Origin Of Groundwater Salinity Research Articles

Salinity origin in the coastal aquifer of the Southern Venice lowland

Groundwater salinization can be natural and anthropogenic in origin, although it often results from a combination of both, especially in low-lying coastal regions that are hydraulically controlled. This study proposes a method to assess the origin of salinity using environmental tracers in porewater, like Cl− and Br−, combined with depositional facies associations detected in sediment cores. Such integrated approach was tested in a target area south of the Venice Lagoon (Italy), where groundwater salinization is triggered by multiple mechanisms due to the complexity of the hydro-geomorphological environment. Batch tests were performed on sediment core samples from boreholes to quantify major anions and total inorganic N. Cl− and Br− porewater concentrations coupled with sedimentary facies association provided insights into the origin of groundwater salinity from a variety of sources, including past and present seawater intrusion, agricultural leaching, and evaporites. The strengths and limitations of the integrated approach are discussed to provide a pathway for improving water resource management and planning measures to prevent groundwater salinization in coastal areas.

Mechanism of Salinization of Shallow Groundwater in Taocheng District, Hengshui City

In order to understand the characteristics and origin of groundwater salinization in Taocheng district of Hengshui City, the recharge and salinization procession of shallow groundwater were analyzed with isotopic and geochemical data of the shallow groundwater (buried depth ≤ 100 m) and the soluble salt in boreholes. The results showed that the shallow groundwater was weak alkaline salt water, with the total dissolved solid (TDS) in the groundwater ranging from 176.06 to 17569.65 mg·L-1and the soil total salinity in unconsolidated sediments ranging from 1.830 to 6.509 g·kg-1. The hydrochemical types were mainly SO4·Cl-Na·Mg and Cl·SO4-Na·Ca in the shallow groundwater and the soluble salt. The main recharge resource of shallow groundwater was precipitation with different geological periods. The hydrochemical compositions of shallow groundwater mainly came from the dissolution of halite and sulfate weathering and experienced intense evaporation and the reduction environment. Meanwhile, the groundwater salinization was barely affected by human activities and seawater intrusion.

Origin of Groundwater Salinity in the Draa Sfar Polymetallic Mine Area Using Conservative Elements (Morocco)

In the Marrakech region of Morocco, where water resources are particularly limited, excessive salinity has been measured in the water from some wells intended for human consumption and irrigation. Moreover, the start-up of a mine for the exploitation of a polymetallic sulfide deposit and the progress of the exploitation work have revealed the existence of very saline deep groundwater with a total mineralization of over 80 g/L. The hydrogeochemical study using conservative elements has helped to understand the origin of the groundwater salinity in the Draa Sfar mine and to assess the contribution of the deep salinity source to the high salinities observed in the mine. The groundwater of the shallow aquifer shows almost constant Br−/Cl− and Na+/Cl− ratios, independent of the chloride content. The constant ratios of these conservative elements indicate a single autochthonous origin of Cl−, Br− and Na+, and groundwater salinity is diluted by recharge water containing low concentrations of these elements. Regarding the mine groundwater, the high Li+/Cl− ratio and Br−/Cl− ratios in the range measured on the leachates of the rocks extracted from the mine indicate that the pore water is the reservoir for dissolved chloride and the salinity of the mine’s groundwater results from a mixture between these pore waters and fresh meteoric water that seeps in from the surface and recharges the entire aquifer. This porewater would be a remnant of the hydrothermal fluids that formed the sulfide deposit.

The origin of groundwater salinity in the Matanza-Riachuelo aquifer system, Argentina

