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UP: Umweltphysik

UP 8: Bodenphysik - Poster

UP 8.2: Poster

Montag, 18. März 2002, 16:30–18:00, Galerie 1

SOLUTE MIXING AND MACROSCOPIC SOIL WATER HYSTERESIS — •Michela Rossi¹, Nadia Ursino², and Hannes Fluehler¹ — ¹Soil Physics, Swiss Federal Institute of Techonology Zuerich, Schlieren, Switzerland — ²Dipartimento IMAGe, Universita’ di Padova, Via Loredan 20, 35131 Padua, Italy

Both field and laboratory experiments have shown that structural heterogeneity of soils can strongly dominate the flow field depending on the water saturation degree. At high saturation degrees they can behave as quasi-homogeneous structures while at lower saturation degrees fast and sharply delimited flow paths may be embedded in a low conductive background. So, the conductivity map of a heterogeneous soil depends on water saturation.

The variable hydraulic structure strongly affects the transport of dissolved chemicals: the residence time of a certain chemical in a zone of high sorption capacity changes with saturation affecting the mixing and dilution processes.

We performed laboratory sand tank experiments in order to describe and quantify the effect of physical heterogeneity at different stationary flow regimes established during drainage and imbibition.

Fluorescence imaging techniques are used to investigate the concentration distribution of the tracers at different saturation degrees. The so obtained concentration maps are analyzed in terms of spatial moments and of the dilution index, which describes local mixing processes.