Evgeniya S. Sidkina

The abundant water resources of the Northern Ladoga region are subject to anthropogenic pressures and geogenic influences associated with the distinctive geochemistry of the bedrock. Spring water is widely used for domestic purposes, including drinking. These waters are characterized by low salinity with a dominant Ca–HCO₃ facies often enriched in SO₄²⁻. Geochemical signatures reflect sulfide and fluorite mineralization, particularly in springs near Pitkäranta, and are associated with elevated concentrations of Zn, Mn, Rb, Y, Cd, Mo, U, and Cu. NICA-Donnan speciation modeling indicates extensive complexation by dissolved organic matter (DOM) of Fe, Ni, Cd, Cu, Pb, U, Th, Co, and Al, with particularly stable complexes of Cu, Pb, U, and Th. Positive matrix factorization (PMF) modeling indicated that mining and its associated industrial heritage are the primary sources of potentially toxic elements, followed, to a lesser extent, by transport and road infrastructure, as well as natural sources.

The study investigates the chemical composition of natural waters of rivers, streams, lakes, including the littoral zone of Lake Ladoga, and artificial reservoirs (ponds and flooded quarries) in the Pitkyaranta District of the Republic of Karelia. The aim was to assess water quality refer to the standards established for the surface waters of fishery importance and recreational use, as well as to identify patterns in the formation of chemical composition during low-water period. It was found that the formation of the chemical composition and the exceedance of maximum allowable concentrations (MACs) for some trace elements are mainly associated with natural factors and processes (the spread of ore mineralization in the study area, the waterlogging of the territory, the atmospheric transport of salts, the hydrological feeding regime of the studied water bodies and watercourses). The most frequently observed concentrations in excess of the MACs were recorded for Fe, Al, Mn, Cu, Zn, F^–, and Mo with respect to the quality standards for surface waters of fishery importance; and Fe and Al, with respect to the standards established for recreational waters. In some cases, the incompliance for water chemistry characteristics with the quality standards is due to anthropogenic factors, namely, the impact of historical mining production, the road network, and the infrastructure of Pitkyaranta. This indicates the need for particular attention to monitoring water quality in the zone of influence of both existing and historical enterprises, and also demonstrates the importance of reclamation of abandoned mines and their waste rock dumps. Reclamation of the waste rock dumps of the historical mines and development of the adjacent territory, in addition to environmental significance, has tourism and recreational potential, since the ore mining sites are the historical and cultural heritage of the region. The natural water bodies are the most favorable as recreation surface waters; however, only the littoral zone of Lake Ladoga and water of Lakes Nietjarvi, Peryalampi and Valkamalampi fully meet the quality standards in terms of chemical indicators among the water bodies considered. Higher values and variations of the total pollution index and a wider range of pollutants were observed in the watercourses and artificial reservoirs compared to the natural water bodies. In particular, they showed concentrations in excess of the MACs for the substances of the hazard classes 1 and 2 (F^–, Li, Cd, Cr, U). If the most common pollutants—Fe and Al—are excluded from consideration, the water quality of all natural water bodies and almost all watercourses will be assessed as satisfactory, which indicates the need to discuss the introduction of regional MACs at least for these elements, since they do not have a toxic effect on human body.

Natural spring waters of the Northern Ladoga region are poorly studied and are actively used for drinking and domestic purposes by the region’s population, which necessitates comprehensive isotope–geochemical investigations. Isotope measurements have shown that the range of δ¹⁸O values in spring water varies from –13.52 to –12.53‰ with corresponding δ²H values from –95.4 to –87.7‰. For comparison, in the tested rivers and streams, the δ¹⁸O values vary from –12.71 to –10.48, and δ²H, from –88.8 to –76.5. At the same time, the figurative points of the springs on the δ¹⁸O and δ²H diagram are located along the local meteoric water line, which means their meteoric origin. Estimates of the ratio of “winter” to “summer” infiltration waters in the spring water balance show that “summer feeding” dominates by ≥75%. Hydrocarbonate and calcium predominate in the ionic composition, which is very typical for ultra-fresh waters, and a distinctive feature is the relatively high content of sulfate ion, Zn, Ni, Cu, Pb, Mo, W, As, and Cd in some samples. However, due to the high rate of water exchange, the concentrations of potentially toxic elements are quite low. The assessment of non-carcinogenic risks showed that water from springs can be used by the population for drinking purposes.

