Evaporites Research Articles

ASSESSMENT OF NATURAL RADIOACTIVITY OF SALT SAMPLES WITH REDUCED SODIUM CONTENT

Poles are the leaders in Europe in terms of the amount of salt consumed per day. Table salt is themost frequently used spice and is essential for the proper functioning of the body. However, itsexcessive consumption may have adverse effects on human health. The Word Health Organization(WHO) informs that the leading cause of premature deaths in the European region of WHO is thecardiovascular disease. This is why medicine is increasingly recommending the use of low-sodiumsalt, which contains a reduced content of sodium and an increased content of potassium becauseit is essential for the proper functioning of the brain, cells and for proper work of muscles. Thereis no information in the literature on the concentration of natural radioactive isotopes presentin sodium-reduced salts used as a substitute for table salt. Therefore the aim of this study wasestablishing the concentration of natural radioactive isotopes in salt samples with low sodiumcontent available in retail sale on the Polish market and widely used in Polish households. Inthese salt samples analysed was the concentration of natural radioactive isotopes like radium,thorium and potassium with use of Mazar type gamma radiation spectrometer connected witha scintillation probe NaI (Tl). Concentration of 226Ra and 232Th isotopes in the tested salt sampleswith reduced sodium content amounted to below the background level of determination, and the40K content was within the limits 3386–5794 Bq∙kg-1. Additionally on the basis of the establishedconcentration of natural radioactive isotopes, the annual loading effective dose was calculated forwomen and men classified to the group of adults from the point of view radiological protection.The effective dose limit of 1 mSv∙y-1 was not exceeded for any test subject consuming reducedsodium salts.. The obtained results were compared with reported data from other countriesavailable in the literature.

Geochemical study of groundwater in the Oued El Hatiba Basin, pre-Saharan Atlas, eastern Algeria

ABSTRACT The Oued El Hatiba Basin, located at the eastern boundary of the Aures massif, constitutes the main massif of the pre-Saharan Atlas in eastern Algeria. The area is characterized by a semi-arid climate. Geologically, the basin features a succession of marls at the base, overlain by Cretaceous limestones, covered by Plio-Quaternary sediments composed of alluvium and sand. The Babar Dam, with a capacity of 41 hm3, is situated in this basin, draining an area of 567 km2 along the Larab wadi. It is intended for irrigation of surrounding lands and the supply of potable water to neighboring communities. The analysis of major element concentrations from various sampled water points reveals that the waters exhibit dominant facies: chloride–calcium (48.88%), sulfate–calcium (24.44%), bicarbonate–calcium (15.55%), magnesium bicarbonate (08.88%), and magnesium chloride (02.22%). These chemical facies are determined by the aridity of the climate, water–rock interaction, dissolution, and mineral precipitation, which are mediated by cationic exchanges throughout the water flow toward its outlet. The calculation of mineral saturation indices in the water indicates that only carbonate minerals tend to precipitate, notably calcite and dolomite, while evaporitic minerals (gypsum and halite) tend towards dissolution.

Impact of effluents from a closed mine on the surrounding water resources: Groundwater contamination of the historical abandoned mine site in Japan.

The extraction of mineral deposits is often associated with the occurrence of acid mine drainage (AMD), which can persist even after mine closure due to remaining sulfide minerals. This study investigates a 200-year-old abandoned mine and its impacts on nearby water resources. The study area is well known for Kuroko ore deposits located upstream of spring and river water resources. To elucidate the impacts of the abandoned mine site, mine water and spring and river water samples were collected, and their geochemical properties were monitored between 2021 and 2022. Groundwater, seepage, and surface water at the mine site showed AMD characteristics with Ca2+-SO42-/Mg2+-SO42- type. AMD-affected mine water showed a low pH range of 3.40-4.84, with elevated SO42- of up to 326mg/L. At the downstream of the mine site, one of the groundwater samples showed pH of 3.55 and average concentrations of 5.03mg/L of Al, 2.06mg/L of Cu, 2.06mg/L of Fe, 0.42mg/L of Pb, and 8.04mg/L of Zn, inferring the contaminant transport. Saturation indices of the mine water also indicated that the solubility controlling phases, anglesite, gibbsite, ferrihydrite, and jarosite influence the concentrations of Al, Fe, and Pb at the mine site. Meanwhile, spring and river water samples showed Ca2+-HCO3-, Ca2+-SO42-, and Na+-K+-HCO3- type with a circumneutral pH range of 5.59-8.02 and they were unaffected by AMD. The principal component analysis (PCA) of the spring and river water samples also showed higher loadings for Ca, Mg, NO3-, and Cl- reflecting the abundance of carbonate and evaporite minerals while the mine water and groundwater downstream showed higher loadings of Cl-, Fe, SO42-, and Zn. The results suggest that the past mining activities only influenced the mine site and groundwater downstream. Consequently, the fate and migration of contaminants in the downstream of the mine site should be evaluated in the near future.

