Na-Cl Water Type Research Articles

Monitoring soil salinization and waterlogging in the northeastern Nile Delta linked to shallow saline groundwater and irrigation water quality

Soil salinization and waterlogging are critical environmental issues affecting agricultural productivity and cultural heritage preservation, particularly in arid regions. This study investigated soil degradation processes in the archaeologically and agriculturally significant northeastern Nile Delta of Egypt. The objective was to assess the severity of soil degradation and identify key drivers related to water resources and soil characteristics to aid in the development of management strategies. The research employed a multi-faceted approach, including hydrochemical analyses (of groundwater, irrigation water, and soil), water quality indices calculations, statistical analyses, and satellite data. The results revealed high levels of soil salinization in the northern and central areas, with 64% of soil samples classified as strongly and very strongly saline. Soil chemistry indicated salinization sources linked to sodium chloride dominance. Satellite data from Sentinel-2 images and SRTM digital elevation data showed widespread severe waterlogging in the northern lowlands. The Irrigation Water Quality Index (IWQI) values indicated that 87.5% of irrigation water samples posed severe restrictions due to high salinity and sodium hazards, which were mismatched with the low soil permeability observed in 81% of the collected samples exhibiting clay texture and covering most of the study area. Furthermore, shallow groundwater at depths of 0.5–3 m with high salinity was detected, where total dissolved solids exceeded 20,000 mg/L, and Na-Cl water types prevailed, indicating saltwater intrusion. A strong positive correlation (r > 0.83) was found between shallow saline groundwater and soil salinity. The combination of poor irrigation water quality, shallow saline groundwater tables, and low-permeability soils created a synergistic effect that severely compromised soil health and agricultural productivity. It also posed severe risks to the structural integrity of archaeological sites and buried artifacts through accelerated physical and chemical weathering processes. This necessitates an urgent mitigation strategy to combat soil degradation in this critical area.

Identifying seawater interaction with coastal aquifers using hydrochemical and GIS for Nagapattinam district, southeast coast of India

Groundwater chemistry of the two different seasons collected between 2020–2021 from the coastal areas of Nagapattinam, Mayiladuthurai and Karaikal in Tamil Nadu state of southeast India were evaluated for seawater intrusion into coastal aquifers. Groundwater types, its classification was evaluated to know the extension of seawater intrusions into coastal aquifers using the Groundwater Quality Indices (GQI) such as GQIPiper(mix), GQIPiper(dom), fsea, GQIfsea and GQISWI. Piper diagram grouped most samples (GQIPiper(mix) and GQIPiper(dom)) in domain-II, representing Na-Cl water type, followed by domain-IV, indicating mixed Ca-Mg-Cl water for both the seasons. As measured by the saltwater Intrusion as Groundwater Quality Index (GQISWI), about 62.5 % and 37.5 % of the pre-monsoon samples showed low saltwater intrusion and moderate seawater intrusion, respectively. In the post-monsoon samples, the low saltwater intrusion increased to around 82.5 % and the moderate seawater intrusion decreased to 17.5 % of the groundwater samples. The GIS framework was used to display the geographical distribution of groundwater types as well as the delineation of vulnerable zones from seawater intrusion.

Major Ions and Trace Elements Characterization of Groundwater in Shallow Aquifers, Yaoundé Urban City, Cameroon

Purpose: This study assessed the suitability of groundwater in parts of Yaoundé city for drinking and domestic purposes, investigating the factors controlling its composition. Materials and Methods: Water samples were collected during the dry season and analyzed for physicochemical parameters and major ions. Findings: Results showed an acidic aquifer with generally fresh water, dominated by Ca-HCO3, Na-Cl, Ca-NaHCO3, and Ca-Cl water types. While most major ions were within WHO guidelines, nitrates exceeded safe limits in most samples, and some trace elements like aluminum, manganese, and iron were also above recommended levels. Implications to Theory, Practice and Policy: The study concludes that groundwater quality is influenced by water-rock interaction, ion exchange, and anthropogenic activities, particularly nitrate and chloride pollution. Therefore, proper groundwater management strategies are crucial to ensure the sustainability and safety of this vital resource.

