Hydrogeochemical Tools Research Articles

Understanding water characteristics and arsenic contamination of Lower Bakırçay Basin (LBB) and its coastal wetland (Western Turkiye): from Bergama (Pergamum) to Çandarlı (Elaia) by hydrogeochemical tools and stable isotope signatures.

Bakırçay Basin is one of the largest and most productive basins in Turkey in terms of geothermal energy, history, mining, agriculture, and tourism. In this study, the lower part of the Bakırçay Basin was extensively examined using hydrogeochemical tools, encompassing 27 different water sample points in the basin, in alignment with the United Nations' 2030 sustainable development goals that focus on access to safe drinking water for all and climate action for carbon emissions. From the higher zones of the basin towards the coastal wetland, EC values increase from 212 to 26500 µS/cm. Again in the same direction, water types are Ca-Mg-HCO3 in hilly areas and Na-Cl at the coastal wetland. Salt marshes, which are the silent heroes of carbon sequestration, are the most important element of the Bakırçay coastal wetland. Irrigation water evaluation has also been made for agriculture, which is widespread in the basin. Except for the salty waters in the wetland, waters are suitable for irrigation. A contamination investigation was conducted in the waters with the aim of clean drinking water. As and Mn contamination, which exceeds the standard values, has been detected in the Bakırçay river and its tributaries, especially from the mining sites in LBB. The arsenic content of water in the study area varies between 2 and 62.2 ppb. Additionally, the study identified As(III) species, which is 60 times more toxic than As(V), in the study area. Stable isotope values (δ18O and δD) of waters in the basin are from - 6.66 to 1.43‰ and - 36.4 to 5.8‰, respectively, and all waters are of meteoric origin. It is essential to emphasize the importance of controlling mining activities in the basin, halting the construction of the port that will destroy the carbon sequestration coastal wetland, and instead, transforming it into a recreation area, the significance of which is now understood during the COVID-19 pandemic.

Use of hydrogeochemical tools to evaluate seawater intrusion: a case study of Upper Pliocene Aquifer in the Ca Mau Peninsula, Vietnam

Groundwater resources have been withdrawn significantly to meet the demands of agricultural economic development in the Ca Mau Peninsula, Mekong River Delta. As a result, aquifers face the risk of groundwater levels decline and high salinization potential. This study uses the groundwater quality index (GQI) and hydrochemical facies evolution diagram (HFE-D) to assess the hydrochemical characteristics and salinization potential of the Upper Pliocene aquifer (n2 2), which is one of the two most exploited aquifers in the Mekong River Delta. A total of 6 monitoring wells were used to observe groundwater level and water quality from 2017 to 2020. The GQI results ranged from 33.38 to 75.61, indicating that groundwater in Hau Giang and Soc Trang areas is salinized. The spatial distribution results of HFE-D stated that the boundaries of intrusion and freshening have varied in space and time. Specifically, the Upper Pliocene aquifer has been in the process of seawater intrusion. The freshwater area in the Ca Mau has been gradually shrinking in the East Sea area faster than the West Sea area. The displacement speed of the intrusion and freshening boundary varied considerably from 0.04 to 0.67 km/year from 2017 to 2020.

Interactions of waste disposal site leachate with the Merida karst aquifer, Mexico

Hydrogeochemical tools were applied to evaluate the effect caused by the presence of municipal waste leachate on the balance of a karstic aquifer. The system evaluated correspond to the aquifer underlying the area of the old municipal waste disposal site (MWDS) in the city of Merida, Mexico. A contaminant plume identified with chloride ion concentrations was detected. Groundwater samples were collected from boreholes located along a flow line, starting at the downstream boundary of the dump site. The parameters involved in the carbonate system were analyzed, obtaining a decline in calcium (Ca2+) and magnesium (Mg2+) concentrations for high pCO2 values. This behavior is explained by the presence of high bicarbonate (HCO3–) content, as a result of the waste decomposition reactions. The bicarbonate ions behaved as a buffer preventing pH reduction. In addition to this, the calcium and magnesium species indicate that the formation of complexes affected the mineral solubility where leachate has the greatest influence. The transport of minerals, in moles, between boreholes located along the groundwater flow line, was determined through inverse modeling. It is concluded that the leachate affects the carbonate balance, as determined by the transfer of minerals along the flow line; it was observed that mixed waters with a higher percentage of leachate tend to dissolve carbonate minerals. This is the analogous to findings reported in other leachate contaminated aquifers.

