Source Of Salinity Research Articles

Influences of natural salinity sources and human actions on the Shapour River salinity during the recent streamflow reduction period.

The Shapour River, with a catchment area of 4254 km2, is a major river system in southern Iran. While the upstream river flow (the upper Shapour River) is fresh, it becomes extremely salinized at the downstream confluence of the Shekastian saline tributary and the entering nearby Boushigan saline spring. Then, the river passes via the Khesht plain and finally discharges into Raeisali-Delvari storage dam which went into operation in 2009. Over the 2006-2019 period, reduced precipitation and over-utilization of freshwater resources resulted in ~ 72% streamflow reduction in the Shapour River. Due to not using the saline waters for irrigation, drinking, and industrial purposes, the ratio of saline-outflow of Shekastian tributary and Boushigan spring to fresh-outflow of upper Shapour River increased by ~ 3 times; consequently, river salinity fluctuation domain at the Khesht plain inlet dramatically increased from 2.1-4.0 dS m-1 to 3.7-26.0 dS m-1. It resulted in major economic damages to the agricultural sector of middle Shapour River. On the seasonal timescale, consecutive processes of salt accumulation during irrigation season of the Khesht plain date orchards and then salt drainage during the rainy season have adjusted salinity fluctuation domain from 3.7-26.0 dS m-1 at the plain inlet to 5.2-8.9 dS m-1 at the plain outlet. In the lower Shapour River, storage/mixing of fresh/saline inflow waters in the Raeisali-Delvari reservoir has adjusted strong river salinity fluctuation domain from 0.9-10.7 dS m-1 at the reservoir inlet to 3.6-5.5 dS m-1 at the reservoir outlet. The success of the Raeisali-Delvari reservoir for salinity adjustment is due to its suitable location on the Shapour River, by being situated downstream of all main river tributaries with natural saline/fresh sources of water.

Similarities and distinctions in the genesis of salt-affected soils in different regions of the south of Eastern Siberia

Soil salinization is determined by a set of factors, which can be subdivided into sources and mechanisms. The south of Eastern Siberia is characterized by the mountainous topography with numerous intermontane depressions, a large number of tectonic faults and springs. Hydromorphic surface-saline soils of sulfate and chloride-sulfate chemistry predominate. In Tuva, the share of chloride salinity increases, which is associated with the presence of salt rocks, and the percentage of soda-saline soils decreases sharply. In Buryatia, the percentage of soda salinity is higher than in other regions. In Khakasia, despite the gypsum deposits, the percentage of soda-saline soils is also significant, which is related to irrigation practices. Sharper differences are observed in individual basins of the regions, the salinity of which is determined by the presence of salinization sources in the given area, as well as by the mechanisms and conditions of soil salinization. For example, the presence of permafrost prevents the leaching of chlorides from the profile leading to the development of chloride salinization, or an increase in the alkalinity associated with the magnesium bicarbonate in slightly arid intermontane depressions of Buryatia and high–mountain depressions of Tuva.

ISOLATION OF SEAWEED ASSOCIATED BACTERIA'S AND THEIR PRODUCTION OF BIOPOLYMER BY SOLID-STATE FERMENTATION

Plastic material is any of a wide range of synthetic or semi-synthetic organic solids that are moldable. Plastics are typically organic polymers of high molecular mass, but they often contain other substances. They are usually synthetic, most commonly derived from petrochemicals, but many are partially natural. Environmental pollution by the disposal of non-degradable conventional plastics is a fast-growing problem worldwide, especially in India. Nowadays, plastics are replacing by other constructional materials like glass, wood, metal in numerous applications. In this study, there has been considerable interest in the development and production of biodegradable polymer to solve the current problem of pollution caused by the continuous use of synthetic polymer from seaweed associated Bactria. . Based on the dry weight of total biopolymer content, the strain SBT 09 showed maximum accumulation and selected for optimizing at different pH, temperature, salinity, carbon, and nitrogen source and the peak time of PHB accumulation. Based on the biochemical tests, the strain SBT 09 was found.The optimum pH, temperature, and salinity were found to be 7, 300C, and 5%. The peak time of PHB accumulation was found to be 36hrs. The best carbon and nitrogen source was found to be sucrose and (NH4)2 HPO4. The selected strain was mass cultured using the optimized media and PHB was extracted by solvent extraction. Keywords: Marine Bacteria, PHB, Biosynthesis, Biopolymer.

