Hydrogeochemical Indicators Research Articles

Exploring secondary contamination in river and spring waters: A novel phenomenon arising from seawater intrusion into deep coastal aquifers.

Seawater intrusion, characterized by the infiltration of a seawater wedge into deep coastal freshwater aquifers, poses a significant threat to water quality. Despite extensive research on this hydrogeological phenomenon, monitoring remains challenging, often requiring deep drilling that exacerbates aquifer contamination. This study proposes a novel approach for monitoring seawater intrusion based on hydrogeochemical indicators, specifically focusing on secondary contamination observed in river and spring waters along the Black Sea coast of Russia. Using mass spectrometry, we analyzed the abundance and concentrations of 71 elements, identifying key indicators of secondary contamination influenced by the low hypsometric altitudes of the region. In total, 30 river and spring water samples were analyzed. Notable findings include a positive correlation between excess trace elements and Cl- and SO42-, characteristic of seawater. River waters exhibited lower mineralization compared to spring waters, with consistently higher Mn/Br, Cs/Br, and ∑ rare earth element/Br ratios, serving as reliable indicators of secondary contamination. This study allowed us to propose a geochemical indicator (GIM) GIM=∑ Mn Cs REE/Br which reflects the secondary contamination intensity. The decrease in GMI dynamics indicates an increase in the impact of the secondary contamination process on surface and spring waters. This innovative approach minimizes the reliance on extensive drilling, providing valuable insights for the study and monitoring of seawater intrusion in coastal aquifers.

Quantifying the environmental fate and source of nitrate contamination using dual-isotope tracing coupled with nitrogen cascade model on the basin scale.

Nitrate (NO3-) contamination in riverine networks has threatened the environment and human health. Clarifying the NO3- source and environmental fate within the basin under different underlying surfaces is essential for water body protection, especially China's two mother rivers. A series of combination methods were established i.e., field survey, index measurements, isotope-tracing techniques, and material flow analysis in four typical basins to investigate the spatiotemporal variation and source of NO3- pollution and nitrogen cascade characteristics. The dual-isotope coupled with MixSIAR model revealed that manure and sewage were the major NO3- source in the irrigation basin (WY, 76.7%), hilly mountainous basin (YC, 52.3%), and plateau lake basin (DC, 48.7%). However, for the plain-river network basin (CZ), soil leachate was the main source (55.5%). In terms of the N losses to water within agri-environment system, livestock-breeding system in three basins made the biggest contribution among the systems, WY (77.3%), YC (47.3%), and DC (41.8%). While in CZ, about 34.4% of N was delivered from the crop-production system. The N cascade model verified the results of isotope-tracing techniques for each basin. The study provides new insight into NO3--tracing combining hydrogeochemical indicators, isotopic-tracing techniques, and material flow analysis and guides strategies for mitigating the negative impacts of NO3- pollution on aquatic environments on basin scale.

Some questions of the connection between mud volcanism and seismicity in Azerbaijan

The article discusses some issues of the genetic connection between mud volcanic activity in Azerbaijan and seismicity, the results of monitoring studies of mud volcanoes characterized by active gryphon-salsa activity between eruptions located in tectonic structures of different ages. For the first time, an anomalous change in Br and J, mainly associated with Paleogene-Miocene deposits, was established in the chemical composition of the studied waters based on hydrogeochemical indicators of volcanic activation. The established differences in the studied waters are associated with the location of mud volcanoes within different oil and gas bearing regions of Azerbaijan and the lithofacies features of terrigenous-carbonate rocks in mud volcanic breccia. The above measurements of the temperature of waters carried by mud volcanoes to the earth’s surface confirmed the previously obtained results: during quiet activity of volcanoes, fluids are carried out from Pliocene deposits, and when their gryphon-salsa activity is activated, they are diluted with fluids coming from the depths of the Paleogene-Miocene age. Analyzing various intervals of “rest” between eruptions of mud volcanoes, tracing changes occurring in small crater fields (cracks, subsidence, etc.), the seismogeological material we have accumulated allows us to make an estimated forecast (as a long-term one) of the eruption of a mud volcano within one year.

