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The Geochemistry of Natural Waters
... The occurrence of GGCs in groundwater (Fig. 1a,b; Supplementary Table 1) and their partitioning between the aqueous and solid (mineral) phases result from their chemical behaviour and transformation in the subsurface, which depend on equilibrium thermodynamics and reaction kinetics 38,39 . The elements As, Se and U are redox-sensitive and are commonly mobilized by microbially mediated oxidation and reduction of metal (Fe or Mn) (oxyhydr)oxides [40][41][42] . ...
... Orogenic belts, such as the Himalayas and the Cordillera, generate topography-induced basin divides that bound gravity-driven, regional-scale groundwater flow systems in major aquifers in foreland sedimentary basins 20,131 (Fig. 2a). Regional and local groundwater flow drives diverse geochemical processes, which induce the evolution of hydrogeochemical facies along flow paths 38,39 (Fig. 3). The consequent hydrogeochemical evolution exerts substantial control on scale-dependent reactive transport of GGCs 14,37,39,109,132 . ...
... Panel a adapted with permission from ref. 102, Elsevier.Regional recharge zones46,103,133 experience infiltration of O 2enriched meteoric water(Fig. 3)which becomes oxic groundwater with a positive E h and Ca 2+ , introduced from surficial or pedospheric sources38,39 . This oxic groundwater liberates oxyanions of As, Se and U, primarily by oxidative dissolution of the aquifer matrix, which is augmented by competitive anion exchange (NO 3 − , PO 4 3− ), as in the Chaco-Pampean plains of Argentina and the Huhhot basin of Inner Mongolia (China) ...
Geogenic groundwater contaminants (GGCs) affect drinking-water availability and safety, with up to 60% of groundwater sources in some regions contaminated by more than recommended concentrations. As a result, an estimated 300-500 million people are at risk of severe health impacts and premature mortality. In this Review, we discuss the sources, occurrences and cycling of arsenic, fluoride, selenium and uranium, which are GGCs with widespread distribution and/or high toxicity. The global distribution of GGCs is controlled by basin geology and tectonics, with GGC enrichment in both orogenic systems and cratonic basement rocks. This regional distribution is broadly influenced by climate, geomorphology and hydrogeochemical evolution along groundwater flow paths. GGC distribution is locally heterogeneous and affected by in situ lithology, groundwater flow and water-rock interactions. Local biogeochemical cycling also determines GGC concentrations, as arsenic, selenium and uranium mobilizations are strongly redox-dependent. Increasing groundwater extraction and land-use changes are likely to modify GGC distribution and extent, potentially exacerbating human exposure to GGCs, but the net impact of these activities is unknown. Integration of science, policy, community involvement programmes and technological interventions is needed to manage GGC-enriched groundwater and ensure equitable access to clean water. Sections
... Nevertheless-if there are no known point sources-the most practical and cost-effective response is usually to monitor for heavy metal contamination and respond appropriately if any is detected rather than launching into a modeling effort. For example, when the 2012 Reading Fire burned a portion of Lassen Volcanic National Park, CA, USA, the BAER hydrologists measured changes in the pH and ORP 67 of stream water, which raised the concern that the wildfire may have been hot enough to mobilize heavy metals from the volcanic materials (Drever, 1997), particularly arsenic (Murphy et al., 2020;Nordstrom et al., 2014). Out of an abundance of caution, they recommended testing above a nearby village's water intake after rain events through midwinter (Stewart and Wheelock, 2012). ...
... 67 Oxidation reduction potential (ORP) is measurable in the field but is often beyond the scope of routine investigations. It can be converted to pe, which when plotted against pH, can be compared to standard diagrams that give the phase and form in which an element's system will be found at various temperatures and pressures (Drever, 1997). ...
Abstract: Hydrologic modeling is an essential tool for analyzing the environmental effects of wildfires.
Simulations of watershed behavior are uniquely suited to emergency assessments in which data are
limited and time is scarce, such as those performed under the Burned Area Emergency Response
(BAER) Program used by Federal Land Management Agencies in the United States. In these
situations—when the values at risk (VARS) include lives and property—it is critical to remember:
“All models are wrong, but some are useful” (Box and Draper, 1987). However, all too often, neither
reports nor results rigorously reflect this imperative. With the wildfire crisis worsening each year,
improving the state of the practice can be a strategic force multiplier for agencies, NGOs, and
researchers alike.
Herein, the twin questions of how wrong and how useful are used as the foundation for an
overview of meaningful modeling within the context of postfire hydrologic assessments. Therefore,
this paper focuses on how to: (1) think about watershed modeling, (2) select a modeling strategy, and
(3) present the simulations in a meaningful way. The beginning and the end—the bread of a modeling
sandwich. Nearly a third of the content is about science communication.
While the focus is on burnt watersheds, BAER, and the US, the basic principles of modeling,
grappling with uncertainty, and science communication are universal—and often not taught in many
academic programs.
[This provisional version has not undergone use testing or formal review by theUS Forest Service and will continue to evolve until the agency officially releases it. However, it was included as chapter 9 of Wheelock S.J. (2024) Marscapes to Terrestrial Moonscapes: A Variety of Water Problems."
... Essas águas salinas são geralmente muito antigas, mas a idade pode variar de milhares a milhões de anos (Freeze and Cherry, 1979 Em mananciais subterrâneos profundos em bacias sedimentares e em alguns sistemas mais superficiais, as águas subterrâneas evolvem para um estágio de salmoura com o Clsendo o ânion dominante da solução. Entretanto, isto só ocorre no caso de contato das águas com formações minerais específicas, tais como a halita ou silvita (Drever, 1997). Em algumas bacias sedimentares profundas, estratos de sal podem ocorrer durante um período de evaporação intenso em regiões litorâneas restritas durante milhões de anos. ...
... Como exemplo, a Figura 4 apresenta a evolução das concentrações de cloretos com o tempo, onde se verifica uma nítida tendência de elevação dos valores de cloretos, que eram da ordem de 60 mg/L em 1993 e passou a valores superiores a 3000 a partir de 2002. É necessário, então, que sejam estabelecidas as condições de exploração na cidade, através da implementação da lei estadual de recursos hídricos, para que tal ascensão de sal não afete as demais captações.Figura 2.Mapeamento hidroquímico das águas subterrâneas de Maceió, utilizando dados de poços rasos (p < 100 m) no períodode 1996-1997.Figura 3. Caracterização hidroquímica das águas subterrâneas de Maceió, utilizando dados de poços profundos (P > 100 m) no período de 1996 -1997. (Fonte: Autor). ...
Uma investigação preliminar da qualidade das águas do aquífero de Maceió-AL foi conduzida através da avaliação dos resultados analíticos obtidos para um total de 1204 amostras de águas subterrâneas para um período de cerca de 20 anos. Esses dados foram coletados a partir de 322 poços tubulares da região com profundidades entre 50m e 250m. Foi utilizada a metodologia gráfica de Stiff para elaboração dos mapas hidroquímicos objetivando a detecção de tendências espaciais da qualidade da água. Os resultados indicaram que há uma predominância de águas do tipo cloretada magnesiana, seguida do tipo bicarbonatada magnesiana. As águas são, em geral, apropriadas ao consumo humano, onde são satisfeitos, na maioria dos casos, os critérios de potabilidade definidos pelas leis ambientais vigentes com base apenas nos dados físico-químicos fornecidos pela Companhia de Saneamento de Alagoas (CASAL). Vale lembrar, entretanto, que não há disponibilidade de dados para verificação da existência de compostos tóxicos como, por exemplo BTEX, PCBs e metais pesados nas águas subterrâneas de Maceió tendo em vista a inexistência de um programa específico de preservação e controle do uso dessas águas.
... Outside of those two measurements, samples with elevated SO 4 from the mining district generally had pH values that were relatively high compared to the low-SO 4 streams. This is the expected case for a watershed containing both high alkalinity (carbonatebuffered) and low alkalinity, DOC-rich streams (e.g., Drever, 1988). ...
... These waters, however, appear to have Ca concentrations that vary similarly across seasons similar to those in the low-SO 4 Floodwood River. A high-Mg SO 4 source may also be present in the lower SO 4 streams, but if so, it is being dominated by calcite dissolution and precipitation processes that commonly control calcium concentrations in surface waters (e.g., Drever, 1988). ...
he St. Louis River and its major tributaries were sampled upstream from Cloquet during periods of high, medium, and low flow between September 2007 and October 2008. Special emphasis was placed on measuring sulfate (SO4) and mercury (Hg) distributions as well as other chemical parameters that might help to determine whether SO4 releases from the Iron Range have an impact on Hg speciation in the St. Louis River. These included, but were not limited to, dissolved organic carbon (DOC), dissolved iron (Fe), and the isotopic ratios for sulfur and oxygen atoms in dissolved SO4 (34SSO4 and 18OSO4). Dissolved and particulate fractions of methyl mercury (MeHg), total mercury (THg), and bioavailable mercury (AHg) were additionally determined over a range of hydrologic conditions to identify primary source regions and transport mechanisms for Hg species.
... This indicates that the solubility of these minerals limits cation and anion concentrations in the studied water. In many aqueous systems, gypsum solubility may be the only limiting factor for SO4 concentration [57,58]. Figure 7c demonstrates that gypsum saturation indices increase from negative values at low SO4 concentrations to values that approximate zero Obtained results show that the dissolution of carbonates (dolomite, calcite), sulfates (gypsum, anhydrite, and barite), and silicates (plagioclases) plays an important role in forming the composition of the water in the Elbrus area (Figure 7). ...
... This indicates that the solubility of these minerals limits cation and anion concentrations in the studied water. In many aqueous systems, gypsum solubility may be the only limiting factor for SO 4 concentration [57,58]. Figure 7c demonstrates that gypsum saturation indices increase from negative values at low SO 4 concentrations to values that approximate zero with increasing concentrations of SO 4 . ...
