Segui questo link per vedere altri tipi di pubblicazioni sul tema: Surface sediment.
Articoli di riviste sul tema "Surface sediment"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 articoli di riviste per l'attività di ricerca sul tema "Surface sediment".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi gli articoli di riviste di molte aree scientifiche e compila una bibliografia corretta.
1
Suryono, Chrisna Adhi, Ibnu Pratikto e Ajeng Rusmaharani. "Logam Berat Anthropogenik Pb dan Cu pada Lapisan Sedimen Permukaan dan Dasar Muara Sungai di Kota Semarang, Jawa Tengah Indonesia". Jurnal Kelautan Tropis 22, n. 1 (13 aprile 2019): 87. http://dx.doi.org/10.14710/jkt.v22i1.3223.
Testo completoAbstract (sommario):
Semarang coastal areas as specially on river down stream have been develop to industrial, dumpping areas and human settlement. Its will be caused increasing sedimentation and anthropogenic heavy metals accumulation in sediments. In order to assess Pb, and Cu on diferent layers of sediments on three down stream rivers on Semarang, samples of surface and bed sediment were collected for analyzed by ICPMS. The result showed that the heavy metal of Pb on bed layer was higher than Pb on surface sediment, on the other hand Cu on surface sediment was higher than Cu on bed sediments. Unfraternally the heavy metal concentration on surface and beds sediments they do not correlation with totals organic carbon and combination silt and clay in sediment on three down stream rivers on Semarang. Wilayah pesisir Semarang terutama di daerah muara sungai telah berkembang menjadi kawasan industri, penimbunan dan hunian. Hal tersebut menyebabkan peningkatan sedimentasi dan akumulasi antropogenik logam berat dalam sedimen. Untuk mengetahui logam berat Pb dan Cu dalam permukaan dan dasar sedimen di tiga muara sungai Semarang. Maka sampel pada permukaan dan dasar sedimen diambil dan dianalisa dengan ICPMS. Hasil pengukuran menunjukan bahwa konsentrasi logam Pb pada lapisan dasar lebih tinggi dari pada lapisan permukaan sedimen, sebaliknya konsentrasi logam Cu pada lapisan permukaan lebih tinggi dari pada lapisan dasar sedimen. Namun keseluruhan antropogenik logam berat Pb dan Cu pada lapisan permukaan maupun bawah sedimen tidak ada korelasinya dengan kandungan total bahan organik karbon dan kombinasi antara silt dan clay dalam sedimen di ketiga mura sungai di Semarang.
2
Kamiludin, Udaya, e Yudi Darlan. "KARAKTERISTIK PASIR DI PANTAI DAN LEPAS PANTAI BINUANGEUN, LEBAK-BANTEN". JURNAL GEOLOGI KELAUTAN 11, n. 2 (16 febbraio 2016): 79. http://dx.doi.org/10.32693/jgk.11.2.2013.235.
Testo completoAbstract (sommario):
Pasir merupakan sesuatu penomena yang menarik karena padanya tersimpan misteri bagaimana partikel itu terendapkan sesuai dengan lingkungannya, apakah merupakan pasir pada lingkungan marin, pantai atau sungai. Untuk mengetahui lingkungan pengendapan tersebut maka dilakukan identifikasi karakteristik pasirnya. Metoda penelitan meliputi pengambilan contoh, analisis besar butir, klasifikasi nomenklatur sedimen dan parameter statistik. Klasifikasi nomenklatur sedimen pada endapan sedimen permukaan dasar laut, gisik pasir, tanggul gisik dan endapan sungai aktif didapat pasir sebanyak, masing masing 19, 35, 15 dan 3 percontoh. Ke empat jenis endapan mempunyai ukuran butir rata-rata (mean) relatif seragam, yaitu pasir halus (2 Φ - 3 Φ). Begitu juga ukuran pasirnya berupa pasir halus dengan kurva distribusi persen berat fluktuatif. Perbedaan terlihat pada ukuran pasir sedimen permukaan dasar laut dan sedimen sungai aktif, selain pasir halus hadir pula pasir menengah (1 Φ - 2 Φ). Klasifikasi lingkungan pasir memperlihatkan bahwa ke empat endapan mempunyai kesesuaian lingkungan pengendapan disertai adanya muatan partikel yang mengkasar dan menghalus dengan bentuk kurtosis leptokurtik dan platikurtik monomodal. Sumber batuan asal sedimen diduga berasal dari hasil abrasi batugamping terumbu yang tersingkap di pantai bagian tengah daerah penelitian dan pengerjaan ulang batuan gunungapi dan batuan sedimen asal volkanik yang umum tersingkap di utara daerah penelitian.
Kata Kunci : Sedimen permukaan dasar laut, gisik pasir, tanggul gisik, sedimen sungai aktif, lingkungan pengendapan pasir, sumber batuan.
Sand sediment is something interesting phenomenon because the sand is stored in the mystery of how the sand particles sedimented according to the deposition environment, what is the sand that was deposited in marine, beach or river environment. The identification of sand sediment characteristic is used for the determination of depositional environment. Study methods include sediment sampling, grain size analysis of sediment, sediment nomenclature classification and computing the statistical parameters. Sediment nomenclature classification results on the seafloor surface sediment, sand beach sediment, berm sediment and active stream sediment derived as much sand sediment types, respectively 19, 35, 15 and 3 samples. The four types of sediment deposition that has mean is relatively uniform, which falls on the fine sand (Φ 2 - Φ 3). While the size of sand fall in the fine sand with fluctuating weight percent distribution curve. The difference was in the size of the sand on the sea floor sediments and active stream sediments, in addition to fine sand also present medium sand (Φ1 - Φ2). Sand environment classification showed that all four types of the sediments have suitability depositional environment be accompanied excess coarse and fine particles with curved kurtosis leptokurtic and platykurtic monomodal. Source rocks of the sediments probably derived from the abrasion of coralreef limestone exposed in the central coast of study area and rework volcanic rocks and sedimentary rocks of volcanic origin are commonly exposed in the northern of study area.
Key words: Seafloor surface sediment, sand beach, berm, active stream sediment, sand depositional environment, source rocks.
3
Rosa, Kátia Kellem da, Rosemary Vieira e Jefferson Cardia Simões. "Identificação de Mudanças Ambientais Através da Caracterização Sedimentar e Investigação de Processos Glaciogênicos e Paraglaciais no Ambiente Glacial da Geleira Wanda, Ilha Rei George, Antártica (Identification of Environmental Change Through...)". Revista Brasileira de Geografia Física 6, n. 1 (17 luglio 2013): 029. http://dx.doi.org/10.26848/rbgf.v6i1.232807.
Testo completoAbstract (sommario):
Este estudo objetiva identificar as características sedimentares associadas aos depósitos glaciogênicos e sedimentos com modificação por processos não glaciais na área proglacial da geleira Wanda, Ilha Rei George, Antártica. A metodologia foi desenvolvida através de atividades de campo realizadas durante a estação de verão em 2007, 2010 e 2011. Os sedimentos foram analisados para determinar a distribuição granulométrica e características morfoscópicas. Este estudo apresenta resultados de interpretações dos sedimentos coletados na proglacial da geleira Wanda. A análise sedimentar possibilita a distinção de sedimentos glaciogênicos e dos sedimentos modificados por atividade paraglacial, podendo evidenciar mudanças ambientais em decorrência do aumento da temperatura atmosférica superficial e da precipitação líquida. AbstractThis study arms identify sediment characteristics related to glaciogenics deposits and modification with paraglacial processes in Wanda Glacier proglacial area, King George Island, Antarctica. The methodology was developed through field activities performed during summers in 2007, 2010 and 2011. The sediments were analyzed to determine the particle size distribution and morphoscopical characteristics. This study presents results of the samples sediment interpretation in Wanda Glacier proglacial area. The sediment analyses provided the discrimination of the glaciogenicssediments and paraglacial modified sediments, and was evidence for environment changes in the study area due to the increase surface atmospheric temperature and liquid precipitation.
4
Inamdar, Shreeram, Nathan Sienkiewicz, Alyssa Lutgen, Grant Jiang e Jinjun Kan. "Streambank Legacy Sediments in Surface Waters: Phosphorus Sources or Sinks?" Soil Systems 4, n. 2 (11 maggio 2020): 30. http://dx.doi.org/10.3390/soilsystems4020030.
Testo completoAbstract (sommario):
Streambank legacy sediments can contribute substantial amounts of sediments to Mid-Atlantic waterways. However, there is uncertainty about the sediment-bound P inputs and the fate of legacy sediment P in surface waters. We compared legacy sediment P concentrations against other streambank sediments and upland soils and evaluated a variety of P indices to determine if legacy sediments are a source or sink of P to surface waters. Legacy sediments were collected from 15 streambanks in the mid-Atlantic USA. Total P and M3P concentrations and % degree of phosphorus saturation (DPS) values for legacy sediments were lower than those for upland soils. % DPS values for legacy sediments were below the water quality threshold for P leaching. Phosphorus sorption index (PSI) values for legacy sediments indicated a large capacity for P sorption. On the other hand, equilibrium phosphorus concentration (EPC0) for legacy sediments suggested that they could be a source or a sink depending on stream water P concentrations. Anoxic conditions resulted in a greater release of P from legacy sediments compared to oxic conditions. These results suggest that legacy sediment P behavior could be highly variable and watershed models will need to account for this variability to reliably quantify the source-sink behavior of legacy sediments in surface waters.
5
Najamuddin, Najamuddin, Irmalita Tahir, Rustam E. Paembonan e Inayah Inayah. "Pengaruh Karakteristik Sedimen terhadap Distribusi dan Akumulasi Logam Berat Pb dan Zn di Perairan Sungai, Estuaria, dan Pantai". Jurnal Kelautan Tropis 23, n. 1 (13 febbraio 2020): 1. http://dx.doi.org/10.14710/jkt.v23i1.5315.