Temperature estimation of the Nevado del Ruiz Volcano geothermal reservoir: Insight from western hot springs hydrogeochemistry

Geochemical surveying is one of the techniques of geothermal exploration that include geothermometry to estimate the temperature of deep reservoirs. This work provides the temperature estimation of geothermal resources, geochemical analysis, and a conceptual model of the geothermal reservoir located to the western flank of the Nevado del Ruiz Volcano (NRV), a mayor geothermal target for energy production in Colombia. Hydrogeochemical data (pH, temperature, electrical conductivity, major, minor, and trace elements) were obtained from water samples collected at several hot springs located to the west of the NRV between 2017 and 2019. The data available from the Colombian Geological Survey database were also included in the analysis to better characterize the hot spring behavior. The hydrogeochemical tools Liquid analysis Powell and Cumming and GQAnalyzer software were used to draw ternary diagrams and to use geothermometers. The results allowed separating the hot springs into two groups, according with their chemical characteristics and spatial location: Nereidas 1, Nereidas 2, Nereidas Pozo, and Chorro Negro hot springs belong to Group 1 (G1), located closer to the NRV; on the other hand, Geysers, El Bosque-La Piscina, Quebrada Negra, and Rio Claro, which are located further from NRV, belong to Group 2 (G2). The latter is made of mature and chloride waters, indicating a water-rock equilibrated interaction with most of ions. The results of this study contribute to the future Colombian geothermal development, and the methodology and analysis can be applied to geothermal systems with similar geological characteristics to infer a conceptual model useful for geothermal exploration.

Hydrochemical Assessment of Water Used for Agricultural Soil Irrigation in the Water Area of the Three Morava Rivers in the Republic of Serbia

The assessment of the suitability and status of irrigation water quality from the aspect of its potential negative impact on soil salinization and mapping of spatial distribution within the area of the three Morava rivers, which includes the South, West, and Great Morava basins, was the purpose of this research. A total of 215 samples of irrigation water were tested, and their quality was evaluated based on the analysis of the following parameters: pH, electrical conductivity (EC), total dissolved salt (TDS), sodium adsorption ratio (SAR), and content of SO42−, Cl−, HCO3−, CO3 2−, Mg2+, Ca2+, Na+, and K+. The results showed that the average content of ions was as follows: Ca2+ > Mg2+ > Na+ > K+ and HCO3− > SO42− > Cl− > CO32−. The assessment of irrigation water suitability was determined by calculating the following indices: percentage sodium (Na %), residual sodium carbonate (RSC), permeability index (PI), magnesium hazard (MH), potential salinity (PS), Kelley’s index (KI), total hardness (TH), irrigation water quality index (IWQI). Based on Wilcox’s diagram, the USSL diagram, and the Doneen chart, it was concluded that most of the samples were suitable for irrigation. Using multivariate statistical techniques and correlation matrices in combination with other hydrogeochemical tools such as Piper’s, Chadha’s, and Gibbs diagrams, the main factors associated with hydrogeochemical variability were identified.

Integrated Hydrogeochemical Analysis of Stream Water in Parts of Proterozoic Shillong Basin Meghalaya, India

Hydrogeochemical surveys were conducted in parts of the Proterozoic Shillong basin in Meghalaya to locate the unconformity-related uranium deposits, related alteration patterns, and the influence of the rock formations on the groundwater solute chemistry. Shillong Basin comprises Proterozoic metasediments and felsic volcanics of Tyrsad Formation, undeformed arenaceous Barapani Formation with intrusive granites, and metabasic sills and dykes. The groundwater quality is determined for drinking, and domestic-agro-industrial utilities using hydrogeochemical tools and physicochemical parameters. The water is acidic to slightly alkaline and has an oxidizing redox environment, Electrical Conductivity (EC), Total Dissolve Solids (TDS), and major ions fell below the World Health Organization (WHO) and Indian Standards Institute (ISI) acceptable limits except for Zn, Fe, and SiO2 showing higher concentrations.The sequences of abundance of major cations and trace elements are Fe>Zn>SiO2>Ca2+>Na+ >Mg2+>K+ >U and anions as HCO3>Cl- >SO4 2- .Groundwater character was assessed by ion exchange, simple dissolution, and unusual dissolution mechanisms. The area has dominant CaHCO3, NaHCO3, and restricted CaMgHCO3 type water. Plagioclase dissolution and high SiO2 and cation exchange of Ca for Na were identified. The groundwater indices of Sodium Percent, Kelley’s Index, Sodium Adsorption Ratio, Magnesium Ratio, Electrical Conductivity, TDS, USSL, and Wilcox index were found suitable for agro-industrial uses. Permeability Index is found to be suitable in most areas and the Corrosivity Ratio shows the areas of galvanized pipes and PVC pipes to be used for water supply. AHC analysis shows three distinct groups of water types, as well as the factor analysis, also shows the three prominent factors of water types defining the dimensionality of water types. Magnesium metasomatic alteration zones and Zn anomalous zones are delineated.

