Rock Dissolution Research Articles

Chemical Characteristics and Water Quality Assessment of Groundwater in the Dongjiang-Hanjiang River Basin, China

Groundwater plays an important role in the rapid economic development of the Dongjiang-Hanjiang River Basin. This paper uses the Gibbs model, ionic ratio coefficient analysis, factor analysis, water quality index method and human health risk assessment model to estimate the chemical properties and quality of groundwater in the Dongjiang-Hanjiang Basin. The ion concentration and proportion of SO42- water in the Hanjiang River Basin are higher than those in the Dongjiang River Basin. The groundwater ions come mainly from the dissolution of carbonate rocks, silicate rocks and saline rocks, some of which come from human activities such as industry and mining. Groundwater composition is controlled by rock dissolution, alternating cation adsorption, and human activities. The proportion of rock dissolution is the greatest, but the influence of human activities is obvious. The intensity of human activities such as industry, mining and agriculture is greater in the Hanjiang River Basin than in the Dongjiang River Basin. The overall groundwater quality is poor, and the Dongjiang River Basin is better than the Hanjiang River Basin. The above-standard factors are mainly pH, I−, NO3−, NH4+, As and Pb2+. Nitrate pollution in groundwater is harmful to health and the health risk of children from nitrate is higher than that of adults. The health risk in the Hanjiang River Basin is higher than that in the Dongjiang River Basin. This can serve as a vital reference for similar areas worldwide, offering guidance for groundwater management, pollution prevention and control.

The influence of major faults and fractures on the development of non-matrix porosity system in a pre-salt carbonate reservoir, Santos Basin – Brazil

Faults and fractures are central for characterizing the permeability distribution in carbonate reservoirs since they act as pathways for diagenetic fluids that often favor intense rock dissolution and permeability. Usually, high permeability zones and fractures are not easily recognized in seismic data due to limited resolution and they are often associated with higher concentrations of hydrocarbons or even significant fluid losses during drilling, thus creating a challenge for hydrocarbon exploration. In the Santos Basin, southeast Brazil, the pre-salt carbonate reservoirs from the Barra Velha Formation (BVE) are the main hydrocarbon producers in Brazilian Atlantic margin and well-known for being extremely heterogeneous, exhibiting complex dual-porosity systems. In this study, we built a conceptual model of these fracture zones and non-matrix porosity formation that helped narrowing the understanding of these complex systems. The characterization of faults and fractures was carried out using seismic, well-logs, and borehole image data to understand the influence of these structures in the porosity formation along the Barra Velha Formation. In the study area, three fault sets were defined (F1, F2, and F3) from seismic data. F1 represents to the larger faults, while the F3 fault set represents the smaller faults related to the reactivation of F1; both sets being oriented NE-SW. The F2 fault set is associated with the rift formation and is oriented to NNE-SSW. These three fault sets compartmentalized the studied area into different domains, each exhibiting distinct fracture sets. The natural open fractures were formed during the reactivation of rift faults and are oriented mainly NW, NNE-NNW, NE, and ENE and were identified across the entire study area, but with different intensity values. The fracture intensity closely relates to the distance from major faults where the wells with the highest fracture intensity occurs located 150–590 m from the larger F1 fault set. Scan-lines were conducted throughout the area to determine the fault width, and an average value of 1.2 km was established. Seven non-matrix porosity classes were characterized and classified into stratigraphically concordant and discordant non-matrix pore types at well scale through borehole image interpretation. The Barra Velha Formation exhibit higher occurrence of stratigraphically discordant non-matrix porosity related to fractured zones while stratigraphically concordant non-matrix porosity is mainly controlled by the paleotopography of the study area. Overall, non-matrix porosity formation tends to follow an orientation that suggests a preferential dissolution flow towards NE and ENE directions. Intervals with higher silica content shows a positive correlation with both fracture intensity and stratigraphically discordant non-matrix porosities. This work provides a conceptual model about the fractures and non-matrix porosity distribution in pre-salt carbonate rocks that can help address some of associated structural and stratigraphic uncertainties during field appraisal and development.

