Water Rock Research Articles

The Optimization of Waterproof and Drainage Design and an Evaluation of the Structural Safety of Tunnels in Weak Watery Strata

The surrounding rock and high water pressure in weak watery strata have adverse effects on the mechanical properties of tunnel support structures. In order to optimize the anti-drainage design of tunnels in weak watery strata and evaluate their structural safety, this paper relies on the Taidacun Tunnel of the China–Laos Railway to carry out field monitoring research. A dual-field fluid–solid coupling calculation model is established to optimize the tunnel’s waterproof and drainage design, combined with a bending moment curvature model to evaluate structural safety. The main conclusions are as follows: Under the action of high water and soil pressure, the structural safety margin of the water-rich fine sand section of the Taidacun Tunnel is small, and waterproof and drainage design optimization is required. Combined with the proposed average pressure reduction coefficient, the influence of the water level and annular blind pipe spacing on the water pressure of the lining is proved, and then the optimal annular blind pipe spacing in the water-rich area of the tunnel is determined. A structural safety evaluation method based on the bending moment curvature model is proposed. Two models of elastic beam and moment–curvature beam are used to analyze the mechanical characteristics and optimization effects of the structure under optimal annular blind pipe spacing.

Groundwater trace element changes were probably induced by the ML3.3 earthquake in Chaoyang district, Beijing

Geochemical composition changes in groundwater related to earthquakes have been documented in previous studies, and most such studies focused on the changes in major ions, hydrogen, oxygen isotopes, and geochemical gases. Changes in trace elements were suggested to be more sensitive to small earthquakes than the commonly used chemical constituents such as major ions, yet they received less attention. Beijing is located in the Zhangjiakou-Bohai seismic belt and experiences frequent occurrences of small earthquakes. In this paper, we collected groundwater samples from a hot spring in Yanqing district of Beijing weekly from August 2021 to August 2022. Each water sample contained 41 trace chemical compositions. During the sampling, an earthquake with a magnitude of ML3.3 occurred in the Chaoyang district of Beijing on 3 February 2022, so these trace elements changes were systematically monitored before and after the earthquake: Li, Sc, Ti, and Pb elements had upward changes before the earthquake, while Cu, Nb, Th, Zn, Tl, and U elements had downward changes before the earthquake. Eu (rare earth elements) had upward changes after the earthquake. At the same time, the earthquake caused no significant changes in the groundwater level in the seismic monitoring well near the Songshan spring. Such responses indicate that trace elements are likely to be more sensitive to crustal strain than groundwater level. We considered that the earthquake-induced rock cracks before or after the earthquake caused enhancing water-rock interaction and led to the migration of trace elements between the water column and rocks, which is the mechanism to explain the trace elemental changes. This study probably provides a comprehensive assessment of the sensitivity of trace element constituents to the earthquake. Furthermore, we suggest that more long-term continuous monitoring and research of trace elements in Beijing and Zhangjiakou-Bohai Fault Zone should be considered to explore the response mechanism of groundwater geochemistry to earthquakes in the future.

Using hydrogeochemical facies and signatures for groundwater characterization and evolution assessment in aquifers with contrasting climate and geology in Tanzania

