Hydrochemical Processes Research Articles

Hydrogeochemical evaluation of groundwater and surface water interactions in an alluvial plain, Southeast Brazil

AbstractAlluvial plains are transition areas between terrestrial and aquatic environments where groundwater (GW) and surface water (SW) interactions occur. They are the subject of our present study, using hydrochemistry and environmental isotopes. Two water sampling campaigns in dry and wet seasons for studying physicochemical and natural isotope analysis provided 44 groundwater samples and watertable level measurements from monitoring wells and eight water samples from river, creek, and lake. In the dry season, lake and creek waters presented TDS (<3.64 mg L−1) and high values of TDS in groundwater and river (average 47.71 and 108.7 mg L−1, respectively), showing CaMgHCO3, NaHCO3, and NaHCO3Cl types and precipitation prevalence. However, GW–SW interaction occurred in CaMgCl and CaMgSO4 groundwater with TDS varying from 93.8 to 164.7 mg L−1 and weathering dominance close to riverbanks. The TDS, sulfate, and sodium were monitoring markers of this interaction. In the wet season, superficial waters and groundwater were more diluted, presenting CaMgHCO3, NaHCO3, and NaHCO3Cl types and precipitation dominance. Overall, the ion exchange was the main hydrochemical process. The δ18O, δ2H, and d‐excess indicated groundwater recharge with a weak evaporation process, rainwater mixture, and water–rock interaction. Maps of the distribution of ions, isotopes, and d‐excess showed GW–SW interaction along the riverbanks and depleted groundwater in a large portion of the alluvial plain. The alluvial plains are susceptible areas to precipitation changes due to fast and direct infiltration. Their monitoring can be essential to understand the climate variability and reduce impacts on the shallow aquifer that sustain forests and human life.

Self-organizing map improves understanding on the hydrochemical processes in aquifer systems

The holistic understanding of hydrochemical features is a crucial task for management and protection of water resources. However, it is challenging for a complex region, where multiple factors can cause hydrochemical changes in studied catchment. We collected 208 groundwater samples from such region in Kumamoto, southern Japan to explicitly characterize these processes by applying machine learning technique. The analyzed groundwater chemistry data like major cations and anions were fed to the self-organizing map (SOM) and the results were compared with classical classification approaches like Stiff diagram, standalone cluster analysis and score plots of principal component analysis (PCA). The SOM with integrated application of clustering divided the data into 11 clusters in this complex region. We confirmed that the results provide much greater details for the associated hydrochemical and contamination processes than the traditional approaches, which show quite good correspondence with the recent high resolution hydrological simulation model and aspects from geochemical modeling. However, the careful application of the SOM is necessary for obtaining accurate results. This study tested different normalization approaches for selecting the best SOM map and found that the topographic error (TE) was more important over the quantization error (QE). For instance, the lower QE obtained from min-max and log normalizations showed problems after clustering the SOM map, since the QE did not confirm the topological preservation. In contrast, the lowest TE obtained from Z-transformation data showed better spatial matching of the clusters with relevant hydrochemical characteristics. The results from this study clearly demonstrated that the SOM is a helpful approach for explicit understanding of the hydrochemical processes on reginal scale that may capably facilitate better groundwater resource management.

Study of hydrochemical and geochemical characteristics and solute fluxes in Upper Ganga Basin, India

Himalayan rivers are considered the most sensitive of all the ecosystems to the impact of climate change. In the present investigation, hydrochemical processes controlling the meltwater chemistry of the rivers Bhagirathi, Alaknanda and Ganga in the Upper Ganga Basin, India have been studied simultaneously creating a large database for the first time. For this purpose, an extensive water quality assessment in Upper Ganga Basin has been carried out by collecting water samples from all three rivers on monthly basis from September 2016 to May 2018 and analysing these samples for hydro-chemical parameters. Hydro-chemical characteristics revealed that sulphide oxidation and carbonation- the two proton producing reactions govern the chemical weathering processes pertaining in the rivers. One of the most peculiar findings of the study is the dominance of carbonate dissolution in the whole stretch of River Alaknanda, while the dominance of sulphide oxidation in River Bhagirathi upto Dabrani revealing the continuum of Gangotri glacial processes followed by carbonate dissolution upto Haridwar. The principal component analysis further supports this weathering process in the basin.