Testo completoAbstract (sommario):
The purpose of the study was to analyze the effect of surface sediment characteristics including texture, organic carbon content, and redox potential of sediments on the distribution and accumulation of heavy metals Pb and Zn in three different water zones of each river, estuary and coast. Sediment texture was determined by pipette method, organic carbon content in sediments using Walkley and Black method, redox potential of sediments measured by Eh Meter, and concentrations of heavy metals Pb and Zn in sediments with Atomic Absorption Spectrophotometer with graphite furnace system. The results showed that the distribution and accumulation pattern of heavy metals Pb was similar to Zn where the highest concentration was in the coastal waters zone and the lowest was in the estuary waters zone. Sediment texture in the three zones of the dominant was sand. The percentage of organic carbon content in sediments ranges from 1.63-3.25% and the sediment redox potential was classified as reduction and transition zones. The parameters of texture, organic carbon content, and sediment redox potential have a significant influence on the distribution and accumulation of heavy metals Pb and Zn in sediments in all three water zones. Tujuan penelitian adalah menganalisis pengaruh karakteristik sedimen permukaan meliputi tekstur, kandungan karbon organik, dan potensial redoks sedimen terhadap distribusi dan akumulasi logam berat Pb dan Zn di tiga zona perairan berbeda masing-masing sungai, estuaria, dan pantai. Tekstur sedimen ditentukan dengan metode pipet, kandungan karbon organik dalam sedimen dengan metode Walkley and Black, potensial redoks sedimen diukur dengan Eh Meter, dan konsentrasi logam berat Pb dan Zn dalam sedimen dengan Spektrofotometer Serapan Atom dengan sistem graphite furnace. Hasil penelitian menunjukkan pola distribusi dan akumulasi logam berat Pb serupa dengan Zn dimana konsentrasi tertinggi di zona perairan pantai dan terendah zona perairan estuaria. Tekstur sedimen pada tiga zona perairan dominan berupa fraksi pasir (sand). Persentase kandungan karbon organik dalam sedimen berkisar antara 1,63-3,25 % dan nilai potensial redoks sedimen termasuk kategori zona reduksi dan transisi. Parameter tekstur, kandungan karbon organik, dan potensial redoks sedimen memberikan pengaruh nyata terhadap distribusi dan akumulasi logam berat Pb dan Zn dalam sedimen pada ketiga zona perairan.
6
Hernawan, Undang, e Kris Budiono. "KARAKTERISTIK DAN DISTRIBUSI LUMPUR SIDOARJO SEPANJANG SUNGAI, ESTUARI DAN PERAIRAN PORONG". JURNAL GEOLOGI KELAUTAN 11, n. 2 (16 febbraio 2016): 91. http://dx.doi.org/10.32693/jgk.11.2.2013.234.
Testo completoAbstract (sommario):
Semburan lumpur Sidoarjo (Lusi) di daerah Porong menambah fungsi Sungai Porong menjadi sarana untuk mengalirkan lumpur ke arah laut, karena kemampuan tanggul – tanggul penghalang di sekitar lokasi semburan sangat terbatas. Kondisi ini berdampak pula terhadap terbawanya lumpur lapindo ke perairan Porong. Penelitian ini bermaksud untuk mengetahui sebaran sedimen di sungai, muara dan perairan sekitar Porong terutama yang bersumber dari luapan lumpur Sidoarjo.
Materi yang digunakan dalam penelitian ini adalah sebanyak 30 sampel sedimen hasil sampling yang diambil di lokasi sungai – muara sungai Porong dan 30 sampel sedimen permukaan dasar laut di perairan sekitar muara sungai Porong.
Distribusi umum sebaran sedimen di perairan Porong menunjukkan sedimen lumpur ditemukan di pinggir sungai dan sedimen pasir ditemukan di bagian tengah sungai. Distribusi umum sedimen dasar perairan di sekitar muara Porong berupa pasir, lempung dan lempung lanau pasiran. Hasil analisis mikroskopik dan SEM menunjukkan bahwa sedimen yang berasal dari luapan lumpur Sidoarjo ditemukan di sepanjang aliran Sungai Porong sampai muara, namun belum ditemukan di perairan luar sekitar muara Porong. Sedimen Lusi yang sampai ke muara Porong berukuran butir sampai 2,5 mikron. Deskripsi megaskopis menunjukkan sedimen Lusi pasir - kerikil umumnya berbentuk pipih (halus– agak halus). Hasil SEM menunjukkan bahwa sedimen yang berasal dari lumpur Sidoarjo umumnya seragam dan didominasi berupa smectite. Berbeda dengan sedimen sungai, hasil SEM yang diperoleh dari sampel laut yang menunjukkan sedimennya beragam, berupa montmorilonite, kaolinite dan illite.
Kata Kunci : Sedimen, Porong, lumpur Sidoarjo
The Sidoarjo mudflow in the Porong area increases the functions of Porong River as media to drain the muds towards the sea, because the ability of embankments in the area as a barrier is very limited. This condition intends to determine the presence and distribution of sediment in rivers, estuaries and waters originating from the Lusi mudflow.
The materials used in this study are the sediment sampling results as many as 30 samples taken from the river and off the river mouth and 30 samples of sea surface sediments in the surrounding waters.
General distribution of sediments in the Porong River shows the form of mud sediments are generally found in the riverside and sandy sediment found in the middle of the river, while the distribution of sediments in waters Porong form of sand, clay and sandy silt clay. The results of microscopic and SEM analysis showed that the sediments derived from the Lusi mudflow found along Porong River till estuaries, but they have not reach surrounding water of Porong estuary. The Lusi sediment that reached the estuary Porong sized to 2.5 micron. General megascopic description show the shape of the Lusi sediment as sand-gravel is a flat-shaped (rounded - sub rounded). SEM results showed that the sediments derived from the Lusi is generally uniform and dominated by smectite. In contrast to stream sediments, the SEM results obtained from marine sediment samples show a variety of sediments, in the form of montmorillonite, caolinite and illite.
Key words: Sediment, Porong, Sidoarjo, Mud Overflow (Lusi)
7
Owens, Edward H., Gary A. Sergy e John Harper. "THE BEHAVIOUR AND TREATMENT OF ORIMULSION® BITUMEN STRANDED ON PEBBLE, COBBLE OR IMPERMEABLE SUBSTRATE SHORELINES". International Oil Spill Conference Proceedings 2005, n. 1 (1 maggio 2005): 919–24. http://dx.doi.org/10.7901/2169-3358-2005-1-919.
Testo completoAbstract (sommario):
ABSTRACT Bitumen from an Orimulsion® spill can strand on shorelines in the form or dispersed bitumen or coalesced bitumen. Wetness of the shoreline substrate is an important factor in the adhesion of the bitumen and this in turn significantly effects selection of a treatment technique. Stranded bitumen on the surface of a shoreline that remains wet and/or non adhesive can be removed relatively easily by a combination of low-pressure washing, flooding, and recovery, or by manual and mechanical removal techniques. When stranded on dry surfaces or when interfacial surfaces dry, then the bitumen will strongly adhere to shoreline substrates either in the form of thin coatings or thick deposits of bitumen that are difficult to remove. Heated, high-pressure seawater washing is effective but must be accompanied by flooding to minimize penetration into coarse sediments. Sediment relocation, sediment removal, wet tilling and natural recovery techniques are appropriate techniques under specific oiling conditions. Temperature greatly effects bitumen penetration into sediments. Where bitumen coatings or deposits form in subsurface sediments then treatment becomes extremely difficult, requiring sediment removal or techniques to bring oiling surface sediments to the surface for treatment.
8
Junakova, N., J. Junak e M. Balintova. "The effect of physicochemical properties of bottom sediments on nitrogen and phosphorus sorption". IOP Conference Series: Materials Science and Engineering 1252, n. 1 (1 settembre 2022): 012059. http://dx.doi.org/10.1088/1757-899x/1252/1/012059.
Testo completoAbstract (sommario):
Abstract River and reservoir bottom sediments are characterized by their physical and chemical properties, which affect the quality of water and deposited sediments in reservoirs. The grain composition of sediments is their fundamental property that determines the detachment, transport and sedimentation of sediments. In addition to understanding the dynamics of transport and distribution of particles in the watershed, the granularity is closely related to the mineral and chemical composition of the sediment and plays an important role in terms of its ability to bind contaminants. Other important property of sediment includes the specific surface area, which determines the nature of sediment surface reactions and influences ecosystem level, biological processes. This study investigates sediment properties, including physical properties such as grain-size distribution, specific surface area, organic matter and chemical composition, and their reflections on nitrogen and phosphorus adsorption by the sediments deposited in the small water reservoir. The results clearly indicate the dependence of the content of nutrients (nitrogen and phosphorus) in reservoir sediments on their grain size and specific surface area.
9
Moreton, Steven G., Gunhild C. Rosqvist, Sarah J. Davies e Michael J. Bentley. "Radiocarbon Reservoir Ages from Freshwater Lakes, South Georgia, Sub-Antarctic: Modern Analogues from Particulate Organic Matter and Surface Sediments". Radiocarbon 46, n. 2 (2004): 621–26. http://dx.doi.org/10.1017/s0033822200035669.
Testo completoAbstract (sommario):
Lake sediments have the potential to preserve proxy records of past climate change. Organic material suitable for radiocarbon dating often provides age control of such proxy records. Six shallow freshwater lakes on the sub-Antarctic island of South Georgia were investigated for carbon reservoir effects that may influence age-depth profiles from lake sediment records in this important region. Paired samples of particulate organic matter (POM) from the water column and surface sediment (bulk organic carbon) were analyzed by accelerator mass spectrometry 14C. POM in 4 lakes was found to be in equilibrium with the atmosphere (~107% modern), whereas 2 lakes showed significant depletion of 14C. In each lake, the surface sediment ages were older than the paired POM age. Surface sediment ages showed a much greater range of ages compared to the equivalent POM ages, even for lakes located in close proximity. We conclude that sediment disturbance during coring, bioturbation, and periodic resuspension of sediments are likely factors causing the difference in the apparent age of surface sediments.
10
Spencer, K. L., e C. L. MacLeod. "Distribution and partitioning of heavy metals in estuarine sediment cores and implications for the use of sediment quality standards". Hydrology and Earth System Sciences 6, n. 6 (31 dicembre 2002): 989–98. http://dx.doi.org/10.5194/hess-6-989-2002.
Testo completoAbstract (sommario):
Abstract. Total metal concentrations in surface sediments and historically contaminated sediments were determined in sediment cores collected from three estuaries (Thames, Medway and Blackwater) in south-east England. The partitioning behaviour of metals in these sediments was also determined using a sequential extraction scheme. These data were then compared with sediment quality values (SQVs) to determine the potential ecotoxicological risk to sediment dwelling organisms. When total metal concentrations in surface sediments are examined, no risk to biota in any of the estuaries is indicated. However, when historically contaminated sediments at depth are also considered, risks to biota are apparent and are greatest for the Thames, followed by the Medway and then the Blackwater. This suggests that regulatory authorities should examine vertical metal profiles, particularly in estuaries that are experiencing low sediment accumulation rates where historically contaminated sediments are in the shallow sub-surface zone and where erosion or dredging activities may take place. When metal partitioning characteristics are also considered, the risk to biota is comparable for the Medway and the Blackwater with the potentially bioavailable fraction presenting no ecotoxicological risk. Conversely, over 70% of metals are labile in the Thames Estuary sediments and toxic effects are probable. This suggests that the application of SQVs using total sediment metal concentrations may over- or under-estimate the risk to biota in geochemically dissimilar estuarine sediments. Keywords: sediment quality values, estuarine sediments, metal contamination, partitioning, sequential extraction
11
Cook, Nancy H., e Peter G. Wells. "Toxicity of Halifax Harbour Sediments: an Evaluation of the Microtox® Solid-Phase Test". Water Quality Research Journal 31, n. 4 (1 novembre 1996): 673–708. http://dx.doi.org/10.2166/wqrj.1996.037.
