Inhaltszusammenfassung

Under field conditions, soils are influenced by a permanent change of the moisture conditions. A consequence is the alternation of uptake and loss of water, which coincides with swelling 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 characte...Under field conditions, soils are influenced by a permanent change of the moisture conditions. A consequence is the alternation of uptake and loss of water, which coincides with swelling 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 shows the latest results of the water uptake kinetics of hydrophobic and wettable soil samples. The dependence of the time constants on the properties of the different soil samples are discussed. Further soil parameters characterising the changes of the soil structure and of the interactions with the soil water that occur during water uptake and swelling were examined. The freezing behaviour of the soil water was investigated by Differential Scanning Calorimetry (DSC). Probably, these DSC measurements provide information to trace the swelling process and to distinguish between different forms of water binding in soil. Finally, structural properties observed with an Environmental Scanning Electron Microscope (ESEM) of dried and swollen soil samples are described and discussed. The different investigations show that the process of 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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