. J H.Laboratory experiments will be performed to determine if and how trivalent REE are fractionated during their geochemical interactions in waters and sediments. Field data have shown that fractionation occurs during weathering and soil development, during early diagenesis of redox.reactive marine sediments and in the water column of marine and estuarine basins with oxic/anoxic boundaries. Little is known about the reactions and chemical factors which govern fractionation of trivalent REE. Fractionation, in turn, is a unique characteristic of REE series and forms the basis for understanding geochemical cycling of these important elements. Emphasis will be placed on developing laboratory simulation of natural processes at natural concentrations of solution and solid phases. Radioactive isotopes of REE will be used as tracers for the different reactions.