This study aimed at characterizing groundwater evolution using hydrogeochemical facies and signatures in two basins with contrasting climate and geology, one in the central part and the other in the eastern coast of Tanzania. The Kimbiji (humid, unconsolidated) aquifer is covered by an unconfined layer in the upper parts and a confined layer in the lower parts, with strong artesian flow characteristics while groundwater in the Singida (semi-arid, consolidated) aquifer occurs in weathered shallow layers and in fractures of basement rocks. Fieldwork involved water sampling from precipitation, deep and shallow boreholes, springs and surface water from rivers and lakes in the two study areas. These were specifically conducted for hydrogeochemical analyses to unravel hydrogeochemical facies and signatures in the two aquifers. Physico-chemical water quality parameters [i.e., pH, electrical conductivity (EC) and total dissolved solids (TDS)] were measured in situ using HANNA HI 9829 Multiparameter Analyzer. Standard procedures for water sampling, preservation, transportation, and chemical analyses of major ions were conducted as documented in previous studies. Samples were carried and stored at 4 °C prior to their shipping and analyses at Water analysis and testing in environmental regions (WATER) laboratory in Iringa, Tanzania. The mechanism controlling groundwater geochemistry were revealed by assessing the reactions between groundwater and aquifer minerals. Chloro-Alkaline indices (CAIs) were used to study cation exchange processes between the groundwater and its host environment at stagnancy and/or during groundwater travel. The Gibbs ratio 1 values were found to range from 0.26 to 0.94 and Gibbs ratio 2 values ranged from 0.11 to 0.95. The majority of the samples irrespective of the contrast in climate and geology were observed to fall in the rock–water interaction zone. This is attributed to chemical weathering processes where the dissolution of rock forming minerals takes place. Some samples exhibited replacement of Na+ by Ca2+ or Mg2+ (S18), loss of Na+ through precipitation of evaporate rocks (S11, S13, S16, S19), and water flowing through crystalline rocks (S1, S2, S4, S6, S8, S10, S12, S13, S14, S21). The ratio Na+: Ca2+ > 1.0 (S1, S4, S8, S10, S12, S14, S17, S18, S19, S21) explains base ion exchange while the ratio < 1 implies a reverse ion exchange (S2, S6, S11, S13, S16).The Ca2+: SO42− + HCO3− ratio < 1.0 connotes groundwater flowing through a normal hydrological cycle (S1, S4, S8, S10, S12, S14, S17, S18, S2, S6, S11, S13, S21) and a ratio greater than 1 is an indication of Ca2+–Cl− brines (S16, S19). The HCO3−: Cl− hydrogeochemical signatures divided the Singida aquifer into upper water flow course, where groundwater recharge occurs (S52, S54, S56, S57, and S58) and the discharge zone, (S53, S59, S60, S61) which is a lower groundwater flow course. Interestingly, the Mg2+ + Ca2+: Na+ + K+ ratios as well confirmed that the Singida aquifer is a lower groundwater flow course (discharge zone). The greater than 1 Na+: Ca2+ ratios confirm the dominance of base ion exchange in the Singida aquifer as it has been explained by the CAIs and the Piper diagram. The Gibbs diagrams revealed that the hydrochemistry of groundwater in the Kimbiji and Singida aquifers are mainly in the rock weathering region, affirming that there is high dissolution with rock forming minerals. This is thus one of the main controls of groundwater mineralization in the two study areas. The similarity of hydrogeochemical signatures between a distant surface water body, Lake Inkhanoda and Mwankoko borehole in the Singida aquifer is an indication that there is a discernible interaction between groundwater and surface water, further revealing that the Singida aquifer is fed by sub-regional and regional groundwater flow systems.

Heat flow characteristics and thermal resistance model for soil-rock mixtures during freezing-thawing processes: Damping properties

As a special heterogeneous geological material, soil-rock mixtures are widely distributed in nature and used in civil engineering. Heat flow is one of the most significant factors affecting the development of water balance and redistribution, ground temperature evolution, and heat transport processes in cold regions. This study explores the heat flow characteristics and generalized thermal resistance model for soil-rock mixtures during freezing-thawing processes. A series of freezing-thawing experiments for soil-rock mixtures with different rock contents (i.e., 10%, 25%, and 40%) were conducted. The effects of rock content and water–ice phase transition on heat flux during the freezing-thawing processes were analyzed, and the damping properties of heat flow for soil-rock mixtures during freeze–thaw cycles were found and illustrated. Subsequently, a generalized thermal resistance model for soil-rock mixtures was proposed and discussed. The results show that the freezing-thawing processes and rock content significantly influence the heat flux and soil temperature of the soil-rock mixtures. Regardless of rock content, the sums of heat flux in freezing and thawing stages all firstly decreased, and then gradually tends to be stable with freeze–thaw cycles. Besides, the reduction of volumetric unfrozen water content increases with the freeze–thaw cycles, and the amplitude of unfrozen water reduction for sample with high rock content is larger than that with low rock content. Additionally, owing to the effect of the latent heat released by water/ice phase transition and thermal sensitive property of rock, the variation of heat flow for soil-rock mixtures presents damping property in the stages without completely freezing, and the variation of heat flow exhibits reversed damping property in the post-freezing stages due to the denser structure and ice crystal growth. Furthermore, based on the thermal resistance in series, characteristics of water–ice phase transition, and thermal sensitive property of rocks, a new generalized thermal resistance model of soil-rock mixtures during freezing-thawing processes is proposed.