Testo completoAbstract (sommario):
Abstract Subtidal sediments were collected in Halifax Harbour, Nova Scotia, in July and August, 1992, to study sediment toxicity and hazards near the proposed location of a sewage treatment plant and outfall. A set of 110 samples from eight stations was evaluated. Interstitial water from surface (0-2 cm) and subsurface (2-4 cm) sediments was analyzed by the Microtox® 100% toxicity test protocol. The sediment particles were analyzed using the Microtox® solid-phase test. Interstitial water from surface and subsurface sediments from all stations was usually non-toxic, compared to a phenol standard. The mean 5 min-EC50 of surface sediments (n=57) was 5,433mg/L; the mean 5 min-EC50 of subsurface sediments (n=50) was 804 mg/L. Toxicity thresholds for the harbour sediments were compared with National Research Council marine analytical sediment reference materials and a selection of natural sediments, and ranked. An experiment with the marine reference sediments (certified for PAHs and trace metals) and their mixtures showed the ability of the solid-phase test to discriminate among different levels of contaminated sediments. Intra- and inter-sample variability in toxicity at different locations in relation to time, sediment depth, sediment properties, and types and concentrations of contaminants was evaluated by multivariate and PCA tech-niques. This laboratory-field study provided insights into the sensitivity, repro-ducibility, significance and discriminatory ability of the Microtox® solid-phase bioassay and its value in the study of complex natural sediment mixtures.
12
Liu, Yanguang, Chuanshun Li, Ramlan Bin Omar, Xuefa Shi, Hui Zhang e Noraswana Nor Faiz. "Sediment Sources and Dispersion on the Western Sunda Shelf, Malay Peninsula, Southern South China Sea". Water 13, n. 20 (11 ottobre 2021): 2823. http://dx.doi.org/10.3390/w13202823.
Testo completoAbstract (sommario):
Thirty-nine surface sediment samples collected from the western Sunda Shelf off the Malay Peninsula (WSSMP) in the southern South China Sea (SCS) were analysed for grain size, major and trace elemental compositions, and light/heavy mineral contents to trace the sediment sources and their transport mechanisms in the study area. In the WSSMP, the surface sediments are relatively poorly sorted but transportable. A principal component analysis of 37 elements and grain size fractions indicates that the surface sediments can be grouped into four major assemblages in the study area. Integrating with the light/heavy minerals data in the 63–125 μm fractions of the surface sediment samples, to better trace the sediment sources of the coarse-grained components in the marine environment, the study area can be further divided into four sediment provinces. Province I is located in the northwestern part of the study area. The concentrations of TiO2, Na2O, garnet, siderite, and glauconite in Province I were higher than in the other provinces. The main sediment source for this province originated from the Kelantan River and the Gulf of Thailand transported by the northeastern monsoon current. Province II is located offshore of the Pahang and Endau Rivers. The percentages of TiO2, rare earth elements, Al2O3, quartz, plagioclase, hypersthene, and magnetite in the surface sediments were typically higher in this province than in the other provinces. The Pahang and Endau rivers provide most of the sediments to this province, which are transported by southward coastal currents. Province III is located in the northeastern and eastern parts of the study area, where the coarse-grained sediment fraction had relatively high hornblende and biotite contents. Sediments in this province are mostly transported from the Mekong River during the northeastern monsoon. The other parts of the study area belong to Province IV, where the surface sediment elemental and mineral concentrations were mostly between those of the other three provinces. Therefore, we suggest that Province IV has a mixed source due to inputs from the surrounding rivers.
13
Weisbrod, Barbara, Susanna A. Wood, Konstanze Steiner, Ruby Whyte-Wilding, Jonathan Puddick, Olivier Laroche e Daniel R. Dietrich. "Is a Central Sediment Sample Sufficient? Exploring Spatial and Temporal Microbial Diversity in a Small Lake". Toxins 12, n. 9 (9 settembre 2020): 580. http://dx.doi.org/10.3390/toxins12090580.
Testo completoAbstract (sommario):
(1) Background: Paleolimnological studies use sediment cores to explore long-term changes in lake ecology, including occurrences of harmful cyanobacterial blooms. Most studies are based on single cores, assuming this is representative of the whole lake, but data on small-scale spatial variability of microbial communities in lake sediment are scarce. (2) Methods: Surface sediments (top 0.5 cm) from 12 sites (n = 36) and two sediment cores were collected in Lake Rotorua (New Zealand). Bacterial community (16S rRNA metabarcoding), Microcystis specific 16S rRNA, microcystin synthetase gene E (mcyE) and microcystins (MCs) were assessed. Radionuclide measurements (210Pb, 137Cs) were used to date sediments. (3) Results: Bacterial community, based on relative abundances, differed significantly between surface sediment sites (p < 0.001) but the majority of bacterial amplicon sequence variants (88.8%) were shared. Despite intense MC producing Microcystis blooms in the past, no Microcystis specific 16S rRNA, mcyE and MCs were found in surface sediments but occurred deeper in sediment cores (approximately 1950′s). 210Pb measurements showed a disturbed profile, similar to patterns previously observed, as a result of earthquakes. (4) Conclusions: A single sediment core can capture dominant microbial communities. Toxin producing Microcystis blooms are a recent phenomenon in Lake Rotorua. We posit that the absence of Microcystis from the surface sediments is a consequence of the Kaikoura earthquake two years prior to our sampling.
14
Zafra Mejía, Carlos Alfonso, Javier Temprano González e Iñaki Tejero Monzón. "Evaluating urban runoff pollution: sediments deposited on a road surface". Ingeniería e Investigación 29, n. 1 (1 gennaio 2009): 101–8. http://dx.doi.org/10.15446/ing.investig.v29n1.15149.
Testo completoAbstract (sommario):
The pollution caused by runoff water continues being a great problem in urban areas. Studying the behavior of sediments deposited on a road surface serves to determine the characteristics of their build-up during dry times and wash-off during rainy periods. It will also lead to establishing pollution control mechanisms associated with the sediment deposited on particular types of road surfaces. This paper presents data regarding the sediment accumulating on a road surface in the city of Torrelavega in northern Spain during a 65-day period, during which time 132 samples were collected. Two types of sediment collection samples were obtained: vacuumed dry samples (free load) and those swept up following vacuuming (fixed load). Sediment loading, particle size distribution and moisture were determined for each type of sample. The data showed that the sediment loading (gm-2) and vacuumed availability of the load which adhered most strongly to the surface (fixed load) increased with the number of dry days. Collected sediment particle size distribution tended to be finer with the increase in the number of dry days. <125 µm particle sizes presented the greatest rate of build-up during dry time and those which were <500 µm had the greatest susceptibility to being washed off during rain.
15
Ngo, Chi Kim Thi, Long Van Hoang, Binh Van Phan, Tinh Nguyen Trinh, Trung Tu Do, Hiep Huu Nguyen e Nghiem Van Dao. "The characteristics of the surface sediments in Co To island". Journal of Mining and Earth Sciences 61, n. 2 (29 aprile 2020): 33–40. http://dx.doi.org/10.46326/jmes.2020.61(2).04.
Testo completoAbstract (sommario):
552 grain size samples and 33 mineral quality defined samples have been collected in the Co To island, Tonkin Bay of Vietnam, to study the distribution and the sediment provenance. The field investigation method, the grain analysis, and the detrital composition examination method have been used to study the characteristics of the surface sediments in Co To island. The obtained results show that the surface sediments in the area consist of ten different fields, namely: sandy gravel, gravelly sand, sand, gravelly muddy sand, sand mixed gravel, muddy sand, gravelly mud mixed sand, silty sand, muddy sandy gravel, and sandy mud. The mineral component method shows that quartz is the main contain of the surface sediment (72,0÷90,6%), less rock detritus, felspat, mica, and very few of the shells. It is to confirm that the continent is the main primary material source of the study area. The distribution of the sediment is complicated. As the East-Southeast side of the research area, the sediment distribution following gravity way, coarse grain near the shore (gravel, sandy gravel,…), finer grain far off the shore (gravelly muddy sand, silty sand,…), choice level is very low. Which This is saying that the movement of sediment in the area is dominant, ; the flow energy is governed by the topography near the island and seafloor. In tMhe meanwhile, the west-northwest side, the topography of seafloor is the complicated, coarse sediment grains (gravel, sand), ); the roundness is bad, which is saying that the hydrodynamic flow there plays an important role in the sediment distribution.
16
Kamel, Nariman H. M. "The Behaviour of134Cs,60Co, and85Sr Radionuclides in Marine Environmental Sediment". Scientific World JOURNAL 2 (2002): 1514–26. http://dx.doi.org/10.1100/tsw.2002.290.
Testo completoAbstract (sommario):
This work describes experimental investigations and modelling studies on the sorption of radionuclides134Cs,60Co, and85Sr by certain marine sediments within Egypt. The chemical composition of the marine sediments was determined. The soluble salts were measured for the sediments and the concentrations of the released cations, Al3+, Fe3+, and Si4+, were measured for the sediment materials in 0.1 M NaClO4aqueous solution at different hydrogen ion concentrations. The two main factors that control the uptake of the radionuclides onto the sediment are the pH and the exchangeable capacities of the sediment materials. Surface complex model was used to estimate the surface charge densities and the electric surface potential of the marine sediment materials. These two parameters were calculated at the surface capacity sites of the sediment materials. The desorption of the adsorbed cations was determined by means of selective consecutive extraction tests using different chemical reagents including (1) 1 M MgCl2(pH 7), (2) 1 M ammonium oxalate (pH 3-5), (3) 0.04 M NH2OH,HCl in 25% acetic acid (pH 3-4), (4) H2O2in 5% HNO3(pH 2-3), and (5) digestion with nitric acid followed by hydrofluoric and perchloric acids (pH 2).
17
Searcy, Kristin E., Aaron I. Packman, Edward R. Atwill e Thomas Harter. "Deposition of Cryptosporidium Oocysts in Streambeds". Applied and Environmental Microbiology 72, n. 3 (marzo 2006): 1810–16. http://dx.doi.org/10.1128/aem.72.3.1810-1816.2006.
Testo completoAbstract (sommario):
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.
18
Tye, A. M., S. Chenery, M. R. Cave e R. Price. "Using 206/207Pb isotope ratios to estimate phosphorus sources in historical sediments of a lowland river system". Journal of Soils and Sediments 21, n. 1 (10 novembre 2020): 613–26. http://dx.doi.org/10.1007/s11368-020-02820-y.
