Triassic Aquifer Research Articles

Characterizing Natural Hydrogen Occurrences in the Paris Basin From Historical Drilling Records

AbstractThis study investigates natural hydrogen (H2) occurrences in the Paris Basin, using Optical Character Recognition (OCR) technology to analyze an extensive, yet underexploited, database that contains historic drilling records. The potential of natural hydrogen has been largely unexplored in conventional oil and gas wells. Utilizing the in‐house CVAGeoDB database based on public well data, which includes well logs, mudlogs, and End Drilling Reports (EDRs) in PDF image format, we applied the Tesseract‐OCR Engine to convert these documents into searchable formats for efficient data analysis. Our analysis revealed several H2‐bearing wells across French sedimentary basins. The hydrogen occurrences in the Aquitaine Basin may be explained by the geological context and in particular the presence of a mantle body at shallow depth. On the contrary, the detection of H2 in the Paris Basin cannot be explained in a straightforward manner as the presence of ultramafic or U‐rich rocks is poorly documented so far. In the Paris Basin, H2 has been detected in four main formations: the Lusitanian, the Dogger, and Triassic aquifers as well as in the basement. The highest hydrogen concentration (52 vol%) was measured in the Dogger aquifer. These wells are primarily located along the Bray Fault, indicating at least a structural influence on H2 distribution. Finaly, the presence of serpentinzed dunite from the Lizard complex associated with the bedrock may have played the role as a source for H2. This research demonstrates the effectiveness of OCR in reassessing historical drilling data for natural hydrogen exploration, highlighting the need for comprehensive exploration methodologies in this emerging field.

ABOUT THE MAIN RESULTS OF DEEP DRILLING IN THE TERRITORY OF THE PREDVERKHOYANSKAYA OIL AND GAS AREA

This article presents the results of drilling wells in the Predverkhoyanskaya oil and gas area, where deep exploratory drilling for oil and gas was started in 1954 at the Kitchan, Sangar and Ust-Vilyu structures pre-pared by the seismic survey in combination with structural core drilling.According to the results of deep drilling in the Predverkhoyanskaya oil and gas area, the section of the sedimentary cover was studied, and ideas about the material composition of the foundation upper part were obtained. The pro-spects of oil and gas potential are evaluated: the reservoir properties are possessed by rocks of the subsalt Nizhnevendsky, Vendian-Lower Cambrian terrigenous and carbonate complex-es, which are associated with industrial oil and gas potential in nearby fields.The following fluid-bearing complexes are distinguished in the sedimentary section of the Preverkhoyanskiy trough: Permian (P), Lower Triassic (T1), Triassic-Lower Jurassic (T2–3–J1), Middle Upper Jurassic (J2-3), Lower Cretaceous (K1).Deposits of the Lower Triassic aquifer complex are deposited on Permian formations. The capacity of the complex is variable, due to the structural features of the Lower Triassicsediments, and it has not been established with-in the Predverkhoyanskiy trough. Thermobaric data were not obtained during the test. Reser-voir pressures are close to hydrostatic. Reser-voir temperatures, as in the Permian complex, increase from west to south-east to the Predverkhoyanskiy trough from 50 °C to 95 °C.The deposits of the Middle-Upper Triassic – Lower Jurassic aquifer complex are more widely developed. During the sampling and test-ing of oil and gas exploration wells, water and gas inflows were obtained from the deposits of the complex, including industrial ones on Ust-Vilyuiskaya, Sobo-Khainskaya Square. The flow rates of water inflows reached 300 m3/day (Sangarskaya 2), gas inflows up to 1800000 m3/day (Ust-Vilyuiskaya area). In the Sobo-Khainskaya 1 well, an industrial gas in-flow was obtained from the interval of 1328–1349 m.The prospects for oil and gas exploration at the Preverkhoyanskaya oil and gas area are associated with its northern part (Setas struc-ture), on which the Setas parametric well No. 1 with a design depth of 4000 m is being laid, and its southern part, where it is advisable to drill 2 parametric wells with a planned depth of 3000 m.