Testing the viability of normal seawater dolomitization in lower Cambrian carbonates using clumped isotopes

ABSTRACTWhile dolomitization by normal seawater has been commonly used to explain the formation of Cenozoic dolomites, ancient platform‐scale dolostones are normally interpreted as being products of either evaporative brines or mixed fresh and marine fluids. However, the viability of these two models in ancient successions is continuously questioned by new studies which favour normal or slightly modified seawater as the dolomitizing fluid. This study presents an ancient example from the lower Cambrian Longwangmiao Formation (South China) which, although appearing to have formed in association with evaporite minerals and experienced meteoric subaerial exposure, was interpreted to be dolomitized by normal seawater. Three petrographic types of dolomites, formed in the penecontemporaneous to early burial diagenetic stages in the Longwangmiao Formation. These include finely, fine to medium and medium to coarse crystalline dolomites. The stable isotope compositions (δ13Ccarb, δ18Ocarb and Δ47) were determined on pure dolomite samples that had been chemically isolated, and the results interpreted using a coupled numerical model. This analysis strongly suggests that the dolomite was replaced by Cambrian seawater (ca −2‰) and subsequently experienced closed‐system recrystallization (water/rock ratio <0.4) in the deep burial stage. The vertical variation of the mol% Mg content of the dolomite shows multiple episodes of dolomitization with the increasing stoichiometry in each episode suggesting the control of sea‐level changes. This study has revealed that the normal‐seawater dolomitization could also proceed in an evaporative environment on a shallow‐water platform. As in many studies of ancient carbonates, the recognition of diagenetic fluids is often hindered by complex geochemical overprinting in bulk samples.

Hydrochemical analysis and groundwater quality assessment for irrigation in the Remila Plain, Khenchela, Northeast Algeria

Water resources are facing significant challenges in result of rapidly growing demand, deteriorating quality, and the effects of climate change. Today, water quantity and quality issues have become prevalent in various regions across the globe, affecting both northern and southern territories. Among the sectors reliant on this resource, irrigation stands out as the largest consumer of water. When surface water becomes inaccessible due to insufficient precipitation or other factors, the use of groundwater becomes the only viable alternative for irrigation. The Remila Plain (Khenchela) is located in an endorean watershed in northeastern Algeria and extends over 250 km2 in a synclinal basin filled with water from the Mio-Plio Quaternary - the main aquifer of the region, widely used for irrigation. The aim of this work is to study the hydrochemistry of these waters, as well as the evolution of mineralisation, the identification of the origin of the chemistry, and the suitability of these waters for irrigation. Initial results indicate an evolution of mineralisation in the direction of groundwater flow, with electrical conductivity values varying between 1000μS/cm in the recharge zones, and 2700μS/cm at the outlet. This mineralisation is mainly due to the dissolution of evaporitic minerals and the alteration of silicates. In addition, the various water quality indices used indicate that the water can be used for irrigation without major risk to plants and soils.

Gypsum crystal morphologies in lake sediments for paleoclimate reconstructions: a case study in Fuente de Piedra playa-lake (Málaga)

Gypsum (CaSO4∙2H2O) is one of the most common evaporitic minerals on Earth. Its crystals exhibit diverse morphologies that can provide insights into their depositional environment. We analyzed the morphologies of gypsum deposits in a 14 m sedimentary sequence of Fuente de Piedra playa-lake (Málaga, Spain) to link its variations to sedimentary facies and changes in the past lake level. Precipitation of primary prismatic crystals prevailed during lake highstand periods. In contrast, lenticular gypsum crystals are consistently present throughout the entire core and do not seem to be related to specific lake levels. An exception are macro-lenticular crystals, which seem to be correlated with dry periods and high salinity water. Subrounded gypsum grains, eroded from former primary crystals, are also abundant along the sequence and usually concentrate in facies related to stages of lake agitation during highstand periods. Gypsum is generally absent during lowstand periods, which may indicate relatively high dissolve organic matter or, more likely, less interaction of the lake with the saline groundwater aquifer beneath. Our results suggest that the occurrence of some gypsum morphologies can be used to infer paleo-lake levels.