Testo completoAbstract (sommario):
Abstract Purpose Engineering and dredging strategies to manage sediment, along with river-scouring, can reveal older sediments. These present a unique opportunity to assess past sources of phosphorus (P) inputs into river sediments. We used the sediment concentrations of P, lead (Pb) and 206/207Pb isotopes to produce ‘first-order’ estimates of the source (diffuse agricultural or sewage treatment) of phosphorus. Materials and methods Sediment cores (n = 30) were collected from the length of the non-tidal River Nene, a lowland river in eastern England. Cores were analysed for sediment elemental concentrations and Pb isotopes. Principal component analysis and linear regression modelling were used to assess the relationships between P, Pb and Pb isotopes. Monte-Carlo simulations and boot-strapping were undertaken to estimate, with 95% confidence intervals, the source of P in these sediments. Results and discussion Analysis of the relationships between PTotal, PbTotal and 206/207Pb isotope ratios suggested that sediments were deposited largely prior to the phasing out of tetra-ethyl Pb (PbBHT) from petrol. Regression models showed positive correlations between PTotal and PbTotal (R2 = 0.85). Principal component analysis suggested a strong sewage treatment signal for Pb and P enrichment. In the rural upper three water bodies, little sewage treatment work (STW)-derived P was found in the sediment, a consequence of limited STW input and greater sediment transport. In the more urbanised water bodies 4–6, ‘first-order estimates’ of STW P suggest that median concentrations were 30–40% of PTotal. Conclusions The strong relationships between Pb and P concentrations in river water provided the opportunity to use 206/207Pb isotope ratios to calculate ‘first-order’ estimates of the proportion of P released from STWs in the historical sediment. Understanding the sources of historical sediment P can be used to assess the success of current sediment management strategies and to base further mitigation measures. Results suggest that whilst much recent sediment P is removed, the legacy sediment remains to contribute P to the water body. Thus, options regarding the practical removal of these sediments and the extent to which this would improve water P status need to be assessed and balanced against options such as further decreasing soil P or STW P stripping.
19
Wang, H., X. Jia, Y. Li e W. Peng. "Selective deposition response to aeolian–fluvial sediment supply in the desert braided channel of the upper Yellow River, China". Natural Hazards and Earth System Sciences 15, n. 9 (2 settembre 2015): 1955–62. http://dx.doi.org/10.5194/nhess-15-1955-2015.
Testo completoAbstract (sommario):
Abstract. Rivers flow across aeolian dunes and develop braided stream channels. Both aeolian and fluvial sediment supplies regulate sediment transport and deposition in such cross-dune braided rivers. Here we show a significant selective deposition in response to both aeolian and fluvial sediment supplies in the Ulan Buh desert braided channel. The Ulan Buh desert is the main coarse sediment source for this desert braided channel, and the mean percentage of the coarser (> 0.08 mm) grains on the aeolian dunes surface is 95.34 %. The lateral selective deposition process is developed by the interaction between the flows and the aeolian–fluvial sediment supplies, causing the coarser sediments (> 0.08 mm) from aeolian sand supply and bank erosion to accumulate in the channel centre and the finer fluvial sediments (< 0.08 mm) to be deposited on the bar and floodplain surfaces, forming a coarser-grained thalweg bed bounded by finer-grained floodplain surfaces. This lateral selective deposition reduces the downstream sediment transport and is a primary reason for the formation of an "above-ground" river in the braided reach of the upper Yellow River in response to aeolian and fluvial sediment supplies.
20
Seleznev, Andrian, Ilia Yarmoshenko, Georgy Malinovsky, Daria Kiseleva, Ekaterina Ilgasheva, Anastasia Ryanskaya e Alexander Teterin. "Surface stormwater runoff in the formation of contemporary urban surface deposited sediments". E3S Web of Conferences 98 (2019): 07028. http://dx.doi.org/10.1051/e3sconf/20199807028.
Testo completoAbstract (sommario):
Surface runoff represents one of the major mechanism connecting sources, transport, deposition and storage of the particle matter in urban sediment cascade. The urban surface deposited sediment represents a medium for the transport and nonpoint source of pollution in cities. The study is aimed to characterize the role of surface stormwater runoff in accumulation of the contemporary surface deposited sediments in the urban environment taking to account the seasonal factor. The study was conducted on the example of residential area of Ekaterinburg, Russia. The role of the surface stormwater runoff in the formation of the urban surface deposited sediments was discussed. The snow and dirt mixture accumulates surface runoff and pollutants in it during the winter season in an urban area. A large supply of water accumulated in the snow cover during the cold period contributes to the formation of large volumes of snow-mud mixture during spring. The active snowmelt in the spring leads to the formation of snow-dirt sludge and transfer of the sedimentary material.
21
Satoh, Hisashi, Yoshiyuki Nakamura e Satoshi Okabe. "Influences of Infaunal Burrows on the Community Structure and Activity of Ammonia-Oxidizing Bacteria in Intertidal Sediments". Applied and Environmental Microbiology 73, n. 4 (22 dicembre 2006): 1341–48. http://dx.doi.org/10.1128/aem.02073-06.
Testo completoAbstract (sommario):
ABSTRACT Influences of infaunal burrows constructed by the polychaete (Tylorrhynchus heterochaetus) on O2 concentrations and community structures and abundances of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in intertidal sediments were analyzed by the combined use of a 16S rRNA gene-based molecular approach and microelectrodes. The microelectrode measurements performed in an experimental system developed in an aquarium showed direct evidence of O2 transport down to a depth of 350 mm of the sediment through a burrow. The 16S rRNA gene-cloning analysis revealed that the betaproteobacterial AOB communities in the sediment surface and the burrow walls were dominated by Nitrosomonas sp. strain Nm143-like sequences, and most of the clones in Nitrospira-like NOB clone libraries of the sediment surface and the burrow walls were related to the Nitrospira marina lineage. Furthermore, we investigated vertical distributions of AOB and NOB in the infaunal burrow walls and the bulk sediments by real-time quantitative PCR (Q-PCR) assay. The AOB and Nitrospira-like NOB-specific 16S rRNA gene copy numbers in the burrow walls were comparable with those in the sediment surfaces. These numbers in the burrow wall at a depth of 50 to 55 mm from the surface were, however, higher than those in the bulk sediment at the same depth. The microelectrode measurements showed higher NH4 + consumption activity at the burrow wall than those at the surrounding sediment. This result was consistent with the results of microcosm experiments showing that the consumption rates of NH4 + and total inorganic nitrogen increased with increasing infaunal density in the sediment. These results clearly demonstrated that the infaunal burrows stimulated O2 transport into the sediment in which otherwise reducing conditions prevailed, resulting in development of high NH4 + consumption capacity. Consequently, the infaunal burrow became an important site for NH4 + consumption in the intertidal sediment.
22
Rood, Kenneth M., e Edward J. Hickin. "Suspended-sediment concentration and calibre in relation to surface-flow structure in Squamish River estuary, southwestern British Columbia". Canadian Journal of Earth Sciences 26, n. 10 (1 ottobre 1989): 2172–76. http://dx.doi.org/10.1139/e89-183.
Testo completoAbstract (sommario):
Surface grabs of suspended sediments from boils and the background flow in Squamish Estuary revealed strong differences between the two environments. Boils exhibit higher sediment concentrations and larger particle sizes than the background flow. The higher sediment concentrations and larger grain sizes in boils are related to tidal phase, with maximum concentrations and sediment sizes occurring in the early decelerating phase of the tidal flow. Sediment concentrations and grain sizes in the background flow are comparatively invariant with tidal phase. Boils appear to play an important, if not dominant, role in suspending and transporting sand-sized sediments in Squamish Estuary.
23
Setiady, Deny, Udaya Kamiludin e Nienu Yayu Gerhaneu. "JENIS DAN SEBARAN SEDIMEN DI PERAIRAN PAPELA DAN SEKITARNYA, ROTE-NDAO, NUSA TENGGARA TIMUR". JURNAL GEOLOGI KELAUTAN 13, n. 3 (16 febbraio 2016): 153. http://dx.doi.org/10.32693/jgk.13.3.2015.270.
Testo completoAbstract (sommario):
Daerah Penelitian terletak di perairan Papela dan sekitarnya yang merupakan bagian dari Selat Rote yang secara administratif merupakan wilayah dari Kabupaten Rote-Ndao, Provinsi Nusa Tenggara Timur. Di daerah penelitian pada 40 lokasi telah dilakukan pengambilan sedimen dasar laut dengan pemercontoh comot, deskripsi megaskopis dan analisis besar butir. Penelitian bertujuan untuk mengetahui jenis sedimen, sebaran sedimen dan lingkungan pengendapannya. Berdasarkan hasil analisis besar butir nomenklatur sedimen di daerah penelitian dijumpai 4 jenis sedimen yaitu: kerikil, pasir, pasir lanauan, lanau pasiran dan lanau. Sebaran kerikil terdapat di dua tempat, yaitu di utara dan selatan tepian daerah penelitian.Sebaran pasir mencapai kurang lebih 30 % dari luas perairan penelitian, pasir lanauan menutupi kurang 5 % dari luas perairan penelitian, lanau pasiran mempunyai sebaran kurang lebih 30 % dari luas perairan daerah penelitian dan sebaran lanau terdapat di muka muara sungai bagian dalam Teluk Papela dengan tutupan kurang lebih 5 % dari luas perairan penelitian.Kata kunci Sedimen permukaan dasar laut, analisis besar butir, sebaran sedimen, perairan Papela The study area is located in Papela waters area and that is part of the Rote Strait, administratively is a region of Rote-Ndao regency, East Nusa Tenggara Province. The method of research conducted is sampling seafloor sediments, megaskopis description and analysis of the grain size. The study area is located in Papela waters area and that is part of the Rote Strait, administratively is a region of Rote-Ndao regency, East Nusa Tenggara Province. The method of research conducted is sampling seafloor sediments, megaskopis description and analysis of the grain size. The purpose of research is the grain size analysis of seabed surface sediment to determine the type of sediment, sediment distribution and depositional environment. Based on nomenklature sediment grain size analysis result in the study area was found four types of sediments , there are: gravelly, sand, silty sand, sandy silt and silt Distribution of gravel found in two places, namely on the north and south banks of the study area. Distribution of sand reaches approximately 30% of the water area of research, silty sand covering approximately 5% of the water area of research, sandy silt has spread approximately 30% of the total water area of research and distribution of silt contained in the inner face of the Gulf estuaries Papela with cover approximately 5% of the water area of research. Keywords: Surficial sediment, grain size analysis, sediment distribution, Papela Waters
24
Liu, Yang, Peng Zhang, Sen Du, Zhuoru Lin, Yanyan Zhou, Lizhao Chen, Rencheng Yu e Li Zhang. "Sediment as a Potential Pool for Lipophilic Marine Phycotoxins with the Case Study of Daya Bay of China". Marine Drugs 17, n. 11 (31 ottobre 2019): 623. http://dx.doi.org/10.3390/md17110623.
