Mineral Seawater Research Articles

Magnesium from Deep Seawater as a Potentially Effective Natural Product against Insulin Resistance: A Randomized Trial.

Background and Objectives: Deep seawater has been shown to restore pancreatic function in obese diabetic mice and considerably improve the homeostatic model assessment for insulin resistance, total cholesterol, and low-density lipoprotein cholesterol concentrations in patients with impaired fasting glucose or glucose tolerance. In this study, the effect of 12-week daily consumption of magnesium (Mg2+)-containing deep seawater mineral extracts on blood glucose concentration and insulin metabolism-associated indicators was investigated in patients with impaired glucose tolerance. Materials and methods: In this 12-week randomized, double-blind trial, patients (n = 37) with impaired glucose tolerance consumed deep seawater mineral extracts. Changes in blood glucose concentration and related indicators were compared between the treatment group and placebo group (n = 38). Results: The fasting insulin, C-peptide, homeostatic model assessment for insulin resistance, quantitative insulin sensitivity check index, homeostatic model assessment of beta-cell function, and Stumvoll insulin sensitivity index values in the deep seawater mineral extract group showed improvements compared with the placebo group. However, no significant differences between groups were observed in fasting blood glucose, postprandial blood glucose, glycated hemoglobin, or incremental area under the curve values. Conclusions: Oral supplementation with deep seawater mineral extracts enriched in Mg2+ markedly improves insulin sensitivity in patients with pre-diabetes. This study illustrates the potential clinical application of natural Mg2+ from deep seawater to alleviate insulin resistance in patients with pre-diabetes. Trial registration: This trial was retrospectively registered with Clinical Research information Service (CRIS), No. KCT0008695, on 8 August 2023.

Mechanistic Insights into Electrodeposition in Seawater at Variable Electrochemical Potentials

AbstractThe classical approach to manufacturing cement and concrete involves considerable and energy‐intensive exploitation of minerals from the environment, calling for alternative and sustainable methods to obtain such resources. Electrodeposition resulting from local pH changes near an oxygen or water reduction electrode can be used to grow valuable minerals in seawater for use in the cement and concrete industries, with the potential to use clean electricity without relying on the mining of resources. Limited knowledge is available about the electrochemical reaction networks that yield mineral precipitates via electrodeposition in seawater, hindering a complete assessment of the promise of such an approach to serving the construction industry. This work presents an investigation of the electrodeposition in seawater as a function of the applied potential. The work identifies multiple electrochemical potential regimes that yield distinct polymorphs, quantities, and production rates of calcium and magnesium‐based minerals due to the varying rates of oxygen reduction and water‐splitting reactions. The quality of the produced minerals is comparable to that of traditionally mined aggregates in terms of morphology and composition, supporting that seawater represents a vast source of raw materials for use in the construction industry upon an enhancement in the efficiency of hydroxide‐producing reactions and the reactor design.

Investigation of Minerals Extracted during Seawater Desalination Using Two-Dimensional Correlation Spectroscopy

In this study, mineral components extracted during the desalination process were concentrated and dried, and then identified using energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), infrared (IR), and Raman spectroscopy. For detailed identification, two-dimensional correlation spectroscopy (2D-COS) was also applied to the XRD patterns, IR spectra, and Raman spectra of the minerals obtained from each desalination step. The EDS results confirm the presence of seawater minerals rich in Na+ ions in the first and second extracts, Ca2+ ions are present only in these stages, and Mg2+ ions are abundant in the third and final extracts. The presence of NaCl and MgSO4 minerals in the first to third and final extracts, respectively, was confirmed using XRD patterns. From the IR and Raman spectra, we found that the degree of hydration of SO42−-related extracts decreased as seawater underwent desalination. Furthermore, 2D-COS provides information about the changes in the extracts obtained from the first to final stage. Heterospectral XRD and Raman 2D-COS provides clear assignments for Raman spectra. The use of 2D-COS helps to understand the characteristics of seawater extracts during the desalination process, and provides a better understanding of chemical and structural adaptations within the extract. As a result, this method contributes to an improved understanding of the desalination process and final products.