Hydrogeochemical characteristics and enrichment regularities of groundwater uranium in the Erlian basin, China

Groundwater is a key medium for the migration and enrichment of elements into ore bodies in sandstone-type uranium deposits, with anomalies of uranium elements and their associated components in water serving as indicators for exploring such deposits. The Erlian Basin, located in central-northern Inner Mongolia, is a crucial production area for sandstone-type uranium deposits in China. The groundwater flow system in the basin plays a significant role in the formation of uranium deposits. To study the hydrogeochemical characteristics and enrichment regularities of groundwater uranium in the Erlian Basin, 269 groundwater samples were collected. Hydrogeochemical analysis methods, such as Piper diagrams, Gibbs diagrams, and contour maps, were employed to determine the distribution characteristics and occurrence forms of groundwater uranium in the study area. The primary water chemistry types in the study area were HCO3–Ca•Na, HCO3–Na, HCO3•SO4–Na, and SO4•HCO3–Na•Ca. The distribution range of uranium content in groundwater in the study area was 0.1–453 μg/L (average of 53.08 μg/L). A comprehensive analysis, based on the direction of groundwater flow and changes in the redox environment, suggested that the higher uranium values in groundwater were distributed in the runoff and discharge areas, with uranium anomaly points existing in areas with alternating oxidation and reduction zones. These uranium anomaly points were in good agreement with the known large uranium deposits of Nuheting, Qiharigetu, Daoersu, and others, thereby predicting six other uranium hydrochemical anomaly points as prospective areas for uranium mineralization. The pH value distribution range in the study area's groundwater was 6.8–9.1, and the redox potential (Eh) value range was -126–52 mV, indicating that uranium exists in groundwater in the form of UO2(CO3)34− and UO2(CO3)22−. An increase in bicarbonate (HCO3−) is conducive to uranium dissolution. The enrichment and occurrence forms of uranium in groundwater are influenced by the concentrations of Fe and (Ca2++Mg2+), with uranium precipitation and enrichment occurring as the groundwater evolves and changes in the redox environment. The uranium content in deep wells is higher than in nearby shallow wells, indicating that deep water circulation is beneficial for mineralization. The pH, Eh, HCO3−, Fe, and other hydrogeochemical indicators are indicative of uranium enrichment; thus, they can be considered as reference bases when exploring for potential uranium resources.

Experience of using the Aptian-Albian-Cenomanian hydrogeological complex in the disposal of produced water from the Kamennoye subsoil area

The objective of the presented study is to assess the efficacy of the Aptian-Albian-Cenomanian hydrogeological complex in the disposal of surplus associated water generated in large quantities during oil production within the Kamennoye subsoil area.The necessity for utilising produced water within the Kamennoye subsoil area is justified by the accumulated volume of water currently exceeding 10 000 thousand m3. The water content in wells' production at the Kamennoye subsoil area is 52-55 %. Furthermore, further extraction will result in an increase in the water cut. One of the key challenges facing subsoil users is to minimise the negative impact of water disposal into the absorbing horizon.In the course of the study, the following tasks were solved: assessment of the natural geological and hydrogeological conditions of the Aptian-Albian-Cenomanian hydrogeological complex, analysis of the stability of the hydrogeochemical indicators of the groundwater in the complex based on the results of monitoring studies (since the 1960s), assessment of the compatibility of the produced water and the formation water by calculating the carbonate equilibrium of the system. The obtained solution of each of the above tasks indicates the rationality of using the Aptian-Albian-Cenomanian hydrogeological complex for the disposal of produced water. The article also emphasises the necessity of continuous improvement of the system for monitoring the condition of the absorbing horizon, as well as careful observance of all environmental protection measures, which is a prerequisite for preserving the natural balance of the subsoil of the West Siberian oil and gas basin.