The region surrounding the Elbrus volcano in the Great Caucasus is a popular tourist destination, home to native people and an area of the richest ore mineral resources. Based on the chemical composition of surface water, mineral, and groundwater in the Elbrus area, as well as statistical and thermodynamic calculations, waters with high concentrations of Mn, Cu, Zn, Mo, Ba, W, Pb, and As were identified, possible mineral phases that may lead to these metal concentrations in water were estimated, and risks to human health were assessed. Two main sources of surface water pollution have been identified: (1) water from tailings that are enriched due to oxidation of sulfide minerals is considered a source of As (181 µg/L) and Mo (2070 µg/L) pollution in the area of the Tyrnyauz W-Mo deposit; and (2) CO2-rich waters of deep horizons discharge on the earth surface with high concentrations of As (828 µg/L) and W (504 µg/L). It has been shown that compared to all toxic elements studied, only Mo and As have adverse non-carcinogenic effects on adult health. The estimated carcinogenic risk of As in the mine area was 1.7 × 10−3 and exceeded the generally accepted range of 10−4 to 10−6. In order to minimize the health risks, regular monitoring of water quality is required when mining activities on the Tyrnyauz W-Mo deposit are renewed.
... In mountainous regions, the springs water is an important source of freshwater and provide information regarding local and regional hydrogeological characteristics of karstic aquifers (Tran et al., 2023;Sheikh et al., 2023;Goldscheider et al., 2020;Stevanović, 2019;Zhang et al., 2020;Jeelani et al., 2017;Andreo et al., 2002). Furthermore, hydrogeological and hydro-chemical characteristics of karst aquifers were found to be considerably distinct than other aquifers (Terzić et al., 2012;Elçi and Polat, 2011;Ford and Williams, 2007;Drever, 1988;Langmuir, 1997). However, globally the studies on carbonate dominated aquifers are limited as compared to other rock formations (Zhang et al., 2023;Farid et al., 2015;Ma et al., 2011;Moral et al., 2008). ...
... The authors declare that no grants, funds, or other support were received during the preparation of the manuscript. Ali et al., 2023;Cao et al., 2020;Drever, 1988;;Langmuir, 1997;Milanovic, 1981;Parkhurst and Appelo, 2013;Piper, 1944;Rozanski et al., 1993;Stevanović, 2015. ...
Spring waters originates from carbonate aquifers provides substantial water for drinking and widely used for irrigation in Afghanistan. Thus, understanding hydrogeochemical evolution in carbonate dominated aquifer is important for sustainable groundwater resource management in the country. Therefore, in this study water from springs and dug wells from carbonate dominated aquifers were investigated to study hydrogeochemical evolution in Upper Shirin Tagab sub-basin, Northern Afghanistan. This study reveals that water in the area mainly belongs to Ca-Mg-HCO 3 facies type in Upper part and Mg-(Na, Ca)-SO 4-(HCO 3 , Cl) in the lower part. The hydrogeo-chemical processes in the aquifer were found to be governed by dissolution of carbonate, gypsum and halite minerals. Results shows that the chemical composition of springs is primarily controlled by local geology and water-rock interactions of limestone and dolomite with minor effects of silicate weathering. The δ 2 D-H 2 O and δ 18 O-H 2 O of springs water shows wide variations and found in the range of −64.4 ‰ to −52.6 ‰ and −10.1 ‰ to −8.6 ‰, respectively. Stable isotopes of water indicate that the water in the study area receive recharge from infiltration of recent precipitation and showing less evaporative enrichment of heavier isotopes. Overall, the quality of groundwater is safe for drinking with respect to WHO guidelines but the aquifer is suspectable to anthropogenic contamination such as sewage sludge, excessive nutrients, sulfate and pathogens. Furthermore, findings of this study will be helpful for decision makers to develop a sustainable water resource management in Shirin Tagab sub-basin in Northern Afghanistan.
... For this, the tendency of chemical forms between dissolved and inorganic phase was examined by the saturation index. This expresses the degree of chemical equilibrium between water and the inorganic matrix in the aquifer and can be considered as a measure of dissolution and/or precipitation in the of water-rock interaction [26,27]. The use of code PHREEQC [28], allows calculating the saturation indexes of carbonate minerals (aragonite, calcite, and dolomite) and evaporating minerals (anhydrite, gypsum, and halite). ...
... where IAP is the ion activity and K, the equilibrium constant. The SI minerals are used to evaluate the state of saturation of the water and controlling the chemistry and equilibrium with the solid phase [27]. ...
... For this, the tendency of chemical forms between dissolved and inorganic phase was examined by the saturation index. This expresses the degree of chemical equilibrium between water and the inorganic matrix in the aquifer and can be considered as a measure of dissolution and/or precipitation in the of water-rock interaction [26,27]. The use of code PHREEQC [28], allows calculating the saturation indexes of carbonate minerals (aragonite, calcite, and dolomite) and evaporating minerals (anhydrite, gypsum, and halite). ...
... where IAP is the ion activity and K, the equilibrium constant. The SI minerals are used to evaluate the state of saturation of the water and controlling the chemistry and equilibrium with the solid phase [27]. ...
Tel. +213 0 5 55 83 20 05, Tel./Fax: +213 33 86 97 24, Tel. +213 0 5 51 59 37 47, Tel./Fax: +213 33 86 97 24 A B S T R A C T This work aims to evaluate the hydrochemical characteristics of a shallow aquifer located between carbonated formations and salt lake in the Chemora region in northeastern Algeria. Hydrochemical, multivariate statistical, and the thermodynamics techniques were used to investigate the hydrochemical evolution within the aquifer. Twenty-five water samples were collected during May 2013 in this the aquifer wells. The results indicate that this shallow water is characterized by sulfate-dominant facies representing about 64% of cases, followed by the chloride with 24%, and the remaining (12%) is represented by the bicarbonate facies. The sulfate facies is acquired mainly by the alteration of pyrite. The saturation index showed that all carbonate minerals are supersaturated and all evaporate minerals are undersaturated which suggest that their soluble component Na + , Cl − , Ca 2+ , and SO 2À 4 concentrations are not limited by mineral equilibrium. The application of the cluster analysis and the principal components analysis based on major ion contents defined 3 main chemical water types reflecting different hydrochemical processes with salinity increases along the groundwater flow.
... Consequently, identifying different water masses and ongoing processes (salinization or freshening) represents a significant challenge to effectively managing groundwater in coastal aquifers. In this context, a thorough understanding of hydrogeological conditions, the distribution of saline groundwater, their origins and geochemical processes are essential in protecting groundwater resources from over-exploitation and pollution, which ultimately helps maintain stable socio-economic development of coastal regions (Drever, 1988;Appelo and Postma, 2004). ...
... Hydro-geochemical and statistical approaches are widely used to explore geochemical characteristics, contamination sources and salinization processes in coastal aquifers (Drever, 1988;Appelo and Postma, 2004;Sarker et al., 2021). Geochemical features like water type (Appelo and Postma, 2004) and ionic ratios (Stuyfzand, 2008) are commonly applied for identifying salinization/freshening processes. ...
In many coastal regions, groundwater is the sole freshwater resource for drinking and irrigation. However, coastal aquifers often face saline intrusion due to excessive groundwater extraction, climate change, and sea-level rise. This study integrated approaches in geochemistry, geophysics, statistical analysis, and geographic information system (GIS) to identify groundwater salinization pathways in the Ca Mau Peninsula of the Mekong Delta for sustainable protection of the invaluable freshwater resources. We collected 31 well logging data and groundwater samples from 388 wells in the area. A geochemical analysis demonstrated significant salinization in 9% of investigated wells. Calculated entropy-weighted water quality index (EQWI) indicates that only <3% of samples have excellent water quality and about 35% of medium-to-poor water quality groundwater. High salinity is the leading cause of impaired water quality. We combined geochemical and geophysical methods to validate an approach relating well-logging data (formation resistivity) to salinity to determine high-resolution vertical salinity profiles across the aquifer systems. We demonstrated the occurrence of saline groundwater in the surficial aquifers (Holocene and upper Pleistocene) that overlay above fresh and ancient groundwater aquifers (upper middle and lower Pleistocene, and Pliocene). This fresh groundwater is mostly fossil (age >10,000 years) and cannot be recharged directly from rainfall in the area while being highly susceptible to salinization by the downward movement of saline waters from overlaying aquifers. These findings call for appropriate strategies and directives in groundwater management to protect and sustain the critical water resources in the Mekong Delta.
... Soil texture and clay content are indicators of the speed and condition of the organic matter decomposition process (complete or incomplete), acting as key-elements for the storage or release of organic compounds in the marginal soils of the basin. Studies regarding DOC behavior in tropical forest soils [26,27] confirmed this distribution pattern. ...
... 1), establishing the equilibrium of the system (buffering system). According to Drever [27], such reactions control the pH of most aquatic systems, and when there is a significant variation in pH or oxygen partial pressure, calcium and magnesium ions can abruptly alternate their dissolved and precipitated volumes. This sudden oscillation was observed especially in the eastern northern region, in the areas of direct influence of the tidal zone. ...
A study on the typology of Amazonian waters was developed in the North Geographic Region of Brazil, considering a set of historical data from 1995 to 2022. The objective was to discuss and point out which environmental parameters are considered preponderant within the classification criteria of Amazonian waters. Historical data on temperature, density, pH, conductivity, oxygen, transparency, light attenuation, turbidity, color, total and dissolved solids, hardness, alkalinity, CaCO3, BOD, COD, main cations and anions, iron, C, N and P fractions, silicate, trace elements (Al, Cu, Zn and Mn) and chlorophyll a were analyzed. The analysis comprised water samples from the National Hydrometeorological Network (Sub-Basins 10 to 19), with a total of 36 basins, including tributaries, lakes and adjacent streams. The historical series was statistically analyzed through the techniques of Cluster, Principal component analysis (PCA), Piper Diagram and image interpolation by the ordinary kriging method. The results indicated a strong seasonal trend, with an evident distinction between the flood and ebb periods. The typology of white, black and clear waters was also evidenced, this last group being an intermediate class to the others, due to the physical-chemical standards. The PCA highlighted the parameters conductivity, pH, calcium, bicarbonate and Dissolved inorganic carbon (DIC) (Factor 1), and turbidity and alkalinity (Factor 2) as preponderant in the water classification. The ionic balance demonstrated that the white waters stood out for the highest concentrations of calcium and magnesium. The results suggest a pattern of calcic waters oscillating towards sodic and carbonated waters, with a subgroup in the northern eastern region of seasonally sodic-chlorinated waters, due to the influence of ocean tides. Image interpolation suggested a predominance of white waters in the western southern zone (Western Amazon) and white waters transitioning to clear waters in the eastern zone (Eastern Amazon). The analysis also showed a predominant strip of black and clear waters in the northern zone, and a strip of white waters in the central Amazon.