Sodium metabisulfite as a copper depressant in the selective flotation of copper-molybdenum concentrate using seawater

The main challenge for the selective flotation of copper and molybdenum (Cu-Mo) sulfide minerals in seawater is the formation of colloidal precipitates in strongly alkaline conditions. These precipitates hinder the selective separation of copper from molybdenum minerals in seawater by lowering the floatability of Cu-Mo sulfide minerals. The present study aimed to examine the direct utilization of seawater in the selective flotation of Cu-Mo sulfides. Additionally, the effectiveness of sodium metabisulfite (Na2S2O5) as a copper depressant for selective flotation of Cu-Mo sulfides in seawater was studied under weakly acidic, neutral, and moderately alkaline conditions. A complex Cu-Mo concentrate that largely consisted of chalcopyrite and molybdenite, as well as a tiny amount of pyrite and quartz, was used in the flotation tests. The flotation results revealed that treatment with 3.6 kg/t Na2S2O5 in seawater at pH 5.5 significantly lowered the copper recovery from 97% to 11% and caused a modest reduction in the molybdenum recovery from 98% to 94% with a Cu-Mo separation efficiency of 83%. These flotation results demonstrate that Na2S2O5 treatment in seawater selectively depresses the floatability of copper minerals. Consequently, molybdenum can be separated from copper minerals under a weakly acidic condition in seawater. In addition, this study discusses the effects of various pH conditions and dosages of Na2S2O5. The surface properties of Cu-Mo minerals were studied using X-ray photoelectron and infrared spectroscopies, and a mechanism to explain the selective flotation of Cu-Mo using Na2S2O5 treatment in seawater is proposed.

Nano-mineralogy and growth environment of Fe-Mn polymetallic crusts and nodules from the South China Sea

Fe-Mn polymetallic crusts and nodules from the South China Sea (SCS) consist of submarine ferromanganese (Fe-Mn) oxide precipitates, and represent important marine mineral resource with substantial economic and scientific research value. Previous studies on the SCS polymetallic crusts and nodules were mainly focused on their bulk mineralogy and geochemistry, whilst research on their nanomineralogy is still lacking. In this study, transmission electron microscopy (TEM), Raman spectroscopic mapping, and in-situ micro X-ray diffraction (XRD) analysis were conducted on the nano-mineralogy of the SCS polymetallic crusts and nodules. It is found that the SCS polymetallic crusts and nodules consist mainly of layered/columnar/mottled nano-phase Fe-Mn minerals and detritus such as quartz, feldspar, and clays. Also, an independent Ti mineral phase has been documented, and the mineralogical analysis reveals the transformation from vernadite to birnessite and todorokite. Titanium forms colloidal minerals in seawater and precipitates into the crusts and nodules with other colloids, such as FeOOH and Si-Al. Vernadite and birnessite can be transformed to todorokite with stable structure under sub-oxic conditions. Therefore, the SCS polymetallic crusts and nodules were formed in a short period of sub-oxic environment and diagenetic process, and the transformation can influence the enrichment of Ni and other metals during the crust/nodule growth.

Adopting abundant seawater as green chemical activators for preparing high surface area biochar

Equipping the agricultural waste with new functionality through a green route echoes the spirit of the circular economy by minimizing the environmental impact. We propose herein to adopt abundant seawater as the green chemical activation reagent to prepare high surface area biochar. By this arrangement, the gasification of seawater Na+ ions in the matrix of the beer dregs in the pyrolysis process leaves the porous biochar with a high surface area > 380 m2/g at 800 °C. Pyrolysis temperature plays the determining factor in developing the surface area due to the limited amount of seawater activators compared to the amount used in the conventional chemical activation. By contrast, seawater minerals are mainly responsible for the surface chemistry of biochar. Lastly, carbonization pretreatment is essential to facilitate seawater sodium ions diffusing into the matrix.

Geochemical and isotope constraints on the hydrogeology and geochemistry of the geothermal waters in the Shandong Peninsula, China

