Inhaltszusammenfassung

Under field conditions, the upper soil layers are exposed to dynamics of moisture and tem-perature. In the course of change of moisture, soil organic matter (SOM) changes its water content and its state of swelling. Recent results show that, with the state of swelling, SOM gradually changes its physicochemical properties, such as sorbent properties , , macromolecu-lar structure , , thermal characteristics or the binding of hydrophobic organic chemicals. These changes are ...Under field conditions, the upper soil layers are exposed to dynamics of moisture and tem-perature. In the course of change of moisture, soil organic matter (SOM) changes its water content and its state of swelling. Recent results show that, with the state of swelling, SOM gradually changes its physicochemical properties, such as sorbent properties , , macromolecu-lar structure , , thermal characteristics or the binding of hydrophobic organic chemicals. These changes are well-known to affect sorption and transport phenomena and thus have to be taken into consideration. Despite this relevance, very little is known about the process of swelling of SOM, and even less is known about its effect on SOM physicochemistry . In the study presented here, we investigated the process of drying and rewetting in selected humic soil samples. We focussed on the properties of dissolved organic matter. The soil sam-ples were observed before and after drying and during cycles of re-wetting. The state of moi-sture affected the surface tension and the amount and quality of the dissolved organic matter, which was indicated by the molecular size distribution, by the UV absorption of the size frac-tions, and probably also by the particle size distribution itself. From these observations, we conclude that the state of moisture of humic soil samples strongly affects many colloidal cha- racteristics of DOM.» weiterlesen» einklappen

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