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Frenette, M., e P. Y. Julien. "LAVSED-I — Un modèle pour prédire l'érosion des bassins et le transfert de sédiments fins dans les cours d'eau nordiques". Canadian Journal of Civil Engineering 13, n.º 2 (1 de abril de 1986): 150–61. http://dx.doi.org/10.1139/l86-023.
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Computer modeling techniques are used for predicting soil losses from overland flow and subsequent suspended sediment yield from large watersheds. The model LAVSED-I (LAVal SEDidentological model No. 1) is based on the universal soil-loss equation of Wischmeier and Smith and the equation of Kiline and Richardson. The model subdivides the watershed into square units varying in size from 0.3 to 3000 km2 and the computational procedure is subdivided in four components: precipitation, physical characteristics of watersheds, erosion/sedimentation, and land use. This paper describes the operational development and the application of the model to a prototype-scale watershed. A map for the annual soil loss is presented for the Chaudière watershed (area = 5830 km2). Results of mapping compared with the sediment yield observed are shown in the paper.
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Subardjo, Petrus, Agus Anugroho Dwi Suryoputro e Ibnu Praktikto. "Sebaran Sedimen Tersuspensi di Perairan Teluk Awur Jepara menggunakan Citra Landsat 8". Buletin Oseanografi Marina 9, n.º 1 (24 de abril de 2020): 77–82. http://dx.doi.org/10.14710/buloma.v9i1.29111.
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Sedimen tersuspensi dianggap sebagai sedimen yang didistribusikan oleh arus laut. Arus sepanjang pantai (longshore current) berperan besar terhadap proses perpindahan sedimen di perairan. Gelombang laut yang yang membentuk sudut terhadap garis pantai menyebabkan arus sepanjang pantai Transpor sedimen yang disebabkan oleh arus sepanjang panti sering menimbulkan permasalahan erosi pantai dan pendangkalan perairan. Perairan Teluk Awur memiliki bentuk teluk dan tanjung yang memungkinkan terjadinya arus sepanjang pantai. Potensi adanya proses erosi dan sedimentasi di perairan Teluk Awur membuat pentingnya kajian mengenai pola sebaran sedimen tersuspensi. Penelitian ini mampu menjelaskan tentang pola sebaran sedimen tersuspensi di perairan Teluk Awur, Kecamatan Tahunan, Kabupaten Jepara. Metode yang digunakan untuk penentuan sedimen tersuspensi menggunakan pengindraan jauh dan data yang digunakan yaitu citra satelit landsat-8. Kandungan sedimen tersuspensi tertinggi berada di Desa Teluk Awur dan Desa Demaan. Kandungan tertinggi sebesar ± 67,54 mg/L dan semakin menjauhi pantai konsentrasi menurun. Tingginya kadungan sedimen tersuspensi dipengaruhi oleh proses mixing dan intensitas curah hujan. Suspended sediments are considered as sediments distributed by ocean currents. Current along the coast (longshore current) plays a major role in the process of transfer of sediment in the waters. Sea waves that form angles to the coastline cause currents along the coast Sediment transport caused by currents along the orphanage often cause erosion and coastal silting problems. The waters of Teluk Awur have the shape of bays and headlands which allow currents along the coast. The potential for erosion and sedimentation in the Awur Bay waters makes it important to study the pattern of suspended sediment distribution. This research is able to explain the pattern of suspended sediment distribution in Awur Bay waters, Annual District, Jepara Regency. The method used to determine suspended sediment uses remote sensing and the data used are Landsat-8 satellite imagery. The highest suspended sediment content was in Teluk Awur Village and Demaan Village. The highest content of ± 67.54 mg / L and increasingly away from the beach decreased concentration. The high suspended sediment content is influenced by the mixing process and the intensity of rainfall.
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Gude, Martin, Christer Jonasson, Susanne Dietrich e Dieter Scherer. "Assessment of Variability in Fluvial Sediment Transfers in Kärkevagge (N-Sweden) during the last 50 Years". Hydrology Research 31, n.º 4-5 (1 de agosto de 2000): 373–84. http://dx.doi.org/10.2166/nh.2000.0022.
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The Kärkevagge (Abisko area, Northern Sweden) represents a focus research basin concerning geomorphic processes and sediment budgets for the last 50 years. Different geomorphic process studies provide comparative data sets concerning climate variability implications on sediment transfers. While monitoring of sediment transfers is discontinuous with respect to study periods and methods, a detailed chronology of high-magnitude events with significant sediment displacement is available. In continuation of these studies, investigations in 1995 and 1998 as part of the MOSAIC project (Modelling Of Snowmelt And Its Consequences) are concentrating on snowmelt-induced slushflow initiation and transports of sediments in several small headwater catchments during the snowmelt period. Main purpose of the investigations is to characterize different catchment sections in terms of their hydrologic and sedimentologic contribution to the total fluvial and sediment budget of the basin, and to evaluate their specific sensitivity related to changes in atmospheric boundary conditions. By means of these data sets, the temporal variability of fluvial sediment transfers can be assessed over different time scales. The paper focuses on a description of different sections in the fluvial sediment transfer system in Kärkevagge. By comparing results from recent field investigations with data from former studies, the significance of rainfall- and snowmelt-triggered events for sediment transfers is evaluated.
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Cutter, Leah, Kevin R. Sowers e Harold D. May. "Microbial Dechlorination of 2,3,5,6-Tetrachlorobiphenyl under Anaerobic Conditions in the Absence of Soil or Sediment". Applied and Environmental Microbiology 64, n.º 8 (1 de agosto de 1998): 2966–69. http://dx.doi.org/10.1128/aem.64.8.2966-2969.1998.
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ABSTRACT Bacterial enrichment cultures developed with Baltimore Harbor (BH) sediments were found to reductively dechlorinate 2,3,5,6-tetrachlorobiphenyl (2,3,5,6-CB) when incubated in a minimal estuarine medium containing short-chain fatty acids under anaerobic conditions with and without the addition of sediment. Primary enrichment cultures formed both meta and orthodechlorination products from 2,3,5,6-CB. The lag time preceding dechlorination decreased from 30 to less than 20 days as the cultures were sequentially transferred into estuarine medium containing dried, sterile BH sediment. In addition, only ortho dechlorination was observed following transfer of the cultures. Sequential transfer into medium without added sediment also resulted in the development of a strict ortho-dechlorinating culture following a lag of more than 100 days. Upon further transfer into the minimal medium without sediment, the lag time decreased to less than 50 days. At this stage all cultures, regardless of the presence of sediment, would produce 2,3,5-CB and 3,5-CB from 2,3,5,6-CB. The strictortho-dechlorinating activity in the sediment-free cultures has remained stable for more than 1 year through several transfers. These results reveal that the classical microbial enrichment technique using a minimal medium with a single polychlorinated biphenyl (PCB) congener selected for ortho dechlorination of 2,3,5,6-CB. Furthermore, this is the first report of sustained anaerobic PCB dechlorination in the complete absence of soil or sediment.
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Cogez, Antoine, Frédéric Herman, Éric Pelt, Thierry Reuschlé, Gilles Morvan, Christopher M. Darvill, Kevin P. Norton, Marcus Christl, Lena Märki e François Chabaux. "U–Th and <sup>10</sup>Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia". Earth Surface Dynamics 6, n.º 1 (5 de março de 2018): 121–40. http://dx.doi.org/10.5194/esurf-6-121-2018.
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Abstract. The estimation of sediment transfer times remains a challenge to our understanding of sediment budgets and the relationships between erosion and climate. Uranium (U) and thorium (Th) isotope disequilibria offer a means of more robustly constraining sediment transfer times. Here, we present new uranium and thorium disequilibrium data for a series of nested moraines around Lago Buenos Aires in Argentine Patagonia. The glacial chronology for the area is constrained using in situ cosmogenic 10Be analysis of glacial outwash. Sediment transfer times within the periglacial domain were estimated by comparing the deposition ages of moraines to the theoretical age of sediment production, i.e., the comminution age inferred from U disequilibrium data and recoil loss factor estimates. Our data show first that the classical comminution age approach must include weathering processes accounted for by measuring Th disequilibrium. Second, our combined data suggest that the pre-deposition history of the moraine sediments is not negligible, as evidenced by the large disequilibrium of the youngest moraines despite the equilibrium of the corresponding glacial flour. Monte Carlo simulations suggest that weathering was more intense before the deposition of the moraines and that the transfer time of the fine sediments to the moraines was on the order of 100–200 kyr. Long transfer times could result from a combination of long sediment residence times in the proglacial lake (recurrence time of a glacial cycle) and the remobilization of sediments from moraines deposited during previous glacial cycles. 10Be data suggest that some glacial cycles are absent from the preserved moraine record (seemingly every second cycle), supporting a model of reworking moraines and/or fluctuations in the extent of glacial advances. The chronological pattern is consistent with the U–Th disequilibrium data and the 100–200 kyr transfer time. This long transfer time raises the question of the proportion of freshly eroded sediments that escape (or not) the proglacial environments during glacial periods.
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Burd, Brenda J., Christopher J. Lowe e Carmen Morales-Caselles. "Uptake of PCBs into sediment dwellers and trophic transfer in relation to sediment conditions in the Salish Sea". FACETS 7 (1 de janeiro de 2022): 936–65. http://dx.doi.org/10.1139/facets-2021-0032.
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We examined uptake of polychlorinated biphenyls (PCBs) into various marine sediment feeders relative to physical and geochemical factors and transfer to higher trophic levels. PCBs exceeding Canadian Council Ministers of the Environment Guidelines by 6–55× were found in industrialized harbours and some near-outfall sediments, indicating ongoing land input. Sediment PCBs were correlated with organic flux and content. Tissue PCBs were >10× sediment PCBs in all samples and highest in Victoria Harbour infauna, suggesting considerable uptake from these extremely contaminated, organically enriched, chronically disturbed sediments. Sediment PCBs were the primary predictor of tissue lipid PCBs followed by %fines. This results in generally higher tissue PCBs in more depositional regions. The lipid/sediment PCBs (uptake rate) declined with increasing sediment PCBs, acid volatile sulfides and benthos biomass turnover. PCB homologue composition did not change with uptake from sediments or at higher trophic levels, suggesting minimal metabolization in tissues. Trophic bio-magnification occurs since lipid PCBs were 2–100× higher in seal blubber than sediment feeders. PCBs were compared with polybrominated diphenyl ethers (PBDEs) for the same samples. PCBs were highest in industrialized harbours, whereas PBDEs were elevated in harbours but highest near wastewater discharges. This reflects differences in usage history, sediment dynamics, and affinities. PCBs appear to be more bio-accumulative and persistent at higher trophic levels than PBDEs.