Controls on the behaviors of rare earth elements in acidic and alkaline thermal springs

Understanding the rare earth elements (REE) behaviors in aquatic environment is important to reveal the complex hydrochemical processes and hydrological circulation, such as water-rock interactions, mixing, redox reactions. Based on the samples collected from the Rehai geothermal field, southwestern China and the data from published literature, this study revealed that there are apparently differences in general hydrochemistry and REE geochemistry characteristics between the acidic and alkaline springs. The content of REE in acidic springs is one to three orders of magnitude higher than that of alkaline springs and river water. The NASC-normalized REE patterns of acidic springs are more similar to river water and volcanic rocks, but heavy rare earth elements (HREE) in all samples are enriched compared with volcanic rocks. Moreover, the most remarkable characteristic is that the total concentration of REE decreases significantly with the increase in pH of the springs, but rises slightly after water becomes neutral. Through speciation calculations, major REE species are Ln3+ and LnSO4+ in acidic springs (Ln represents REE), and REE hydroxide complexes are predominant in alkaline springs. The behaviors of REE in thermal springs are controlled by three processes: (i) the dissolution and alteration of primary minerals containing REE vary with the pH of water. The co-alteration of the whole-rock minerals contribute to the REE in the acidic springs, whereas the dissolution of feldspar is main source of REE in the alkaline springs; (ii) the content and species of Fe and Mn affects the adsorption, desorption and co-precipitation of REE, especially under weakly alkaline conditions; and (iii) inorganic complexation and adsorption are responsible for the fractionation between LREE and HREE. The positive Eu anomaly is mainly owing to preferential dissolution of feldspar in alkaline springs. Combined with the general hydrochemistry of thermal springs, isotopic data and inverse geochemical modeling, acidic springs in the Rehai geothermal field generate from oxidized shallow water heated by steam containing H2S, and alkaline springs are derived from deep geothermal water.

Hydrochemical Characteristics and Groundwater Quality Assessment Using an Integrated Approach of the PCA, SOM, and Fuzzy c-Means Clustering: A Case Study in the Northern Sichuan Basin

Groundwater is a precious resource that is vital for human life. Widespread human activities occur in the Sichuan basin due to befitting climate and geological conditions, inducing a series of groundwater contamination. In this article, hydrochemical analysis, principal component analysis (PCA), self-organizing map (SOM), and fuzzy c-means clustering (FCM) were integrated to reveal the hydrochemical process and assess groundwater quality in the northern part of the Sichuan Basin based on a collection of 203 groundwater samples. The groundwater hydrochemical types were dominated by the HCO3-Ca type. The PCA results show both natural and anthropogenic factors contributed to the hydrochemical compositions. The combination of the SOM and FCM classifies neurons into two categories: the first category where NO2− and NH4+ are most similar, perhaps as anthropogenic sources of pollution, which pose serious threats to human health; and the second category, where the total dissolved solids, Ca2+, Na+, Cl−, SO42, Mg2+, and K+ are most similar, explained as the influence of natural factors. The ion source was determined by water–rock interactions: Na+ mainly comes from the dissolution of silicate rocks, while Ca2+, Mg2+, and HCO3− from the dissolution of calcite and dolomite. Cation exchange was recognized in the water–rock interactions. The achievements would provide a significant reference for groundwater protection in the Sichuan Basin.