Hydrogeochemical indicators of a nested groundwater flow system in arid and semi-arid regions: evidence from the Aksu River Basin, Xinjiang, China

Hydrogeochemical indicators of a nested groundwater flow system in arid and semi-arid regions: evidence from the Aksu River Basin, Xinjiang, China

Assessment of hydrogeochemistry in groundwater using water quality index model and indices approaches

Groundwater resources around the world required periodic monitoring in order to ensure the safe and sustainable utilization for humans by keeping the good status of water quality. However, this could be a daunting task for developing countries due to the insufficient data in spatiotemporal resolution. Therefore, this research work aimed to assess groundwater quality in terms of drinking and irrigation purposes at the adjacent part of the Rooppur Nuclear Power Plant (RNPP) in Bangladesh. For the purposes of achieving the aim of this study, nine groundwater samples were collected seasonally (dry and wet season) and seventeen hydro-geochemical indicators were analyzed, including Temperature (Temp.), pH, electrical conductivity (EC), total dissolved solids (TDS), total alkalinity (TA), total hardness (TH), total organic carbon (TOC), bicarbonate (HCO3−), chloride (Cl−), phosphate (PO43−), sulfate (SO42−), nitrite (NO2−), nitrate (NO3−), sodium (Na+), potassium (K+), calcium (Ca2+) and magnesium (Mg2+). The present study utilized the Canadian Council of Ministers of the Environment water quality index (CCME-WQI) model to assess water quality for drinking purposes. In addition, nine indices including EC, TDS, TH, sodium adsorption ratio (SAR), percent sodium (Na%), permeability index (PI), Kelley's ratio (KR), magnesium hazard ratio (MHR), soluble sodium percentage (SSP), and Residual sodium carbonate (RSC) were used in this research for assessing the water quality for irrigation purposes. The computed mean CCME-WQI score found higher during the dry season (ranges 48 to 74) than the wet season (ranges 40 to 65). Moreover, CCME-WQI model ranked groundwater quality between the “poor” and “marginal” categories during the wet season implying unsuitable water for human consumption. Like CCME-WQI model, majority of the irrigation index also demonstrated suitable water for crop cultivation during dry season. The findings of this research indicate that it requires additional care to improve the monitoring programme for protecting groundwater quality in the RNPP area. Insightful information from this study might be useful as baseline for national strategic planners in order to protect groundwater resources during the any emergencies associated with RNPP.

Hydrogeochemical Characteristics and Evolution of Karst Groundwater in Heilongdong Spring Basin, Northern China

Understanding the impact of natural processes and anthropogenic activities on geochemical evolution is vital for groundwater protection and utilization. This research was devoted to identifying the water quality status and the main controlling factors of the hydrochemical evolution of karst groundwater by combining hydrogeochemical indicators with multi-isotope analysis techniques in the Heilongdong Spring Basin, North China. The results showed that the karst groundwater in the area was of meteoric origin, and the dissolution of carbonate minerals was dominant in water–rock interactions. Meanwhile, the positive and negative cation exchange occurred in the process. The main hydrochemical types of karst groundwater were HCO3-Ca·Mg and HCO3-Ca in the recharge area, while the predominant hydrochemical types were the HCO3·SO4-Ca·Mg and HCO3·SO4-Ca in the runoff and discharge area. Under the influence of coal mining and other factors, the average concentrations of major ions kept rising in the runoff area where coal mines were distributed, and the SO42− concentrations of the karst groundwater changed the most in the study area. In addition, sewage from agricultural production and domestic sources had also negatively impacted the quality of regional groundwater in the runoff and discharge area, as evidenced by the increasing NO3− and Cl− contents in the Quaternary sediment groundwater, Permian bedrock groundwater and a small portion of karst groundwater. These results were helpful to explain the mechanism of gradual hydrogeochemical changes and provided a scientific basis for the effective management and utilization of karst groundwater.

A new large-volume equilibration method for high-precision measurements of dissolved noble gas stable isotopes.

