A structure–property correlation has been developed, which makes it possible to choose the optimal values of the enthalpy of formation of alkali metal borates, for which, according to the data of various experimental works and reference publications, wide variations are observed. Using this correlation, the enthalpy of formation of unstudied alkali metal borates can be reasonably estimated. It has been found that the contribution of B 2 O 3 to the enthalpy of formation is the same not only for alkali metal borates but also for Ba, Ca, and Pb borates, for whose enthalpy of formation a structure–property correlation has also been established. This suggests the suitability of the obtained correlations for estimating the enthalpy of formation in the borate series, where the value is known only for one member of the series, as well as the possibility of estimating the enthalpy of formation of mixed borates of different metals.

—A 6-meter core of the Holocene sediments in Lake Dukhovoe is studied. The material composition of the core is heterogeneous and has clear bedding. Lacustrine sediments are represented by the upper 293 cm. Each bed of the sediments is subjected to microbiological analysis. A high total number of heterotrophic bacteria is revealed in the upper (0–15 cm) and deeper (110–150 cm) sapropel intervals. Sulfate-reducing bacteria are identified only in Chrysophyceae cysts. The CaO/Fe2O3 ratio shows the degree of “carbonate content” of bottom sediments. It is low in the lake sapropel (0.2), which indicates the geochemical specificity (carbonate-free sapropel). Na, Mg, Al, Si, Al, Ca, Fe, Mn, Zr, and Cr concentrations in sapropel are within the average concentrations for the Earth’s crust, shale, and oceanic pelagic clays, while U and Mo concentrations exceed them. Phytoplankton is enriched in phosphorus (biogenic element) and chalcophile elements (Zn, Cd, Sn, Sb, Hg, Pb, and Cu), which characterize the pollution of the modern atmosphere of the Baikal region. Diagenetic processes result in the transformation of the pore waters, namely an increase in mineralization as compared to lake water, an increase in the concentrations of biogenic components (HCO3-, NH4+, NO3-, and PO43-) and a decrease in SO42-. Pyrite framboid accumulations are revealed in organomineral sediments below the horizon of 200 cm, and iron phosphates represented by vivianite are identified in sapropel.

A composition–property relationship has been developed that makes it possible to select the optimal values of the standard entropy of alkali metal borates, for which available experimental and reference data vary in wide ranges. This relationship allows one to estimate the standard entropy of unstudied alkali metal borates with sufficient validity. To ensure the reliability of the relationship, a critical analysis of the initial data borrowed from reference books and original experimental works has been carried out. Experimental measurements of low-temperature heat capacity were processed to verify the reliability of the standard entropy values of alkali metal borates presented in the literature.

Министерство науки и высшего образования Российской Федерации Российское химическое общество им.Д.И.Менделеева Секция по химической термодинамике и термохимии Научного совета РАН по физической химии Сибирское Отделение Российской Академии Наук Институт неорганической химии им.А.В.Николаева СО РАН

A Gibbs free energy minimization approach realized in “Selector-C” software is used to study germanate melts and glasses of the K2O–GeO2 system. A database of the thermodynamic properties of structural units of germanate melts was compiled by according to the results of high-temperature Raman spectroscopy for the correction of physicochemical models. Three mechanisms for the introduction of potassium cations into the germanium-oxygen network are identified along with the effect of composition and temperature on these mechanisms. It is shown that the germanate anomaly maximum shifts with increasing temperature towards low-alkaline compositions due to the appearance of non-bridging oxygen atoms in the system.