Mining activities have long-term impacts on the environment even after the active stage. Historical mines developed in the 19th and 20th centuries for tin, copper, and mainly iron ore are located in the Pitkäranta area (Karelia, Russia). These objects are considered in our research as natural–anthropogenic sites of long-term water–rock interaction. Waters from flooded mines are the subject of this research. Redox conditions, pH, dissolved oxygen content, conductivity, and water temperature were determined during field work. The chemical composition of natural waters was determined by ICP-MS, ICP-AES, ion chromatography, potentiometric titration, and spectrophotometry. Our investigation showed that the mine waters are fresh and predominantly calcium–magnesium hydrocarbonate; most samples showed elevated sulfate ion contents. Circumneutral pH values and the absence of extremely high concentrations of heavy metals indicate neutral mine drainage. However the calculation of the accumulation coefficient showed the highest levels for siderophile elements relative to the corresponding data of the geochemical regional background. Moreover, zinc has the highest content in the series of heavy metal(loid)s considered. The maximum concentration of zinc was determined in the water of one of the shafts of the Lupikko mine, i.e., 5205 µg/L. The accumulation of heavy metals occurs in the process of long-term interaction of water–rock–organic matter under conductive redox conditions. Overall, the research highlighted the relevance of investigating the geochemistry of historical mines in the Pitkäranta area both from the perspective of environmental safety and the preservation of mining sites for scientific and educational purposes.

The speciation of chemical elements in the waters and its dependence on the dissolved organic matter were studied by a complex of methods, involving thermodynamic calculations and experimental fractionation. The waters were studied at the abandoned and flooded Herberz Mine in the Pitkäranta district, Karelia, Russia. The regional natural waters are typically highly humified. In combination with the unique metallogeny of the rocks, this makes the mine suitable for solving the formulated problems. The eastern shaft of the Herberz Mine was sampled to a depth of 20 m to trance the changes induced by changes in the redox conditions. One of the geochemical characteristics of the waters is their relatively high concentrations of trace elements and a low salinity (TDS, total dissolved solids). All water samples from the Herberz Mine contain elevated concentrations of Zn, Fe, Mn, Cu, Ni, As, and W. Experimental fractionation and thermodynamic simulations of the speciation of chemical elements led us to identify metals whose accumulation most strongly depends on organic matter (OM). Both methods have demonstrated that U, Th, Cu, Ni, and Y show a high chemical affinity to OM. Metals (Cd and Fe) weakly bonded to the functional groups of natural OM, with the predominance of electrostatic bonding and a higher proportion of carboxyl bonds, are most susceptible to transformations with changes in geochemical conditions.

Actual analytical methods make it possible to precisely determine a of chemical elements contained in water, including for the purpose of assessing the ecological state of the environment in connection with mining activities. The object of this research is the natural waters of the gold deposit “Novye Peski” located in the Pryazhinsky region (Republic of Karelia, Russia). Analytical data indicate that the geochemical background of the region is exceeded for most of the chemical elements. Research results indicate that the geochemical background of the region is exceeded for most of the considered chemical elements and ions, which can be divided into three groups: 1) the highest concentrations were determined in quarry water (Zn, As, Mo, U, Ni, Cu, Sr, Li, B, as well as Ca 2-); 2) the content is at the same level in all and other cations, HCO3samples (Al, Si, V, Ti, Ba); 3) the highest content in stream and tailing pond (Fe, Mn). We assume that the main factor influencing the behavior of elements of the first group is mining, and for the third is the presence of dissolved organic matter high content with the formation of metal-organic species in water.

