ABSTRACT
More than 40 % of Slovenia is covered with carbonate rocks, urbanisation is proliferating thus increasing pollution. Previous facts result in intensified research of solute transport in fractured and karstified rocks. Laboratory experiments were made to study behaviour (sorption) of tracers in porous media as a preliminary study for in-situ tracer experiments in fractured rocks and final modelling of mass transport.
Experiments were carried out in the laboratory of Institute for Mining, Geotechnology and Environment in three permeameters which were connected in a series. Each permeameter was 1,5 m long and permitted individual sampling. Huge reservoirs containing fluid fed the flow which was propelled through gravitation. Constant flow was maintained through uniform fluid levels in the supply and outlet reservoir. Salt and uranine were utilised as tracers. Two different concentrations of salt and uranine water solutions were used. Three porous materials of different grain size distribution from the nearby limestone quarry were used as porous media with 99,3% concentration of CaCO3. The grain size distribution of applied material was in range between 0,160-4 mm and 4-8 mm, whereas part of the material was a mixture of both ranges with an even distribution.
During the tests various measurements of parameters like flow, pressure, temperature, pH, conductivity, oxygen content, alkalinity, acidity and uranine content were constantly performed. The experiment with salt water solution confirmed that there was no sorption. Conductivity of uranine solution increased after teginning of the experiment and then stabilised at a value 20% higher than the initial value. Experiments with uranine water solution indicated very fast sorption and desorption. Based on this fact this process was assumed to be connected only to the grain surface. Because of detection problems, the results so far can not be determined. Hence, additional batch-tests are planned to confirm the sorption process.