Mathematical model of surface water quality dynamics in river basin catchments

To conduct quantitative and qualitative assessment of activities in the catchment areas of river basins using a variety of principles and methods, multi-year systematic objectively hydrological, hydrogeochemical and economic information and analytical materials are needed.  At the same time, the scientific and theoretical value of surface water quality assessment of river basins is determined to some extent by the mathematical correctness of the tasks and methods of their solutions, which characterize the validity and reliability of hydrogeochemical processes of watershed areas of river basins, which dictates the need for structural analysis of complex hydrochemical indexes of surface water pollution assessment, based on natural laws, principles and properties of natural processes. The aim of the study is to develop mathematical models based on the genetic theory of hydrochemical processes of the natural system to assess activities in the watershed territories of river basins. In this paper developed mathematical models to improve the tools to assess the quality of surface waters of river basin catchments, based on the solution of differential equations of hydrochemical processes of natural systems, corresponding to the physical and mathematical sign of the practical problems of hydrochemistry and the principles of non-linearity of natural processes, are the result of using classical mathematical methods of modelling and their analytical analysis The proposed approach to the assessment of surface water quality in the catchment area of river basins in conjunction with geographical analysis can be used for comprehensive geo-ecological studies to develop recommendations for the rational management of water resources under anthropogenic activities.

Hydrogeochemical processes and groundwater quality of over-exploited Dupi Tila aquifer in Dhaka city, Bangladesh.

Dhaka is one of the highly populated cities in the world. Increased urbanization and population growth in Dhaka are mostly dependent on groundwater, with 78% of the supply water coming from the Plio-Pleistocene Dupi Tila aquifer. This research was conducted with the objectives of identifying ion chemistry, hydrochemical processes and their relationship to groundwater quality and finding out the impact of over-exploitation on Dupi Tila aquifer. Three consecutive semi-confined aquifers have been delineated up to the explored depth: the Upper Dupi Tila aquifer (UDA), Middle Dupi Tila aquifer (MDA) and Lower Dupi Tila aquifer (LDA). Hydrogeochemical processes and water quality have been inferred from bivariate plots, correlation of major ions, piper plot and stable isotopes analysis. The total dissolved solids show an increasing downwards trend from an average of 267mg/l in UDA to an average of 284mg/l in LDA. Waters in all three aquifers as well as surface water (SW) are mainly of Ca/Mg-HCO3 type. The weathering of aluminosilicates controls the concentration of the major ions. Even though there is a significant decline in piezometric level both in UDA (> -85m Public Works Department reference datum (PWD)) and MDA (> -65m PWD), there is no evidence of groundwater recharge through direct infiltration from the river. The stable isotopes indicate most of the UDA, MDA and LDA waters are mainly from local precipitation. Increasingly enriched mean values for stable isotopes for the subsequent aquifers UDA, MDA and LDA, as well as increasing PCO2 for UDA < MDA < LDA, indicate increasingly warmer recharge conditions. The overall groundwater quality in the aquifers is good. At present, we have no indication that groundwater exploitation has altered groundwater quality of the Dupi Tila aquifer. Therefore, it is of vital importance to regularly monitor water quality for the purposes in order to timely detect any potential water quality alteration that could be aggravated by the vast decline in piezometric level, in view of the long-term sustainable development of the groundwater resources of this city.

Groundwater Hydrochemical and Isotopic Evolution from High Atlas Jurassic Limestones to Errachidia Cretaceous Basin (Southeastern Morocco)

The objective of this research was to determine the recharge of the Cretaceous aquifers by the High Atlas, as well as the interaction and possible mixing phenomena between the waters of the different aquifers, by investigating the hydrochemical and isotopic evolution of groundwater flow paths from the limestone karst systems of the High Atlas to the Cretaceous basin of Errachidia. Geological techniques were used to investigate and confirm the chemical and isotopic characteristics of the waters. Although the Gibbs diagram shows that water–rock interaction is the dominant hydrochemical process, some water samples in the Cretaceous basin are influenced by both evaporation and water–rock interaction, indicating a mixture of rainfall and deep waters. A saturation index study indicated that limestone minerals were supersaturated in parts of the groundwater samples (calcite and dolomite). This result was confirmed by isotope data. Indeed, some Cretaceous basin samples show isotopic similarities to those from the Jurassic High Atlas. The geological cross-sections illustrate that the High Atlas Jurassic limestones are in direct contact with the Cretaceous basin’s permeable rocks, allowing groundwater to circulate from the High Atlas to Errachidia’s Cretaceous basin.

