Particle reworking in Great Lakes sediments: in-situ tracer studies using rare earth elements

A rare-earth-element (REE) tracer technique for measuring sediment transport rates is described. It utilizes the high neutron-capture cross section of samarium oxide and neutron activation analysis to trace the burial and lateral transport rates of surficial sediments in the littoral (scuba diver depths) and profundal (manned submersible depths) of the Great Lakes. The REE tracer was prepared as a pellet encapsulated in a cylindrical cake of ice. This method permitted the tracer to be carried to the lake bottom without any loss and allowed the tracer particles to be gently deposited at the sediment-water interface as the ice melted. The purpose of the measurements is to determine the mass balance of contaminants in the lakes. After 23 days, 11 undisturbed punch cores were collected and analyzed. The results are presented, and needed improvements of the method are identified