The Historical Aspect of the Impact of Zn and Pb Ore Mining and Land Use on Ecohydrological Changes in the Area of the Biała Przemsza Valley (Southern Poland)

The article presents the impact of Zn and Pb ore mining and land use on ecohydrological changes in the area of the Biała Przemsza valley in the historical aspect, with particular emphasis on the period 1941–2021. GIS was used to analyse the maps to identify spatial and temporal changes in land use. The following trends could be observed in the spatial development of the Biała Przemsza valley: rapid urbanisation and industrialisation in the 21st century, marked reduction in the surface area of arable land and sands, and dynamics of the increase in the surface area occupied by forests. Notable changes occurred in the plant ecosystems between 1941 and 2021 due to land management. Groundwater level lowering due to mining activity resulted in the change from wet meadows to fresh or dry xerothermic grasslands, while forest cover increased by 4% within the catchment area. The hydrographic network evolved. After the commissioning of the Zn-Pb ore mines Olkusz and Pomorzany in the 1960s and 1970s, a regional depression cone with an area of 400 km2 was formed, while the maximum groundwater inflows to the mines reached 360 m3/min. Changes in the hydrodynamic conditions have resulted in changes in the hydrogeochemical regime of the Triassic aquifer manifested by increased levels of, e.g., SO4 and Cl. Wastewater with lignosulphonate compounds from the paper factory caused periodic degradation of some of the water flowing into the Pomorzany mine. As a result of mining activity, the character of some sections of the Biała Przemsza river changed to an infiltrating one, the quantitative depletion of groundwater resources within the range of the mine drainage cone occurred, river springs disappeared, and the flow in the river decreased. At the same time, mine water was discharged to the tributaries of the Biała Przemsza. A radical reduction in the flow of the Biała Przemsza and its tributaries occurred after the decommissioning of the Zn-Pb ore mines at the turn of 2021 and 2022.

Conceptual Hydrodynamic Model with Hydrochemical and Isotopic Signatures of the Triassic and Silurian-Devonian Groundwater Systems in Northwestern Saudi Arabia

Groundwaters from an Upper Silurian-Lower Devonian sandstone-siltstone aquifer and an Upper Triassic calcareous unit in the northwestern part of Saudi Arabia were geochemically assessed to define their provenances, lateral migration pathways, secondary alteration processes, and potential connectivity between both aquifers. The water samples were analysed for their hydrochemical properties (n = 74), 87Sr/86Sr ratios (n = 14), 14C activities and noble gases (n = 5). The Devonian aquifer is of NaCl and Na-Cl-HCO3 water type, while the Triassic aquifer is of NaCl and Ca-Cl-SO4 type. A general increase in water salinity from 189 mg/L toward maximum concentrations of 5546 mg/L in the NW confirms potential recharge from Devonian outcrop areas with a lateral fluid migration from SE to NW. Principal component analysis (PCA) with nine variables (Na+, Ca2+, Mg2+, K+, Cl−, and SO42−, alkalinity, TDS, pH) revealed variations in TDS reflecting the observed lateral groundwater migration. A positive correlation between SO42− and Ca2+ loadings on PC2 illustrates the presence of gypsiferous water. An inverse correlation between Ca2+ and Na+ loadings on PC2 indicates cation exchange processes for both aquifers. The sandstone/siltstone-composed Silurian-Devonian aquifer groundwater was found to be dominantly undersaturated in terms of aragonite, calcite, and dolomite. Overlapping Ca/HCO3 and Na/Cl ratios for some Devonian and Triassic samples indicates mixing between both aquifers along the Hercynian Unconformity in the northwestern part of the study area. A depth-related increase in 87Sr/86Sr ratios (from 0.708611 to 0.711577) suggests the presence of water-rock exchange processes between the infiltrating groundwater and 87Sr/86Sr-enriched underlying units, likely by vertical segregating fluids. The general lack of measured 14C activities suggest the occurrence of recharge prior to Late Pleistocene Pluvial period or, more likely, a complete 14C decay during groundwater flow from recharge to the present discharge area. Elevated 4He/20Ne and depleted R/Ra ratios (0.01 to 0.05) of the groundwater indicate crustal radiogenic influence from the interaction with crustal fluids. 4He is produced in-situ with negligible contribution from the mantle. Evidence of noble gas isotopic fractionation was reflected in one water sample, indicating a preferential loss of some of the lighter isotopes of Ne and Ar.