Impact of Flooding on Shallow Groundwater Chemistry in the Taklamakan Desert Hinterland: Remote Sensing Inversion and Geochemical Methods

Understanding the effect of flooding on groundwater quality is imperative for oasis vegetation protection and local ecological environment development. We used geochemical and remote sensing inversion methods to evaluate the effects of flood recharge on the groundwater hydrochemical and geochemical processes in the Daliyaboy Oasis. Groundwater samples were collected from 30 ecological observation wells in the study area before (PRF) and after (POF) the flood. Except for small changes in HCO3− and K+ and a decrease in pH, ion levels were higher POF than PRF, and the water chemistry was essentially unchanged. In the POF groundwater, HCO3− was correlated with Cl−, Na+, Mg2+, total soluble solids (TDS), and electrical conductivity (EC), but not with SO42−, Ca2+, K+, or pH, and was positively correlated with all other variables, while the remaining variables, except for pH, were strongly positively correlated with each other. PRF water chemistry was controlled by silicate and evaporite mineral weathering and evaporation processes, resulting in high groundwater TDS, EC, and a major ion content, while POF major groundwater ions were regulated by mineral weathering and flood recharge. We demonstrated the high accuracy of remote sensing inversion, confirming this as a reliable method for evaluating groundwater chemistry. The results of the study help to reshape and predict the history of the regional hydrogeological environment and hydrogeochemical development, and provide a theoretical basis for assessing the rational use of local water resources and protecting the ecological environment.

Impact of Climate Change on Hydrochemical Processes at Two High-Elevation Forested Watersheds in the Southern Appalachians, United States

Climate change increasingly affects primary productivity and biogeochemical cycles in forest ecosystems at local and global scales. To predict change in vegetation, soil, and hydrologic processes, we applied an integrated biogeochemical model Photosynthesis-EvapoTranspration and BioGeoChemistry (PnET-BGC) to two high-elevation forested watersheds in the southern Appalachians in the US under representative (or radiative) concentration pathway (RCP)4.5 and RCP8.5 scenarios. We investigated seasonal variability of the changes from current (1986–2015) to future climate scenarios (2071–2100) for important biogeochemical processes/states; identified change points for biogeochemical variables from 1931 to 2100 that indicate potential regime shifts; and compared the climate change impacts of a lower-elevation watershed (WS18) with a higher-elevation watershed (WS27) at the Coweeta Hydrologic Laboratory, North Carolina, United States. We find that gross primary productivity (GPP), net primary productivity (NPP), transpiration, nitrogen mineralization, and streamflow are projected to increase, while soil base saturation, and base cation concentration and ANC of streamwater are projected to decrease at the annual scale but with strong seasonal variability under a changing climate, showing the general trend of acidification of soil and streamwater despite an increase in primary productivity. The predicted changes show distinct contrasts between lower and higher elevations. Climate change is predicted to have larger impact on soil processes at the lower elevation watershed and on vegetation processes at the higher elevation watershed. We also detect five change points of the first principal component of 17 key biogeochemical variables simulated with PnET-BGC between 1931 and 2100, with the last change point projected to occur 20 years earlier under RCP8.5 (2059 at WS18 and WS27) than under RCP4.5 (2079 at WS18 and 2074 at WS27) at both watersheds. The change points occurred earlier at WS18 than at WS27 in the 1980s and 2010s but in the future are projected to occur earlier in WS27 (2074) than WS18 (2079) under RCP4.5, implying that changes in biogeochemical cycles in vegetation, soil, and streams may be accelerating at higher-elevation WS27.

