Dissolution Of Silicate Minerals Research Articles

Geochemical characteristics, mechanisms, and suitability of groundwater resource for sustainable water supply in Quetta valley

ABSTRACT Groundwater is a crucial water resource for various usages worldwide. The Quetta Valley of Pakistan was investigated regarding its groundwater quality sustainability based on integrated approaches of hydrochemistry, geographic information system, and multivariate statistics. A total of 29 groundwater samples were collected from monitoring wells to get insights into the hydrochemical suitability of groundwater for sustainable irrigation and drinking utilization. The results indicate groundwater is mainly featured by the hydrochemical facies of HCO3·Cl-Ca. Groundwater hydrochemical composition is dominantly governed by the dissolution of carbonates and silicate minerals in combination with positive cation exchange in the valley. Principal component analysis reveals a significant influence of geogenic factors on groundwater chemistry, further supported by PHREEQC simulation that detects a supersaturation of calcite, dolomite, and sulphate minerals in the aquifer. The irrigation water quality index divides groundwater in the study area into three zones, which signify low restriction and no restriction, except for a severe restriction in the southwestern part of the valley. Groundwater is generally suitable for irrigation across the valley. The entropy-weighted water quality index classifies groundwater as excellent and good quality for drinking. This study can provide crucial insights for authorities on groundwater suitability in Quetta Valley and similar regions worldwide.

Geochemistry and sources of boron and strontium of geothermal waters from the Pearl River Delta region, South China: Implications for water-rock interactions

Pearl River Delta (PRD) region of South China is abundant of geothermal water resources. However, the development and utilization level of geothermal resources in this region is relatively low, due in part to the lack of fundamental geochemical research. To access water-rock interaction processes of the PRD geothermal system, we analyzed the geochemistry of geothermal waters by combining trace elements (B, Sr, and Br) and isotopes (δ11B and 87Sr/86Sr) with conventional tracers (major elements) that had been reported. The Cl/Br ratios (from 31 to 639) confirm the multi-source salinity of marine origin, precipitation, and a minor dissolution of halite. Major ions chemistry highlights the influence of ions exchange, the dissolution of carbonate, silicate, and sulphate minerals as well as the contribution of seawater. The Cl/B ratios (61 to 22,583) suggest interactions with carbonate rock and felsic rock, input of seawater, and groundwater mixing. Boron isotopic compositions (δ11B) range between −9.22 and +39.78 ‰. Sr contents and 87Sr/86Sr ratios are more homogeneous, falling between 0.06 and 32.26 mg/L and between 0.71239 and 0.72121, respectively. The B and Sr isotopic signatures show that three processes contribute to geochemistry of geothermal waters: 1) water/rock interaction involving marine carbonate rock, evaporite, and granitoid or/and gneiss, 2) seawater intrusion, and 3) shallow groundwater mixing. Major-trace element chemistry and these isotope systematics on their own indicates essential information on the aspects of fluid origin or water-rock interaction processes, and however provide a more comprehensive understanding of the geothermal system in the PRD region, South China.

Genetic mechanism of geothermal water in the sandstone reservoir of western Sichuan, SW China: Evidence from hydrochemistry and δD − δ18O isotopes