Groundwater assessment for sustainable development in the Wadi Al-Hamd Basin, Al-Madinah Al-Munawarah, KSA

This study relied on well monitoring many drilled wells data in the Wadi Al-Hamd Basin to determine water level and chemical properties from field measurements. The characteristics of groundwater must be assessed in terms of present and future eases and stresses to ensure sustainable development. Hydrogeological, hydrochemical, groundwater quality indices and Geographic Information Systems (GIS) data sets have been integrated to assess the groundwater aquifer in the study area. To implement this work, we measured the depth to the water table from eighty-eight drilled wells. Also, the major ions were determined from 82 water samples to evaluate the physicochemical properties, groundwater facies, and controlling mechanisms using diagrams such as the modified Piper proposed by Chadha, Total Ionic Salinity (TIS), and Gibbs. In this study, five irrigation water quality indicators (IWQI), including total dissolved solids (TDS), sodium adsorption ratio (SAR), potential salinity (PS), magnesium hazard (MH), and residual sodium carbonate (RSC) have been determined to assess the suitability of groundwater for irrigation. Based on the findings of this study, groundwater flows from the southeast and northwest to the west and south, respectively. In this basin, 56% of water samples have TDS greater than 2000 mg/L, while 62% of water points are categorised as Na–Cl water type, which indicates that evaporation and rock–groundwater interaction influenced groundwater quality evolution. Almost 87% of samples were rated good to excellent for irrigation use with respect to SAR. On the other hand, all water points are suitable for irrigation based on RSC. Likewise, groundwater is suitable for irrigation purposes despite the relatively high PS levels (>5 meq/L in about 49% of samples) and some small spots with high levels of MH (>50% in about 12% of samples), especially in the southern and central portions of the studied basin.

Study of Environmental Isotopes and Hydrochemical Characteristics of Groundwater from Springs at Archaeological Sites in Dompu Regency, West Nusa Tenggara, Indonesia

The existence of groundwater sources in several springs at archaeological sites in Dompu Regency, West Nusa Tenggara, Indonesia, has been widely used by the surrounding community for various needs. However, from a number of the springs, there are springs whose water discharge has decreased. Meanwhile, from a number of existing springs, there is one spring whose groundwater is used every day even though it tastes a bit brackish. For this reason, it is important to conduct a groundwater study in the area with the aim of knowing the characteristics, preliminary identification of recharge areas and quality of groundwater in the study area through an environmental isotope and hydrochemical. The study was conducted by taking a number of groundwater samples from several archaeological sites in Dompu Regency. The results of environmental isotope and hydrochemical analysis show that there are 2 springs (2 archaeological sites), namely the Riwo and Ncona springs, because these two areas are part of the recharge area, which must be preserved by not clearing forest land. Meanwhile, for the quality of groundwater, of the 5 springs located at the archaeological sites, only the Hodo spring is of “poor quality” with the Na–Cl water type; it is unfit for drinking water.

The Effect of Sodic Water Type on the Chemical Properties of Calcareous Soil in Semi-Arid Irrigated Land

Irrigation of calcareous soil with saline–sodic water can modify the composition of the soil solution and exchange complexes in agricultural land of arid and semi-arid regions with low water resources. The objective of this study was to monitor (medium-term) potential changes in a calcareous clay soil irrigated with two types of sodic waters without cropping. Irrigation water with two high sodium adsorption ratios (SAR = 20 and 40) and electrical conductivity (EC < 3 dS m−1) was prepared using NaCl and NaHCO3 salts. The sodic irrigation waters were applied (June–October) in three periods (1, 2, and 4; one period = five irrigations) to bare non-saline soil with drip irrigation during two growing seasons; no irrigation action was taken in the winter–spring rainy season (period 3). Sampling (0–30 cm) was made after each period to determine the changes in soil pH, EC, water-soluble Na+, Ca2+, Mg2+, K+, Cl−, and HCO3−. Relative to the control, irrigation with both sodic waters increased soil pH, EC, and water-soluble Na+ and decreased or did not change water-soluble cations (Ca2+, Mg2+). The Cl− concentration increased rapidly with NaCl-type water application, but it was leached away quickly by winter–spring rains. The HCO3− concentration increased with NaHCO3-type water application, yet it leached out slowly in the rainy period. The movement of HCO3− ions in the upper soil profile (0–30 cm) was significantly slower compared to Cl− ions. Dissolution of slightly soluble soil CaCO3 by irrigation increased the solution concentration of Ca2+ and its mobility, yet the kinetics of processes depended on water type and irrigation period. The released Ca2+ interacted with other cations in the soil, causing further significant positive physicochemical changes in the soil solution and exchange capacity (comparable with control soil) at the end of the irrigation period. The CaCO3 content in the soil would be a long-term guarantee of the Ca2+ resource in soils, even if the amount of water-soluble Ca2+ may decrease for the short-term period during irrigation. The results should be considered for rational irrigation management (with various water qualities) in semi-arid and arid regions.

