdepositional changes in lake sediments of Holocene age clay minerals in clay fraction (<2 mkm) should be analysed. Particularly illite, smectite mixed layered minerals - illite/smectite (I/Sm) and chlorite. Additionally, grain size distribution of studied lake sediments was analysed. Accordingly, our studied sediments are clays, silty clays and clayey silts with bimodal particle distribution, except two samples from Zeiļi and Plusons with unimodal distribution.
29
Cieśla, Maksymilian, Renata Gruca-Rokosz y Lilianna Bartoszek. "The Connection between a Suspended Sediments and Reservoir Siltation: Empirical Analysis in the Maziarnia Reservoir, Poland". Resources 9, n.º 3 (11 de marzo de 2020): 30. http://dx.doi.org/10.3390/resources9030030.
Texto completoResumen
This paper presents research on the influence of suspended sediments on selected aspects of a reservoir’s functioning. As the amount of sediment suspended in water (SS) there was found to correlate significantly with sedimentation rate (Us), it was possible to develop a function allowing the rate of accumulation of sediments to be predicted by reference to known amounts of suspended sediment. The latter factor was also shown to correlate significantly with the content of organic matter in suspension (OMSS), in sediment captured in a sediment trap (OMS), and of bottom sediment (OMSB). Analysis of amounts of suspended sediment can provide for estimates of total loads of organic pollutants deposited in the sediments of a reservoir. A further significant correlation with SS was noted for the concentration of total phosphorus in water (TPW), confirming the importance of internal production where the circulation of this biogenic substance in a reservoir ecosystem is concerned. Analysis of stable carbon isotopes in turn showed that entrapped sediments were depleted of—or enriched in—13C, in line with whether concentrations of total P in those sediments (TPS) were at their highest or lowest levels. This dependent relationship may thus be of key importance in assessing sources of phosphorus, as well as in forecasting concentrations present in reservoir sediments. The results obtained make it clear that sediments suspended in the water of a reservoir unify phenomena and processes ongoing there, between elements of the water-sediment system.
30
Yuan, Xu Yin, Quan Liu, Ji Zhou Li, Jun Feng Ji y Chang Ping Mao. "Risk Assessment of Organochlorine Compounds in Water and Surface Sediments from Taihu Lake and Nanjing Section of Changjiang, China". Advanced Materials Research 356-360 (octubre de 2011): 624–29. http://dx.doi.org/10.4028/www.scientific.net/amr.356-360.624.
Texto completoResumen
Samples of surface water and sediment were collected in Taihu Lake and Nanjing section of Changjiang. Organochlorine compounds(OCCs) of samples were detected to investigate the characteristics and ecological risk of them in the lake and river. The concentrations of OCCs in water of Nanjing section of Changjiang were higher than those in Taihu Lake, but the concentrations of OCCs in sediments were higher in Taihu Lake. HCHs of Taihu sediments were relatively enriched, indicating the agricultural source of compounds. PCBs of Changjiang sediments were higher compared to Taihu sediments, denoting a obvious industrial source. Comparing with other compartments in China, HCHs of the study area were higher than most sediment of Chinese rivers, DDTs didn’t show high contents in sediments, PCBs was in relatively low levels. By contrast with the relevant sediment quality guidelines of these compounds, the ecological risk of OCCs in sediments were evaluated. The OCCs of sediments in Taihu Lake and Nanjing section of Changjiang didn’t show high ecological risk.
31
Wang, Weibo, Xu Wang, Xiao Shu, Baoru Wang, Hongran Li y Quanfa Zhang. "Denitrification of Permeable Sand Sediment in a Headwater River Is Mainly Influenced by Water Chemistry, Rather Than Sediment Particle Size and Heterogeneity". Microorganisms 9, n.º 11 (22 de octubre de 2021): 2202. http://dx.doi.org/10.3390/microorganisms9112202.
Texto completoResumen
Sediment particle size and heterogeneity play an important role in sediment denitrification through direct and indirect effects on, for example, the material exchange rate, environmental gradients, microbial biomass, and grazing pressure. However, these effects have mostly been observed in impermeable sediments. On the other hand, the material exchange of permeable sediments is dominated by advection instead of diffusion, with the exchange or transport rates exceeding those of diffusion by two orders of magnitude relative to impermeable sediments. The impact of permeable sediment particle size and heterogeneity on denitrification remains poorly understood, especially at the millimeter scale. Here, we conducted an in situ control experiment in which we sorted sand sediment into four homogeneous-particle-sizes treatments and four heterogeneous treatments. Each treatment was deployed, in replicate, within the riffle in three different river reaches with contrasting physicochemical characteristics. After incubating for three months, sediment denitrifier communities (nirS, nirK, nosZ), denitrification gene abundances (nirS, nirK, nosZ), and denitrification rates in all treatments were measured. We found that most of the denitrifying microbes in permeable sediments were unclassified denitrifying microbes, and particle size and heterogeneity were not significantly correlated with the functional gene abundances or denitrification rates. Water chemistry was the key controlling factor for the denitrification of permeable sediments. Water NO3−-N directly regulated the denitrification rate of permeable sediments, instead of indirectly regulating the denitrification rate of sediments by affecting the chemical characteristics of the sediments. Our study fills a knowledge gap of denitrification in permeable sediment in a headwater river and highlights that particle size and heterogeneity are less important for permeable sediment denitrification.