Testo completoAbstract (sommario):
Marine sediments can reserve many environmental pollutants. Lipophilic marine phycotoxins (LMPs) are natural toxic substances widespread in the marine environment; however, evidence of their existence in sediment is scarce. In the present study, in order to explore the occurrence and distribution characteristics of LMPs in sediment, surface sediment samples collected from a tropical area of Daya Bay (DYB) at different seasons, were analyzed using liquid chromatography with tandem mass spectrometry (LC-MS/MS). According to the results, up to six toxin compounds were detected in sediment samples from DYB, OA and DTX1 had the highest levels, followed by PTX2, homo-YTX, AZA2, and GYM. Although AZA2 and GYM were found in most of the sediment, OA, DTX1, homo-YTX, and PTX2 were the predominant toxin compounds, and PTX2 was the most ubiquitous toxin in sediment. The spatial distribution of LMP components in the sediment fluctuated with sampling times, partially according to the physical–chemical parameters of the sediment. There are likely several sources for LMPs existing in surface sediments, but it is difficult to determine contributions of a specific toxin-source in the sediment. Therefore, marine sediments may be a toxin reservoir for LMPs accumulation in benthic organisms via food chains.
25
Matmon, Ari, Kyle Nichols e Robert Finkel. "Isotopic insights into smoothening of abandoned fan surfaces, Southern California". Quaternary Research 66, n. 1 (luglio 2006): 109–18. http://dx.doi.org/10.1016/j.yqres.2006.02.010.
Testo completoAbstract (sommario):
AbstractCosmogenic nuclide concentrations measured on abandoned fan surfaces along the Mojave section of the San Andreas Fault suggest that sediment is generated, transported, and removed from the fans on the order of 30–40 kyr. We measured in situ produced cosmogenic 10Be, and in some cases 26Al, in boulders (n = 15), surface sediment (n = 15), and one depth profile (n = 9). Nuclide concentrations in surface sediments and boulders underestimate fan ages, suggesting that 10Be accumulation is largely controlled by the geomorphic processes that operate on the surfaces of the fans and not by their ages.Field observations, grain-size distribution, and cosmogenic nuclide data suggest that over time, boulders weather into grus and the bar sediments diffuse into the adjacent swales. As fans grow older the relief between bars and swales decreases, the sediment transport rate from bars to swales decreases, and the surface processes that erode the fan become uniform over the entire fan surface. The nuclide data therefore suggest that, over time, the difference in 10Be concentration between bars and swales increases to a maximum until the topographic relief between bars and swales is minimized, resulting in a common surface lowering rate and common 10Be concentrations across the fan. During this phase, the entire fan is lowered homogeneously at a rate of 10–15 mm kyr−1.
26
Clayton, C. J., e S. J. Hay. "Gas migration mechanisms from accumulation to surface". Bulletin of the Geological Society of Denmark 41 (30 marzo 1994): 12–23. http://dx.doi.org/10.37570/bgsd-1995-41-03.
Testo completoAbstract (sommario):
The driving force for gas migration is buoyancy, aided in some cases by sediment overpressure gradients (pressures above hydrostatic). Resistance to migration is controlled by the-capillary entry pressure into the pore network of the overlying sediments, or by their resistance to fracturing. It can be shown that migration mechanisms vary with depth. Below the upper few hundred metres gas migrates by invading the pore network of the sediment whereas at shallower depths fracturing may occur preferentially. Thus even though gas appears to seep into the water column from fractures it will be more dispersed below the sediment surface. In addition, gas shows a tendency to "pond" in near surface sediments, which can be explained as a function of sediment compaction with depth and decreasing gas-water interfacial tension. Approximate calculations of seal leakage rates are possible using a modified Darcy flow equation. For capillary failure of a mudstone seal at 3 km depth, gas fluxes are in the order of .0015 m3/m2/year at ambient pressure or 0.23 m3/m2/year at surface conditions. Flow rates from fractured seals depend on the amount of time the fracture remains open. They vary from a value similar to that for capillary failure if the fracture is open for an average of one minute per year, to five or six orders of magnitude faster. The calculated capillary failure fluxes are comparable to measured surface gas seepage fluxes.
27
Manning, P. C. "Phosphate Ion Interactions at the Sediment–Water Interface in Lake Ontario: Relationship to Sediment Adsorption Capacities". Canadian Journal of Fisheries and Aquatic Sciences 44, n. 12 (1 dicembre 1987): 2204–11. http://dx.doi.org/10.1139/f87-270.
Testo completoAbstract (sommario):
The chemical forms of iron and phosphorus in surficial sediments of the Niagara Basin of Lake Ontario were determined by Mossbauer spectral and chemical extraction methods. The core locations lie on a transect across a boundary separating sediments displaying a crusty iron- and phosphorus-rich red layer a few centimetres beneath the sediment–water interface from sediments displaying no such layer. Concentrations of nonapatite inorganic phosphorus are relatively low at the surfaces of the layered cores whereas the iron forms are quantitatively similar. It is proposed that the red layers prevent upward diffusion of pore-water ferrous and phosphate ions to the surface. The degree of phosphorus recycling within the top few centimetres of sediment can then be estimated. Approximately 0.035% nonapatite inorganic phosphorus is carried into the anoxic zone. The data, combined with loadings of fine-grained sediment, indicate that Lake Ontario sediments have a net annual binding capacity of ~3500 metric tons of phosphorus, which compares with current loadings of ~8900 metric tons. This binding capacity supports current recommended phosphorus loadings to Lake Ontario.
28
Alley, Richard B., Daniel E. Lawson, Edward B. Evenson e Grahame J. Larson. "Sediment, glaciohydraulic supercooling, and fast glacier flow". Annals of Glaciology 36 (2003): 135–41. http://dx.doi.org/10.3189/172756403781816121.
Testo completoAbstract (sommario):
AbstractGlaciers often advance over proglacial sediments, which then may enhance basal motion. For glaciers with abundant meltwater, thermodynamic considerations indicate that the sediment–ice contact in the direction of ice flow tends toward an angle opposed to and somewhat steeper than the surface slope (by slightly more than 50%). A simple model based on this hypothesis yields the extent of over-ridden sediments as a function of sediment thickness and strength, a result that may be useful in guiding additional fieldwork for hypothesis testing. Sediment-floored as well as rock-floored overdeepenings are common features along glacier flow paths and are expected based on theories of glacier erosion, entrainment, transport and deposition.
29
Chen, Xian, Xiaoming Sun, Zhongwei Wu, Yan Wang, Xiao Lin e Hongjun Chen. "Mineralogy and Geochemistry of Deep-Sea Sediments from the Ultraslow-Spreading Southwest Indian Ridge: Implications for Hydrothermal Input and Igneous Host Rock". Minerals 11, n. 2 (29 gennaio 2021): 138. http://dx.doi.org/10.3390/min11020138.
Testo completoAbstract (sommario):
Detailed mineralogical and geochemical characteristics of typical surface sediments and hydrothermal deposits collected from the ultraslow-spreading Southwest Indian Ridge (SWIR) were studied by high-resolution XRD, SEM-EDS, XRF, and ICP-MS. The SWIR marine samples can be generally classified into two main categories: surface sediment (biogenic, volcanic) and hydrothermal-derived deposit; moreover, the surface sediment can be further classified into metalliferous and non-metalliferous based on the metalliferous sediment index (MSI). The chemical composition of biogenic sediment (mainly biogenic calcite) was characterized by elevated contents of Ca, Ba, Rb, Sr, Th, and light rare earth elements (LREE), while volcanic sediment (mainly volcanogenic debris) was relatively enriched in Mn, Mg, Al, Si, Ni, Cr, and high field strength elements (HFSEs). By contrast, the hydrothermal-derived deposit (mainly pyrite-marcasite, chalcopyrite-isocubanite, and low-temperature cherts) contained significantly higher contents of Fe, Cu, Zn, Pb, Mn, Co, Mo, Ag, and U. In addition, the metalliferous surface sediment contained a higher content of Cu, Mn, Fe, Co, Mo, Ba, and As. Compared with their different host (source) rock, the basalt-hosted marine sediments contained higher contents of Ti–Al–Zr–Sc–Hf and/or Mo–Ba–Ag; In contrast, the peridotite-hosted marine sediments were typically characterized by elevated concentrations of Mg–Cu–Ni–Cr and/or Co–Sn–Au. The differences in element enrichment and mineral composition between these sediment types were closely related to their sedimentary environments (e.g., near/far away from the vent sites) and inherited from their host (source) rock. Together with combinations of certain characteristic elements (such as Al–Fe–Mn and Si–Al–Mg), relict hydrothermal products, and diagnostic mineral tracers (e.g., nontronite, SiO2(bio), olivine, serpentine, talc, sepiolite, pyroxene, zeolite, etc.), it would be more effective to differentiate the host rock of deep-sea sediments and to detect a possible hydrothermal input.
30
Ren, Ze, Xiaodong Qu, Wenqi Peng, Yang Yu e Min Zhang. "Nutrients Drive the Structures of Bacterial Communities in Sediments and Surface Waters in the River-Lake System of Poyang Lake". Water 11, n. 5 (2 maggio 2019): 930. http://dx.doi.org/10.3390/w11050930.
Testo completoAbstract (sommario):
Lake and its inflow rivers compose a highly linked river-lake system, within which sediment and water are also closely connected. However, our understanding of this linked and interactive system remains unclear. In this study, we examined bacterial communities in the sediments and surface waters in Poyang Lake and its five tributaries. Bacterial communities were determined while using high-throughput 16S rRNA gene sequencing. The results showed significant differences of bacterial communities between sediments and surface waters, as well as between Poyang lake and its tributaries, suggesting that the river-lake system of Poyang Lake provides diverse and distinct habitats for bacterial communities, including lake water, lake sediment, river water, and river sediment. These biomes harbor distinct bacterial assemblages. Sediments harbor more diverse bacterial taxa than surface waters, but the bacterial communities in surface waters were more different across this river-lake system than those in sediments. In this eutrophic river-lake ecosystem, nitrogen and phosphorus were important drivers in sediment bacterial communities. Nitrogen, phosphorus, and dissolved organic carbon, as well as their stoichiometric ratios affected bacterial communities in surface waters. Moreover, network analysis revealed that the bacterial communities in surface waters were more vulnerable to various disturbances than in sediments, due to lower alpha diversity, high complexity of network, and a small number of key taxa (module hubs and connectors). Nutrient variables had strong influences on individual operational taxonomic units (OTUs) in the network, especially in bacterial network in surface waters. Different groups of taxa responded differently to nutrients, with some modules being more susceptible to nutrient variations. This study increased our current knowledge of linked river-lake ecosystems and provided valuable understanding for effective management and protection of these ecosystems by revealing bacterial communities in sediments and surface waters in Poyang Lake and its tributaries, as well as their responses to nutrients variation.
31
Wu, Chao, Xiaodong Wu, Xuguang Ge, Lian Feng, Ya Tan, Jiuyun Yang, Weixiang Ren e Min Zou. "Characteristics of Dissolved Organic Matter in Sediments of Typical Lakes in Southeastern Hubei Province, China". International Journal of Environmental Research and Public Health 19, n. 12 (16 giugno 2022): 7402. http://dx.doi.org/10.3390/ijerph19127402.