Utilization of low-temperature (< 150°C) geothermal waters plays an increasingly important role in the space heating and other direct uses in China, providing an alternative energy source to fossil fuels. In the Shandong Peninsula several local geothermal areas with low temperatures were discovered by drilling over 90 boreholes. The geothermal waters have surface temperatures ranging from 28 to 89°C, pH values between 6.8 and 8.5, and total dissolved solid contents between 150 and 10,000 mg/L. The mobile element systematics (B, Sr, and Cl) and isotope ratios (δ2H, δ18O) reveal that the geothermal waters are predominantly of meteoric origin with occasional minor seawater mixing and/or mineral salt leaching followed by modification through water–rock interactions and mixing with shallow non-thermal groundwaters. By applying multiple mineral-water equilibria geothermometry, higher subsurface water temperatures ranging from 70 to 160°C were obtained indicating conductive cooling and/or mixing with non-thermal groundwater as the geothermal waters ascends to the surface. Two types of geothermal waters were identified in the Shandong Peninsula. The type I geothermal waters are characterized by deep water circulation (∼2–5 km) associated with large and deep faults, low Cl concentrations (57.7–1781 mg/L), variable and often low 14C activity (6.94–82.6 pMC) and 3H activity (< 1–8.3 TU), and reasonably high reservoir temperatures (70–160°C). These results indicate mixing between reacted and “old” water components at depth and modern meteoric water sourced from the surface. The type II geothermal waters are associated with shallower fractures located away from the major granite intrusions. The geothermal waters have a narrow range of 3H activity (5.9–6.9) revealing a modern meteoric origin, whereas the 14C (54.26–131.78 pMC) activity ranges from modern to “old”. This is the result of input from multiple carbon sources rather than the input of only “old” water. The calculated reservoir temperatures (50–160°C) are generally lower than those of the type I geothermal waters and the water commonly display more elevated Cl concentrations (254–5316 mg/L) and a lower degree of water–rock interactions and rock leaching based on the B, Cl, and Sr systematics. Based on these findings, further prospects for geothermal exploration and exploitation may be feasible in the Shandong Peninsula in terms of deeper boreholes that may discharge higher temperature water.

Preparation of magnesium Ferrite-Doped magnetic biochar using potassium ferrate and seawater mineral at low temperature for removal of cationic pollutants

Magnetic biochar has captured a great interest for remediation of environment as an easily separable carbonous adsorbent. Herein, a highly adsorptive magnetic biochar was manufactured through seawater mineral and K2FeO4 co-promoted pyrolysis of jackfruit peel at 300 °C for removal of different cationic pollutants, and characterized by element analysis, FTIR, SEM-EDS, XRD, XPS and so on. MgFe2O4 was generated without external base and a 19.42 emu/g saturation magnetization was achieved. Simultaneously, iron oxides and oxygen containing groups were introduced. The magnetic biochar exhibited 61.30 mg/g, 129.61 mg/g, and 1238.30 mg/g adsorption capacities for Cu2+, methylene blue (MB), and malachite green (MG) at 25 °C, respectively, and remarkably surpassed the corresponding pristine biochar. The adsorption of MB and MG was mainly realized by electrostatic interaction, hydrogen bonding, complexation, and π-π electron-donor–acceptor interaction, and that of Cu2+ was attributed to electrostatic interaction, hydrogen bonding, and complexation.

Investigation of seawater mineral promoted pyrolysis at low temperature for improving the adsorption capabilities of biochar

Naturally abundant seawater mineral was employed to engineer banana pseudostem and bamboo biochars through pyrolysis at different low temperatures for improving their adsorption capabilities for methylene blue (MB) and tetracycline (TC). The adsorption capabilities were greatly enhanced as the biochars were pyrolyzed at 300 °C with 50/1 (mL/g) dosage of seawater to biomass. For instance, the engineered banana pseudostem biochar exhibited 8.00 and 6.54 times higher adsorption capabilities than the corresponding pristine biochar for MB (447.79 mg/g vs 55.96 mg/g) and TC (100.59 mg/g vs 16.75 mg/g) at 25 °C, respectively. The characterization results indicated that a large number of carboxylates, lactone acid salts, and alkoxides were generated on the engineered biochar and a high cation exchange capacity was gained. The adsorption of MB was mainly attributed to cation exchange complying with hydrogen bonding and electrostatic interaction, whereas the adsorption of TC was realized by hydrogen bonding and complexation.

Characterization and acute oral toxicity of concentrated minerals of Pamekasan Madura seawater.

