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| Titel |
Deep and near-surface solute redistribution during evaporation leads to high-concentration spots and loops of solute mass fluxes |
| VerfasserIn |
Michel Bechtold, Sabina Haber-Pohlmeier, Jan Vanderborght, Andreas Pohlmeier, Ty P. A. Ferre, Harry Vereecken |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250057125
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| Zusammenfassung |
| We present magnetic resonance imaging (MRI) data of solute transport in a heterogeneous
porous medium during a cycle of infiltration and evaporation. The solute plume
(aqueous solution of Gd-DTPA) was visualized using a strongly T1 weighted spin echo
sequence. During infiltration solute was preferentially transported downwards in
coarse-grained zones, whereas during evaporation solute moved from coarse- to fine-grained
zones deeper in the sample and from fine- to coarse-grained zones near the sample
surface. This ‘solute mass loop’ was predicted by a 3D coupled unsaturated flow
and solute transport model based on Richards’ and advection-dispersion equation.
Observations of dye and salt tracer distributions at the sample surface confirm that
near-surface redistribution can lead to high concentration spots in coarse-grained
zones.
The accumulation in coarse-grained zones is opposite to the perception that
accumulation would take place primarily in regions with a finer soil texture which
support a higher evaporation. We propose that as long liquid water flow to the soil
surface is sustained to coarse- and fine-grained zones, flow will redistribute and
accumulate solutes towards locations with lowest water potential. These locations
correspond to regions with low hydraulic conductivity, which can be either fine-
or coarse-grained regions, depending on the pressure conditions. A 2D model is
used to examine the impact of this transport cycling on solute breakthrough curves. |
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