Geothermal energy is the vital clean and renewable energy in the world. In China, most of high−temperature sedimentary − type geothermal waters are developed in western Sichuan, such as geothermal springs in the Litang county. In this study, hydrochemistry and δD − δ18O isotopes were investigated to clarify the genetic mechanism of high−temperature sedimentary − type geothermal waters in the Litang county. The self-organized map and Piper diagram showed three hydrochemical types of geothermal waters: (1) HCO3 − SO4 − Na, (2) HCO3 − Na with low Cl− concentration, (3) HCO3 − Na with high Cl− concentration. Cluster 1 geothermal water of Na − HCO3 − SO4 was dominated by dissolution of silicate and sulfate minerals. Cluster 2 geothermal water of HCO3 − Na with low Cl− concentration was affected by dissolution of silicate and CO2 degassing and mixed by large amounts of shallow cold water. Cluster 3 geothermal water of HCO3 − Na with high Cl− concentration was affected by dissolution of sandstone silicate and CO2 degassing and mixed by less shallow cold water. The recharge elevation of geothermal water in Litang ranges from 4799 to 4972 m, with an average of 4915 m. This suggests that the recharge sources of geothermal water are snow melt water and magmatic water. Cluster 3 geothermal water displayed the largest contribution of magmatic water. The temperature of HCO3 − SO4 − Na geothermal water after mixing is 92−102 °C, with an average of 97 °C; the initial temperature of HCO3 − Na with low Cl− geothermal water is 60−72 °C, with an average of 65 °C; the initial temperature of HCO3 − Na with high Cl− geothermal water is 74−91 °C, with an average of 81 °C. The temperature of geothermal water after mixing is Class 1 > Class 3 > Class 2. From the perspective of reservoir temperature, the Class 3 of geothermal water had the highest values, followed by Class 1 and Class 2 of geothermal water. From the perspective of cold − water mixing ratio, Class 2 and Class 3 of geothermal water had a similar mixing ratio, slightly higher than that of Class 1 of geothermal water. Therefore, the class 3 geothermal water with HCO3 − Na with high Cl− concentration possess the great potential for exploitation.

Constructing a map of potassium inputs to paddy fields from irrigation

Geographical and geological parameters, including land use, lithology, and water quality, and volume of irrigation were investigated to map K inputs into paddy fields from irrigation in the eastern part of Fukushima, Japan. This area has had one of the greatest needs for K maintenance worldwide due to the control of radiocesium uptake by plants after the Fukushima nuclear accident in 2011. The K+ concentration in irrigation water and its sources was in the range of 0.2–5.2 mg L−1, which was probably affected by both the natural conditions (e.g., amount of silicate mineral dissolution and presence of hot springs and coal seams) and human activities (e.g., agriculture and urbanization). Irrigation volume was estimated to range from 306 to 2300 mm in response to daily water requirement rates. K inputs were computed by multiplying the concentrations and volumes, giving estimated inputs of 2.5–133 kg K2O ha−1 crop−1. The inputs proved spatially variable and were high in the western and southeastern parts of the study area. Irrigation was estimated to supply more than half of the K application rate in the rice cultivation guidelines to 12% of the paddy field area. This map should provide useful information for devising K maintenance plans.

Hydrochemical Characteristics, Controlling Factors and Strontium Enrichment Sources of Groundwater in the Northwest Plain of Shandong Province, China

To elucidate the hydrochemical characteristics, controlling factors, sources and mechanisms of strontium ion enrichment in groundwater in the northwest plain of Shandong Province, China, 88 groundwater samples were collected, including 51 shallow pore groundwater samples, 29 deep pore groundwater samples and 8 karst groundwater samples. The hydrochemical characteristics of the different types of groundwater were quite different. The karst groundwater samples were all fresh water with a single hydrochemical type, either HCO3-Ca or HCO3-Ca·Mg. The deep pore groundwater samples were mainly brackish water, and the shallow pore groundwater samples were brackish water–salt water, which has complex hydrochemical types. The hydrochemical characteristics of all the types of groundwater were controlled by mineral dissolution and active positive cation exchange. In shallow pore groundwater, deep pore groundwater and karst groundwater, the dissolution of silicate, evaporite and carbonate minerals dominated the hydrogeochemical process. The strontium in groundwater was derived from the dissolution of minerals with strontium isomorphism. The average contents of strontium in shallow, deep and karst groundwater were 1.59 mg/L, 0.58 mg/L and 0.50 mg/L, respectively. The strontium in shallow pore groundwater was mainly derived from the enrichment of groundwater runoff, and its sources are abundant, with silicic rock being the main source. The deep pore groundwater mainly derived from the evaporative minerals containing strontium, and the karst water mainly derived from carbonate rock dissolution with similar characteristics.