Hydrogeological Investigations of Groundwater and Surface Water Interactions in the Berg River Catchment, Western Cape, South Africa

The Berg River Catchment based in the Western Cape Province, South Africa services the greater Cape Town area with water, subsequent to supplying the vast agricultural activities that exist in the middle and the lower reaches. This study thus investigates the hydrogeochemical interactions between surface and groundwater in the Berg River Catchment with the aim of establishing trends and transfer of constituents between the surface and groundwater systems, investigates the role that geology plays in water chemistry as well as identifies the geochemical processes controlling surface and groundwater chemistry in the catchment. This study was carried out using three types of research designs namely i) experimental research design; ii) field research design and meta-analysis research design. Furthermore, the study made use of hydrochemical data ranging from 2003 to 2013 obtained from the National Water Monitoring Database owned and maintained by the Department of Water and Sanitation and data that were sampled in 2016 by authors and analyzed using the ICP-MS Technique Ground Water Chart, Arc-GIS and Geosoft (Oasis Montaj) were further employed to model the data. The results indicated that: i) in the Upper Berg there is not much interaction and transfer of constituents between surface and groundwater; ii) the Middle Berg, however, indicated a degree of interaction with the sharing of constituents between the two water systems and iii) the Lower Berg indicated only NaCl water type also noting that the area situated near the river mouth whereby there is the mixing of river and seawater.

Application of radium isotopes to estimate seawater intrusion rate in coastal aquifers

Coastal aquifers, as the interface zone between ocean and land, are highly sensitive and vulnerable to seawater intrusion. This study presents the behavior of radium isotopes and their application to estimate the rate of seawater intrusion in a typical coastal city (Qinhuangdao, China). The hydrochemical results indicated that the coastal aquifers have Na–Cl type water with the lower Na/Cl ratios. The analysis revealed that the formation process of the chemical composition of groundwater was mainly the mixing of seawater and groundwater, while that of inland groundwater was dominated by mineral dissolution and cation exchange and adsorption. Groundwater of intruded aquifers contain significantly higher activities of radium than those of nearshore seawater and inland groundwater. The rates of seawater intrusion were estimated by using equation of the fate and transport of radium in 1–D transient groundwater flow system. In the calculation process, we ignored dissolution and co-precipitation and mainly considered mixing, alpha recoil and decay contribution for radium activity as sources and sinks terms of radium in coastal groundwater based on the characteristics of radium activity and 224Ra/228Ra ratio in groundwater. The recoil (P) was determined by the activity ratio of 224Ra to Th (232Th/230Th), while the retardation (Rf) was calculated from the steady-state radium equilibrium equation. The seawater intrusion rates were obtained by integrating 224Ra and 228Ra activities under different thorium ratios (232Th/230Th). The results show that the rate of seawater intrusion varies in a wide range at different locations, which are 0.17–1.03 (232Th/230Th = 0.67) and 0.11–1.01 (232Th/230Th = 1.25) m/d. The method of calculating seawater intrusion rate with radium isotope can obtain the rate of different parts of heterogeneous anisotropic aquifer, which also extends the application of radium isotope in hydrogeology.