Hydrogeothermal potential assessment in a complex tectonic environment by geophysical and hydrogeochemical tools: a case of the geothermal province of Hajeb Layoun-Jilma-Oued Hjal basins (Central Tunisia)

Hydrogeothermal potential assessment in a complex tectonic environment by geophysical and hydrogeochemical tools: a case of the geothermal province of Hajeb Layoun-Jilma-Oued Hjal basins (Central Tunisia)

Assessment of anthropogenic pollution using multiple hydrogeochemical tools and statistical analysis in rural plain basins of the Argentinian Pampean Plain

AbstractChemistry of surface water and groundwater can be conditioned by geology, anthropic influence, and exchange of flow between them. The Pampean Plain located in Argentina has gaining streams and mainly rural activities. An increase in the concentration of chemical values of surface waters with respect to groundwater can be attributed to the anthropogenic contribution. The aim of this work was to identify the natural and/or anthropic processes that determine the chemistry of surface water and groundwater in a sector of the Pampean Plain of Argentina through the analysis of major and trace elements, 18O and 2H isotopes, and statistical tools. A surface water and groundwater sampling network was designed, where physicochemical parameters were measured, and samples were taken to determine major and trace elements and stable isotopes of water. The results indicate that dissolution, cation exchange, and evaporation are the main processes that determine the chemistry of the major elements associated with natural processes without showing evidence of anthropic involvement. Some trace elements that are statistically associated with major ions evidence water‐sediment interaction within the aquifer. On the other hand, trace elements, as heavy metals, present a higher concentration in surface water compared to groundwater. This fact, evidences an anthropogenic contribution attributable to anthropic activities. The multivariate statistical analysis allowed discriminating between those trace elements associated with natural processes from those influenced by anthropic activity, even when these elements' concentration was very low.

Application of isotope techniques to study groundwater resources in the unconsolidated aquifers along the Ping River (Thailand)

ABSTRACTSevere droughts during the dry season and floodings during the rainy season are among the major problems encountered in the valleys along the Ping River in Thailand. Improving our understanding of the groundwater resources in this agricultural area is an important issue for the sustainable development of the region. Hence, in order to gain understanding on the groundwater flow dynamics in the unconsolidated shallow aquifers along the Ping River, stable (13C, 18O, 2H, noble gases) and radioactive (3H, 14C) isotope techniques were combined with hydrogeochemical tools. The comprehensive interpretation of the chemical and isotope data consistently showed different origins for groundwater in the northern and southern areas of the investigated aquifers. Groundwaters in the northern part have younger 3H/3He ages, are less mineralized, and have suffered a stronger evaporation than groundwaters in the southern part of the aquifer. Overall, our results are consistent with the hydrogeological situation of the investigated area, namely shallow groundwaters and a spatially extended recharge. 3H/3He apparent ages indicated that young groundwater (<50 years) is present in all the investigated wells. Elevated concentrations of some pollutants (nitrate and phosphate) in parts of the aquifer evidenced a relatively high vulnerability of the aquifer to surface pollution.

