Search results for "Sediment"
showing 10 items of 1648 documents
Post-fire practices benefits on vegetation recovery and soil conservation in a Mediterranean area
2021
Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG. [Abstract] Post-fire practices (PFP) aim to reduce soil erosion and favour vegetation recovery, but their effectiveness is spatially heterogeneous and under debate because of the economic and environmental costs. This study evaluates the different changes (Δ) of canopy cover (CC), sediment connectivity (SC) and local topography in four areas affected by the Pinet fire in eastern Spain (August 8th, 2018) and managed with: totally burnt with tree removal and long log erosion barriers (LEBs) (Pinet-1), partially burnt without PFP (Pinet-2), totally burnt with tree removal and short LEBs (Pinet-3), and totally burnt wit…
Sediment yield from glacio-lacustrine calcareous deposits during the postglacial period in the Combe d’Ain (Jura, France)
1998
The middle valley of the river Ain (Jura) cuts through glacio-lacustrine deposits laid down in an ice-dammed lake during the most recent glacial advance. The total volume eroded is about 6·21 ×10 8 m 3 for a surface area of 3·7 ×10 7 m 2 . Erosion occurred between 18 ka BP and 6 ka BP, i.e. over a duration of some 12 ka. Sediment yield from the area was of the order of 2500 t km -2 a -1 , which is comparable with modern-day sediment yield from NW African badlands. These high values are ascribed to the amenability of glacio-lacustrine deposits to mechanical weathering and to the rapid geomorphological changes that affected glacial and paraglacial sedimentary cover after the retreat of the ic…
Atmospheric Lead Deposition into Guarapina Lagoon, Rio de Janeiro State, Brazil
1988
The rate of anthropogenic mobilization of heavy metals is higher than the natural supply to the sedimentary environments. I n rivers, lakes and various other terrestrial areas, the drastic increase of heavy metals has been accredited to human activity (Tyler 1972). Erlenkeuser et al. (1974) suggest that Cd, Pb, Zn and Cu in the upper sediment sequence of sediment cores collected from Kiel Bight in the Baltic Sea, are the result of fossil fuel use in industries. Such assemblages have been identified in North America by Goldberg et al. (1977, 1979) from both coastal regions. Sediment cores taken from the deepest part of lakes and lagoons have been analysed to study the historical development …
Management of Alluvial Forests Included in Natura 2000 91E0* Habitat Type in Maramureş Mountains Nature Park
2015
Abstract The Natura 2000 habitat type 91E0* Alluvial forests of Alnus glutinosa and Fraxinus excelsior (Alno-Padion, Alnion incanae, Salicion albae) include three subtypes of forests. In the Maramureș Mountains Nature Park (MMNP) the alluvial forests are represented by Alnus incana forest situated on the banks of mountain rivers. Starting from 2007, 70% of the MMNP is also a Natura 2000 site of community interest. In the standard form for the site are listed 18 Natura 2000 habitat types, but that of alluvial forests 91E0* is not listed either due to an error or lack of available research data. Our study seeks to provide information regarding this high conservation value habitat such as: str…
Hatching and viability of rotifer diapausing eggs collected from pond sediments
2006
SUMMARY 1. Planktonic rotifers inhabiting variable environments produce diapausing eggs that accumulate in the sediment of lakes and ponds, forming egg banks that may withstand adverse periods. A common assumption in zooplankton diapausing egg bank studies is to count as viable all eggs in the sediment that look healthy. This assumption should be challenged by asking how effectively ‘healthy-looking’ eggs represent viable eggs. 2. In this study, viability of more than 1100 ‘healthy-looking’ diapausing eggs belonging to the Brachionus plicatilis species complex was assessed in a laboratory hatching experiment. Eggs were collected at different depths from sediment cores obtained from 15 ponds…
Sediment Transport and Hydrodynamic Parameters of Tsunami Waves Recorded in Onshore Geoarchives
2014
In regions with a short historical tsunami record, the assessment of long-term tsunami risk strongly depends on geological evidence of prehistoric events. Whereas dating tsunami deposits is already well established, magnitude assessment based on remaining sedimentary structures is still a major challenge. In this study, two approaches were applied to deduce transport processes and hydrodynamic parameters of tsunami events from onshore deposits found in the coastal plain of Ban Bang Sak, SW Thailand: (1) The maximum offshore sediment source was determined using granulometry, geochemistry, mineralogy and foraminifera of the tsunamites, and reference samples from various marine and terrestrial…
Heavy Metal Contents in Soft-Bottom Marine Macrophytes and Sediments Along the Mediterranean Coast of Spain
2000
. Hg, Cd, Pb and Zn concentrations were determined in sediment and in tissues of five species of soft-bottom marine macrophytes (Posidonia oceanica, Cymodocea nodosa, Zostera noltii, Ruppia cirrhosa and Caulerpa prolifera) along the Spanish Mediterranean coast. Levels of metals were low in most of the sampling stations and similar to those found by other authors in uncontaminated zones. Certain locations, however, showed some degree of contamination (Cambrils, Almassora, Alacant, Mar Menor and El Portus). In Santa Pola we found high contents of metals in one sample of sediment due to the high proportion of the fine fraction (particules < 63µm) and organic matter, but not in the seagrass spe…
Response of benthic foraminifera to heavy metal contamination in marine sediments (Sicilian coasts, Mediterranean sea)
2011
To examine the suitability of benthic foraminifera and their test deformations as bioindicators of pollution in coastal marine environments, we studied foraminifera and metal concentrations in 72 marine sediment samples, collected from the inner shelf along the Sicilian coast (Gulfs of Palermo and Termini) and on the south-eastern coast of Lampedusa Island. These areas are characterised by different environmental conditions. On the basis of pollution sources and foraminiferal assemblages, we recognised different zones in the Gulf of Palermo. The most polluted zones showed high metal concentrations, and low diversity of benthic foraminifera with species typical of stressed environments. By c…
10. Holocene and Eemian varve types of Eifel maar lake sediments
2007
Abstract Varves of the Holocene and of the last interglacial were investigated in two sediment sequences from Eifel maar lakes. The modern maar with Schalkenmehrener Maar Lake and the dry maar lake West Hoher List have the same size, are two kilometres apart at the same altitude, but the Eemian lake was much deeper. The sediments of both lakes are dominated by autochthonous sediments, mainly from diatom-dominated algae. Differences in the palaeoproductivity and in calcite precipitation are probably not climatically controlled but due to lake basin morphometry and the carbonate reservoir in the catchment areas. The occurrence of dry periods with aeolian dust deposition during the last interg…
Computation of flow velocity in rough channels
2006
Accurate estimate of flow-velocity profile is of crucial importance both for scientific purposes and for solving numerous engineering problems that include, among others, sediment transport, contaminant transport, flow resistance evaluation. This paper presents a new empirical equation to represent the vertical velocity profile. The proposed equation is essentially a modified form of the well-known logarithm law of the wall and contains three parameters having a clear physical meaning. The applicability of the equation and its accuracy assessment for different hydraulic conditions, including non-uniform conditions, is verified by using experimental data obtained by different sources. The va…