Hydro-geochemistry and Related Processes Controlling the Composition of Thermal Waters in the Lake Natron Basin, Northern Tanzania

Lake Natron Basin (LNB) forms part of the eastern branch of the East African Rift System (EARS) in Tanzania. The basin is endowed with thermal springs flowing towards the lake from the western, northwestern, southwestern and eastern parts. The western, northwestern and south-western thermal springs emanate from fractures in the basaltic rocks while in the east, they originate from the western flank of the Gelai volcano. There are limited studies on these springs, thus their geochemical differences and distributions of physicochemical parameters are not well understood. A hydrogeochemical study was conducted to interpret available geochemical data from the LNB springs, including cold and thermal water to allow their geochemical characterization. Results have shown that LNB water is dominated by sodium (Na+), chloride (Cl-) and bicarbonate (HCO3-) ions. Three hydro-chemical facies have been identified forming Na-Cl, Na-HCO3 and Ca-HCO3 water types. This study has also revealed that thermal water in the north-western part of the basin is highly mineralised and gradually becomes diluted toward south-west and south due to groundwater incursion. Water-CO2-rock interaction affects the overall chemistry of thermal water leading to HCO3- water, particularly in the east of the basin. While few springs from the western side of the basin indicated maturity of the thermal waters, other springs indicated mixed Cl-HCO3/peripheral water; while the cold waters are HCO3 type. It is recommended to take precautions when planning geothermal projects to avoid corrosion and scaling of production facilities. Similarly, mixing or dilution of thermal water with shallow groundwater can affect the temperature and the composition of Cl-.

Hydrogeochemical and isotopic evolution of groundwater in shallow and deep aquifers of the Kabul Plain, Afghanistan.

Groundwater from shallow and deep aquifers are widely used for drinking, agricultural and industrial use in Kabul, the capital of Afghanistan. However, unplanned urbanization and rapid population growth has led to the installation of numerous unlicensed wells to meet the public demand. This has caused to extraction of huge amounts of groundwater from the subsurface and further deterioration of groundwater quality. Therefore, understanding the hydrogeochemical characteristics of groundwater in shallow aquifers and deep aquifers is imperative for sustainable management of the groundwater resource in Kabul Plain. Thus, in this study, we used a multi-parameter approach, involving hydrochemical and environmental isotopes to understand the geochemical evolution of entire groundwater system of the Kabul Plain including river and dam water. The results of this study show that shallow and deep aquifers are dominantly of Mg-(Ca)-HCO3 and Na-Cl water type, respectively. We observed that (1) water-rock interaction is the major contributing factor to the chemical compositions of groundwater in the Kabul Plain; (2) groundwater in deep aquifer is mainly influenced by silicate weathering, and dissolution of evaporitic and carbonate minerals and reverse cation exchange; (3) dissolution of carbonates and silicate weathering plays a pivotal role in the groundwater chemistry of shallow aquifer; (4) the stable isotopes of groundwater display that the shallow aquifer is principally recharged by river water and local precipitation; (5) the tritium analysis exhibited that groundwater of shallow aquifer was primarily recharged recently, whereas groundwater of deep aquifer is the mixture of pre 1953 with post 1953 groundwater. This study revealed that there are hydraulic interactions between the two aquifers and the deep aquifer is recharged through shallow aquifer. The findings of this study would be useful for Afghanistan's water authorities to develop an effective strategy for sustainable water resources management in the Kabul Basin.