Indonesia is a maritime country with abundant seawater mineral content. One of the regions with the highest salt production is Pamekasan Madura. Minerals are known to have many roles and benefits for our bodies, such as regulating fluid balance and metabolism. Therefore, this study aimed to characterize the physicochemical and microbial properties of concentrated minerals obtained through solvent evaporation and salt deposition for ± 60 days. Acute oral toxicity examination was performed as a first step in determining the safety of concentrated minerals to be used as a raw material for drugs. Based on the test results, the concentrated mineral has a clear yellow color, salty taste, and a bit bitter, odorless, with a pH of 6.6 ± 0.21. Concentrated minerals have high mineral content with levels of potassium, sodium, magnesium, boron, and calcium being 44734.1598 ± 12950.4633, 33192.1198 ± 2699.3419, 8738.1388 ± 100.4894, 2092.5715 ± 60.3224, and 276.9704 ± 13.1133 mg/Kg, respectively. The results of microbiological analysis of untreated concentrated minerals (without antimicrobials or sterilization) showed that the total plate count was within limits, including coliform and Salmonella. However, the total mold and yeast levels exceed the threshold. Based on the results of acute oral toxicity testing, the concentrated mineral is practically nontoxic. With high mineral content and low toxicity, it can be concluded that the concentrated minerals from Pamekasan Madura seawater is potential to be used as a raw medicinal material.

Chemical and isotopic constraints on the origin of saline waters from a hot spring in the eastern coastal area of China

The Jimo hot spring in Shandong Peninsula, China, is a typical coastal geothermal system. The geothermal water has a very high salinity (10.8 g/L) and the origin of the salt is key to utilization of this geothermal resource. A systematic investigation of the hydrochemistry and isotopes (δ11B, 87Sr/86Sr, δ18O, δD, 13CDIC and 14CDIC) of water from 14 geothermal wells was conducted. The results show that the geothermal waters from the high-temperature center and eastern part of the geothermal field are Cl-Na·Ca-type waters with Br/Cl (8 × 10−4–1.0 × 10−3), Na/Cl (0.63–0.70) and δ11B values (15.9–17.2‰) that are lower than those of seawater. The western geothermal waters are dominated by Cl-Na-type waters with Br/Cl and Na/Cl values similar to those of seawater. The depleted δD and δ18O compositions and the corrected 14CDIC age suggest that Jimo geothermal waters are mixtures of late Pleistocene to early Holocene and younger meteoric waters. An improved Br/Cl-Na/Cl diagram, ion mass balance calculations and δ11B values indicate that halite and K-salt dissolution and subsequent cation exchange formed the dominant Cl-Na·Ca-type geothermal water, and this was then modified into a small amount of Cl-Na-type water in the western area by mixing with minor seawater entrapped in the unconsolidated sediments. The 87Sr/86Sr ratios (0.710613–0.710726) of the geothermal waters reflect water–rock reactions in the sandstone. The improved Br/Cl-Na/Cl diagram, Piper plot and boron isotopic dataset containing saline waters from coastal geothermal systems worldwide further confirm that the salinity in the Jimo geothermal water originated from dissolution of marine evaporites.

The Role of Mineral Sea Water Bonding Process with Graphite-Aluminum Electrodes as Electric Generator

The development of alternative ecofriendly electric energy production technology is very essential. The development of electric generator by using sea water element to boost electron jump in electrode has been studied. The aim of this research is to develop an electrode material composite that can collaborate with sea water to produce electricity. The electrodes tested are copper, aluminum, activated carbon, wood powder, and graphite electrode powder. The result shows that each electrode produces different voltage when interacting with sea water. It is caused by the patterns of the electron movement disrupted by the electron of sea water in producing a new compound. The composite of graphite-aluminum generates high electricity of about 580 mV compared to other materials. The electrical conductivity of graphite material depends on the particle size which is larger at smaller particle size. This research elucidates the role of sea water elements in boosting kinetic energy of delocalized electron on graphite resulting in an electron jump.

Latitudinal Variation of Planktonic Foraminifera Shell Masses During Termination I