In the mining industry, one of the principal issues is the management of the waste generated during ore concentration, which represents a potential source of environmental pollution. The most acute issue originates from the mining heritage in the form of dumps formed of mining tailings that were created before the introduction of waste storage standards and may be located in urban areas. This research investigated this problem using the example of the tailings dump “Krasnaya Glinka”, located in a residential area of Pitkäranta (Karelia, Russia) in close proximity to the shoreline of Lake Ladoga. A complex approach, including the investigation of the natural water of the study area and tailings material and an experiment simulating the interaction of this material with atmospheric precipitation, allowed us to obtain the first data on the current status of the tailings dump and its surroundings and to identify environmental pollutants. This research used XRF, XRD, and EPMA analytical methods for assaying the tailings materials obtained from the dump and ion chromatography, potentiometric titration, ICP-MS, and AES for the water samples. The results show the influence of the tailings dump’s materials on the formation of the environmental impact—in the water from the area of the tailings dump, increased concentrations of chalcophilic elements are observed, for example, Zn up to 5028 µg/L. Based on this study of the tailings dump’s materials and the conducted experiment, an attempt is made to connect the chemical compositions shown in the natural water data with the specific mineral phases and processes occurring during supergene transformations in the tailings storage. As a result of the conducted research, it was found that despite more than 100 years of exposure of the tailings materials under natural factors, mostly atmospheric precipitation, equilibrium with the environment has not come. The processes of extracting toxic elements and carcinogenic mineral phases into the environment are continuing. In the process of studying the tailings materials, it was found that they are probably of economic interest as a technogenic source of W and Sn due to the contents of these components exceeding industrially significant values in the exploited fields.

Link for citation: Soldatova E.A., Sidkina E.S., Kiriukhin B.A., Maximov P.N., Krivenok L.A., Ivanov V., Tananaev N.I. Geochemical conditions of Sullar spring: formation of authigenic minerals and methane fluxes. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 10, рр. 16-33. In Rus. Relevance and the research object. Interpermafrost aquifers and areas of their discharge with seasonal ice covers are special permafrost-hydrogeological and hydrochemical systems that are not typical for the thick continuous permafrost zone of Central Yakutia. Differences in chlorofluorocarbon content indicate the anaerobic conditions of some springs suggesting microbial degradation of these compounds by methanogenic bacteria. In the discharge area of such springs, a sharp change in the geochemical conditions takes place leading to a transformation in the water chemical composition and boosting the processes of authigenic mineral formation in this buffer area. In current work we considered the geochemical system of the Sullar spring – the most northern and the least studied among interpermafrost groundwater discharge zones of the Lena River right bank. Intensive accumulation of authigenic minerals was found in the Sullar discharge area during field research. It was Fe compounds with bacterial mats as an opalescent film. Some researchers state the connection between the transformation of Fe compounds during permafrost melting and the migration and transformation of organic matter, including its consumption by microorganisms with further methane emission. We assumed that there is a relationship between the authigenic mineral formation and the content and emission of methane in the discharge area of the spring. This research is the first comprehensive description of the hydrochemistry of the interpermafrost water of the Sullar spring. The aim of the research was to explore influence of geochemical conditions and microbial communities on formation of authigenic minerals and methane fluxes, in particular the effect of the change of geochemical conditions due to groundwater discharge on Fe precipitation and to analyze the relation of that process with methane fluxes. For this purpose, we study water chemical composition of the Sullar spring, measure methane fluxes from water surface and analyze mineral and microbial composition of secondary mineral crusts and bottom eluvium collected near water sampling points. Methods. The main element content was determined by ion chromatography. The concentrations of the bicarbonate ion and dissolved carbon dioxide were calculated by the equilibrium modeling method based on the pH and Eh values of the system. The content of trace elements was measured by mass spectrometry with inductively coupled plasma. To identify seasonal and annual variability, a retrospective analysis of the water chemical composition of the Sullar spring for the period from 1962 to 2020 was carried out. Methane fluxes were measured using the chamber method. The methane concentration was determined by gas chromatography with a flame ionization detector. The features of the secondary mineral crusts and bottom eluvium were determined using a petrographic microscope. The chemical composition of individual mineral phases was evaluated using a scanning electron microscope equipped with a detector for energy dispersive X-ray spectral microanalysis. The DNA concentration was measured on a fluorimeter. Amplicon libraries were generated by polymer chain reaction with universal primers for the V4 region. Equilibrium modeling was carried out using the HCh software. Ссылка для цитирования: Геохимические условия источника межмерзлотных вод Суллар: вторичное минералообразование и потоки метана / Е.А. Солдатова, Е.С. Сидкина, Б.А. Кирюхин, П.Н. Максимов, Л.А. Кривенок, В. Иванов, Н.И. Тананаев // Известия Томского политехнического университета. Инжиниринг георесурсов. – 2023. – Т. 334. – № 10. – С. 16-33. Актуальность и объект исследования. Межмерзлотные водоносные горизонты и области их разгрузки с приуроченными к ним сезонными наледями подземных вод – особые мерзлотно-гидрогеологические и гидрохимические системы, нетипичные для мощной сплошной криолитозоны центральной Якутии. Различия в содержании хлорфторуглеродов указывают на анаэробный статус некоторых источников, предполагающий микробную деградацию этих соединений метаногенными бактериями. В области разгрузки таких источников происходит резкая смена геохимической обстановки, приводящая к трансформации химического состава вод и запускающая процессы вторичного минералообразования в этой буферной области. В данной работе рассмотрена геохимическая система источника Суллар – самого северного и наименее изученного в группе источников межмерзлотных вод правобережья р. Лены. В ходе экспедиционных исследований в зоне разгрузки источника нами была обнаружена интенсивная...