32
Richter, Kenneth y Jennifer Ayers. "An Approach to Predicting Sediment Microbial Fuel Cell Performance in Shallow and Deep Water". Applied Sciences 8, n.º 12 (14 de diciembre de 2018): 2628. http://dx.doi.org/10.3390/app8122628.
Texto completoResumen
Here we present an approach to predicting sediment microbial fuel cell performance based on environmental conditions. Sediment total organic carbon and water temperature were found to be important determinants in predicting the power output from microbial fuel cells in shallow sediments (<100 m) in San Diego. We extrapolated data from the in situ San Diego experiments to predict MFC performance in shallow sediments in other locations, namely the Gulf of Mexico and the Yellow Sea. Finally, using laboratory data of MFC performance in deep water (~1000 m) sediment samples, we extend our predictions to ocean sediments worldwide. We predict low power output from the deep sea (microwatts) relative to the shallow sediments (milliwatts), and attribute that to a possible lack of electrogenic bacteria in the sediments, lower sediment permeability, or a greater proportion of refractory organic matter reaching the bottom.
33
Droppo, Ian G. "Biofilm structure and bed stability of five contrasting freshwater sediments". Marine and Freshwater Research 60, n.º 7 (2009): 690. http://dx.doi.org/10.1071/mf08019.
Texto completoResumen
Using an annular flume, erosion characteristics of five diverse sediment types (stormwater pond, contaminated lacustrine, fluvial, aquaculture waste and industrial grade kaolin sediment), each with different physical and biological characteristics, were examined for relative erosion resistance and factors contributing to bed sediment stability. Suspended flocs represent primary building blocks of bed sediment with mass settling being independent of suspended solid concentration. Biofilm growth period, depositing floc structure and composition, nutrient supply and sediment properties all played a complex role in dictating the stability of the sediments. The river, lake and stormwater pond sediments were the most resistant to erosion relative to the high nutrient and organic content aquaculture sediment and kaolin. Biofilms developed to varying degrees on all sediments with the greatest growth occurring with the aquaculture sediment and the least with kaolin. While electrochemical properties will provide some attraction and stabilising forces, with no measurable consolidation evident for the examined sediments, it is suggested that active biofilm development was the dominant factor controlling bed stability and erosion potential. Differences in biological mediation of strength between sediments were partially attributed to the structural differences within the biofilms and integration of the extracellular polymeric fibril matrix within the sediment pores.
34
Clark, M. W. y D. M. McConchie. "Development of acid sulfate soil in sub-aerially disposed dredge spoil at Fisherman Islands, Brisbane, Australia". Soil Research 42, n.º 6 (2004): 553. http://dx.doi.org/10.1071/sr03072.
Texto completoResumen
During disposal of Brisbane River estuary dredge sediments into the reclamation paddocks at Fisherman Islands, a size separation of the fine (<63 µm) pyrite-rich silts and clays from the coarser (>63 µm) pyrite-poor sands and gravels occurs. The sand and gravel fractions contain most of the shell material and, therefore, most of the acid-neutralising capacity. In the most recently reclaimed paddock this size separation is of little consequence because sediments remain well buffered and acid produced from sulfides contained in the oxidising estuarine sediments is readily neutralised by the large volume of seawater and fine-grained carbonate minerals. However, as more sediment is added to the paddock, sediments become anoxic and sulfate reduction within the sedimentary pile occurs. This reduction rapidly produces pyrite and black monosulfides, consequently the pyrite content and degree of pyritisation and sulfidisation (DOP, DOS) of the sediment increase. Sulfide production rapidly removes sulfate from sediment pore waters and the process quickly becomes sulfate-limited because the fine-grained sediment texture restricts sediment permeability and therefore sulfate replenishment. Consequently, a clear relationship between DOP and DOS is observed for the reclamation paddock sediments. However, pre-existing mud-flat, and older unbunded dredge spoil sediments from the 1960s and 1970s, have no clear relationship between DOP and DOS values because they contain fewer fines and the production of pyrite was not limited by sulfate availability, but was constrained by other geochemical factors (e.g. redox potential, organic matter, or iron availability). Because of the increasing pyrite content of the paddock sediments as they age, the carbonate-buffering capacity provided by the sediment is readily exceeded, and the sediments become potentially acid sulfate. Should these sediments subsequently be disturbed and allowed to oxidise, the surrounding environment could be subject to large quantities of metal-rich acidic waters.
35
Alrawi, Reem A., Nik Norulaini Nik Ab Rahman, Anees Ahmad, Norli Ismail y A. K. Mohd Omar. "Characterization of Oily and Non-Oily Natural Sediments in Palm Oil Mill Effluent". Journal of Chemistry 2013 (2013): 1–11. http://dx.doi.org/10.1155/2013/298958.
Texto completoResumen
Palm oil is one of the many vegetable oils widely consumed around the world. The production of palm oil requires voluminous amount of water with the concurrent generation of large amount of wastewater known as palm oil mill effluent (POME). POME is a mixture of water, oil, and natural sediments (solid particles and fibres).There is a dearth of information on the physical properties of these POME sediments. This study intends to distinguish the physical properties of oily and non-oily POME sediments which include sediment size, particle size distribution (PSD), sediment shape, sediment surface morphology, and sediment density. These characterizations are important for future researches because these properties have significant effects on the settling process that occurs either under natural gravity or by coagulations. It was found that the oily and non-oily POME sediments have different sizes with nonspherical irregular shapes, and because of that, the aspect ratio (AR) and circularity shape factors were adopted to describe the shapes of these sediments. The results also indicate that the density of oily POME sediment decreases as the sediment size increases.