Seasonal Variations in the Hydrogeochemistry and the Domestic-Agro-Industrial Water Quality of the Granite-Gneiss Fractured Rock Aquiferous formations in Wum, North West Region, Cameroon

Wum the capital of Men chum Division is an important agricultural area in the Northwest Region in Cameroon vital for the food security of the country. The study objective was to determine and evaluate the seasonal variations during four hydrogeological seasons; dry (March), drywet (June), wet (September) and wetdry (December) in the groundwater chemistry, groundwater rock interactions and domestic-agro-industrial groundwater quality using hydrogeochemical tools; physicochemical parameters, ionic ratios, gibbs diagrams, piper diagrams, durov diagrams, Total Hardness HT, Water Quality Index WQI, Sodium Adsorption Ratio SAR

Hydrogeology of Abuja FCT-Nigeria: A GIS Evaluation

Groundwater has been recognized as playing a very important role in the development of Abuja FCT Nigeria’s capital, as many private and government establishments depend solely on wells for their water needs. Exploitation of groundwater is delicate due to its potency to contamination and difficulty to remediate aquifers. This study is to evaluate the input of the rock formations to the groundwater solute chemistry and groundwater domestic quality using hydrogeochemical tools and physicochemical parameters: pH, EC, Temperature, TDS, Chloro-alkaline indices, Ionic ratios, Gibbs diagrams, Piper diagrams, Durov diagrams and water quality index. From physicochemical parameters: pH ranged from, 4.8 - 7.9; EC, 13.4 - 1634 μS/cm; Temperature, 26℃ - 36.1℃ and TDS, 17.42 - 1094.78 mg/L. The major ions fell below WHO acceptable limits. The sequences of abundance of major ions were, K > Ca2 > Na > Mg2 for cations and Cl-> HCO3->NO3- >SO42- for anions. Borehole depths range from 19.5 - 34.5 m with static water levels between 3 - 12 m.a.m.s.l. Yields were between 3.2 - 7.2 m3/Hr. Ionic ratios show ninety-five (95%) percent of the groundwater chemistry resulting from chemical weathering of rock-forming minerals through the dissolution of the host rock. The Chloro-alkaline indices: CAI1 87.23% are positive indicating exchange of Na and K from water with Mg and Ca of the rocks and 12.77% are negative, indicating reverse softening of groundwater in rocks by infiltrating rainwater while CAI2 85.11% are positive indicating exchange of Na and K from water with Mg and Ca of the rocks and 14.89% are negative, indicating reverse softening of groundwater in rocks by infiltrating rainwater. Thus chloro-alkaline indices indicate the dominance of alkaline earth elements over alkalis in majority of samples due to direct exchange of Ca2 and Mg2 from the aquifer matrix with Na and K from the groundwater. Gibbs diagram revealed groundwater ionic content was as a result of ion exchange from rock-weathering. Piper diagrams give three water types: 75% are CaHCO3, 21.20% are of MgHCO3 and 3.19% are of Na KHCO3 water types respectively. Piper diagrams also give three hydrogeochemical facies in Abuja FCT: 54.25% are of Ca-Mg-Cl-SO4, 42.56% are of Ca-Mg-HCO3 and 3.19% are of Na-K-Cl-SO4 hydrogeochemical facies respectively. Durov plot shows 20.21% are anion discriminate Ca dominant; mixed water and 63.83% had no dominant ion; simple dissolution. Water quality indices (WQI) values were between ？220 - 180, Total hardness (TH) values were between 0 - 519.12. These WQI and TH values indicate that 69.2% and 47.37% of the groundwater respectively are suitable for domestic purpose. The groundwater in Abuja FCT is acidic to slightly alkaline in nature, soft to moderately hard and of low to high salinity. Major processes controlling the water quality are the weathering of the host rock through mineral dis-solution, cation exchange and inverse cation exchange processes. Ion-exchange, simple dissolution and uncommon dissolution processes determined groundwater character.

Geogenic Imprint on Groundwater and Its Quality in Parts of the Mamfe Basin, Manyu Division, Cameroon