Behaviour of flotation tailings from a rare earth element deposit at high salinity

Various rare earth element (REE) deposits hosted by carbonatite complexes have been identified in southern (Montviel, Niobec) and northern Quebec (Eldor deposit). During the winter in Quebec, the use of road salts to facilitate transportation on the mine site and/or avoid water freezing during mine operation may be necessary. The sources of salinity can be diverse on a mine site: process water, precipitation, alteration of minerals in the soil. Thus, tailings may come in contact with these salts and react. The purpose of the present study was to evaluate the impact of salinity on the behaviour of flotation tailings (Eldor deposit), i.e. the mobility of the elements contained in the tailings under these conditions and the environmental risks involved. For this purpose, leaching column tests were developed. The solutions were deionized water (CW column), NaCl (25 g/L; CS1 column) and CaCl2 (25 g/L; CS2 column). The leachate analysis revealed that the divalent cations (Ba, Cd, Mg, Mn, Sr, and Zn) are more mobile in the presence of CaCl2 (CaCl2 > NaCl > deionized water). The mobility of these elements appears to be governed by the competition with Ca2+ for tailings sorption sites. U and Sc are most mobile in the presence of salts regardless of the applied salt solution, i.e. CaCl2 = NaCl > deionized water. The formation of soluble chloride complexes with these elements could therefore be the cause of this phenomenon. For S, the leaching solution has no impact on its mobility. In conclusion, the presence of salts would tend to increase the mobility of divalent cations present in these residues and enhance their contamination potential. Modeling using PHREEQC software allowed comparison of these results with post-dismantling mineralogical characterization. Both methods showed: (i) total dissolution of fluorite [CaF2], galena [PbS], richterite [Na(CaNa(Mg,Fe2+)5[Si8O22](OH)] and Ba silicate; (ii) precipitation of iron oxides/hydroxides and silicate minerals. However, the modeling was unable to predict the behaviour of carbonate minerals. Further modeling tests involving kinetics should be considered in a future study.

Optimization of constant-current operation in membrane capacitive deionization (MCDI) using variable discharging operations

Membrane capacitive deionization (MCDI) is an emerging electric field-driven technology for brackish water desalination involving the removal of charged ions from saline source waters. While the desalination performance of MCDI under different operational modes has been widely investigated, most studies have concentrated on different charging conditions without considering discharging conditions. In this study, we investigate the effects of different discharging conditions on the desalination performance of MCDI electrode. Our study demonstrates that low-current discharge (1.0 mA/cm2) can increase salt removal by 20% and decrease volumetric energy consumption by 40% by improving electrode regeneration and increasing energy recovery, respectively, while high-current discharge (3.0 mA/cm2) can improve productivity by 70% at the expense of electrode regeneration and energy recovery. Whether discharging electrodes at the low current or high current is optimal depends on a trade-off between productivity and energy consumption. We also reveal that stopped flow discharge (85%) can achieve higher water recovery than continuous flow discharge (35–59%). However, stopped flow discharge caused a 20–30% decrease in concentration reduction and a 25–50% increase in molar energy consumption, possibly due to the higher ion concentration in the macropores at the end of discharging step. These results reveal that an optimal discharging operation should be obtained from achieving a balance among productivity, water recovery and energy consumption by varying discharging current and flow rate.

Unveiling the extent of salinization to delineate the potential submarine groundwater discharge zones along the North-western coast of India

The North-West coast of India was notable for the urbanization and semiarid climate, particularly the Gujarat coastal region which was facing water crises and aquifer salinization issue. Under the light of these critical issues, the present study investigates the sources of aquifer salinization and probable location of submarine groundwater discharge (SGD) using an integrated approach of major ion chemistry, statistical techniques, and isotopic signature of groundwater (GW). The evolution of GW reveals that water facies changes from Ca2+-Mg2+-Cl− to Na+-Cl type from the south Gujarat towards the Gulf of Khambhat. Log-normal distribution of Cl− and NO3− divulges that different pollution sources influence the GW quality. Statistical findings supplemented with Isotopic signatures, ionic ratios and cross plots identified four classes of GW, which varies with degree of anthropogenic and seawater influences. Results suggested that seawater intrusion heavily influences 42% of the total GW samples, whereas 58% samples showed the probability of SGD. The study recommends the feasible locations of check dams as a remedial measure for controlling the salinization of coastal aquifer.

