Soils of Lakeside Depressions of Pulsing Chloride Lakes of Internal Runoff in Central Asia: Morphology, Physical-Chemical and Geochemical Features

Abstract

Data on saline soils of drainless lakeside depressions, which are formed in areas of extra continental climate with a cyclic 25–30-year change in the level of lakes within the arid and humid climatic phases, were obtained first. Different types of soils are shown to be formed on the landscapes adjacent to highly mineralized chloride lakes of southeastern Trans-Baikal Region: on superaqueous–subaqueous positions– gleyic solonchaks (Gleyic Solonchak (Loamic, Chloridic)); on superaqueous – humus–gley saline soils (Calcaric Mollic Gleysol (Arenic, Endosalic, Sodic)); on eluvial-superaqueous – light-humus saline soils (Fluvic Kastanozem (Epiarenic, Amphiloamic, Sodic)). Salinity degree of the soils under the study is different. Salinity chemistry is sodium taking into account cations. Anion content in solonchaks and upper horizon of humus-gley soil is mostly chloride. Soda-chloride and chloride-soda anion composition prevail in other soils. Gleyic solonchaks have strongly alkaline pH values, high content of carbonates, and a sharp dominance of Na+ among exchangeable cations. Many chemical elements are concentrated in the solonchakous horizon (Sr, S, Li, Mg, Ca); a high content of As is a regional feature. The humus-gley saline soil has the same properties as the light-humus saline soil in terms of physico-chemical parameters, and in terms of elemental composition and texture as solonchaks. This is due to it functions periodically in a semihydromorphic or hydromorphic regimes when changing the arid and humid phases. The high level of groundwater contributes to the enrichment of soils with the elements typomorphic for lake waters. The paleohydromorphic stage of development has been established to be recorded in lower layers of light-humus saline soil in the form of a high content of easily soluble salts and carbonates. The geochemical specialization of soil-forming rocks is associated with the significant accumulation of As, as well as concentration of Li, Ba, and Pb. It was also revealed that low Ca/Sr ratio is their geochemical feature. The use of cluster analysis of indicators of soils under the study revealed that both dynamic and stable soil parameters are reflected in humus-gley soil and it is recommended for monitoring of the dynamics of endorheic lakeside ecosystems in Central Asia with cyclic climatic phases.