Groundwater studies in parts of the Mamfe basin are sparse and the Mamfe area has the highest population density in the Mamfe basin. An in-depth study of groundwater rock interaction and groundwater quality is of vital importance. This same part of the basin is the economic centre and as such development of businesses in this area requires knowledge of the groundwater quality. Therefore, this study was undertaken to determine the input of the rock formations on the groundwater solute chemistry and groundwater domestic-agro-industrial quality using hydrogeochemical tools and physicochemical parameters: Ionic ratios, Gibbs diagrams, Piper diagrams, Durov diagrams and water quality indices. From physicochemical parameters, in the rainy season, pH ranged from, 4.3 - 8.6; EC, 3 - 1348 μS/cm; Temperature, 24.4℃ - 30.1℃ andTDS, 2.01 - 903.16 mg/L and in the dry season, pH ranged from 5.5 - 9.3; EC, 6 - 994 μS/cm; Temperature, 25℃ - 38.6℃ andTDS, 4.02 - 632.48 mg/L. Forty groundwater samples: 20 per season, wet and dry were analysed. The major ions fell below WHO acceptable limits for both seasons. The sequences of abundance of major ions were: Ca2+ > K+ > Mg2+ > > Na+, Cl- > > > > NO3 in wet season and Ca2+ > Mg2+ > K+ > Na+, > Cl- > > > in dry season. Ion-exchange, simple dissolution and uncommon dissolution processes determined groundwater character. Groundwater ionic content was as a result of ion exchange from rock-weathering. Water types are: CaSO4 and MgHCO3 in both seasons. Hydrogeochemical facies are Ca-Mg-Cl-SO4 and Ca-Mg-HCO3. SAR for wet season 0.05 - 0.06 and dry season 0.00 - 0.05, %Na wet season 3.64 - 16.59 and dry season 1.22 - 10.97, KR wet season 0.01 - 0.02 and 0.00

Seasonal Variations in Groundwater of the Phreatic Aquiferous Formations in Douala City-Cameroon: Hydrogeochemistry and Water Quality

This study was to determine the seasonal variations of groundwater, the influence of the rock formations on the groundwater solute chemistry and groundwater domestic-agro-industrial quality using hydrogeochemical tools and physicochemical parameters; Ionic ratios, Gibbs diagrams, Piper diagrams, Durov diagrams and water quality indices. From physicochemical parameters; in the rainy season, pH ranged from, 4.6-7.1; EC, 0.023-1.63 mS/cm; Temperature, 26.3-290C andTDS, 0.015-1.09 mg/L and in the dry season pH ranged from 5-7.2; EC, 0.01-1.61 mS/cm; Temperature, 24.4-29.50C andTDS, 0.01-1.08 mg/L. Forty groundwater samples; 20 per season, wet and dry were analysed. Themajor ions fell below WHO acceptable limits for both seasons. The sequences of abundance of major ions were, Ca2 >K >Mg2 >NH4 >Na , HCO3->Cl->SO42->NO3->HPO42- in wet season and Ca2 >Mg2 >K >Na >NH4 , HCO3->Cl->SO42->HPO42->NO3- in dry season. Ion-exchange, simple dissolution and uncommon dissolution processes determined groundwater character. Groundwater ionic content was as a result of ion exchange from rock-weathering. Water types are; MgCl and MgHCO3 in both seasons. Hydrogeochemical facies are; Ca-Mg-Cl-SO4, characteristic of groundwater some distance along its flow path and Ca-Mg-HCO3, characteristic of freshly recharged groundwater from precipitation. The groundwater indices of; Sodium Percent (% Na), Residual Sodium Carbonate (RSC) , Kelley’s ratio (KR), Sodium Adsorption Ratio (SAR), Electrical Conductivity (EC), Total Dissolved Solid (TDS), USSL and Wilcox index were determined, evaluated and found to be suitable for agro-industrial uses in all seasons. Permeability Index (PI) , Water quality index (WQI) and Magnesium Adsorption Ratio (MAR) were not suitable in some areas and in some seasons.

Processes of water–rock interactions and their impacts upon the groundwater composition in Assiut area, Egypt: Applications of hydrogeochemical and multivariate analysis

Ion exchange, dissolution and precipitation represent the effective hydrogeochemical processes water-rock interactions. They play a great role in the form of changes in the hydrogeochemical composition of the groundwater in the Pleistocene, Plio-Pleistocene, and Eocene aquifers in Assiut area. Their impacts upon groundwater composition are investigated by applying the conventional hydrogeochemical tools and confirmed by the multivariate statistical treatments. The hydrogeochemical indices are used for investigating the actual changes in the chemical composition of the groundwater and their extents. Statistical multivariate analysis of the factors and principal components are used for investigating the effective loading of groundwater. They confirm the obtained results by applying the hydrogeochemical indices. The results indicate that dissolution and precipitation play the essential control on the groundwater composition in the Pleistocene aquifer around the Nile, while ion exchange is more effective in controlling the water composition in the Plio-Pleistocene and Eocene aquifers in Assiut area. The present work enables for assessment of the hydrogeochemical regime of the aquifer systems in Assiut area. It provides good understanding of natural and man-made factors which execute the processes of water-rock interactions and controlling the groundwater composition and suitability for different uses.