The influence of stormwater infiltration on downslope groundwater chemistry

Stormwater infiltration basins have been used extensively around the world to restore urban hydrology towards more natural flow and water quality regimes. There is, however, significant uncertainty in the fate of infiltrated water and accompanying contaminants that depends on multiple factors including media characteristics, interactions with downslope vegetation, legacy contaminants, and presence of underground infrastructure. Understanding the influence of such factors is thus central to the design and siting of infiltration basins. An extensive field program was established to collect monthly data on ground water quality, including nutrients and major ion concentrations, in a bore network downstream of a stormwater infiltration basin in Victoria, Australia. The groundwater samples were analysed for temperature, pH, EC, turbidity, major ions (Na+, Ca2+, K+, Mg2+, Cl−, SO42−, NO3−, CO32−, HCO3−), NOx and heavy metals. The collected data were used to understand the origin and fate of water and solutes in the subsurface and their interactions with the soil matrix. The results revealed that Ca–HCO3, Na–Cl water types predominate in the study area, grouped in 3 clusters; shallow fresh groundwater in the vicinity of the basin (near basin), deep saline groundwater further downstream of the basin (near-stream) and a mid-section where rock-water interaction (Na–HCO3 water) through cation exchange control the chemistry of groundwater. The results also suggest that as the water moves downstream of the basin, it experiences significant evapotranspiration and concentration due to the presence of deep-rooted vegetation. The results suggest that while infiltration basins can remove infiltrated contaminants, the infiltrated stormwater can mobilise legacy contaminants such as nitrate. Overall, the efficacy of infiltration basins in urban regions depends substantially on the downstream vegetation, urban underground infrastructure and the presence of legacy contaminants in the soils. These all need to be considered in the design of stormwater infiltration basins.

Hydrogeochemical and multivariate statistical approaches to investigate the characteristics of groundwater quality in fluoride-enriched hard rock region in Tirupathur district of Tamil Nadu, India.

Fluoride pollution is a major issue worldwide, posing health risks such as dental and skeletal fluorosis. This study was conducted in fluoride enrichment hard rock regions of Vaniyambadi and Ambur talks in Tirupathur district, Tamil Nadu. Four hundred eighty groundwater samples were collected from May 2021 to April 2022 and grouped as summer, southwest monsoon (SWM), northeast monsoon (NEM), and winter. Maximum concentration of fluoride was found to be 4mg/L in the summer season in Vellakuttai region of Vaniyambadi taluk. The study aims to investigate the hydrogeochemical process and mechanism influencing groundwater chemistry and it also provides the confirmation of exploratory data analysis in groundwater quality using structural equation modeling. The Piper and Gibbs diagrams illustrate the rock-water interaction and anthropogenic sources that contribute to the NaHCO3 and NaCl-type waters, respectively. Multivariate statistical analysis such as hierarchical cluster analysis (HCA), principal component analysis (PCA), multiple linear regression (MLR), and structural equation modeling (SEM) has been carried out to determine the groundwater quality. HCA manifests the nature and sources of groundwater, whereas PCA divides all the physicochemical parameters into two PC loadings, accounting for 97.46%, 99.46%, 99.18%, and 98.93% of cumulative % of variance during the summer, SWM, NEM, and winter seasons, respectively. PC1 has a higher loading factor to Cl, Ca, and Mg, whereas PC2 has a higher loading factor to Na, HCO3, SO4, and NO3. The results of the MLR model provide higher accuracy in detecting the contamination factors associated with the environment and natural rocks. SEM revealed the goodness-of-fit indices 0.993, 0.999, 1.000, and 0.999 in summer, SWM, NEM, and winter, respectively. Hence, this study provides insight view of variation of fluoride concentration in groundwater in different seasons and also mentions the factors that influence fluoride concentration in Vaniyambadi and Ambur taluk.

Hydrogeochemistry and isotopic assessment of a new geothermal prospect in rancho Nuevo (Guanajuato-Central Mexico)

Mexico has five high-temperature geothermal fields, three of which are located in an active volcanic arc known as the Trans-Mexican Volcanic Belt in central Mexico. In this geological province, there are numerous hot springs, many of which have not been studied yet. It is the case of the Rancho Nuevo area, which is composed of two hot springs and thermal groundwater wells. The present study focuses on the hydrogeochemical and isotopic characterization of the Rancho Nuevo geothermal system. According to the results cationic exchange, silicates and carbonates rock alteration processes are occurring. A cooling of thermal water is also carried out caused by a mixing process between deep Na-Cl type water and shallow Na-HCO3. In addition, the most relevant process identified in the study area is the water-rock interaction and corroborated by the stable isotope results showing enrichment of δ18O. All these processes are enhanced by the thermal activity in the region. The CO2 and N2 concentrations confirm the geothermal activity in the Rancho Nuevo area. The CH4 concentration is also typical of geothermal fluids and may represent a magma degassing.Finally, the reservoir temperature was estimated at 225 °C ± 15 °C based on silica, cation, and integrated multicomponent solute geothermometers. Therefore, the Rancho Nuevo geothermal area can be defined as a high-temperature system and as a very interesting prospect; however, for geothermal resource production, the calcium carbonate deposition in the wells shall be considered.

