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  • caesium-137  (2)
  • modelling  (2)
  • overbank sedimentation  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 99 (1997), S. 71-80 
    ISSN: 1573-2932
    Keywords: River floodplains ; overbank sedimentation ; floodplain deposits ; grain size composition ; spatial variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract An important feature of overbank floodplain deposits is the spatial variability of their particle size composition. Analysis of such spatial variability can assist in developing an improved understanding of the transport and deposition of suspended sediment on river floodplains during overbank flood events, in investigating the fate of sediment-associated contaminants and in calibrating existing floodplain sediment deposition models. The study reported in this paper investigates the spatial variability of the grain size composition of overbank floodplain deposits at different spatial scales, through analysis of surface sediment samples collected from frequently inundated floodplain sites on the Rivers Culm, Stour and Severn in the UK. Significant lateral and downstream variations in the grain size composition of the sediment deposits have been documented at the study sites, and the results obtained have been interpreted in terms of the processes governing overbank floodplain flow and sediment transport and deposition, which are influenced by a number of factors including floodplain geometry and topography.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 99 (1997), S. 9-20 
    ISSN: 1573-2932
    Keywords: Floodplains ; sedimentation ; caesium-137 ; unsupported lead-210 ; overbank deposition ; deposition rates ; fallout radionuclides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Attempts to study spatial patterns of overbank sedimentation on river floodplains commonly face important operational and sampling problems in documenting deposition rates. Recent advances in the application of fallout radionuclides (137Cs and unsupported210Pb) to the estimation of medium-term rates of overbank sedimentation offer an essentially unique opportunity to assemble detailed distributed data sets for medium term deposition rates. Such data can afford a valuable basis for investigating the complex relationship between sedimentation rates and floodplain microtopography and morphology and flow hydraulics. This paper reports the results of an investigation of the spatial pattern of overbank sedimentation rates on the floodplain of the River Culm, Devon, UK. Caesium-137 and unsupported210Pb measurements have been used to establish the general pattern of deposition rates along an 11 kilt reach and more intensive measurements have been employed to document the detailed pattern existing within a small area subject to frequent inundation. The resultant data have been used as a basis for interpreting the major controls on the observed patterns.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 99 (1997), S. 71-80 
    ISSN: 1573-2932
    Keywords: River floodplains ; overbank sedimentation ; floodplain deposits ; grain size composition ; spatial variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract An important feature of overbank floodplain deposits is the spatial variability of their particle size composition. Analysis of such spatial variability can assist in developing an improved understanding of the transport and deposition of suspended sediment on river floodplains during overbank flood events, in investigating the fate of sediment-associated contaminants and in calibrating existing floodplain sediment deposition models. The study reported in this paper investigates the spatial variability of the grain size composition of overbank floodplain deposits at different spatial scales, through analysis of surface sediment samples collected from frequently inundated floodplain sites on the Rivers Cuhn, Stour and Severn in the UK. Significant lateral and downstream variations in the grain size composition of the sediment deposits have been documented at the study sites, and the results obtained have been interpreted in terms of the processes governing overbank floodplain flow and sediment transport and deposition, which are influenced by a number of factors including floodplain geometry and topography.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 99 (1997), S. 9-20 
    ISSN: 1573-2932
    Keywords: Floodplains ; sedimentation ; caesium-137 ; unsupported lead-210 ; overbank deposition ; deposition rates ; fallout radionuclides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Attempts to study spatial patterns of overbank sedimentation on river floodplains commonly face important operational and sampling problems in documenting deposition rates. Recent advances in the application of fallout radionuclides (137Cs and unsupported 210Pb) to the estimation of medium-term rates of overbank sedimentation offer an essentially unique opportunity to assemble detailed distributed data sets for medium-term deposition rates. Such data can afford a valuable basis for investigating the complex relationship between sedimentation rates and floodplain microtopography and morphology and flow hydraulics. This paper reports the results of an investigation of the spatial pattern of overbank sedimentation rates on the floodplain of the River Culm, Devon, UK. Caesium-137 and unsupported 210Pb measurements have been used to establish the general pattern of deposition rates along an 11 km reach and more intensive measurements have been employed to document the detailed pattern existing within a small area subject to frequent inundation. The resultant data have been used as a basis for interpreting the major controls on the observed patterns.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-2932
    Keywords: desorption ; ferrihydrite ; modelling ; phosphate ; TEM ; transformation ; wastewater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The presence of phosphate retards the transformation of ferrihydrite into crystalline products. Increasing phosphate from 0 to 1 mole % results in an order of magnitude decrease in the rate of transformation of ferrihydrite at pH 12. Levels of phosphate of ∼1 mol % suppress the formation of goethite (α-FeO(OH)) and result in the formation of a product consisting of η-Fe2O3. Higher levels of phosphate result in the ferrihydrite remaining amorphous, even after several hundred hours. Phosphate prevents formation of goethite by hindering the dissolution of ferrihydrite rather than by interfering with nucleation and growth of goethite in solution. The transformation rate of pure ferrihydrite is also strongly inhibited in the presence of dissolved phosphate. This is due to surface complexation. The transformation rate was measured at temperatures of 60 °C and 70 °C. The rate of transformation was found to be described by either (i) a solid-state reaction equation for powdered compacts or (ii) a zero-order reaction controlled by desorption. The transformation of the ferrihydrite matrix was accompanied by the loss of the phosphate trace component. X-ray diffraction indicates that no solid solution involving phosphate substitution into η-Fe2O3 is formed. Transmission electron microphotographs of the original precipitates containing phosphate confirm the presence of the phosphate and demonstrate its involvement in linking together extremely small particles of ferrihydrite.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-2932
    Keywords: desorption ; ferrihydrite ; modelling ; phosphate ; TEM ; transformation ; wastewater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The presence of phosphate retards the transformation of ferrihydrite into crystalline products. Increasing phosphate from 0 to 1 mole % results in an order of magnitude decrease in the rate of transformation of ferrihydrite at pH 12. Levels of phosphate of ∼1 mol % suppress the formation of goethite (α-FeO(OH)) and result in the formation of a product consisting ofη-Fe2O3. Higher levels of phosphate result in the ferrihydrite remaining amorphous, even after several hundred hours. Phosphate prevents formation of goethite by hindering the dissolution of ferrihydrite rather than by interfering with nucleation and growth of goethite in solution. The transformation rate of pure ferrihydrite is also strongly inhibited in the presence of dissolved phosphate. This is due to surface complexation. The transformation rate was measured at temperatures of 60 °C and 70 °C. The rate of transformation was found to be described by either (i) a solid-state reaction equation for powdered compacts or (ii) a zero-order reaction controlled by desorption. The transformation of the ferrihydrite matrix was accompanied by the loss of the phosphate trace component. X-ray diffraction indicates that no solid solution involving phosphate substitution intoη-Fe2O3 is formed. Transmission electron microphotographs of the original precipitates containing phosphate confirm the presence of the phosphate and demonstrate its involvement in linking together extremely small particles of ferrihydrite.
    Type of Medium: Electronic Resource
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