Groundwater Monitoring in the Gneisso-Basaltic Fractured Rock Aquiferous Formations of Kumba, Southwest Region Cameroon: Seasonal Variations in the Aqueous Geochemistry and Water Quality

The objective was to determine and monitor seasonal changes during four hydrological seasons: Wet season (September), Wetdry season (December), Dry season (March) and Drywet season (June) in the groundwater aqueous geochemistry and its domestic-agro-industrial quality using physicochemical parameters and hydrogeochemical tools: Temperature, Electrical Conductivity EC, pH, Total dissolved solids TDS, Ionic ratios, Gibbs diagrams, Piper diagrams Durov diagrams, total hardness HT, Water quality index WQI, Sodium adsorption ratio SAR, Percent Sodium %Na, Kelly’s Ratio KR, permeability index PI, Magnesium adsorption ratio MAR, Residual sodium carbonate RSC and Wilcox diagram. Field physicochemical parameters ranged from: Wet season; pH 3.9 - 6.9; Temperature, 23.3°C - 29.1°C; EC, 10 - 1900 μS/cm; TDS, 6.7 - 1273 mg/L; Wetdry, pH, 5.7 - 11.7; Temperature, 23.6°C - 28.3°C; EC, 1 - 1099 μS/cm, TDS, 0.67 - 736.33 mg/L; Dry pH, 5.7 - 13.1; Temperature, 26.3°C - 30.2°C; EC, 12 - 770 μS/cm, TDS, 8.04 - 515.9 mg/L and Drywet, pH, 4 - 7.4; Temperature, 25.8°C - 30.7°C; EC, 10 - 1220 μS/cm, TDS, 6.7 - 817.4 mg/L. Seventy-two groundwater samples, 18 per season were analysed. All ionic concentrations fell below acceptable World Health Organization guidelines in all seasons. The sequence of abundance of major ions are; Wet, Ca+ > Mg2+ > Na+ = K+ > NH4+, HCO3? > Cl? > NO3? > SO42? > HPO42?; Wetdry Ca+ > K+ > Mg2+ > Na+ > NH4+, HCO3? > Cl? > SO42? > NO3? > HPO42?; Dry Ca+ > K+ > Mg2+ > Na+ > NH4+, HCO3? > Cl?> NO3? > SO42? > HPO42?; Drywet NH4+ > Ca+ > K+ > Mg2+ > Na+; Cl? > HCO3? > NO3? > SO42? > HPO42?. Groundwater ionic content was due to rock weathering and ion exchange reactions. CaSO4 is the dominant water type in Wet and Wetdry seasons; followed by CaHCO3, Na + K-Cl Wet, CaSO4 and CaHCO3 Wetdry; MgCl Dry and Drywet followed by CaCl, CaHCO3 Dry and CaSO4, CaHCO3 Dry-Wet. The dominant hydrogeochemical facies are Ca-Mg-Cl-SO4 followed by Na-K-SO4 Wet and Ca-Mg-HCO3? in all other seasons. Ion exchange, Simple dissolution and uncommon dissolution are the processes determining groundwater character. The water quality indices; WQI, HT, SAR, %Na, KR, PI, MAR,RSC and Wilcox diagrams, indicate that groundwater in Kumba is 80% - 100% excellent during the Drywet &Wet seasons, 5% - 10% unsuitable during the Wetdry & Dry seasons for domestic use while being excellent-good for Agro-Industrial uses in all other seasons. Physicochemical parameters in some areas exceeded permissible limits for drinking. All hydrogeochemical parameters vary with seasons and these variations show the impact of annual cycles of seasonal changes on the aqueous geochemistry of groundwater in Kumba.

