The Beck mine, located in the Republic of Karelia, Russia, is an abandoned mining site with significant potential for environmental contamination due to the presence of potential pollutants in its waste rocks. In this study, we investigated the chemical composition of mine waters and waste rocks and developed a theoretical model to understand waterrock interactions and the release of potential pollutants. Water samples collected from various locations on the Beck mine property were analyzed for chemical composition and showed low concentrations of total dissolved solids with pH values ranging from 6.42 to 7.74. The chemical composition of natural waters was determined by ICP-MS, ICP-AES, ion chromatography, potentiometric titration, and spectrophotometry. Equilibrium kinetic modeling was used to simulate water-rock interactions. The model predicted the concentrations of major and trace elements, demonstrating that dissolution-precipitation and complexation are the primary mechanisms shaping the chemical composition of mine waters. The dynamics of dissolution-precipitation of Fe-containing minerals highlighted the importance of the duration of water-rock interaction, with stagnant mine waters exhibiting higher concentrations of heavy metals. In addition, the presence of dissolved organic matter played a critical role in the accumulation of iron and arsenic in the studied mine waters. Overall, this study highlights the utility of equilibrium kinetic modeling in understanding the behavior of heavy metals during water-rock interactions and provides valuable insights into the potential environmental impacts of abandoned mine sites such as the Beck mine.

Abandoned mines are sources of potentially toxic chemical elements, although the development of these objects was completed. The Lupikko I mine area (Karelia Republic, Russia) is an excellent example of such technogenic objects. It is one of the largest mines in the Pitkäranta area, which was abandoned more than one hundred years ago. The dump rocks here are characterized by significant mineral diversity. Disseminated ore mineralization of the study area contains heavy metals, which enter the natural waters due to the oxidative dissolution of sulfides. Dump rocks and water from the Lupikko I mine area were collected to research the behavior of toxic elements. The samples were analyzed using ICP-MS, ICP-AES, potentiometric titration, ionic chromatography, X-ray microanalysis, X-ray fluorescence, and SEM to obtain information about the geochemical environment. According to new data, the content of Fe, Zn, Cu, Pb, Cd, and Ni in the natural waters of the mine significantly exceeds the geochemical background. For a more detailed study of the behavior of heavy metals, equilibrium-kinetic modeling, which considers the dissolution rate of ore minerals and the accumulation of toxic elements over time, was applied. A comparison of modeling data and field observations agreed. It was also found that for accurate modeling of Fe behavior, it is necessary to consider the organic matter content. Despite some model limitations, such retrospective assessments allow us to approve the applicability of this method for forecasting estimates.

The technogenic impact of the development of the Lomonosov diamond deposit is associated with the discharge of quarry and drainage water into the river, which has a special conservation status. Earlier studies on the composition of bottom sediments showed that there are signs of increased accumulation of heavy metals and radionuclides at wastewater discharge sites. The purpose of this work was to predict changes in the composition of surface water and bottom sediment in the river during the further development of mining operations with brackish and salty water captured by drainage systems, the presence of which was established in the zone of their future influence. For this, a simulation of changes in the composition of the water in the river was carried out using the GEOCHEQ software package by minimizing the free energy of the system using a convex simplex algorithm. It was found that the maximum salinity of surface water can reach 1.51 g/L. In this case, the MPC of Cl−, Na+, SO42−, Mg2+, Sr, V, and U can be exceeded for fishery watercourses. The genetic basis of the accumulation of these components in solutions for mixing was considered. According to the calculations, when about 5000 m3/h of drainage water is discharge d into the river, the mass of precipitated chemical elements will be 56–191 t/h, including up to 2.1 t/h of iron; therefore, accumulation in the discharge zone must be controlled.

Equilibrium-kinetic modeling allows investigating metal behavior in the water–rock-organic matter system with time to evaluate anthropogenic effects on the environment. In the article, the interactions of stagnant mine drainage water of the flooded mine “Arsenic” with ore and gangue minerals were simulated using different organic matter incorporation approaches. If the model is closed to humic substances (no additional organic matter input), most fulvic acids are bound in the Fe fulvate complex. While under the removal of Fe fulvate from the model, the Cu fulvate becomes prevalent, the contribution of the fulvate complexes with Zn, Mg, and Ca also increases. This scenario simulates the organo-mineral complexes behavior well and allows identifying the sequence of metal binding to organic ligands as follows Fe > Cu > Zn > Mg > Ca. The second scenario imitates the constant input of organic matter to the model (open system regarding humic substances). The dissolved metal concentrations in the model solution are extremely high in comparison to the mine drainage water. This scenario demonstrates that excessive input of organic matter leads to the accumulation of the metals in a dissolved form and blocks the secondary mineral formation despite the faster dissolution of the primary minerals under a more acidic pH than in the first scenario. However, despite the differences between the model solution and the mine drainage water, this scenario is useful to address specific issues associated with changes in natural and anthropogenic conditions. Both scenarios show the importance of organic matter incorporation to the equilibrium-kinetic models.