Use of various statistical techniques to assess the vertical and lateral change in the groundwater chemistry of Quaternary aquifer in an irrigated highly populated area

A large Hydrogeochemical data were obtained from the central Nile delta aquifer system where 167 groundwater samples were gathered from three depth zones and analyzed for majors and minors. Different statistical techniques were applied to the analyzed geochemical data. The target of the current investigation is to find the principle factors and processes controlling the variation in the hydrogeochemistry in the three groundwater zones. The physicochemical analysis revealed that concentrations of majors (K, Na, Ca, Mg, HCO3, Cl and SO4) with some traces as NO3, Si, NH4 and Fe decrease from the shallow zone to reach its lowest values in the deep zone because of the surface hydrologic and anthropogenic factors affect the shallow groundwater. The studied groundwater classified into five series, every series has its own hydrochemical type. It is revealed that the shallow groundwater was affected by surface hydrochemical process, soil salinity and water–rock interaction as main sources of groundwater salinity. There are two origins of the deep groundwater, one is fresh flowing from south to north and the other is influenced by the intruded seawater in the northern part of the investigated region. The groundwater of the intermediate zone is a mix between the shallow groundwater and the deep groundwater.

Fingerprinting sources of salinity in a coastal chalk aquifer in Denmark using trace elements

Salinity levels above the drinking water standard (>250 mg/l Cl–) are observed at shallow depth in a Maastrichtian chalk aquifer on the island of Falster, south-eastern Denmark. To understand the source of the salt, 63 samples from 12 individual, 1 m, screened intervals between 14 and 26 m b.s. were collected from 1 May to 4 June 2018. The samples were collected during a tracer test to estimate the dual porosity properties of the chalk and were analysed for a wide range of elements. Furthermore, samples from the Baltic Sea and from deeper saline aquifers in the area (40 and 85 m b.s.) were analysed for comparison. The geochemical data were analysed using an unsupervised machine-learning algorithm, self-organising maps, to fingerprint water sources. The water composition in the screened intervals at various stratigraphic levels has specific geochemical fingerprints that are maintained for the first days of pumping and are distinct amongst the different levels. This suggests an evolution in water composition because of reaction with the chalk. Water composition is distinct from both seawater from the nearby Baltic Sea and salty water from deeper levels of the reservoir. Thus, neither up-coning of salty water nor intrusion of seawater caused the elevated salinity levels in the area. The slightly saline composition of groundwater in the shallow aquifer (14–26 m b.s.) is more likely because of incomplete refreshing of the salty connate water in the chalk during the Pleistocene and Holocene. Furthermore, the geochemical fingerprint of salty water from the deeper aquifer at 40 m was similar to water from the Baltic Sea, suggesting a Baltic Sea source for salt in the aquifer at 40 m b.s., c. 100 m from the coast. Statistical analysis based on self-organising maps is an effective tool for interpreting a large number of variables to understand the compositional variation in an aquifer and a useful alternative to linear dimensionality-reduction methods such as principal component analysis. The approach using the multi-element analysis combined with the analysis of self-organising maps may be useful in future studies of groundwater quality.

Natural and anthropogenic sources of salinity in the Awash River and Lake Beseka (Ethiopia): Modelling impacts of climate change and lake-river interactions