Identifying groundwater recharge and discharge zones using geostatistical simulation of hydraulic head and its derivatives

Identifying groundwater flow directions and the locations of recharge and discharge areas is critical for effective groundwater management. Groundwater flow directions, the concavity and the locations of extrema (i.e., minima and maxima) can be assessed using the first and second derivatives of the hydraulic head surface. We developed a geostatistical method to jointly simulate hydraulic head and its first and second derivatives using sequential Gaussian simulation. The derivative values were used to identify regional groundwater flow directions, and the second derivative test was used to probabilistically map the concavity and the locations of extrema in the hydraulic head surface. By comparing the mapped concavity and extrema to known features, it was possible to attribute areas of recharge and discharge to physical features of the system, such as rivers, lakes and geological outcrops. This was applied to Triassic aquifers in the Galilee Basin (Queensland, Australia) to delineate the likely recharge and discharge areas. This provided an objective assessment of likely recharge and discharge zones and their uncertainty, which is an important addition to a region where the hydrogeology has been the subject of much conjecture.

Hydrogeochemical Characteristics of Geothermal Waters from Mesozoic Formations in the Basement of the Central Part of the Carpathian Foredeep and the Carpathians (Poland) Using Multivariate Statistical Methods

The subject of this study is the chemical composition of potentially geothermal waters of the Mesozoic basement of the central part of the Carpathian Foredeep and the Outer Carpathians regions. The research objectives were: (1) to identify statistically significant differences between the chemical composition of waters from the Cretaceous, Jurassic, and Triassic aquifers, and between the waters of both regions; and (2) the discovery of zones indicating active water exchange—attractive due to the operational efficiency of wells. Knowledge of the chemical composition of water allows for the preliminary identification of areas of interest for the exploitation of water for recreational, healing, and heating purposes. The research methods used were: (1) statistical tests and (2) methods of multivariate data analysis, such as the Kruskal–Wallis test and Principal Component Analysis (PCA). The performed tests and statistical analyses allowed us to draw conclusions about significant differences between the chemical composition of waters from the Cretaceous, Jurassic, and Triassic aquifers, and the basement of the Carpathian Foredeep and the Outer Carpathians. They indicated the existence of a zone with symptoms of active water exchange. Before establishing the fact of active exchange of waters in this zone, further research should be undertaken.

Critical Tectonic Limits for Geothermal Aquifer Use: Case Study from the East Slovakian Basin Rim

The Pannonian basin is a major geothermal heat system in Central Europe. Its peripheral basin, the East Slovakian basin, is an example of a geothermal structure with a linear, directed heat flow ranging from 90 to 100 mW/m2 from west to east. However, the use of the geothermal source is limited by several critical tectono-geologic factors: (a) Tectonics, and the associated disintegration of the aquifer block by multiple deformations during the pre-Paleogene, mainly Miocene, period. The main discontinuities of NW-SE and N-S direction negatively affect the permeability of the aquifer environment. For utilization, minor NE-SW dilatation open fractures are important, which have been developed by sinistral transtension on N–S faults and accelerated normal movements to the southeast. (b) Hydrogeologically, the geothermal structure is accommodated by three water types, namely, Na-HCO3 with 10.9 g·L−1 mineralization (in the north), the Ca-Mg-HCO3 with 0.5–4.5 g·L−1 mineralization (in the west), and Na-Cl water type containing 26.8–33.4 g·L−1 mineralization (in the southwest). The chemical composition of the water is influenced by the Middle Triassic dolomite aquifer, as well as by infiltration of saline solutions and meteoric waters along with open fractures/faults. (c) Geothermally anomalous heat flow of 123–129 °C with 170 L/s total flow near the Slanské vchy volcanic chain seems to be the perspective for heat production.