Noble gases are widely used as physically based climate proxies, notably in dissolved water samples as tracers of past recharge temperature in groundwater and air-sea gas exchange processes in seawater. Recent advances in measuring large-volume samples of dissolved noble gas isotopic ratios at high precision have expanded the range of climate parameters that can be interpreted. We build on prior methods for measuring noble gas stable isotopes at high precision with a new large-volume equilibration (LVE) method wherein sample gases are equilibrated in the sample flask between the dissolved phase and the headspace. The original dissolved gas composition is determined by measuring the headspace gases and correcting for the equilibrium dissolved gas content of the discarded water using known solubilities and fractionation factors. We evaluate the accuracy and precision of this method with air-equilibrated water standards of known noble gas composition. Replicate air-equilibrated water standards and field measurements demonstrate that the LVE method achieves comparable precision to prior methods, with major advantages of measuring the Ne content as a constraint on excess air and allowing for long-term sample storage. Isotope ratios measured with the LVE method in replicate samples were consistent between two laboratories, and LVE elemental noble gas abundances agreed closely with replicate samples measured using established copper-tube methods and static noble gas mass spectrometry. The new LVE method enables reconstruction of past water table depths at ±1m precision along with excess air, recharge temperature, and age and hydrogeochemical indicators. It has wide application to investigating climate signals and physical gas exchange processes in groundwater and seawater.

ТЕМПЕРАТУРА И ХИМИЧЕСКИЙ СОСТАВ ТЕРМОМИНЕРАЛЬНЫХ ВОД ДАГИНСКИХ ИСТОЧНИКОВ (о. САХАЛИН) ПОСЛЕ ПРОВЕДЕНИЯ РЕКОНСТРУКЦИИ КАПТАЖНЫХ СООРУЖЕНИЙ В 2019–2020 гг.

The paper presents the results of the study of physical and chemical characteristics of thermo-mineral waters of the Daginsky field (Sakhalin Island) after the reconstruction of the captation structures in 2019–2020. The analysis of the data indicates the stability of the chemical composition of thermo-mineral waters before and after reconstruction works on the territory of springs. The thermo-mineral waters had a typical Cl-Na composition, and the values of the hydrogeochemical indicators did not exceed the range of values established by the analysis of data for these waters over a multi-year period (1958–2019). However, for most of the springs whose captation structures underwent reconstruction, a significant drop in the surface temperatures of thermo-mineral waters (by 5–15°C) was recorded. The indicated temperature anomaly is not related to changes in the origin of discharged thermo-mineral waters or to seasonal air temperature variation. The observed drop in temperatures may be a consequence of a decrease in the flow rates of the springs after construction work, as well as technically incorrect design of the thermal baths.

Hydrological regulation of nitrate sources, transformation and transport pathway in a karstic river

A comprehensive understanding of nitrate dynamics in rivers is vital for nitrogen management, especially for the karst zone with high leaching of nitrate producing potential risk to environmental quality. However, identification of the source-transformation-pathway of nitrate is limited in the karst rivers. Thus, a suit of hydrogeochemical parameters, including δ15N-NO3−, δ18O-NO3−, δ13C-DIC, δ18O-H2O, soil-related parameters (DOC) and geogenic ions (Mg2+, DIC), were used to identify nitrate sources and dynamics in the Wujiang River, a typical karstic river as a tributary of Changjiang River. The combined use of a conceptual model of normalized NO3− and DOC, and other hydrogeochemical parameters (δ13C-DIC, Mg2+, DIC) suggested that most nitrates were transported through the soil/epikarst pathway in the wet season, whereas >70 % of nitrates were transported through groundwater pathway in the dry season for Wujiang River. Nitrification and mixing were the dominant processes, meanwhile ∼31 % of nitrate was denitrified in the wet season in this study. The reanalysis of δ15N-NO3− and δ18O-NO3− values for reported karstic rivers in China and worldwide also revealed the predominant nitrification and denitrification in karst regions. The Bayesian model indicated that chemical fertilizer (CF, 42 %) and soil organic nitrogen (SON, 32 %) contributed the most in the wet season, while ∼60 % of nitrate originated from SON (31 %) and manure and sewage wastes (M&S, 30 %) in the dry season in the Wujiang River. The sustained contribution of non-point sources from nitrification through the soil/epikarst pathway might be related to the widespread porosities in the karst rivers. Thus, measures to reduce nitrogen leaching and improve fertilizer use efficiency should be considered, like water and soil conservation, slow-release fertilizer and nitrification inhibitors. Additionally, a suit of hydrogeochemical indicators proves to be helpful for identification of source, transformation and transport pathway of nitrate in the karst basin.