Groundwater salinization is a severe worldwide issue affecting many coastal aquifers by threatening their freshwater resources (Werner et al., 2013; Michael et al., 2017). The Matanza-Riachuelo River Basin (MRRB) is a coastal-continental basin that supplies fresh water to the Greater Buenos Aires conurbation, encompassing approximately 10% of Argentina's population. Among other environmental degradation issues, salinization is one of the most important processes affecting the MRRB. In this study, salinization across the MRRB was unraveled using major (Cl, HCO3, SO4, Na, Ca, Mg) and tracer (Br) solutes, together with stable (18O, 2H, 13C) and radioactive isotopes (3H, 14C). Three different saline end-members were identified: Upper Basin Slightly Saline (UBSS), Lower Basin Highly Saline (LBHS), and Lower Basin Hyper Saline (LBHPS). The salinity of the UBSS and the LBHPS end-members was associated with the Miocene Paraná Formation connate marine water, while the salinity of the LBHS end-member were associated with the Pleistocene to Holocene Postpampeano Sediments connate seawater. The estimated 14C values were related to travel time differences in the flow paths delivering water to different zones of the Puelche Aquifer. Groundwater in the upper basin sector of the Puelche Aquifer was likely to belong to long, regional groundwater flow recharged outside the MRRB boundary. Groundwater in the top of the Puelche Aquifer at the lower basin comes from the Upper Aquifer through vertical transfer. This study contributes to a better understanding of (1) salinization processes linked to connate marine water of different ages in the Matanza-Riachuelo Aquifer System and (2) different sources of flow paths delivering groundwater to the upper and lower sectors of the confined Puelche Aquifer. The knowledge generated from this study can help to understand groundwater salinization processes in other aquifer systems around the world and support groundwater management plans across the MRRB.

Delineating the origins and processes of groundwater salinization and quality degradation in a coastal irrigated plain, Korba (Northeastern Tunisia)

From 2006 to 2020, groundwater investigations were conducted in the Korba coastal aquifer in northern Tunisia along two flow paths (transects S1 and S2), perpendicular to the shoreline. Groundwater sampling, hydrodynamic monitoring, and electrical tomography imaging were performed in situ. Geochemical analysis (Ionic ratios, ionic deltas, conventional diagrams, and stable isotopes) and modelling using PHREEQC, and multivariate statistical analysis were applied. The objective was to identify the potential origin of groundwater salinization (i.e., high TDS and NO3) and to study associated processes.The groundwater flow inversion was corroborated by the piezometric survey in transect S1, where a piezometric depression of 5 m was detected at 4000 m from the seashore. Seawater intrusion and agricultural contamination, mainly through N-fertilizers, both contribute to groundwater mineralization and consequently salinization, according to PCA analysis. The impacted geochemical area of seawater intrusion was estimated to be 4000 and 1500 m, respectively, along transect S1 and transect S2. Inversely, agricultural contamination acts in internal areas beginning at 2000 m and 1500 m from the shoreline for S1 and S2, respectively. Results of different scenarios of inverse geochemical modelling along flow paths indicated that mixing, ion exchange, dissolution of gypsum, and precipitation of dolomite and calcite are the main processes controlling the groundwater composition in the coastal study area.

Chemo-isotopic tracing of the groundwater salinity in arid regions: An example of Shahrood aquifer (Iran)

Understanding the origin of groundwater salinity is critical to efficiently manage the scarce water resources in arid regions. In the current research, the source and mechanism of groundwater salinity in the Shahrood aquifer, central Iran, have been assessed using combination of hydrochemical techniques and environmental isotopes. A total of 115 groundwater samples were collected and analyzed for the major and minor ions (HCO3, Cl, SO4, Ca, Mg, Na, K, Br and I) and isotopes (δ18O and δ2H). Based on the results of the chemical approach, halite and gypsum dissolution, Na-silicate weathering and calcite precipitation induced by common-ion effect are the main source of salinity (>7500 mg/L) in the saline water zone (SWZ) of the Shahrood aquifer. The SWZ groundwaters are more depleted in δ2H as compared with fresh water zone (FWZ) samples which plotted on the Shahrood local meteoric water line (SMWL). Development of a groundwater divide line at the central parts of the aquifer causes low velocity and then enhancing the residence time of the SWZ groundwaters mainly originated from isotopic-depleted sub-modern precipitations in surrounding high-elevated mountains. Mixing water zone (MWZ) is identified between FWZ and SWZ, where the relative fractions of the saline groundwaters vary in the range of 23–99%. Managing groundwater withdrawals is highly recommended; as the groundwater over-exploitations enhance invasion of the saline groundwaters from SWZ and then overall degradation of the water quality in the aquifer. This is the first model explaining the groundwater salinity source and mechanism of the Shahrood aquifer as a case of mountain-front recharged plain aquifer, providing guidelines for salinity assessments in other arid-land aquifers around the world.