Геохимическая роль метеорных вод как фактор формирования пустотного пространства коллекторов нефти и газа

The features of the chemical composition of formation waters of the Upper Permian, Lower and Middle Triassic aquifers within individual structures of the Malozemelsk-Kolguev monocline of the Timan-Pechora oil and gas bearing basin are examined. It is shown that the aquifers that, despite their remoteness from the recharge areas, had experienced repeated processes of dipping and uplifting of the territory, preserved the infiltration waters, but significantly transformed ones. To identify their genetic profile and determine the relationship with the processes of catagenetic changes, hydrochemical coefficients and indices of water saturation of calcium carbonate and calcium sulfate are calculated. It is established that the examined infiltration waters are characterized by high aggressiveness, dissolution ability, leaching and removal of main minerals. It is pointed out that the consequence of these processes is the formation of secondary void space and the creation of high capacitive and filtration properties of rocks. The universality of geochemical interaction between water and rocks in thermodynamically open geological systems is emphasized and it is confirmed by individual geological examples that the heterogeneity of the hydrochemical field can act as a cause of screening zones of oil and gas accumulation, as well as provide appropriate conditions for localization of hydrocarbon fluids.

Assessment of groundwater salinization using PEST and sensitivity analysis: case of Zeuss-Koutine and Mio-Plio-Quaternary aquifers

Groundwater is the main source of water in arid regions. In the Southeast of Tunisia, Zeuss-Koutine and Mio-Plio-Quaternary underflow aquifers of Jeffara plain are considered the main source of water supply for drinking, agriculture, and industry. The study area is characterized with several known groundwater pollution sources (industrial and wastewater effluents, domestic wastes, etc.). This paper explains how sensitivity analysis can be useful tools in risk assessment of groundwater salinization. The main concern is whether the contamination sources threaten the drinking and irrigation water wells of the area. The groundwater flow and transport model of salts is set up to answer this question using MODFLOW, MT3DMS, and PEST tools. The preliminary results of the model are associated with large uncertainty. Thus, the effect of boundary conditions, dispersivity and porosity, on the migration of pollutants was investigated to estimate this uncertainty and build confidence in the model results. All variables and parameters were given a value from a range of realistic values. The sensitivity analyses show that the model is more sensitive to the salinity of the infiltrated water and the dispersivity. The results showed that the salinization process affects the areas close to the Mediterranean Sea and the Sebkha of Oum Zessar. The recharge areas have the low salinity values ranging from 1 to 2.5 g/l. High salinity reaching 3 g/l in the southeast of the Zeuss-Koutine aquifer is due to the inflow from the Triassic aquifer through Tajra fault.

The assessing of the quality of geothermal reservoirs on the example of the Lower Triassic aquifer in the Mogilno-Łódź Trough (Polish Lowlands)

Petrographic and petrophysical investigations of the aquifers allow to estimate their productivity and infectivity, as well as allow for better recognition of the origin of the chemical composition of geothermal waters. Deep deposition of the Lower Triassic sediments in the analysed area (locally above 5000 m b.s.l.) is conducive to high temperatures (above 90°C) within the reservoir and causes deterioration of reservoir parameters. The Lower Triassic geothermal reservoir consists of fine and mixed grain- size sands and sandstones layers from 10 to 650 m thick; depending on the depth. The water within the reservoir exhibits mineralization ranging from 2 to over 100 g L-1 and its temperature ranges from 30 to 100°C. The mineralization of waters varies from 140 g/dm3 (Warsaw basin) to over 350 g/dm3 in the deep zones of the basin (axial fragments of the Mogileńsko-Łódź trough). The average permeability of reservoir layers in the Polish Lowlands is 145.5 mD.