Geochemical simulation to assess the rock–water interaction in crystalline aquifers in São Paulo State, Southeastern Brazil

Geochemical simulation to assess the rock–water interaction in crystalline aquifers in São Paulo State, Southeastern Brazil

Effects of ice content on compression characteristics of frozen sandstone by in-situ NMR technology

In cold regions, the freezing of pore water in rock affects the mechanical behavior of the rock. This paper studied the ice content of frozen sandstone at different temperatures and its effects on the mechanical properties of sandstone. First, the progressive freezing treatment (from 25.0 to − 30.0 °C) and in-situ nuclear magnetic resonance test were conducted to study the evolution of the ice content of sandstone with temperature. This evolution was quantitatively described by the frozen ratio defined as the percentage of the mass of ice and the total mass of water. Then, the mechanical properties of frozen sandstone at different temperatures (25.0 °C, 0.0 °C, − 5.0 °C, − 10.0 °C, − 20.0 °C and − 30.0 °C, respectively) were tested, such as P-wave velocity, uniaxial compressive strength (UCS), peak strain and elastic modulus. Finally, the effects of the frozen ratio on these properties were discussed. The results show that the pore water in sandstone shows three stages as the temperature decreases: stable liquid (from 25.0 to 0.0 °C), sharp phase transition (from 0.0 to − 2.5 °C) and slow phase transition (from − 2.5 to − 30.0 °C). Especially, the capillary and bulk water in sandstone is almost completely frozen in the sharp phase transition stage. As the temperature decreases, the frozen ratio first remains constant, then increases rapidly and finally increases slowly. Moreover, as the frozen ratio increases, the P-wave velocity, UCS and peak strain increase while the elastic modulus decreases. Interestingly, the compressive failure mode of sandstone changes from brittle to ductile as the frozen ratio increases.

Rock water use by apple trees affected by physical properties of the underlying weathered rock

Rock water use by apple trees affected by physical properties of the underlying weathered rock

Study on the Law of the Electric Folding Water Coefficient in Chayuo Middle Banner

In this paper, based on the investigation and research of groundwater types, topography and geomorphology, geological structure, stratigraphic lithology, groundwater richness and agricultural irrigation wells in the area of Chayou Middle Banner Inner Mongolia, a test area is selected and typical wells are determined. The estimating water consumption of typical wells was measured. Based on the calculation results, the distribution map of the Electricity-to-water conversion factor was drawn, and the influence of groundwater type on the Electricity-to-water conversion factor was analyzed. The results show that the type of groundwater has a significant impact on the number of electric water conversion factors, and the electric water conversion coefficients of fracture pore pressure water and groundwater in Neoproterozoic clastic rocks are relatively large; The electric water conversion coefficient of pore and fissure water pressure and groundwater in Neoproterozoic basalt ranks second; Quaternary loose rock pore water average; The bedrock fissure water is the smallest. At the same time, the influence of topography, atmospheric precipitation, and agricultural production on the Electricity-to-water conversion factor under the same type of groundwater was preliminarily investigated.