Assessing groundwater salinity across Africa

In Africa groundwater is the principal source of drinking water (https://washdata.org/) and has significant potential to improve food production as a source of irrigation water. Although volumes of stored groundwater are high when compared to surface water, not all the available groundwater is suitable for irrigation. One of the principal factors that limit the development of groundwater is salinity, but quantitative evidence regarding the scale of salinization in Africa has been lacking. This paper presents an initial analysis of the extent of groundwater salinization in Africa, bringing together groundwater salinity data (n = 12,255) from across the continent. In our dataset c.80% of the samples have electrical conductivity values less than 2000 μS/cm. Samples with high conductivity values of more than 2000 μS/cm are restricted to limited geological and climatic environments. The data reveals salinity does not affect the water security status of most countries in Africa. However, salinity compounds water insecurity issues in arid low groundwater recharge environments. The paper discusses the role of anthropogenic processes such as river valley water resources development, extensive groundwater pumping, inter-basin groundwater transfer, and irrigation in altering the salinity of groundwater bodies. The paper further elucidates the origin of groundwater salinity by critically reviewing the natural and human-induced factors that control the salinization of the various groundwater bodies across Africa. Existing case studies reveal several causes of salinization, including i) human-induced salinization, ii) climate and hydrological change-induced paleo groundwater salinity, iii) rock dissolution, and iv), saltwater encroachment.

Origin of Groundwater Salinization in the Osis of Béni Abbès (Saoura Valley, South-West Algeria)

The aquifer of the alluvial terraces of the Béni Abbès palm grove is subject to a hyperarid climate. The groundwater salinity problem is caused by several human and natural factors, causing serious irrigation problems. Hydrochemical analyses over a 40-year interval show an alarming Spatio-temporal evolution of salinity: the drying up of the Saoura valley due, on the one hand, to the impact of the construction of the Djorf Torba dam, on the other hand to the strong evaporation which

Hydrogeochemical processes controlling the groundwater salinity in the coastal aquifers of Southern Tamil Nadu, India

The current study identifies groundwater quality issues and investigates the most important geochemical processes that control seawater intrusion using various ionic ratios, hydrochemical facies evolution, and geochemical modelling. Cl-/Br ratio is an important indicator to identify the origin of groundwater salinity in coastal aquifers. Nineteen percent of the groundwater samples with Cl−/Br− ratio similar to that of Standard Mean Ocean Water (SMOW) are affected by seawater intrusion in the study area. Particularly, nine groundwater samples have high chloride values and are similar to SMOW, and it may derived salinity from seawater sources from the Bay of Bengal due to the over-pumping of production wells in the Uvari zone. Five samples are similar to SMOW, which is due to the presence of salt pan activities. The bivariate plots such as Ca2+ + Mg2+ vs Cl−, EC vs Cl−, and Na+/Cl− ratio indicate that seawater intrusion is the primary source for groundwater salinisation. Evaporation is the dominant process controlling groundwater chemistry, rather than rock-water interaction and precipitation, according to mechanisms controlling groundwater chemistry. Direct ion exchange and converse ion exchange are the critical controlling factors for groundwater salinisation, according to the hydrochemical facies evolution diagram (HFED). The water quality index (WQI) shows that most groundwater belongs to the poor to the marginal category. The saturation indices show that the groundwater samples are saturated with minerals such as dolomite, calcite, aragonite and magnesite. Therefore, these minerals are susceptible to precipitation due to the effective leaching of calcareous minerals from the bedrocks. Compiled hydrogeochemical analysis and multivariate statistical analysis revealed that the Tiruchendur and Uvari zone was affected by the seawater intrusion and led to an increase in the salinity of the groundwater.