Chemical Spatiotemporal Characteristics and Environmental Driving Factors of Groundwater in Hetao Irrigation Area

To explore the chemical characteristics and environmental factors of groundwater in the Hetao Irrigation Area of Inner Mongolia, five irrigation fields, including UulanBuh, Jiefangzha, Yongji, Yichang, and Wulat, were selected as the research area. From 72 groundwater observation wells, a total of 216 groundwater samples were collected throughout three typical periods： the end of freeze-thaw （March）, the middle of irrigation （July）, and the end of autumn watering （November）. Comprehensive methods were utilized, such as statistical analysis, Piper three-line diagram, Gibbs diagram, ion ratio, and principal component analysis, to explore the changes in the groundwater chemical environment and the environmental driving factors of groundwater component formation. The groundwater drinking suitability was evaluated using the water quality index （WQI）, and the irrigation suitability was analyzed using the USSL and Wilcox plots. The results indicated that the groundwater in the research areas was generally saline, and the total anion and cation concentrations in each period in ascending order were as follows： late freeze-thaw stage, late autumn irrigation stage, and mid-irrigation stage, with Na+ and Cl- being the major contributing ions. The chemical type of groundwater was dominated by Cl-Na, followed by Cl·SO4-Ca·Mg and a coexistence with SO4-Ca·Mg, HCO3·Cl-Na, HCO3-Na, and HCO3-Ca·Mg. Based on WQI values, the shallow groundwater in Hetao Irrigation District was mainly classified as Class IV and Class V, and the quality was poor in general. According to the USSL diagram and Wilcox diagram, the comprehensive evaluation results showed that the salinity and sodium concentration of shallow groundwater in the irrigation area were generally high. A total of 80.6% of the water samples during the late freeze-thaw period, 76.1% during the mid-irrigation period, and 77.6% during the late autumn irrigation period lacked irrigation suitability. Two major controlling factors of groundwater chemical characteristics were present in the study area, namely, evaporation and rock weathering, and Na+ and Cl- mainly came from the dissolution and cation exchange of salt rocks. Agricultural irrigation and drought were the chief driving factors of groundwater chemical evolution in the Hetao Irrigation Area. The study provides technical support for optimizing agricultural management measures and a theoretical reference for rational utilization of groundwater resources in the Yellow River irrigation area of Inner Mongolia.

Modeling the impact of pH and reservoir temperature on the dissolution of quartz mineral due to oilfield chemical treatment

The petroleum industry frequently uses oilfield chemicals, such as corrosion inhibitors, scavengers, drilling fluid, and chemical enhanced oil recovery methods, to improve oil recovery. However, these chemicals can negatively impact the geochemical characteristics of the formation, potentially leading to facility failure and reservoir formation damage. A study using PHREEQC was conducted to predict the impact of reservoir temperature and pH on quartz rock dissolution under different temperatures and pH levels. The results showed consistent dissolving rates for quartz at different pH levels. The solubility of quartz minerals was slightly affected by the solution pH, suggesting that the process variable pH has little effect on the equilibrium rate. However, precipitation caused quartz to dissolve at a rate of 0.04 mmol.L−1.s−1 at 45 °C but increased to 0.07 mmol.L−1.s−1 at 65 °C in 0.8 s. As temperature increased, quartz and NaNO3 solution interaction reached equilibrium concentrations in 0.8 and 2.7 s. The study concluded that temperature significantly impacts quartz dissolution during interaction with sodium nitrate oilfield chemicals compared to pH. The PHREEQ software is a useful research tool for simulating rock-fluid interactions resulting in reservoir formation dissolution and precipitation, which can cause formation damage and sand production.

Optimizing the heat extraction performance in the Qingfeng Karst geothermal reservoir

Faults are typically associated with hydrothermal reservoirs and may control the heat extraction of geothermal reservoirs. However, in Karst geothermal reservoirs, the dissolution of soluble rocks results in pronounced spatial porosity and permeability anisotropy (PPA), potentially weakening the dominant role of faults. The question arises: which plays a dominant role, PPA or faults? Should geothermal exploitation strategies be adjusted under the interaction of both factors? In this study, we proposed a coupled Thermal-Hydraulic-Geothermal Wellbore (THG) numerical simulation model to streamline the integration of non-isothermal flow and heat transfer processes within a 3D wellbore. Utilizing this model, we analyzed the influence of faults compared to PPA and assessed the geothermal well doublet's heat extraction performance, including thermal breakthrough time, temperature losses along the wellbore wall, and recovery factor (Rg). There are specific geothermal reservoir development conditions leading to the latest thermal breakthrough time and the maximum Rg. The results of contribution rates highlight the influence of injection rate in determining Rg. It is crucial to note that thermal breakthrough time does not necessarily increase with injection temperatures. A more suitable definition for thermal breakthrough time in the Karst geothermal reservoir has also been identified. This study provides an essential reference value for the efficient development of similar Karst geothermal reservoirs.

