The Propagation of Pollution in an Alluvial Aquifer. Distance Effect

This work of hydrogeology consists of a study of the migration of elements in solution in a saturated natural porous medium. An experimental trace in the alluvial water-table of the Marne river showed that there was strict sedimentary control of the transfer. An effect traditionally attributed to scale change could be observed even within the guides. Closer analysis led to doubts as to the constancy over time of the dispersive parameters. A new formula was then used to describe the distribution of a tracer injected intermittently and briefly into a guide, which could be considered as a flat medium with constant flow. The dispersive properties of a guide are here characterized by a function of time: the temporal law of dispersion. This dependence on time in fact indicates a relation with the distance covered by the average point of the tracer cloud: this is the "distance effect".