Testo completoAbstract (sommario):
This study aimed to reveal the distribution characteristics and sources of dissolved organic matter (DOM) in sediments of typical lakes in the southeastern of the Hubei province and provide a reference for pollution control of eutrophic lakes. The sediments of four typical lakes (Liangzi, Baoan, Daye, and Qingshan) in the southeastern of the Hubei Province were investigated in May 2019. Ultraviolet-visible (UV-Vis) absorption spectroscopy and excitation-emission matrixes characteristics of DOM were obtained by UV-Vis spectrophotometry and three-dimensional fluorescence spectroscopy. Moreover, the DOM fluorescence components were resolved by parallel factor analysis (PARAFAC). The results showed that: (1) The absorption coefficient a350 in surface sediments followed the order: Baoan Lake (16.99 ± 3.82 m−1) > Qingshan Lake (15.37 ± 3.8 m−1) > Liangzi Lake (12.54 ± 5.58 m−1) > Daye Lake (12.43 ± 1.43 m−1). Specifically, with increasing depth in the sediment cores, a350 increased and then gradually decreased in Daye Lake and Baoan Lake, but fluctuated in Liangzi Lake and Qingshan Lake with a roughly decreasing trend. (2) Two humic-like components (C1, C2) and one protein-like component (C3) were identified via PARAFAC. This analysis also showed that the surface sediment fluorescent dissolved organic matter (FDOM) was dominated by protein-like, while the sediment core FDOM was dominated by humic-like in Liangzi Lake. The proportion of humic-like in FDOM was higher than protein-like in surface sediments and sediment cores of Baoan, Daye, and Qingshan Lakes. (3) The DOM of surface sediments in the Liangzi Lake comprised mostly autochthonous components, mainly produced by the vital activities of aquatic organisms. The DOM of surface sediments in Baoan Lake and Qingshan Lake showed weak humic and moderate autochthonous characteristics. The humification of DOM in sediment cores of Liangzi, Baoan, and Qingshan Lakes gradually decreased from depth to the surface. The DOM in surface sediments of Daye Lake had strong humic and moderate autochthonous characteristics. (4) In general, the DOM of lake sediments in southeastern Hubei Province has dual-contribution characteristics representing terrigenous and endogenous sources. In the restoration and treatment of lake ecology, both internal and terrestrial pollution should be considered. At the same time, it is noteworthy that cyanobacteria depletion and aquatic residues caused potential internal pollution.
32
Zhang, Lian Kai, Hui Yang e Wei Jin. "Distribution Characteristics and Ecological Risk Assessment of Arsenic in the Surface Sediment of Bohai Sea". Advanced Materials Research 610-613 (dicembre 2012): 932–35. http://dx.doi.org/10.4028/www.scientific.net/amr.610-613.932.
Testo completoAbstract (sommario):
Arsenic is a carcinogen to both humans and animals. Thirteen typical surface sediment samples were taken at Tanghe and Daihe in Qinhuangdao, April, 2011. Hydride generation atomic fluorescence spectrometry (HG-AFS) was used to analyze arsenic (As) concentration. The correlations of sediment arsenic and sediment organic matter (SOM), pH, river water arsenic were discussed. Index of geoaccumulation (Igeo) and potential ecological risk index were cited to assess the arsenic pollution level and its potential ecological risk. The results show that, arsenic in river water sediment, estuary sediment and coast sediment of Daihe are lower than the average level of other Chinese rivers. Arsenic Igeo of these sediments are cleanliness. However, Arsenic concentration in the sampling points of Tanghe is higher than the average level of domestic rivers except river water sampling points. Their Igeo are light pollution. The potential ecological risk index of the two rivers are slight ecological harm. Arsenic concentration of different sampling points in the two rivers distributes as: estuary sediment As>coast sediment As> river water sediment As. The correlation among sediment arsenic, water arsenic, SOM and sediment pH are: 1) Arsenic in sediment has a extremely significant positive correlation with that in water at p<0.01; 2) Sediment arsenic shows a significant positive correlation with SOM at p<0.05; 3) However, there is a negative correlation between sediment pH and sediment arsenic.
33
Weingarten, Eric A., Lauren A. Lawson e Colin R. Jackson. "The Saltpan Microbiome Is Structured by Sediment Depth and Minimally Influenced by Variable Hydration". Microorganisms 8, n. 4 (8 aprile 2020): 538. http://dx.doi.org/10.3390/microorganisms8040538.
Testo completoAbstract (sommario):
Saltpans are a class of ephemeral wetland characterized by alternating periods of inundation, rising salinity, and desiccation. We obtained soil cores from a saltpan on the Mississippi Gulf coast in both the inundated and desiccated state. The microbiomes of surface and 30 cm deep sediment were determined using Illumina sequencing of the V4 region of the 16S rRNA gene. Bacterial and archaeal community composition differed significantly between sediment depths but did not differ between inundated and desiccated states. Well-represented taxa included marine microorganisms as well as multiple halophiles, both observed in greater proportions in surface sediment. Functional inference of metagenomic data showed that saltpan sediments in the inundated state had greater potential for microbial activity and that several energetic and degradation pathways were more prevalent in saltpan sediment than in nearby tidal marsh sediment. Microbial communities within saltpan sediments differed in composition from those in adjacent freshwater and brackish marshes. These findings indicate that the bacterial and archaeal microbiomes of saltpans are highly stratified by sediment depth and are only minimally influenced by changes in hydration. The surface sediment community is likely isolated from the shallow subsurface community by compaction, with the microbial community dominated by marine and terrestrial halophiles.
34
Praeger, Thomas H., Stuart D. Messur e Richard P. DiFiore. "Remediation of PCB-containing sediments using surface water diversion “dry excavation”: a case study". Water Science and Technology 33, n. 6 (1 marzo 1996): 239–45. http://dx.doi.org/10.2166/wst.1996.0102.
Testo completoAbstract (sommario):
Remediation of contaminated sediments presents an on-going challenge in the efforts toward improved water quality and environmental restoration. Faced with this challenge, Mercury Marine recently selected a remedial alternative that included diverting creek flow and removing approximately 5,900 in-situ cubic meters of sediments containing PCBs from an impoundment in Cedar Creek. The regulatory objective was to remove all sediment containing PCBs “to the extent practicable” from an 180-meter stretch of the impoundment. A remedial investigation was conducted to collect the data necessary to characterize the site and prepare a remedial design. Technical issues involved with dry excavation that were critical to implementing this alternative included: channel diversion, sediment characterization, pond dewatering, wastewater treatment, groundwater infiltration, surface water run-off, and sediment removal, handling and disposal. Mercury Marine and its engineering staff found sediment removal by dry excavation to be a labor intensive and costly means of remediating the PCB-affected sediments at this site. Before implementing dry excavation at any site, owners, consultants, and regulatory agencies must realize the many limitations of this alternative and give special consideration to site conditions, engineering, and planning.
35
Nwosu, Ebuka Canisius, Patricia Roeser, Sizhong Yang, Lars Ganzert, Olaf Dellwig, Sylvia Pinkerneil, Achim Brauer, Elke Dittmann, Dirk Wagner e Susanne Liebner. "From Water into Sediment—Tracing Freshwater Cyanobacteria via DNA Analyses". Microorganisms 9, n. 8 (21 agosto 2021): 1778. http://dx.doi.org/10.3390/microorganisms9081778.
Testo completoAbstract (sommario):
Sedimentary ancient DNA-based studies have been used to probe centuries of climate and environmental changes and how they affected cyanobacterial assemblages in temperate lakes. Due to cyanobacteria containing potential bloom-forming and toxin-producing taxa, their approximate reconstruction from sediments is crucial, especially in lakes lacking long-term monitoring data. To extend the resolution of sediment record interpretation, we used high-throughput sequencing, amplicon sequence variant (ASV) analysis, and quantitative PCR to compare pelagic cyanobacterial composition to that in sediment traps (collected monthly) and surface sediments in Lake Tiefer See. Cyanobacterial composition, species richness, and evenness was not significantly different among the pelagic depths, sediment traps and surface sediments (p > 0.05), indicating that the cyanobacteria in the sediments reflected the cyanobacterial assemblage in the water column. However, total cyanobacterial abundances (qPCR) decreased from the metalimnion down the water column. The aggregate-forming (Aphanizomenon) and colony-forming taxa (Snowella) showed pronounced sedimentation. In contrast, Planktothrix was only very poorly represented in sediment traps (meta- and hypolimnion) and surface sediments, despite its highest relative abundance at the thermocline (10 m water depth) during periods of lake stratification (May–October). We conclude that this skewed representation in taxonomic abundances reflects taphonomic processes, which should be considered in future DNA-based paleolimnological investigations.
36
Kurečić, Tomislav, Valentina Hajek Tadesse, Lara Wacha, Marija Horvat, Nina Trinajstić e Ivan Mišur. "Sub-recent microfauna within allogenic sediments at the bottom of a deep cave, Njemica (Biokovo Mt., Croatia)". International Journal of Speleology 51, n. 3 (novembre 2022): 223–33. http://dx.doi.org/10.5038/1827-806x.51.3.2428.
Testo completoAbstract (sommario):
Clastic sediments deposited at the bottom of the vertical, nearly 1000 m deep Njemica Cave (Biokovo Mountain, Croatia) were analysed. Owing to the vertical morphology of the cave, the occurrences of clastic sediments are sparse. Small, up to decimetre-thick, undisturbed sediment accumulations situated near the siphon lake revealed interesting palaeontological and mineralogical data. These data are used as a useful proxy for discussing depositional processes, the provenance of the sediments and paleo-habitats of the subterranean fauna. The sub-recent assemblages of ostracods were discovered within the sediment, and they were shown to be correlative to the known endemic species in the wider Dinaric Karst area (Pseudocypridopsis sywulai and Phreatocandona cf. motasi). The well-preserved sediment archive indicates the allogenic origin of the sediment and defines it as an allochthonous infiltrate of the Quaternary. The detritus originates from Pleistocene–Holocene deposits in the surrounding area, whose composition was influenced by volcanic activity in the wide Adriatic region. Sedimentation occurred in a calm aquatic environment by settling from suspension. Therefore the sediments are defined as slackwater deposits.
37
Rognerud, Sigurd, Trond Skotvold, Eirik Fjeld, Stephen A. Norton e Anders Hobæk. "Concentrations of trace elements in recent and preindustrial sediments from Norwegian and Russian Arctic lakes". Canadian Journal of Fisheries and Aquatic Sciences 55, n. 6 (1 giugno 1998): 1512–23. http://dx.doi.org/10.1139/f98-026.