Major Ion Chemistry of Surface Water and Its Controlling Factors in Ebinur Lake Basin

The sustainable development of arid regions is significantly constrained by the availability of water resources, which play a crucial role in this context. It is necessary to deeply investigate and analyze the hydrochemical characteristics and major ion sources. This study, which was based on data from 183 water samples collected from the Jinghe River Basin, provided a comprehensive analysis of the river water hydrochemistry. The results show that the average TDSs (total dissolved solids) was measured at 49.8 mg·L−1. HCO3− (82.4%) and Ca2+ (77.1%) were the ions present in the highest abundances. The river water was classified as the HCO3−-Ca2+ hydrochemical type. The Gibbs diagrams indicated that the ion composition was primarily influenced by rock weathering. Additionally, the Na-normalized molar ratio diagrams suggested that the chemical composition was primarily governed by the weathering and dissolution of silicate rocks, while the carbonate rock dissolution played a lesser role. This study demonstrates a critical aspect of water resources quality evaluation, which is of great significance for the sustainable development, utilization and environmental protection of regional water resources.

Hydraulic and Hydrogeochemical Characterization of Carbonate Aquifers in Arid Regions: A Case from the Western Desert, Egypt

Using geochemical and pumping test data from 80 groundwater wells, the chemical, hydrologic, and hydraulic properties of the fractured Eocene carbonate aquifer located west of the Al-Minya district, the Western Desert, Egypt, have been characterized and determined to guarantee sustainable management of groundwater resources under large-scale desert reclamation projects. The hydrochemical data show that groundwater from the fractured Eocene carbonate aquifer has a high concentration of Na+ and Cl− and varies in salinity from 2176 to 2912 mg/L (brackish water). Water–rock interaction and ion exchange processes are the most dominant processes controlling groundwater composition. The carbonate aquifer exists under confined to semi-confined conditions, and the depth to groundwater increases eastward. From the potentiometric head data, deep-seated faults are the suggested pathways for gas-rich water ascending from the deep Nubian aquifer system into the overlying shallow carbonate aquifer. This mechanism enhances the dissolution and karstification of carbonate rocks, especially in the vicinity of faulted sites, and is supported by the significant loss of mud circulation during well drilling operations. The average estimated hydraulic parameters, based on the analysis of step-drawdown, long-duration pumping and recovery tests, indicate that the Eocene carbonate aquifer has a wide range of transmissivity (T) that is between 336.39 and 389,309.28 m2/d (average: 18,405.21 m2/d), hydraulic conductivity (K) between 1.31 and 1420.84 m/d (average: 70.29 m/d), and specific capacity (Sc) between 44.4 and 17,376.24 m2/d (average: 45.24 m2/d). On the other hand, the performance characteristics of drilled wells show that well efficiency ranges between 0.47 and 97.08%, and well losses range between 2.92 and 99.53%. In addition to variations in carbonate aquifer thickness and clay/shale content, the existence of strong karstification features, i.e., fissures, fractures or caverns, and solution cavities, in the Eocene carbonate aquifer are responsible for variability in the K and T values. The observed high well losses might be related to turbulent flow within and adjacent to the wells drilled in conductive fracture zones. The current approach can be further used to enhance local aquifer models and improve strategies for identifying the most productive zones in similar aquifer systems.

New insights on the hydrochemistry, geothermometry, and isotopic characteristics of the hydrothermal groundwater of the SASS basin: case study of the Jérid geothermal field, Southern Tunisia.