... For this the tendency of chemical forms between the dissolved phase and the inorganic phase was examined by the saturation index. This expresses the degree of chemical equilibrium between water and the inorganic matrix in the aquifer and can be considered a measure of the dissolution and / or precipitation in the study of water-rock interaction (Gibbs, 1970;Drever, 1997). The use of code PHREEQ-C, allows calculating the saturation indices of some carbonate and evaporating minerals (Parkhurst and Appelo, 1999). ...
... where IAP is the ion activity and K, the equilibrium constant. The SI minerals are used to evaluate the state of saturation of the water and controlling the chemistry and equilibrium with the solid phase (Drever, 1997). In general, the water-rock equilibrium is reached when SI = 0. ...
The intensive exploitation of groundwater resources in the region of Agmerouel-Roknia has greatly influenced the hydrochemical functioning of the superficial aquifer. This has resulted in a general decline of the piezometric level of the groundwater, a mineralization of water and calcium facies near Western limestone and sodium chloride in the East of the plain in liaison with the lithology. To highlight the hydrochemical processes of groundwater, a study by Major ions were analyzed for twenty two groundwater samples collected from this aquifer during the month of March 2013. Multivariate statistical techniques factor analysis and cluster analysis were applied to the data on groundwater quality, with the objective of defining the main controls on the hydrochemistry at the plain. These statistical techniques have shown the presence of two salinity groups increasing important according to the geology. The initial facies on the Western limits as well as infiltration areas is bicarbonate. In the East of the plain water becomes charged with Na and Cl in connection with the dissolution of salt formations. The presence of nitrates is related to agricultural activity. The major ion chemistry (Mg, Ca, HCO3 and SO4) in the three stations derived from the anthropogenic sources and the water-rock interaction.
... Magnesium ions in secondary minerals can be adsorbed on a mineral's surface/interlayer (i.e., exchangeable Mg), or tightly bound with oxygen in the crystal structure as impurities (i.e., structural Mg) (e.g., Drever, 1988). It has been suggested that, in most cases, isotopically heavy Mg is preferentially incorporated into the structural sites of secondary minerals, including clay minerals (e.g., Cai et al., 2022;Wimpenny et al., 2014), crystalline Fe/Al-oxides (e.g., Chapela Lara et al., 2017;Liu et al., 2014), and amorphous minerals (Ryu et al., 2021), whereas the adsorption of exchangeable Mg onto these minerals leads to little or no fractionation of Mg isotopes (Cai et al., 2022;Wimpenny et al., 2014). ...
... This can be understood because illite is an Mg-bearing clay mineral and typically contains high concentrations of structural Mg (2%-3% for MgO; Olphen, 1979). The Mg in illite, like in biotite, is primarily structural, while that in Mg-depleted clay minerals such as kaolinite is primarily adsorbed on surface and interlayer sites (Drever, 1988). The formation of illite thus results in the enrichment of heavy Mg isotopes in the regolith samples below −250 cm (Figures 6a and 6b). ...
Magnesium (Mg) isotopes have been utilized to constrain continental weathering; however, to date, little is known about the climate effects on Mg isotope fractionation during weathering. In this study, we measured δ²⁶Mg values of bulk regolith and exchangeable fraction in two granite regolith profiles developed under temperate, semiarid and tropical, humid climate conditions, respectively. Combined with mineralogy and element composition, we aimed to investigate how climate influences fractionation patterns of Mg isotopes during chemical weathering. At the temperate site, δ²⁶Mg values of regolith are slightly higher than that of the bedrock and negatively correlated with τMg,Th. Correspondingly, the exchangeable Mg is characterized by low δ²⁶Mg values. These results can be explained by the formation of small number of clay minerals. For the tropical regolith profile, δ²⁶Mg values decrease toward the surface, and the regolith has either lower δ²⁶Mg values above −250 cm or higher δ²⁶Mg values below −250 cm relative to the bedrock. The δ²⁶Mg value of exchangeable Mg is markedly lower than that of the regolith and varies significantly. These results can be explained by the mixing of Mg from solid weathering products and atmospheric deposition. The Mg from rainwater and/or marine aerosol deposit on the regolith and some may enter the crystal structure of the illite. The deposited Mg can overprint the granitic Mg, and the δ²⁶Mg value of shallow regolith samples will reflect mixing between granitic and atmospheric sources. The compilation of our and previously published Mg isotopic data reveals the potential control of climate on Mg isotope fractionation during continental weathering.
... They might have a longer residence time of the groundwater. The mineral stability diagram is another approach to test the proposed hydrochemical evolution of silicate minerals and their stability [44,45]. These diagrams are usually used to assess the degree of equilibrium and water-rock interaction [46,47] Figure 13. ...
... These diagrams are usually used to assess the degree of equilibrium and water-rock interaction [46,47] Figure 13. The stability fields for Ca-Plagioclase (anorthite) and its possible weathering products, gibbsite, kaolinite, and Ca-montmorillonite, as a function of log ([Ca 2+ ]/[H + ] 2 ) and log [H4SiO4] show that the kaolinite is more likely to be stable than, for example, gibbsite, as a result of an- The mineral stability diagram is another approach to test the proposed hydrochemical evolution of silicate minerals and their stability [44,45]. These diagrams are usually used to assess the degree of equilibrium and water-rock interaction [46,47]. ...
The complex and interconnected water challenges linked to global climate change and natural and anthropogenic water resources pressure have become major challenges in the 21st century. The Garonne River and its accompanying alluvial aquifers are considered the most important source for agricultural activities in the Garonne Valley, Nouvelle-Aquitaine Region, southwest France. The water is used for irrigation in summer and to reduce frost damage in spring. The alluvial shallow aquifer is recharged by rainfall, lateral inflow from the hillside, and seepage from the riverbed during the flood periods. The aquifer maintains the flow of the river during dry periods. Moreover, the potential recharge of this aquifer is particularly sensitive to annual climatic fluctuations and consequently affects surrounding ecosystems and related socioeconomic activities. The increasing impacts of climate change have increased the concern about the availability of these resources. Various adaptation strategies have been considered to mitigate and adapt to the new situation in southwest France. The artificial recharge of the alluvial aquifer is one such regional adaptation strategy to adapt to climate change. The study has two main objectives: to assess the natural and anthropogenic influence on the groundwater chemistry, and to model water infiltration, and understand the aquifer response and, consequently, the effects on river baseflow. The TAG (Technopole Agen-Garonne) project aims to increase the economic wealth of the region while respecting the region's agricultural traditions. Runoff water from the TAG zone is collected in retention basins and is a potential source to recharge the shallow alluvial aquifer. Sampling campaigns were carried out during the summer of 2019 to collect groundwater samples from several observation wells. Groundwater levels were measured in 132 wells/boreholes to determine the groundwater level fluctuations and create piezometric maps. Piper, spatial distribution, and ionic ratio plots were used to determine the dominant hydrochemical processes and to delineate the hydrochemical facies in the study area. The groundwater chemistry is controlled by silicate weathering and anthropogenic influence. Groundwater quality appears to be affected by the river water in the wells located in the low plain area. The measurements showed that the groundwater levels in the wells located near the river increase more than 2 m after a flood event. The artificial recharge has increased the groundwater level by more than 1 m close to the infiltration basin after a rainstorm. Similarly, a three-dimensional (3D) groundwater model shows a similar magnitude aquifer response to the induced infiltration. The modeling-obtained result shows that the infiltrated water would take about 4 months to reach the Garonne River, which is an appropriate time to maintain the river's low-flow and thermal buffering capacity, and thus the functioning of its ecosystems during dry periods.
... Geological formations and other activities by humans such as industrialization, agriculture activities and urbanization are factors that affect the divergence the quality of groundwater (Belkhiri et al., 2010;Darwish & Galal, 2020;Galal & Darwish, 2020). The type of rocks, climate, vegetation, relief, and time as environmental conditions affects the water chemistry (Drever, 1988). Recharge and discharge patterns, type of water-bearing sediments, and contaminated sources are factors that affect water quality is controlled by Ackah et al. (2011) and Sayyed and Wagh (2011). ...
... Furthermore, the salinity of groundwater, especially in shallow aquifers, has a considerable effect on water quality, especially in arid and semi-arid regions, leading to the phenomenon of evaporation (Drever, 1988;Güler & Thyne, 2004). The quality of groundwater changes when water seeps into the pores, joints, and fissures of the waterbearing sediments. ...
This study aims to assess water resources’ quality, biology, and suitability for different uses at some localities in the Dakhla Oasis in Egypt. Thirty-nine groundwater samples represent the Nubian Sandstone Aquifer with different depths, and 7 surface water samples represent wastewater lakes and canals. Major ions, total salinity, Na%, SAR, EC, RSC, PI, MH, KR, SSP, and Cl⁻ are used for the assessment of the water for different uses. It has been found that all groundwater samples of the study area are suitable for different purposes. Where the values of pH, major ions, TH, and TDS are below the permissible limit, this water is free of fecal coliforms. Based on the findings, the groundwater samples are generally suitable for drinking, with the exception of elevated levels of Fe²⁺ and Mn²⁺ concentrations that exceed the permissible limits. These elements can be treated to meet drinking water standards. The water samples from lakes and canals are not suitable for different purposes where these values are over the permissible limit and biologically contain fecal coliforms. According to the quality map, the groundwater in the area of study is excellent for drinking, livestock, and poultry and highly suitable for industrial purposes; and high to low suitable for irrigation purposes. However, lakes and canal water are not suitable for drinking, for livestock and poultry, industry, or for irrigation. The study reveals that there is a chance of an increase in total dissolved solids of wastewater in the lakes and canals which may pose a risk to soils in the study area. The present study recommends the necessity of finding a quick solution to the wastewater lakes which leads to the loss of large quantities of water and land due to salinization processes.