Identifying the origin of groundwater salinization in the Bokoya massif (central Rif, northern Morocco) using hydrogeochemical and isotopic tools

The recurrent drought in the Rif region, Northern Morocco, and specifically the Bokoya massif, has led to significant exploitation of groundwater to meet human and socio-economic objectives. In this context, a hydrochemical, geochemical, and isotopic tools has been carried out to determine the origin of dissolved elements and the processes contributing to the increase in salinization of groundwater. To achieve this objective, physico-chemical analyses of the water were carried out on 96 samples (81 wells and 15 springs), taken April 2018. The results show that the groundwater samples studied are characterized by a medium to high salinity, which can exceed 8000 μS/cm. Spatial distribution of physico-chemical parameters are consistent with the distribution of the rocks from Triassic formations. Our results also show that the salinization is probably due to the dissolution of evaporate rocks and ion exchange with precipitation of carbonate minerals such as calcite and dolomite. The stable isotope contents vary from −6.69 to −4.84‰ for δ18O and −42.6 to −30.1‰ for δ2H, indicating an altitude of recharge for most of the springs between 350 and 750masl. Exceptions to this are likely to have recharged from the flysch of Tizirene at altitudes higher than 1000masl, and following an altitudinal gradient of 0.27‰ per 100 m.

Assessing salinization of coastal groundwater by tidal action: The tropical Wouri Estuary, Douala, Cameroon

Study regionDouala, Cameroon, West Africa. Study focusSalinity of shallow coastal groundwater in Douala, Cameroon impairs its use for drinking and industrial purposes. Previous studies suggest that salinization is from tidal flooding from the Wouri Estuary. We aimed to test the tidal origin of groundwater salinization by conducting a time series investigation of water level and salinity, and assessed the stable water isotopes (δ¹⁸O and δD) and major cations (Ca²+ and Mg²+) in groundwater and adjacent estuarine tidal creek. During the time series measurements, we pumped groundwater for over 5 tidal cycles to induce flow into a test well. New hydrologic insights for the regionThe time-series groundwater level mimicked water level changes in the estuary. However, the temporal salinity in groundwater did not correspond to tidal salinity changes of estuarine water, indicating that estuarine water did not intrude groundwater. The δ¹⁸O and δD of the groundwater and estuarine samples are collinear and fall along the local meteoric water line of Douala and had d-excesses of >10, indicating a non-evaporated rain recharge of groundwater or lack of salinization by evapoconcentration. The salinity-δ¹⁸O relationship showed that the origin of salinity in the coastal groundwater aquifer is not from seawater intrusion. The Mg²+/Ca²+ ratios of <1 in groundwater compared to 6–8 in estuarine water support the non-seawater origin of groundwater salinity. We conclude that the salinity of coastal groundwater in Douala is not affected by tide-induced salinization from the adjacent Wouri Estuary but by geogenic sources in the aquifer.

Identifying sources of groundwater salinity and major hydrogeochemical processes in the Lower Kabul Basin aquifer, Afghanistan.

The Kabul Basin aquifer is the main source of water for domestic, agricultural and industrial use in Kabul city. Identifying the main hydrogeochemical processes and source of salinity is crucial for groundwater management. In this study, the results of 41 groundwater samples from the Lower Kabul Basin (LKB) aquifer were evaluated using major hydrogeochemical processes and hierarchical cluster analysis (HCA) methods. The electrical conductivity (EC) concentrations ranged from 672 to 15 290 μS cm-1 with a mean value of 1428 μS cm-1. The high spatial variations of EC in the LKB aquifer are due to different sources of salinity in groundwater. The results show that the Mg-(Ca, Na)-HCO3 water type is the dominant hydrogeochemical facies in the aquifer, followed by Mg-(Na)-Cl-(SO4), Na-(Mg)-SO4-(Cl), Na-Cl and Mg-Cl water types. The major factors controlling groundwater chemistry in the aquifer are the dissolution of carbonate, gypsum anhydrate minerals, weathering of silicates, ion exchange and mixing. Based on Cl/Br ratios, dissolution of minerals, anthropogenic and urban effects, and evaporitic lacustrine deposits are the possible sources of salinity in the aquifer. According to Cl/Br ratios and hierarchical cluster analysis, the evaporitic lacustrine deposits are the main source of salinity in the aquifer. The new groundwater survey also confirms the findings. The Cl/Br ratios and HCA successfully identified the sources of salinity in the LKB aquifer. The results of this study can provide a basis for local decision makers to develop effective and sustainable groundwater resources and environmental management strategies for Kabul city.