Study region: Awash River Basin, Ethiopia: Study focusMany river basins in sub-Saharan Africa have become vulnerable due to the impact from climate change, weak governance and high levels of poverty. One of the primary concerns is the elevated salinity and the degradation of water quality in the Awash River. Located in the Great Rift Valley in Ethiopia, the Awash River has unique hydrochemistry due to water-rock interactions. However, in recent years, increasing anthropogenic activities including the discharge from saline Lake Beseka into the Awash River has caused some concern. This study used an Integrated Catchment Model to simulate chloride concentration in the Awash River Basin by taking both natural and anthropogenic sources of salinity into consideration. Future scenarios of climate change and Lake Beseka discharge were examined to assess the impact to the river water quality. New hydrologic insightsResults show that Lake Beseka has made significant contribution to the rise of the salinity in the Awash River. If the trend of human interference (e.g. increased irrigation and unregulated water transfer) continues, the river downstream of Lake Beseka could see Cl increases up to 200 % in the near future (2006–2030). The modeling results are essential for generating long term plans for proper utilization of water resources especially in the region where the resources and the economic capacity to meet the water demand is lacking.

Potential Impacts of Shale Gas Development on Inorganic Groundwater Chemistry: Implications for Environmental Baseline Assessment in Shallow Aquifers

The potential contamination of shallow groundwater with inorganic constituents is a major environmental concern associated with shale gas extraction through hydraulic fracturing. However, the impact of shale gas development on groundwater quality is a highly controversial issue. The only way to reliably assess whether groundwater quality has been impacted by shale gas development is to collect pre-development baseline data against which subsequent changes in groundwater quality can be compared. The objective of this paper is to provide a conceptual and methodological framework for establishing a baseline of inorganic groundwater quality in shale gas areas, which is becoming standard practice as a prerequisite for evaluating shale gas development impacts on shallow aquifers. For this purpose, this paper first reviews the potential sources of inorganic contaminants in shallow groundwater from shale gas areas. Then, it reviews the previous baseline studies of groundwater geochemistry in shale gas areas, showing that a comprehensive baseline assessment includes documenting the natural sources of salinity, potential geogenic contamination, and potential anthropogenic influences from legacy contamination and surface land use activities that are not related to shale gas development. Based on this knowledge, best practices are identified in terms of baseline sampling, selection of inorganic baseline parameters, and definition of threshold levels.

Freshwater–Saltwater Interactions in a Multilayer Coastal Aquifer (Ostia Antica Archaeological Park, Central ITALY)

An integrated research approach consisting of hydrogeologic and geochemical methods was applied to a coastal aquifer in the Ostia Antica archaeological park, Roma, Italy, to describe freshwater–saltwater interactions. The archaeological park of Ostia Antica is located on the left bank of the Tevere River delta which developed on a morphologically depressed area. The water monitoring program included the installation of multiparametric probes in some wells inside the archaeological area, with continuous measurement of temperature, electrical conductivity, and water table level. Field surveys, water sampling, and major elements and bromide analyses were carried out on a seasonal basis in 2016. In order to understand the detailed stratigraphic setting of the area, three surface boreholes were accomplished. Two distinct circulations were identified during the dry season, with local interaction in the rainy period: an upper one within the archaeological cover, less saline and with recharge inland; and a deeper one in the alluvial materials of Tevere River, affected by salinization. Oxygen and carbon isotopic signature of calcite in the sediments extracted from the boreholes, along with major elements and Br concentration, allowed us to recognize the sources of salinity (mainly, local interaction with Roman salt pans and agricultural practices) and the processes of gas–water–rock interaction occurring in the area. All these inferences were confirmed and strengthened by PCA analysis of physicochemical data of groundwater.

Geochemical and isotopic evidence of groundwater salinization processes in the Essaouira region, north-west coast, Morocco

The city of Essaouira is located along the north-west coast of Morocco, where groundwater is the main source of drinking, domestic and agricultural water. In recent decades, the salinity of groundwater has increased, which is why geochemical techniques and environmental isotopes have been used to determine the main sources of groundwater recharge and salinization. The hydrochemical study shows that for the years 1995, 2007, 2016 and 2019, the chemical composition of groundwater in the study area consists of HCO3–Ca–Mg, Cl–Ca–Mg, SO4–Ca and Cl–Na chemical facies. The results show that from 1995 to 2019, electrical conductivity increased and that could be explained by a decrease in annual rainfall in relation to climate change and water–rock interaction processes. Geochemical and environmental isotope data show that the main geochemical mechanisms controlling the hydrochemical evolution of groundwater in the Cenomanian–Turonian aquifer are the water–rock interaction and the cation exchange process. The diagram of δ2H = 8 * δ18O + 10 shows that the isotopic contents are close or above to the Global Meteoric Water Line, which suggests that the aquifer is recharged by precipitation of Atlantic origin. In conclusion, groundwater withdrawal should be well controlled to prevent groundwater salinization and further intrusion of seawater due to the lack of annual groundwater recharge in the Essaouira region.