ON THE POSSIBILITY OF IMPLEMENTING CCS PROJECTS IN THE CARBONATE RESERVOIRS OF THE SIBERIAN PLATFORM

Link for citation: Nikitenkov A.N., Novikov D.A., Maksimova A.A., Penigin A.V., Varaksina I.V., Zhukovskaya E.A. On the possibility of implementing CCS projects in the carbonate reservoirs of the Siberian Platform. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 68-78. In Rus. The relevance. Carbon capture utilization and storage technology involving geological storage of carbon dioxide in deep aquifers is widely used in the world as this technology is aimed at decreasing the emission of greenhouse gases into the Earth’s atmosphere and minimizing the influence of these gases on the global climate change. Objective: to carry out preliminary investigation of the features of water – rock – carbon dioxide interactions in application to carbonate collectors, which are widespread in hydrogeological basins over the territory of the Russian Federation and are potentially suitable as carbon dioxide storage facilities. These processes are considered by the example of the ancient Siberian Platform, where industrial production of hydrocarbons is currently increasing, and a series of large-scale projects in the area of petroleum and gas chemistry are under implementation. Methods. Mathematical physical and chemical modeling was applied to solve the problem. The calculations were implemented by the HydroGeo software package, in which the achievement of chemical equilibria for the «water–rock» system is implemented on the basis of the method of equilibrium constants. Results. The obtained results allow us to evaluate the directions of geochemical processes in the collectors under consideration and to provide qualitative estimation of changes in the pore space under the conditions of its saturation with carbon dioxide, with respect to different saturation degrees. It is established that solution acidification is observed as a result of its saturation with СО2, with the transition of chemical elements to the prevailing forms of complex ions bound with hydrocarbonate and chloride ions (Mn, Na, K). At the same time, saturation with carbon dioxide does not have so substantial effect on the forms of Ca and Fe migration. Special attention is attracted to Al, which is transformed almost completely from complex forms into Al3+ in the presence of carbon dioxide. In the studied reference samples, rather intense transformation of collector rocks with redistribution of elements between the primary and secondary mineral phases is observed (both rock dissolution and precipitation up to several hundred g/dm3) with comparatively small absolute changes in open porosity. In a series of the considered objects, the dissolution of calcite and dolomite proceeds due to a decrease in pH. The directions of transformations, as well as the trend of changes in filtration-capacity properties, are determined by the specific mineralogical combination of collector rocks and the brine present in them, as well as by the stage of evolution of the system under consideration (the first part of the considered combinations is initially far from the equilibrium and continues interacting, while the second part is close to the equilibrium and is transformed into non-equilibrium state due to saturation with carbon dioxide).

Weathered bedrock converts hydrological processes in loess hilly-gully critical zone

Weathered bedrock ecohydrology is indispensable for terrestrial ecosystem stability; however, the influence on the hydrological processes is poorly understood in loess hilly-gully critical zone. Using simulation experiments and in-suit observations, this study evaluated the intervention of weathered bedrock particles on profile infiltration and evaporation, investigated rock core sample characteristics and detected the spatiotemporal water variation in hillslopes of woodland and shrubland. Results showed that adding weathered bedrock particles interfered with infiltration and evaporation processes. Infiltration simulation discovered that stable infiltration rates increased linearly with weathered bedrock thicknesses, which accelerated by 0.5–5.7 times more than bulk soil layers. Interestingly, due to water separation at soil-rock interface, there existed nonlinear initial and average infiltration intensity fluctuations. Evaporation simulation demonstrated that cumulative evaporation presented a linear decrease with weathered bedrock, while the initial daily evaporation intensity increased, reaching a maximum of 15.4 ± 2.2 mm d−1. Moreover, borehole investigations manifested that weathered bedrock layers presented a thickness of more than 5.0 m, and the weathering intensity gradually decreased with depth, which was related to terrains and locations in hillslopes. Furthermore, profile water movement monitoring between woodland and shrubland slopes demonstrated that weathered bedrock optimized profile hydrological allocation. The average rock moisture reached about twofold than soil moisture, with average soil and rock moisture of 0.07 ± 0.04 cm3 cm−3 and 0.15 ± 0.05 cm3 cm−3 in woodland, 0.08 ± 0.03 cm3 cm−3 and 0.15 ± 0.03 cm3 cm−3 in shrubland, respectively. Besides, the profile water storage changed dynamically in equilibrium and escalated linearly with weathering layer thickness. Fundamentally, a conceptual structure model covering soil and rock water balance, vegetation dynamics, and climate change was constructed and discussed throughout the Earth’s critical zone, which was then applied in describing water circulation participating by rock moisture under relative water shortage and abundance scenarios in loess hilly-gully regions. This study would furnish insights for improving and deepening the water cycle in shallow soils, and provide new horizons for enriching water resources utilization under climate change.

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.

Groundwater Quality Assessment for Drinking and Irrigation Purposes at Al-Jouf Area in KSA Using Artificial Neural Network, GIS, and Multivariate Statistical Techniques