The effect of geochemical processes on groundwater in the Velenje coal basin, Slovenia: insights from mineralogy, trace elements and isotopes signatures

This study investigated the mineralogical and isotopic composition of groundwater and precipitation to identify and constrain geochemical processes within stacked Pliocene and Triassic aquifers in the Velenje coal basin. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopic analysis revealed that suspended matter in the Pliocene aquifer consists of feldspars and quartz, while dolomite, calcite and feldspars are present in the aquifer dewatering Triassic strata. The concentrations of trace elements in Triassic and Pliocene aquifers range from highest to lowest Zn > Fe > Ni > Al > Ba > Mn > B>Li > Mo > As with the majority of trace element concentrations below international drinking water health guidelines. Multivariate principal component analysis indicated that concentrations of Mn, Ba, Eu, Cs, Y, Li and T, pH, conductivity and dissolved oxygen in samples were the best chemical parameter for distinguishing the two aquifers. A significant positive correlation (p < 0.05) was found between Ni, Mn, Co, Zn, As and Mo. Groundwater in the Pliocene aquifer likely has an external source of carbon based on the δ13CCO2 values (− 12.3 to − 3.6‰). The groundwater also has detectable levels of dissolved methane with isotopic values (− 77.7 to − 51.4‰ δ13CCH4; − 247 to − 162‰ δ2HCH4) consistent with microbial methanogenesis. The groundwater in the Triassic aquifer has tritium values (up to 4.1 TU 3H) characteristic of modern recharge (< 50 years), while the lack of detectable 3H (0 TU) in the Pliocene aquifer is consistent with longer residence times.

The origin of high hydrocarbon groundwater in shallow aquifer: experimental evidences from water-rock interaction.

The current studies had already revealed the hydrocarbons could migrate from relatively high hydrocarbon potential stratum to shallow groundwater by corrosion emission and extraction emission in karst area and further impact on human health. Then, the comprehensive experiments were used to understand the mechanism and process of hydrocarbon emission as a continuation of a long-term study on original high hydrocarbon groundwater in shallow Triassic aquifer, taking northwest Guizhou, China, as a reference. The results determined water-rock interaction that lead to the hydrocarbon emission into groundwater with salinity acting as the main driving force. Relatively high salinity promotes the rock corrosion and hydrocarbon emission in the study area. The hydrocarbon emission process varied with different strata, as the results show that the hydrocarbon uniformly distributed in T2g3 than that in T1yn4. Furthermore, the stratum with uniformly distributed hydrocarbon would likely contain high hydrocarbon groundwater, as determined by the process of sedimentation. In addition, "corrosion rate estimation method" and "mineral constituent estimation method" were firstly employed to estimate the hydrocarbon concentration in groundwater to date. Compared with the hydrocarbon concentration of local groundwater samples (0 to 0.14 mg L-1), the result of "mineral constituent estimation method" was analogous to measured value of groundwater samples in the area (0.05 to 0.50 mg L-1), indicating the concentration of hydrocarbon could be estimated by mineral constitutions of groundwater, which was related to the concentration of Ca2+ and Mg2+. Based on the methods and theories in this study, the concentration of original hydrocarbon in shallow groundwater could be estimated and help to understand the mechanism of water-rock interaction in shallow aquifer and original high hydrocarbon groundwater strategic assessment.