Chemical and isotopic indicators were used to recognize the origin of hydrothermal groundwater, to assess the mineralization processes and groundwater quality, to identify the source of solutes and the likely mixing with cold, and elucidate the fluid geothermometry in the Jérid field of Southern Tunisia. The results show that the geothermal groundwater is neutral to slightly alkaline. They are characterized by SO4-Cl-Na-Ca water type. The dissolution of evaporates and pyrite-bearing rocks is the dominant mineralization process. The groundwater quality index indicates that the majority of samples are very hard and belong to poor to unsuitable for drinking classes. Applications and calculations of hydrogeochemical parameters, including SAR, %Na, PI, Kr, and MAR, showed that the majority of samples are unsuitable for agricultural practices. The human health risk was assessed based on hazard quotient and total hazard index through ingestion and dermal contact with iron-rich groundwater. The consumption of CI groundwaters does not present non-carcinogenic risk to adults and children. The δ18 O and δ2H signatures indicate that the geothermal groundwater was recharged by ocean precipitation during cold and wet paleoclimatic periods. The slight enrichment of oxygen-18 and deuterium contents suggests a limited mixing effect between geothermal water and cold groundwater within the same aquifer. This mixing effect is confirmed by the Na-K-Mg and the chloride-enthalpy diagrams. The K-Mg and SiO2 geothermometers provided fairly reliable reservoir temperature values, ranging between 69.6 and 99°C. Calculated geothermal potential values, varying between 469 and 16987 kWth, which allow several applications such as domestic and agricultural heating.

Cumulative effects of natural and anthropogenic processes on groundwater chemistry of a small karst island—case study of Vis (Croatia)

Many coastal and island communities depend on groundwater as the only source of freshwater, making it an invaluable resource. In the Mediterranean region, groundwater resources are highly vulnerable to natural and anthropogenic pressures, such as overexploitation, climate change, seasonal variations in precipitation, and seawater intrusion. Hence, an understanding of hydrogeological processes and groundwater chemistry is a basis for the sustainable management of coastal and island groundwater resources. Vis, a small and remote karst island in the Adriatic Sea, exhibits peculiar geological and hydrogeological settings, resulting in the island’s autonomous water supply. The current pumping capacity (maximum of 42 l/s) meets most of the demand, but intensive summer tourism and climate change exert high stress on groundwater resources during the dry season. Consequently, in the last decade, occasional reductions for consumers occurred. Monitoring of in situ physicochemical parameters and groundwater sampling for chemical and isotopic analyses were conducted from 2020 to 2023 at deep borewells, shallow dug wells, and springs. Hydrochemical interpretation indicated that groundwater chemistry was affected primarily by carbonate and sulfate rock dissolution, mixing with seawater, reverse ion exchange, and dedolomitization. The majority of groundwater samples exhibit Ca–HCO3 hydrochemical facies, followed by Na–Cl and mixed facies. The low percentage of seawater in the mixture indicated that seawater intrusion is not too extensive even during prolonged dry periods, implying a favorable hydrostatic regime with relatively small but sufficient groundwater reserves of the island’s aquifers, although the investigated period was characterized by significantly lower precipitation with respect to the 30-year average.

Identifying the genesis of hydrothermal activities in the Xiangcheng fault belt, southwestern China: Evidence from hydrochemistry and stable isotopes

Regional faults are beneficial structures for the formation of hydrothermal activities and have thus become target areas for geothermal resource utilization. Numerous hydrothermal activities have been reported along the Xiangcheng fault belt, particularly concentrating in the Batang, Xiangcheng and Shangri-La areas. In this study, hydrochemistry and stable isotopes were used to identify the genesis of hydrothermal activities in the Xiangcheng fault belt. The pH values of the geothermal water in these regions gradually decreases in this order, while the total dissolved solids gradually increase. The δD and δ18O values indicate the geothermal waters are mainly originated from snowmelt water and meteoric water. The recharge elevation of geothermal waters in Batang, Xiangcheng, and Shangri-La was 4415–4904 m, 4585–5038 m, and 3673–3969 m, respectively. Most geothermal waters belong to the hydrochemical type HCO3-Na, however some Batang geothermal water is of the SO4·HCO3-Na type, influenced by deep geothermal gas, and some Shangri-La geothermal water is of HCO3-Ca·Na type, influenced by shallow cold water and dissolution of carbonate rocks. Correlations of major ions suggest that HCO3-Na type geothermal waters are determined by the dissolution of paragonite, K-feldspar and albite as well as positive ion exchange. According to Na-K-Mg triangle diagram and mineral saturation indices, the geothermal waters do not reach full equilibrium and are mixed with shallow cold. Geothermometers, including cationic and SiO2, and geochemical thermodynamic calculations indicate that the deep and shallow reservoir temperatures are 200–240 °C and 169–193 °C for the Batang area, 194–201 °C and 119–131 °C for the Xiangcheng area, and 156–178 °C and 100–109 °C for the Shangri-La area. Conceptual models of the genesis of hydrothermal activities in the Batang, Xiangcheng, and Shangri-La areas were constructed, respectively. CaCO3 scaling is dominated in the study area. The hydrothermal activities of Batang and Xiangcheng areas with enriched deep materials and high reservoir temperatures are beneficial for rare-alkali metal (e.g., Li). The findings of this study provide a scientific basis for the development and utilization of geothermal resources in the high-temperature hydrothermal activity areas of western Sichuan.

