Experimentation and Modelling of U, Th and Lanthanides Transport in Fissured Rocks: Influence of Complexation

Abstract

AbstractThree circulation experiments have been carried out between two drill-holes in a granite after hydraulic fracturation (Le Mayet de Montagne, France). We have injected together uranyl carbonate and Th, La, Sm, Eu, Dy and Yb EDTA complexes. Amounts of tracers were different in each run. Recovery curves are similar for Th and lanthanides, but have a delayed peak and an increased tailing for uranium. For rare earth elements, recovery rates increase with increasing stability of the complex used as tracer. Recovery rates increase also with increasing amount of tracer. Those features are explained by non linear and non reversible sorption. The importance of complexation is demonstrated. Strong organic complexing agents enhance trace elements mobility.