Investigation into Groundwater Resources in Southern Part of the Red River’s Delta Plain, Vietnam by the Use of Isotopic Techniques

Groundwater in the Red River’s delta plain, North Vietnam, was found in Holocene, Pleistocene, Neogene and Triassic aquifers in fresh, brackish and saline types with a total dissolved solids (TDS) content ranging from less than 1 g L−1 to higher than 3 g L−1. Saline water exists inHolocene aquifer, but fresh and brackish water exist in Pleistocene, Neogene and Triassic aquifers. This study aims at the investigation into genesis and processes controlling quality of water resources in the region. For this isotopic, combined with geochemical techniques were applied. The techniques include: (i) measurement of water’s isotopic compositions (δ2H, δ18O) in water; (ii) determination of water’s age by the 3H- and 14C-dating method, and (iii) chemical analyses for main cations and anions in water. Results obtained revealed that saline water in Holocene aquifer was affected by seawater intrusion, fresh water in deeper aquifers originated from meteoric water but with old ages, up to 10,000–14,000 yr. The recharge area of fresh water is from the northwest highland at an altitude of 140–160m above sea level. The recharge water flows northwesterly towards southeasterly to the seacoast at a rate of 2.5m y−1. Chemistry of water resources in the study region is controlled by ferric, sulfate and nitrate reduction with organic matters as well as dissolution of inorganic carbonate minerals present in the sediment deposits. Results of isotopic signatures in water from Neogene, Triassic and Pleistocene aquifers suggested the three aquifers are connected to each other due to the existence of faults and fissures in Mesozoic basement across the delta region in combination with high rate of groundwater mining. Moreover, the high rate of freshwater abstraction from Pleistocene aquifer currently causes sea water to flow backwards to production well field located in the center of the region.

A combined methodology for estimating the potential natural aquifer recharge in an arid environment

ABSTRACT An innovative methodology that combines an indirect physiography-based method for determining the runoff coefficient at a sub-basin scale and a water balance model applied on a daily time scale was developed to calculate the natural groundwater recharge in three watersheds within the Oum Zessar arid area, Tunisia. The effective infiltration was calculated as part of the water surplus by considering the average available water content (AWC) of soil and an average runoff coefficient for each sub-basin. The model indicates that the sub-basins covered mainly by the “artificial” soils of tabias and jessour, characterized by average AWC values greater than 150 mm, did not contribute to natural groundwater recharge over the 10-year period (2003–2012) considered. The estimated volume for the Triassic aquifer amounted to about 4.5 hm3 year−1, which is consistent with previous studies. For the Jurassic and Cretaceous aquifers, the estimated volumes amounted to about 200 dm3 year−1.

Microbial Communities of Low Temperature, Saline Groundwater Used for Therapeutical Purposes in North Poland

Knowledge on microbial community composition and ecology in highly mineralized (TDS up to 71 g l−1), cold waters (T < 12 °C) from the zones of restricted water exchange is scarce. Therefore, the aim of our study was to reveal how the particular physicochemical water conditions of these zones affect the community composition. The community members, which could be involved in the sulfur cycling were of particular interest since they may strongly influence wells operation. The pristine, mineral waters of North Poland were extracted from boreholes reaching Cenozoic, Jurassic, and Triassic aquifers at the depth of 46–1248 m below ground surface. Both culture-dependent (culturing on R2A medium) and culture-independent techniques (microscopic methods and high-throughput 16S rDNA amplicon sequencing) were applied. The bacterial communities were characterized by low complexity and strongly varied across the sampling locations. Bacteria potentially involved in the sulfur cycle (sulfate reduction) were common in all mineral waters and were dominant (especially Desulfovibrio) in the deepest waters. The most important geochemical drivers of the observed microbial community composition were TDS including Cl−, Na+, Mg2+, and NO3−. Bacterial isolates belonged mostly to the genus Bacillus. Sequences assigned to Archaea (Methanobacterium) were detected only in the deepest borehole water.