Evolutionary process of saline groundwater influenced by palaeo-seawater trapped in coastal deltas: A case study in Luanhe River Delta, China

Coastal aquifers provide fresh drinking water to over 20% of the world's population. In recent times, they have come under immense pressure due to salinization. This study aims to investigate the origin of groundwater salinity and elucidate the major processes controlling shallow groundwater (depth of 0–50 m) evolution in the Luanhe River Delta since the Holocene. Rapid increase in Electric Conductivity (EC) profile was observed in the area, as such, based on the vertical distribution of EC and sedimentary history, shallow groundwater was generalized into two zones for analysis: the groundwater in Holocene stratum (HSG) and groundwater in Late Pleistocene stratum (PSG). The isotopic (δ 18O, δ 2H and 14C) analyses showed that the HSG is recharged by modern surface water, while the PSG having enriched isotopic values could have been recharged during a warmer Holocene transgression period. The hydrochemistry analyses demonstrated that seawater is the major source of salinity in groundwater and over time a series of geochemical processes (mineral weathering and/or cation exchange) modified the chemistry of the groundwater. The combined use of Cl− and δ 18O yielded four classes of groundwater (fresh water, brackish water, saline water and brine), while the mixing phenomena between fresh water and seawater was identified to be the main evolutionary process of the shallow groundwater. To improve understanding of evolution of multiple groundwater types in a spatial context, a conceptual model was developed integrating the results derived from the presented study in a vertical cross-section. The conceptual model shows that the residual seawater mixes with freshwater from surface recharge at the shallow aquifer of the delta plain where the lagoon environment provides salinity concentration conditions for the formation of hyper-saline water. Due to the precipitation and accumulation of the salinity from hyper-saline water, some brine might form formed in late Pleistocene continental stratum. In addition, the submarine groundwater discharge may be mainly from deeper inland fresh groundwater, but it is not significantly affected by the hyper-saline water from the shallow aquifer in Luanhe River delta.

Impact of human activities on coastal groundwater pollution in the Yang-Dai River plain, northern China.

Overexploitation of groundwater has resulted in seawater intrusion in many semiarid and arid coastal areas. This study illustrates the origin of groundwater salinity and assesses seawater intrusion/extrusion process in the Yang-Dai River plain aquifer, by analyzing hydrochemical and stable isotopic compositions of surface water, groundwater, geothermal water, and seawater. A cone of depression in groundwater is caused by intensive groundwater pumping formed in the late 1980s in the alluvial Yang-Dai River plain. In the northern part, groundwater exploitation has caused seawater intrusion identified by Ca-Cl type water. However, the widely distributed silty clay prevented the seawater intrusion in the southern part, evidenced by Ca-HCO3 type water with depleted δ2H (-60 to -46‰) andδ18O (-8.9 to -4.7‰). Anthropogenic pollution also plays a significant role in groundwater salinization. The positive correlation between Cl and NO3- for most groundwater and the extremely high nitrate concentrations (up to 652.7 mg/L) indicate that fertilizer from agricultural activities has greatly influenced groundwater quality. Irrigation return flow evaporation during agricultural activities also accounts for groundwater salinity. Besides the intensive fertilizer usage, seawater intrusion and the established anti-tide dams reduced the surface water and groundwater discharge to the sea and then resulted in the extremely high nitrate concentration. This study may improve the understanding of the groundwater salinization processes in a complex coastal aquifer, which is greatly influenced by anthropogenic activities.

Iodine-129 for determining the origin of salinity in groundwater in Pampanga, Philippines

Assessing groundwater vulnerability from salinity contamination is vital and relevant to meet the increasing demand for freshwater. Iodine-129 (129I, half-life = 15.7 million years), a radioisotope of iodine, was used as an environmental tracer for the possible origin of salinization in groundwater (e.g., natural rock weathering, evaporated water, seawater, brine fossil water, contamination). In July 2017 (wet season), thirty-two (32) water samples were taken from production wells of different localities in Pampanga, a province in the Philippines that relies heavily on groundwater for freshwater sources. Hydrogeochemical (mainly Cl) and stable water isotopes (δ2H and δ18O) were able to identify seven samples potentially affected by seawater intrusion. The salinity origin of these samples was investigated using iodine-129 and iodine-127 isotopes by generating two graphs: 129I vs. chloride and 129I/127I ratio vs. 1/127I. 129I vs. Cl graph was capable of showing a clear distinction between different salinity origins. Five out of the seven samples were being affected by evaporated water, one sample from possible wastewater, and one sample from brine fossil water. A conceptual model was produced to summarize the results. Compiled end-members (e.g., natural brine, seawater, modern rain) were plotted in the 129I/127I ratio vs. 1/127I graph to show the interaction between two recharge sources. The results of this study will be helpful to the government, civil society, and other organizations for monitoring, policymaking, and management of the groundwater and the subsurface formations that will be crucial to continuously supply the freshwater needs of the present and future generation.

