Inhaltszusammenfassung

Under field conditions, soils are influenced by a permanent change of the moisture conditions. A consequence is the alternation of water uptake and swelling as well as water losing and shrinkage. These processes depend strongly on the hydrophobic properties of the soil organic matter. Up to now, the description of the time dependent behaviour of soil organic matter during the uptake of water is insufficient. Furthermore, very little ...Under field conditions, soils are influenced by a permanent change of the moisture conditions. A consequence is the alternation of water uptake and swelling as well as water losing and shrinkage. These processes depend strongly on the hydrophobic properties of the soil organic matter. Up to now, the description of the time dependent behaviour of soil organic matter during the uptake of water is insufficient. Furthermore, very little is known about the characteristics of wettable and hydrophobic soils which are responsible for the differences during water uptake and swelling. This contribution tries to describe the kinetic of water uptake of hydrophobic and wettable soil samples. The dependence of the time constants on the properties of the different soil samples are discussed. In addition, further soil parameters were investigated in order to describe changes of the soil structure and of the interactions with the soil water that occur during water uptake and swelling. The freezing behaviour of the soil water was investigated by Differential Scanning Calorimetry (DSC). Probably, these DSC measurements provide parameters that could be applied to trace the swelling process and to distinguish between different forms of water binding in soil. Furthermore, 1H NMR measurements have shown continuous changes in the distribution of the pore sizes in the course of soil swelling. Finally, it was tested, if it is possible to observe the changing soil structure during the water uptake with an Environmental Scanning Electron Microscope (ESEM). The different investigations show that the process swelling lasts up to a time of three weeks. However, after this period of time the differences of hydrophobic and wettable soil samples concerning the interactions with water have not completely disappeared.» weiterlesen» einklappen

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