Characteristics of congruent dissolution of silicate minerals enhanced by chelating ligand under ambient conditions

Characteristics of congruent dissolution of silicate minerals enhanced by chelating ligand under ambient conditions

Soil Inorganic Carbon Formation and the Sequestration of Secondary Carbonates in Global Carbon Pools: A Review

Soil inorganic carbon (SIC), a potential carbon sink especially in arid and semi-arid environments, contributes to soil development, landscape stability, carbon (C) sequestration, and global C dynamics but due to the lack of SIC scientific reporting in most C sequestration research, its importance is unclear. A detailed overview of primary and secondary carbonate occurrence, formation, and importance is much needed to understand the role of pedogenic (PC)/secondary carbonate (a common biogeochemically derived soil mineral over time) in the SIC. The mechanisms involved in the formation of PC including carbon dioxide (CO2) from microbial respiration and precipitation, silicate mineral weathering, dissolution, and reprecipitation are highlighted. The isotopic composition of carbonates related to biological C3 or C4 carbon fixation pathways and other paleoecologic and/or climactic factors responsible for new soil carbonate formation are discussed in detail. To address the lack of knowledge associated with SIC, this review attempts to highlight the currently known aspects of the literature, and briefly describe the formation and methodologies that can aid in addressing the research gaps surrounding SIC sequestration. The authors also suggest that greater focus needs to be provided on the actual measurement of SIC to develop a more comprehensive SIC inventory to provide sound data for future research direction, and modeling efforts and to predict C terrestrial storage and change efficiently.

A combination of multivariate statistics and machine learning techniques in groundwater characterization and quality forecasting

Globally, the quality of groundwater has proven to have been affected by some natural and human activities in recent years. To ensure there is good drinking water (Sustainable Development Goal 6.3, there is a need to elucidate the groundwater quality status of the area of interest. The groundwater in the northwestern parts of Ghana is not yet well characterized. Hence, this study employed a multi-method approach of hydrochemistry, water quality index (WQI), multivariate statistics, and machine models: multiple linear regression (MLR), decision tree regression (DTR), random forest regression (RFR), and artificial neural network (ANN), are combined in the characterization and prediction of the water quality in the area. They are robust in providing conclusions on groundwater assessment that can be relied upon for decision-making processes regarding groundwater usage and monitoring. Except for NO3− and TDS exceeding their standard levels in 22 and 2 locations, respectively, the other physicochemical parameters are within acceptable limits. The groundwater is generally good for domestic usage based on the WQI, with 79.2% of excellent to good waters. The groundwater evolved from Na-type, Cl-type, and Cl(SO4)-Ca(Mg) facies. Agricultural activities are the main source of human impact on the groundwater. Silicate mineral dissolution and ion exchange processes are the natural processes that affect groundwater mineralization, with mineral dissolution being the dominant process. Based on the performance metrics: MAE, MSE and RMSE of the ML methods considered in the WQI forecasting, the order of performance of the models is ANN > RFR > DTR > MLR, with the following respective R2 values 0.9974, 0.9193, 0.8966 and 0.8886.

Muddy sediments are an important potential source of silicon in coastal and continental margin zones