Evaluating the predictive power of different machine learning algorithms for groundwater salinity prediction of multi-layer coastal aquifers in the Mekong Delta, Vietnam

Groundwater salinization is considered as a major environmental problem in worldwide coastal areas, influencing ecosystems and human health. However, an accurate prediction of salinity concentration in groundwater remains a challenge due to the complexity of groundwater salinization processes and its influencing factors. In this study, we evaluate state-of-the-art machine learning (ML) algorithms for predicting groundwater salinity and identify its influencing factors. We conducted a study for the coastal multi-layer aquifers of the Mekong River Delta (Vietnam), using a geodatabase of 216 groundwater samples and 14 conditioning factors. We compared the predictive performances of different ML techniques, i.e., the Random Forest Regression (RFR), the Extreme Gradient Boosting Regression (XGBR), the CatBoost Regression (CBR), and the Light Gradient Boosting Regression (LGBR) models. The model performance was assessed by using root-mean-square error (RMSE), coefficient of determination (R2), the Akaike Information Criterion (AIC), and Bayesian Information Criterion (BIC). The results show that the CBR model has the highest performance with both training (R2 = 0.999, RMSE = 29.90) and testing datasets (R2 = 0.84, RMSE = 205.96, AIC = 720.60, and BIC = 751.04). Ten of the 14 influencing factors, including the distance to saline sources, the depth of screen well, the groundwater level, the vertical hydraulic conductivity, the operation time, the well density, the extraction capacity, the thickness of the aquitard, the distance to fault, and the horizontal hydraulic conductivity are the most important factors for groundwater salinity prediction. The results provide insights for policymakers in proposing remediation and management strategies for groundwater salinity issues in the context of excessive groundwater exploitation in coastal lowland regions. Since the human-induced influencing factors have significantly influenced groundwater salinization, urgent actions should be taken into consideration to ensure sustainable groundwater management in the coastal areas of the Mekong River Delta.

Saline-Resistant Paddy Macronutrient Content Response to The Saline Source Distance

The impact of salinity on paddy production in Indonesia was pronounced with an average decline of 6.83% (2015-2019). Salinity interferes with macronutrients' absorption into plants, causing stunted growth (salinity contributed to a 42% decrease in paddy production). One solution to solve the salinity problem in paddy is to use saline varieties. There were very few studies on macronutrient content analysis in resistant varieties response to the salinity source's distance. This research conducted in Jabon Sidoarjo, Indonesia, aims to see the macronutrient response and plant growth to the saline source's distance. This research was conducted in Jabon District, Sidoarjo Regency, using two transects with a length of 2 km and 3.4 km, respectively. The distance between the research location and the salinity source was 10.65 km. The survey used a free grid to adjust paddy fields' location and the presence of resistant varieties. The results showed that the closer to the salinity source, the salinity indicators consisting of Electrical Conductivity, Sodium Adsorption Ratio, Exchangeable Sodium Percentage, and pH H2O would increase. The increase in salinity then affects the decrease in macronutrients (Nitrogen, Phosphor, and Kalium) in plants. However, tillers and leaves (length and number) were unaffected by high salinity levels in the soil.

Abundance, community structure and diversity of nitrifying bacterial enrichments from low and high saline brackishwater environments