Enrichment of High Arsenic Groundwater Controlled by Hydrogeochemical and Physical Processes in the Hetao Basin, China.

Based on 447 samples collected from a shallow aquifer (depths from 0 to 150 m) in the Hetao Basin, Northern China, an integrated hydrogeochemical approach was used in this study to conceptualize the enrichment of high arsenic groundwater in the Hetao Basin. An unconventional method of distinguishing hydrogeochemical and physical processes from a dataset was tested by investigating the cumulative frequency distribution of ionic ratios expressed on a probability scale. By applying cumulative frequency distribution curves to characterize the distribution of ionic ratios throughout the Hetao Basin, hydrogeochemical indicators were obtained that distinguish the series of hydrogeochemical processes that govern groundwater composition. All hydrogeochemical processes can basically be classified as recharge intensity of groundwater, evaporation concentration intensity, and reductive degree controlling the spatial distribution of arsenic. By considering the three processes, we found that the concentration of arsenic was more than 10 μg/L when the (HCO3-+CO32-)/SO42- ratio was over 4.1 (strong reductive area). As the evaporation concentration intensity increased, the median value of arsenic increased from 10.74 to 382.7 μg/L in the median reductive area and rapidly increased from 89.11 to 461.45 μg/L in the strong reductive area. As the river recharge intensity increased (with the intensity index increasing from 0 to 5), the median value of arsenic dropped from 40.2 to 6.8 μg/L in the median reductive area and decreased more markedly from 219.85 to 23.73 μg/L in the strong reductive area. The results provide a new insight into the mechanism of As enrichment in groundwater.

Geodynamic prerequisites and reflection of signs of fluid migration in hydrogeochemical indicators of formation water in the Bukhara-Khiva region

The article describes the results of a study of changes in the composition and hydrogeochemical parameters of individual areas and fields of the Bukhara-Khiva region based on well materials. Vertical zonality of hydrogeochemical parameters associated with deep fluid flow and heat and mass transfer is noted. The manifestation of tectonodynamic conditions in the Mesozoic-Cenozoic history of the region, which served as a prerequisite for the formation of weakened zones (channels of deep heat and mass transfer) in the field of tensile stresses for the vertical migration of fluids and juvenile gases, is noted. A hydrogeological criterion for identifying zones of deep heat and mass transfer and vertical fluid migration is proposed. Keywords: wells; oil and gas; formation waters; fluids; hydrogeochemical indicators of formation waters; heat and mass transfer.

Hydrochemical and environmental isotopes characteristic of groundwater and controlling factors for waters’ chemical composition in the iron–copper mine area of Elazığ, SE Turkey