Two cores of the Dulikha peat bog deposits, 4.0 and 5.2 m thick, were studied in detail. The reduction type of diagenesis has been established. Decomposition of the organic matter of the bog deposits begins already in the upper intervals of the section at the earliest stages of diagenesis. Microbiological studies of the peat bog revealed numerous organotrophic, ammonifying, nitrifying, and phosphate-mobilizing microorganisms as well as Fe-Ox and Mn-Ox microorganisms and showed the almost complete absence of sulfate-reducing bacteria (except for the lower intervals of the peat section). The processes of the nitrogen, phosphorus, and carbon cycles are more active than the sulfur cycle processes. The chemical composition of the bog water changes during diagenesis. The contents of HCO3-, NH4+, PO43-, NO3-, and C-org increase in the peat bog section, which is the result of the destruction of organic matter, leading to the transition of the most mobile and labile components into the bog water. The results of physicochemical modeling show that the high content of organic matter significantly changes the chemical composition of the bog water. The enrichment of the latter in Cu, Zn, Sr, Ba, As, Si, Al, and Pb indicates a diagenetic transformation of the bog deposits. A change of oxidizing conditions by reducing ones in the peat bog leads to the reduction of oxidized Fe (III) and Mn (IV) forms to mobile Fe (II) and Mn (II) forms and their subsequent migration from the solid phase of deposits into the bog water. With depth, the reduced S (II) forms become predominant in the peat, which indicates more reducing environmental conditions. The concentration of SO42- decreases in the pore water of the peat-underlying mineral deposits, which marks the beginning of sulfate reduction. This process, however, is very slow in the bog deposits because of the acid environmental conditions and the lower degree of transformation of organic matter.

The article focuses on the chemical composition of hydrosulfates formed in bottom sediments and soils as a consequence of sulfide minerals oxidation in mining waste rock dumps. An alkaline geochemical barrier formed under the dumps reduces pollution of natural-territorial complexes. High concentrations of Zn up to 1.29%, Cu-0.74%, and Cd-27.3 mg/kg are found in the hydrosulfates formed in the river bottom and in the soils. The percentages of exchangeable copper, zinc and cadmium in their total content are 33%, 28% and 22%, respectively. Metals are actively involved in lateral and radial migration, which is regulated by alkaline and evaporation geochemical barriers. The hydrosulfates’ mineralogical composition was studied using microscopy and thermodynamic modeling. Among the secondary minerals, gypsum and iron oxyhydroxides are of primary importance, and to a lesser extent barite, epsomite, and jarosite. Secondary minerals of Cu and Zn in scattering halos are not found, which indicates the leading role of adsorption processes in their phase transitions.

Dumps for coal-fired thermal power plant ash-and-slag mixture storage occupy large areas and require considerable costs. The chemical composition of such mixtures is quite diverse and includes a large number of chemical elements, thus providing ample opportunities to be used in various ways. In this article, the oxidation–remediation processes and melt formation in the Al-C-Ca-Fe-K-Mg-Mn-Na-P-Si-Ti-B-Cr-F-N-H-O system have been studied. The techniques of a model formation and numerical experiment performance, setting the initial conditions and limitations, p,T-scenarios of the processes, and analysis of the simulation results are shown. For better demonstration, a generalized model reflecting the most typical features of the ash-and-slag mixture melting processes is provided. A physical–chemical modeling method is based on finding the global minimum of the thermodynamic potential (Gibbs energy) of the modeled system on the set of limitations established by the system of mass balance equations. The melting process has been investigated under two scenarios: amorphous and crystalline phases. The results of the equilibrium composition of the system are given as a function of the ash–slag mixture melting temperature.

The evolution of peat deposits of the Vydrino bog (southern Baikal region) and concentration of elements in them are discussed. The bog peat massif more than 4 m in thickness formed mostly during the Holocene. The beginning of peat formation dates back to the late Allerod (13.1 ka). At present, the Vydrino bog is a biogeocoenosis of the high-moor type with a transitional peat deposit. We have established that the bog nonuniformly accumulated chemical elements during its formation. Concentration of Pb, Sn, Cd, Zn, and Sb in recent vegetation and in the upper layer of the peat bog is mainly due to forest fires and anthropogenic air pollution. The anomalous enrichment of peat with Zn and Cu in the Early Holocene (12.1-8.8 ka) horizons proceeded through the periodic inflow of thermal groundwater into the bottom part of the peat deposit. Authigenic Zn and Cu sulfides formed on the inner membrane of the cell wall of sphagnum moss. Geochemical modeling has shown that Zn and Cu sulfides can form abiotically.