Alterations to groundwater chemistry due to modern water transfer for irrigation over decades

After a long-term surface irrigation in the southern edge of the Chinese Loess Plateau, the local groundwater is diluted to some extent, which differs from most of the other surface irrigation systems. Identifying the origin of groundwater salinity and determining the implications of irrigation can provide insights into the sustainable development of irrigation systems. In this study, a comprehensive investigation of groundwater, river water, canal water, and irrigation system was conducted. Our results suggest that the irrigation activities produce significant influence on the hydrochemistry of both river and groundwater. In the north-eastern part of the study area, hydrochemistry types are mainly HCO3-Na and HCO3∙SO4-Na types which is recharged by the river replenished by water transfer for irrigation. In the south-western part, groundwater is mainly HCO3-Na·Mg type which largely directly receives canal water recharge. The correlation between the irrigation water volume and the salinity variation confirms that mixing with fresh irrigation water which was derived from the reservoirs and the canals, during the irrigation period, dilutes the local groundwater. The natural hydrogeochemical processes of the loess aquifer suggest that the water-rock interactions and cation exchange process supply the excessive Na+ and other solutes to the groundwater, resulting HCO3-Na type water with high salinity. Additionally, the slow Groundwater flow and poor hydrologic cycle between the groundwater and the scarce rainfall promote natural salts accumulation. The δ18O and δD values indicate that modern rainfall may only account for small part of recharge to groundwater. In contrast, the irrigation water, as well as the canal and the reservoir seepage, contribute to a large proportion of groundwater recharge. The finding is beneficial for the policy-makers for the future water management schemes, in large surface irrigation systems, in order to achieve sustainable development goal.

Indications that weathering of evaporite minerals affects groundwater salinity and As mobilization in aquifers of the northwestern Hetao Basin, China

Elevated arsenic (As) concentration and salinity (TDS > 1000 mg/L) seriously affect the groundwater quality in the Hetao Basin, China, however, the origin of groundwater salinity and its influence for As mobilization has not been widely studied. In this study, the influence of evaporite minerals weathering on groundwater salinity and As mobilization were investigated by lithological and mineralogical analysis of sediments from two boreholes in combination with groundwater hydrogeochemical characteristics analysis in the northwestern Hetao Basin. Results from a water-leaching method suggest that Na and Ca related sulphates dominate the evaporite minerals in sediment samples. Groundwater salinization mainly results from evaporation and Na+/Ca2+ cation exchange followed by sulphate and silicate minerals weathering. Saturated indices for calcite, dolomite and unsaturated indices for gypsum as well as negative correlation between pH and SO42- suggest that groundwater chemistry does not reach equilibrium with continual carbonates precipitation by an excessive Ca supply from Ca related sulphates weathering. The groundwater pH decrease and Ca2+ release during weathering of Ca related sulphates can retard As desorption from Fe (oxyhydr)oxides and clay minerals. Furthermore, pyrite minerals were also found in the sediments induced by high sulphide flux and it can cause As sequestration. However, modeling results suggest the occurrence of thio-As species in the study area, which can potentially enhance the As mobilization. This study contributes to the ongoing research into As mobilization in the groundwater of lacustrine basins.