Testo completoAbstract (sommario):
Cu, Hg, Ni, Pb, Se, and Zn concentrations in surface and preindustrial freshwater sediments from 66 lakes in the Norwegian and Russian Arctic were used for studying modern atmospheric deposition of these elements. Statistical analysis showed that, after adjusting for the effects of scavenging factors in sediments (organic matter, Al, and Fe), there were, in general, significantly higher concentrations of Hg and Pb in surface sediments than preindustrial sediments. The differences decreased with increasing latitude and increasing longitude to the east, and in the lakes from arctic islands of Svalbard and along the the arctic coastline of Russia, only Hg concentrations were elevated in surface sediments. We attribute this pattern to modern anthropogenic atmospheric deposition. There were no such differences or regional gradients for the other trace metals. A multivariate analysis of the sediment data showed that Hg and Se were associated with organic matter, whereas Cu, Ni, and Zn were associated with inorganic matter (Al, Fe). There was a shift in Pb association from inorganic matter in the reference sediment to organic matter in the surface sediment, which we interpret as an historic change in importance of sources (from bedrock-derived to atmospheric deposition).
38
Jiang, L., Y. C. Chen, D. J. Zhu e Z. W. Liu. "Faecal coliform attachment to settleable suspended sediments in fresh surface waters: linear partition model validation and sediment concentration effects". Water Supply 15, n. 4 (1 aprile 2015): 864–70. http://dx.doi.org/10.2166/ws.2015.042.
Testo completoAbstract (sommario):
Controlled experiments were conducted to examine the validity of the linear partition model for faecal coliform (FC) attachment to suspended sediments and assess the impact of sediment concentration on the attachment. Sediments were collected from a river in Beijing, China and the suspended particles <62 μm were separated out and mixed with FC suspensions. The experimental mass specific concentration of attached FC linearly increased with the free-floating FC concentration, with the partition coefficient for four different sediment concentrations ranging from 0.2286 to 0.2695 L/g. Actually, the results can be well described using a single partition coefficient of 0.2565 L/g. The rate of sediment particle surface covered by attached FC was in the range of 0.32 × 10−5–0.58 × 10−5, and the relatively low rate gave a possible explanation of the linear relationship. The experimental fraction of attached FC significantly increased with increasing sediment concentration, ranging from 7.5 to 54.2%, and this was well explained by the linear partition model. These results proved that the linear partition model was valid in describing FC attachment to suspended sediments in surface waters and the attached fraction was sediment concentration dependent, while the impact of suspended sediment concentration on the partition coefficient was insignificant.
39
Sakadevan, K., Huang Zheng e H. J. Bavor. "Impact of Heavy Metals on Denitrification in Surface Wetland Sediments Receiving Wastewater". Water Science and Technology 40, n. 3 (1 agosto 1999): 349–55. http://dx.doi.org/10.2166/wst.1999.0181.
Testo completoAbstract (sommario):
Denitrification in sediment-water systems is a predominant process in the removal of nitrogen from wetlands and sediments receiving recycled water. In this study the impact of cadmium (Cd), copper (Cu) and zinc (Zn) on denitrification was examined for a wetland sediment receiving recycled water. Results from the study showed that application of 100 mg Cd kg−1 sediment had no effect (P<0.05) on denitrification (161±2.7 mg N kg−1 sediment) compared to the control (162±2.4 mg N kg−1 sediment) which did not receive Cd, Cu or Zn. Addition of 100 mg Cu or Zn kg−1 sediment significantly increased denitrification (170±1.8 and 168±2.7 mg N2O-N kg−1 sediment for Cu and Zn, respectively) compared to the control treatment. Addition of Cd, Cu or Zn at 500 or 1000 mg kg−1 sediment significantly decreased (P<0.05) total denitrification compared to the control and treatments, which received 100 mg Cd, Cu or Zn kg−1 sediment. For a given heavy metal concentration the largest denitrification inhibition occurred with Cd (30.9%) followed by Zn (24.9%) and Cu (18.9%) over a period of seven days. The amount of ammonium in the sediment water increased in all treatments receiving Cd, Cu or Zn and the concentration increased as the concentration of Cd, Cu or Zn increased in the sediment-water environment. For a given heavy metal concentration, the largest increase in ammonium occurred in treatments receiving Cd (31.1±0.9 mg N kg−1 sediment) followed by Zn (24.8±0.5 mg N kg−1 sediment) and Cu (17.0±0.3 mg N kg−1 sediment). Denitrification inhibition was linearly related to the concentration of ammonium in sediment water (r2=0.928). In general, the study showed that the addition of Cd, Cu or Zn inhibited denitrification and increased the concentration of ammonium in the sediment-water environment.
40
Kawara, O. "Study on the Seasonal Variation of Surface Sediment Composition in Estuaries". Water Science and Technology 20, n. 6-7 (1 giugno 1988): 123–32. http://dx.doi.org/10.2166/wst.1988.0196.
Testo completoAbstract (sommario):
The purpose of this study, as the first step toward clarifying the pollutant transport mechanism of sediments, is to clarify the characteristics of the seasonal changes of surface sediment composition in estuaries based on observation. Remarkable seasonal variations are found in the particle size distributions and the concentrations of the constituents of the surface sediments, though the patterns of the variations are different in each estuary observed. The seasonal variations of the concentrations show good correspondence to those of the particle size distributions. One cause of the seasonal variation is the variation of river discharges. When the sediment size in the Asahi River estuary, Okayama prefecture, became finer, the fresh water inflow to the estuary was about 2.5-3.5 times as much as ordinary water runoff (100-150m3/s) and the change was completed in about 10 days. On the other hand, the change to coarser sediment was completed in a day, by the inflow of over 400m3/s.
41
Yuan, Xu Yin, Quan Liu, Ji Zhou Li, Jun Feng Ji e Chang Ping Mao. "Risk Assessment of Organochlorine Compounds in Water and Surface Sediments from Taihu Lake and Nanjing Section of Changjiang, China". Advanced Materials Research 356-360 (ottobre 2011): 624–29. http://dx.doi.org/10.4028/www.scientific.net/amr.356-360.624.
Testo completoAbstract (sommario):
Samples of surface water and sediment were collected in Taihu Lake and Nanjing section of Changjiang. Organochlorine compounds(OCCs) of samples were detected to investigate the characteristics and ecological risk of them in the lake and river. The concentrations of OCCs in water of Nanjing section of Changjiang were higher than those in Taihu Lake, but the concentrations of OCCs in sediments were higher in Taihu Lake. HCHs of Taihu sediments were relatively enriched, indicating the agricultural source of compounds. PCBs of Changjiang sediments were higher compared to Taihu sediments, denoting a obvious industrial source. Comparing with other compartments in China, HCHs of the study area were higher than most sediment of Chinese rivers, DDTs didn’t show high contents in sediments, PCBs was in relatively low levels. By contrast with the relevant sediment quality guidelines of these compounds, the ecological risk of OCCs in sediments were evaluated. The OCCs of sediments in Taihu Lake and Nanjing section of Changjiang didn’t show high ecological risk.
42
Scheckel, Kirk G., Aaron G. B. Williams, Gregory Mc Dermott, David Gratson, Dean Neptune e James A. Ryan. "Lead Speciation and Bioavailability in Apatite-Amended Sediments". Applied and Environmental Soil Science 2011 (2011): 1–8. http://dx.doi.org/10.1155/2011/689568.
Testo completoAbstract (sommario):
The in situ sequestration of lead (Pb) in sediment with a phosphate amendment was investigated by Pb speciation and bioavailability. Sediment Pb in preamendment samples was identified as galena (PbS) with trace amounts of absorbed Pb. Sediment exposed to atmospheric conditions underwent conversion to hydrocerussite and anglesite. Sediments mixed with apatite exhibited limited conversion to pyromorphite, the hypothesized end product. Conversion of PbS to pyromorphite is inhibited under reducing conditions, and pyromorphite formation appears limited to reaction with pore water Pb and PbS oxidation products. Porewater Pb values were decreased by 94% or more when sediment was amended with apatite. The acute toxicity of the sediment Pb was evaluated withHyalella aztecaand bioaccumulation of Pb withLumbriculus variegatus. The growth ofH. aztecamay be mildly inhibited in contaminated sediment, with apatite-amended sediments exhibiting on average a higher growth weight by approximately 20%. The bioaccumulation of Pb inL. variegatustissue decreased with increased phosphate loading in contaminated sediment. The study indicates limited effectiveness of apatite in sequestering Pb if present as PbS under reducing conditions, but sequestration of porewater Pb and stabilization of near-surface sediment may be a feasible and alternative approach to decreasing potential toxicity of Pb.
43
Andersen, Helle Vang, Jesper Kjølholt, Christian Poll, Steen Øgaard Dahl, Frank Stuer-Lauridsen, Finn Pedersen e Estelle Bjørnestad. "Environmental risk assessment of surface water and sediments in Copenhagen harbour". Water Science and Technology 37, n. 6-7 (1 marzo 1998): 263–72. http://dx.doi.org/10.2166/wst.1998.0761.
Testo completoAbstract (sommario):
The environmental risk assessment of Holmen, a former naval base, included characterisation of the sediments with regard to pollution with xenobiotics, heavy metals, nutrients and bacteria, and ecotoxicity. A simple hydraulic model was established, and the release of substances from the sediment to the water was assessed. Sediment biotests with Corophium volutator and porewater biotests with Skeletonema costatum and Acartia tonsa were conducted. The sediment was characterised as strongly contaminated in the major parts of the investigated area. Based on the application of the acid volatile sulfide method it was concluded that practically none of the heavy metals were bioavailable. Both the sediment and the porewater from a number of stations were toxic. The toxicity did not appear to be attributable to the content of heavy metals, more likely to other contaminants. Furthermore, the sediment, which has served as a sink for accumulation of contaminants over a period of many years, also may constitute a source of contamination due to potential release of heavy metals and xenobiotics from the sediment to the water in some areas. The release appears to give rise to concentrations above the EU Water Quality Objectives at some stations.
44
Forsythe, K. Wayne, Danielle E. Ford, Chris H. Marvin, Richard R. Shaker, Michael W. MacDonald e Ryan Wilkinson. "Multivariable 3D Geovisualization of Historic and Contemporary Lead Sediment Contamination in Lake Erie". Pollutants 1, n. 1 (21 febbraio 2021): 29–50. http://dx.doi.org/10.3390/pollutants1010004.