Groundwater is an essential resource for drinking and agricultural purposes in the Al-Jouf region, Saudi Arabia. The main objective of this study is to assess groundwater quality for drinking and irrigation purposes in the Al-Jouf region. Physicochemical characteristics of groundwater were determined, including total dissolved solids (TDS), pH, electric conductivity (EC), hardness, and various anions and cations. The groundwater quality index (WQI) was calculated to determine the suitability of groundwater for drinking purposes. The EC, sodium percentage (Na+ %), magnesium hazard (MH), sodium adsorption ratio (SAR), potential salinity (PS), and Kelley’s ratio (KR) were assessed to evaluate the suitability of groundwater for irrigation. Effective statistical tests and Feed-forward neural network (FFNN) modeling were applied to reveal the correlation between parameters and predict WQI. The results indicated that approximately all samples are appropriate for drinking and irrigation uses except samples of the Al Qaryat region. The ionic abundance ranking was Na+ &gt; Ca2+ &gt; Mg2+ &gt; K+ for cations, and Cl− &gt; SO42− &gt; NO3− for anions. Moreover, the groundwater is dominated by alkali metals (K+ and Na+) and controlled by the rock–water interaction process. The indicators of groundwater quality for irrigation and drinking according to the following criteria (Na+ %, SAR, KR, MH, PS, WQI (WHO), and WQI (BIS)) can be predicted by the FFNN with root mean square errors (RMSE) of 0.136, 0.070, 0.022, 0.073, 2.45 × 10−3, 1.45 × 10−2, and 1.18 × 10−2, respectively, and R2 of 0.99, 1.00, 0.99, 0.99, 1.00, 1.00, and 1.00, respectively.

Study on Mechanical Behavior and Mechanism of Sandstone under the Coupling Effect of Water Content and Dynamic Load

In the process of underground engineering construction, rock mass often faces the dual influence of dynamic load disturbance and groundwater, it is therefore essential to investigate the mechanical response of the rock mass under the coupling effect of dynamic load disturbance and water content. In this paper, dynamic load impact tests were carried out on sandstone with bullet velocities of 5 m/s, 10 m/s, and 15 m/s and water content of 0, 0.3, 0.6, and 0.9, and the mechanical behavior and mechanism response of water content to sandstone were investigated. The research findings indicate that this study has made significant contributions in quantifying the along grain and trans-grain fractures of microcracks. It has explored the influence of water content and dynamic loading on the strength mechanism of sandstone. It was discovered that the dynamic loading and water content significantly affect the ratio of along grain and trans-grain fractures, thereby influencing the dynamic behavior of sandstone. The findings suggest a negative association between rock strength and water content and that its peak strength rises as the bullet velocity rises. The fracture characteristics of rock are influenced by water content and bullet velocity. The sample’s fracture degree increases with an increase in water content, its particle size distribution map is evident, and there is a positive relation between bullet velocity and fractal dimension. The energy conversion mechanism of the rock is influenced by the water content, as the bullet velocity increases, the absorbed energy density of the rock becomes higher. Furthermore, the correlation between the absorbed energy intensity and density and its fractal dimension is quantified. It is found that energy density and strength are positively correlated. The greater the fractal dimension, the higher the energy density absorbed.

Unveiling recharge sources and dominant processes for alluvial aquifers using hydrochemical and isotopic techniques

The study deals with the hydrochemistry (EC, DO, pH, HCO3–, SO2-4, Cl−, Ca2+, Mg+, Na+, and K+) and isotopic studies (18O, 2H, and 3H) of the groundwater of the Thal Doab, between River Indus and Jhelum, to delineate the sources of recharge and quality of groundwater. The groundwater based on isotopic data is recharged by two sources: the Indus River and rainfall shown by the depleted and enriched isotopic concentrations. The tritium concentrations revealed the short residence time of shallow groundwater as compared to the deeper groundwater. Furthermore, a deep groundwater upwelling zone has also been identified. Furthermore, it was found that the groundwater evolved in response to rock–water interaction, evaporation, precipitation, land use changes, and other anthropogenic activities. The groundwater system in the Chashma area is relatively safe for consumption. Future planning for the groundwater recharge zones should be the priority areas for protection, by the government water management and public health departments.

Physics-informed machine learning for understanding rock moisture dynamics in a sandstone cave