Green product of Kusamba Salt: an Alternative of Re-Branding Strategy in Kusamba, Klungkung, Bali

The Bali Government, recognizing the potential of Kusamba salt, has proposed a strategic plan to introduce it worldwide. The governor of Bali, Wayan Koster, suggested enhancing the marketing strategy to make Kusamba salt more appealing. This involves creating attractive packaging and promoting the product's unique qualities, such as its high-quality production methods and the environmental benefits of using natural Salt. Product Differentiation: The proposal emphasizes the need to differentiate Kusamba salt from other table salt products in the market. This could be achieved by highlighting the product's low iodine content, which benefits health and environmental sustainability. Market Integration: The plan also aims to integrate Kusamba salt into global markets. This involves identifying and establishing partnerships with international retailers and distributors interested in natural and health-conscious products. Farmer Empowerment: A significant part of the strategy focuses on empowering the salt farmers of Kusamba village. This includes facilitating the management of BPOM (Badan et al.) licenses and creating opportunities for the farmers to participate in the marketing and distributing their products. Environmental Sustainability: The proposal highlights the importance of promoting Kusamba salt as an environmentally friendly product. This could involve using eco-friendly packaging and promoting the product's sustainable production methods. In summary, the "Green Product of Kusamba’s Salt: An Alternative of Rebranding Strategy" this study aims to elevate the market value of Kusamba salt by optimizing its marketing strategy, differentiating it from other table salt products, integrating it into global markets, empowering the salt farmers, and promoting its environmental sustainability.

High Performance of Mn2O3 Electrodes for Hydrogen Evolution Using Natural Bischofite Salt from Atacama Desert: A Novel Application for Solar Saline Water Splitting.

Solar saline water splitting is a promising approach to sustainable hydrogen production, harnessing abundant solar energy and the availability of brine resources, especially in the Atacama Desert. Bischofite salt (MgCl2·6H2O) has garnered significant attention due to its wide range of industrial applications. Efficient hydrogen production in arid or hyper arid locations using bischofite solutions is a novel and revolutionary idea. This work studied the electrochemical performance of Mn2O3 electrodes using a superposition model based on mixed potential theory and evaluated the superficial performance of this electrode in contact with a 0.5 M bischofite salt solution focusing on the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) that occur during saline water splitting. The application of the non-linear superposition model provides valuable electrochemical kinetic parameters that complement the understanding of Mn2O3, this being one of the novelties of this work.

Fluvial-lacustrine influences on linear dune erosion at Lake Caroline in the Simpson Desert of Australia

Linear dunes are frequently examined with regard to their formation and maintenance; however, erosion or degradation of these landforms is less commonly addressed, due in part to the lack of observable changes in the geologic record. This study investigates the significant erosion of linear dunes along Lake Caroline, a playa in the northern Simpson Desert of central Australia. Field observations, laboratory analyses, and remote sensing imagery document recent fluvial and lacustrine interactions at Lake Caroline. Compositional and geochemical sediment analyses from three ∼2 m deep hand-augured sample sites indicate that the playa is primarily filled with sand from linear dunes, but also contains evaporite minerals and weathered local bedrock. Satellite images show that the playa has flooded at least 58 times since 2001. Our results indicate that present-day aeolian processes are sufficient to mobilize and transport sediment but are dominated by fluvial-lacustrine processes, resulting in the playa-adjacent dunes becoming isolated and starved of local sediment. As a result, the dunes are currently eroding into the playa which supports the conclusion that long-distance sediment transport is not responsible for the formation or maintenance of linear dunes as suggested by the linear due extension hypothesis. Burial dates from optically stimulated luminescence (OSL) indicate the linear dunes have been eroding for as much as 24 ka, and sediment samples from the playa near one linear dune suggest an onset of dune formation in the area before 58 ka. This work documents an instance in geologic time during the late Quaternary when aeolian, fluvial, and lacustrine processes are competing with one another, offering new insights into the dynamics of linear dunes in the arid Simpson Desert.