36
Carneiro, Fernando Rocha, Arthur Ayres Neto, Rodrigo Menezes Raposo de Almeida y Sidney de Matos Mello. "GEOTECHNICAL DESCRIPTION OF SANDY SEDIMENTS OF THE SURF ZONE USING ELECTRICAL RESISTIVITY MEASUREMENTS". Revista Brasileira de Geofísica 36, n.º 3 (6 de septiembre de 2018): 1. http://dx.doi.org/10.22564/rbgf.v36i3.1952.
Texto completoResumen
ABSTRACT. The geotechnical description of sandy sediments of the surf zone was done in two ways: directly, through standard geotechnical testing proposed by ASTM (American Society for Testing and Materials) and indirectly, through electrical resistivity measurements. The geotechnical property chosen for the description of the sediment was porosity, due to its influence in a wide range of soil properties. The indirect estimate of porosity through resistivity measurements was based on Archie’s equation. However, the difficulty in generalizing this equation is the empirical determination of the cementation exponent (m). For this reason, the values proposed by other authors were tested. A comparison of the porosity values obtained by the two methods (directly and indirectly using different values for cementation exponent) showed that it is not advisable to use cementation exponent (e) from other authors indiscriminately. Moreover, the application of the porosity values obtained by the ASTM tests allowed calculating a more suitable cementation exponent value for sandy sediments of the surf zone (between 1.48 and 1.79). Besides porosity, other geotechnical parameters, such as void ratio (e) and total density (rt ), were also differentiated by measuring the electrical resistivity of selected samples allowing to describe the geotechnical state of the sediment with higher confidence.Keywords: Electrical Resistivity; Coastal Engineering; Archie’s Equation; Porosity; Grain Size.RESUMO. A descrição geotécnica dos sedimentos arenosos da zona de arrebentação foi feita de duas maneiras: diretamente, através de ensaios geotécnicos padrão, propostos pela ASTM (Sociedade Americana de Testes e Materiais) e indiretamente, através de medidas de eletrorresistividade. A propriedade geotécnica escolhida para a descrição do sedimento foi a porosidade, por ser uma variável importante na caracterização das propriedades do solo. A estimativa indireta da porosidade através de medidas de resistividade foi baseada na equação de Archie. Entretanto, a principal dificuldade em generalizar esta equação é a determinação empírica do expoente de cimentação (m). Por esse motivo, os valores propostos por outros autores foram testados. Uma comparação dos valores de porosidade obtidos pelos dois métodos (direta e indiretamente, usando diferentes valores para o expoente de cimentação) mostrou que não é aconselhável usar expoente de cimentação (m) de outros autores indiscriminadamente. Além disso, a aplicação dos valores de porosidade obtidos pelos testes ASTM permitiu o cálculo de um valor para o expoente de cimentação mais adequado para sedimentos arenosos da zona de arrebentação (entre 1,48 e 1,79). Além da porosidade, outros parâmetros geotécnicos, como índice de vazios (e) e densidade total (rt ), também foram diferenciados pela medição da resistividade elétrica de amostras selecionadas, permitindo descrever o estado geotécnico do sedimento com maior confiança.Palavras-chave: Eletrorresistividade; Engenharia Costeira; Equação de Archie; Porosidade; Granulometria.
37
Moitinho, Maria da Luz Ribeiro y Cláudio Santos Ferreira. "Sedimentation in parasitological coproscopy". Revista do Instituto de Medicina Tropical de São Paulo 34, n.º 3 (junio de 1992): 255–58. http://dx.doi.org/10.1590/s0036-46651992000300013.
Texto completoResumen
A sedimentation technique is described, in which a fecal suspension is placed on top of an aqueous sucrose solution of specific gravity 1.015 g/cm³. Using 100 by 15 mm test tubes, duplicate gravity sedimentation experiments were made using homogenized fecal suspensions (single-columns) and fecal suspensions placed on top of clear columns (double-columns). Egg- and cyst-counts, and turbidity determinations were made in the sediments obtained after definite time intervals. Most Ascaris lumbricoides, Trichuris trichiura and Ancylostomidae eggs sedimented within 20 minutes in single - and between 30 and 60 minutes in double-columns. Giardia duodenalis cysts required longer periods to sediment in double - than in single-columns; after 180 minutes (the maximum period of observation), double-column sediments produced 60.0% of the counts of single-columns. Double-column sediments were consistently less turbid than single-column ones
38
Karem, Duha S., Zahra’a S. Al-Shamsi, Salah M. Saleh, Abbas H. Mohammed y Hamid T. Al-saad. "Environmental assessment of Heavy Metals in Sedi - ments of Tigris, Euphrates, Shatt Al-Arab rivers and northern west of Arabian Gulf." IOP Conference Series: Earth and Environmental Science 1300, n.º 1 (1 de febrero de 2024): 012026. http://dx.doi.org/10.1088/1755-1315/1300/1/012026.