Abstract. Rock moisture, which is a hidden component of the terrestrial hydrological cycle, has received little attention. In this study, frequency domain reflectometry is used to monitor fluctuating rock water content (RWC) in a sandstone cave of the Yungang Grottoes, China. We identified two major cycles of rock moisture addition and depletion, one in summer affected by air vapour concentration and the other in winter caused by freezing–thawing. For the summer-time RWC, by using the long short-term memory (LSTM) network and the SHapley Additive exPlanations (SHAP) method, we find relative humidity, air temperature and wall temperature have contributions to rock moisture, and there is a good match between predicted and measured RWC using the three variables as model inputs. Moreover, by using summer-time vapour concentration and the difference between dew point temperature and wall temperature as input variables of the LSTM network, which belongs to physics-informed machine learning, the predicted RWC has a better agreement with the measured RWC, with increased Nash–Sutcliffe efficiency (NSE) and decreased mean absolute error (MAE) and root mean square error (RMSE). After identifying the causal factors of RWC fluctuations, we also identified the mechanism controlling the inter-day fluctuations of vapour condensation. The increased vapour concentration accompanying a precipitation event leads to transport of water vapour into rock pores, which is subsequently adsorbed onto the surface of rock pores and then condensed into liquid water. With the aid of the physics-informed deep learning model, this study increases understanding of sources of water in caves, which would contribute to future strategies of alleviating weathering in caves.

Sensitivity analysis for enhancing crude oil recovery with continuous flow gas lift: A study in reference to the porous media of the upper Assam basin, India

Despite minimal formation damage or water-cut, the majority of oil wells in brown oil fields cease to flow naturally. The current study looks into and analyses what caused a self-flowing well in the upper Assam basin to become non-flowing. The non-flow condition of the well was investigated in the current work as a function of water cut, reservoir pressure, reservoir rock permeability, and GOR. The effect of WHP and WHT on these functions was investigated. This work incorporates innovative methodology that uses the PROSPER simulation model for assessing the possibility of establishing flowability in a dead well based on inflow (IPR) and vertical lift performance (VLP). Subsequent analysis was carried out to examine the scope of producing this dead well under continuous flow gas lift. For this, the current work first examined the tubing diameter and reservoir temperature as standalone parameters to find out if they have any role to play in the flowability of the dead well. Following this, sensitivity analysis was done taking four parameters into account, i.e., reservoir pressure, reservoir rock permeability, water cut, and total GOR. In the current work, surface equipment correlation was established using Beggs and Brill correlation, while vertical lift performance was established using correlation from Petroleum Expert. The results of the current work highlight that a well's production rate under continuous flow gas lift can be enhanced by employing an optimised gas injection rate. The findings of this work conclude that higher reservoir pressure enables an oil well to produce with a high water cut under a continuous flow gas lift system, provided there are no formation damage issues on the well.

Coupling hydrogeochemistry and stable isotopes (δ2H, δ18O and δ13C) to identify factors affecting arsenic enrichment of surface water and groundwater in Precambrian sedimentary rocks, eastern salt range, Punjab, Pakistan.

The study area is a part of the Salt Range, where water quality is being deteriorated by natural and anthropogenic sources. This research integrates water quality assessment, arsenic enrichment, hydrogeochemical processes, groundwater recharge and carbon sources in aquifer. Total dissolved solid (TDS) contents in springs water, lake water and groundwater are in range of 681-847mg/L, 2460-5051mg/L and 513-7491mg/L, respectively. The higher concentrations of magnesium and calcium in water bodies next to sodium are because of carbonates, sulfates, halite and silicates dissolution. The average concentrations of ions in groundwater are in order of HCO3- > SO42- > Cl- > Na+ > Mg2+ > Ca2+ > K+ > NO3-, virtually analogous to springs water, but different from lake water, categorized as poor quality and unfit for drinking purposes. Based on major ions hydrochemistry, NaCl and mixed Ca-Mg-Cl type hydrochemical facies are associated with concentration of arsenic (4.2-39.5µg/L) in groundwater. Groundwater samples (70%) having arsenic concentration (11 ≤ As ≤ 39.5µg/L) exceeded from World Health Organization (WHO) guideline (As ≤ 10µg/L) in near neutral to slightly alkaline (6.7 ≤ pH ≤ 8.3), positive Eh(6 ≤ Eh ≤ 204mV), signifying its oxic condition. Eh-pH diagrams for arsenic and iron indicate that 80% of groundwater for arsenic and iron were in compartments of HAsO42- and Fe(OH)3, unveil oxic environment. Arsenic is moderately positive correlated with TDS, sodium, chloride, bicarbonate, nitrate, sulfate and weak negative with δ13CDIC in surface and groundwater, forecasting multiple sources of arsenic to aquifer. Stable isotopes of waters show recharge of groundwater from local rain and lake water. The lower δ13CDIC values of groundwater are modified by influx of CO2 produced during biological oxidation of soil natural organic matter.