The oceans’ surface layer holds large amounts of dissolved inorganic carbon that is exchanged rapidly with the atmosphere. Carbon enters the ocean mainly through the dissolution of atmospheric carbon dioxide (CO2), and a part of it is converted into carbonate by marine organisms. Calcifying marine organisms include planktonic foraminifers that contribute to the marine carbon turnover by generating inorganic carbon production (CaCO3 shells). Anthropogenic CO2 acidifies the surface ocean, changes the carbonate chemistry and decreases the saturation state of carbonate minerals in sea water, thus affecting the biological precipitation of carbonate shells. Relative changes in average foraminiferal shell mass can be interpreted as variations in test thickness and the extent of calcification that subsequently impacts the global carbonate budgets. The response of calcifying marine organisms to elevated atmospheric pCO2 is diverse and complex with studies reporting from reduced rates of net calcification to neutral receptivity or even increased calcification intensities. This diverse behavior implies that the concentration of dissolved inorganic carbon may not be the dominant factor controlling the amount of carbonate shell masses. Here we provide further evidence that glacial/interglacial variations of planktonic foraminifera shell masses are invariant to atmospheric pCO2. We identify that differences in shell weights of several planktonic foraminiferal species from narrow size intervals, over the most recent deglaciation (Termination I) vary systematically as a function of latitude. Past intervals of abruptly changing pCO2 and temperatures, such as the terminations, can offer a glimpse into the response of marine calcifying plankton to changes in surface oceans. We have compiled all the available bibliographic data of planktonic foraminifera shell weights from restricted sieve fractions of different species from the Atlantic, Pacific and Indian Oceans and we find that for the same pCO2 conditions planktonic foraminifera from equatorial regions may alter their shell mass only as little as 8.2%, while towards higher latitudes changes in shell mass reach up to 54% during the transition from the last glacial to interglacial conditions. We attribute this low variability in the shell mass of planktonic foraminifera from the equator to the stability of the physical oceanographic conditions that characterize the equatorial zone.

In-situ incubation of a coral patch for community-scale assessment of metabolic and chemical processes on a reef slope.

Anthropogenic pressures threaten the health of coral reefs globally. Some of these pressures directly affect coral functioning, while others are indirect, for example by promoting the capacity of bioeroders to dissolve coral aragonite. To assess the coral reef status, it is necessary to validate community-scale measurements of metabolic and geochemical processes in the field, by determining fluxes from enclosed coral reef patches. Here, we investigate diurnal trends of carbonate chemistry, dissolved organic carbon, oxygen, and nutrients on a 20 m deep coral reef patch offshore from the island of Saba, Dutch Caribbean by means of tent incubations. The obtained trends are related to benthic carbon fluxes by quantifying net community calcification (NCC) and net community production (NCP). The relatively strong currents and swell-induced near-bottom surge at this location caused minor seawater exchange between the incubated reef and ambient water. Employing a compensating interpretive model, the exchange is used to our advantage as it maintains reasonably ventilated conditions, which conceivably prevents metabolic arrest during incubation periods of multiple hours. No diurnal trends in carbonate chemistry were detected and all net diurnal rates of production were strongly skewed towards respiration suggesting net heterotrophy in all incubations. The NCC inferred from our incubations ranges from −0.2 to 1.4 mmol CaCO3 m−2 h−1 (−0.2 to 1.2 kg CaCO3 m−2 year−1) and NCP varies from −9 to −21.7 mmol m−2 h−1 (net respiration). When comparing to the consensus-based ReefBudget approach, the estimated NCC rate for the incubated full planar area (0.36 kg CaCO3 m−2 year−1) was lower, but still within range of the different NCC inferred from our incubations. Field trials indicate that the tent-based incubation as presented here, coupled with an appropriate interpretive model, is an effective tool to investigate, in situ, the state of coral reef patches even when located in a relatively hydrodynamic environment.

NMR-based monitoring of the hangover curing effects of deep sea water minerals

NMR-based monitoring of the hangover curing effects of deep sea water minerals

Investigating monomineralic and polymineralic reactions during the oxidation of sulphide minerals in seawater: Implications for mining seafloor massive sulphide deposits

Seafloor massive sulphide (SMS) deposits are rich in metals, particularly Cu and Au, and are attracting the attention of mining companies. However, there are various environmental concerns associated with the potential extraction of these deposits, which includes the release of heavy metals following the crushing and grinding of these deposits on the seafloor as sulphide mineral surfaces are exposed to, and oxidised by seawater. A series of monomineralic and polymineralic sulphide mineral, batch reactor, abiotic oxidation experiments were completed in an effort to assess the geochemical impacts of mining SMS deposits in situ. Pyrite, chalcopyrite, sphalerite, and mixtures thereof, were reacted with synthetic seawater under conditions similar to that of the seafloor at between 2 and 3 km depth (2 °C, pH 8.2), but under atmospheric pressure and equilibrated with air. Galvanic effects are evident in the polymineralic experiments, predominantly the cathodic protection of pyrite by the preferential oxidation of chalcopyrite and sphalerite. However, the reaction between sphalerite and chalcopyrite remains unclear. Rates of reaction could not be quantitatively calculated due to the precipitation of iron oxyhydroxides that sequester Fe, Zn, and possibly minor Cu from solution. These experiments demonstrate that chalcopyrite represents the largest geochemical concern for the in situ mining of SMS deposits due to its continuous oxidation and Cu release, its preferential dissolution in galvanic cells, and the known toxicity of Cu relative to Fe and Zn.