Hydrogeochemistry and Isotope Hydrology of Surface Water and Groundwater in the Mountain Watersheds of Daqing River, North China

Surface water and groundwater interaction variations in time and space are crucial for effective water management, especially in low-precipitation regions. To comprehensively determine the hydrochemical characteristics and interaction processes of surface water and groundwater and to investigate the decreasing causes of water resources in semi-arid mountainous watersheds under changing environments, intensive field surveys were conducted in the Daqing River watershed, a tributary of the Haihe River basin in northern China, during two different times of the year: after the rainy season (September 2018) and before the rainy season (July 2019). Sixty surface water and groundwater samples were collected along the mountainous watershed. Using a combination method of hydrogen and oxygen stable isotope tracing and hydrochemical analysis, the hydrogen and oxygen isotopes and hydrochemical characteristics of surface water and groundwater in the mountainous watershed of the Daqing River were analyzed. Furthermore, the effect of elevation (altitude) on isotopes was discussed, and the correlation between hydrogen and oxygen isotope composition and hydrochemical characteristics was obtained. The results were processed using endmember mixing analysis to determine the amount of contribution of the surface water and groundwater interaction processes. The results show that the hydrochemical characteristics are relatively stable in the mountainous watersheds of the Daqing River, and the surface water and groundwater are mainly of the HCO3-Ca type. The slope of the local meteoric water line is smaller than the slope of the global meteoric water line, and the δD and δ18O in surface water and groundwater show a good linear relationship both before and after the rainy season. There is a decreasing trend of the value of δ18O in surface water samples with decreasing altitude, but a decreasing trend of the value of δ18O in groundwater samples is not obvious. The evaporation intensity of surface water is stronger after the rainy season than before the rainy season, and the connection between the surface water and the groundwater is stronger before the rainy season. Influenced by topographic conditions and other factors, the exchange of surface water and groundwater is frequent, and there is a large difference in the exchange ratio before and after the rainy season. The exchange ratio can be more than 50% after the rainy season. Thus, the reasons for decreasing water resources in the mountains can be implied to be due to the increasing hydraulic gradient between the mountains and the piedmont plains, and the water resources are discharged more in the form of groundwater to the downstream. The conclusions help to enhance the understanding of the water cycle in the mountainous watershed and can provide some theoretical basis for the sustainable development and utilization of water resources in the Haihe River basin and the regional water ecology of the Xiong’an New Area.

Combinations of multivariate statistical analysis and analytical hierarchical process for indexing surface water quality under arid conditions

Novel methods for water quality indexing increase insight into the fitness of water bodies for different uses. We hypothesized that integrating multivariate statistical analysis (MSA) with the analytical hierarchical process (AHP) may provide a reliable estimation of water quality status. Hence, twenty water samples from canals and drains in the northern Nile Delta, Egypt were collected during summer, autumn, winter, and spring and analyzed. Data were subjected to MSA, including correlation analysis, principal component analysis (PCA), and hierarchal cluster analysis (HCA). The AHP was applied to derive weights of parameters implied in developing water quality indices for irrigation (IWQI) and fish farming (FFWQI). Human health risks due to exposure to potentially toxic elements (PTEs) via dermal contact were also considered. The average concentrations of water constituents were acceptable for irrigation, except sodium adsorption ratio (SAR) and Cl−. The dissolved oxygen, total dissolved solids, Cl−, NO2-N, NO3-N, NH3, and PTEs (except Zn) did not meet standard limits for fish production. The MSA revealed that water contamination resulted from human activities (agriculture, industry, and domestic wastes) and hydrochemical processes. The PCA indicated that SAR, Cu, and pH could adequately represent water quality for irrigation, while temperature, NO2-N, Cr, and Zn could reflect fish farming requirements. The AHP provided consistent weights for the original and shortlisted parameters. The water quality varied from good to poor for irrigation and from excellent to low for fish farming. The minimum IWQI could adequately represent the IWQI (R2 = 0.83) and thus reduce the time, effort, and cost for monitoring water quality. However, the minimum FFWQI showed moderate consistency (R2 = 0.51) with FFWQI, implying that increasing the sampling size is essential for better performance. The hazard quotient of all PTEs was below 1.0 for both adults and children, indicating a safe limit. The potential cancer risk was acceptable (1.36E-06) for adults and safe (8.03E-07) for children. Results of this work would be a start point for efficient quality control programs in arid regions.