Spatial and temporal variations of geochemical processes and toxicity of water, sediments, and suspended solids in Sibuti River Estuary, NW Borneo

A comprehensive geochemical study was conducted in the Sibuti River estuary by considering water, suspended solids (SS), and sediment samples from 36 stations during southwest monsoon (SWM) and northeast monsoon (NEM). In this study, the distribution of in situ parameters, major ions, nutrients, trace metals, and isotopes (δD, δ18O) were analyzed in water samples, whereas sediments and SS were studied for trace metals. The distribution revealed that suspended solids were the major carrier of Cd, Zn, and Mn, whereas sediments worked as a major source of Co, Cr, Ba, Se, Cu, and Pb. Na-Cl water type and ion exchange dominated the lower part of the estuary during both seasons. However, the mixed mechanism of Ca–Cl, Ca–Mg–Cl, and higher weathering indicated reverse ion exchange in the intermediate and upper parts of the estuary. Isotopic signatures of δD and δ18O in estuarine water indicate that the precipitation over the Limbang area dominates during SWM, whereas higher evaporation was confirmed during NEM. The factor analysis revealed that seawater influence in the estuary majority controlled the water chemistry irrespective of seasons. Major ions were mainly regulated by the tidal influence during the low flow time of the river (SWM), whereas the mixing mechanism of weathering and seawater controlled the concentrations during NEM. Nutrients such as NO3, SO42−, NH3, and NH4+ mainly originated from the agricultural fields and nitrification along with ammonification were responsible for the recycling of such nutrients. Trace metals except Cd were found to be geogenic in nature and originating mainly from the oxidation of pyrites present in the sandstone and mudstones of the Sibuti Formation. Redox condition was catalyzed by microorganisms near the river mouth, whereas Al-oxyhydroxides and Fe-oxyhydroxides complexes in the intermediate and upper part under oxygenated conditions controlled the absorption of metals. Overall, the estuary was found to be absorptive in nature due to ideal pH conditions and was confirmed by the saturation index (SI) of minerals.

Groundwater Management for Agricultural Purposes Using Fuzzy Logic Technique in an Arid Region

The study aimed to determine groundwater’s suitability for irrigation and cattle rearing in Kuwait. In this regard, groundwater samples were collected from Umm Al Aish (UA) and adjoining Rawdhatain (RA) water wellfields to develop groundwater suitability maps for irrigation purposes using the fuzzy logic technique in ArcGIS. RA was dominated by Na-Cl, Na-Ca, and Ca-SO4 water types, whereas UA was dominated by the Ca-Mg water type. Due to the influence of the temperature and pCO2, the carbonates were inferred to be more susceptible to precipitation in the soil than the sulfates. The ternary plots for both regions revealed that the samples’ suitability ranged from good to unsuitable. Spatial maps of nine significant parameters governing the irrigation suitability of water were mapped and integrated using the fuzzy membership values for both regions. The final suitability map derived by overlaying all the considered parameters indicated that 8% of the RA region was categorized as excellent, while UA showed only 5%. Samples situated in the study areas showed an excellent to very satisfactory range for livestock consumption. Developing a monitoring system along with innovative water resource management systems is essential in maintaining the fertility of the soil and existing groundwater reserves.