Origin of groundwater salinity in the Fasa Plain, southern Iran, hydrogeochemical and isotopic approaches

The study area, the Fasa Plain, is situated in the semiarid region of Fars Province in the south of Iran. The Salloo diapir is a salt dome that crops out in the northwest of the study area. Isotopic and hydrochemical analyses were used to examine the water and how the origin of salinity and the diapir affect the quality of the groundwater quality in the study area. Groundwater was sampled from 31 representative pumping wells in alluvial aquifer and five springs in order to measure their stable isotope compositions, bromide ion concentration, and physical and chemical parameters. The alluvial aquifer was organized into two main groups based on the chemistry, with Group 1 consisting of low-salinity well samples (544–1744 µS/cm) with water type Ca–Mg–HCO3–SO4 which were taken in the center and north of the area, and Group 2 consisting of high-salinity samples (2550–4620 µS/cm) with water type Ca–Mg–Cl–SO4 which were taken from the wells in the south and southwest of the area. A saline spring near the salt dome with an EC of 10,280 µS/cm has water type Na–Cl, while the compositions of the water in the other karstic springs is comparable to the fresh groundwater samples. All groundwater samples are undersaturated with respect to gypsum, anhydrite, and halite and are supersaturated with respect to calcite and dolomite. Stable isotopes (δ18O and δ2H) differentiated four water types: saline springs, freshwater spring, fresh groundwater, and saline groundwater. The results indicate that meteoric water is the main origin of these water resources. Halite dissolution from the salt dome was identified as the origin of salinity. The Na/Cl and Cl/Br ratios confirmed the results. Groundwater compositions in the southwestern part of the area are affected by the intrusion of saltwater from the salt dome. The average saltwater fraction in the some water wells is about 0.2%. In the south and southwestern part of the area, the saltwater fraction is positive in mixed freshwater/saltwater (Group 2). Different processes interact together to change the hydrochemical properties of Fasa’s alluvial aquifer. The main processes that occur in the aquifer are mixing, gypsum dissolution, and calcite precipitation.

The dynamics and origin of groundwater salinity in the northeast Hufu Plain

The aim of this research is to identify the dynamic characteristics and origins of groundwater salinity in the Hufu Plain. Samples of groundwater were taken from wells throughout the Hufu Plain. Geochemical analyses using integrated ionic ratios with a variety of graphical approaches, saturation indices, and the GIS method were performed to distinguish the sources of groundwater salinity. The results indicated that the groundwater can be classified into five main types. The cation and anion trends were Ca2+ > Na+ > Mg2+ > K+ and HCO3 − > SO4 2− > Cl− > NO3 −, respectively. Groundwater quality in the Hufu Plain is influenced by the chemical weathering of rock-forming minerals. The variation in saturation indices for different minerals indicated that groundwater salinization was controlled to some degree by human activities in the Hufu Plain. Groundwater salinity is not only governed by mineral weathering and dissolution (such as calcite, aragonite, dolomite, and gypsum) but also significantly influenced by anthropogenic inputs (such as fertilizer, pesticide, and sewage irrigation). Groundwater salinity originates mainly from the dissolving of gypsum and anhydrite and from anthropogenic inputs rather than from the weathering, precipitation, and dissolution of calcite, dolomite, and aragonite.

Origin of groundwater salinity and hydrochemical processes in an unconfined aquifer: case of Yang-Dai River basin in Qinhuangdao (China)

Groundwater salinization has become a growing concern in Yang-Dai River basin of Qinhuangdao (China) where groundwater is commonly exploited for domestic, industrial and agricultural uses. In this study, hydrochemical and physical parameters of groundwater were analyzed to identify the origin of groundwater salinity and the geochemical processes occurring in the unconfined aquifer. Groundwater types are Ca·Mg–HCO3·SO4 in the hills, Ca·Mg–HCO3·SO4 in the piedmont plain and Na–Cl in the coastal alluvial plain, respectively. Electrical conductivity values varied between 322 and 3990 μS/cm. Chloride concentration attained to 942 mg/L and the proportion of seawater intrusion in the coastal alluvial plain was 5.39 % calculated by seawater fraction formal, displaying the severe seawater intrusion. Cation-exchange reactions and water–rock interactions related to the dilution of halite, gypsum, dolomite and calcite occurred by ionic relationships during seawater intrusion. High nitrate concentrations ranged from 35.6 to 686.5 mg/L distributed in the hills and the south coastal alluvial plain where they are seriously polluted by the industrial wastewater, agricultural fertilizers and domestic sewage. Seawater intrusion and nitrate contamination have common effects on the hydrochemical process in the south coastal alluvial plain. Therefore, the origin of groundwater salinization was attributed not only to seawater intrusion but also to anthropogenic pollution in the study area. This research provides useful information for groundwater salinization and water planning strategies in a coastal area.