DEVELOPMENT OF AN ALGORITHM FOR CALCULATING THE RATE CONSTANT OF HYDROCHLORIC ACID REACTION WITH A CARBONATE ROCK FORMATION

One of the main factors reducing acid stimulation efficiency is the intensive reaction of active acid in the immediate vicinity of the wellbore, which leads to insufficient completeness of reservoir rock dissolution in the remote reservoir zone. The reservoir hydrodynamic characteristics are not being improved properly, and the efficiency of oil production stimulation measures does not reach the planned values.To get high results of acid treatments it is necessary to achieve deep penetration of acid into the formation thickness. The reaction rate constant is used to compare the reactivity of different acid compositions and to select the most suitable acid composition for the geological and physical conditions of the treated object, which provides the highest treatment efficiency. It relates the initial substances concentrations with reaction products formation rate. To determine the reaction rate constant, a volumetric apparatus was created and methodological aspects were developed to work on it, allowing to minimize the measurement error and to achieve the greatest accuracy in determining the kinetic parameters of the reaction. But in the course of further investigations in the work of the existing algorithm for experimental data processing, a number of significant deficiencies distorting the results of calculations were revealed. The aim of the research is to develop a new improved algorithm for reaction rate constant calculation, which will improve the understanding of the process of determining the kinetic parameters of acid reaction with carbonate rock.To achieve this aim, the authors conducted a series of experiments according to the unified methodology, the results of which revealed ways to eliminate the identified deficiencies using a new algorithm. It includes obtaining and saving initial data, subsequent treatment and direct calculation of reaction kinetic parameters with results saving.The developed algorithm makes it possible to unify and automate the process of determining the kinetic parameters of the acid reaction with the formation rock, as well as to determine the reaction characteristics with higher accuracy and reduce the influence of the human factor on the research results, thus reducing the errors of the calculation results.

Hydrogeochemical evolution patterns of diverse water bodies in mining area driven by large-scale open-pit combined underground mining-taking Pingshuo Mining Area as an example

Large-scale open-pit combined underground mining activities (OUM) not only reshape the original topography, geomorphology, and hydrogeochemical environment of the mining area, but also alter the regional water cycle conditions. However, due to the complexity arising from the coexistence of two coal mining technologies (open-pit and underground mining), the hydrological environmental effects remain unclear. Here, we selected the Pingshuo Mining Area in China, one of the most modernized open-pit combined underground mining regions, as the focus of our research. We comprehensively employed mathematical statistics, Piper diagram, Gibbs model, ion combination ratio, principal component analysis and other methods to compare the hydrochemistry and isotope data of different water bodies before (2006) and after (2021) large-scale mining. The changing patterns of hydrochemical characteristics of different water bodies and their main controlling factors in mining area driven by OUM were analyzed and identified, revealing the water circulation mechanism under the background of long-term coal mining. The results showed that: (1) The chemical composition of water has changed greatly due to large-scale coal mining. The hydrochemical types of Quaternary and Permian-Carboniferous aquifers shifted from predominantly HCO3-Ca·Mg before intensive mining to primarily HCO3·SO4-Ca·Mg, HCO3-Na, HCO3·SO4-Na·Mg, and HCO3·SO4-Ca·Mg, HCO3-Ca·Na, HCO3·SO4-Mg·Ca post-mining. Variations in the hydrochemical types of surface water were found to be complex and diverse. (2) Coal mining activities promote the dissolution of silicate rock and sodium-bearing evaporites, enhancing the strength and scale of positive alternating adsorption of cations. The oxidation of pyrite, dissolution of silicate weathering, and the leaching of coal gangue were identified as the main reasons for the significant increase of SO42−, while decarbonation in confined aquifers led to a decrease in HCO3−. (3) Results from the principal component analysis and stable isotopes demonstrated the hydraulic connection among surface water, Quaternary aquifers, and Permian-Carboniferous aquifers induced by long-term OUM. The research findings provide a reference basis for the coordinated development of coal and water in the Pingshuo Mining Area and other open-pit combined underground mining areas.

