Fracture-matrix interaction as a significant feature of mass transport in carbonate-bound luxembourg sandstone

The Luxembourg Sandstone is a calcareous sandstone formation deposited during the Early Jurassic on a shallow marine shelf. Due to its excellent pore content, it forms the most important groundwater reservoir of Luxembourg. However, it has a complex mass transport due to its fractures and their importance for groundwater transport. This work uses laboratory experiments to investigate the fracture-matrix interaction and its effect on solute transport in the near-surface aquifer. Matrix parameters such as pore volume, effective diffusion coefficient, permeability coefficient, and pore diameter are determined on drill cores and freshly fractured material from a quarry. Mass transport and the interaction of the matrix with the fractures as the primary transport pathway are investigated in a laboratory-scale single fracture test using tracer tests. Mass discharge can be attributed to back-diffusion from the matrix into the fracture water, flow through porous matrix-fracture boundary zones, and the fracture itself.