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Hull, Erin A., Rebekah R. Stiling, Marco Barajas, Rebecca B. Neumann, Julian D. Olden e James E. Gawel. "Littoral sediment arsenic concentrations predict arsenic trophic transfer and human health risk in contaminated lakes". PLOS ONE 18, n.º 10 (19 de outubro de 2023): e0293214. http://dx.doi.org/10.1371/journal.pone.0293214.
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Lake sediments store metal contaminants from historic pesticide and herbicide use and mining operations. Historical regional smelter operations in the Puget Sound lowlands have resulted in arsenic concentrations exceeding 200 μg As g-1 in urban lake sediments. Prior research has elucidated how sediment oxygen demand, warmer sediment temperatures, and alternating stratification and convective mixing in shallow lakes results in higher concentrations of arsenic in aquatic organisms when compared to deeper, seasonally stratified lakes with similar levels of arsenic pollution in profundal sediments. In this study we examine the trophic pathways for arsenic transfer through the aquatic food web of urban lakes in the Puget Sound lowlands, measuring C and N isotopes–to determine resource usage and trophic level–and total and inorganic arsenic in primary producers and primary and secondary consumers. Our results show higher levels of arsenic in periphyton than in other primary producers, and higher concentrations in snails than zooplankton or insect macroinvertebrates. In shallow lakes arsenic concentrations in littoral sediment are similar to deep profundal sediments due to arsenic remobilization, mixing, and redeposition, resulting in direct arsenic exposure to littoral benthic organisms such as periphyton and snails. The influence of littoral sediment on determining arsenic trophic transfer is evidenced by our results which show significant correlations between total arsenic in littoral sediment and total arsenic in periphyton, phytoplankton, zooplankton, snails, and fish across multiple lakes. We also found a consistent relationship between percent inorganic arsenic and trophic level (determined by δ15N) in lakes with different depths and mixing regimes. Cumulatively, these results combine to provide a strong empirical relationship between littoral sediment arsenic levels and inorganic arsenic in edible species that can be used to screen lakes for potential human health risk using an easy, inexpensive sampling and analysis method.
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Brydon, Julia, Iwata Oh, Julie Wilson, Ken Hall e Hans Schreier. "Evaluation of Mitigation Methods to Manage Contaminant Transfer in Urban Watersheds". Water Quality Research Journal 44, n.º 1 (1 de fevereiro de 2009): 1–15. http://dx.doi.org/10.2166/wqrj.2009.002.
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Abstract Three case studies on trace metal contamination in urban stormwater are presented from the Greater Vancouver area of British Columbia. In the first case study, the spatial and temporal variability in trace metals in sediments were determined in the completely urbanized Brunette watershed. A natural lake in the middle of the watershed acts as a sediment detention system, and an analysis of the sediment core showed the historic accumulation of metal and selective organic contaminants in sediments since the early 1800s. Suspended sediments transported during storm events showed significantly higher concentrations of trace metals than bedload sediments, and the largest proportion of the geochemically active metals was found to be associated with the organic-sulphur-based fraction. Benthic organism survival tests showed mixed results with lower survival and growth in urban sediments than in control sediments from a forested watershed. In the second case study, significant correlations were obtained between percent impervious cover and trace metal concentrations in 28 subwatersheds with various degrees of urbanization. It is shown that imperviousness combined with traffic density can significantly improve the prediction of metal contamination in highly urbanized watersheds. In the third case study five urban stormwater detention systems were examined over one year to determine how effective these systems were in removing metal contamination. The results were highly variable depending on a wide range of physical conditions, land use activities, traffic volume, and detention system designs. The range of total metal detention was between −15 to +72% for copper (Cu), lead (Pb), and zinc (Zn), while iron (Fe) and manganese (Mn) retention was generally poor. Labile Zn was more effectively retained in four of the five ponds, and a significant relationship was found between percent imperviousness, traffic volume, and Zn concentrations in water, sediment, and labile form.
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Searcy, Kristin E., Aaron I. Packman, Edward R. Atwill e Thomas Harter. "Deposition of Cryptosporidium Oocysts in Streambeds". Applied and Environmental Microbiology 72, n.º 3 (março de 2006): 1810–16. http://dx.doi.org/10.1128/aem.72.3.1810-1816.2006.
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ABSTRACT The transfer of Cryptosporidium oocysts from the surface water to the sediment beds of streams and rivers influences their migration in surface waters. We used controlled laboratory flume experiments to investigate the deposition of suspended Cryptosporidium parvum oocysts in streambeds. The experimental results demonstrate that hydrodynamic interactions between an overlying flow and a sediment bed cause oocysts to accumulate in the sediments and reduce their concentrations in the surface water. The association of C. parvum with other suspended sediments increased both the oocysts' effective settling velocity and the rate at which oocysts were transferred to the sediment bed. A model for the stream-subsurface exchange of colloidal particles, including physical transport and physicochemical interactions with sediment grains, accurately represented the deposition of both free C. parvum oocysts and oocysts that were attached to suspended sediments. We believe that these pathogen-sediment interactions play an important role in regulating the concentrations of Cryptosporidium in streams and rivers and should be taken into consideration when predicting the fate of pathogens in the environment.
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Lau, Maximilian P., Michael Sander, Jörg Gelbrecht e Michael Hupfer. "Spatiotemporal redox dynamics in a freshwater lake sediment under alternating oxygen availabilities: combined analyses of dissolved and particulate electron acceptors". Environmental Chemistry 13, n.º 5 (2016): 826. http://dx.doi.org/10.1071/en15217.
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Environmental contextAt sediment surfaces, the availability of oxygen is controlled by its downward transport from the water surface and its consumption in microbial metabolism. Microorganisms can also consume substances other than oxygen to dispose of the surplus charge that is generated during microbial metabolism. We investigate the complex dynamics of these other substances when the oxygen availability fluctuates, and thereby contribute to the mechanistic understanding of oxygen-consuming processes in aquatic environments. AbstractBenthic mineralisation in lakes largely controls the availability of oxygen in the water column above the sediment. In stratified lakes with anoxic hypolimnetic waters, mineralisation proceeds by anaerobic respiration using terminal electron acceptors (TEAs) other than O2. In past work, hypolimnetic oxygen consumption has been estimated from vertical concentration profiles of redox-active dissolved species in the water column and the underlying sediment. Electron transfer to and from particulate mineral and organic phases in the sediments was, however, not accounted for, mainly because of methodological constraints. In this work we use an electrochemical approach, mediated electrochemical analysis, to directly quantify changes in the redox states of particulate geochemical phases in a lake sediment. In mesocosm incubations, sediments were subjected to shifting oxygen availability similar to conditions during and after lake overturn events. The temporal redox dynamics of both dissolved and particulate phases in sediments were monitored at a high spatial resolution. We used a combination of experimental and modelling approaches to couple the observed changes in the redox state of dissolved and particulate species in the sediment to the oxygen turnover in the overlying water column. For the studied freshwater sediment, the amount of O2 consumed during the re-oxidation of these phases in the top 21mm of the sediment after switching from hypoxic to oxic conditions corresponded to ~50% of the total sediment oxygen consumption that was estimated from in-lake measurements after the onset of summer stratification. We found that solid phases in the sediments play a more profound role in electron accepting processes than previously considered. Based on these results, we propose that the herein presented analytical method offers the possibility to constrain parameters in theoretical models that simulate benthic redox dynamics including the electron transfer to and from geochemical phases in the sediments.
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Moisejenkova, Anastasija, Nikolaj Tarasiuk e Aloyzas Girgždys. "PECULIARITIES OF THE THERMAL REGIME OF THE SURFACE SEDIMENTS IN LAKE TAPELIAI". Mokslas - Lietuvos ateitis 2, n.º 5 (31 de outubro de 2010): 66–70. http://dx.doi.org/10.3846/mla.2010.093.
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The article discusses the process of heat transfer in the water sediment system having an impact on the input of nutrients and mineral substances from sediments to the bottom water layer. Therefore, conductivity sharply increases on the surface of bottom sediments and reaches more than 400 μS∙cm–1. The heat exchange process is analyzed in Lake Tapeliai classified as a “temporally warm” lake (see K. Kilkus). The paper defines heat transfer from bottom sediments to water applying the convection method and describes isotherm deepening of 4 ºC into sediments. The temperature of surface sediments in Lake Tapeliai was 3,3–3,9 ºC in 2007–2009, whereas the isotherm of 4 ºC slid 20–30 cm deeper to bottom sediments.
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Hill, Liesl, e Sebastian Jooste. "The effects of contaminated sediments of the Blesbok Spruit near Witbank on water quality and the toxicity thereof to Daphnia pulex". Water Science and Technology 39, n.º 10-11 (1 de maio de 1999): 173–76. http://dx.doi.org/10.2166/wst.1999.0650.
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With the increasing focus on environmental issues, the objective of this study is to evaluate the potential impact of contaminated sediments of the Blesbok Spruit near Witbank - which receives acid mine drainage (AMD) inter alia - on biota. Direct transfer of chemicals from sediments to organisms is considered to be a major route of exposure for many species, and therefore focusing attention on sediment contamination and highlighting the fact that sediments are an important resource. Acute toxicity tests were performed on Daphnia pulex using both extracted sediment interstitial water and surface water. Chemical analyses were also performed on the sediment, interstitial water and surface water samples. The toxicity results suggest that metal toxicity adds significantly to the toxicity of the stream water which is enhanced by the effect of pH. The pH of the stream and interstitial water was consistently below 4.5.