COMPOSITES BASED ON OYMASH SALT

In recent years, an urgent task is to find materials of domestic origin and create on their basis affordable and cheap, easy-to-use, reliable composite compositions for the preparation of well killing fluid. Nowadays, the need for process fluids that help preserve and restore reservoir properties always remains. Available and inexpensive natural salt from the Oimash deposit (Mangistau region) can create the required density in the well killing fluid and be its main component. The aim of the work is to develop compositions based on Oimash salt for the preparation of well killing fluids, which include all necessary additives. Methodology: The physicochemical characteristics of the composite compositions for the preparation of well killing fluid (bulk density, mass fraction of insoluble substances in water, mass fraction of moisture, solubility) and using standard methods corrosion activity studied. Results. The physicochemical parameters of Oimash salt showed that the salt is not prone to caking, the proportion of insoluble substances in sea water is 0.45%, and in waste water - 0.54%. The solubility of the developed compositions depending on the types of water was studied. All compositions are soluble in various types of water. The solubility of all compositions in seawater is 96.64-97.56%, and in wastewater from 95.59% to 95.97%. The optimal composition of the salt composition is the composition of sample No. 1 with the percentage content of components TPPF: NTF: PAA = 0.5: 0.5: 0.1:30, with a bulk density of 0.7055 t/m3, a mass fraction of insoluble substances in water - 1.4334%, well soluble in sea and waste water 97.56 and 95.66%. As the results of samples No. 1 showed, the corrosive environment is slightly aggressive in terms of aggressiveness.

Long-term potato response to different irrigation scheduling methods using saline water in an arid environment

Crops’ water requirement is generally higher than the annual average precipitation in arid environments characterized by scarce freshwater resources. While using saline water for irrigation can help sustain agriculture in water-stressed regions, several challenges arises concerning productivity and soil salinization. However, adoption of efficient irrigation techniques such as drip irrigation, irrigation scheduling, and deficit irrigation can help optimize water productivity and mitigate salinity problems in irrigated agriculture. In southern Tunisia, potato is considered among the main cultivated horticultural crops due to its high economic value while it is considered as a crop sensitive to salinity. This crop (cv. Spunta) was the subject of long-term studies (2002–2020) conducted during the fall period in the arid region of Médenine. The crop response to full and deficit irrigation with saline water was assessed for several seasons under contrasting climatic conditions. Scheduling using the soil water balance (SWB) method consisted of the total and/or partial replacement of accumulated crop evapotranspiration (ETc), as derived from climatic data and crop coefficients. The impact of decreasing amounts of irrigation waters on crop yield and soil salinity with waters having a salinity ranging between 3 and 7 dS m−1 was evaluated. Results showed improvements in yield (30% to 37%) obtained with the SWB strategy under actual farming conditions, supporting the use of this strategy for irrigation. Appropriate scheduling also seems to be a key element in saving water (15%–22%) and in reducing risks of soil salinization. In the dry environment of southern Tunisia, optimum supply seems to correspond to a replacement of 100% to approximately 70%–80% of ETc. Applying such irrigation levels resulted in a lower salinity buildup in the root zone and higher crop water productivity. Natural salt leaching seems to be more effective under a more humid soil profile. Yield decreases and soil salinity increases almost linearly (r2 = 0.60) with decreasing irrigation water amounts. Future work should focus on the integration of management practices when using saline water. Investigating the relationship and interaction between irrigation amounts, cultivar, fertilizer supply, and salt leaching will help in resolving productivity and environmental issues.

Exploring Biofilm-Related Traits and Bile Salt Efficacy as Anti-Biofilm Agents in MDR Acinetobacter baumannii.

Acinetobacter baumannii has been designated as a critical priority pathogen by the World Health Organization for the development of novel antimicrobial agents. This study aimed to investigate both the phenotypic and genotypic traits of multidrug-resistant (MDR) A. baumannii strains, along with the effects of natural bile salts on biofilm formation. The research analyzed phenotypic traits, including autoaggregation, hydrophobicity, twitching motility, lectin production, and biofilm formation, as well as genotypic traits such as the presence of bap and blaPER-1 genes in twenty wound and eight environmental MDR A. baumannii isolates. While all strains were identified as good biofilm producers, no statistically significant correlation was detected between the examined traits and biofilm formation. However, differences in biofilm production were observed between environmental and wound isolates. The natural bile salts Na-cholate, Na-deoxycholate, and Na-chenodeoxycholate demonstrated effective anti-A. baumannii activity (MIC = 0.25-10 mg mL-1), with significant anti-biofilm effects. Na-deoxycholate and Na-chenodeoxycholate inhibited 94-100% of biofilm formation at super-MIC concentrations (8-32 mg mL-1). This study underscores the urgent need for innovative strategies to combat antibiotic resistance and biofilm formation in A. baumannii, highlighting the potential of natural bile salts as promising biofilm inhibitors and encouraging further research into their modification and combination with other antimicrobials.

Revisiting a natural wine salt: calcium (2R,3R)-tartrate tetrahydrate.