The dissolution of silicate minerals on the seafloor releases an important amount of dissolved silicon (dSi), which is necessary for maintaining high diatom production in Coastal and Continental Margin Zones (CCMZs). However, the dissolution of silicate minerals along the continental shelves is variable, which hinders our understanding of the marine Si cycle on both a regional and global scale. To understand the discrepancy of silicon (Si) released in different sediment matrices and its potential controlling factors, we investigated surface sediments of typical CCMZs of the Chinese marginal Seas using a continuous alkaline extraction technique, grain size and chemical (carbon and total nitrogen) analysis as well as a qualitative measurement of clay mineral composition by X-ray diffraction. The results showed that the amount of Si and aluminum (Al) leached from muddy sediments were 2 times greater than those released from sandy sediments. High dissolution rates (> 0.20 mg-SiO2 g−1 min−1) of silicate minerals are caused by a large sediment-specific surface area. Further, our data showed that biogenic silica (bSi) with high Al content (Si:Al < 40) has low reactivity and that the source of Al incorporated in bSi is silicate minerals undergoing dissolution. We show that although the dissolution of silicate minerals is less active than that of bSi, it still potentially releases more bio-available Si and Al to seawater due to its dominant presence on the seafloor (70.3% − 99.0%wt). This study highlights silicate minerals as an important potential marine Si source and emphasizes the need for a better understanding of the roles of silicate minerals in the Si cycle of marginal seas in future studies.

Hydrogeochemical and geothermal features of thermal springs along the Ganzi-Yushu fault, eastern Tibetan Plateau and its geological implications

Important fault zone processes can be discerned from the hydrothermal fluid circulation associated with active seismic sources. This study focused on the geochemical and isotopic features of the thermal waters along the Ganzi-Yushu fault (GZYSF) located in the eastern Tibetan Plateau. 22 spring samples were collected to characterize the chemical compositions and calculate the geothermal reservoir temperatures. The hydrothermal waters are mainly recharged by meteoric water based on the δ18O and δ2H values. Immature waters with a Na + -HCO3- or Ca2+(Mg2+)-HCO3- composition were recognized in the study area, combined with the poor correlation between K+, Na+, Mg2+, HCO3− and Cl− suggesting a shallow hydrothermal fluid source. The 87Sr/86Sr ratios and high concentrations of B (from 20.3 to 9445 μg/L) and Li (from 3.04 to 2380 μg/L) show a dissolution of silicate minerals containing calcium and magnesium during fluid circulation. The geothermometry in the silicon-enthalpy system suggested equilibrium temperatures up to 146 °C, whereas most are low temperatures. The shallow geothermal fields along GZYSF show that most large earthquakes (M＞5) were distributed in the transitional zone between high-value area and low-value area of the shallow geothermal field, suggesting a potential genetic link between geothermal field structure and earthquake nucleation along active faults. In conclusion, we proposed a conceptual model to portray the fluid circulation process. Such work can provide insights into the potential geothermal resource in Tibetan Plateau, and also investigate the processes controlling the fluid chemistry and the correlation with occurrence of earthquakes in the region.

Geochemical Evidence Constraining Genesis and Mineral Scaling of the Yangbajing Geothermal Field, Southwestern China

The Yangbajing geothermal field, a renowned high-temperature geothermal resource in Tibet of southwestern China, has been utilized for power generation for several decades. To improve geothermal exploitation in the Yangbajing, genesis and mineral scaling have yet to be further revealed. In this study, hydrochemistry and D-O-Sr isotopy were employed for analyzing genesis and mineral scaling in the Yangbajing geothermal field. The geothermal waters were weakly alkaline and had a high TDS content (1400–2900 mg/L) with the Cl-Na, Cl·HCO3-Na, and HCO3·Cl-Na types. The dissolution of silicate minerals (sodium and potassium feldspars) and positive cation exchange controlled the hydrogeochemical process. The geothermal water was recharged from snow-melted water and meteoric water originating from the Nyainqentanglh Mountains and Tangshan Mountains. The geothermal waters possessed the highest reservoir temperature of 299 °C and the largest circulation depth of 2010 m according to various geothermometers. The geothermal waters can produce CaCO3 and SiO2 scaling during vertical and horizontal transport. These achievements can provide a scientific basis for the sustainable development and conservation of the high-temperature geothermal resources in Yangbajing and elsewhere.