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Gemilang, Wisnu Arya, Ulung Jantama Wisha e Guntur Adhi Rahmawan. "PARTICLE SIZE CHARACTERISTICS OF RIVERBED SEDIMENTS TRANSPORTED BY TIDAL BORE ‘BONO’ IN KAMPAR ESTUARY, RIAU-INDONESIA". Marine Research in Indonesia 43, n.º 1 (30 de junho de 2018): 25–35. http://dx.doi.org/10.14203/mri.v43i1.293.
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The presence of tidal bore in the Kampar River (locally known as ‘bono’) may influence sedimentation in the Kampar River and its estuary. Understanding sedimentation mechanisms (e.g., erosion, deposition) is important to communities along the Kampar River, which can be studied by analyzing characteristics of grain size distribution. Here, we study riverbed sediment samples collected from 17 stations using an Ekman grab sampler, accompanied by bathymetry and acoustic Doppler current profiler (ADCP) measurements. Grain size data show that the sediments are coarser upstream and gradually finer downstream. Silty sands are predominant in the upstream section of the river, sands in its river body and sandy silts in the downstream. The results indicate the influence of undular bores on grain size characteristics. We also found that the propagation of bono and Kampar River’s funnelshaped morphology cause intense scouring events of riverbed sediments. Sortation values that range between 0.332.14 suggest unstable currents that result in randomly deposited sediments. The sediment mass transfer per area is positively towards downstream at the low tidal condition. However, after the passage of the bores, the sediment mass transfer area becomes negatively towards upstream.
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Schrott, L., J. Götz, M. Geilhausen e D. Morche. "Spatial and temporal variability of sediment transfer and storage in an Alpine basin (Reintal valley, Bavarian Alps, Gemany)". Geographica Helvetica 61, n.º 3 (30 de setembro de 2006): 191–200. http://dx.doi.org/10.5194/gh-61-191-2006.
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Abstract. This paper focuses in particular on clastic sediment fluxes on talus slopes. Using orthophoto interpretation, field measurements and GIS-techniques, a quantification of areas and volumes of active sediment transfer related to specific landform units was achieved for different spatial scales. Closer investigation of a single landform complex, more specifically a talus sheet/ debris cone-complex, brought to light that remobilisation can overbalance sediment input by a factor of 57. This could be an indication of what may be expected in the whole catchment. At present. approximately 9% of the research area (3 km2), comprising talus slopes and valley bottom, is characterised by sediment transfer mainly through gravilational and fluvial processes. A comparison of the vast volumes (117.174 m3) derived from these active areas of recent sediment transfer and the volume of the entire valley fill (0.07 km3) indicates, however, that the largest part must be related to remobilised sediments and cannot be considered as sediment input from the adjacent rockwalls. This conclusion is also supported by direct measurements of sediment input.
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Zhou, Peng, Jiawang Chen, Dongrui Ruan, Xiaoqing Peng, Xiaocheng Wu, Ziqiang Ren e Qiaoling Gao. "Design of a Marine Sediments Resistivity Measurement System Based on a Circular Permutation Electrode". Journal of Marine Science and Engineering 9, n.º 9 (13 de setembro de 2021): 995. http://dx.doi.org/10.3390/jmse9090995.
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Marine sediments are rich in mineral resources, organic resources, and microbial life. The study of marine sediments is of great significance for the development and utilization of marine resources and understanding the life process. Resistivity is the overall characteristic of the electrical conductivity of marine sediments. Measuring the resistivity of marine sediments is helpful to ascertain the marine geological structure, study the distribution of marine mineral resources, and evaluate the marine soil environment. Measuring the resistivity of marine sediments is of great significance to promote marine exploration. At present, the resistivity measurement device on the market can be directly used to measure soil and water on land, but if used to measure marine sediments, it will be disturbed by seawater temperature and pressure, resulting in large errors. In this paper, a high-precision pressure-maintaining transfer system of marine sediment resistivity measurement instrument based on circular permutation electrode is designed, which can measure the resistivity of marine sediment samples after pressure-maintaining transfer. At the same time, a new type of circular permutation electrode measurement method is proposed, which makes the resistivity value more accurate, reduces the length of the probe appropriately, and saves the cost. By measuring the resistivity of marine sediments, the type of sediments can be inverted, which provides a way of thinking about the promotion of the research and development and utilization of marine resources.
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Vivant, Anne-Laure, Catherine Boutin, Stéphanie Prost-Boucle, Sandrine Papias, Christine Ziebal e Anne-Marie Pourcher. "Fate of two strains of extended-spectrum beta-lactamase producing Escherichia coli in constructed wetland microcosm sediments: survival and change in antibiotic resistance profiles". Water Science and Technology 79, n.º 8 (15 de abril de 2019): 1550–60. http://dx.doi.org/10.2166/wst.2019.153.
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Abstract Free water surface constructed wetlands (FWS CW) are efficient technologies to limit the transfer of antibiotic resistant bacteria (ARB) originating from urban effluents into the aquatic environment. However, the decrease in ARB from inflow to outflow through the FWS CW may be explained by their transfer from the water body to the sediment. To investigate the behavior of ARB in the sediment of a FWS CW, we inoculated three microcosms with two strains of extended-spectrum beta-lactamase producing Escherichia coli (ESBL E. coli) belonging to two genotypes. Microcosms were composed of two sediments collected at two locations of an FWS CW from which the strains were isolated. Phragmites were planted in one of the microcosms. The survival curves of the two strains were close regardless of the genotype and the type of sediment. After a rapid decline, both strains were able to survive at low level in the sediments for 50 days. Their fate was not affected by the presence of phragmites. Changes in the bla content and antibiotic resistance of the inoculated strains were observed after three weeks of incubation, indicating that FWS CW sediments are favorable environments for spread of antibiotic resistance genes and for the acquisition of new antibiotic resistance.
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Shen, Huadong, Zhongbo Yu, Ge Yu e Xiaoli Shi. "Grain Size and Pollen of Sediments in Wanghu Lake (Central China) Linked to Hydro-Environmental Changes". Water 12, n.º 1 (20 de dezembro de 2019): 45. http://dx.doi.org/10.3390/w12010045.
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Grain size of lake sediments is often measured in paleolimnological studies, especially investigations of past paleoclimatic and paleohydrologic changes. The implications of such measures, however, remain unclear, since watershed hydrology and the related transfer of materials to the lake are affected by local climate variables, hydrological shifts, and vegetation cover variables. Sediment from Wanghu Lake in the middle reaches of the Yangtze River have apparently been affected by land cover changes and lake-river system transitions caused by a sluice gate built at Fuchi in 1967. These changes influenced the watershed hydrology, thereby confounding paleoclimatic and paleohydrologic interpretations by proxy records in sediment cores. We collected sediment cores from the center of Wanghu Lake and analyzed trends in pollen and physical properties through sedimentary records to investigate land cover changes and hydrological transitions during the past 90 years. The grain size of the sediment core increased with precipitation and the significant relationships between pollen and grain size after 1967 indicated that sediment transfer to the lake was controlled by rainfall and land cover changes due to human-induced deforestation and farming in the lake catchment. Interestingly before 1967, there was no significant relationship between the pollen and grain size or between the precipitation and grain size, indicating that the sediment of WanghuLake was not simply from the lake catchment. The different relationships patterns before and after 1967 indicated that the sediments in the lake were not only transported following precipitation and discharge from the lake catchment but also came from the Yangtze River draining back into the lake during the flood seasons before 1967. These results highlight matters needing attention and the potential application of grain size of sediments for reconstructions of past hydro-environmental changes.
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Wakeham, S. G., e A. P. McNichol. "Transfer of lipids through marine water columns to sediments – insights from stable and radiocarbon isotopes". Biogeosciences Discussions 11, n.º 6 (24 de junho de 2014): 9761–812. http://dx.doi.org/10.5194/bgd-11-9761-2014.
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Abstract. Compound-specific 13C and 14C compositions of diverse lipid biomarkers (fatty acids, alkenones, hydrocarbons, sterols, and fatty alcohols) were measured in sinking particulate matter collected in sediment traps and from underlying surface sediments in the Black Sea, the Arabian Sea and the Ross Sea. The goal was to develop a multi-parameter approach to constrain relative inputs of organic carbon (OC) from marine biomass, terrigenous vascular plant, and relict sources. Marine biomass in sediment trap material from the Black Sea and Arabian Sea accounted for 66–100% of OC, with lower terrigenous (3–8%) and relict (4–16%) contributions. Marine biomarkers in sediments constituted lower proportions of OC (66–90%), with consequentially higher proportions of terrigenous and relict carbon (3–17% and 7–13%, respectively). Ross Sea data were insufficient to allow similar mass balance calculations. It is apparent that whereas particulate organic carbon is overwhelmingly marine in origin, there are also significant proportions of pre-aged terrigenous and relict OC that become proportionally more important in sediments. These results indicate that pre-aged OC is better preserved during vertical transport to and burial at the seafloor and/or it reaches the sediment by lateral advection rather than only by the vertical sinking/biological pump that affects the upper ocean-derived marine POC.
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Yang, Fan, Yankui Tang, Yuwei Mi, Lu Jiang, Penghong Luo e Yang Yang. "Mn(II) Sorption on Stream Sediments Sampled in Manganese Mining Area: Dynamics and Mechanisms". Applied Sciences 12, n.º 7 (25 de março de 2022): 3368. http://dx.doi.org/10.3390/app12073368.
