Near-surface solute redistribution during evaporation

M. Bechtold, S. Haber-Pohlmeier, J. Vanderborght, A. Pohlmeier, Paul A Ferre, H. Vereecken

Research output: Contribution to journalArticle

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Abstract

We present results from solute transport experiments in an evaporating composite porous medium consisting of a cylindrical inner core with coarse sand that was surrounded by a mantle with fine sand. Small volumes of dye and salt tracer were applied at the surface of the fine material of the evaporating column. The pressure head at the bottom boundary was kept constant using a hanging water table ensuring liquid phase continuity to top surface in both fine and coarse material, whereby the latter was hydraulically less conductive at these pressure conditions. Contrary to the expectation that solute accumulation at an evaporating surface is proportional to local cumulative evaporation, high concentration spots developed at the surface of the coarse material, for which IR surface temperature measurements did not indicate higher evaporation fluxes. 3D unsaturated flow and transport simulations and a second tracer experiment monitored with magnetic resonance imaging (MRI) demonstrated that preferential upward water flux in the fine sand deeper in the column and near-surface lateral water flow from the fine into the coarse sand in combination with a downward diffusive flux are responsible for the local solute accumulation. We propose that at the wet regions of a soil surface, solute accumulation is largely decoupled from local evaporation fluxes and strongly governed by relative differences of the hydraulic conductivities. The possible formation of high solute concentration spots at the surface of coarser regions usually representing preferential flow pathways during strong precipitation may have an accelerating effect on the leaching of solutes.

Original languageEnglish (US)
Article numberL17404
JournalGeophysical Research Letters
Volume38
Issue number17
DOIs
StatePublished - 2011

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solute
solutes
evaporation
sands
sand
tracers
tracer
pressure heads
unsaturated flow
inner core
water tables
preferential flow
solute transport
water flow
leaching
porous medium
water table
hydraulic conductivity
dye
continuity

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Geophysics

Cite this

Bechtold, M., Haber-Pohlmeier, S., Vanderborght, J., Pohlmeier, A., Ferre, P. A., & Vereecken, H. (2011). Near-surface solute redistribution during evaporation. Geophysical Research Letters, 38(17), [L17404]. https://doi.org/10.1029/2011GL048147

Near-surface solute redistribution during evaporation. / Bechtold, M.; Haber-Pohlmeier, S.; Vanderborght, J.; Pohlmeier, A.; Ferre, Paul A; Vereecken, H.

In: Geophysical Research Letters, Vol. 38, No. 17, L17404, 2011.

Research output: Contribution to journalArticle

Bechtold, M, Haber-Pohlmeier, S, Vanderborght, J, Pohlmeier, A, Ferre, PA & Vereecken, H 2011, 'Near-surface solute redistribution during evaporation', Geophysical Research Letters, vol. 38, no. 17, L17404. https://doi.org/10.1029/2011GL048147
Bechtold M, Haber-Pohlmeier S, Vanderborght J, Pohlmeier A, Ferre PA, Vereecken H. Near-surface solute redistribution during evaporation. Geophysical Research Letters. 2011;38(17). L17404. https://doi.org/10.1029/2011GL048147
Bechtold, M. ; Haber-Pohlmeier, S. ; Vanderborght, J. ; Pohlmeier, A. ; Ferre, Paul A ; Vereecken, H. / Near-surface solute redistribution during evaporation. In: Geophysical Research Letters. 2011 ; Vol. 38, No. 17.
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