Marina Kolpakova

Geochemistry and chemical evolution of saline lakes of Western Mongolia

This paper presents data on the major and trace element composition of saline lakes of western Mongolia. The main geochemical types of lakes distinguished in the study are soda-, chloride-, and sulfaterich lakes. Lake water equilibria with major carbonate, sulfate, chloride, and other rock-forming minerals were calculated. The results show that the major factors controlling the formation of each lake type include evaporation and water-rock interaction processes, and the latter factor plays a critical role in freshwater and soda lakes and only a minor role in chloride lakes. Special attention was given to the soda lakes and the factors controlling lake water chemistry.

Uranium in saline lakes of Northwestern Mongolia

Analysis of major- and trace-element compositions of water in hypersaline soda closed basin lakes of Northwestern Mongolia and Chuya basin (Gorny Altai) shows high enrichment in 238U (up to 1 mg/l). Proceeding from new data, uranium accumulation in water has been attributed to (i) location of the lakes and their watersheds in potential provinces of U-bearing rocks and (ii) uranium complexing with carbonate in presence of carbonate (bicarbonate) anions. Among the explored hypersaline soda lakes of the area, the greatest uranium resources are stored in Lake Hyargas Nuur (about 6000 ton).

Thermodynamic modeling of the behavior of Uranium and Arsenic in mineralized Shaazgai-Nuur Lake (Northwest Mongolia)

Highly mineralized closed lakes on the territory of ore regions of Mongolia are of special interest in relation to the search for nonconventional sources of metals. Water of soda Shaazgai-Nuur Lake contains ~1 mg/L U, and the content of the undesirable admixture of As is up to 300 μg/L. Uranium and Arsenic speciation in solution and in the bottom sediments of the lake was estimated using thermodynamic modeling, and a method of their separation was suggested. Calculation of the models of sorption of these elements by goethite and calcite showed that at pH 9.4 typical of natural water it could be effective only at a high concentration of FeOOH sorbent. In this case, at pH <5 and >8 (the area of U sorption), As may be removed by simple filtering of solutions from the suspension upon additional coagulation.

Zonal Features of Bog and Lake Water Chemistry Along a Transect from Boreal to Arid Landscapes in The South of Western Siberia, Russia

Western Siberia is a unique territory where more than 12000 water reservoirs are located. The region is characterized by high bogginess up to 90% in the north. Bog and lake systems are able to accumulate natural and technogenic resources, including trace elements and organic matter. The article presents the results of a surface water chemical composition along a 5-year monitoring. The obtained data allow concluding that dynamics of water chemistry is predetermined by their location in various landscape zones and subordinated to zonal distribution of such major landscape elements as moistening, evaporation, rate of groundwater flow, etc.

Geochemical features of Kulunda plain lakes (Altay region, Russia)

Geochemical specifics of lake water of the Kulunda Steppe territory (Altay region, Russia) are studied. The results show that in the territory mainly chloride and less soda lakes with sodium compound are developed. It is presented that calcite and soda saturation indexes (SI) of lake water increase with growth of pH, but decrease in such minerals as gypsum and barite. The opposite situation is typical for SI depending on the salinity. It is revealed that evaporation, secondary mineral formation and various biological processes have the greatest impact on accumulation of elements in solution.

Uranium in the mineralized lakes of Altai Krai

Data on the physicochemical properties (pH, Eh, salinity) and content of U and other trace elements (As, Li, B, Br, I, Sr) are provided for the mineralized lakes of the Kulundinskaya steppe of Altai Krai. The sodic lakes of the region are characterized by higher U238 contents (up to 4 mg/l). The U contents in the lake waters are positively correlated with the sum of carbonate and hydrocarbonate ions and the pH of waters and are negatively correlated with salinity. These data confirm the presence of an economic U-bearing zone of the ground reservoir oxidation located along the eastern slope of the Platovskoe uplift in the northwestern direction along the boundary with Kazakhstan.

Chemical composition and sulfur forms in saline lakes of Kulunda Plain (Russia)

1 Introduction On the territory Kulunda Plain,located to the south-west of the Ob’plateau,there are more than 3,000 fresh and salt lakes with water TDS range from 1 to 430 g/L.The interest in these lakes was associated mainly with the study of

Uranium in Saline Lakes of Mongolia and Adjacent Areas

1 Introduction Increasing demand for uranium raw materials for the nuclear industry has stimulated interest in non-traditional sources,including hydromineral ones[Qin,2009].Those are saline lakes located in the uranium ore districts.Accumulation of uranium in such lakes results from the leaching of uranium from the rocks by surface and ground

A review of the defining chemical properties of soda lakes and pans: An assessment on a large geographic scale of Eurasian inland saline surface waters

The aim of this study is to evaluate the definition of water chemical type, with particular attention to soda brine characteristics by assessing ionic composition and pH values on a large geographic scale and broad salinity (TDS) range of Eurasian inland saline surface waters, in order to rectify the considerable confusion about the exact chemical classification of soda lakes and pans. Data on pH and on the concentration of eight major ions were compiled into a database drawn from Austria, China, Hungary, Kazakhstan, Mongolia, Russia, Serbia, and Turkey. The classification was primarily based on dominant ions exceeding an equivalent percentage of 25 (> 25e%) of the total cations or anions, and the e% rank of dominant ions was also identified. We identified four major types: waters dominated by (1) Na-HCO3 (10.0%), (2) Na-HCO3 + CO3 (31.4%), (3) Na-Cl (45.9%), and (4) Na-SO4 (12.7%), considering only the first ion by e% rank. These major types can be divided into 30 subtypes in the dataset, taking into account the e% rank of all dominant ions. The major and subtypes of soda brine can be divided into “Soda” and “Soda-Saline” types. “Soda type” when Na+ and HCO3– + CO32– are the first in the rank of dominant ions (> 25e%), and “Soda-Saline type” when Na+ is the first in the rank of dominant cations and the sum of HCO3– + CO32– concentration exceeds 25e%, but it is not the first in the rank of dominant anions. Soda-saline type can be considered as a separate evolutionary stage between Soda and Saline types respect to the geochemical interpretation by saturation indexes of brines. The obtained overlapping ranges in distribution demonstrate that a pH measurement alone is not a reliable indicator to classify the permanent alkaline “soda type” and various other types of temporary alkaline waters.

The Main Factors of Uranium Accumulation in the Ishim Plain Saline Lakes (Western Siberia)

Hydrochemical analysis of the high-salinity lakes in the Ishim Plain (>250–300 g/L) located at the border with the Northern Kazakhstan uranium ore province is performed. The studies have shown that the main factor of concentration and redistribution of uranium in the lake basins of the Ishim Plain are the processes of intense salt deflation causing sanding of lakes and uranium depletion in the near-surface layer of the bottom deposits. The correlation between the hydroxide forms of uranium binding in the bottom lacustrine deposits of the Ishim Plain and the coffinite composition of the Semizbai deposit makes it possible to consider this province to be promising for the discovery of hydromineral uranium deposits.