Texto completoResumen
Abstract The most prevalent environmental contaminants found in sediments that suggest the presence of effluents from both home and industrial sources are thought to be heavy metals. The aim of this study was to assess the accumulation of heavy metals at surface sediment samples that were collected in order to measure the amounts of Cu, Zn, Pb, Cd, and Fe., to re-evaluate the environmental conditions and concentration of the analyzed elements in the sediment to detect any pollution of heavy metals in the studied area by using contamination factors (CF), Enrichment Factor (EF) and geo accumulation index (I-geo). To ascertain the connection between the sediment’s total organic carbon (TOC) level and heavy metal pollution, measurements were taken in addition of it. Using the inductively coupled plasma atomic emission spectrometer, studies were conducted., The mean values of the element in the sediments ranged as: Cu (13.45 μg/g at location 2 to 32.44 μg/g at location 9), Zn (20.76 μg/g at location 1 to 42.49 μg/g at location 10), Pb (9.78 μg/g at location 2 to 30.04 μg/g at location 9 and 10), Cd (7.89 μg/g at location 2 to 18.72 μg/g at location 7) and Fe (459.89 μg/g at location 1 to 833.83 μg/g at location 7) dry weight. The geochemical results show that the distribution and concentration of the heavy metals in the studied sediments is within the average concentration given for the FAO/WHO reported, and the sediment of the studied area is still free from pollution, except Pb and Cd in some local areas, which shows higher concentrations than those reported for world sediments.
39
Junakova, N., J. Junak y M. Balintova. "The effect of physicochemical properties of bottom sediments on nitrogen and phosphorus sorption". IOP Conference Series: Materials Science and Engineering 1252, n.º 1 (1 de septiembre de 2022): 012059. http://dx.doi.org/10.1088/1757-899x/1252/1/012059.
Texto completoResumen
Abstract River and reservoir bottom sediments are characterized by their physical and chemical properties, which affect the quality of water and deposited sediments in reservoirs. The grain composition of sediments is their fundamental property that determines the detachment, transport and sedimentation of sediments. In addition to understanding the dynamics of transport and distribution of particles in the watershed, the granularity is closely related to the mineral and chemical composition of the sediment and plays an important role in terms of its ability to bind contaminants. Other important property of sediment includes the specific surface area, which determines the nature of sediment surface reactions and influences ecosystem level, biological processes. This study investigates sediment properties, including physical properties such as grain-size distribution, specific surface area, organic matter and chemical composition, and their reflections on nitrogen and phosphorus adsorption by the sediments deposited in the small water reservoir. The results clearly indicate the dependence of the content of nutrients (nitrogen and phosphorus) in reservoir sediments on their grain size and specific surface area.
40
Navas-S., G. R., S. Zea y N. H. Campos. "FLUJO DE NITRÓGENO Y FÓSFORO EN LA INTERFASE AGUA-SEDIMENTO EN UNA LAGUNA COSTERA TROPICAL (CIÉNAGA GRANDE DE SANTA MARTA, CARIBE COLOMBIANO)". CICIMAR Oceánides 18, n.º 2 (31 de diciembre de 2003): 45. http://dx.doi.org/10.37543/oceanides.v18i2.5.
Texto completoResumen
. Para evaluar el papel del sedimento sobre la alta producción primaria de una laguna costera tropical, Ciénaga Grande de Santa Marta (Caribe, Colombia), se midió el flujo de nitrógeno y fósforo (inorgánico disuelto, particulado) en la interfase agua-sedimento. Entre 1996 y 1997 se incubaron núcleos de sedimento en el laboratorio y se ubicaron trampas de partículas en campo, en dos estaciones contrastadas por la influencia de aguas dulces y marinas. Los flujos tuvieron una alta variabilidad espacial y temporal pero no mostraron esquemas claros en su dirección e intensidad en relación con las características de los sedimentos o de la columna de agua de las dos estaciones. Esto evidencia una alta heterogeneidad en la naturaleza y actividad de los organismos responsables de los procesos biogeoquímicos. Los sedimentos liberaron en promedio al agua 1643 μmolNm-2d-1 de amonio y 1.3 μmolNm-2d-1 de nitrito, aportando a la columna el 1.90-3.41 % de lo requerido en la producción. En condiciones óxicas normales, el sedimento actuó como sifón del fósforo, absorbiendo en promedio 178 μmolPm-2d-1 disueltos y recibiendo 36277 μmolPm-2d-1 particulados. Pero el fósforo se mantiene en exceso en la columna, en parte, por liberación desde el sedimento en condiciones anóxicas durante florecimientos microalgales masivos. Flux of nitrogen and phosphorus at the water-sediment boundary in a tropical coastal lagoon (Ciénaga Grande de Santa Marta, Colombian Caribbean) To evaluate the role of the sediment in the high primary production of a tropical coastal lagoon, "Ciénaga Grande de Santa Marta" (Caribbean, Colombia), the flux of nitrogen and phosphorous (dissolved, inorganic, particulate) in the water-sediment boundary was measured. From 1996 to 1997 sediment cores were incubated in the laboratory and sediment traps were deployed in the field, in two sites contrasted by the influence of fresh and marine waters. The fluxes were spatially and temporally highly variable but did not show clear patterns in their direction and intensity in relation to the sediment or water column characteristics at the two sites. This evidences a high heterogeneity in the nature and activity of the organisms responsible of the biogeochemical processes. The sediments liberated to the water on average 1643 μmolNm-2d-1 of ammonium and 1.3 μmolNm-2d-1 of nitrite, offering 1.90-3.41 % of the amount required in production. In normal oxic conditions, the sediment acted as a phosphorous sink, absorbing on average 178 μmolPm-2d-1 dissolved and receiving 36277 μmolPm-2d-1 particulate. But the phosphorous is maintained in excess in the column, in part, due to its liberation from the sediment in anoxic conditions during massive algal blooms.
