Methoden zur Erkundung und Beschreibung des Untergrundes von Deponien und Altlasten. Teilprojekt 24/GC 2: Modelluntersuchungen zur Wirkung organischer und metallorganischer Schadstoffe auf das Mikrogefuege und die Rueckhaltewirkung von Tongesteinen. T. 2 Modellexperimente und Schadstoffanalytik. Abschlussbericht

The migration of chloroform and benzene through three different shales has been investigated by percolation experiments. The chemicals were used in form of hydrous solutions as single compounds, as mixtures and in combination with an acid and a tenside. The aim was to identify any alteration of the clay's microfabric which could influence the permeability of the rocks. The concentration of the pollutants in the water was below the saturation limit. In none of the experiments this concentration has been measured in the percolating waters. Therefore, the retaining capacity of the clay discs has never been surpassed. The measured concentration of the pollutants in the percolating water are due to an extreme tailing of the migrating front, cause by an inhomogeneous distribution of the pore channels and/or by diffusive transport. The retaining capacity of the clay is improved by the presence of autochthonous organic matter which could be proved by experiments using mixtures of clay and organic-rich silt. The volumes of water which percolate through a certain pore volume in a given time are not significantly influenced by the type of the pollutant used, however, changes of the microfabric can be detected by scanning electron microscopy. With that respect, a hydrous solution of chloroform and a tenside had the greatest effect. A former parallel fabric changed to a totally disturbed fabric. The results of the experiments can not directly be used to interpret the situation in a geological barrier beneath a waste deposit. The interaction between pollutant and clay observed at a micro scale level may be different at a macro scale level, as competitive processes like compaction, erosion and deposition might overprint the small scale alterations. Therefore, the experiments carried out are basic research orientated and may contribute to the understanding of the ongoing processes in geological barriers. (orig.)SIGLEAvailable from TIB Hannover: F96B864+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman