REE distribution pattern in river sediments: partitioning into residual and labile fractions

To assess rare earth element (REE) distribution, fractionation during weathering processes and river transport, a sequential extraction procedure was applied to 36 river sediments collected from different rivers in Argentina, Brazil, France and Morocco. The results show that labile REE fractions are mainly linked to carbonates, iron oxides or organic matter according to the river. Moreover the leached REE do not behave as a coherent group: middle REE are mainly bound to carbonates or organic matter, whereas light REE (except cerium) are preferentially linked to organic matter and heavy REE and cerium are associated with iron oxide