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The stream sediments that have been impacted by manganese (Mn) containing wastewater for decades contain not only abundant microorganisms but also organic/inorganic substances. To achieve effective treatment of manganese (Mn)-containing effluent and recovery of Mn from water/sediments, the Mn(II) sorption behaviors and mechanism on sediments of a stream in Mn mining areas were studied. In addition, the study analyzed the effects of various factors (initial concentration, solution pH, sediment dose, contact time, and coexisting cations) on the Mn sorption efficiency of Daxin sediments, and explored the contribution of microbial activity in the sediment sorption of Mn(II). The results showed that the sorption process of Mn(II) on the sediments was consistent with the Elovich and Freundlich models, and the removal of heavy metals was maximum at 40 °C (62.47–98.93%), pH = 8 (77.51%), initial concentration of 1 mmol·L−1 (95.37%) and sediment dosing of 12 g·L−1 (98.93%). The addition of 50 mM NaN3 inhibited the microbial activity in the Daxin sediment, reducing the sorption and removal rates of Mn(II) by 0.605 mg·g−1 and 8.92%, respectively. After sorption, the proportion of the Fe–Mn oxidation(iron–manganese) state in Daxin sediments decreased from 54% to 43%, while the proportion of the exchangeable state increased by 10.80%. Microorganisms in the sediment had a positive effect on inhibiting heavy metal migration and reducing the bioavailability of contaminants in the soil. Through this study, we hope to further understand the sorption and desorption mechanism of manganese by stream sediments in manganese ore areas, so as to provide a guide on the management and recovery of Mn from stream sediments in manganese mining areas.
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Adel, Mnaf, e Ali N. Hilo. "The Effects of submerged vanes inclination angle on sediment transport into sub-channel". Wasit Journal of Engineering Sciences 11, n.º 1 (1 de abril de 2023): 105–15. http://dx.doi.org/10.31185/ejuow.vol11.iss1.414.
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The sub-channels that branch from the larger rivers may be manmade or natural. From the major channels, these sub-channels transfer sediments and water. The deposition of sediments at the entrance, sub-channel is a significant research challenge because it threatens the sub-facilities channel's and reduces the sub-carrying channel's capacity. Therefore, submerged vanes were used to reduce the amount of sediment entering the sub-channel. The goal of the vanes is to reduce the amount of sediment entering the sub-channel, hence redistributing sediment at the sub-entry channel's . They are vertically aligned with the flow direction and tilted at a certain angle. A physical model of the main channel, a sub-channel at a right angle, and a sediment feeder mechanism were developed. 51 tests were undertaken, 3 with submerged vanes and 48 without, with a varying number of submerged vanes (7, 5, 3 and 1). And angling it at various angles (10˚, 20˚, 30˚, and 40˚) in the discharge direction and with three sub-discharges of (19.1, 27 and 30.5 l/s), the sediment concentration flow was (6 kg/h). The weights of the sediments in sub-channel were calculated, and it was found that there is an effective use of these vanes and that the least amount of sediments is achieved when the angle is (20ᵓ). It was observed that the performance of the submerged vanes was significantly improved when there was a decrease in the discharge of the sub-channel.
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Zhang, Fei, Zhangdong Jin, A. Joshua West, Zhisheng An, Robert G. Hilton, Jin Wang, Gen Li et al. "Monsoonal control on a delayed response of sedimentation to the 2008 Wenchuan earthquake". Science Advances 5, n.º 6 (junho de 2019): eaav7110. http://dx.doi.org/10.1126/sciadv.aav7110.
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Infrequent extreme events such as large earthquakes pose hazards and have lasting impacts on landscapes and biogeochemical cycles. Sediments provide valuable records of past events, but unambiguously identifying event deposits is challenging because of nonlinear sediment transport processes and poor age control. Here, we have been able to directly track the propagation of a tectonic signal into stratigraphy using reservoir sediments from before and after the 2008 Wenchuan earthquake. Cycles in magnetic susceptibility allow us to define a precise annual chronology and identify the timing and nature of the earthquake’s sedimentary record. The grain size and Rb/Sr ratio of the sediments responded immediately to the earthquake. However, the changes were muted until 2 years after the event, when intense monsoonal runoff drove accumulation of coarser grains and lower Rb/Sr sediments. The delayed response provides insight into how climatic and tectonic agents interact to control sediment transfer and depositional processes.
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Peixoto, Luciana, Pier Parpot e Gilberto Martins. "Assessment of Electron Transfer Mechanisms during a Long-Term Sediment Microbial Fuel Cell Operation". Energies 12, n.º 3 (2 de fevereiro de 2019): 481. http://dx.doi.org/10.3390/en12030481.
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The decentralized production of bioelectricity as well as the bioremediation of contaminated sediments might be achieved by the incorporation of an anode into anaerobic sediments and a cathode suspended in the water column. In this context, a sediment microbial fuel cell microcosm was carried out using different configurations of electrodes and types of materials (carbon and stainless steel). The results showed a long-term continuous production of electricity (>300 days), with a maximum voltage of approximately 100 mV reached after ~30 days of operation. A twofold increase of voltage was noticed with a twofold increase of surface area (~30 mV to ~60 mV vs. 40 cm2 to 80 cm2), while a threefold increase was obtained after the substitution of a carbon anode by one of stainless steel (~20 mV to ~65 mV vs. 40 cm2 to 812 cm2). Cyclic voltammetry was used to evaluate sediment bacteria electroactivity and to determine the kinetic parameters of redox reactions. The voltammetric results showed that redox processes were limited by the diffusion step and corresponded to a quasi-reversible electron charge transfer. These results are encouraging and give important information for the further optimization of sediment microbial fuel cell performance towards the long-term operation of sediment microbial fuel cell devices.
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VANDENPLAS, S., A. B. TEMSAMANI, Z. CISNEROS e L. VAN BIESEN. "A FREQUENCY DOMAIN INVERSION METHOD APPLIED TO OBLIQUE REFLECTED SIGNALS FROM A WATER–SEDIMENT INTERFACE". Journal of Computational Acoustics 09, n.º 02 (junho de 2001): 553–63. http://dx.doi.org/10.1142/s0218396x01000747.
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Due to the complexity of the seafloor as an acoustical system, it is very important to validate wave propagation models and test inversion methods first in the laboratory. A known sediment is placed in a water-filled tank, in such a way that a smooth water–sediment interface is obtained with minimal air bubbles retained in the sediment. Two broadband piston transducers are used to carry out reflection experiments at oblique incidence. The placement of the emitter and receiver is symmetrical with respect to a vertical plane perpendicular to the sediment surface. The aim of this work is to find physical parameters of the sediment from the reflected signals. A general viscoelastic model that considers losses due to absorption and dispersion along the propagation of the wave through the sediments is proposed. A rational transfer function is used to model the viscoelastic modulus of the bulk sediments and a comparison with constant Q viscoelastic modelling is performed. The estimation of the model parameters is elaborated using a Maximum Likelihood Estimator in the frequency domain.
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Glazunova, Irina V., Sergey N. Rednikov e Khanh Zu Nguyen. "Experimental determination of the characteristics of sediment transfer and sedimentation under uniform movement in the channel bed, taking into account the influence of natural and artificial crossbars". Prirodoobustrojstvo, n.º 4 (2023): 92–97. http://dx.doi.org/10.26897/1997-6011-2023-4-92-97.
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The issue of the research – investigation of the hydrodynamics of river sediments’ artificial structures in the interfluve of the Lo and the Kau rivers (The Northern Vietnam) as a tool for the formation of hydrodynamic and geochemical anomalies in water bodies. Laboratory studies of the speeds of movement and sedimentation of suspended sediments were carried out according to the planning of the experiment for a series of using natural and artificial crossbars in modeling the processes of transport and sedimentation of sediments. Based on a laboratory model experiment, the parameters of crossbars at different flow rates are considered for conditions of uniform movement of water in the tray and condition of sedimentation. Graphs of the dependences of the velocities of movement and sediment deposition are drawn, and the parameters of vortex flows in the zone before and after the crossbars are considered. Based on the results of laboratory modeling, graphs of the dependence of the characteristics of the transit and deposition of sediment, taking into account the influence of crossbars, are drawn. The obtained results of laboratory modeling provide data for planning further laboratory and field experiments on the transit of sediment with fertile silt, the accumulation of sediment in the riverbed and the influence of natural and artificial crossbars on sediment deposition, as well as for the formation of mobile sediment-retaining dams. The experiment was planned according to the Shenk X method. The results of the experiment were processed in MathCad and Solidworks.
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Wang, Jianlong, Jinsheng Sun, Hang Bian, Qibing Wang, Zhenbo Feng, Cheng Lu, Han Ren, Rongchao Cheng, Jintang Wang e Ren Wang. "Kinetic Hydrate Inhibition of Natural Gels in Complex Sediment Environments". Gels 8, n.º 12 (22 de novembro de 2022): 758. http://dx.doi.org/10.3390/gels8120758.
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Natural gels are emerging as a hotspot of global research for their greenness, environmental-friendliness, and good hydrate inhibition performance. However, previous studies mostly performed experiments for simple pure water systems and the inhibition mechanism in the sediment environment remains unclear. Given this, the inhibition performance of xanthan gum and pectin on hydrate nucleation and growth in sediment environments was evaluated via hydrate formation inhibition tests, and the inhibition internal mechanisms were revealed via a comprehensive analysis integrating various methods. Furthermore, the influences of natural gels on sediment dispersion stability and low-temperature fluid rheology were investigated. Research showed that the sediments of gas hydrate reservoirs in the South China Sea are mainly composed of micro-nano quartz and clay minerals. Xanthan gum and pectin can effectively inhibit the hydrate formation via the joint effects of the binding, disturbing, and interlayer mass transfer suppression processes. Sediments promote hydrate nucleation and yet inhibit hydrate growth. The interaction of sediments with active groups of natural gels weakens the abilities of gels to inhibit hydrate nucleation and reduce hydrate formation. Nonetheless, sediments help gels to slow down hydrate formation. Our comprehensive analysis pointed out that pectin with a concentration of 0.5 wt% can effectively inhibit the hydrate nucleation and growth while improving the dispersion stability and low-temperature rheology of sediment-containing fluids.
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Sulistiowati, Sulistiowati, Neviaty Putri Zamani, Dietriech Geofrfey Bengen, Cheng Ling Lim e Muhammad Reza Cordova. "Characteristic of Microplastic on Coral Reef Sediment and Sea Urchin (Diadema sp.) in Tidung Island, Jakarta Bay, Indonesia". ILMU KELAUTAN: Indonesian Journal of Marine Sciences 28, n.º 4 (23 de agosto de 2023): 289–300. http://dx.doi.org/10.14710/ik.ijms.28.4.289-300.