Mapping the impacts of the anthropogenic activities and seawater intrusion on the shallow coastal aquifer of Port Said, Egypt

The quality and quantity of groundwater resources have been continuously deteriorating as a result of anthropogenic activities and their excessive usage. This has intensified seawater intrusion, particularly in the coastal area of Egypt. The management of this issue and preventing ongoing groundwater contamination are crucial responsibilities. Thus, an integrated strategy using remote sensing, geophysical technique, and hydrogeochemical analysis is used in this work to identify the causes of degradation and evaluate their impacts on the groundwater quality in East Port Said, Egypt. The following points were identified: 1) Remote sensing analysis between 1984 and 2015 showed an increase in anthropogenic activities, such as the construction of fish farms and vegetation, which became their areas of 12.5 and 37.8 km2 respectively. 2) Field observations demonstrated that the groundwater resources are being overexploited and it is expected that these human activities could have an impact on the groundwater quality. 3) The results of the resistivity approach indicated that sand and clay constitute the underlying layers and the shallow subsurface strata contain a high concentration of saline water. As a result, the aquifer is vulnerable to seawater intrusion due to its homogeneity. 4) Nineteen samples of groundwater were collected from the shallow Quaternary aquifer and the hydrochemical characteristic of the samples was identified. The hydrochemical analysis showed that the groundwater across the research area is of the Na-Cl water type and is highly saline (from 7,558 to 23,218 mg/L). By integrating the aforementioned techniques, it is evident that the research region is affected by anthropogenic activities as well as seawater intrusion on groundwater quality. These results serve as a solid base for further research on groundwater-surface water interactions and the evaluation of possible sources of contamination in the shallow aquifers under stress from anthropogenic activity in such environments.

Water quality and hydrochemical assessments of thermal springs, Gandaki Province, Nepal

Thermal springs are the sites where the water temperature lies above ambient temperature. They are widely used for power generation, hot water spas, balneotherapy, agriculture, laundering, and aquaculture. In Nepal, many thermal springs are reported but scientific understanding on water quality and hydrogeochemistry of the springs is very limited. In this study, a total of 28 physico-chemical parameters were measured in water samples collected from 12 thermal springs from Gandaki Province, Nepal. Correlation matrix and multivariate statistical analysis such as principal component analysis (PCA) and cluster analysis were used to understand the water quality and hydrogeochemistry of the hot water springs. The pH, temperature, electrical conductivity, total dissolved solids, and turbidity in the hot water springs ranged from 7.3 to 8.8, 31.6–64.3 °C, 206–16270 μS/cm, 115–6637 mg/L, and 0.21–63.7 NTU; respectively. The dominance order of major anions and cations were: Cl− > HCO3− > SO42− > NO3− > F− and Na+ > Ca2+ > K+ > Mg2+; respectively. Comparison of the water quality parameters with the WHO and National Water Quality Standards suggested that the majority of the parameters were within the safe limit. Out of 9 heavy metals and trace elements analyzed Zn2+, Ni2+, Cr3+, Cd+2, Hg (total), and Pb2+ were found below the safe limit but Fe (total), As (total) and Cu (total) were found higher than the WHO safe limit in total of 3, 5 and 1 sampling sites; respectively. The water quality index (WQI), sodium absorption ratio (SAR), and magnesium hazard (MH) ratio in the hot water springs ranged from 40.9 to 573, 2.2–49.3, 7.1–70.8; respectively. The result of PCA analysis showed that four principal components are required to explain hydrogeochemistry. Cluster analysis suggested that the sampling sites can be grouped into three distinct clusters based on total dissolved solids. Interestingly, the classification of hydrochemical facies using a Piper diagram suggested that 7 out of 12 thermal springs have Na–Cl type water. Finally, a perspective on the suitability of the hot springs for hot water spas and balneotherapy and policy recommendation is provided.

Geochemical evaluation of mud volcanic sediment and water in Northern Borneo: A baseline study