Hydrothermal alteration, fluid inclusions and stable isotope characteristics of the Shaquanzi Fe–Cu deposit, Eastern Tianshan: Implications for deposit type and metallogenesis

The Shaquanzi Fe–Cu deposit is an important Fe (–Cu) deposit in the Yamansu Fe mineralization belt, Eastern Tianshan. Five-stage (Stage I to V) hydrothermal alteration/mineralization have been recognized: The early skarn (Stage I) and late skarn (Stage II) stages are featured by extensive garnet and amphibole alteration, respectively. Magnetite mineralization stage (Stage III) is associated with pervasive K+Fe±Ca alteration, forming magnetite, mushketovite, K-feldspar, epidote, magnetite, pyrite and quartz. Chalcopyrite mineralization stage (Stage IV) has an ore mineral assemblage of chalcopyrite, bornite, acicular hematite and sphalerite, accompanied with broad epidote+chlorite+calcite alteration. The late veins stage (Stage V) occurs mainly as epidote+calcite veins crosscutting the host rocks and earlier-stage minerals.Stage I hydrothermal fluids have high temperatures (>600°C), medium-high salinities, with magmatic δ18Ofluid=+6‰ to +11.7‰. Stage III ore-forming fluids are medium-high-temperature (ca. 470–570°C) with medium salinity. Stage III minerals were formed under δDfluid=−45.7‰ to −24.3‰, δ18Ofluid=+5.8‰ to +9.1‰ and δ34Sfluid=−1.7‰ to +4.7‰, indicative of magmatic fluids mixed with minor seawater. In contrast, Stage IV fluids have low temperatures (ca. 160°C), medium-low salinities and are Ca-rich, with isotopic compositions reflecting basinal brine mixed with meteoric water (δ13Cfluid=−6.6‰ to −2.3‰; δ18Ofluid=−3.3‰ to +2.8‰ and δ34Sfluid≥+24.8‰).The Shaquanzi diorite (zircon U–Pb age: 298±5Ma) is broadly coeval with previous Re–Os ages of the Shaquanzi magnetite and pyrite (303±12Ma and 295±7Ma, respectively), indicating that the Shaquanzi Fe–Cu metallogeny may have been genetically linked to the regional magmatic–hydrothermal activities led by the Yamansu arc-backarc basin inversion. Features of hydrothermal alterations, mineral assemblages, ore-forming fluids and tectonic setting all suggest that the Shaquanzi Fe–Cu deposit is an IOCG-like deposit, similar to those in the Cenozoic Central Andes.

Benthic marine calcifiers coexist with CaCO3‐undersaturated seawater worldwide

AbstractOcean acidification and decreasing seawater saturation state with respect to calcium carbonate (CaCO3) minerals have raised concerns about the consequences to marine organisms that build CaCO3 structures. A large proportion of benthic marine calcifiers incorporate Mg2+ into their skeletons (Mg‐calcite), which, in general, reduces mineral stability. The relative vulnerability of some marine calcifiers to ocean acidification appears linked to the relative solubility of their shell or skeletal mineralogy, although some organisms have sophisticated mechanisms for constructing and maintaining their CaCO3 structures causing deviation from this dependence. Nevertheless, few studies consider seawater saturation state with respect to the actual Mg‐calcite mineralogy (ΩMg‐x) of a species when evaluating the effect of ocean acidification on that species. Here, a global dataset of skeletal mole % MgCO3 of benthic calcifiers and in situ environmental conditions spanning a depth range of 0 m (subtidal/neritic) to 5600 m (abyssal) was assembled to calculate in situ ΩMg‐x. This analysis shows that 24% of the studied benthic calcifiers currently experience seawater mineral undersaturation (ΩMg‐x &lt; 1). As a result of ongoing anthropogenic ocean acidification over the next 200 to 3000 years, the predicted decrease in seawater mineral saturation will expose approximately 57% of all studied benthic calcifying species to seawater undersaturation. These observations reveal a surprisingly high proportion of benthic marine calcifiers exposed to seawater that is undersaturated with respect to their skeletal mineralogy, underscoring the importance of using species‐specific seawater mineral saturation states when investigating the impact of CO2‐induced ocean acidification on benthic marine calcification.