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Microplastics are recognized as common contaminants of coral ecosystem in Tidung Island, affecting both sediment and sea urchins residing in this environment. Therefore, this study aimed to determine the characteristics of microplastics found in sediment, the mouth, and the digestive system of sea urchins (Diadema sp.), assessing the relationship between coral cover percentage and microplastic type and size, and the transfer of microplastics from sediment to sea urchins. Sampling was conducted twice, namely in October 2021 and October 2022. Microplastics in sediments were extracted using ZnCl2. The destruction process of sea urchins used 30% H2O2 and FeSO4.7H2O, while the microplastics were identified with Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR). The results showed that the microplastics found in the sediments and sea urchins were similar in terms of shape, color, size, and plastic polymers. The forms of microplastics found in this study were fibre, fragment, and foam with fibre predominance, based on the results obtained. The size of microplastics found in sediments and sea urchins was dominated by sizes >1000 µm. Fibres were found in hard coral (HC) and dead coral (DC) conditions while fragments and foams were present in turf algae (TA), sponge (SP), and soft coral (SC) conditions. The microplastics found in sea urchins originate in part from sediments because they have similar characteristics. Sea urchins ingested microplastics from sediment, particularly those grown by algae as a food source. The increase in the number of microplastics found in sediment could potentially result in higher abundance in the biota.
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Kramer Stajnko, Janja, Renata Jecl e Matjaž Nekrep Perc. "Advances in Monitoring and Understanding the Dynamics of Suspended-Sediment Transport in the River Drava, Slovenia: An Analysis More than a Decade-Long". Applied Sciences 13, n.º 15 (7 de agosto de 2023): 9036. http://dx.doi.org/10.3390/app13159036.
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Managing sediment transport in streams is crucial to the surface water resource development strategy and has several implications for flood risk and water management, hydropower use, and balancing river morphology. This paper summarises the movement and behaviour of suspended sediment within the Slovenian portion of the River Drava, covering a span of thirteen years from 2005 to 2018. An analysis of relevant data collected during this period is also presented. Suspended-sediment dynamics strongly depend on flow velocity, seasonal variations in sediment sources, and human interventions in the riverbed. The transportation of material in the River Drava results in the accumulation of sediments in reservoirs and riverbeds, consequently impeding the natural hydrological cycle by reducing the outflow into aquifers. The 2018 high-water event is analysed in terms of the dependence of concentration of suspended sediments on discharge, where counterclockwise hysteresis was observed, providing an essential clue to the origin of sediment. Sediments from the River Drava in Slovenia are managed with some conventional processes and are mainly deposited or reintegrated into rivers and aquatic ecosystems. Some additional sediment management strategies with long-term solutions for efficient and comprehensive water management, hydropower, and ecological problems are proposed.
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Qureshi, Mohsin Usman, Maryam Alsaidi, Mubashir Aziz, Ilhan Chang, Ali Murtaza Rasool e Zaheer Abbas Kazmi. "Use of Reservoir Sediments to Improve Engineering Properties of Dune Sand in Oman". Applied Sciences 11, n.º 4 (10 de fevereiro de 2021): 1620. http://dx.doi.org/10.3390/app11041620.
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Managing sediments dredged from reservoirs of recharge dams is an environmental issue, however, these sediments can be an abundant and economical source of fine-grained fill soil. This experimental investigation quantifies the geotechnical properties of a reservoir sediment used to improve engineering properties of a poorly graded dune sand in Oman. The binary mixes were prepared with different percentages (5, 10, 20, 50, 75, 90, 95%) of sediment with sand. Laboratory tests such as gradation, consistency limits, compaction, and unconfined compression tests were performed to measure the engineering characteristics of the binary mixtures. The results showed that the maximum dry density increases up to a sediment content of 50% and then decreases with further increase in the sediment content. The optimum water content increases with the increase in sediment content from 17% for pure sand to 22.5% for pure sediment. The optimum moisture content shows a good correlation with the plastic limit of the binary mixture of sand and sediment. The unconfined compressive strength substantially increases with sediment content up to 75% and then decreases with further increase in the sediment content. The binary mixture of sand sediment is sensitive to moisture, however, the order of strength stability against moisture is dune sand mixed with 75, 50, and 20% sediments. The addition of sediment to dune sand improved the uniformity coefficient to some extent with an increase in the maximum and minimum void ratios as well. The elemental analysis of the sediment confirms that the material is non-contaminated and can be employed in geotechnical engineering applications as a sustainable and environmentally friendly solution.
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Queiroz, Lucas Gonçalves, Luana de Oliveira Hallai, Beatriz Rocha de Moraes, Rômulo Augusto Ando, Marcelo Pompêo e Bárbara Rani-Borges. "A straightforward protocol for extracting microplastics from freshwater sediment with high organic content". Knowledge & Management of Aquatic Ecosystems, n.º 426 (2025): 6. https://doi.org/10.1051/kmae/2025001.
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Extracting microplastics from sediment is critical in assessing pollution in freshwater environments. However, this process can be particularly challenging for clayey sediments with a significant organic matter content. This study proposes a simplified method for extracting microplastics from organic-rich clayey sediments and a complete protocol for sediment processing. To evaluate the extraction method, calcined clayey sediment was artificially enriched with varying organic content (20, 40, and 60%). Known quantities of plastic particles with distinct characteristics and compositions (PET, HDPE, PP, PE, and PS) were introduced into these artificial organic sediments, mixed with a saline solution, centrifuged, and then assessed the recovery rate. The recovery rate exceeded 83% for the five selected plastic types. Additionally, the method minimized particle loss by reducing the number of transfers between containers, a common issue in other microplastic extraction protocols. Based on the efficiency of the extraction method, we proposed and applied a protocol for environmental samples. The protocol comprises five key steps: (1) drying sediment samples, (2) density separation, (3) filtering, (4) digestion of organic matter, and (5) visual analysis. This protocol extracted a wide variety of microplastics with diverse shapes, colors, sizes, and polymeric compositions. These results demonstrate that the proposed protocol is both straightforward and effective in extracting plastic particles commonly found in clayey sediments of freshwater systems. Moreover, the protocol employs inexpensive, readily available, and environmentally friendly reagents, making it a more sustainable alternative to other methodologies for extracting microplastics from environmental matrices.
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Jackson, Leland J., David J. Rowan, R. Jack Cornett e Jacob Kalff. "Myriophyllum spicatum Pumps Essential and Nonessential Trace Elements from Sediments to Epiphytes". Canadian Journal of Fisheries and Aquatic Sciences 51, n.º 8 (1 de agosto de 1994): 1769–73. http://dx.doi.org/10.1139/f94-178.
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To test the hypothesis that elements can be transferred from freshwater sediments to macrophytes and to epiphytes, we grew Myriophyllum spicatum in natural sediments containing 60Co and 54Mn (essential) and 137Cs, 152Eu, 154Eu, and 155Eu (nonessential). We found no differences between shoot or epiphyte to sediment bioaccumulation factors (BAFs) and only found differences between root and shoot to sediment BAFs for 60Co and 54Mn, probably because these elements adsorb onto root surfaces. We found no differences in BAFs for any elements between shoots and epiphytes, suggesting no differences in the transfer of essential and nonessential elements. There were, however, interelement differences for the roots, again probably due to surface adsorption related to redox sensitivity. Using isotope specific activity ratios, we calculated that over 75% of the Co and 100% of the Mn in M. spicatum was obtained from the sediments and that all Co and Mn in the epiphytes was sediment derived through the host. Although the net flux of trace elements from the sediments to the water via macrophytes has been shown to be small in most situations, buried pulses of nonessential elements may be reintroduced to the littoral food web by epiphytes being grazed by invertebrates and fish.
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Kim, Min-Cheol, e Yong Sik Gihm. "Fluidal Peperites Recorded in the Cretaceous Lacustrine Sediments in the Southern Korean Peninsula: Syn-Magmatic Sediment Fluidization and Its Influence on the Peperite Formation". Minerals 14, n.º 9 (20 de setembro de 2024): 951. http://dx.doi.org/10.3390/min14090951.
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This study assessed the influence of sediment and water redistribution in host sediments on peperite formation by examining the peperites at the boundary between Cretaceous lacustrine sedimentary successions and intruding dikes (D1 and D2). The peperite zones occur along the dike margins and consist of fluidal juvenile fragments, classified as Type A and Type B perperite zones based on lateral extent of the peperite zones. Type A peperite zone, the dominant type, exhibites a narrow distribution (<20 cm), whereas Type B peperite zone sporadically occurs along D1 with a wider width (<1 m). Type B peperite zone is laterally linked with clastic dikes. These dikes containi fluidal shaped dike fragments with jigsaw-fit textures, indicating syn-magmatic fluidization and the resultant formation of the clastic dike via heat transfer. During dike emplacement, the interaction between the host sediments and the intruding magma formed Type A along the margins. Simultaneously, the clastic dikes, composed of fluidized sediments and water, supplied additional water and sediments, enhancing magma-host sediment intermingling and leading to the wide lateral extent of Type B. Our findings demonstrate that sediment and water redistribution via syn-magmatic fluidization is crucial in peperite formation, influencing the initial processes of phreatomagmatic volcanism.
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Sandaa, Ruth-Anne, Vigdis Lid Torsvik e Jostein Goksøyr. "Transferable drug resistance in bacteria from fish-farm sediments". Canadian Journal of Microbiology 38, n.º 10 (1 de outubro de 1992): 1061–65. http://dx.doi.org/10.1139/m92-174.