... The chemistry of water is determined as the results of various chemical variations of meteoric water in geological systems. Water quality is naturally influenced by geochemical compositions of the rocks along with various hydrodynamic factors [5][6][7][8] . Water resources play a vital role to continually increasing demands of agriculture, industry and domestic parts of India [9][10] . ...
... Dominance of bicarbonate is often attributed to the formation of carbonic acid in soil. Drever [39] describes the reaction of CO 2 in unsaturated zone with rainwater results in the production of bicarbonate. Reaction are as follows: ...
This study investigates the qualitative analysis of groundwater obtained from the Tonk district of Rajasthan to determine its suitability as potable water. Around 321 ground drinking water samples were collected and analysed for various physico-chemical characteristics including pH, electrical conductivity (EC), total dissolved solid (TDS), HCO3⁻, F⁻, Cl⁻, SO4²⁻, NO3⁻, Ca²⁺, Mg²⁺, total hardness (TH) and total alkalinity (TA) in Tonk district of Rajasthan (India). The groundwater in the region is a little alkaline and hard. The EC during the pre-monsoon period varies from 434 to 7271 µS/cm, while in the post-monsoon period, it ranges from 356 to 8871 µS/cm. TDS of samples ranged between 285 to 5090 mg/L in the pre-monsoon and 247 to 6140 mg/L post-monsoon seasons. Few samples have EC, TDS, and TH levels higher than the permissible limit, restricts its usage as drinking water. The water quality in the study area varies from soft-fresh to hard-brackish in both pre- and post-monsoon seasons. Anion concentrations in analysed samples followed the order: HCO3⁻ > Cl⁻ > SO4²⁻ > NO3⁻ > F⁻. Notably, the Water quality index (WQI) results for all collected samples fall within the range of 4.55–96.83, indicating they are considered safe and suitable for drinking purposes. Water quality data was analysed by correlation study and geochemical processes. A strong correlation between the Water Quality Index (WQI) and fluoride levels is found in both seasons. The geochemical analysis shows that most of the samples are in the rock water interaction zone, with some in the evaporation zone due to the high content of chloride ions. The groundwater chemistry appears to be influenced by rock-water interaction and evaporation sedimentation. The molar ratio of Ca²⁺/Mg²⁺ denotes calcite dissolution and silicate weathering revealing enrichment of Ca²⁺ and HCO3⁻ ions in aquifer.
... The average results (n=3) of physicochemical characteristics of torrent water are summarized in Table 1 and reveal varying nature of the torrent water. The difference in the quality of water may be due to some difference in the bed, different rechargeable zones and human activity [8]. The torrents T1, T2, T7, T9, and T10 are located in the area of relatively thin population density; the torrents T3 and T8 are located within medium intensity of population. ...
A field study was conducted to estimate the seasonal and regional variations in physicochemical characteristics of water of the hill torrents located in Azad Jammu & Kashmir where torrent water is used for drinking purposes. Ten torrents within the populated areas were selected and analyzed for about 30 parameters, including four major and seven minor metal contents. The monitoring was carried out for summer, autumn and winter during 2004-2005. Total dissolved solids (TDS) were observed within 145-561 µg/ml and 50 % of the torrent water crossed the limit of 500 µg/ml for TDS. For lead 80 %, for cadmium 90 % and for Kjeldahl nitrogen 40 % of studied torrents indicated higher values than the permissible limits of WHO for drinking water. No significant changes were observed in torrent water quality during different seasons.
... Hydrochemical Facies Evolution Diagram was employed (Fig. 4b) to validate the results (Drever, 1988;Appelo and Postma, 2004;Giménez-Forcada, 2014). The salinity intrusion phases are followed by the facies evolution trend 'i 1 ' (Ca-MixHCO 3 ); 'i 2 ' (MixCa-MixCl and Ca-MixCl) (Fig. 4b). ...
Contamination of coastal aquifers by seawater intrusion (SWI) is a major environmental problem. A modified GALDIT method (M-GALDIT), and multi-criteria decision model AHP has been used to identify regions vulnerable to seawater intrusion. We have used the groundwater suitability index for seawater intrusion (GQISWI) in estimating the M-GALDIT index. While the GALDIT analysis indicates that ∼28% of the area is moderately vulnerable, and 8% of the area is relatively highly vulnerable, our estimates using AHP and M-GALDIT method indicate ∼19% of the area as moderately vulnerable, ∼22% of the area as relatively highly vulnerable zones. The GQISWI values in the region vary between 0 and 96.96, indicating that most of the groundwater samples belong to mixed water types. Faults and fractures, population distribution, water-rock interaction, ionic exchange reactions, and evaporation appear to be the dominant mechanisms, besides seawater intrusion that control the overall groundwater geochemistry in the region. Ca2+-HCO3-, Ca2+-Na+-HCO3−, and Ca2+-Mg2+-Cl− are the most dominant water types in the study area. The seawater mixing index (SMI) reveals that ∼34.5% of samples are of relatively freshwater types, whereas ∼61% of samples appear contaminated to some extent, presumably due to the mixing of seawater, or anthropogenic activities such as mining, agricultural activities, etc. Furthermore, analysis of the HFE-D diagram indicates that ∼23% of samples are directly affected by seawater intrusion.
... The Sr/Ca molar ratio of parent dolomitizing fluid can be calculated from the equation (Sr/Ca)dolomite = D sr (Sr/Ca) fluid , where D sr is the distribution coefficient with a range from 0.05 to 0.06 for non-stoichiometric near-surface dolomites (Veizer, 1983;Vahrenkamp and Stewart, 1990;Banner, 1995;Budd, 1997). The elemental composition of the seawater did not change dramatically, particularly during the Phanerozoic (Veizer, 1983), and the calculated molar Sr/Ca ratios of D1 fluids (0.0035 ± 0.0009 and 0.003 ± 0.0008) are lower than that of our present-day seawater (0.0086; Veizer, 1983;Drever, 1988). This suggests a parent dolomitizing fluid composed of seawater that was possibly modified by mixing with other waters. ...
... The calculations are based on the relation between the ion activity product (IAP) and the constant of temperature equilibrium (KT): SI = log (IAP/KT). SIs specify the substances that might crystallize and the phases that could be dissolved in water [42,43]. ...
A hydrochemical and mineral study of groundwaters and damaged rocks from the Tíscar and Larva fault zones (Betic Cordillera, Iberian Peninsula) was carried out in order to (a) describe the physical and chemical properties of the groundwaters; (b) recognize significant locations with deep-origin fluids related to active tectonics; (c) and to describe the water–rock interaction and the neoformation of clay mineral processes and their importance in the seismicity of the faults. A sampling campaign was completed between November 2012 and November 2013, during which data were obtained from 23 different groundwater sites in the fault areas. Two main groups of waters were distinguished: (a) Ca2+-Mg2+-HCO3− facies characterized by poor conductivity and salinity; and (b) saline waters (up to 30 meq/L) rich in Ca2+-Mg2+-SO4-Cl− and with an elevated conductivity (frequently > 1000 μS/cm). In addition, a minor group of saline and warm waters (T > 16.5 °C) was found to be Na+-rich and show moderately high B values (>0.33 ppm), and which mig ht be hosted in aquifers deeper than the two main groups. This group of deep-origin waters is oversaturated in clay minerals and is in equilibrium for Ca-Mg carbonate minerals. X-ray diffraction and scanning and transmission electron microscopy data corroborate the crystallization forecast of authigenic smectite, which appears as thin films coating carbonate fragments. The origin of smectite is related to the fragile strain and thermal–fluid–mineral interactions in fault rocks. Smectite could lubricate carbonate rocks, which favor creep deformation versus seismic slip. This work provides locations where groundwater physico-chemical properties and composition suggest tectonic fault activity.
... The HCO 3 − concentration range was 18.69-293 mg/L, while that of CO 3 2− varied from below the detection limit (BDL) 0-150 mg/L. Natural sources of HCO 3 − include the dissolution of carbonate-containing minerals and the reaction of carbon dioxide (CO 2 ) with rainwater (Drever, 1988). Salinity levels in the groundwater were highest in the central regions and lowest in the southern regions, opposite to the predominant groundwater flow direction. ...
Identifying factors contributing to water salinity is paramount in efficiently managing limited water resources in arid environments. The primary objective of this study is to enhance understanding regarding the hydrochemistry, source, and mechanism of water salinity, as well as to assess the suitability of water for various uses in southern Iraq. The groundwater samples were collected from water wells and springs and analyzed for major cations and anions along with stable isotopes (δ¹⁸O and δ²H) to accomplish the objective. The analysis of major ion chemistry, hydrochemical techniques, principal component analysis (PCA), and isotope signatures were adopted to determine the primary factors contributing to water mineralization. The study inferred that evaporation and geological processes encompassing water–rock interactions, such as dissolution precipitation and ion exchange, were key processes. The stable isotope analysis revealed that the water originated from meteoric sources and underwent significant evaporation during or before infiltration. The utility assessment of water samples indicates that most samples are not appropriate for consumption and are significantly below the established standards for potable water. In contrast, a significant portion of the groundwater samples were found to meet the criteria for irrigation suitability by adopting Wilcox and the US Salinity Laboratory criteria. The groundwater could be considered for irrigation with proper salinity control management. Overall, this study has significantly improved the understanding of the hydrogeochemical regimes and acts as a first step toward the sustainable utilization of water resources.