The study of bottom sediments of Lake Baikal recovered by submarine drilling at the Selenga–Buguldeika saddle (core VER93-2 st. 24GC) allowed us to reconstruct the climatic events in the Baikal region in the last 20–25 k.y. On the basis of the data on distribution of chemical elements in the core section, the mineral composition of sediments was calculated by the physicochemical modeling method. A study of how ratios of clay minerals changed in the section allowed us to identify the Pleistocene–Holocene boundary, Bølling–Allerød postglacial warming, and Late Dryas cooling. The calculated data on mineral composition of bottom sediments from the core VER93-2 demonstrate a good fit to the X-ray diffraction analysis results. The proposed approach can be used in calculation of mineral compositions of other sedimentary sequences with known chemical composition.

The formation enthalpies, standard entropies, and standard heat capacities of alkali and alkaline-earth germanates were determined by regression analysis with allowance for error in the initial data (weights). The potentialities of the presented method of calculation appreciably grew due to the possibility to enhance the array of initial data independently of the crystal structure of compounds. The thermodynamic properties of alkali germanates were estimated for the first time and could be used in the physicochemical models of magmatic melts.

The chemical-technological features of using fluorine compounds in aluminum production have been studied. The modes and parameters of technological processes that significantly decrease the emissions of hazardous substances have been specified by the method of computer modeling. The methods for obtaining fluorides and optimizing their chemical and granulometric composition have been updated. The measures for improving the electrolysis technology that reduce losses of valuable components are developed.

A process of dissolution Severoonezhsk deposit boehmite-kaolinite bauxite by hydrochloric acid, as well as the processes that occur during open-air calcination, were investigated. A dehydration process has been studied, and the basic phase transformation temperatures were identified. Temperature and time of calcination influence on bauxite dehydration speed were determined. It is shown that the preliminary calcination increases the extraction ratio of alumina into solution up to 89%. Thermodynamic modelling of physical and chemical processes of bauxite decomposition by hydrochloric acid and the basic forms of aluminium speciation in solution were obtained.

The standard thermodynamic potentials of natural zeolites in universal stoichiometric representation are computed. The enthalpies are estimated using linear deconvolution into chemical elements for calibration minerals. The entropies are computed using the additive scheme for oxide components; the Gibbs free energies are computed based on the calculated standard thermodynamic functions and entropies of thermochemically simple compounds.

The biogeochemistry of organic lacustrine sediments (sapropels) has been poorly studied in Siberia. In this paper we show the specifics of sapropel formation caused by low pH and mineralization of water by the example of Lake Ochki in Cisbaikalia. The main sources of organic matter are zoo-and phytoplankton, which concentrate mostly basic chemical elements and also some alkaline, alkali-earth, and chalcophile elements and move them to the sediment. The calculated enrichment factors (EF) have shown that the lake plankton is strongly enriched with phosphorus and chalcophile elements. The calculations have also revealed a great contribution of the plankton to the elemental composition of sapropel (Me-bio, %): P (approximate to 100), Cd (57), Br (45), Hg (40), Se and Na (30), Zn (23), K (21), and Ca (15). Elements are rather uniformly distributed throughout the 3.2 m thick sapropel layer. Lithophile elements (Al, Sc, Ti, Y, Zr, Nb) and LREE are mostly from a terrigenous source. The high contents of mobile elements (Cd, Sb, Sn, Pb, Zn) in the upper part of sapropel are probably due to anthropogenic factors. The high Cu and Zn contents in some sapropel layers are probably related to the inflow of deep-level groundwaters, and the elevated contents of Hg, Cd, and Sb might have been caused by forest fires. (C) 2015, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

Thermodynamic modeling of physicochemical processes underlying the preparation of aluminum-containing solutions has been performed. It has been demonstrated that the major aluminum species in solution are aluminum chlorides and hydroxychlorides. Temperature-induced changes in the equilibrium composition of a solution has been studied.