41
Navas-S., G. R., S. Zea y N. H. Campos. "FLUJO DE NITRÓGENO Y FÓSFORO EN LA INTERFASE AGUA-SEDIMENTO EN UNA LAGUNA COSTERA TROPICAL (CIÉNAGA GRANDE DE SANTA MARTA, CARIBE COLOMBIANO)". CICIMAR Oceánides 18, n.º 2 (31 de diciembre de 2003): 45. http://dx.doi.org/10.37543/oceanides.v18i2.5.
Texto completoResumen
. Para evaluar el papel del sedimento sobre la alta producción primaria de una laguna costera tropical, Ciénaga Grande de Santa Marta (Caribe, Colombia), se midió el flujo de nitrógeno y fósforo (inorgánico disuelto, particulado) en la interfase agua-sedimento. Entre 1996 y 1997 se incubaron núcleos de sedimento en el laboratorio y se ubicaron trampas de partículas en campo, en dos estaciones contrastadas por la influencia de aguas dulces y marinas. Los flujos tuvieron una alta variabilidad espacial y temporal pero no mostraron esquemas claros en su dirección e intensidad en relación con las características de los sedimentos o de la columna de agua de las dos estaciones. Esto evidencia una alta heterogeneidad en la naturaleza y actividad de los organismos responsables de los procesos biogeoquímicos. Los sedimentos liberaron en promedio al agua 1643 μmolNm-2d-1 de amonio y 1.3 μmolNm-2d-1 de nitrito, aportando a la columna el 1.90-3.41 % de lo requerido en la producción. En condiciones óxicas normales, el sedimento actuó como sifón del fósforo, absorbiendo en promedio 178 μmolPm-2d-1 disueltos y recibiendo 36277 μmolPm-2d-1 particulados. Pero el fósforo se mantiene en exceso en la columna, en parte, por liberación desde el sedimento en condiciones anóxicas durante florecimientos microalgales masivos. Flux of nitrogen and phosphorus at the water-sediment boundary in a tropical coastal lagoon (Ciénaga Grande de Santa Marta, Colombian Caribbean) To evaluate the role of the sediment in the high primary production of a tropical coastal lagoon, "Ciénaga Grande de Santa Marta" (Caribbean, Colombia), the flux of nitrogen and phosphorous (dissolved, inorganic, particulate) in the water-sediment boundary was measured. From 1996 to 1997 sediment cores were incubated in the laboratory and sediment traps were deployed in the field, in two sites contrasted by the influence of fresh and marine waters. The fluxes were spatially and temporally highly variable but did not show clear patterns in their direction and intensity in relation to the sediment or water column characteristics at the two sites. This evidences a high heterogeneity in the nature and activity of the organisms responsible of the biogeochemical processes. The sediments liberated to the water on average 1643 μmolNm-2d-1 of ammonium and 1.3 μmolNm-2d-1 of nitrite, offering 1.90-3.41 % of the amount required in production. In normal oxic conditions, the sediment acted as a phosphorous sink, absorbing on average 178 μmolPm-2d-1 dissolved and receiving 36277 μmolPm-2d-1 particulate. But the phosphorous is maintained in excess in the column, in part, due to its liberation from the sediment in anoxic conditions during massive algal blooms.
42
Sousa, Eduinetty Ceci P. M., Denis M. S. Abessa, Rachid Bauer R. F., Marcia R. Gasparro y Letícia P. Zaroni. "Ecotoxicological assessment of sediments from the Port of Santos and the disposal sites of dredged material". Brazilian Journal of Oceanography 55, n.º 2 (junio de 2007): 75–81. http://dx.doi.org/10.1590/s1679-87592007000200001.
Texto completoResumen
The dredging of sediments from the Santos Channel is necessary to allow the navigation of ships operating in the Port of Santos. The disposal sites for such sediments are situated on the coastal zone, in front of the Santos Bay. The present paper aimed at evaluating the toxicity of sediments collected at the Santos Channel and at the former and current sediment disposal sites. Whole sediment tests with amphipods and elutriate assays with sea-urchin embryos were used. The samples from the Santos Channel were considered the most toxic: all the sediment samples from this area showed toxicity. Moreover, some samples from both former and new sediment disposal sites exhibited toxicity. Therefore, results showed that sediments from the studied areas present evidences of degradation; however, further studies are required to determine relationships between toxicity and contamination. Results also suggested that the disposal of dredged sediments should be re-evaluated.
43
Wyness, Adam J., David M. Paterson, James E. V. Rimmer, Emma C. Defew, Marc I. Stutter y Lisa M. Avery. "Assessing Risk of E. coli Resuspension from Intertidal Estuarine Sediments: Implications for Water Quality". International Journal of Environmental Research and Public Health 16, n.º 18 (5 de septiembre de 2019): 3255. http://dx.doi.org/10.3390/ijerph16183255.