Testo completoAbstract (sommario):
Lead sediment contamination in Lake Erie stems from a long history of natural and synthetic resource production. Sediment samples with variable sampling densities were collected by the Canada Centre for Inland Waters in 1971, 1997/1998, and 2014. The kriging interpolation method was used to create continuous sediment contamination surfaces for time/space comparisons. Change detection analyses identified an overall decreasing trend in high lead pollution levels from 1971 to 2014, while sediments with the lowest concentrations increased in surface area. Lake-wide circulation patterns and bathymetric data were added to interpolated contamination surfaces to enhance the understanding of interrelated hydrodynamic processes and geophysical features in the movement of contaminated sediments. Utilizing visualization tools in Esri’s ArcScene, bathymetric data were employed to enhance the geographic context of contamination maps. The physical barriers to sediment transportation created by bathymetric features can be visualized in three-dimensions. Elevated features between lake basins are easily recognized as impedances to lake currents when circulation directions are draped over the bathymetric model. By using illumination tools and techniques, geovisualizations of lead sediment contamination throughout Lake Erie create a scientific communication tool for a wide audience to use in multiple-criteria decision making for environmental remediation of sediment contamination.
45
Glasser, Neil F., e Michael J. Hambrey. "Tidewater glacier beds: insights from iceberg debris in Kongsfjorden, Svalbard". Journal of Glaciology 47, n. 157 (2001): 295–302. http://dx.doi.org/10.3189/172756501781832331.
Testo completoAbstract (sommario):
AbstractThe sediment in icebergs offers an opportunity to sample the otherwise inaccessible beds of modern tidewater glaciers. This paper presents a discussion of the benefits and problems of using iceberg debris to make inferences about the nature of the beds of modern tidewater glaciers. As an example, we present data obtained from icebergs calved from fast-flowing tidewater glaciers in Kongsfjorden, Svalbard. Sediment samples obtained from 12 icebergs show that clast-rich muddy diamicton is the dominant facies, although muddy gravel and mud are also present in some debris layers. Sediment texture and clast-shape analyses indicate that most debris in the icebergs is of basal origin. Micro-morphological analyses of thin sections of the diamicton also indicate pervasive deformation of the sediment. Although individual icebergs only represent small samples of the bed of a tidewater glacier, and problems remain in linking iceberg sediments to their precalving transport history beneath the glacier, this method provides a potentially fruitful way of linking sediments to glacier dynamics.
46
Aleksander-Kwaterczak, Urszula, e Anna Kostka. "Lead in the environment of Lake Wigry (NE Poland)". Limnological Review 11, n. 2 (1 gennaio 2011): 59–68. http://dx.doi.org/10.2478/v10194-011-0027-z.
Testo completoAbstract (sommario):
Lead in the environment of Lake Wigry (NE Poland)Analysis was performed for lead content in the sediments of Lake Wigry (NE Poland), taking into account lithology, basic chemical component content and physical characteristics of sediment, Several hundred sediment samples from different parts of the lake and peatland around the lake, were collected. Their locations were determined by GPS and the depth of sediment by echosounder. The surface layer (0-10 cm) of sediment and sediment cores were taken to determine the spatial and vertical distribution of Pb. Concentrations of lead in the surface sediment range from 2.52 to 469 mg kg-1. One of the most important factors influencing spatial distribution of Pb is sediment type. The highest content of Pb was found in samples of organic gyttja and the lowest in clastic sediment samples. Strong positive linear correlation (r = 0.7) between organic matter content and Pb concentration in sediment was observed. It may be the result of simple bio-accumulation of lead. A large influence of sediment location on Pb distribution was found. The largest concentration of this element was found in sediment of the Wigry Basin. The major part of Pb accumulates in the surface layer of sediment.
47
Chafiq, Mohamed, Janine Gibert e Cécile Claret. "Interactions among sediments, organic matter, and microbial activity in the hyporheic zone of an intermittent stream". Canadian Journal of Fisheries and Aquatic Sciences 56, n. 3 (1 marzo 1999): 487–95. http://dx.doi.org/10.1139/f98-208.
Testo completoAbstract (sommario):
Interactions between surface and subsurface water in intermittent streams are poorly understood. We predicted that surface discharge patterns would influence retention and transport of fine sediments and particulate organic matter in a first-order intermittent stream, which in turn would affect microbial activity at different depths in the sediment. We measured sediments, dissolved and particulate organic carbon, and microbial and bacterial biomass and activity at three depths (surface and 20 and 40 cm) over a period spanning low and high flows at five stations on an intermittent stream. Discharge influenced physicochemical and sediment characteristics at the upstream stations with coarse substratum. In the finer sediments of the lower reaches, an active hyporheic microbial assemblage primarily governed sediment and organic dynamics. With decreasing discharge and increasing retention of fine sediments and particulate organic carbon, greater microbial hydrolytic activity in bed-sediments occurred downstream. Dissolved oxygen, organic carbon, fine sediments, microbial biomass, hydrolytic activity, and bacterial biomass declined with depth, and changed over time, apparently in response to varying discharge. We conclude that discharge and substratum particle size may interact to control organic dynamics and hyporheic microbial activity in a 1st order stream.
48
Shaiek, Moez, Noureddine Zaaboub, Deniz Ayas, Maria Virgínia Alves Martins e Mohamed Salah Romdhane. "CRABS AS BIOINDICATORS OF TRACE ELEMENT ACCUMULATION IN MEDITERRANEAN LAGOON (BIZERTE LAGOON, TUNISIA) / CARANGUEJOS USADOS COMO BIOINDICADORES DE ACUMULAÇÃO DE METAIS NUMA LAGUNA MEDITERRÂNEA (LAGUNA DE BIZERTE, TUNÍSIA)". Journal of Sedimentary Environments 3, n. 1 (25 febbraio 2018): 1–11. http://dx.doi.org/10.12957/jse.2018.32950.
Testo completoAbstract (sommario):
Nine crab species samples, males and females, were collected after homogeneously prospection of sediment surface of Bizerte Lagoon. Crabs were caught by dip net from Bizerte Lagoon during spring 2012. Concentrations of metals (Zn, As, Cd, Cr, Cu, Fe, Ni, Pb and Zn) were evaluated in the carapace and muscle tissue of crabs and in surface sediment samples. Concentrations of metals accumulated in the benthic crabs tissues were compared to the reactive metals content that constitute the bioavailable fraction of the sediments. Total organic carbon and carbonate contents were also determined, since they are principal requirements associated with crab development.Results of this work indicate that, in the study area, the metals that reach the highest concentrations in the sediments-water interface are by decreasing order Zn, Cr and Pb. The reactive concentrations of these metals are also the highest. However, the trace elements that are being accumulated in the carapace and muscle of crabs are mainly As and Cu.Continental waters flowing into the Bizerte Lagoon are the main source and the principal cause of the enrichment of trace elements in sediment. Results highlight that the reactive concentrations of metals in sediments were the principal cause of their bioaccumulation in the crabs tissues.The important results of this work highlight that cabs can be very useful on studies of monitoring and evaluation of environmental quality in addition to data obtained from the sediment as they also give information about the bioaccumulation of metals through the oceanic food webs. ResumoNove amostras de espécies de caranguejos, machos e fêmeas, foram coletadas na superfície do sedimento da Laguna de Bizerte. Os caranguejos foram capturados com uma rede na Laguna de Bizerte, na primavera de 2012. Foram avaliadas nas carapaças e no tecido muscular dos caranguejos e em amostras de sedimentos superficiais, concentrações de metais (Zn, As, Cd, Cr, Cu, Fe, Ni, Pb e Zn). As concentrações de metais acumuladas nos tecidos de caranguejos bênticos foram comparadas com o teor de metais reativos que constituem a fração biodisponível dos sedimentos. Os teores totais de carbono orgânico e carbonato também foram determinados, uma vez que são requisitos principais associados ao desenvolvimento dos caranguejos.Os resultados deste trabalho indicam que, na área de estudo, os metais que atingem as maiores concentrações na interface sedimentos-água são, por ordem decrescente, Zn, Cr e Pb. As concentrações reativas desses metais também são as mais elevadas. No entanto, os metais que estão sendo acumulados nas carapaças e nos músculos dos caranguejos são principalmente As e Cu. As águas continentais que desembocam na Laguna Bizerte são a principal fonte e a principal causa do enriquecimento de metais nos sedimentos. Os resultados sugerem que as concentrações reativas de metais nos sedimentos foram a principal causa de sua bioacumulação nos tecidos dos caranguejos.Os resultados deste trabalho revelam que para além dos dados sedimentológicos, os caranguejos podem ser muito úteis em estudos de monitoramento e avaliação da qualidade ambiental, pois fornecem informações sobre a bioacumulação de metais através das cadeias alimentares oceânicas.
49
Deasy, C., e J. N. Quinton. "Use of rare earth oxides as tracers to identify sediment source areas for agricultural hillslopes". Solid Earth Discussions 2, n. 2 (1 luglio 2010): 195–212. http://dx.doi.org/10.5194/sed-2-195-2010.
Testo completoAbstract (sommario):
Abstract. Understanding sediment sources is essential to enable more effective targeting of in-field mitigation approaches to reduce diffuse pollution from agricultural land. In this paper we report on the application of rare earth element oxides to arable soils at hillslope scale in order to determine sediment source areas and their relative importance, using a non-intrusive method of surface spraying. Runoff, sediments and rare earth elements lost from four arable hillslope lengths at a site in the UK with clay soils were monitored from three rainfall events after tracer application. Measured erosion rates were low, reflecting the typical event conditions occurring at the site, and less than 1% of the applied REO tracers were recovered, which is consistent with the results of comparable studies. Tracer recovery at the base of the hillslope was able to indicate the relative importance of different hillslope sediment source areas, which were found to be consistent between events. The principal source of eroded sediments was the upslope area, implying that the wheel tracks were principally conduits for sediment transport, and not highly active sites of erosion. Mitigation treatments for sediment losses from arable hillslopes should therefore focus on methodologies for trapping mobile sediments within wheel track areas through increasing surface roughness or reducing the connectivity of sediment transport processes.
50
Deasy, C., e J. N. Quinton. "Use of rare earth oxides as tracers to identify sediment source areas for agricultural hillslopes". Solid Earth 1, n. 1 (26 novembre 2010): 111–18. http://dx.doi.org/10.5194/se-1-111-2010.
Testo completoAbstract (sommario):
Abstract. Understanding sediment sources is essential to enable more effective targeting of in-field mitigation approaches to reduce diffuse pollution from agricultural land. In this paper we report on the application of rare earth element oxides to arable soils at hillslope scale in order to determine sediment source areas and their relative importance, using a non-intrusive method of surface spraying. Runoff, sediments and rare earth elements lost from four arable hillslope lengths at a site in the UK with clay soils were monitored from three rainfall events after tracer application. Measured erosion rates were low, reflecting the typical event conditions occurring at the site, and less than 1% of the applied REO tracers were recovered, which is consistent with the results of comparable studies. Tracer recovery at the base of the hillslope was able to indicate the relative importance of different hillslope sediment source areas, which were found to be consistent between events. The principal source of eroded sediments was the upslope area, implying that the wheel tracks were principally conduits for sediment transport, and not highly active sites of erosion. Mitigation treatments for sediment losses from arable hillslopes should therefore focus on methodologies for trapping mobile sediments within wheel track areas through increasing surface roughness or reducing the connectivity of sediment transport processes.