... In the process of dissolution, highly soluble minerals dissolve first while less soluble salts remain in solid form. Consequently, after a dissolution-evaporation cycle, water contains ions derived from highly soluble salts (Drever, 1997). Therefore, it can be inferred that halite dissolution is the primary source of sodium and chloride in the lake. ...
Study region: Bakhtegan Lake, southern Iran, is a "Wetland of International Importance" (Ramsar Site). Study focus: This study focuses on analyzing the time series of the lake's inundation area, identifying factors contributing to its shrinkage, and studying its hydrochemical characteristics. To map the inundation area, Landsat images from 1972 to 2019 were used and 64 water samples were collected from the lake during 2017-2019 for geochemical modeling. New hydrological insights for the region: The study reveals that the Bakhtegan Lake has become a seasonal lake with a long-term dry state since 2007. The lake's inundation area shows a significant correlation with the Kor River discharge, and the main reason for the lake's shrinkage is a decrease in river inflow due to over-exploitation in the basin and construction of two new dams since 2007. The lake water and brine below the lake bed have TDS concentrations varying between 70000 and 451000 mg/L and 118000-373000 mg/L, respectively. The Gibbs, Na-normalized ratio end-member diagrams show that the lake water chemistry is mainly controlled by evaporation. The saturation index indicates that brine samples were in an equilibrium state with gypsum, halite, and glauberite. The Spencer diagram and evolutionary pathway model suggest that water samples shifted toward natural sulfate-rich minerals during evaporation. The lake water evolution model predicts precipitation of halite, kieserite, and carnallite minerals during progressive evaporation.
... The Fengcheng Formation in the Mahu Sag is a typical alkaline lake deposit in China, and its sedimen-tary-diagenetic environment evolution differs significantly from those of freshwater and non-alkaline saline lake deposits. Firstly, the original sedimentary environment is very alkaline (pH > 9), which can enhance the solubility of quartz [24] and the instability of silicate minerals (clay minerals) [25] . Quartz, clay minerals, and tuffaceous materials are prone to be dissolved or transformed in alkaline lakes, resulting in higher concentra- 100 tions of soluble silica and Al(OH)3 in the lake water [26] . ...
... Rare earth elements are thought to behave conservatively in low pH systems, and in the formation of iron oxides they are not preferentially scavenged or sorbed due to competitive binding of more favorable solutes, ligands, and/or metals (Verplanck et al. 2004). As with many other cations, REEs in an aqueous environment are in constant competition to form stable complexes or otherwise be incorporated in solid phases, which often requires the presence of inorganic ligands in mediating this partitioning (Stumm and Morgan 1988;Drever 1997. In alkaline systems, for example, carbonate plays a significant role in the cycling of REEs between free-ion, complexed, and colloidal forms (Quinn et al. 2006;Pourett et al. 2007). ...
The environmental impacts of acid rock drainage (ARD) and acid mine drainage (AMD) are a problem facing many waterways across the Rocky Mountains and throughout the world, particularly in areas of historic mining. Here we examine ARD/AMD enriched in rare earth elements (REE) in the Snake River watershed, located near the former mining boomtown of Montezuma, Colorado. Long-term data sets of precipitation, temperature, river discharge at many sites throughout the region show decreasing trends in summer flows from 1980 to 2010 which correlate to a snowpack melting occurring 2-3 weeks earlier. A 30-year water chemistry data set from the Upper Snake River further shows that metal concentrations are 100 to 400% higher than baseline concentrations during low-flow months. In addition, a low water table and decreased snow cover have increased the area of exposed sulfide minerals and the production of ARD, enhancing dissolution of metals from the disseminate pyrite present in the country rock and other secondary minerals present. The concentration of REEs present in tributaries of ARD- impacted Upper Snake and AMD-effected Peru Creek are three orders-of-magnitude higher than rivers worldwide and offer the unique opportunity to contrast their behavior against other dominant aspects of water chemistry. Iron is the predominant metal present both in the Upper Snake River and Peru Creek. In these headwaters, acidic water with pH 3.3 to 3.8 maintains a significant fraction of iron and aluminum dissolved, but mixing with shallow groundwater and pristine, circumneutral surface inflows downstream facilitate oxide precipitation. Of additional influence are diurnal changes in the valence state of dissolved iron coupled with the re-
iii
dissolution of precipitates owing to competing microbial and photochemical reactions. This study hypothesizes that headwaters loading of REEs are historically increasing at rates observed with other conservative solutes such as zinc. Similarly suggested and also related to alterations of hydrologic regime, are the enhanced enrichment of REEs by periods of extreme flow. In support, investigations for this thesis present data collected over the last 3 years regarding the sourcing, fate, and transport of rare earth elements as well as in relation to other solutes in the Snake River Watershed.
... In J o u r n a l P r e -p r o o f certain fields and industries, the barium salts, silicate and phosphate solids could also be discovered in the scaling layers (Chesters, 2009;Kelland, 2011;MacAdam and Parsons, 2004;Shakkthivel and Vasudevan, 2006). Among these components, calcium carbonate or calcite CaCO3 is one of the major components in the scaling layer (Drever, 1988;Keysar et al., 1994;Tang et al., 2008). Hence, it is reasonable to investigate the scaling mechanisms of calcium carbonate deposited on metallic surfaces as a representative. ...
... The maximum level of Fe in leachate samples suggested that Ironscraps are more likely to be dumped at the waste disposal sites (Aderemi et al., 2011). Seepage of Fe may occur from landfills, especially during the rainy season, contaminating the aquifer system (Drever, 1997). The dark brown colour of the leachate is due to the Fe oxidation reaction that involves converting ferrous to ferric and creating ferric hydroxide colloids and complexes along with humic substances (Chu et al., 1994). ...
... Saturation index (SI) can provide insights into water-rock interactions and enable the assessment of reactions between minerals and the aqueous solution. They serve as a qualitative indicator for the dissolution and precipitation of minerals in groundwater (Drever 1988), as illustrated in Fig. 5. The SI of the specific mineral can be computed using the following equation: Content courtesy of Springer Nature, terms of use apply. ...
High-fluoride groundwater is commonly found in coastal areas worldwide, while its formation mechanism remains elusive. Herein, a comprehensive study was performed to identify the major controlling factor of high-fluoride groundwater occurrence along the eastern coast of China. Hydrogeochemical methods were employed to examine the distribution patterns of seawater intrusion and fluoride concentration and the impact of seawater intrusion on the fluoride concentration. The results indicate that seawater intrusion significantly influences the groundwater evolution process in the study areas. The groundwater in Laizhou Bay was affected by brine, and the groundwater in Tianjin and Jiangsu was affected by seawater with a mixing ratio lower than 40% and 20%, respectively. And the fluoride concentration in groundwater from Tianjin, Laizhou Bay, and Jiangsu generally exceeded 1 mg/L, with the average of 2.3 mg/L, 24.9 mg/L, and 34.6 mg/L, respectively. Both the degree of seawater intrusion and the fluoride concentration exhibit a consistent pattern: Laizhou Bay > Tianjin > Jiangsu. Cl⁻ concentration in groundwater varies positively with the F⁻ concentration (y = 0.66x − 1.31). Moreover, the spatial distribution of areas with high-fluoride groundwater mirrors that of seawater intrusion. The high-fluoride groundwater varies spatially and is related to the degree, stage, and type of seawater intrusion. In other words, when seawater intrusion intensifies more or groundwater in the freshwater renewal phase with higher Na⁺/Ca²⁺ or the presence of paleo-seawater intrusion with higher fluoride concentration of brine, the concentration of fluoride in groundwater is higher. As seawater intrusion intensifies, the high-fluoride groundwater in the study areas generally poses a higher health risk to human. These findings enhance our comprehension of the mechanisms underpinning high-fluoride groundwater in coastal regions and the environmental ramifications of seawater intrusion.
... Examples include calcite, magnesite, dolomite, and ankerite (CaCO 3 , MgCO 3 , CaMg(CO 3 ) 2 , and CaFe(CO 3 ) 2 , respectively). Equation 8 represents the dominant dissolution reaction of calcite (CaCO 3 ) with iron-sulfide-generated acid (H + ) above pH 6.4, while equation 9 is the dominant reaction below pH 6.4 (Drever, 1988): ...
Environmental issues have become important, if not critical, factors in the success of proposed mining projects worldwide. In an ongoing and intense public debate about mining and its perceived environmental impacts, the mining industry points out that there are many examples of environmentally responsible mining currently being carried out (e.g., Todd and Struhsacker, 1997). The industry also emphasizes that the majority of mining-environmental problems facing society today are legacies from the past when environmental consequences of mining were poorly understood, not regulated, or viewed as secondary in importance to societal needs for the resources being extracted. On the other hand, environmental organizations (e.g., Mineral Policy Center, 1999) point to recent environmental problems, such as those stemming from open-pit gold mining at Summitville, Colorado, in the late 1980s (see Summitville summaries in Posey et al., 1995; Danielson and Alms, 1995; Williams, 1995; Plumlee, 1999), or those associated with a 1998 tailings dam collapse in Spain (van Geen and Chase, 1998), as an indication that environmental problems (whether accidental or resulting from inappropriate practices) can still occur in modern mining. Recent legislation imposing a moratorium on new mining in Wisconsin, and banning new mining in Montana using cyanide heap-leach extraction methods further underscore the seriousness of the debate and its implications for mineral resource extraction.
In this debate, one certainty exists: there will always be a need for mineral resources in developed and developing societies. Although recycling and substitution will help meet some of the worlds resource needs, mining will always be relied upon to meet the remaining needs. The challenge will be to continue to improve the ways in which mining is done so as to minimize its environmental effects.
The earth, engineering, and life sciences (which we group here under the term “earth-system sciences,” or ESS for short) provide an ample toolkit that can be drawn upon in the quest for environmentally friendly mineral resource development. The papers in this two-part volume provide many details on tools in the scientific toolkit, and how these tools can be used to better understand, anticipate, prevent, mitigate, and remediate the environmental effects of mining and mineral processing.