A study on the geothermal circulation system of granite: An example from the Lancang area, Yunnan

This study assesses the geothermal water circulation process of a granite geothermal system in the Lancang area, Yunnan. Cycling processes are studied using water chemistry and isotope analysis techniques. The results show that the water chemistry type of the hot springs in Lancang is Na-HCO3, with TDS values ranging from 246 to 724 mg/l. The granite pluton, as the main heat source, has a high radiogenic heat generation rate (4.17 μW/m3 on average). δD and δ18O in Lancang are close to the global atmospheric and local precipitation lines, indicating that geothermal water originates from atmospheric precipitation. Moreover, the mountainous area from 1295.3 to 1624.5 m above sea level is the main precipitation recharge area. In addition, the main ions of geothermal water mainly come from the dissolution, weathering, and cation exchange of silicate minerals in granite, and Ca2+ and Mg2+ in the water are exchanged with Na+ and K+ in the reservoir, significantly increasing the Na+ and K+ concentrations in the water. The reservoir temperatures are 126.60 °C to 151.32 °C based on the SiO2 geothermometer, and the depths range from 2283.05 to 4024.59 m. The NW- and NE-oriented fault system in Lancang serves as a channel for geothermal water to exit the ground and form hot springs; this water is also mixed with cold water during upwelling, and the mixing ratios are 63 %-84 %. Finally, the model of geothermal water circulation in the Lancang is established.

Lithium extraction from typical lithium silicate ores by two bacteria with different metabolic characteristics: Experiments, mechanism and significance

Microorganisms obtain inorganic nutrients or energy from specific minerals to selectively weather minerals, but few studies on the differences in metabolic components of different functional bacteria lead to different weathering effects. This study evaluated the leaching effects of two bacteria with distinct metabolic characteristics on lithium silicate minerals with different structures. We aimed to understand the microscopic mechanism of crystal destruction of lithium silicate minerals with different structures under the action of microorganisms. The results showed that the metabolites produced by an acid producing silicate strain Raoultella sp. Z107 (strain Z107) had a high content of organic acids, among which lactic acid was up to about 11 g/L. Bacillus mucilaginosus 21,699 (strain BM) secreted capsular polysaccharide with a high content of 14.84 mg/L. The metabolic activities of the two strains were significantly different. Through the analysis of the leaching residue, it was found that the lithium silicate minerals were acid etched, interlayer domains expanded, crystallinity decreased, and metal bonds were broken under the action of bacteria. The dissolution of lithium silicate minerals by bacteria is a combination of bacterial adsorption, organic acid corrosion, and complexation of small molecular organic acids and macromolecular polymers with metal ions. The acid erosion and complexation effects of organic acids are greater than the single complexation of capsular polysaccharides, and the layered lepidolite is more likely to be decomposed by the weathering of bacterial metabolites than the chain structure spodumene. These results indicate that the diversity of metabolic activity of bacteria from different sources and the sequence and decomposition mechanism of metal ions released from minerals after lattice destruction are also different. Microorganisms decompose minerals for energy and nutrients, and eventually become the main players in the transformation of elements in biogeology.

Chemical Alteration of Riverine Particles in Seawater and Marine Sediments: Effects on Seawater Composition and Atmospheric CO2