The study reports diversity in nitrifying microbial enrichments from low (0·5-5‰) and high (18-35‰) saline ecosystems. Microbial community profiling of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) enrichments was analysed by sequencing 16S rRNA and was processed using Mothur pipeline. The α-diversity indices showed the richness of nitrifying bacterial consortia from the high saline environment and were clustering based on the source of the sample. AOB and NOB enrichments from both the environments showed diverse lineages of phyla distributed in both groups with 38 and 34 phyla from low saline and 53 and 40 phyla in high saline sources, respectively. At class level, α- and γ-proteobacteria were found to be more dominant in both the enrichments. AOBs and NOBs in enrichments from low saline environments were dominated by Nitrosomonadaceae, Gallionellaceae (Nitrotoga sp.) and Ectothiorhodospiraceae and Nitrospira, respectively. Though Chromatiaceae were present in both AOB and NOB enrichments, Nitrosoglobus and Nitrosococcus dominated the AOBs while NOBs were dominated by uncultured genera, whereas Rhizobiales were found in both the enrichments. AOBs and NOBs in enrichments from high saline environments were dominated by Nitrospira-like AOBs, Nitrosomonas and Nitrosococcus genera, whereas ammonia-oxidizing archaea (AOA) group included Nitrosopumilus and Nitrososphaera genera comprising and Nitrospirae, respectively. The majority of the genera obtained in both the salinities were found to be either uncultured or unclassified groups. Results of the study suggest that the AOB and NOB consortia have unique and diverse microbes in each of the enrichments, capable of functioning in aquaculture systems practised at different salinities (0-60ppt).

Addressing the contribution of indirect potable reuse to inland freshwater salinization

Inland freshwater salinity is rising worldwide, a phenomenon called the freshwater salinization syndrome (FSS). We investigate a potential conflict between managing the FSS and indirect potable reuse, the practice of augmenting water supplies through the addition of highly treated wastewater (reclaimed water) to surface waters and groundwaters. From time-series data collected over 25 years, we quantify the contributions of three salinity sources—a water reclamation facility and two rapidly urbanizing watersheds—to the rising concentration of sodium (a major ion associated with the FSS) in a regionally important drinking-water reservoir in the Mid-Atlantic United States. Sodium mass loading to the reservoir is primarily from watershed runoff during wet weather and reclaimed water during dry weather. Across all timescales evaluated, sodium concentration in the reclaimed water is higher than in outflow from the two watersheds. Sodium in reclaimed water originates from chemicals added during wastewater treatment, industrial and commercial discharges, human excretion and down-drain disposal of drinking water and sodium-rich household products. Thus, numerous opportunities exist to reduce the contribution of indirect potable reuse to sodium pollution at this site, and the FSS more generally. These efforts will require deliberative engagement with a diverse community of watershed stakeholders and careful consideration of the local political, social and environmental context. Freshwater salinization syndrome is an emerging threat to freshwater globally. Here the authors quantify the contribution of indirect potable reuse to sodium pollution and suggest a variety of behavioural and technological interventions to address this growing environmental problem.

Quantification of surface water and groundwater salinity sources in irrigated lowland area of North China Plain

AbstractSeasonally variation of water salinity is observed worldwide, the mechanisms of water salinity are not well understood due to natural factors and anthropogenic activities. Quantification water salinity source are challenging since complex influence factors, especially in agricultural regions irrigated with multi‐water sources. In the lowland area of North China Plain, transferred water, brackish shallow groundwater and fresh deep groundwater were combinative utilized to relieve prominent contradictions between regional water shortages and grain production. In this study, influence factors of surface water (canal water, pond water) and shallow groundwater salinity were identified and quantified through statistical analysis, deuterium excess, and ionic relationship. Salinity of canal water and pond water increased in dry season and decreased in rainy season, while salinity of shallow groundwater decreased in dry season after water transfer and rainy season, but increased in dry season. Evaporation and mineral dissolution were main factors for surface water salinity in dry season, with mineral dissolution was the more important one. The contribution ratio of evaporation and mineral dissolution for canal salinity were 4.4 and 49.1% in dry season after water transfer, 7.1 and 34.4% in dry season, and that for pond water salinity were 12.4 and 18.3% in dry season, respectively. Precipitation and surface runoff were main factors for surface water salinity in rainy season. The contribution of surface runoff for canal water and pond water salinity were 66.1 and 45.8%, respectively. Salinity of canal water and shallow groundwater was temporary decreased by water transfer. Domestic sewage from rural areas had larger influence than agricultural activities for salinity increase of pond water and shallow groundwater. Mineral dissolution was the main contributor for shallow groundwater salinity, with contribution ratio larger than 60% in different periods. This study demonstrated and quantified salinity source of surface water and shallow groundwater and may deepen our understanding of water management under multi‐water resources utilization.