Extending classical geochemical weathering studies through the mountain block: The effect of increasing scale on geochemical evolution in the Sierra Nevada (CA)

The seminal studies of Feth et al. (1964) and Garrels and Mackenzie (1967) describe the chemical weathering processes controlling the geochemistry of spring waters in the Sierra Nevada (CA) and provide a framework for understanding geochemical weathering processes at local groundwater scales (i.e., short distances between recharge and subsequent groundwater discharge). Here, we extend these concepts to investigate the factors controlling geochemical evolution at the intermediate, mountain-block scale (i.e., increased flowpath length, circulation depth, and rock-water interaction). We accomplish this by applying a multi-tracer approach to mountain-front springs emerging along the Sierra Nevada frontal fault zone in Owens Valley, CA. These springs emerge at a significantly lower elevation (1100–2000 mamsl) than the eastern Sierra crest (4000+ mamsl) and provide a window into the hydrogeological and hydrochemical processes occurring within the mountain block from high-elevation mountain-block recharge to low-elevation mountain-front discharge, a recognized knowledge gap in hydrogeology. We delineate approximate spring contributing areas and identify geologic units likely sourcing springflow using stable isotopes of water and dissolved noble gases. We then classify four major geochemical groups after identifying the likely geologic units sourcing springflow and subsequent analysis and modeling of spring geochemistry. Our results lead to three main conclusions: 1) geochemical evolution within the mountain block from high elevation mountain block weathering to mountain front discharge follows power-law weathering relationships and becomes increasingly dependent on the dissolution of disseminated calcite present in plutonic rocks with increasing flowpath length, 2) geologic heterogeneity (i.e., differences in plutonic compositions and the presence/absence of Paleozoic metasedimentary roof pendants) exerts a dominant control on geochemical evolution with increased flowpath length, and 3) within geochemical groups, simple metrics like TDS or mole transfers from inverse geochemical models scale with physical and isotopic indicators of groundwater circulation and flowpath length.

Geochemical Characteristics of Rare Earth Elements in the Chaluo Hot Springs in Western Sichuan Province, China

High-temperature hydrothermal activity areas in western Sichuan Province, China are ideal objects for studying deep Earth science, extreme ecological environments, and comprehensive geothermal utilization. To understand the geochemical characteristics of rare Earth elements (REEs) in the Chaluo hot springs in western Sichuan Province, the authors analyzed the composition and fractionation of REEs in the hot springs through hydrochemical analysis, REE tests, and North American Shale Composite-normalized REE patterns. Moreover, the composition and complex species of REEs in the geothermal water in the Chaluo area were determined through calculation and simulation analysis using the Visual MINTEQ 3.0 software. The results are as follows. In terms of hydrochemical type, all geothermal water in the Chaluo area is of the Na-HCO3 type. The cations in the geothermal water are mainly controlled by water-rock interactions and evaporation, the anions are determined by water-rock interactions, and the hydrochemical processes are primarily controlled by the dissolution of silicate minerals. The total REE content of the geothermal water in the Chaluo hot springs is 0.306 ± 0.103 ug/L. It is low compared to the Kangding area and is primarily affected by the reductive dissolution of Fe oxides/hydroxides, followed by pH. The geothermal water in the Chaluo area is rich in light rare Earth elements (LREEs) because of the presence of Fe oxides. It shows positive Eu and Ce anomalies due to the combined effects of the dissolution of Eh and Mn oxides and surface water. Furthermore, the positive Eu anomalies are also caused by the water-rock interactions between the Qugasi Formation and deep geothermal water. Similar to alkaline water bodies, the complex species of REEs in the geothermal water mainly include Ln(CO3)2−, LnCO3+, and LnOH2+, which is caused by the stability constants of complexation reactions.