Numerous studies have shown that riverine particles react with seawater. Reactions include dissolution of reactive silicate minerals (e.g., feldspars) and formation of authigenic clays and carbonates. Previous studies have either focused on mineral dissolution (marine silicate weathering) or authigenic phase formation (reverse weathering). A comprehensive study that assesses all processes affecting the marine alteration of riverine particle has -to our knowledge- not yet been conducted. Our contribution aims to fill this gap. We first quantify cation exchange between seawater and riverine particles that occurs when particles enter the marine realm and show that significant global cation fluxes are induced by this process (-1.3 Tmol Na yr-1, -0.2 Tmol K yr-1, -0.4 Tmol Mg yr-1, +1.2 Tmol Ca yr-1) where the positive sign indicates cation release into seawater while the negative sign denotes uptake on particles. We then use thermodynamic and kinetic modeling to investigate how much of the suspended particle load dissolves in contact with seawater and estimate corresponding global release rates for dissolved cations and silica assuming congruent dissolution (+0.06 Tmol Na yr-1, +0.15 Tmol Ca yr-1, +2.8 Tmol Si yr-1). Subsequently, we investigate rates of mineral dissolution and authigenic clay and carbonate formation in marine sediments applying reactive transport modeling, porewater data and mass balance calculations. Our best estimates for net fluxes across the sediment/water interface (dissolution–mineral formation) result as +1.5 Tmol Na yr-1, -2.5 Tmol K yr-1, -2.0 Tmol Mg yr-1, +2.5 Tmol Ca yr-1, and +1.9 Tmol Si yr-1 where most of the Na and Ca release is induced by plagioclase dissolution, K is taken up in authigenic clays and Mg is removed from solution by authigenic clay and carbonate formation. We conclude that the alkalinity of seawater is not significantly affected by marine silicate alteration since cation release fluxes (Na, Ca) are as high as cation uptake fluxes (K, Mg) on equivalent basis. Moreover, marine silicate weathering and reverse weathering are closely coupled since Al required for clay formation is mostly provided by feldspar dissolution while Al removal in authigenic clay promotes and maintains feldspar dissolution in marine sediments. Authigenic carbonate formation in anoxic subsurface sediments sequesters significant amounts of carbon (2.5 Tmol C yr-1) according to our estimates where most of the Ca and alkalinity required for carbonate formation are provided by the dissolution of Ca-bearing silicate minerals. This hidden sedimentary cycle provides a sink for dissolved inorganic carbon that may drive a slow draw-down of atmospheric CO2 on geological timescales. Marine silicate alteration has an even stronger effect on the geochemical evolution of seawater by generating large fluxes of dissolved K, Mg, Ca and Si.

Appraisal of rock–water interaction and frailty of groundwater to corrosion and salinization, northwestern Gulf of Suez, Egypt

AbstractFrom 12 groundwater samples taken in Egypt's northwestern Suez Gulf, it can be concluded that the water is not suitable for drinking or irrigation purposes. The water is highly mineralized, has extreme hardness, and is very saline, with salinity levels above 3000 ppm. The dominant ions in the water samples are Cl, Na, SO4, and HCO3, and there are two distinct water types: SO4. Ca–Cl (90%), and SO4. Na-Cl (10%). The research also revealed that three wells had become salinized due to dominant ions from sewage water recharge and seawater invasion. The water samples were found to be oversaturated with carbonate, silicate, iron oxide, and evaporite mineral dissolution, which could be harmful to human health. The water was found to exhibit ion exchange, where alkaline earth's (Ca + Mg) ions associated with solids and alkalis' ions (Na + K) in water samples exchange ions. The water was also found to have a high propensity for corrosion, making it unsafe to move groundwater over long distances. The excessive salinity of the water in the research area also makes it undesirable for drinking and irrigation purposes. Overall, the research findings suggest that measures need to be taken to ensure the safety of the groundwater in the area and prevent further contamination. The findings also highlight the importance of regular monitoring and testing of groundwater to ensure that it meets safe levels for human consumption and agricultural use.

Characterizing the water–rock interactions and groundwater flow processes in the Paleozoic to Cenozoic strata aquifer systems with contrasting mineralogy at basin scale: Qingyi river, east China