Environmental context Predicting the hydrodynamic structure of water resources based on water chemistry and isotope results is important for understanding their transport and effects on the hydrogeological system. According to the results of this study, hydrogeological characteristics of ground and surface water resources in the Zeryan Stream sub-basin in the iron–copper mining area and their geochemical evolution are mainly controlled by the weathering of silicate and carbonate minerals, and ion exchange. Rationale and hypothesis Groundwater is generally the most important water resource in mine areas, and its circulation processes need to be studied in detail for rational resource exploitation. This work tested the hypothesis that the evolution of groundwater chemistry and recharge by using hydrogeochemical indicators and isotope tracers together are affected by the hydrogeochemical processes that may have taken place during the water-rock interactions in the Zeryan Stream Sub-basin, where the Iron-Copper mine is located. Methodology It used approaches such as hydrochemistry, Piper diagrams, saturation index, ionic ratios, and environmental isotopes to analyze groundwater origin and hydrochemical processes affecting water chemistry. Fifty-seven water samples were collected from 19 points during wet and dry periods. Results Results indicated that the dominance of cations and anions in the mine water follows the trend Mg2+ > Ca2+ > Na+ > K+ and SO42− > HCO3− > Cl−, and most of the water samples are Mg-Ca-HCO3-SO4, Mg-Ca-SO4-HCO3, and Ca-HCO3. Discussion Evaluation of analyzed groundwater chemical data showed that dissolution or precipitation of silicate minerals dominated in the hydrochemical evolution of groundwater, dissolution of carbonate minerals was a secondary process and to a lesser extent, ion exchange processes played a role. The δD and δ18O isotopic contents indicated that the water samples were controlled by local atmospheric precipitation, and affected by secondary evaporation during the recharge process. Tritium levels indicated some well waters are recharged from older groundwater resources from water-rock interaction and residence time. Findings The findings of this study were provided to decision-makers in order to design sustainable implications for groundwater utilization based on the sub-basin.

Динамика физико-химических параметров термоминеральных вод Дагинского месторождения (до проведения реконструкции источников 2019–2020 гг.)

The paper presents the results of studies (2017 and 2019) of the physicochemical characteristics of the thermomineral waters of the Daginsky field, obtained before the reconstruction of the springs in 2019–2020. The obtained data were compared with the data from the studies of previous years (1958–2014) in order to study the dynamics of the measured indicators in over time. It was found that the waters of the Daginsky field are characterized by the constancy of the chemical composition and reservoir temperatures calculated by means of hydrochemical geothermometers. This fact indicates a stable hydrogeological regime of the field. For many years, spatial hydrogeochemical heterogeneity has also been preserved within the field, which consists in the differences in some physicochemical indicators (surface temperatures, concentrations of Na+, Cl–, SO42–, HCO3–, etc.) of the thermomineral waters discharged in different sites (Northern, Central, Southern). It is shown that the content of microcomponents (B, Br–, Li+) in the studied waters, which were measured in different laboratories (or with different methods of chemical analysis) can differ significantly. The most reliable estimates of reservoir temperatures of the Daginsky field are obtained using Na-K, K-Mg and SiO2 hydrochemical geothermometers. The reservoir temperatures mainly range from 60 to100 °С, which corresponds to a circulation depth of the thermomineral waters of about 2–3 km. These researches provide a basis for the studying the further dynamics of hydrogeochemical indicators of the Daginsky field, including after the reconstruction of the thermomineral springs.

Search for hydrogeochemical indicators of the genetic relation between mud volcanism and oil and gas fields

The paper reports the results of a comparative analysis of the chemical and isotope composition (δ180 and δD) of mud volcanic waters and formation waters from oil and gas fields. Studies show that the waters discharged by mud volcanoes in most cases are very similar to formation waters. The most characteristic geochemical traits of both waters are elevated concentrations of hydrocarbonate ions, iodine, boron, bromine, and a low content of sulfate ions.

Tracing Nitrate Source and Transformation in Glacier Runoffs on the Tibetan Plateau Using Triple Nitrate Isotopes

Glaciers are the largest reservoir of fresh water on earth. Global warming accelerates glacier retreat and enhances glacier runoff, which heavily impacts the geochemical cycling in downstream ecosystems. Nitrate is the main form of nitrogen in glacier runoff, while little is known about its source in high-altitude regions. Here, we measured triple nitrate isotopes (δ 15 N, δ 18 O, and Δ 17 O) in ten geographically separated glacier runoffs on the Tibetan Plateau with the altitudes ranged from 2,409 to 5,564 m. The isotope results were combined with hydrogeochemical indicators to assess the primary sources and transformation processes of nitrate. Results showed that all the glacier runoffs exhibited low nitrate concentration, which ranged from 0.3 ± 0.0 to 1.5 ± 0.8 mg·L -1 . The SIAR model results indicated that soil organic nitrogen and atmospherically oxidized nitrate accounted for 67% of nitrate in the runoffs, whereas human-related source (i.e., chemical fertilizers) contributed 33% on average. Significant geospatial differences in the contribution of chemical fertilizers were identified, with their contributions being significantly higher in the monsoon domain (43% ± 3%) than that in the westerlies domain (22% ± 8%). Furthermore, δ 18 O of nitrate ranged from -15‰ to 15‰, this suggested that the nitrification process is responsible for the nitrogen transformation in Tibetan glacier ecosystems. Our study reveals the source of nitrogen in Tibetan glaciers and highlights the substantial impact of human activity on glacier nutrient cycling. Our work may shed light on the understanding of nitrogen cycling in downstream ecosystems.