Hydrogeochemical Characteristics Refine the Conceptual Model of Groundwater Flow in Wood Buffalo National Park, Canada

Wood Buffalo National Park (WBNP), the largest national park of Canada, has unique and complex ecosystems that depend on specific water quantity and quality. We characterize groundwaters and surface waters in WBNP by determining their chemical compositions and water types, the dominant hydrochemical processes affecting their compositions, and their hydrochemical characteristics in relation to interpreted groundwater flow systems. Total Dissolved Solid concentrations in groundwaters and surface waters range from ≤10 mg/L to ≥300,000 mg/L. Four distinct water type groups are found: (1) Ca-SO4-type waters occur in multiple clusters across the area in outcrop areas of Devonian evaporites; (2) Na-Cl-type waters predominantly occur in the Salt plains region along the central eastern boundary, overlapping evaporite and carbonate-dominated bedrock formations; (3) Ca-HCO3-type waters dominate the Peace-Athabasca Delta-region in the south and most of the central region; and (4) “mixed” waters. Solutes in the waters originate from three main processes: dissolution of halite, dissolution of sulphate minerals, and dissolution of carbonates. The spatial occurrence of hydrochemical characteristics correlate with hypothesized groundwater flow systems, i.e., Ca-SO4 and Na-Cl-type waters coincide with discharge areas of intermediate to regional groundwater flow paths, and Ca-HCO3-type waters overlap with recharge areas. The findings of this study contribute to advancing knowledge on the hydrochemical characteristics of this remote and highly protected region of Alberta, Canada, and are important components of any further, comprehensive assessment of the natural water conditions.

Hydrochemical characteristics, hydrochemical processes and recharge sources of the geothermal systems in Lanzhou City, northwestern China

Lanzhou city has abundant geothermal resources in the sedimentary geothermal system. Based on water quality indicators from 9 geothermal water samples and 7 phreatic water samples, the hydrochemical properties of geothermal water were delineated and the hydrochemical processes and recharge sources of geothermal water were investigated. The principal component analysis (PCA) was used to determine the main physicochemical components of geothermal water and their influencing factors in the study area. Three principal components explaining 84.34% of the total variance were identified. The storage conditions and sources of geothermal water were analyzed using ionic ratios and isotopic analyses. The results demonstrated that geothermal waters are of Na-Cl and Na-SO4 facies, while the phreatic waters are of Na-SO4, Na-Cl, and Ca-HCO3 facies. Moreover, the halite and silicates dissolutions showed the greatest impact on geothermal and phreatic waters, respectively. On the other hand, the primary recharge source of geothermal water is ancient infiltration water, whereas the primary recharge source of phreatic water is a mixture of modern infiltration and geothermal waters. Although the geothermal water is stored in a relatively closed system, it may have a hydraulic connection with phreatic water through faults.

Spatial and Temporal Evolution of Groundwater Chemistry of Baotu Karst Water System at Northern China

Karst water quality degradation has been a challenge for domestic and industrial water supplies worldwide. To reveal the possible factors response for karst water quality degradation, Baotu karst spring system is studied as an representative example. In this study, a hydrogeochemical investigation and mathematical, statistical, and geochemical modeling was conducted together to identify the major hydrochemical processes involved in the degradation process. It is found that the karst water is normally fresh, neutral-to-slightly alkaline, with calcium and magnesium as the predominant cations, and bicarbonate and sulfate as the predominant anions. The abnormally high chloride (95.05 mg/L) and nitrate concentrations (148.4 mg/L) give clues to the potential source of contamination in some karst water. The main hydrochemical facies of karst water are HCO3-Ca and HCO3 × SO4-Ca, accounting for 76% of water samples. The water hydrochemistry is controlled mainly by the dissolution of carbonate minerals (calcite, dolomite), followed by the dissolution of silicate and gypsum. The dissolution of calcite and dolomite mostly happens in the recharge area. In the discharge area, the karst water is basically in equilibrium with calcite. The negative SI value of gypsum represents that the water–gypsum interaction is dominated by dissolution along the whole flow path. Cation exchange is observed in the karst water in the indirect recharge area. Along the flow path, the contents of chloride, sulfate, nitrate, and TDS (Total dissolved solids, abbreviated TDS, indicates how many milligrams of dissolved solids are dissolved in one liter of water) vary significantly, which is mostly affected by pollution from human industrial and agricultural activities. The concentrations of major ions were maintained at a low level (&lt;20 mg/L) in the 1960s in karst water. The fast elevation of the parameter values has occurred in the past two decades. The temporal elevation of some pollutants in karst water suggest that global changes (acid rain) and human activity (such as overusing fertilizer) are main factors resulting in the degradation of karst water quality in the study area. The results of this paper provide invaluable information for the management and protection of karst water resources in the urban and rural areas.

