Uranium, Lithium, and Arsenic in Salt Lakes of Eastern Transbaikalia
Distribution analysis of lithium, uranium, and arsenic in water of mineral lakes of Eastern Transbaikalia that are different by mineralization degree, macrocomponent composition, and water pH was performed. Lithium is mainly concentrated in more mineralized chloride lakes, and arsenic and uranium - in less saline, i.e. soda, as established. According to thermodynamic calculations, lithium is mainly present in lakes as Li<sup>+</sup> ion; LiCO<sub>3</sub><sup>-</sup> acts as second biggest in soda water bodies, and LiCl - in chloride. Uranium is mainly found as uranyl tricarbonate ([UO<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub>]<sup>4-</sup>) and bicarbonate ([UO<sub>2</sub>(CO<sub>3</sub>)<sub>2</sub>]<sup>2-</sup>). Arsenic in oxidative environment of lakes is presented by hydroarsenate (HAsO<sub>4</sub><sup>2-</sup>), and in reductive hydrosulphuric - dihydrogen arsenite (H<sub>2</sub>AsO<sub>3</sub><sup>-</sup>). Lithium does not form its own minerals in lakes. Reducing environment, in which it is precipitated as uranium hydroxide (U(OH)<sub>4</sub>), may be a geochemical barrier for uranium. Sodium uranospinite (NaUO<sub>2</sub>AsO<sub>4</sub>) that may limit arsenic content in water too is likely to form under oxidative conditions. A single focus in the distribution of their contents in chloride lakes is observed for lithium and chlorine. Direct dependence of the concentrations of uranium and arsenic on the contents of hydrocarbonate and carbonate ions is typical of soda lakes. The lack of appropriate specialization in the catchment areas of most lakes with a wide variation of contents of lithium, uranium and arsenic in their water, and also the presence of direct dependencies on the contents of the main macrocomponents indicates the prevailing influence of geochemical environment in their accumulation, the formation of which is mainly determined by evaporative concentration of water and hydrolysis of aluminosilicate rocks. The prevalence of this or that process ensures the formation of a certain chemical type of lakes and the appropriate set of microelements.