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Antibiotic-resistant bacteria were isolated from sediment samples collected beneath two fish farms west of Bergen (Norway). The samples were collected just after the fish had been treated with oxytetracycline. Eighty-four bacterial isolates were tested for susceptibility to antibacterial agents. Most of the isolates were resistant to oxytetracycline, kanamycin, and sulfamethoxazole. Transferable plasmid-related resistance was shown by direct cell transfer and agarose gel electrophoresis. Among 34 multiple-resistant isolates, 7 isolates were able to transfer resistance to Escherichia coli HB101. Phenotypical characterization indicated that these seven isolates belonged to the genera Vibrio and Pseudomonas. The results indicate that sediments beneath fish farms may serve as a reservoir for transferable antimicrobial resistance genes. Key words: drug resistance, gene transfer, marine sediment bacteria.
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Tasselli, Stefano, Laura Marziali, Claudio Roscioli e Licia Guzzella. "Legacy Dichlorodiphenyltrichloroethane (DDT) Pollution in a River Ecosystem: Sediment Contamination and Bioaccumulation in Benthic Invertebrates". Sustainability 15, n.º 8 (11 de abril de 2023): 6493. http://dx.doi.org/10.3390/su15086493.
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Dichlorodiphenyltrichloroethane (DDT) contamination in the Toce River in northern Italy was studied by collecting data from 2016 to 2021 upstream and downstream of a production factory which in the past had discharged technical DDT. Analysis of sediments and of bioaccumulation in different benthic invertebrate taxa (Gammaridae, Diptera, Ephemeroptera Baetidae and Heptageniidae) was carried out to assess the transfer of DDT from sediments to benthic invertebrates and the environmental risk of this legacy pollutant for the river ecosystem. DDT and its metabolites dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD), here called DDx, were analyzed by isotope dilution gas chromatography–mass spectrometry (GC-MS/MS). DDx values in sediments in upstream stations (1.14–2.25 ng g−1 1% Organic Carbon) were lower than downstream of the industrial site (5.60–7.60 ng g−1 1% Organic Carbon), often exceeding Sediment Quality Guidelines for total DDx. Peak levels derived from new inputs of parental DDT, as confirmed by fingerprint analysis. Bioaccumulation was higher at downstream sites (up to 5107 ng g−1 lipid weight), confirming the bioavailability of residual DDT as well as active metabolism, with the formation of DDD and DDE. The Biota-Sediment Accumulation Factor evidenced the highest values (over 4.2) for Diptera and Gammaridae, highlighting that invertebrates can transfer contamination from sediments to the trophic chain. Linear regression models were developed to estimate DDx concentrations in benthic invertebrates from DDx concentrations in sediments. However, determination coefficients R2 remained in the range of 0.36–0.51, highlighting the necessity of bioaccumulation analysis to fully estimate environmental risk. The results show that DDT contamination, even if residual, may still represent a risk due to its effective transfer to the trophic chain.
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Tang, Q., Y. Bao, X. He e A. Wen. "Heavy metal enrichment in the riparian sediments and soils of the Three Gorges Reservoir, China". Proceedings of the International Association of Hydrological Sciences 367 (3 de março de 2015): 244–50. http://dx.doi.org/10.5194/piahs-367-244-2015.
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Abstract. The Three Gorges Reservoir encompasses a riparian zone with a vertical height of 30 m and a total area of 349 km2 that has been subjected to alternate inundation and exposure due to regular impoundment. Sedimentation on the riparian landforms constitutes an important pathway for riverine contaminant redistribution. In an attempt to understand heavy metal enrichment since water inundation, riparian sediments and soils were sampled along five transects in a typical riparian zone composed of cultivated bench terraces in the middle reaches. Heavy metals (Cr, Ni, Cu, Zn, As, Cd and Pb) were determined to characterize the lateral distribution and vertical transfer ratio. The results indicated that all heavy metals were enriched to varying extents both in the riparian sediments and soils, compared with regional background contents in soils and the reference levels in sediments. However, heavy metal levels in the riparian sediments were generally higher than those in the riparian soils, while those in the upper riparian soils (0–5 cm) were overall slightly higher than those in the lower riparian soils (5–10 cm). There was a decreasing trend of heavy metal contents with increasing elevation. The elevated levels of heavy metals in the riparian sediments may be attributed to sediment yields from upstream anthropogenic sources, especially during major rainstorms in the wet season when large loads of contaminated sediment may be produced from diffuse source areas. Heavy metals can also be adsorbed to pure sediment in the course of mobilization or after deposition. Considering that the riparian soils are local weathering products without mobilization, the enrichment of heavy metals may principally be ascribed to chemical adsorption from dissolved fractions or vertical transfer from overlaid sediments. Heavy metal enrichment may further be affected by the specific type of hydrologic regime such that relatively long flooding duration caused by water impoundment and natural floods was responsible for the relatively higher levels of heavy metals in the lower portions of the riparian zone.
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Seidel, H., J. Ondruschka, P. Morgenstern e U. Stottmeister. "Bioleaching of heavy metals from contaminated aquatic sediments using indigenous sulfur-oxidizing bacteria: a feasibility study". Water Science and Technology 37, n.º 6-7 (1 de março de 1998): 387–94. http://dx.doi.org/10.2166/wst.1998.0776.
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The removal of heavy metals from contaminated river sediments was studied using suspension leaching under laboratory conditions and percolation leaching in a pilot plant. The leaching potential of indigenous sulfur-oxidizing bacteria was compared with acid treatment. Bioleaching with elemental sulfur as substrate was found to be better than treatment with sulfuric acid for the solubilization of all metals tested. The physical and chemical properties of the sediments used in this study did not affect leaching capacity under optimum conditions in the laboratory. Under the practical conditions in the pilot plant, the redox state of sludge had a considerable influence on leaching efficiency. In a deposited oxic sediment with good permeability, about 62% of the metals tested were removed by percolation leaching after 120 days. Zn, Cd, Ni, Co and Mn were sufficiently leached to enable treated sediments to be reused as soil. In a freshly dredged anoxic sediment, only a total of 9 % of metals were removed. The results indicate that freshly dredged sediments need to undergo pretreatment before percolation leaching to improve mass transfer and to activate the leaching active bacteria.
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Wang, Yang, Yufei Wang, Xiaoming Wan, Chen Huang, Rui Wang, Xiujuan Liu, Jiaji Yi e Yunzhong Zhang. "Influence of the Hanjiang River’s Inlet Sediment Decrease on Modern Sedimentation in the Underwater Delta". Applied Sciences 13, n.º 14 (10 de julho de 2023): 8039. http://dx.doi.org/10.3390/app13148039.
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The Hanjiang River is the second-largest river in Guangdong Province, China. The modern sedimentation pattern of the Hanjiang subaqueous delta has been significantly affected by changes in the sediment delivered by the Hanjiang River. Based on multiperiod charts and columnar samples from the Hanjiang subaqueous delta, the influence of a sharp decrease in the sediment flux from the Hanjiang River on the deposition of the Hanjiang subaqueous delta in the past 60 years was studied through a combination of chart-based analysis of the evolution of erosion and deposition and the analysis of sediment samples. The results showed that the significant reductions in sediment fluxes from the Hanjiang River and Rongjiang River had obviously spatially differentiated effects on the deposition pattern of the Hanjiang subaqueous delta. The significant decreases in sediment fluxes from the Hanjiang River and the Rongjiang River caused the sediment grain size of the columnar samples in the near-estuary area of the Hanjiang River subaqueous delta to coarsen upward, the deposition rate to decrease, and the depositional state to change to an erosional state. Since the sediments discharged into the ocean after reservoir impoundment are mainly fine-grained suspended sediments, the supply of coarse-grained sediments in the Hanjiang subaqueous delta decreased, resulting in the upward fining of the columnar samples. The spatial response pattern of the Hanjiang subaqueous delta to the sharp decrease in sediment flux into the sea differed significantly from those of the Yangtze and Yellow subaqueous deltas.
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Kouhpeima, A., S. Feiznia e H. Ahmadi. "Tracing fine sediment sources in small mountain catchment". Water Science and Technology 63, n.º 10 (1 de maio de 2011): 2324–30. http://dx.doi.org/10.2166/wst.2011.509.
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Fine sediment represents an important diffuse source pollutant in surface waters, due to its role in governing the transfer and fate of many substances, including nutrients, heavy metals, pesticides and other organic contaminants, and its influence on aquatic ecology. Therefore, catchment management strategies frequently need to include provision for the control of sediment mobilization and delivery. The sediment tracing concept provides a valuable framework for assisting the management and control of diffuse source sediment pollution by identifying the key sources and demonstrating the importance of intermediate storages and the likely impact of upstream mitigation strategies on downstream sediment and sediment associated contaminant fluxes. In this research, fine sediment sources were identified using tracing method. By field works, sediments were sampled from dam reservoir, different sources were also sampled. Fifteen tracers were first selected for tracing which are: The amounts of N, P, C, Cr, Co, Mg, K, Na, smectite, chlorite, illite, kaolinite, and two magnetic properties consisting of Low Frequency Magnetic Susceptibility (XLF) and Frequency Dependent Magnetic Susceptibility (XFD). The samples were analyzed in the laboratory for these parameters and different statistical methods were applied to the data including Non-parametric Kruskal–Wallis Test and Stepwise Discriminant function analysis. The results provide important information on the relative importance of fine sediment sources to the reservoir sediments, which can be used to support model validation and the targeting of management and control strategies.
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Ivanov, Maksim M., Nadezhda Ivanova e Valentin Golosov. "Sediment and Particulate 137Cs Budget Studies in Upa River Basin: History, Results, and Prospects". Land 12, n.º 1 (5 de janeiro de 2023): 175. http://dx.doi.org/10.3390/land12010175.
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The intensive pollution of vast areas after the Chernobyl accident, especially in the territories of Ukraine, Russia, and Belarus, has not only become a serious environmental issue, but also presents wide methodological opportunities for studying the functioning of natural systems. The proposed work is a generalization of the results of studies on the migration of 137Cs in the runoff of river sediments, which were carried out in the basin of the Upa River for over 30 years after the accident. This basin is one of the most radioactively contaminated and studied in Central Russia. Over the past three decades, under the conditions of the decreasing snowmelt runoff in the spring and reduced share of cultivated land over the post-Soviet period, the intensity of the 137Cs transfer has decreased. The 137Cs deposit losses associated with erosion activities do not exceed a few percent. Most of the mobilized sediments and sediment-associated radionuclides accumulate in dry valleys or artificial reservoirs. With a general reduction in the durations of floods, rivers have become the predominant channels for the transfer of sediment yield and particulate pollutants. The exploration of the vertical distribution of the 137Cs in the accumulative strata makes it possible to identify the changes in the sediment budgets of the rivers and their radioecological consequences.