As with any toolkit, it is the professional’s responsibility to choose the tool(s) best suited to a specific job. By describing the tools now available, we do not mean to imply that all of these tools need even be considered at any given site, nor that
... Many researchers stated that ground water typically have large range of chemical composition in relation to the diversity of factors that influence their quality (Hem, 1970;Drever, 1982;Matthess, 1990;Apello and Postman, 1993). A group researchers in their paper concluded that the chemical composition of groundwater is strongly influenced by dissolutions from the soil zone; the processes that contribute to the concentration of major ions in the groundwater also depend on carbonate dissolution and precipitation, seawater intrusion, cation exchange, evaporative concentration of solutes and to a minor extent aluminosilicates dissolution (Kortatsi et al., 2007). ...
This study examined the concentration levels of physico-chemical profiles of groundwater quality of communities in Southern Ijaw Local Government Area of Bayelsa State, Nigeria. The seasonal variation of groundwater quality were evaluated. Fifteen (15) communities within the LGA were selected and groundwater from hand-dug well (HDW-15samples) and borehole (BH-15samples) was sourced during the wet season (July) and dry season (March) and analyzed for seasonal variations. The difference in the mean of the parameters investigated during the dry and wet season revealed the difference in concentration level as influenced by the season attributes. The HDW showed a very strong correlation in wet and dry season physicochemical properties as well as no significant difference in the physicochemical properties of groundwater at both seasons. Also, the results of borehole water sample showed a very strong correlation in wet and dry season physic-chemical properties with no significant difference in the physicochemical properties of water at both seasons. There are similarities in various natural and anthropogenic activities influencing the concentrations during both wet and dry seasons. The mean values of parameters such as pH, TDS, TSS, Bicarbonate, Cl, SO34, NO2, Ca, Mg, K and P are within the permissible limit of WHO and NSDWQ during both seasons except TC.
... The removal of solutes by AFH precipitation is an important process controlling the solubility of many metals (Drever 1982). Cations (e.g., Cd, Cu, Pb and Zn) in solution may subsequently be sorbed or coprecipitated with AFH at a solution pH of 5 or greater (Swallow et al. 1980, Dzombak and Morel 1990, Smith 1991, while anionic species [e.g., As, Cr(VI), Mo, Se] are strongly sorbed to AFH at pH < 7.5 (Leckie et al. 1980). ...
Mine permitting requires an analysis of reasonably forseeable impacts. In pit lake models, precipitates may be invoked which reduce dissolved aqueous concentrations, and thereby perceived groundwater impacts in the event of a throughflow pit lake after mine closure. The phases selected by modelers are generally based on geochemical theory rather than empirical data, and there is little information on the phases that actually precipitate in USA pit lakes. This paper focuses on the mineralogy of the former acidic Liberty pit pond mineral assemblage, predominantly amorphous ferric hydroxide and gypsum, while the former pH-neutral Cortez pit pond sediment contained barite, with biogenic calcite replacing the vascular cavities of horsetail with Ba, Mg, Mn and Zn in solid solution. Floc collected from the once-acidic, now pH neutral Lone Tree pit lake profile demonstrated trona dissolution with precipitation of an amorphous Fe, Al and Ca solid, with attendant As, Mn and Zn. Based on these data, appropriate authigenic precipitates in predictive pit lake studies should generally be constrained to amorphous, poorly crystalline solids, with reliance on exotic mineral phases appearing unwarranted.
... The groundwater can dissolve or precipitate minerals according to their saturation indices as they regulate the equilibrium between the aqueous solution and the host rock (Mohamed et al., 2015;Nosair et al., 2022;Redwan et al., 2016). The SI is a relation between the ions' activity product and the thermodynamics reaction constants (Clark & Fritz, 1997;Domenico, 1972;Domenico & Schwartz, 1997;Drever, 1997). The saturation index (SI) was calculated using the PHREEQC interactive code by applying the following equation (Parkhurst & Appelo, 2013): SI = log [ion activity product]/K T Where: K T is the equilibrium constant at temperature T. Both the semi-confined and the unconfined Quaternary, the Miocene, and the Nubian aquifer water samples show oversaturation with calcite and dolomite (Fig. 11 a and b), while they express an undersaturation with respect to gypsum and halite (Fig. 11 c and d). ...
... Despite a large number of studies on aluminium and silica concentration in seawater, the reports on solubility, kinematics of precipitation and adsorption of these elements are limited. The reported solubility limit of Al and silica for pH of 7-8 is log a SiO2 = − 2.7 (Drever 1988) and log a Al,total = -6.3 (Goldberg 1965;Klein and Bricker 1977). ...
Iron-rich rocks of Orosirian Period in the Chilpi Group on the northern margin of the Bastar Craton, Central India, contain an association of hematite-magnetite-greenalite-chamosite-quartz in oxide-silicate facies. Additionally chert (quartz) and siderite occur in chert and carbonate facies. Presence of these mineral assemblages was investigated to infer the redox state of the depositional basin. The results have indicated formation temperature variation of 116–255 °C (average 198 °C) and log P(O2) between – 37 and – 60 (average –44). A ferruginous state of the shallow water depositional environment, having oxygen content of 10–2 to 10–5 times the present atmospheric level, is inferred. The variations in composition of greenalite-chamosite association indicate development of the mineral phases from the reaction involving kaolinite-illite and magnetite-siderite as end-members. Thermodynamic requirements for the formation of the rare association of magnetite-greenalite-cronstedtite indicate the precipitation of the mineral phases from seawater with enhanced activities of Fe²⁺, Al, Si, Mg and C compared to the level in the present day seawater. The results indicate a steep fall in the atmospheric oxygen content immediately after the Great Oxidation Event of 2400–2000 Ma.
... As such, expanded euxinic conditions due to the stimulation of sulfate reducers ~2.4 Gya likely further limited the availability of Ni. By 0.55 Gya and to the present, the concentration of Ni in oceans has been ~9 nM (11). ...
Nickel (Ni) is a key component of the active site metallocofactors of numerous enzymes required for methanogenesis, including [NiFe]-hydrogenase, carbon monoxide dehydrogenase, and methyl CoM reductase, leading to a high demand for Ni among methanogens. However, methanogens often inhabit euxinic environments that favor the sequestration of nickel as metal-sulfide minerals, such as nickelian pyrite [(Ni,Fe)S 2 ], that have low solubilities and that are not considered bioavailable. Recently, however, several different model methanogens ( Methanosarcina barkeri , Methanococcus voltae , Methanococcus maripaludis ) were shown to reductively dissolve pyrite (FeS 2 ) and to utilize dissolution products to meet iron and sulfur biosynthetic demands. Here, using M. barkeri Fusaro, and laboratory-synthesized (Ni,Fe)S 2 that was physically isolated from cells using dialysis membranes, we show that trace nickel (<20 nM) abiotically solubilized from the mineral can support methanogenesis and limited growth, roughly fivefold less than the minimum concentration known to support methanogenesis. Furthermore, when provided direct contact with (Ni,Fe)S 2 , M. barkeri promoted the reductive dissolution of (Ni,Fe)S 2 and assimilated solubilized nickel, iron, and sulfur as its sole source of these elements. Cells that reductively dissolved (Ni,Fe)S 2 bioaccumulated approximately fourfold more nickel than those grown with soluble nickel and sulfide but had similar metabolic coupling efficiencies. While the mechanism for Ni uptake in archaeal methanogens is not known, homologs of the bacterial Nik uptake system were shown to be ubiquitous across methanogen genomes. Collectively, these observations indicate that (Ni,Fe)S 2 is bioavailable in anoxic environments and that methanogens can convert this mineral into nickel-, iron-, and sulfur-containing metalloenzymes to support methanogenesis and growth.
IMPORTANCE
Nickel is an essential metal, and its availability has changed dramatically over Earth history due to shifts in the predominant type of volcanism in the late Archean that limited its availability and an increase in euxinic conditions in the early Proterozoic that favored its precipitation as nickel sulfide minerals. Observations presented herein indicate that the methanogen, Methanosarcina barkeri , can acquire nickel at low concentration (<20 nM) from soluble and mineral sources. Furthermore, M. barkeri was shown to actively reduce nickelian pyrite; use dissolution products to meet their iron, sulfur, and nickel demands; and bioaccumulate nickel. These data help to explain how M. barkeri (and possibly other methanogens and anaerobes) can acquire nickel in contemporary and past anoxic or euxinic environments.
... The study of the interaction between the aqueous species (H 2 AsO 4 − ) and each different adsorbent under equilibrium conditions has to be assessed to establish adsorption mechanisms. Stumm and Morgan [63] and Drever [64] presented the mechanistic models for the adsorption of inorganic anions onto metal (Me) hydr(oxide) as a surface complexation model that is valid, among other things, for iron (hematite, goethite, and iron hydroxide) and aluminum (γ-alumina, gibbsite) minerals. For these solids, at pH values below pH PZC the speciation of the surface of the adsorbent is neutral (=Me-OH) and partially positively charged (=Me-OH 2 + ), and at pH values above pH PZC, it is neutral (=Me-OH) and partially negatively charged (=Me-O − ). ...
The role of precipitates from acid mine drainage (AMD) in arsenic removal in water is a process to be investigated in more detail. The present study is focused on the potential use of two AMD precipitates using oxidation and Ca(OH)2 (OxPFe1) or CaCO3 (OxPFe2) as As(V) adsorbents and the comparison of their performance with two commercial adsorbents (nanohematite and Bayoxide®). The AMD’s supernatants and precipitates were characterized using several techniques and assessed with theoretical speciation and mass balance methods. Gypsum was identified by XRD and assessed as the main component of the precipitates. Amorphous iron hydroxide was assessed as the second component (22% in mass), and jurbanite or aluminum hydroxide were present in the third likely phase. The equilibrium adsorption of As(V) in water at a pH between 4 and 6 was tested with the four adsorbents, and the Langmuir model correlated well. The maximum adsorption capacity (qmax) had the highest value for OxPFe1 and the lowest value for nanohematite (that could be explained in terms of the adsorbent surface speciation). The two precipitates have limited application to the adsorption of very low concentrations of arsenic because they have a binding constant (b) lower than the commercial adsorbents and could release a small amount of the arsenic contained in the precipitate.