Origin and characteristics of brackish groundwater in Abu Madi coastal area, Northern Nile Delta, Egypt

Hydrogeochemical and geoelectrical resistivity investigations were carried out to assess the origin and characteristics of a brackish groundwater in Abu Madi coastal area. Twenty six surface water, shallow and deep groundwater samples were collected and analyzed for various ionic concentrations as well as oxygen and hydrogen stable isotopic contents. In addition, a total of 20 vertical electrical sounding sites were conducted to investigate layers’ thicknesses, resistivities, and to detect the water-bearing layers. Then, 2-D Electrical Resistivity Tomography (ERT) along two profiles in the study area was conducted to get information about the surface water effect on recharge. The stable isotopic composition and the chloride concentrations strongly suggest that the deep groundwater in Abu Madi area is dominated by inland freshwater with a minor seawater component. This groundwater was recharged during the first and the third Holocene humid climatic cycles where the sea surface was about 125 and 25 m below the current sea level, respectively. The brackish nature and higher piezometric surface of the groundwater, as well as the occurrence of vertical low-salinity seawater zone in front of the study area, support the possibility of submarine groundwater discharge. The geoelectrical resistivity surveying, on the other hand, revealed a number of geoelectrical groundwater-bearing layers. The main water-bearing layer in the study area is represented by the sixth geoelectrical layer, which has relatively high resistivity and a considerable thickness being consistent with the hydrogeochemical observations. ERT results point to the presence of shallow water-bearing layers recharged from the surface water drains with low resistivity and surface rain water of moderate resistivity. Results from the hydrogeochemical analyses and the different hydrogeological data are consistent with the high resistivity values of this geoelectrical layer. However, the overall high specific conductance and high sodium hazards indicate that the groundwater in the study area should be carefully treated before irrigation and domestic uses through mixing it with surface irrigation water.

Identification of anthropogenic and natural inputs of sulfate into a karstic coastal groundwater system in northeast China: evidence from major ions, &amp;lt;i&amp;gt;δ&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C&amp;lt;sub&amp;gt;DIC&amp;lt;/sub&amp;gt; and &amp;lt;i&amp;gt;δ&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;34&amp;lt;/sup&amp;gt;S&amp;lt;sub&amp;gt;SO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;&amp;lt;/sub&amp;gt;

Abstract. The hydrogeochemical processes controlling groundwater evolution in the Daweijia area of Dalian, northeast China, were characterised using hydrochemistry and isotopes of carbon and sulfur (δ13CDIC and δ34SSO4). The aim was to distinguish anthropogenic impacts as distinct from natural processes, with a particular focus on sulfate, which is found at elevated levels (range: 54.4 to 368.8 mg L−1; mean: 174.4 mg L−1) in fresh and brackish groundwater. The current investigation reveals minor seawater intrusion impact (not exceeding 5 % of the overall solute load), in contrast with extensive impacts observed in 1982 during the height of intensive abstraction. This indicates that measures to restrict groundwater abstraction have been effective. However, hydrochemical facies analysis shows that the groundwater remains in a state of ongoing hydrochemical evolution (towards Ca–Cl type water) and quality degradation (increasing nitrate and sulfate concentrations). The wide range of NO3 concentrations (74.7–579 mg L−1) in the Quaternary aquifer indicates considerable input of fertilisers and/or leakage from septic systems. Both δ13C (−14.5 to −5.9 ‰) and δ34SSO4 (+5.4 to +13.1 ‰) values in groundwater show increasing trends along groundwater flow paths. While carbonate minerals may contribute to increasing δ13CDIC and δ34SSO4 values in deep karstic groundwater, high loads of agricultural fertilisers reaching the aquifer via irrigation return flow are likely the main source of the dissolved sulfate in Quaternary groundwater, as shown by distinctive isotopic ratios and a lack of evidence for other sources in the major ion chemistry. According to isotope mass balance calculations, the fertiliser contribution to overall sulfate has reached an average of 62.1 % in the Quaternary aquifer, which has a strong hydraulic connection to the underlying carbonate aquifer. The results point to an alarming level of impact from the local intensive agriculture on the groundwater system, a widespread problem throughout China.