Distribution of rare earth elements in waters and bottom sediments of mineralized lakes in the eastern Transbaikal region (Russia)

Abstract

Contents of rare earth elements in waters and bottom sediments are maximum in the most mineralized soda lakes. It is shown that REE occur in waters mainly as carbonate (LnСО₃)⁺ and oxyhydroxide LnO₂H, LnO⁺, (LnO₂)^– complexes, whose activity in the La → Lu series changes in opposite directions. It has been determined that increase of mineralization leads mainly to higher concentrations of the dissolved HREE. Prevalence of the absolute values of MREE and HREE is recorded in basins with the development of bacterial processes. Geochemical barrier for the accumulation of LREE in waters can be represented by fluorcarbonates, whose saturation degree in the soda lake waters can be several orders of magnitude higher than the solubility products (SP). Oxidative and reductive settings in lakes are favorable for the formation of Ce(OH)₄ and Ce(OH)₃, respectively.