Experimental analysis of primary factors controlling carbonate rock dissolution capability and its impact on geothermal reservoir modification

Experimental analysis of primary factors controlling carbonate rock dissolution capability and its impact on geothermal reservoir modification

Water Quality Assessment of the Euphrates River from Haditha to Al-Nasiriyah, Iraq

A comprehensive assessment of four gauging stations along the Euphrates River reach (Haditha, Al-Hindiya, Samawa, and Al-Nasiriyah) was conducted to assess the water quality deterioration spatially and temporarily for the period 2005-2021. The spotlight is on discharge rates and climate conditions, which mainly controlling water quality and availability. The mean monthly discharge rate was taken 2005–2021, in addition to the water quality parameters (TDS, pH, EC, Mg+2, Ca+2, Na+, SO4-2, Cl-, and HCO3-, BOD5, COD, FCB, and E. coli). The discharge rates showed a visible decrease downstream, causing the river salinity and all the ion concentrations to rise. The statistical package of social sciences revealed two groups of water pollution sources: The F1 reflects natural conditions produced from the dissolution of the basin rocks, with a percentage of 28.0% from the total variance; the eigenvalue is 4.4. F2 reflects the anthropogenic sources, contributing 14.5% and having an eigenvalue of 2.1. The total ionic salinity plot indicated less than 2000 mg/l at the Haditha and Al-Hindiya sites and between 3000 and 4000 mg/l at downstream sites (Samawa and Al-Nasiriyah). The transportation of dissolved loads is decreased downstream following the discharge rate as indicated by the rating curves, as follows: 781000, 542628.4, 443861, and 432950.4 tons/month for Haditha, Al-Hindiya, Samawa, and Al-Nasiriyah, respectively. Water type shows a notable downstream deterioration, from MgSO4 at Haditha and Na2SO4 at Al-Hindiya to NaCl at Samawa and Al-Nasiriyah sites.

Source-oriented health risk assessment of groundwater based on hydrochemistry and two-dimensional Monte Carlo simulation

Accurately assessing the health risks posed by major contaminants is essential for protecting groundwater. However, the complexity of pollution sources and the uncertainty of parameters pose challenges for quantitative health risk assessment. In this study, a source-oriented groundwater risk evaluation process was improved by screening key pollutants, employing a combined hydrochemical and positive matrix factorization (PMF) approach for source apportionment, and incorporating two-dimensional Monte Carlo simulation for risk characterization. The application of this process to groundwater assessment in Central Jiangxi Province identified NO3-, F-, Se and Mn as the key pollutants. The pollution sources were anthropogenic activities, rock dissolution, regional geological processes, and ion exchange. Anthropogenic sources contributed 36.8 % and 28.8 % of the pollution during the wet season and dry season, respectively, and accounted for more than half of the health risks. NO3- from anthropogenic sources was the primary controlling pollutant. Additionally, the risk assessment indicated that children were at the highest health risk during the dry season, with ingestion rate suggested to be controlled below 1.062 L·day−1 to make the health risk within an acceptable range. The improved assessment methodology could provide more accurate results and recommended intakes.