This study aims to identify water–rock interaction and groundwater flow processes in aquifer systems with contrasting mineralogy at the basin scale. Investigations have been carried out using major ion geochemistry and environmental isotopes (δ2H and δ18O of water, δ13C values, 87Sr/86Sr ratios, and 14C activities) within aquifers with contrasting mineralogy in the Qingyi river basin (QRB, east China) composed of marine carbonate and continental granitic sediments with successive strata during Paleozoic, Mesozoic and Cenozoic. Analysis of 95 rain, surface and groundwater, and 12 solid rock samples found that dissolution of limestone, silicate minerals, and evapotranspiration dominated the hydrogeochemical process in the lower, upper, and middle basin, respectively. The various major ion and 87Sr/86Sr ratios of groundwater in each aquifer suggest that local lithology minerals dissolution controls the water–rock equilibria in the groundwater system. The 87Sr/86Sr ratios are correlated with both major ion geochemistry and δ13C values, constraining the process of varying proportions of silicate and carbonate minerals dissolution. Percolating water from soils carrying dissolved CO2 plays an important role in controlling the hydrogeochemical processes in the groundwater system throughout the QRB. Inter-aquifer flow has been proved by the well correlated relations between 87Sr/86Sr ratios and δ13C values or/and Sr/Na and Ca/Na ratios, as well as the irregular groundwater apparent 14C ages (1.78 to 8.52 kyr) with respect to position in the basin. Admixture ratios of 9–50% are derived from the groundwater in limestone aquifer. The rapid decrease in carbonate groundwater mixing ratio is accompanied by an increase in 87Sr/86Sr ratios, indicating that groundwater is derived Sr from silicate weathering and abundant carbon from the soils. Regional inter-aquifer flow occurs in the buried carbonate aquifers based on isotopic evidence, which could result in karstic groundwater leakage in the Wuhu cityside and should be given special attention.

Groundwater–Surface Water Exchange and Spatial Distribution of Arsenic in Arid and Semi-Arid Regions: The Case of Aksu River in Xinjiang, Northwestern China

The Aksu River, a quintessential inland river, exhibits elevated arsenic (As) concentrations in certain sections of its natural waters. Further investigation is necessary to determine the role of surface water and groundwater (SW-GW) exchanges in contributing to these high As concentrations. Both surface water and groundwater constitute crucial components of the basin water cycle, and the interaction between the two has been a central focus in basin water cycle research. In this study, a total of 59 groundwater samples and 41 surface water samples were collected along the river’s course within the basin. Among the groundwater samples, 18.64% exceeded the permissible drinking limit for As concentrations (10 μg/L), while 39.02% of the surface water samples exceeded this threshold. The water bodies in the Aksu River Basin are mildly alkaline, with total dissolved solids (TDSs) in surface water significantly surpassing those in groundwater. The chemical compositions of surface water and groundwater are strikingly similar, with the predominant anions being chloride (Cl−) and sulfate (SO42−) and the principal cations being sodium (Na+). The dissolution of silicate and carbonate minerals primarily influences the water chemistry characteristics of surface water and groundwater in the Aksu River Basin, followed by the dissolution of salt rocks. Human activities also play a major role in affecting the river’s water quality. The distribution of groundwater with elevated As content is entirely encompassed within the spatial distribution of surface water. Groundwater–surface water exchange plays a vital role in As enrichment in surface water.

Evaluation of Groundwater Quality for Drinking and Irrigation Purposes Using GIS-Based IWQI, EWQI and HHR Model

Groundwater pollution has emerged as a significant water crisis in various regions around the globe. Groundwater serves as a crucial source of water for human consumption and agricultural activities in the Sichuan Basin where groundwater quality has yet to be concentrated. A total of 41 groundwater samples were collected from domestic wells in Suining city of the Sichuan Basin, which were used for analyzing the hydrogeochemical processes and suitability for irrigation and drinking purposes. In the study area, groundwater samples belonged to the HCO3-Ca type. Hydrochemical compositions were dominated by carbonate and silicate mineral dissolution with positive cation exchange. Agricultural activities and urban sewage were the primary sources of NO3− pollution. The irrigation water quality index (IWQI) was calculated using electronic conductivity (EC), Na+, Cl−, HCO3−, and sodium adsorption ratio (SAR). The IWQI values showed that the suitability of groundwater irrigation was generally good and presented the decreasing trend southeastwardly. According to the entropy-weighted water quality index (EWQI), the groundwater quality for drinking purposes was generally good. However, there were some local areas with poor water quality concentrated in the southeast part. According to the human health risk (HHR) model, the groundwater was deemed safe for adults and children. However, for infants, the nitrate level in the groundwater remained high and posed potential health risks. The combined IWQI and EWQI evaluation served as a valuable reference for the utilization of the groundwater resource in the Sichuan Basin, as well as other comparable regions worldwide.