To evaluate the effect of redox conditions at the sedimentation stage on uranium content and U/TOC ratio in marine source rocks, we analyzed the accumulation of uranium in modern marine bottom sediments formed in different redox conditions. The behavior of uranium from bottom sediments formed in oxidizing and sub-oxidizing settings has been studied on the sediments of the Upper Pleistocene–Holocene age accumulated in the coastal area of the White Sea (Kandalaksha Gulf). We studied the content of uranium, Eh, pH, TOC, C, H, N, and S element and isotope compositions and other parameters in two sampled columns of bottom sediments at a depth of 0–2.5 m. The composition of sediments was typical for the shelf zone where marine genesis mixes with the continental run-off. The upper layer of sediments (0–50 cm) were characterized by oxidizing conditions (Eh ~ 400 mV); with the increase in depth, redox conditions changed from oxidizing to reducing (−0 ÷ −200 mV). The uranium concentration in the upper layer was 1–1.5 ppm, U/TOC ratio varied in the range of 0.8–1.1 ppmU/%TOC. The uranium content and U/TOC ratio increased up to the values of 2.6 ppm and 1.4 ppmU/%TOC at a depth of 0.5–2.5 m, respectively, but the general content of uranium in the studied environment was close to the values characterizing continental run-off. The results obtained for the White Sea sediments were compared with the sediment of the Black Sea, formed in the anoxic conditions of hydrogen sulfide contamination. In these conditions, the uranium content varied from 10 to 20 ppm. The obtained data were interpreted using thermodynamic modeling of the uranium forms in the seawater at different pH and Eh. This study demonstrated that the change of redox conditions from oxidizing to reducing leads to increased uranium content due to a decrease in uranium’s solubility in water. These results show that oxidation–reduction potential could be one of the most important factors controlling uranium content in black shales formed in the marine environment.

Numerical chemical models for water-basalt interaction have been used to constrain the formation of stratified mineralogical sequences of Noachian clay-bearing rocks exposed in the Mawrth Vallis region and in other places on cratered martian highlands. The numerical approaches are based on calculations of water-rock type chemical equilibria and models which include rates of mineral dissolution. Results show that the observed clay-bearing sequences could have formed through downward percolation and neutralization of acidic H2SO4-HCl solutions. A formation of weathering profiles by slightly acidic fluids equilibrated with current atmospheric CO2 requires large volumes of water and is inconsistent with observations. Weathering by solutions equilibrated with putative dense CO2 atmospheres leads to consumption of CO2 to abundant carbonates which are not observed in clay stratigraphies. Weathering by H2SO4-HCl solutions leads to formation of amorphous silica, Al-rich clays, ferric oxidesioxyhydroxides, and minor titanium oxide and alunite at the top of weathering profiles. Mg-Fe phyllosilicates, Ca sulfates, zeolites, and minor carbonates precipitate from neutral and alkaline solutions at depth. Acidic weathering causes leaching of Na, Mg, and Ca from upper layers and accumulation of Mg-Na-Ca sulfate-chloride solutions at depth. Neutral MgSO4 type solutions dominate in middle parts of weathering profiles and could occur in deeper layers owing to incomplete alteration of Ca minerals and a limited trapping of Ca to sulfates. Although salts are not abundant in the Noachian geological formations, the results suggest the formation of Noachian salty solutions and their accumulation at depth. A partial freezing and migration of alteration solutions could have separated sulfate-rich compositions from low-temperature chloride brines and contributed to the observed diversity of salt deposits. A Hesperian remobilization and release of subsurface MgSO4 type solutions into newly-formed depressions could account for formation of some massive layered sulfate deposits through freezing or evaporation. This scenario explains the observed deficiency of salts in Noachian formations, a paucity of Hesperian phyllosilicates, and the occurrence of sulfate deposits in Valles Marineris troughs, chaotic terrains, and some craters of the Hesperian age. (C) 2016 Elsevier Inc. All rights reserved.

Discussed is the structure, analytical properties and functionality of the analytical information system (AIS) for calculating the structure and parameters of the hydroacoustic field for long-range distances with variable characteristics of the medium and its boundaries. Estimated is the accuracy of the results of a program for calculating the characteristics of a sea medium (the DALNOST program). Investigated are the parameters and structure of the hydroacoustic field, which were calculated from the in-situ measurements of the sound speed inside a vortex disturbance zone that was observed in the western part of the Sea of Japan. The obtained results indicate the practical importance of technique and the DALNOST program as a key element of the AIS structure and provide the possibility for its integration into the systems created for the monitoring of marine water fields to solve the research problems as well as the problems of developing the ocean environment in the interests of the marine science.