Texto completoResumen
Estuarine sediments are a reservoir for faecal bacteria, such as E. coli, where they reside at greater concentrations and for longer periods than in the overlying water. Faecal bacteria in sediments do not usually pose significant risk to human health until resuspended into the water column, where transmission routes to humans are facilitated. The erosion resistance and corresponding E. coli loading of intertidal estuarine sediments was monitored in two Scottish estuaries to identify sediments that posed a risk of resuspending large amounts of E. coli. In addition, models were constructed in an attempt to identify sediment characteristics leading to higher erosion resistance. Sediments that exhibited low erosion resistance and a high E. coli loading occurred in the upper- and mid-reaches of the estuaries where sediments had higher organic content and smaller particle sizes, and arose predominantly during winter and autumn, with some incidences during summer. Models using sediment characteristics explained 57.2% and 35.7% of sediment shear strength and surface stability variance respectively, with organic matter content and season being important factors for both. However large proportions of the variance remained unexplained. Sediments that posed a risk of resuspending high amounts of faecal bacteria could be characterised by season and sediment type, and this should be considered in the future modelling of bathing water quality.
44
Abed, Mahmood, Muthanna Al-Tharb y Ahmed Al-Taie. "Eco-Toxicological Risk Assessment of Heavy Metals and Polycyclic Aromatic Hydrocarbons in Sediments of Tigris River, Iraq". Iraqi Geological Journal 56, n.º 1C (31 de marzo de 2023): 62–73. http://dx.doi.org/10.46717/igj.56.1c.5ms-2023-3-16.
Texto completoResumen
The Tigris River is an important source for domestic, agricultural, industrial, fisheries, and even recreational activities. Therefore, environmental assessment of river sediments is vital, as sediments can be considered reservoirs of pollutants that are re-released into the water during floods or human activities. This research aimed to assess Tigris river sediments from Al Qayyarah to Al Tarmiyah. Nine samples of sediment were collected for analysing seven heavy metals and a metalloid (i.e. Cu, Cd, Cr, Pb, Zn, Ni, and As) and sixteen PAHs compounds. The concentrations of heavy metals Cd, Pb, As, Cr, and Ni in some locations have exceeded their background concentrations in the earth's crust. For assessing the contamination of sediments by metals, three indices, viz, SPI, TRI, and MERMQ were used. According to the results of the three indices, Al Qayyarah and Baiji sites were more contaminated than other sites. This may be attributed to anthropogenic activities represented by the petroleum industry which enriches sediments with metals. Also, three indices for evaluating the environmental risk of PAHs, i.e., MERMQ, SQGQ, and RQ, were used. Based on Mean ERM Quotient values, the toxicity probability of PAHs in sediments ranged from 49% at Al Qayyarah and Baiji to 21% and 9% at other sites. The SQGS index values showed that Al Qayyarah and Baiji sites were highly affected by PAHs contaminants. According to the Risk Quotient (RQ) values of the sum PAHs, the environmental risk of river sediments ranged from low to moderate.
45
Pujate, Agnese, Karina Stankevica, Laimdota Kalnina, Maris Klavins, Aija Cerina, Anda Drucka y Kristaps Kiziks. "Records of the anthropogenic influence on different origin lake sediments of Latvia". Baltica 28, n.º 2 (11 de diciembre de 2015): 135–50. http://dx.doi.org/10.5200/baltica.2015.28.12.
Texto completoResumen
Sediments in lakes have formed under the conditions of sensitive ecosystem functions as archives of micro- and macrocomponents. Besides others, lake sediments preserve palaeobotanical and chemical evidence reflecting environmental changes. During the last centuries, sediment composition has been influenced also by inconsistent urban and industrial developments. This paper represents the results of chemical and palaeobotanical signatures in the sediments from four lakes of different origin: Lake Lilaste, Lake Velnezers, Lake Engure, and Lake Vevers. The data were compared with the results from sediment composition analysis obtained by Loss on Ignition and chemical methods taking into account changes in plant macroremains. The studies of lake sediments revealed that human impact is recognisable in the upper sediment layer of all investigated sites, but at different depth from sediment surface. The most recognisable traces of anthropogenic influence can be attributed to the sharp increase of the amount of lead (Pb) and number of plant macroremains in analysed lake sediments.
46
Li, Nan, Ziyang Fan, Haoran Ma, Shuai Jia, Jingyu Kan, Changyu Sun y Shun Liu. "Permeability of Hydrate-Bearing Sediment Formed from CO2-N2 Mixture". Journal of Marine Science and Engineering 11, n.º 2 (8 de febrero de 2023): 376. http://dx.doi.org/10.3390/jmse11020376.
Texto completoResumen
CO2-N2-mixture injection can be used for the exploitation and reformation of natural gas hydrate reservoirs. The permeability evolution of sediments in the presence of CO2-N2 hydrate is very important. In current permeability tests, hydrate-bearing sediment formed from CO2-N2 gas mixture is rarely involved. In this work, hydrate-bearing sediment was formed from CO2-N2 mixtures, and a constant flow method was employed to measure the permeability of the hydrate-bearing sediments. The effects of CO2 mole fraction and hydrate saturation on the permeability were investigated. The results show that gas composition is the key factor affecting hydrate formation. Hydrate saturation increases with increasing CO2 mole fraction in the gas mixture. The presence of hydrate formed from a CO2-N2 mixture leads to a sharp permeability reduction. The higher the fraction of CO2 in the injected gas mixture, the lower the sediment’s permeability. Our measured permeability data were also compared with and fitted to prediction models. The pore-filling model underestimates the permeability of hydrate-bearing sediments formed from a CO2-N2 gas mixture. The fitted hydrate saturation index in the Masuda model is 15.35, slightly higher than the general values, which means that the formed hydrates tend to occupy the pore center, and even block the pore throat.
