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  • 1
    Electronic Resource
    Electronic Resource
    Experimental investigation of transport of strongly retained species by soil columns (1997)
    Springer
    Water, air & soil pollution 95 (1997), S. 337-351 
    Details
    ISSN: 1573-2932
    Keywords: transport ; soil columns ; breakthrough curves ; lead ; proton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Column experiments have been extensively used in transport studies of major cations but few investigations are available on migration through soils of strongly retained species that are environmentally relevant (like heavy metals). By presenting some selected experiments (lead and proton step-breakthrough tests in different conditions), this study shows that the soil-column technique is also applicable in the case of species which exhibit very large retention factors. The use of very small soil columns (about 0.4 mL of pore volumes) combined with relatively high flow rates (0.1–0.3 mL min−1 ) allows to observe the entire breakthrough curve (adsorption and desorption front up to 5000 pore volumes) in reasonable experimental time, in reproducible conditions and without experimental drawbacks. In the adopted experimental conditions no kinetic effects, related to diffuse transport and sorption reaction were recognized; moreover, Peclet number was higher than 60. Consequently, it was possible to calculate the equilibrium isotherms from the diffuse fronts of the breakthrough. Knowledge that can be derived, concerning the reversibility of the adsorption process, the influence of complexation on the adsorption, the kinetics of complex formation, and the effect of dissolution on proton transport, is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406173
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    EXPERIMENTAL INVESTIGATION OF TRANSPORT OF STRONGLY RETAINED SPECIES BY SOIL COLUMNS (1997)
    Springer
    Water, air & soil pollution 95 (1997), S. 337-351 
    Details
    ISSN: 1573-2932
    Keywords: transport ; soil columns ; breakthrough curves ; lead ; proton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Column experiments have been extensively used in transport studies of major cations but few investigations are available on migration through soils of strongly retained species that are environmentally relevant (like heavy metals). By presenting some selected experiments (lead and proton step-breakthrough tests in different conditions), this study shows that the soil-column technique is also applicable in the case of species which exhibit very large retention factors. The use of very small soil columns (about 0.4 mL of pore volumes) combined with relatively high flow rates (0.1–0.3 mL min-1 ) allows to observe the entire breakthrough curve (adsorption and desorption front up to 5000 pore volumes) in reasonable experimental time, in reproducible conditions and without experimental drawbacks. In the adopted experimental conditions no kinetic effects, related to diffuse transport and sorption reaction were recognized; moreover, Peclet number was higher than 60. Consequently, it was possible to calculate the equilibrium isotherms from the diffuse fronts of the breakthrough. Knowledge that can be derived, concerning the reversibility of the adsorption process, the influence of complexation on the adsorption, the kinetics of complex formation, and the effect of dissolution on proton transport, is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026474015336
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    Paper (German National Licenses)
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  • 3
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    Solar Energetic Particle Events Observed by the PAMELA Mission (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Despite the significant progress achieved in recent years, the physical mechanisms underlying the origin of solar energetic particles (SEPs) are still a matter of debate. The complex nature of both particle acceleration and transport poses challenges to developing a universal picture of SEP events that encompasses both the low-energy (from tens of keV to a few hundreds of MeV)observations made by space-based instruments and the GeV particles detected by the worldwide network of neutron monitors in ground-level enhancements (GLEs). The high-precision data collected by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) satellite experiment offer a unique opportunity to study the SEP fluxes between 80 MeV and a few GeV, significantly improving the characterization of the most energetic events. In particular, PAMELA can measure for the first time with good accuracy the spectral features at moderate and high energies, providing important constraints for current SEP models. In addition, the PAMELA observations allow the relationship between low and high-energy particles to be investigated, enabling a clearer view of the SEP origin. No qualitative distinction between the spectral shapes of GLE, sub-GLE and non-GLE events is observed, suggesting that GLEs are not a separate class, but are the subset of a continuous distribution of SEP events that are more intense at high energies. While the spectral forms found are to be consistent with diffusive shock acceleration theory, which predicts spectral rollovers at high energies that are attributed to particles escaping the shock region during acceleration, further work is required to explore the relative influences of acceleration and transport processes on SEP spectra.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN67543 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 862; 2; 97
    Format: application/pdf
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