Separation of alumina from aluminum-rich coal fly ash using NaOH molten salt calcination and hydrochemical process

Separation of alumina from aluminum-rich coal fly ash using NaOH molten salt calcination and hydrochemical process

Paleoenvironmental Implications of Authigenic Magnesian Clay Formation Sequences in the Barra Velha Formation (Santos Basin, Brazil)

The characterization of Mg-clays in rock samples (well P1) from the Barra Velha Formation (Early Cretaceous) allowed the establishment of mineral assemblages on the basis of their kerolite and Mg-smectite (stevensite and saponite) content. Kerolite-rich assemblages (A and B) rarely contain saponite. Assemblage B is composed of kerolite-stevensite mixed layers, while assemblage A consists of more than 95% kerolite. Mg-smectite-rich assemblages (C and CB) are made up of both Mg-smectites. The predominance of stevensite in the lower interval of the stratigraphic succession suggests evaporative conditions, higher salinity and pH, which would favor its authigenesis by neoformation. In the upper portion, the occurrence of thick kerolite-rich intervals suggests regular water inputs, contributing with a decreasing in salinity and pH, favoring the neoformation of kerolite and later kerolite-stevensite mixed layering. The saponite would be the result of the transformation from Al-smectite into Mg-smectite in a Mg2+ rich medium. The results indicate that lake hydrochemical processes would have allowed the establishment of a basic depositional sequence, from base to top, as follows: (i) initial lake expansion stage marked by the occurrence of saponite, (ii) later kerolite neoformation, (iii) formation of kerolite-stevensite mixed layer with increasing salinity, and (iv) neoformation of stevensite, marking a final stage of maximum salinity (evaporation) and alkalinity of the lake.

Hydrochemical characterization and irrigation suitability of the Ganges Brahmaputra River System: review and assessment.

The hydrochemical characterization and irrigation suitability assessment of the Ganges-Brahmaputra River System (GBRS) has immense importance for the livelihoods of people and ecosystem sustainability in the region. This study aims to assess the hydrochemical characteristics and evaluate the irrigation suitability of water in the GBRS by reviewing published literature of the major tributaries. The studied rivers were categorized into two groups namely Group-1 and Group-2 considering the similarities of climatic patterns, hydrochemical attributes, and drainage characteristics. The hydrochemistry of the river water was characterized by the Piper diagram, Gibbs plot, mixing plots, and ionic ratios. Furthermore, irrigation water qualities were evaluated by electrical conductivity (EC), sodium percentage (Na%), sodium adsorption ratio (SAR), magnesium hazard (MH), and Wilcox diagram. The results indicated that the hydrochemistry of the GBRS was slightly alkaline to alkaline (7.42–8.78) in nature. The average concentrations of most of the chemical attributes showed higher in Group-1, whereas the average concentrations of K+ and NO3− were found higher in Group-2. The average concentration of the major ions followed the dominancy order Ca2+ > Mg2+ > Na+ > K+ for cations and HCO3− >SO42− > Cl− > NO3− for anions in both groups. Gibbs plot and mixing plot indicated that carbonate rock weathering dominates the hydrochemical process, which was further confirmed by the Piper diagram and the ionic ratios. From the analyses of irrigational water quality, almost all the rivers (except Gomti River in terms of MH and Rangit River in terms of Na%) in the GBRS were found to be suitable based on EC, SAR, Na%, MH, and Wilcox diagram. Finally, the majority of river systems in the GBRS were characterized by carbonate dominated lithology and irrigational water quality is mostly suitable for utilization. This study could be useful for water quality management in the glacial-fed Himalayan river under the context of global climate change.Electronic supplementary materialSupplementary material (Appendix 1) is available in the online version of this article at 10.1007/s11629-021-6834-z