Changes of steady state water flow rates and the bromide breakthrough were observed in laboratory infiltration experiments done on a sample of compacted sand and on an undisturbed soil sample (Eutric Cambisol). Infiltration-outflow experiments consisted of series of ponded infiltration runs with seepage face boundary condition at the lower end of columns. The initial water contents were different for each run. The results of the experiment done on an undisturbed soil column showed that the flux rates and water contents measured during quasi-steady state differ between infiltration runs. This finding contradicts the standard theory. The fluctuations of the water content during the steady state flow can be ascribed to the variations in volume of the entrapped air. Similarly, bromide breakthrough curves performed during the steady state flow runs differ for the undisturbed soil sample. The same behaviour was not observed in the sample of homogeneous sand. Computer tomography was utilized to characterize the structure of the undisturbed soil sample with focus on potential preferential flow pathways. To formulate more general conclusions, the infiltration outflow and bromide solute transport experiments have to continue with the aim to collect a representative set of data. and Studie sleduje změny ustálených rychlostí proudění a průnikových čar bromidu na vzorku zhutněného písku a na neporušeném vzorku půdy ze skupiny kambisolů. Experimenty sestávaly ze série výtopových infiltrací na horním okraji a s výronovou plochou na spodním okraji vzorků. Počáteční vlhkost byla pro jednotlivé infiltrační běhy různá. Výsledky experimentu uskutečněného na neporušené půdě ukazují, že se vlhkosti a rychlosti proudění během ustáleného proudění lišily pro jednotlivé infiltrační běhy. Tento efekt není ve shodě se standardní teorií. Změny vlhkosti během ustáleného proudění mohou být způsobeny přítomností uzavřeného vzduchu. Pro neporušený půdní vzorek se lišil také tvar průnikových čar bromidu, měřených během ustáleného proudění. Oba efekty nebyly pozorovány pro vzorek zhutněného písku. Počítačová tomografie byla použita k popisu struktury neporušeného půdního vzorku se zaměřením na přítomnost potenciálních cest preferenčního proudění. K tomu, aby bylo možno formulovat obecné závěry, bude nutné získat reprezentativní soubor dat pomocí zde představeného experimentu.
Isothermal and non-isothermal infiltration experiments with tracer breakthrough were carried out in the laboratory
on one intact column (18.9 cm in diameter, 25 cm in height) of sandy loam soil. For the isothermal experiment, the
temperature of the infiltrating water was 20°C to the initial temperature of the sample. For the two non-isothermal experiments
water temperature was set at 8°C and 6°C, while the initial temperature of the sample was 22°C. The experiments
were conducted under the same initial and boundary conditions. Pressure heads and temperatures were monitored in two
depths (8.8 and 15.3 cm) inside the soil sample. Two additional temperature sensors monitored the entering and leaving
temperatures of the water. Water drained freely through the perforated plate at the bottom of the sample by gravity and
outflow was measured using a tipping bucket flowmeter. The permeability of the sample calculated for steady state stages
of the experiment showed that the significant difference between water flow rates recorded during the two experiments
could not only be justified by temperature induced changes of the water viscosity and density. The observed data
points of the breakthrough curve were successfully fitted using the two-region physical non-equilibrium model. The results
of the breakthrough curves showed similar asymmetric shapes under isothermal and non-isothermal conditions.