Distribution of trace elements and the influence of major-ion water chemistry in saline lakes

Abstract

Although the water chemistry in saline lakes can differ drastically due to subtle differences in inflowing water conditions, the concentrations, distributions, and geochemical behaviors of trace elements in such environments are poorly understood. In this study, the influence of major-ion chemistry on the trace element distribution in saline lakes is examined based on major and trace element concentrations and geochemical modeling in three carbonate-rich saline lakes located in Mongolia and Turkey. The results are compared to data reported from other carbonate-rich and carbonate-depleted lakes. The concentrations of U and oxyanions (V, Mo, and W) in carbonate-rich saline lakes are several orders of magnitude higher than their contributing rivers and seawater. By contrast, their concentrations in carbonate-depleted saline lakes are lower than those in rivers and oceans. The high U concentrations in carbonate-rich saline lakes are possibly attributed to the formation of (magnesium-)uranyl-carbonate complexes, and the high oxyanion concentrations are likely a result of the high pH of lake water preventing them from being adsorbed onto solid phases such as suspended particulate matter and sediment. Strontium and Ba concentrations are lower in carbonate-rich saline lakes than in river water and seawater, but relatively higher in carbonate-depleted lakes. Incorporation into aragonite and/or calcite, adsorption onto solid phases, and formation of carbonate minerals are possible mechanisms that may account for the lower concentrations of these elements in carbonate-rich lakes. These results help elucidate the influence of water chemistry on trace element distribution in saline lakes.