A comprehensive geochemical investigation was carried out to characterise the sediment and water seeping out from mud volcano, in Kampung Meritam, Limbang, northern Borneo. Chemical analysis included major oxides, trace metals, rare earth elements, and major ions. Interpretation of results reveals that the geochemical composition of sediment samples is originated from sedimentary provenance particularly Setap Shale, which is the dominant Formation present in this region. The concentration of trace elements and major oxides were used to identify the origin and weathering nature of sediment. SiO2 is the dominant major oxide present in the sediment samples with an average concentration of 58.24%. Whereas for trace metals, Ba is dominating with an average concentration of 263ppm. Environmental pollution indices such as contamination factor, geoaccumulation index, and enrichment factor were used to assess the contamination level of mud volcanic sediments. Hydrochemistry of mud volcano suggests that the water is derived from ionic enriched solute, indicated by Na-Cl water type. The average concentration of Na+ and Cl- is 987 mg/L and 10457.50 mg/L. The ionic ratios suggest that water-rock interaction including carbonate mineral dissolution is the predominant process that controls the water chemistry. Gibbs diagram shows that the water is influenced by the dissolution of evaporite minerals. Thermodynamic stability and saturation index were used to evaluate the mineral stability and saturation condition during weathering. Ca2+ and Mg2+ were released into the water due to the reverse ion exchange process, which was supported by XRD results. Higher ionic strength and Log pCO2 values suggest longer residence time of water in the aquifer matrix and therefore significant dissolution of enriched solute due to the intensive water-rock interaction. The outcome of this study would provide the basis for a better understanding on the geochemical characteristics of Meritam mud volcano in Northern Borneo.

Geochemical evaluation of groundwater around Chromepet tannery belt, Southern India

The study appraises the geogenic and anthropogenic contamination of groundwater around tanneries located in Chromepet, Southern India. Thirty-six groundwater samples were examined for major anions, cations and trace metals concentration. The concentration of chromium (Cr), iron (Fe) and lead (Pb) in the study area ranges from 0.04 to 0.51 mg/L, 0.001–1.07 mg/L and 0.001–0.09 mg/L respectively. 97% of the samples exceeded the acceptable range for Cr whereas, lead and iron exceeded 89 and 8% of the samples respectively. The high concentrations of chromium, iron and lead in the groundwater are due to the influence of tannery effluents. The majority of the samples in the study area suggested silicate weathering. The piper plot reveals that 50% of the water samples have Na–Cl type water which is possibly due to anthropogenic sources. The Chadha plot revealed that silicate weathering and ion exchange govern the bulk of groundwater chemistry in freshwater aquifers owing to carbonate precipitation and mineral dissolution. Durov plot highlights that the bulk of the samples has no dominating anion or cation types, indicating simple dissolution or mixing. Saturation Index (SI) reveals that 50% of the samples were supersaturated due to calcite and dolomite precipitation. Principal Component Analysis (PCA) 1 suggested secondary salt discharge from geogenic and anthropogenic processes due to tanning industries. Increasing the performance of wastewater treatment plants is essential to improve the groundwater quality of the region under tannery influence.

Tracing Saltwater Intrusion into Shallow Mangrove Aquifers Using Hydrogeochemical Analysis and Isotopes of Oxygen and Hydrogen

AbstractCoastal aquifers that are hydraulically connected to the ocean suffer from the compromised of the wholesomeness of freshwater. The extent of the effect is largely dependent on the degree of aquifer stressing. Consequently, ratios of the stable isotopes of hydrogen (δ2H) and oxygen (δ18O) are integrated with ionic ratios of groundwater samples to assess the effect of intrusion on shallow aquifers in a low‐lying area of the western Niger Delta basin. Geochemical analysis shows sodium chloride (NaCl) water type, an indication that intrusion has a noteworthy effect on concentrations of groundwater by having values of total dissolved solids, electrical conductivity, and Cl− in excess of 1000, 500, and 250 mg L−1, respectively. Major ionic ratios of Na+/Cl− (0.06–1.76), Ca2+/Mg2+ (0.48–0.98), Cl−/HCO3− (148.77– 88), Cl−/HCO3− + SO42− (>1), and base exchange index (14.03 to 1.26) are largely indicative of intrusion. The δ18O and δ2H composition of groundwater and the brackish Forcados River samples reveal values that range from −4.2‰ to 1.08‰ and 0.18‰ to 3.8‰, respectively. The shallow groundwater samples are more depleted than the deep aquifers with δ18O values of −4.2‰ to −3.8‰ and δ2H of −20.99‰ to 18.51‰, respectively. The Cl−/δ18O ratios show the mixing of shallow aquifers with saltwater (SW) from the ocean.