Multi-isotopes and hydrochemistry combined to reveal the major factors affecting Carboniferous groundwater evolution in the Huaibei coalfield, North China

Both natural processes and anthropogenic activities have significant effects on groundwater evolution in coal mining regions. In this study, the primary controlling mechanism of the groundwater chemistry evolution for the Carboniferous groundwater in the Huaibei coalfield, North China was proposed based on the hydrogeochemical indicators combining with multiple isotope tracers. The diversity of hydrochemical types indicates the complexity of the hydrogeochemical environment in the groundwater, which is recharged by precipitation infiltration with minimal evaporation according to the distributions of δD and δ18O. Additionally, ion correlation analysis suggests that minerals dissolution and cation exchange between Na+ and Ca2+ are the dominant processes within that groundwater. The hydrochemical and δ13CDIC characteristics of the groundwater demonstrate that HCO3− is mainly controlled by the dissolution of carbonate minerals and soil CO2, and the proportion of the latter is believed to be dominated by the hydrogeologic conditions. Similarly, the values of SO42− and δ34SSO4 indicate that a small portion of SO42− in the groundwater in the northern part originates from the meteoric precipitation, while it is mainly derived from the dissolution of gypsum in the southern part. Furthermore, mining activities also alter the groundwater level and flow conditions through pumping and drainage, which enhances the interaction between groundwater and aquifer lithologies, thereby affects the hydrogeochemical processes. The findings of this work are of great significance for promoting the safe exploitation of deep coal resources and the sustainable utilization of groundwater in the Huaibei coalfield, as well as the most of other coalfields in North China.

HYDROGEOLOGICAL FEATURES OF THE DEVELOPMENT OF THE BOROK QUARRY (NOVOSIBIRSK)

The hydrogeological features of the development of the Borok granite quarry, the oldest in Siberia, are considered in the article. It was found that the hydrogeological conditions of the quarry are quite difficult. Two aquifers: alluvial deposits of the Quaternary age and Paleozoic granites were identified according to the geological structure of the quarry, assessing the main hydrogeochemical indicators of the drainage waters of the quarry. The volume of water inflows for the last 70 years has been analyzed. The role of fissure-vein waters of Paleozoic granites, Quaternary aquifer and atmospheric precipitation during the year is substantiated.

Гидрогеохимические критерии поиска и разработки углеводородных месторождений: обзор, анализ и перспективы использования на острове Сахалин

The paper discusses the directions of hydrogeochemical researches used to solve actual problems of the oil and gas industry: assessment of the oil and gas potential of territories, localization of oil and gas trap, prediction of the phase composition of hydrocarbon fields, control the development process of hydrocarbon fields, etc. Based on the literature data, the analysis and systematization of the main hydrogeochemical indicators of groundwater with oil and gas prospecting significance, as well as used already at the stage of development of oil and gas fields, have been carried out. The most efficiency of the application of hydrogeochemical researches in oilfield practice is achieved with the integrated use of various indicators. On the example of researches of the oil and gas potential of Sakhalin Island, it is shown that the hydrogeochemical data of the middle of the 20th century, obtained by outdated chemical analytical methods, cannot always be considered reliable. In this regard, additional researches are required to update the relevant hydrogeochemical data in this region.