Hydrogeochemical Model and Water Quality of Groundwater in the Granito-Basaltic Fractured Rock Aquiferous Formations in Bafoussam, West Region-Cameroon

This study determined the hydrogeochemical model of groundwater and groundwater domestic-agro-industrial quality in Bafoussam using hydrogeochemical tools and physicochemical parameters: Ionic ratios, Gibbs diagrams, Piper diagrams, Durov diagrams and water quality indices. From physicochemical parameters; pH ranged from, 4.47 - 7.84; EC, 10 - 820 μS/cm; Temperature, 22.3°C - 29.5°C and TDS, 6.7 - 549.4 mg/L. The major ions fell below WHO acceptable limits. The sequences of major ionic abundance are: Ca2+ > Mg2+ > K+ > Na+ > NH+4, HCO-3 > Cl- > SO2-4 > NO3 > HPO2-4. Recharge by atmospheric precipitation, ion-exchange and simple dissolution processes are responsible for groundwater character, ionic content resulted from ion exchange and rock-weathering. Water types are Ca-HCO3 and Ca-Cl Hydrogeochemical facies are Ca-Mg-Cl-SO4 and Ca-Mg-HCO3. Domestic water quality was determined by use of pH, electrical Conductivity EC, total dissolved solids TDS, total Hardness HT and water quality index WQI. WQI values ranged from 0 - 42.09 and HT 67.89 - 339.01 indicating that water is of good domestic quality. Agro-industrial suitability of groundwater was determined using, sodium adsorption ratio SAR, permeability index PI, Magnesium adsorption ratio MAR, percent sodium %Na, Kelly’s ratio KR and Residual sodium carbonate RSC and Wilcox diagram; From irrigational water suitability parameters, SAR values ranged from 0.01 - 0 05; %Na 3.69 - 15.50; KR 0.005 - 0.023; PI 1.04 - 67.98; MAR 2.89 - 55.27; RSC -5.22 to -0.44 and Wilcox diagram indicate that inorganic groundwater content in the study area is excellent-good for irrigation; this is of significance since Bafoussam a major agroindustrial zone in Cameroon and Central Africa is in the process of developing large scaled irrigation based agricultural projects dependent on use of surface and groundwater. Recharge from precipitation exchanges ions with the weathered country rocks and mixes with regional flow in a generally south-east north-westerly direction by piston flow in the granito-basaltic aquiferous formations in Bafoussam. There is need for detailed studies to determine aquifer characteristics: permeability, transmissivity and storativity, vertical-lateral regional extent of aquifer boundaries, groundwater pollution potentials for biological, organic and trace metals.

Assessing major factors affecting shallow groundwater geochemical evolution in a highly urbanized coastal area of Shenzhen City, China

Groundwater is the most important alternative drinking water source in the coastal urban area of Shenzhen City, China. Understanding the main geochemical factors affecting groundwater chemistry is vital for sustainable water resource management in the long term. Seawater intrusion has been a serious problem, but the situation seems to have recently improved with the establishment of a water supply system and land reclamation. However, total dissolved solids (TDS) concentrations in the groundwater have increased. To determine major factors controlling groundwater geochemical evolution, studies were carried out in the area in Shenzhen most vulnerable to seawater intrusion. Along the groundwater flow path from the bedrock outcrop area to the coastal plain, groundwater evolution processes were studied using multiple hydrogeochemical analyses. Piper plots and hydrochemical facies evolution diagrams show the aquifer vulnerable to seawater intrusion is currently dominated by fresh groundwater of Ca-HCO3 or Ca-Na-HCO3-Cl type; only a few locations close to Shenzhen Bay appear to be Na-Cl type, indicating the threat of seawater intrusion. Anthropogenic pollution is mainly characterized by elevated NO3− and NH4+ in the form of point sources. Correlation coefficient analysis to evaluate water-rock interactions during granite weathering indicates this process can contribute significant amounts of Ca2+, Mg2+, Na+, K+, and HCO3– to groundwater. Evaluation of the aggressiveness index (AI), Langelier saturation index (LSI), and Ryznar stability index (RSI) suggest all groundwaters are corrosive and the dissolution of concrete material foundations in urban areas contributes significant amounts of Ca2+ and SO42− to groundwater. Principal components analysis (PCA) demonstrates water-rock interactions and concrete material dissolution are more important factors than seawater intrusion in terms of affecting shallow groundwater chemistry. This study demonstrates that hydrogeochemical tools are effective in assessing groundwater evolution under the influence of multiple factors in a highly urbanized coastal area.

