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Introduction: Under field conditions, the upper soil layers are exposed to dynamics of moisture and temperature. 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 propertiesi,ii macromolecular structureiii,iv, thermal characteristicsv or the binding of hydrophobic organic chemicals. These ch...Introduction: Under field conditions, the upper soil layers are exposed to dynamics of moisture and temperature. 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 propertiesi,ii macromolecular structureiii,iv, thermal characteristicsv 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 proc-ess of swelling of SOM, and even less is known about its effect on SOM physicochemistryvi and on the colloidal properties of SOM. In the study presented here, we investigated the process of drying and rewetting in selected sandy soil samples with the focus on some colloidal properties. Conclusions: From the observations in this study, we conclude that the state of moisture of soil samples containig organic matter strongly affects colloidal characteristics in aqueous soil extracts. The hydrophobicity of the soil sample may affect the mo-lecular size distribution in the soil extracts. However, fur-ther studies have to be done which investigate whether this is an effect of hydrophobicity or of the different chemistry or microbiology as indicated for example by the difference in pH. Freeze-drying affected the colloidal characteristics reversi- bly, while air-drying seemed to have irreversible effects on the colloidal properties of the soil extracts. Due to this irreversibility, drying is also expected to have an influence on the process of soil formation.» weiterlesen» einklappen

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