Water quality assessment of the Triassic aquifer, SE Tunisia, for drinking water supply

The Triassic aquifer is located in southereastern Tunisia, in the Medenine region, and being part of Jeffara's multilayer aquifer system. The aquifer is currently overexploited with an exploitation rate of 163%, which led to a generalized drop in the piezometric level in the order of 20 cm/year. This study applied conventional techniques such as hydrochemical compositions, multivariate statistical methods and Geographical Information Systems (GIS). To better identify the processes controlling the hydrogeochemical evolution of groundwater quality of Triassic aquifer and its suitability for drinking uses, 14 well water samples from the Triassic aquifer were analysed for physical character and chemical composition. In the groundwater, the respective order of cation and anion concentration was Na&gt;Ca&gt;Mg&gt;K and SO4&gt;Cl&gt;HCO3. The chemical data of water samples from the study area presented by plotting on a Piper diagram reveals the predominance of two hydrochemical types: a Na-Ca-Mg-SO4 facies and a Na-Ca-Mg-Cl-SO4 facies. Analytical results demonstrate that the chemical composition of groundwater in Triassic aquifer is strongly influenced by residence time and flow path. Water quality deteriorates going from southwest to northeast across the region, coincident with the appearance a clay layer limiting the infiltration of rainwater. The majority of ions are above the maximum desirable limits recommended for drinking water by WHO guidelines and Tunisian Standards (NT.09.14). Based on the Water Quality Index (WQI), 36% of water samples of the Triassic aquifer are classified as "poor water" and they cannot be used for drinking purposes without prior treatment.

Hydro-geochemical characteristics of the groundwater resources in the southern part of the Red River’s Delta plain, Vietnam

In this study, the origin and recharge areas as well as the chemistry of the groundwater in the southern part of the Red River Delta plain, in Thai Binh, Nam Dinh and Ninh Binh provinces (North Vietnam) was investigated by using isotopic techniques combined with geochemical analysis. Groundwaters under the study were those that are available in the Holocene, Pleistocene, Neogene and Triassic aquifers. Groundwater in the Holocene aquifer is brackish of Na–Cl type with an electric conductivity as high as up to 6000 µS cm−1. The water in the shallow aquifer comprises three end-members: the local precipitation, Red River’s water and intruded seawater. Groundwater in the Pleistocene, Neogene and Triassic aquifers in the Southwest of the study region is fresh containing less than 1 g L−1 of total dissolved solids and is characterized by the Ca–Na–HCO3 type. However, groundwater in the deep aquifers in the Northeast area is brackish of Na–Ca–Cl–HCO3 ion type containing more than 1 g L−1 TDS. The chemistry of groundwater in the study region is controlled by three processes, namely the incongruent dissolution of the biogenic high Mg-calcite, the reduction of sulphate and iron oxyhydroxide with organic matters present in the aquifers. The salinity in deep aquifers in the NE was attributed to the diffusion of saline pore water from aquifer or/and aquitard deposits to the recharge water. Groundwater in the Pleistocene, Neogene and Triassic aquifers in the study region seem to have meteoric origin with long traveling time and it mixed with the saline pore water that migrated from the aquifers sediments, as it was evident from the water isotopic compositions. The isotopic compositions of water (δ2H and δ18O) in the Neogene and Triassic aquifers are similar to that found in the Pleistocene aquifer suggesting the aquifers are hydraulically connected to each other due to the over-extraction rate of fresh water from the latter aquifer. Recharge area of groundwater in the Pleistocene and Neogene aquifers is suggested to be from the NW extension of the region and out crops at a highland at an altitude of 140–160-m above sea level (masl). The recharge water flows from northwesterly towards southeasterly to the sea coast. The results of the 14C-dating for groundwater combined with the hydraulic heads distribution in the deep aquifers revealed that the saline groundwater is flowing from the NE and backwards from the sea side to the production well field in the center of the region due to the high rate of groundwater mining. In order to mitigate the saltwater intrusion and avoid deterioration of the quality of the groundwater that is currently being mined and supplied to the local population, it needs to develop and implement an appropriate strategy for the groundwater resource management in the region.