Tackling the salinity-pollution nexus in coastal aquifers from arid regions using nitrate and boron isotopes.

Salinization and nitrate pollution are generally ascertained as the main issues affecting coastal aquifers worldwide. In arid zones, where agricultural activities also result in soil salinization, both phenomena tend to co-exist and synergically contribute to alter groundwater quality, with severe negative impacts on human populations and natural ecosystems' wellbeing. It becomes therefore necessary to understand if and to what extent integrated hydrogeochemical tools can help in distinguishing among possible different salinization and nitrate contamination origins, in order to provide adequate science-based support to local development and environmental protection. The alluvial plain of Bou-Areg (North Morocco) extends over about 190km2 and is separated from the Mediterranean Sea by the coastal Lagoon of Nador. Its surface is covered for more than 60% by agricultural activities, although the region has been recently concerned by urban population increase and tourism expansion. All these activities mainly rely on groundwater exploitation and at the same time are the main causes of both aquifer and lagoon water quality degradation. For this reason, it was chosen as a case study representative of the typical situation of coastal aquifers in arid zones worldwide, where a clear identification of salinization and pollution sources is fundamental for the implementation of locally oriented remedies and long-term management strategies. Results of a hydrogeochemical investigation performed between 2009 and 2011 show that the Bou-Areg aquifer presents high salinity (often exceeding 100mg/L in TDS) due to both natural and anthropogenic processes. The area is also impacted by nitrate contamination, with concentrations generally exceeding the WHO statutory limits for drinking water (50mg/L) and reaching up to about 300mg/L, in both the rural and urban/peri-urban areas. The isotopic composition of dissolved nitrates (δ15NNO3 and δ18ONO) was used to constrain pollution drivers. The results indicate two main origins for human-induced pollution: (i) manure and septic effluents, especially in urban areas, and (ii) synthetic fertilizers in agricultural areas. In the latter, δ15N-enriched values highlight a mixture of those sources, possibly related to unbalanced fertilization and agricultural return flow. Boron isotopes (δ11B) were hence studied to further distinguish the nitrate origin in the presence of multiple sources and mixing processes. The results indicate that in the study area, the high geochemical background for B and Cl, associated to the complex water-rock interaction processes, limit the application of the coupled δ11B and δ15N isotopic systematics to the detection of sources of groundwater pollution. In fact, despite the exceedingly high nitrate contents, the depleted δ11B values that characterize synthetic fertilizers and sewage leakages could not be detected. Therefore, even if in saline groundwater the anthropogenic contribution has a negligible effect in terms of salinity input, with both sewage and irrigation water not very charged, the associated nitrate content fuels up water-rock interaction processes, eventually leading to a mineralization increase.

Characterization of Recharge Mechanisms and Sources of Groundwater Salinization in Ras Jbel Coastal Aquifer (Northeast Tunisia) Using Hydrogeochemical Tools, Environmental Isotopes, GIS, and Statistics

Groundwater is among the most available water resources in Tunisia; it is a vital natural resource in arid and semiarid regions. Located in north-eastern Tunisia, the Metline-Ras Jbel-Raf Raf aquifer is a mio-plio-quaternary shallow coastal aquifer, where groundwater is the most important source of water supply. The major ion hydrochemistry and environmental isotope composition (δ18O, δ2H) were investigated to identify the recharge sources and processes that affect the groundwater salinization. The combination of hydrogeochemical, isotopic, statistical, and GIS approaches demonstrates that the salinity and the groundwater composition are largely controlled by the water-rock interaction particularly the dissolution of evaporate minerals and the ion exchange process, the return flow of the irrigation water, agricultural fertilizers, and finally saltwater intrusion which started before 1980 and which is partially mitigated by the artificial recharge since 1993. As for the stable isotope signatures, results showed that groundwater samples lay on and around the local meteoric water line LMWL; hence, this arrangement signifies that the recharge of the Ras Jbel aquifer is ensured by recent recharge from Mediterranean air masses.

Erratum to: Geophysical, isotopic, and hydrogeochemical tools to identify potential impacts on coastal groundwater resources from Urmia hypersaline Lake, NW Iran.

Erratum to: Geophysical, isotopic, and hydrogeochemical tools to identify potential impacts on coastal groundwater resources from Urmia hypersaline Lake, NW Iran.