Hydrogeochemical Characterization as a Tool to Recognize “Masked Geothermal Waters” in Bahía Concepción, Mexico

Geo-thermalism has been widely recognized on the Baja California Peninsula, especially during the last decade. The current research, carried out on Bahia Concepcion, evidences the existence of geothermal springs, which get recharged mainly by groundwater and seawater. The groundwater can be characterized as Na+-Cl− and Na+-HCO3− type, with a pH value close to neutrality. The slightly more acidic thermal sites presented temperatures between 32 °C and 59 °C at the surface. Based on the relationships of the Cl− and Br−, as well as the B/Cl−, and Br−/Cl− ratios, seawater was recognized as the main source of salinity. The spatial distribution is explained directly through marine intrusion, or via sprays and aerosols within the rainwater. Seawater ratios in thermal springs varied from 62% to 83%, corresponding mainly to shallow inflow, but seawater inputs into the deep thermal reservoir were also recognized. Temperatures in the geothermal deep reservoir were inferred from 114 to 209 °C, calculated through the SiO2 and Na+-K+ geothermometers. In addition to previously reported thermal sites at Bahía Concepción, and based on their elevated temperatures, two new sites were identified. Another five springs do not fulfill the commonly used definition, based on differential temperature, but show the typical hydrogeochemical signature of thermal water. A new approach to identify this low-temperature geothermal-influenced spring water by its hydrogeochemical composition is presented, for which the term “Masked Geothermal Waters” (MGW) is introduced. Our findings increase the area of the geothermal anomaly and, therefore, the potential of geothermal resources. The approach proposed in this research will also be useful to identify more MGW in other coastal areas.

Groundwater Chemical Characteristics and Salinization Mechanism in the Coastal Plain of the South Bank of Laizhou Bay

Based on 59 groundwater samples which were collected on the south bank of Laizhou Bay, the main ionic ratios analysis and the main ionic Piper three-line diagram was done. The results show that from offshore to nearshore, groundwater hydrochemical is mainly freshwater, brackish water, salt water, and brine. And the ion type transforms from HCO3-Ca to HCO3·Cl-Ca, then converted to HCO3·Cl-Na and further transformed into Cl·HCO3-Na, then changed to Cl-Na regularity. By calculating some conventional water ion ratios which include Na/CL, K/CL, Ca/CL, SO4/CL, the hydrogeochemical effects of water-rock interactions, the source of groundwater salinity and the mechanism of groundwater salinization were investigated in this study. The anion-cation exchange reaction in the groundwater of the brackish water transition zone in the northern part of the monitoring section is more obvious than that in the southern underground freshwater. The main hydrogeochemical processes occurring in the brackish water transition zone are the dissolution of minerals (calcite, anhydrite and rock salt), precipitation of gypsum and dissipation of carbon dioxide. And the main cation exchange in this area is Ca-Na exchange.

Possible Sources of Salinity in the Upper Dibdibba Aquifer, Basrah, Iraq

Salinity increase in groundwater was investigated in the area between Al-Zubair and Safwan, and close to the Khor Al-Zubair Channel of southern Iraq. Thirty-nine groundwater samples from the shallow aquifer and one sample from the Khor Al-Zubair Channel were analyzed. The mean total dissolved solids are 7556 mg/L. The δ2H and δ18O plot in two groups are below the global meteoric water line. Group A indicates the evaporation effect of irrigation return-flow, while group B is characterized by depleted δ18O values due to recharge under colder climate. Deuterium excess values plot within the region of modern precipitation and dilution of groundwater by precipitating water. The groundwater residence time is between 1000 and 2000 years and combining 14C -age with SO42− shows a contrasting effect on groundwater on both sides of Khedr Almai Fault and the Zubair anticline, which indicates the role of these geological structures on the hydrochemical evolution in the western part. Jabal Sanam shows no clear effect in this regard. The ratio Cl−/Br− and sulfate in groundwater showed that the measured salinity in groundwater is the result of a mixing process between groundwater, seawater intruding from Khor Al-Zubair Channel, and water from septic tanks in addition to dry and wet sea spray, and irrigation return-flow.