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Koppes, Michèle, Richard Sylwester, Andres Rivera e Bernard Hallet. "Variations in Sediment yield Over the Advance and Retreat of a Calving Glacier, Laguna San Rafael, North Patagonian Icefield". Quaternary Research 73, n.º 1 (janeiro de 2010): 84–95. http://dx.doi.org/10.1016/j.yqres.2009.07.006.
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Bathymetric and sub-bottom acoustic data were collected in Laguna San Rafael, Chile, to determine sediment yields during the Little Ice Age advance and subsequent retreat of San Rafael Glacier. The sediment volumes and subaqueous landforms imaged are used to interpret the proglacial dynamics and estimate erosion rates from a temperate tidewater glacier over a complete advance–retreat cycle. Sediment yields from San Rafael Glacier averaged 2.7 × 10 m/a since the end of the Little Ice Age, circa AD 1898, corresponding to average basin-wide erosion rates of 23 ± 9 mm/a; the highest erosion rates, 68 ± 23 mm/a, occurred at the start of the retreat phase, and have since been steadily decreasing. Erosion rates were much lower during glacial advance, averaging at most 7 mm/a, than during retreat. Such large glacial sediment yields over two centuries of advance and retreat suggest that the contribution of sediments stored subglacially cannot account for much of the sediment being delivered to the terminus today. The detailed sub-bottom information of a proglacial lagoon yields important clues as to the timing of erosion, deposition and transfer of glacigenic sediments from orogens to the continental shelves, and the influence of glacier dynamics on this process.
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Zhou, Peng, Chunyue Zhang, Jingkun Ai, Yongqiang Ge, Xiaoqing Peng, Qiaoling Gao, Wei Wang, Zhonghui Zhou e Jiawang Chen. "The Numerical Simulation and Experimental Study of Heat Flow in Seabed Sediments Based on COMSOL". Journal of Marine Science and Engineering 10, n.º 10 (22 de setembro de 2022): 1356. http://dx.doi.org/10.3390/jmse10101356.
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In situ electrothermal conduction heating technology refers to the setting up of a heat source directly within the sediments, using the heat conductivity of the sediments and the heat radiation of the heat source for heat transfer to achieve the in situ heating of the sediments. The in situ electrothermal conduction heating of sediments has the disadvantage of the heating equipment being easily damaged and difficult to operate, and requires the equipment to be able to withstand seawater pressure and marine corrosion. In this paper, based on the combination of numerical simulations (using COMSOL Multiphysics software) and approximate in situ electrothermal conduction heating experiments, the temperature field and other factors of sediments heated by in situ conductive heating (in a specific area) were studied to determine a numerical model for sediment heat flow in a specific area under different pressures and initial temperatures, and the correctness of the numerical model was further verified by comparative experiments. The results of this study have important implications for future studies on the actual thermal properties of sediments and even heat transfer mechanisms during gas hydrate extraction.
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Ward, Melissa A., Tessa M. Hill, Chelsey Souza, Tessa Filipczyk, Aurora M. Ricart, Sarah Merolla, Lena R. Capece et al. "Blue carbon stocks and exchanges along the California coast". Biogeosciences 18, n.º 16 (18 de agosto de 2021): 4717–32. http://dx.doi.org/10.5194/bg-18-4717-2021.
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Abstract. Salt marshes and seagrass meadows can sequester and store high quantities of organic carbon (OC) in their sediments relative to other marine and terrestrial habitats. Assessing carbon stocks, carbon sources, and the transfer of carbon between habitats within coastal seascapes are each integral in identifying the role of blue carbon habitats in coastal carbon cycling. Here, we quantified carbon stocks, sources, and exchanges in seagrass meadows, salt marshes, and unvegetated sediments in six bays along the California coast. In the top 20 cm of sediment, the salt marshes contained approximately twice as much OC as seagrass meadows did, 4.92 ± 0.36 kg OC m−2 compared to 2.20 ± 0.24 kg OC m−2, respectively. Both salt marsh and seagrass sediment carbon stocks were higher than previous estimates from this region but lower than global and US-wide averages, respectively. Seagrass-derived carbon was deposited annually into adjacent marshes during fall seagrass senescence. However, isotope mixing models estimate that negligible amounts of this seagrass material were ultimately buried in underlying sediment. Rather, the vast majority of OC in sediment across sites was likely derived from planktonic/benthic diatoms and/or C3 salt marsh plants.
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Gray, Derek K., e Hugh J. MacIsaac. "Diapausing zooplankton eggs remain viable despite exposure to open-ocean ballast water exchange: evidence from in situ exposure experiments". Canadian Journal of Fisheries and Aquatic Sciences 67, n.º 2 (fevereiro de 2010): 417–26. http://dx.doi.org/10.1139/f09-192.
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To reduce the transfer of nonindigenous species, regulations require transoceanic ships to exchange ballast with ocean water before discharging into the Great Lakes. Although ballast water exchange (BWE) is effective for live freshwater animals, laboratory experiments provide mixed results with regards to its impact on diapausing zooplankton eggs. We conducted an in situ test of the effectiveness of BWE for treating diapausing eggs in ballast sediments. Incubation chambers containing ballast sediment were placed in ballast tanks of cargo vessels transiting from North America to Europe. Each vessel had paired ballast tanks, one of which remained filled with Great Lakes water (control), while the second was exchanged with mid-ocean water. Laboratory viability tests were then conducted to compare viability of eggs recovered from sediments placed in both treatments, as well as identical sediments that remained at the laboratory in cold storage. No significant differences in egg viability were detected between treatments, but more species hatched from sediment that remained in cold storage. Results indicate that physical conditions in ballast tanks may affect egg viability, but saltwater exposure does not eliminate the risk of species introductions via diapausing eggs. Strategies that minimize sediment accumulation in ballast tanks can reduce the risk of species introductions via diapausing eggs.
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Bentley, Samuel J., e Elisabeth Kahlmeyer. "Patterns and mechanisms of fluvial sediment flux and accumulation in two subarctic fjords: Nachvak and Saglek Fjords, Nunatsiavut, Canada". Canadian Journal of Earth Sciences 49, n.º 10 (outubro de 2012): 1200–1215. http://dx.doi.org/10.1139/e2012-052.
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Recent marine sedimentary deposits and river discharge in two subarctic fjords in Nunatsiavut (Northern Labrador, Canada) have been studied to elucidate patterns and mechanisms of fluvial sediment transfer and accumulation in the fjords, to further our understanding of the longer-term sedimentary record. Multibeam and sub-bottom acoustic data and sediment cores were collected in Nachvak and Saglek fjords, within Canada’s Torngat Mountains National Park, as part of the most extensive study of the park’s marine resources to date. Cores were subsampled for X-radiography, grain size, and 210Pb/137Cs geochronology. Muddy basin sediments within each fjord are bioturbated, indicating circulation of oxygenated bottom water. Depositional fluxes and inventories of 210Pb indicate efficient marine scavenging of 210Pb by fine suspended sediments. In Nachvak Fjord, with small rivers and steep, presently glaciated catchments, postglacial and recent sediment accumulation rates are similar, implying relatively constant sedimentation over time. In Saglek Fjord, fed by larger rivers with more extensive catchments that lack glaciers, recent sediment accumulation is more rapid than that averaged over postglacial time. Present mass accumulation rates for the Nachvak Fjord basin are on average 39 000 t·year–1 for the entire basin, and for Saglek 43 000 t·year–1 for the entire basin, with sediment-gravity flows being one likely mechanism for sediment delivery to deep basins. Results collectively suggest that both marine basins are excellent natural sediment traps. Comparison of accumulation rates from 137Cs and 210Pb suggest that sediment fluxes to Nachvak Fjord may have decreased slightly over the past ∼130 years.
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Michaelovitch de Mahiques, Michel, Roberto Violante, Paula Franco-Fraguas, Leticia Burone, Cesar Barbedo Rocha, Leonardo Ortega, Rosangela Felicio dos Santos, Bianca Sung Mi Kim, Rubens Cesar Lopes Figueira e Marcia Caruso Bícego. "Control of oceanic circulation on sediment distribution in the southwestern Atlantic margin (23 to 55° S)". Ocean Science 17, n.º 5 (15 de setembro de 2021): 1213–29. http://dx.doi.org/10.5194/os-17-1213-2021.
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Abstract. In this study, we interpret the role played by ocean circulation in sediment distribution on the southwestern Atlantic margin using radiogenic Nd and Pb isotopes. The latitudinal trends for Pb and Nd isotopes reflect the different current systems acting on the margin. The utilization of the sediment fingerprinting method allowed us to associate the isotopic signatures with the main oceanographic features in the area. We recognized differences between Nd and Pb sources to the Argentinean shelf (carried by the flow of Subantarctic Shelf Water) and slopes (transported by deeper flows). Sediments from Antarctica extend up to the Uruguayan margin, carried by the Upper and Lower Circumpolar Deep Water. Our data confirm that, for shelf and intermediate areas (the upper 1200 m), the transfer of sediments from the Argentinean margin to the north of 35∘ S is limited by the Subtropical Shelf Front and the basin-wide recirculated Antarctic Intermediate Water. On the southern Brazilian inner and middle shelf, it is possible to recognize the northward influence of the Río de la Plata sediments carried by the Plata Plume Water. Another flow responsible for sediment transport and deposition on the outer shelf and slope is the southward flow of the Brazil Current. Finally, we propose that the Brazil–Malvinas Confluence and the Santos Bifurcation act as boundaries of geochemical provinces in the area. A conceptual model of sediment sources and transport is provided for the southwestern Atlantic margin.
