Inhaltszusammenfassung

The objective of these investigations was to gain information about the structure of solid-phase soil organic matter. A continuous extraction method was developed to investigate the kinetics of the dissolution of SOM (soil organic matter) from sandy, humic soil material, which was extracted in the dry or pre-moistened state. The extractions were carried out with water or with 0.01 M CaCl2, at different flow rates and temperatures for about 4 to 6 hours. The experi...The objective of these investigations was to gain information about the structure of solid-phase soil organic matter. A continuous extraction method was developed to investigate the kinetics of the dissolution of SOM (soil organic matter) from sandy, humic soil material, which was extracted in the dry or pre-moistened state. The extractions were carried out with water or with 0.01 M CaCl2, at different flow rates and temperatures for about 4 to 6 hours. The experiments show that the dissolution of SOM is rate limited (i.e. the dissolved organic matter is not in equilibrium with the solid phase) with the dissolution rate depending on the pre-moistening time and the electrolyte concentration. The energy of activation indicates diffusion control. As diffusion in the liquid phase is not expected to depend strongly on the moisture condition of SOM or the electrolyte concentration, it was concluded that the solid SOM phase controls the rate of diffusion. This is considered to be due to a gel phase developing in the swelling SOM. The lower dissolution rates found for extractions with 0.01 M CaCl2 could indicate a more stable gel structure than in the presence of water. The development of the gel phase may be influenced by mechanical strain due to increased flow rates. The gel structure should help to further explain certain ecological functions of soil organic matter.» weiterlesen» einklappen

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