An experimental investigation on the damage mechanisms of red glutenite in the Mount Wuyi cultural and natural heritage site subject to acid rain and wet-dry cycles: a macro-to-micro approach

The safety of rock landscapes in Mount Wuyi is significantly impacted by acid rain and wet-dry cycles. In this paper, the decay characteristics of the physical–mechanical properties of red glutenite were investigated under acidic wet-dry cycles. A systematic approach, including cold field emission scanning electron microscopy (CFE-SEM), image processing techniques, and X-ray diffraction (XRD), was proposed to investigate the damage mechanism of red glutenite under acidic wet-dry cycles. The results indicate that with increasing solution acidity and wet-dry cycles, dry density (DD), longitudinal wave velocity (LWV), uniaxial compressive strength (UCS), and elastic modulus (EM) of red glutenite significantly decrease. Under different acidic conditions, DD, LWV, and UCS exhibit exponential decay with wet-dry cycles, while EM exhibits linear decay. A regression fitting was employed to establish a prediction model for UCS, which exhibited a better capability in predicting the correlation between UCS, pH, and the number of wet-dry cycles. Microscopic comprehensive analysis reveals that the interaction between rock dissolution and desiccation is the primary factor leading to changes in the microstructure and mineral composition of red glutenite, culminating in the decay of its physical–mechanical properties. This study holds significant guidance implications for the preservation of cultural and natural heritage in Mount Wuyi.

Understanding zinc isotopic signatures in volcanic lakes

Magmatic activity can be monitored through the chemical variations of volcanic lakes. While those lakes can be influenced by direct magmatic input, water-rock interaction processes in hydrothermal system also have a large influence. Disentangling those effects is critical to use crater lakes for volcanic activity monitoring purposes. Zinc is a volatile metal that is easily degassed and can be incorporated into fluid circulation. During degassing, Zn isotopes can be fractionated and can thus be a potential tracer of magmatic input. Here we present a novel approach using stable Zn isotopic systems to understand how dissolution/precipitation processes affect isotopic compositions of volcanic lakes and if they can be used as tracers of magmatic activity. We investigate Zn isotopes expressed as δ66Zn for four volcanic lakes ranging from hyperacidic to neutral waters. Two of them, Kawah Ijen (Indonesia) and Santa Ana (El Salvador) volcanic lakes have been sampled from 2010 to 2012 and 2000–2002, respectively, and show a clear magmatic input with extremely low pH [0.1–1]. Taal (Philippines, pH ≈ 3) and Kelud (Indonesia, pH ≈ 6.5) volcanic lakes were sampled from 2017 to 2019 and 2003–2007 respectively, and are dominated by hydrothermal rather than magmatic inputs. Hyper-acidic lakes show minimal isotopic variation over the investigated time ranges, with δ66Zn values similar to their basalt-andesitic host rocks (0.26 ± 0.08 ‰). In contrast, we observe large δ66Zn fractionation for the Taal waters (0.4 ± 0.01 ‰) compared to their basalt-andesitic host rocks but no δ66Zn temporal variations. Kelud waters show significant δ66Zn (−0.08 ± 0.06 ‰ to 0.43 ± 0.06 ‰) temporal variation. This could be related to an evolution of the lake water chemistry as the sampling period occurred between two increases in lake temperature culminating into a lava dome eruption in 2007. For Taal and Kelud volcanic lakes, enrichment factors (EF) and PHREEQc modelling indicate that Zn is depleted and suggest that Zn could precipitate in the hydrothermal system, hence fractionating Zn isotopes during these precipitation processes. This contrasts to Zn elemental and isotope values from Kawah Ijen and Santa Ana with an EF ≈ 1 suggesting that Zn is derived from host rock dissolution, in agreement with their δ66Zn. These data are still limited and a longer observation is needed in the future to highlight significant geochemical changes in volcanic lakes and their relation to volcanic activity.

Arsenic-contaminated groundwater of the Western Banat (Pannonian basin): Hydrogeochemical appraisal, pollution source apportionment, and Monte Carlo simulation of source-specific health risks.

Due to rapid urbanization and industrial growth, groundwater globally is continuously deteriorating, posing significant health risks to humans. This study employed a comprehensive methodology to analyze groundwater in the Western Banat Plain (Serbia). Using Piper and Gibbs plots, hydrogeochemistry was assessed, while the entropy-weighted water quality index (EWQI) was used to evaluate groundwater quality. Pollution sources were identified using positive matrix factorization (PMF) accompanied by Pearson correlation and hierarchical cluster analysis, while Monte Carlo simulation assessed health risks associated with groundwater consumption. Results showed that groundwater, mainly Ca-Mg-HCO3 type, is mostly suitable for drinking. Geogenic pollution, agricultural activities, and sewage were major pollution sources. Consumption of contaminated groundwater poses serious non-carcinogenic and carcinogenic health risks. Additionally, arsenic from geogenic source was found to be the main health risks contributor, considering its worryingly elevated concentration, ranging up to 364 μg/L. These findings will be valuable for decision-makers and researchers in managing groundwater vulnerability. PRACTITIONER POINTS: Groundwater is severely contaminated with As in the northern part of the study area. The predominant hydrochemical type of groundwater in the area is Ca-Mg-HCO3. The PMF method apportioned three groundwater pollution sources. Monte Carlo identified rock dissolution as the primary health risk contributor. Health risks and mortality in the study area are positively correlated.