Wykorzystanie modelowania geochemicznego oraz badañ izotopowych siarczanów do identyfikacji procesów kształtujących skład chemiczny wód podziemnych ujęcia Gliwice-Łabędy

Application of sulfate isotope studies and geochemical modeling in determining processes affecting groundwater chemistry in the Gliwice-£abedy well-field area. A b s t r a c t. In order to determine geochemical processes affecting chemical composition of groundwater in the Gliwice-Łabedy well-field area two research methods were applied. Chemical analysis allowed us to assess the quality of groundwater in the Triassic karst-fractured-porous aquifer of the southwestern part of the major groundwater basin no. 330. The chemical composition of groundwater is distinguished by spatial heterogeneity highlighted by higher mineralization and concentrations of individual ions in the western area. In addition, all samples collected in 2016 were analyzed for the 34 S and 18 O to identify sources of sulfates in the waters examined. The study revealed a different origin of these ions depending on location of the wells sampled. The results of chemical analysis and archival data allowed for application of geochemical modeling in identification of processes taking part in groundwater chemistry evolution. Simulations of processes controlling water chemistry within the Triassic aquifer were conducted using The Geochemist’s Workbench 10.0.6. The examined processes encompassed dissolution of minerals forming the carbonate aquifer and Miocene evaporates overlying the Triassic aquifer as well as mixing of groundwater and surface water.

A multi-method approach to groundwater risk assessment: a case study of a landfill in southern Poland

Estimating groundwater vulnerability to pollution is based on the quantitative and qualitative assessment of the degree of exposure to the pollution. This article attempts to assess groundwater vulnerability to pollution in the area of a complex of landfill sites located in the supply area of one of the important groundwater reservoirs in southern Poland. Two dynamic leaching tests and two static tests were carried out on two different samples of slag from one of the metallurgical landfills during various periods of storage (15 year old waste and freshly deposited waste). Transport equations were based on the data from a column experiment. The advection-dispersion equation for column leaching was employed, which confirmed the simulation parameters through experimentation. The results of the leaching tests on chlorides showed that they are leached from the landfill over a period of ~60–90 years from the moment of depositing the waste. The seepage time for the Quaternary aquifer is 1–7 years and, for the Triassic aquifer, 5–40 years. The Backman’s contamination index (1998) values exceeded 25, while a high threat to groundwater is observed when the contamination index value equals 3. The use of all the aforementioned methods determined the most vulnerable area.

Basin‐scale thermal and fluid flow histories revealed by carbonate clumped isotopes (Δ47) – Middle Jurassic carbonates of the Paris Basin depocentre

AbstractThe reconstruction of past diagenetic conditions in sedimentary basins is often under‐constrained. This results from both the analytical challenge of performing the required analyses on the minute sample amounts available from diagenetic mineral phases and the lack of tracers for some of the diagenetic parameters. The carbonate clumped isotope thermometry (Δ47) opens new perspectives for unravelling the temperatures of diagenetic phases together with the source of their parent fluids, two parameters that are otherwise impossible to constrain in the absence of exploitable fluid inclusions. Here is reported the study of a large number of sedimentary and diagenetic carbonate phases (from Middle Jurassic reservoirs of the Paris Basin depocentre) by combining detailed petrographic observations with a large number of Δ47 data (n &gt; 45) on a well‐documented paragenetic sequence, including calcite and dolomite burial cements. The data reveal carbonate crystallization at temperatures between 29°C and 98°C from fluids with δ18Owater values between −7‰ and +2‰, in response to the progressive burial and uplift of the Paris Basin, throughout 165 Myr of basin evolution. Coupled with the time–temperature evolution previously estimated from thermal maturity modelling, these temperatures allow determining the timing of four successive cementation episodes. The overall data set indicates a history of complex water mixing with a significant contribution of hypersaline waters from the Triassic aquifers migrated upward along faults during the Cretaceous subsidence of the basin. Subsequent large‐scale infiltrations of meteoric waters induced a dilution of these pre‐existing brines in response to the Paris Basin uplift in the Tertiary. Overall, the data presented here allow proposing an integrated approach to characterize the cementation events affecting the studied carbonate reservoir units, based on temperature, oxygen isotope composition and salinity of the parent fluids as well as on petrographic grounds.