... Banner, 1995), whereas m Sr and m Ca are the molar concentrations of Sr and Ca in dolomites, respectively. The calculated Sr/Ca molar concentrations (Appendix 1) for Md1 fluids range from 0.0075 to 0.0090 compared with 0.0086 of the present-day seawater (Drever, 1988). This may suggest that a parent dolomitizing fluid was composed of slightly evaporated seawater that was possibly modified by mixing with meteoric waters (e. g., Azmy et al., 2001;Azomani et al., 2013;Olanipekun et al., 2014;Hou et al., 2016;Shembilu et al., 2021;Luan et al., 2022). ...
... Generally, groundwater is greatly influenced by multiple natural and anthropogenic factors that govern groundwater quality, distribution, availability, and accessibility (Kresic, 2007). Naturally, groundwater quality in a region can be influenced by lithological composition, subsurface geological formations, types of aquifers, hydrogeochemical interactions between water and aquifers, depth of groundwater table, and other hydrometeorological factors such as rainfall, runoff, and presence of surface water bodies (Todd, 2003;Drever, 1982). These factors significantly influence groundwater quality due to geochemical interactions and the dissolution of numerous ions from the aquifer matrix to groundwater, making it a dilute electrolyte solution (McSween et al., 2009). ...
Spatio-temporal hydrogeochemical assessments of groundwater resources were carried out for the valley region of Manipur in India to investigate its quality status and suitability criteria for irrigational and potable uses. The assessment was carried out for 140 spatially distributed groundwater samples collected during 2018–2021 for pre- and post-monsoon seasons. To assess and comprehend the hydrogeochemical behavior of underlying aquifers and controlling factors for groundwater quality in the region, groundwater quality indices and statistical tools were used. Assessment of in situ parameters such as pH, TDS, salinity, and EC under feld conditions reveal that the values exceed concentration in many locations. Most of the samples fall in the category of hard to very hard water. Moreover, observation of both positive and negative oxidation–reduction potential (ORP) and low dissolved oxygen (DO) concentration in groundwater samples indicates aquifers are of recent unstable geologic formations. Similarly, elevated concentrations of F−, Cl−, HCO3
−, and Fe3+ greater than the prescribed standards of the World Health Organization in many samples indicate the unsuitability of the groundwater sources for potable uses. The geochemical interactions were found to be dominated and controlled by the rock-weathering geochemical process that contributes to HCO3
−-Ca2+-type water, followed by HCO3−-Na+, Cl−-Ca2+, and mixed type water in both seasons. Spatio-temporal geospatial vulnerable groundwater zone mapping using interpolation techniques carried out in the ArcGIS platform identifes the aquifers based on the water quality and pollution indices. The study’s signifcant fndings can provide baseline information that can supplement the government’s planning and management initiatives to deal with the current water security challenges in the region as groundwater uses are increasing due to various hydroclimatic phenomena in the state.
... Since the matrix composition of sea waters, in contrast to that of fresh waters, was stable [42][43][44], the influence of the main macro components of sea water, Na + , K + , Ca 2+ , Mg 2+ , Cl − , SO 4 2− , NO 3 − and PO 4 3− , on the AS Sn was studied. We also considered the influence of OTC on the direct ICP-spectrometric determination of tin without any sample pretreatment. ...
This paper considers the features of determining the total tin content in waters with different salinity. Direct ICP-spectrometric analysis of sea waters with a salinity of more than 6‰ significantly reduced the analytical signal of tin by 70% (ICP-MS) and 30% (ICP-OES). The matrix effect of macrocomponents was eliminated by generating hydrides using 0.50 M sodium borohydride and 0.10 M hydrochloric acid. The effect of transition metals on the formation of tin hydrides was eliminated by applying L-cysteine at a concentration of 0.75 g/L. The total analyte concentrations, considering the content of organotin compounds, were determined after microwave digestion of sample with oxidizing mixtures based on nitric acid. The generation of hydrides with the ICP-spectrometric determination of tin leveled the influence of the sea water matrix and reduced its detection limit from 0.50 up to 0.05 µg/L for all digestion schemes. The developed analysis scheme made it possible to determine the total content of inorganic and organic forms of tin in sea waters. The total content of tin was determined in the waters of the Azov and Black seas at the levels of 0.17 and 0.24 µg/L, respectively.
... A bicarbonate molecule is produced during the decomposition of organic matter in the soil due to root respiration and humus degradation, during which CO 2 is produced, which then reacts with precipitation to produce bicarbonate ions [41,42]. It was found that the bicarbonate level in groundwater was approximately 225 mg/l at SW5 in Merab Badawacho and 16 mg/l at SW2 at the Gemesha site, with an average of 96.61 mg/l among all groundwater samples collected in the area (Figure 7). ...
Groundwater is an important source of drinking water and irrigation in Ethiopia’s present study area of the upper Omo River catchment. The present study area has an increasing demand for high-quality groundwater. Extensive irrigation and urban expansion are ongoing in the study area, seriously compromising groundwater quality. A study was conducted in Ethiopia’s upper Omo River catchment to assess groundwater’s suitability for drinking water and agricultural purposes. In total, 58 water samples were collected for this study. Based on the WHO and Ethiopian standards for assessing water quality, the study’s results have been analyzed and compared. The groundwater’s primary ion and physicochemical properties were plotted using GIS technology. Based on the results of the hydrochemical analysis, three water quality index (WQI) zones were identified: excellent (58.82%), good (35.29%), and poor (5.88%). From the Piper diagram plots, five different types of water were identified as Ca-HCO3, Na-HCO3, mixed Ca-Na-HCO3, NaCl, and CaCl, out of the total of fifty-eight samples collected from the study area. The present study found that in the area, most water samples are suitable for drinking, except for a few parameters above the standards for drinking water set by the World Health Organization and Ethiopian drinking water quality standards. Except for the three samples, EC, SAR, and PI data indicate that most of the area’s water samples are suitable for irrigation. Water quality indices, irrigation water quality methods, and GIS techniques are crucial for assessing water quality based on the study.
... O nitrato (NO 3 ) representa o estágio final da oxidação da matéria orgânica. Trata-se de um composto muito móvel, mas ocorre em pequeno teor nas águas naturais, uma vez que este composto não pode ser encontrado na forma livre e tampouco advindo da dissolução dos minerais presentes nos solos ou rochas (DREVER, 1988;KEHEW, 2001). ...
No atual contexto do licenciamento ambiental, a legislação infraconstitucional específica sobre a proteção das cavidades naturais subterrâneas existentes no território nacional traz em sua atual flexibilização potenciais riscos associados aos aquíferos cársticos. Assim, o objetivo deste trabalho foi avaliar criticamente a promulgação do Decreto Federal nº 10.935, de 12 de janeiro de 2022, que ocorreu sem a participação da comunidade científica e espeleológica no processo de tomada de decisão política. Por meio de dados de análises químicas realizadas em águas provenientes de aquíferos cársticos no DF foi possível correlacionar a presença de efluentes contaminantes nas águas subterrâneas, devido a presença de atividades antrópicas na área estudada. Das 15 amostras de água subterrânea analisadas, 10 delas (67%) continham concentrações de elementos químicos provenientes de atividades antrópicas. A acidificação destas águas pela presença dos contaminantes eleva ainda mais seu poder corrosivo, aumentando a dissolução dos minerais carbonáticos formadores dos aquíferos cársticos, podendo ocasionar ainda efeitos sinérgicos e deletérios ao patrimônio natural e ao ecossistema cárstico.
... Since CO 2 causes various reactions, mineralizations take place at different temperatures. CO 2 -rich water facilitates Ca-Na exchange processes in feldspars and clay minerals (Drever, 1982). The high concentrations of HCO 3 − , K + , and Na + are produced by the hydrolysis reaction (chemical weathering) of dissolved carbon dioxide within the rocks (Pasvanoğlu, 2020) (Eq. 1) 2KAlSiO + 2CO + 3HO↔AlSiO(OH) +2K + + 2HCO − +4SiO (1) SKT-2020/1 and SAK-2020/3 samples are in the facies of Na-Cl waters. ...
This study based on the project titled "Examination of the Economic Potentials of the developed Basins Along the North Anatolian Fault System (NAFS) and East Anatolian Fault System (EAFS) with Remote Sensing and Geographic Information Systems (GIS) Methods" carried out by the General Directorate of Mineral Research and Exploration (MTA). The Sakarya (Adapazarı) Basin is controlled by the right lateral strike-slip North Anatolian Fault Zone (NAFS) which is one of the most active structures in Turkey. The Basin showing a different evolution mechanism from the pull-apart basins along the NAFS is represented by the sedimentation by the Sakarya River in the northern site towards the Black Sea. Moreover, the southern margin of the basin is shaped by the active faults. On the accounts of these factors, the geological significance of the basin for both geothermal and deformation features entirely focuses around the southern margin of the basin. In the study area, the Paleocene and Eocene aged limestones have abundantly broken, cracked and karstic cavity. The clayey-silty levels of the Plio-Quaternary sediments on the limestones showing the reservoir character are also cover rock.Chemical and isotopic compositions were determined by sampling from hot fluids produced from wells drilled in the Sakarya Basin and various cold-water sources. The electrical conductivity of cold and thermal waters varies between 199 and 7250 µS/cm. Temperatures of fluids taken from wells and springs are between 24 and 80° C. According to the classification of International Association of Hydrogeologists (IAH), Sakarya thermal waters are classified as boron-containing sodium, chlorinated, bicarbonate thermal and mineral waters and are deeply circulating fluids.The maturation index of Sapanca-Uzunkum and Akyazı waters is greater than 2. The cation geothermometers have been applied to these waters as well as silica geothermometers. The reservoir temperatures of these waters calculated by silica and cation geothermometers are 44-109oC and 34-99oC, respectively. These results can be attributed to the enrichment of oxygen isotopes in Akyazı and Sapanca-Uzunkum waters, their deep circulation and longer interaction with reservoir rocks.