Arsenic and metal levels in snake tissues from Lagoa Santa Karst, Brazil.

Concentrations of one metalloid (As) and eight metals (Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) were determined in tissues (muscle, liver, and kidney) of eight snake species (Bothrops neuwiedi, Crotalus durissus, Dipsas mikanii, Epicrates crassus, Helicops modestus, Micrurus carvalhoi, Oxyrhopus guibei, and Oxyrhopus trigeminus) from Lagoa Santa Karst. Except for Cu and Zn, all other analyzed elements were detected in concentrations within the ranges previously reported for snakes inhabiting polluted areas, emphasizing Hg (specific Hg mean concentrations varied from 0.87 to 9.76μgg-1 d.w). The highest mean concentrations of all elements except Zn were found in muscle samples of the false corals O. guibei (means ranged from 2.01 [Pb] to 9.76 [Hg]). The highest Zn mean concentration (13.77μgg-1 d.w) was detected in the kidney of the water snake H. modestus. No significant correlation was found between element concentrations and body size for all species. Significant interorgan differences were observed for As, Cr, Cu, Hg, Mn, Pb, and Zn concentrations in the three tissues in H. modestus. Significant interspecific differences were found in at least one organ for all elements. Significant pairwise differences were found between diet specialist species and between these species and broader diet species, while no significant difference was found between the broader diet species. The bioaccumulation of As and metals in snakes from Lagoa Santa Karst could be associated with natural rock dissolution and erosion processes but also with the wide-scale mining in the region and the increased agriculture and urbanization.

An Analytical Method for Quantification of Sn Isotope Variations in Geological Materials Using MC‐ICP‐MS

A robust analytical method is presented here, for measurements of Sn isotope variations with high precision using a multi‐collector inductively coupled plasma‐mass spectrometer (MC‐ICP‐MS). A silicate rock dissolution procedure was used, together with means to remove organic matter introduced by the resin during ion‐exchange chromatography. The two‐stage ion exchange chromatography efficiently isolates Sn from the matrix and isobarically interfering elements, from samples with variable Sn mass fractions (~ 0.03 to 7 μg g−1). A double spike technique was also implemented to correct any secondary mass bias induced during sample processing and isotope ratio measurements. An intermediate precision (2s) of ± 0.47 was obtained for ε122/118Sn (using internal normalisation; n = 70 over a period of 29 months), ± 0.021‰ for δ122/118Sn (using double spike; n = 176 over a period of 29 months) and ± 0.059‰ for δ122/118Sn (using Sb doping; n = 34 over a period of 4.5 months) for the Sn standard solution, NIST SRM 3161a (Lot# 140917). The δ122/118SnNIST SRM 3161a of eleven geological reference materials are reported for the first time (BIR‐1a, BRP‐1, DTS‐2b, ECRM 782‐1, JP‐1, OKUM, QLO‐1a, RGM‐2, SGR‐1b, STM‐2 and UB‐N), with five others (AGV‐2, BCR‐2, BHVO‐2, GSP‐2 and W‐2a) showing similar results to previous studies, generally with improved precision. The intermediate precision (2s) of replicate dissolutions of ten RMs (AGV‐2, BCR‐2, BHVO‐2, BIR‐1a, DTS‐2b, GSP‐2, OKUM, SGR‐1b, STM‐2 and W‐2a) varied from 0.003 to 0.054‰. Typical repeatability precision (2SE) of individual measurements of these ten RMs over multiple measurement sessions varied from 0.031 to 0.297‰ (with 120Sn+ beam intensity < 2.37 V) and 0.017 to 0.025‰ (with 120Sn+ beam intensity > 2.37 V).