This paper confirms the regularities of the formation of increased concentrations of strontium (Sr) in fresh groundwater used for drinking water supply, depending on the time they are residen in the carbonate deposits of the aquifer. On average, every thousand years, the Sr concentration increases by 2.1–3.5 mg L⁻¹. In addition, high strontium content is positively correlated with altitude and well depth and negatively correlated with redox conditions in the aquifer. Large relief elevations are associated with the development of marginal moraine deposits from the Last Glacial Period composed predominantly of clay, which contributes to a decrease in water exchange. The high Sr content is associated with the dissolution of significant formations of celestite and strontianite, up to their ore occurrences. For this reason, the saturation indices (SIs) for celestite and strontianite correlate with TDS and rise to − 1.42 and 2.05, respectively. Low Sr values do not correlate with the residence time of groundwater in the aquifer or the depth of wells and tend to depressions in the relief, with a virtual absence of overlying sediments and positive Eh values, which indicates an active water exchange. The low level of Sr is associated with the dissolution of gypsum, calcite, and dolomite containing strontium as an impurity. This causes the SIs for gypsum, calcite, and dolomite to correlate with TDS, while for celestite and strontianite, the SI drops to − 5.02 and − 0.92, respectively. The established patterns make it possible to more reasonably choose places for the construction of water wells to obtain drinking water of standard quality. Graphical abstract

The development of mineral deposits causes changes that are comparable to natural exogenous geological processes, and prevail over the latter in local areas of intensive mining activity. In this article, a diamond deposit is selected, developed by quarries of great depth, and a forecast is made of the impact of drainage water discharge on changes in the composition of surface water and bottom sediments during the entire period of development of the deposit. Modeling was performed according to various scenarios, taking into account changes in the total dissolved solids of groundwater from 0.5 to 21.7 g/kg H₂O. Thermodynamic calculations were carried out using the HCh software package. The role of dissolved organic carbon in the migration of chemical elements and the effect of DOC on the precipitation of chemical elements from mixed solutions is given. It has been established that fulvic acid completely binds to Fe in the Fe(OH)₂FA⁻ complex in all types of natural waters and under all mixing scenarios. With humic acid, such a sharp competitive complex formation does not occur. It is distributed among the various elements more evenly. It was determined that the mass of precipitating iron in the presence of DOC decreases by 18–27%, and its precipitation in winter is more intense. In contrast to Fe, the precipitation of Ca, Mg, and C from solutions with DOC is higher in summer, and there are more of them in the solutions in winter. This study contributes to a better understanding of the behavior of heavy metals in surface waters and sediments under anthropogenic pressures in order to improve the sustainable management of water resources in the face of anthropogenic activities.