Description
STP 1288 is the first publication of its kind featuring newly developed techniques and guidance for simulating water, air and contaminant movement in subsurface water resources.
Papers are presented in an order consistent with the procedures for conducting a model application, making this volume easy to use. A comprehensive glossary of ground-water modeling terminology is included.
24 peer-reviewed papers cover the following comprehensive topics:
Evaluation of Modeling -- Four papers explore a full range of concerns from the difficulty of ground-water modeling, to recommendations for future standards rectification and model codes for general use.
Conceptualization -- Successful problem solving techniques for subsurface flow problems in various hydrologic and geologic settings are explored in four papers.
Code Selection/Validation -- Four papers address alternative model codes and how to best fit objectives with the conceptual model chosen.
Model Design and Construction -- The diversity of codes and applications, and how best to establish the model grid, boundary conditions and conduct sufficient simulations are addressed in six papers.
Calibration -- Two papers examine how to adjust uncertain model input parameters to account for the difference between measured versus observed input.
Application Verification/Uncertainty -- Innovative techniques for verifying differing model applications are discussed in three papers.
Post Audit -- An extensive paper examines how the investigation of one site resulted in design remediation.
The present study focuses on the hydrogeological system of the Batha basin (Chad). This area is symptomatic of the functioning of an endoreic basin in an arid to semi-arid climate, of its water storage capacity related with the climatic fluctuations, and of the problems associated with assessing resources in this Sahelian zone. This basin forms the eastern part of the Lake Chad basin, which extends over 2.38 Mkm². It is a vast sedimentary basin, filled by detrital and fluvial-lacustrine deposits of Eocene (Continental Terminal) to Quaternary age, and bordered by Precambrian crystalline formations. The study aims to assess the aquifer potential of the groundwater system and its dynamics using a combined geology-hydrogeology-hydrochemistry approach. The lithology defined an heterogeneous and multi-layered system. The piezometric map reveals the dynamics of the general groundwater flow direction SE-NW, suggesting the interconnection of the different parts of the aquifer system. Based on the concentrations of major ions in solution, the hydrochemical results have identified four main types of facies: calcium bicarbonate (dominant), sodium bicarbonate, sulphate-sodium and mixed. The mineralization of these facies appears to be essentially controlled by water-rock interaction and to a lesser extent by base exchange and evaporation process. Calculations of saturation indices indicate that these waters are close to equilibrium with the calcite-Mg phases, gaylussite and gypsum. Nevertheless, given the low and medium ionic contents, it appears that the groundwater in the Batha basin is moderately evolved. On the other hand, stable isotope analyses (δ²H and δ¹⁸O) of groundwaters show the existence of three compositional groups corresponding to: (A) ancient water disconnected from current meteoric influences, (B) mixtures of current meteoric water and older water affected by evaporation during infiltration, (C) mixtures of current and ancient meteoric water more impacted by the evaporation process. In addition, tritium (³H) analysis of these waters shows the existence of three composition groups corresponding to current rainwater, modern water and post-modern water. Taken together, these results show that the hydrogeochemical differentiations obtained from both ionic and isotopic analyses cannot be strictly associated with the different aquifers (Quaternary, Pliocene, CT and basement). This confirms the interconnection of the Batha system and suggests that the heterogeneity observed is mostly controlled by lithological and climatic variations.
Silver (Ag) isotopes have the potential to provide useful insights into a diverse range of geological, environmental, and archaeological processes. This manuscript presents a novel technique that provides a simple,...
In the Tano River Basin, groundwater serves as a crucial resource; however, its quantity and quality with regard to trace elements and microbiological loadings remain poorly understood due to the lack of groundwater logs and limited water research. This study presents a comprehensive analysis of the Tano River Basin, focusing on three key objectives. First, it investigated the aquifer hydraulic parameters and the results showed significant spatial variations in borehole depths, yields, transmissivity, hydraulic conductivity, and specific capacity. Deeper boreholes were concentrated in the northeastern and southeastern zones, while geological formations, particularly the Apollonian Formation, exhibit a strong influence on borehole yields. The study identified areas with high transmissivity and hydraulic conductivity in the southern and eastern regions, suggesting good groundwater availability and suitability for sustainable water supply. Secondly, the research investigated the groundwater quality and observed that the majority of borehole samples fall within WHO (Guidelines for Drinking-water Quality, Environmental Health Criteria, Geneva, 2011, 2017. http://www.who.int) limit. However, some samples have pH levels below the standards, although the groundwater generally qualifies as freshwater. The study further explores hydrochemical facies and health risk assessment, highlighting the dominance of Ca–HCO3 water type. Trace element analysis reveals minimal health risks from most elements, with chromium (Cr) as the primary contributor to chronic health risk. Overall, this study has provided a key insights into the Tano River Basin’s hydrogeology and associated health risks. The outcome of this research has contributed to the broader understanding of hydrogeological dynamics and the importance of managing groundwater resources sustainably in complex geological environments.
Changes in sea-level are linked to glacial-interglacial variability and have been claimed as the main factor controlling the production of carbonate platform factories. The Maldives archipelago (Indian Ocean), composed of two rows of atolls that enclose an inner sea, is a very sensitive region to sea-level changes. The sediments of the Inner Sea, offer an excellent study site to explore the impact of sea-level changes on carbonate platforms. Elemental geochemical composition records, obtained by X-ray fluorescence (XRF) core-scanning, from the Maldives Inner Sea (IODP Site U1467), have been used in this work to evaluate the influence of orbitally-driven sea-level fluctuations on the carbonate production and export from the neritic environment into the Maldives Inner Sea over the last 1.3 million years. High Sr aragonite-rich carbonates (HSAC) from neritic settings are deposited in the Maldives Inner Sea during sea-level highstand intervals, increasing the values of the Sr/Ca ratio. In contrast, during sea-level lowstand periods large areas of the atolls were exposed or unable to grow and the demise in the carbonate production and sediment export is reflected as low Sr/Ca values in the Inner Sea. However, we propose that sea level is not the only factor controlling the production of HSAC during sea-level highstands since several interglacial periods before and after the Mid-Brunhes event (MBE, ~430 ka) indicate high carbonate production (high Sr/Ca). The intensity of the summer monsoon and the Indian Ocean Dipole probably modulated the production at the atolls. Marine Isotope Stage 11 stands out as a period with high sea-level and rather high carbonate production in the Maldives platform. This extraordinary carbonate production in the Maldives atolls (and in other low latitude carbonate platforms) probably contributed to the Mid-Brunhes dissolution event through a strong shelf-to-basin fractionation of carbonate deposition.
Nitrate (NO3−) pollution in karst areas has been widely discussed, which affects human health and the ecological environment. To investigate nitrate sources and their perturbations on cave hydrogeochemistry in karst cave systems, this study was conducted in Mahuang Cave, a karst cave in Southwest China, to assess the impact of human activities on the karst carbon cycle and the environment. The results show that (1) the variations of the water-soluble ions in Mahuang Cave are mainly controlled by carbonate weathering, and the cave water chemistry is characterized as the HCO3–Ca–Mg and HCO3–SO4–Ca–Mg types. (2) The dual isotopes and stable isotope Bayesian mixing model (SIAR) show that chemical fertilizers (41.5%) and soil nitrogen (33.75%) are the main nitrate sources in the cave water bodies, followed by manure and sewage (17.25%) and atmospheric precipitation (7.5%). (3) The significant enrichment of dissolved inorganic carbon isotope (δ13CDIC) in Mahuang Cave reveals that nitric acid produced by nitrification accelerates carbonate weathering in Mahuang Cave, and the carbon source effect of the carbon cycle in the cave is enhanced. Consequently, the response of cave drips and sediments to external environments is disturbed.
E veniamo ora al 2022. Un anno, per tanti accadimenti extraspeleologici nel mondo con-temporaneo, attraversato da tragedie epocali e laceranti che mai avremmo pensato di essere costretti a vivere; per contro, sotto certi aspetti (quasi) post-pandemici, dopo la funesta parentesi più che biennale del Covid, di parziale rinascita anche per la Speleologia. Con ritardo di due anni, ha infatti potuto svolgersi a Ormea il 23° Congresso Nazionale. Anche noi c'eravamo. Eravamo presenti, a riprova che, all'età di novant'anni suonati, il Gruppo è più che mai attivo e non ha perso smalto e capacità sempre rinnovata di perse-guire con successo interessi scientifici ed esplorativi. È in omaggio a questa realtà confortante che pubblichiamo ora di seguito integralmente le due nostre comunicazioni al Congresso, unitamente a una terza frutto di una ricerca in collaborazione, augurandoci che il filo virtuoso che ha caratterizzato in questi decenni la nostra presenza attiva nell'ambito della speleologia nazionale non sia destinato a interrom-persi negli anni che ci separano dal centenario della fondazione e per molto tempo ancora. Riassunto Viene preso in esame, in Provincia della Spezia, il sistema idrogeologico correlato alla risorgente di Cassana (Li-SP 1041), alla grotta del Ginepro (Li-SP 66), all'Inghiottitoio del canale di Faggiona (Li-SP 1867), alla risorgenza sul torrente Redarena (Li-SP 175) ed alla sorgente carsica sul torrente Casale. Sulla base dei dati geo-speleologici, Idrogeologici e geochimici raccolti ed alla luce delle recenti ricerche nella zona della miniera di Cerchiara (Faggiona), viene formulata l'ipotesi dell'esistenza di un unico sistema carsico attivo localizzato nei comuni di Borghetto Vara e Pignone e viene presentata un'ipotesi di modello concettuale dell'acquifero.
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