The characteristics and origin of chlorite coats in the Oligocene gas sandstone reservoirs of the Upper Huagang Formation, Xihu Depression, East China Sea Shelf Basin

Clay coats are widespread in the Oligocene braided river channel sandstones in the Xihu Depression on the East China Sea Shelf Basin. High clay coat coverage in braided channel sandstones is typically associated with good reservoir quality. The morphology, origin and distribution of clay coats and their effect on reservoir quality in different braided channel facies are investigated by core description, core analysis and a series of petrographic techniques. The present clay coats consist of two parts, the inner and outer coats. The inner coats are mainly composed of illite and chlorite components. The inner illite coats are transformed from smectitic clay precursors, while the inner chlorite coats may originate from thermally driven recrystallization of Fe-rich clay precursors. The outer clay coats, composed of well-crystallized chlorite, are possibly the result of neoformation directly from Fe- and Mg-rich pore water. The distribution of inner clay coats is controlled by sediment transport and deposition processes. The inner illite coats that are better developed in terms of content and thickness typically form in low energy braided channels due to relatively less transport abrasion of the smectitic clay precursors. The inner chlorite coats are observed exclusively in high energy mud clast-rich braided channels. The abundance of mud clasts and Fe-rich clay precursors are likely derived from the intense erosion of adjacent overbank mudstones, which are enriched in flocculated fluvial Fe oxides and hydroxides. The high coverage outer chlorite coats tend to occur in high energy braided channels with well-developed primary pores, since they provide sufficient growth space for chlorite. High energy braided channels with relatively low ductile component content generally maintain better porosity and permeability, which facilitates the development of the outer chlorite coats, thereby preserving more pore space by inhibiting quartz cementation and promoting subsequent dissolution of unstable silicate minerals, further improving reservoir quality. The results of this study provide new insights into the prediction of chlorite-coated reservoir quality of gas fields in Xihu Depression while also being relevant to braided river sandstones having comparable depositional settings worldwide.

Hydrogeochemical Characteristics and Isotopic Tools Used to Identify the Mineralization Processes of Bottled Mineral Water in Morocco

Bottled waters are among the most important products in the human diet. In Morocco, eleven bottled mineral waters were analyzed (physicochemical composition and water stable isotopes) to identify their geologic origins and hydrochemical characteristics. The study of the ionic ratios shows that the mechanisms of water–rock interaction, such as the dissolution of carbonate and silicate minerals, influence the chemistry of these mineral waters, which are controlled by lithology and tectonics, sometimes with the influence of deep flux through fractures. The water from the Oulmes plateau shows a Na-HCO3 chemical facies in relationship with alkaline granite. Moreover, the carbonated waters (EMG and EMGL) are characterized by high concentrations of Si, Li, Rb, Sr, and Cs due to deep CO2 flux origin. The waters of Saiss, Middle Atlas, and Rif are of the Ca-HCO3 type linked mainly to carbonate formation. The stable isotope contents of water range from −7.74 to −5.35‰ for δ18O and −45.4 to −30.4‰ for δD. The recharge altitude of the aquifer was estimated to be between 250 and 1200 m, following a δ18O altitudinal gradient between 0.25 and 0.27‰ per 100 m. The industrial production process and the natural presence or artificial addition of CO2 can also influence the isotopic composition of water. These results can be a relevant guide to decision makers for better exploitation and assessment of the water quality.