47
Tudurí, Adriana, Leandro Bergamino, Roberto Violante, José Luis Cavallotto y Felipe García-Rodríguez. "SPATIAL AND TEMPORAL VARIATION IN THE PRESENT AND HISTORICAL SEDIMENTARY ORGANIC MATTER WITHIN THE RÍO DE LA PLATA ESTUARY (SOUTH AMERICA) IN RELATION TO THE SALINITY/TURBIDITY GRADIENT / VARIAÇÃO ESPACIAL E TEMPORAL PRESENTE E HISTÓRICA DA MATÉRIA ORGÂNICA SEDIMENTAR NO ESTUÁRIO DO RÍO DE LA PLATA (AMÉRICA DO SUL) EM RELAÇÃO AO GRADIENTE DE SALINIDADE / TURBIDEZ". Journal of Sedimentary Environments 3, n.º 4 (23 de diciembre de 2018): 265–79. http://dx.doi.org/10.12957/jse.2018.39152.
Texto completoResumen
The aim of this study is to examine sedimentary organic matter sources, spatial distribution and temporal variability in a large estuarine system, the Río de la Plata estuary (South America). For this purpose, this work integrates recent and historical carbon and nitrogen isotopes (δ13C, δ15N), total organic carbon, total nitrogen, C/N ratios and sediment grain size analyses along the Río de la Plata estuary. Principal component analysis based on biogeochemical variables and salinity revealed two main biogeochemical contrasting zones, corresponding to the upper and the lower estuary. Such zones are derived from the density gradient observed at the maximum turbidity zone acting as a physical barrier by trapping fine sediments and controlling primary productivity. As a consequence, sedimentary total organic carbon and total nitrogen increase from upper reaches towards lower reaches to attain maximum values under the turbidity gradient due to the presence of fine sediments. On the other hand, C/N ratios display an opposite trend, with higher values in the upper reaches due to a higher influence of continental organic matter. Moreover, Stable Isotope Analysis in R (SIAR) based on δ13C and δ15N reveals that the main organic matter source to the sediment appears to be the continental particulate organic matter and the estimated percentages of terrestrial allochthonous contribution (C3 plants) indicated a decreased contribution towards the lower reaches. The paleoenvironmental analysis shows a change in the sedimentary organic matter composition since 1970 associated to an increased influence of terrestrial organic matter. This trend is related to an increase in the Paraná River flow, which in turn is related to climatic variability (i.e., the polarity change of the Pacific Decadal Oscillation). ResumoO objetivo deste estudo é estimar fontes de matéria orgânica sedimentar, distribuição espacial e variabilidade temporal num grande sistema estuarino, o estuário do Río de la Plata (América do Sul). Este trabalho integra dados atuais e históricos de isótopos de carbono e nitrogênio (δ13C, δ15N), carbono orgânico total, nitrogênio total, relação C/N e granulometria do sedimento ao longo do estuário do Río de la Plata. A análise de componentes principais baseada em variáveis biogeoquímicas e salinidade revelou duas zonas biogeoquímicas contrastantes, correspondentes ao estuário superior e inferior. Tais zonas são definidas por diferenças no gradiente de densidade na zona de turbidez máxima, o qual atua como uma barreira física, causando o aprisionamento de sedimentos finos e influenciando a produtividade primária. Como conseqüência, o carbono orgânico total sedimentar e o nitrogênio total aumentam dos trechos superiores para os trechos inferiores atingindo valores máximos sob o gradiente de turbidez devido à presença de sedimentos finos. Por outro lado, a razão C/N exibe uma tendência oposta, atingindo valores mais elevados no estuário superior devido a uma maior influência da matéria orgânica continental. Os resultados isotópicos de δ13C e δ15N sugerem que a principal fonte de matéria orgânica para o sedimento é a matéria orgânica particulada continental. A contribuição alóctone terrestre (plantas C3) diminui no estuário inferior. A análise paleoambiental mostra uma mudança na composição da matéria orgânica sedimentar a partir de 1970, causada pelo aumento do fornecimento da matéria orgânica terrestre. Essa tendência está relacionada a um aumento no fluxo do Rio Paraná, na sequência de alterações climáticas relacionadas com a mudança de polaridade da Oscilação Decadal do Pacífico.
48
Abessa, Denis, Thaisa Marques Vicente, Lucas Buruaem Moreira, Lucas Gonçalves Morais, Ana Carolina Feitosa Cruz, Mirella Massonetto, Bruno Galvão de Campos et al. "Assessing the sediment quality of the Laje de Santos marine state park and other marine protected areas of the central coast of São Paulo (Brazil)". Brazilian Journal of Oceanography 65, n.º 4 (diciembre de 2017): 532–48. http://dx.doi.org/10.1590/s1679-87592017128606504.