FREZCHEM is an equilibrium chemical thermodynamic model parameterized for concentrated electrolyte solutions [up to approximate to 20 moles/kg(H2O) (molality)] using the Pitzer approach for the temperature range from < -70 to 25 degrees C and the pressure range from 1 to 1000 bars. This subzero temperature model has been extensively used to explore cold geochemical processes and/or limits for life in the Arctic, Antarctica, Europa, and Mars. FREZCHEM contains environmental pathways for simulating temperature change, evaporation, and pressure change. The objectives of this work were to (1) adopt a better mathematical algorithm to calculate chemical equilibrium, (2) develop a more user-friendly Internet version, and (3) develop an archive for various model versions. We adopted a Gibbs free energy mathematical algorithm that significantly reduced convergence problems that existed with older versions of this model. An Internet site was developed at http://frezchem.dri.edu that simplifies model access and is more user-friendly than pre-existing FREZCHEM versions. At this Internet site, FORTRAN codes and instructions for using various FREZCHEM versions are archived. This effort will make this unique theoretical research tool readily and easily available, even to occasional users, now and in the future. (C) 2009 Elsevier Ltd. All rights reserved.

CHEMICAL EQUILIBRIUM CONSTRAINTS. A. C. McAdam, M. Yu. Zolotov, M. V. Mironenko, and T. G. Sharp, Atmospheric Experiments Laboratory, Code 699, Goddard Space Flight Center, Greenbelt, MD 20771, Amy.McAdam-1@nasa.gov, School of Earth & Space Exploration, Arizona State University, Tempe, AZ 852871404, Amy.McAdam-1@nasa.gov, Vernadsky Institute of Geochemistry & Analytical Chemistry, Russian Academy of Sciences, 19 Kosygin Str., Moscow 119991, Russia.

Theoretical geochemical modeling has been used to evaluate the formation conditions of amorphous silica during aqueous alteration of typical Martian igneous rocks at 0°C. The models show that some silica can form during low‐temperature alteration of mafic to ultramafic rocks over a large range of pH and water/rock ratios. Silica‐dominated deposits, like those found at the Columbia Hills in Gusev crater on Mars, could form at solution pH below ∼2 and water/rock ratios of ∼102–104. High‐water/rock conditions could represent acid flow through rocks, solution discharge from an acid spring, and/or surface flow of released solutions. Low pH favors dissolution of silicates and saturation of solution with respect to relatively insoluble silica, which then precipitates. Partial evaporation or freezing of released solutions would also cause precipitation of amorphous silica. Modeling shows that Ti oxides are also present in silica‐rich deposits. More soluble minerals (e.g., ferric oxides, phyllosilicates) could precipitate downstream from partially neutralized, evaporated, or frozen solutions. Temperatures above ∼0°C are not required to form abundant silica through acid alteration of Martian rocks.

Weathering of olivine basalt by H2SO4‐HCl aqueous solutions at the conditions of early Mars was investigated through numerical modeling in a system open with respect to CO2and O2only. The model includes dissolution rates of primary and secondary minerals and oxidation rate of aqueous Fe2+, as well as chemical equilibration among solutes, dissolved gases, and precipitates. The results reveal fast dissolution of Fe‐Mg minerals at low pH, followed by preferential dissolution of plagioclase at higher pH. Correspondingly, solutions evolve from acidic, Mg‐Ca‐Fe2+‐Fe3+‐Al3+compositions toward Na‐rich alkaline fluids. The period over which neutralization and mineral precipitation may occur is shorter at higher initial pH, lower water to rock ratios, and larger mineral surface areas. Early stages of weathering are characterized by the formation of amorphous silica, goethite, and kaolinite, while zeolites and carbonates form considerably later at higher pH, where silica dissolves. Slow oxidation of Fe2+causes precipitation of ferrous phyllosilicates. Comparison with Martian observations indicate that amorphous silica, Fe3+oxyhydroxides, and Mg‐, Ca‐, and Fe‐sulfates could have formed during multiple short‐term episodes of acid weathering that were terminated by freezing and/or evaporation. Throughout history, impact generation of oxidants (e.g., O2, SO3, NO2) caused formation of strong acids and incremental Fe2+oxidation, the processes that are not efficient during O2‐deficient periods of volcanic degassing. Although impact‐generated acid rainfalls could have caused intense weathering and erosion in Noachian time, dilution of acids and a prolonged existence of surface solutions favored local neutralization of solution, and formation, transport and deposition of clays.