Water and Geological Assessment in the Micro-Watersheds of the Alkaline Rocks of Tanguá and Soarinho in Rio de Janeiro State

Alkaline bodies of Tanguá and Soarinho in Rio de Janeiro present drainage areas that form the sources of the Soarinho and Caceribu Rivers. Due to its water and geological importance, we sought to investigate the relation between alkaline rocks and water bodies and the possible consequences of mining activity, as well as the use and occupation of land in water quality. Initially, the magnetometric profile was traced to confirm whether the locations selected for sample collection were located in the alkaline region. Then, water and sediment collections were carried out from the bed at three points on the Soarinho River and one point on the Caceribu River, all inserted in the drainages of the Soarinho and Tanguá alkaline massifs. Parameters necessary to calculate the Water Quality Index (WQI) and those related to contamination by mining activities were analyzed. Chemical analysis of the bed material sought to identify the deposition of contaminants. The context of alkaline rock interaction and water influence is confirmed through geophysical and lithogeochemical techniques through location maps and comparative results of bed material and direct samples of alkaline rocks that showed similar constitutions. In general, the WQI presented a median result, meeting the main requirements for appropriate water for conventional treatment aimed at public supply, and no indicators of contamination by mining activities were found, however, at point P3, representative of the headwaters of the Soarinho River, there were significant changes in BOD and fecal coliforms indicating direct discharge of domestic sewage in a nearby location. The results of the analyzes downstream of this point demonstrate the water bodies dilution capacity.

Study on the Damage Mechanism of Sandstone under Different Water Content States

Understanding the failure mechanisms of rocks that are exposed to different water contents is important for rock stability in rock engineering applications, and the quantitative analysis of rock behavior is necessary for predicting and preventing the occurrence of rock failure due to water effects. Mechanical tests using real-time acoustic emission (AE) technology were carried out to reveal the damage evolution in sandstone rocks in a dried state, natural state, and saturated state, which includes a quantitative analysis of AE characteristics and cracking properties. The testing results indicate that with the growth of water content, sandstone rocks show a decreasing trend in strength and tend to experience gentle damage with relatively fewer fractures. The crack morphology of the main fracture surfaces is quantitatively described, including a fractal dimension calculation and cracking length measurements. As the water content rises, when rock failure occurs, a higher AE b-value can be obtained, revealing an increasing proportion of large-scale cracks. The fractal dimension of the acoustic emission hit rate shows that the evolution of rock damage and deformation has self-similarity, that is, the transformation from order to disorder to order, and it is affected by different water contents. The AE waveforms of the sandstone have two dominant frequency bands (0~75 kHz and 75~150 kHz) no matter which water-bearing state they are in. The increase in rock water content has resulted in the decline of AE waveforms located in the range of 200–300 kHz, whereas the rise of AE waveforms is located in the range of 0–50 kHz. The findings of this study deepen our understanding of the mechanism behind rock failure and provide a meaningful reference for disaster assessment and control.

Molecular Simulation of Methane Adsorption in Deep Shale Nanopores: Effect of Rock Constituents and Water

The molecular models of nanopores for major rock constituents in deep shale were constructed. The microscopic adsorption behavior of methane was simulated by coupling the grand canonical Monte Carlo and Molecular Dynamics methods and the effect of rock constituents was discussed. Based on the illite and kerogen nanopore models, the discrepancies in microscopic water distribution characteristics were elucidated, the effects of water on methane adsorption and its underlying mechanisms were revealed, and the competitive adsorption characteristics between water and methane were elaborated. The results show a similar trend in the microscopic distribution of methane between different shale rock constituents. Illite and kerogen slit pores have no significant difference in methane adsorption capacity. The adsorption capacity per unit mass of kerogen is greater than that of illite due to the smaller molar mass of the kerogen skeleton and its large intermolecular porosity. Illite has a greater affinity for water than methane. With increasing water content, water molecules preferentially occupy the high-energy adsorption sites and then overspread the entire pore walls to form water adsorption layers. Methane molecules are adsorbed on the water layers, and methane adsorption has little effect on water adsorption. Kerogen is characterized as mix-wetting. Water molecules are preferentially adsorbed on polar functional groups and gather around to form water clusters. In kerogen with high water content, methane adsorption can facilitate water cluster fusion and suppress water spreading along pore walls. In addition to adsorption, some water molecules dissolve in the kerogen matrix.