Texto completoResumen
Abstract In this study, the quality of sediments from three Marine Protected Areas (MPAs) located on the coast of São Paulo (Laje de Santos Marine State Park - PEMLS; Xixova-Japui State Park - XJSP; and Central Coast Marine Protection Area - APAMLC) was assessed. Four sampling surveys were conducted (September/October 2013; January 2014; July 2014; January 2015). Sediment samples were collected at10 sites, distributed along the 3 MPAs. Samples were analyzed for sediment texture, total organic carbon, CaCO3, metals, aliphatic and polycyclic aromatic hydrocarbons, and for whole-sediment and sediment-water interface toxicities. Principal component analysis (PCA) was used to integrate data. Most of the sediments exhibited low concentrations of chemicals, with the exception of those from P2 (APAMLC) where moderate levels of contaminants were detected. Sediments from P7 and P9 (PEMLS) occasionally showed signs of petroleum hydrocarbons. The other sediments showed no relevant contamination but presented variable toxicity, especially those of bioclastic composition. The PCA indicated a contribution of the sediment properties to the toxicities, especially the CaCO3. In bioclastic sediments, toxicity might be due to physical causes by or any indirect factor such as the presence of ammonia. It was concluded that both natural and anthropic factors are causing toxicity in sediments from the MPAs studied.
49
Ashey, Jill, Hailey McKelvie, John Freeman, Polina Shpilker, Lauren H. Zane, Danielle M. Becker, Lenore Cowen et al. "Characterizing transcriptomic responses to sediment stress across location and morphology in reef-building corals". PeerJ 12 (30 de enero de 2024): e16654. http://dx.doi.org/10.7717/peerj.16654.
Texto completoResumen
Anthropogenic activities increase sediment suspended in the water column and deposition on reefs can be largely dependent on colony morphology. Massive and plating corals have a high capacity to trap sediments, and active removal mechanisms can be energetically costly. Branching corals trap less sediment but are more susceptible to light limitation caused by suspended sediment. Despite deleterious effects of sediments on corals, few studies have examined the molecular response of corals with different morphological characteristics to sediment stress. To address this knowledge gap, this study assessed the transcriptomic responses of branching and massive corals in Florida and Hawai‘i to varying levels of sediment exposure. Gene expression analysis revealed a molecular responsiveness to sediments across species and sites. Differential Gene Expression followed by Gene Ontology (GO) enrichment analysis identified that branching corals had the largest transcriptomic response to sediments, in developmental processes and metabolism, while significantly enriched GO terms were highly variable between massive corals, despite similar morphologies. Comparison of DEGs within orthogroups revealed that while all corals had DEGs in response to sediment, there was not a concerted gene set response by morphology or location. These findings illuminate the species specificity and genetic basis underlying coral susceptibility to sediments.
50
Haltia, E. M. y N. R. Nowaczyk. "Magnetostratigraphy of sediments from Lake El'gygytgyn ICDP Site 5011-1: paleomagnetic age constraints for the longest paleoclimate record from the continental Arctic". Climate of the Past 10, n.º 2 (26 de marzo de 2014): 623–42. http://dx.doi.org/10.5194/cp-10-623-2014.
Texto completoResumen
Abstract. Paleomagnetic measurements were performed on sediments drilled from ICDP Site 5011-1 in Lake El'gygytgyn (67°30' N, 172°05' E) located in Far East Russian Arctic. The lake partly fills a crater formed by a meteorite impact 3.58 ± 0.04 Ma ago. Sediments from three parallel cores (5011-1A, 5011-1B and 5011-1C), recovered from the middle part of the lake, yield a total of 355 m of sediment. Sediments are characterized by a variable lithology, where intervals of homogenous and laminated sediments alternate, and mass movement deposits occur frequently along the sediment profile. Mineral magnetic investigation made on sediments enclosed in core catchers suggests that magnetic carrier in these sediments is partly maghemitized Ti-rich pseudo-single domain magnetite. Its detrital origin can be shown by mineral magnetic measurements and SEM-EDS analyses performed on mini-sized cylindrical rock samples, polished rock sections and creek sediments. The intensity of the natural remanent magnetization in the sediments is high with a range from about 1 to 1000 mA m−1. Most of the sediments carry a stable magnetization interpreted as primary depositional remanent magnetization. Characteristic inclination data show alternating intervals of steep positive and negative inclinations that are used to assign magnetic polarity to the lake sediment profile. This is a rather straightforward procedure owing to the mainly high quality of data. The Matuyama/Gauss (M/G) (2.608 Ma) and Brunhes/Matuyama (B/M) (0.780 Ma) reversals were recognized in the sediments. The Mammoth and Kaena reversed subchrons were identified during the Gauss chron, and the Olduvai and Jaramillo normal subchrons as well as the Réunion and Cobb Mountain cryptochrons were identified during the Matuyama chron. Sediments also provide a record of the Olduvai precursor and Intra-Jaramillo geomagnetic excursions. Sediment deposition rate is highest at the base of the sequence laid down in the early Gauss chron, when the deposition rate is approximately 44 cm kyr−1. Sediment deposition decelerates upcore and it is an order of magnitude lower during the Brunhes chron in comparison with the early Gauss chron. Decrease in sediment deposition in the late Pliocene probably relates to atmospheric and oceanic reorganization heralding the onset of Quaternary climate change. The high-quality magnetostratigraphy reconstructed from Lake El'gygytgyn sediments provides 12 first-order tie points to pin down the age of the longest paleoclimate record from the continental Arctic.