Inhaltszusammenfassung

The hydration kinetics of soil organic matter (SOM) are influential factors for transport and sorption processes in soil. Nevertheless, our knowledge about wetting and swelling processes, which both control the overall hydration kinetics, is limited. In this study, we observed the hydration process of actually water repellent and wettable soil samples with three independent methods. The rate of water uptake by water repellent samples was distinctly lower than that of wettabl...The hydration kinetics of soil organic matter (SOM) are influential factors for transport and sorption processes in soil. Nevertheless, our knowledge about wetting and swelling processes, which both control the overall hydration kinetics, is limited. In this study, we observed the hydration process of actually water repellent and wettable soil samples with three independent methods. The rate of water uptake by water repellent samples was distinctly lower than that of wettable samples when the water was supplied in liquid phase, but was comparable when water was supplied in gas phase. Gravimetric measurements of the water uptake and 1H NMR Relaxometry showed that wetting of water repellent soils may last up to three weeks. This duration is distinctly longer than the WDPT of the samples, which consequently only reflects the first wetting step of the soil surface and does not consider infiltration of larger amounts of water. Since the achievement of equilibrium conditions is a slow process, the hydration kinetics of SOM may control transport and sorption kinetics in water repellent soils. Differences in the freezing, melting and evaporation processes of soil water of actually water repellent and wettable soil samples, observed by Differential Scanning Calorimetry (DSC), are most probably only a consequence of different water contents under field conditions. Consequently, the DSC measurements provided no evidence of a general difference in the way of water binding in water repellent and wettable soil samples.» weiterlesen» einklappen

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