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Hahn, Jens, Thanh Bui, Mathias Kessler, Collin J. Weber, Thomas Beier, Antje Mildenberger, Martina Traub e Christian Opp. "Catchment Soil Properties Affect Metal(loid) Enrichment in Reservoir Sediments of German Low Mountain Regions". Applied Sciences 12, n.º 5 (22 de fevereiro de 2022): 2277. http://dx.doi.org/10.3390/app12052277.
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Sediment management is a fundamental part of reservoir operation, but it is often complicated by metal(loid) enrichment in sediments. Knowledge concerning the sources of potential contaminants is therefore of important significance. To address this issue, the concentrations and the mobile fractions of metal(loid)s were determined in the sediments and the respective catchment areas of six reservoirs. The results indicate that reservoirs generally have a high potential for contaminated sediment accumulation due to preferential deposition of fine particles. The median values of the element-specific enrichment factor (EF) demonstrates slight enrichments of arsenic (EF: 3.4), chromium (EF: 2.8), and vanadium (EF: 2.9) for reservoir sediments. The enrichments of cadmium (EF: 8.2), manganese (EF: 3.9), nickel (EF: 4.8), and zinc (EF: 5.0) are significantly higher. This is enabled by a diffuse element release from the soils into the impounded streams, which is particularly favored by soil acidity. Leaching from the catchment soils partially enriches elements in stream sediments before their fine-grained portions in particular are deposited as reservoir sediment. We assume that this effect is of high relevance especially for reservoirs impounding small streams with forested catchments and weakly acid buffering parent material of soil formation.
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Khalilivavdareh, Sohrab, Ali Shahnazari e Amirpouya Sarraf. "Spatio-Temporal Variations of Discharge and Sediment in Rivers Flowing into the Anzali Lagoon". Sustainability 14, n.º 1 (4 de janeiro de 2022): 507. http://dx.doi.org/10.3390/su14010507.
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In the last few years, trend identification has become an important issue in hydrological time-series analyses; it is also a difficult task, due to the variety of models and the impact of climate change on the river flow regime. Due to the vital importance of the Anzali Lagoon to the environment of the region, and the threat to its health caused by the volume or amount of inlet sediments, we decided to study the changes in flow and sediment in the rivers flowing into the Anzali Lagoon. For the present study, the long-term monthly, seasonal, and annual sediment and discharge data of seven stations were obtained during the period 1985–2019. According to the available information, the trend of sediment load variation was investigated at different time scales. In this study, the Mann–Kendall statistical test, the double-mass curve, and performance fitting were used to assess the seasonal and annual trends in sediment and river flow. The results showed that at Aghamahale station, the low relationship between discharge and sediment compared with that at other stations was due to the low slope and constant water of the Behmbar River, which caused the sediments to settle and decreased their carrying rate. Moreover, Nokhaleh station had the largest share of sediment transfer to the lagoon during 2002–2012. Sediment details also show that the highest amount of sediment in all stations occurred in non-crop seasons—i.e., from October to January—and was directly dependent on the amount of rainfall in these areas. The results of the sediment analysis also indicate that the discharge and the subsequent sediment loads from upstream to downstream were high over the summer. Furthermore, the rivers downstream demonstrated springtime peaks in the sediment loads and discharge, probably owing to snow melting.
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Wakeham, S. G., e A. P. McNichol. "Transfer of organic carbon through marine water columns to sediments – insights from stable and radiocarbon isotopes of lipid biomarkers". Biogeosciences 11, n.º 23 (10 de dezembro de 2014): 6895–914. http://dx.doi.org/10.5194/bg-11-6895-2014.
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Abstract. Compound-specific 13C and 14C compositions of diverse lipid biomarkers (fatty acids, alkenones, hydrocarbons, sterols and fatty alcohols) were measured in sinking particulate matter collected in sediment traps and from underlying surface sediments in the Black Sea, the Arabian Sea and the Ross Sea. The goal was to develop a multiparameter approach to constrain relative inputs of organic carbon (OC) from marine biomass, terrigenous vascular-plant and relict-kerogen sources. Using an isotope mass balance, we calculate that marine biomass in sediment trap material from the Black Sea and Arabian Sea accounted for 66–100% of OC, with lower terrigenous (3–8%) and relict (4–16%) contributions. Marine biomass in sediments constituted lower proportions of OC (66–90%), with consequentially higher proportions of terrigenous and relict carbon (3–17 and 7–13%, respectively). Ross Sea data were insufficient to allow similar mass balance calculations. These results suggest that, whereas particulate organic carbon is overwhelmingly marine in origin, pre-aged allochthonous terrigenous and relict OC become proportionally more important in sediments, consistent with pre-aged OC being better preserved during vertical transport to and burial at the seafloor than the upper-ocean-derived marine OC.
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Kummert, Mario, e Reynald Delaloye. "Regional-scale inventory of periglacial moving landforms connected to the torrential network system". Geographica Helvetica 73, n.º 4 (14 de dezembro de 2018): 357–71. http://dx.doi.org/10.5194/gh-73-357-2018.
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Abstract. When connected to torrential channels, periglacial moving landforms (including rock glaciers, push moraines and high-altitude landsliding masses) may constitute important active sediment sources for gravitational and torrential transfer processes such as debris flows. However, still very little is known about the location and the number of such types of sedimentary connection in given regions, as well as about the typical sediment transfer rates that can be expected. Therefore, this contribution aims at (i) describing a new methodology developed to identify and characterize moving landforms connected to the torrential network system at a regional scale and (ii) presenting the results yielded from the application of this method in a 2000 km2 region in the southwestern Swiss Alps. The developed approach is based on the analysis of simple data such as a high-resolution digital elevation model (DEM), time series of aerial images and a slope movement inventory. The approach allowed both the fast identification of moving landforms connected to torrential channels and the estimation of annual sediment transfer rates for these inventoried landforms. In the study region, results showed that such types of sedimentary connection appeared to be rather rare. Results also showed that most connected moving landforms were characterized by relatively low sediment transfer rates (<500 m3 yr−1) but several sites were identified as transferring large amounts of sediment into the torrents (>1000 m3 yr−1). As sediment transfer rates depend on the kinematical behavior of the landforms, values calculated may change in regard to the evolution of the surface velocities, which are currently generally increasing in the European Alps. When connected to torrents, periglacial moving landforms may thus represent substantial active sources of sediments for the development of debris flows and should be considered in the management of torrential catchments.
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De La Fuente, Maria, Jean Vaunat e Héctor Marín-Moreno. "Modelling Methane Hydrate Saturation in Pores: Capillary Inhibition Effects". Energies 14, n.º 18 (7 de setembro de 2021): 5627. http://dx.doi.org/10.3390/en14185627.
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Experimental and field observations evidence the effects of capillarity in narrow pores on inhibiting the thermodynamic stability of gas hydrates and controlling their saturation. Thus, precise estimates of the gas hydrate global inventory require models that accurately describe gas hydrate stability in sediments. Here, an equilibrium model for hydrate formation in sediments that accounts for capillary inhibition effects is developed and validated against experimental data. Analogous to water freezing in pores, the model assumes that hydrate formation is controlled by the sediment pore size distribution and the balance of capillary forces at the hydrate–liquid interface. To build the formulation, we first derive the Clausius–Clapeyron equation for the thermodynamic equilibrium of methane and water chemical potentials. Then, this equation is combined with the van Genuchten’s capillary pressure to relate the thermodynamic properties of the system to the sediment pore size distribution and hydrate saturation. The model examines the influence of the sediment pore size distribution on hydrate saturation through the simulation of hydrate formation in sand, silt, and clays, under equilibrium conditions and without mass transfer limitations. The results show that at pressure–temperature conditions typically found in the seabed, capillary effects in very fine-grained clays can limit the maximum hydrate saturation below 20% of the host sediment porosity.
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Darricau, Louise, Abdellatif Elghali, Patrick Martel e Mostafa Benzaazoua. "Evaluation of the Anthropogenic Metal Pollution at Osisko Lake: Sediments Characterization for Reclamation Purposes". Applied Sciences 11, n.º 5 (5 de março de 2021): 2298. http://dx.doi.org/10.3390/app11052298.
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The anthropogenic pollution of lake ecosystems by human activities (e.g., mining industries) is recognized as a serious issue. The Osisko urban lake located in Rouyn-Noranda (Quebec, Canada) was used partially as a waste disposal facility for many decades, causing a heavy pollution. The main undertakings of this study are (i) assessing the mineralogical and geochemical properties of lake Osisko sediments, and (ii) studying the pollution that occurred within lake water due to the sediments’ reactivity. Water and sediments across the lake were collected in different sensitive locations. Within the sediment samples, two parts were distinguished: a small layer of black vase over grey sediments. The black vase resembled organic matter while the gray sediment seemed close to clean lake sediments. The collected samples were characterized for their physical (particle size distribution, specific gravity and specific surface area), chemical (minor and major elements as well as total sulfur and carbon) and mineralogical (X-ray diffraction and scanning electron microscope) properties. Additionally, the reactivity of sediments was studied using weathering cells to quantify chemical species leaching and their releasing rates. The results showed that the vase was the only contaminated part with high concentrations of sulfur and metals such as copper, zinc and iron. Geochemical data showed that the composite sample and the vase potentially cause contaminated acid drainage if they are exposed to atmospheric conditions. Indeed, the pH values of the leachates from both samples were between 4 and 6, while those corresponding to sediments remained around circumneutral values. Quantitatively, the contaminant release from the tested samples was variable. Indeed, the Fe cumulative concentrations were around 200, 80 and 20 mg/kg for the vase, composite and sediment samples, respectively. Similarly, the Zn cumulative concentrations were around 4500, 4200, and below the detection limit for vase, composite and sediment samples, respectively. The same tendency was observed for Cu, S, and Fe. Thus, sediments within Osisko lake present a risk for water contamination if they are resuspended or dredged out of the lake. Consequently, they should be stabilized before their disposal. The samples’ high Cu contents also offer the possibility of their reprocessing.