The crystal structure of the salt calcium (2R,3R)-tartrate tetrahydrate {systematic name: poly[[diaqua[μ4-(2R,3R)-2,3-dihydroxybutanedioato]calcium(II)] dihydrate]}, {[Ca(C4H8O8)(H2O)2]·2H2O}n, is reported. The absolute configuration of the crystal was established unambiguously using anomalous dispersion effects in the diffraction patterns. High-quality data also allowed the location and free refinement of all the H atoms, and therefore to a careful analysis of the hydrogen-bond interactions.

An investigation on thermoluminescence properties and kinetic parameters of Çankırı rock salt

This study investigates the thermoluminescence (TL) dosimetric properties and kinetic parameters of natural salt samples sourced from the Çankırı rock salt cave in Turkey using β irradiation. Obvious effective TL maximum observed at around 85 and 230°C. A preheat condition was determined to apply a thermal cleaning for the lower temperature side of TL spectrum. Dose sensitivity, linearity and reusability characteristics were investigated for effective TL maximum on the high temperature side of the spectrum. TL kinetic parameters were determined via various heating rates (VHR) experiment, and whole TL glow curve was studied via Tm−Tstop experiment and glow curve deconvolution. General order kinetics approach was utilized for glow curve deconvolution analysis. Kinetic parameters were determined for at least eight electron trap levels which has activation energies in the range of 0.8–1.53 eV.

Biodiversity and biotechnological potential of cultivable Halophilic bacteria from Slana voda (Oravska Polhora, Slovakia) natural salt spring

AbstractHalophilic microorganisms are of immense importance in various fields of biotechnology. There is a multitude of actual or potential applications in the research of environmentally friendly applications in biodegradation, decolorization, food biotechnology, and biopolymers production. Thirty-eight strains of halophilic bacteria were isolated from the Slana voda (Slovakia, Central Europe) natural salt spring, with a tolerance of up to 20% of NaCl. The Halomonas genus accounted for more than 35% of the cultivable microbiota, followed by Shewanella and Pseudoaltermonas genera. More than 55% of bacterial isolates were able to produce at least one of the tested hydrolases (cellulase, lipase, amylase, protease) and three of them were positive for all four enzyme activities. Bacterial isolates showed a relatively high ability to degrade synthetic dyes, namely congo red, crystal violet, malachite green, methylene blue, methyl red, and safranin (5.26, 42.11, 44.74, 63.16, 92.18, and 18.42% of isolates respectively). Interestingly only a small overlap was observed between the isolates producing extremozymes and the isolates demonstrating decolorizing activity.

Carboniferous–Permian interglacial warming and volcanism temporally linked to the world's oldest alkaline lake deposit of the Fengcheng Formation, NW China

In addition to being an important lacustrine hydrocarbon source rock, the Fengcheng Formation possesses well-preserved sodium‑carbonate evaporite units and tuff beds. Known ancient alkaline salt-lake deposits bearing sodium‑carbonate evaporite minerals like the Late Paleozoic Fengcheng Formation are limited beyond the modern day. However, hitherto the absolute age of the alkaline lacustrine Fengcheng Formation of the Junggar Basin (China) is debated (Late Carboniferous and/or Early Permian), and therefore its temporal link to a specific stage of the Late Paleozoic Ice Age (LPIA) remains unclear. Here, new ReOs geochronology demonstrates that the Fengcheng Formation is predominately of Late Carboniferous-age (304.4 to 297.3 Ma), and therefore its deposition coincides with the interglacial climate warming interval between glaciation C4 and P1 of the LPIA and not the younger interglacial stages as previously proposed. The ReOs isotope systematics indicate that the lake water column during the deposition of the Fengcheng Formation had a relatively unradiogenic Os (187Os/188Os, Osi) isotope composition (0.32 to 0.36), which is in contrast to the typical radiogenic Osi recorded for lacustrine deposits throughout geological time. The unradiogenic Osi for the Fengcheng Formation ties the source of the Os in the lake to the weathering of adjacent mafic volcanic rocks and/or hydrothermal input (∼0.13). As a result, the penecontemporaneous relationship to the Late Paleozoic interglacial climate warming (causing enhanced evaporation) coupled with weathering of volcanic rocks and/or hydrothermal fluid input into the lake is considered to have been mechanistic in the formation of an alkaline salt lake dominated by sodium and carbonate.

Quantitative records of paleotemperature in Qarhan Salt Lake, Qaidam Basin and its relationship with potassium deposits

Qarhan Salt Lake, located in the Qaidam Basin on the Qinghai-Tibet Plateau in northwestern China, is the largest potash production base in China. The main potash deposit in Qarhan Salt Lake is a comprehensive deposit in which the liquid potassium resources dominated by potassium-rich and lithium-rich brine coexist with the low-grade solid potassium salt deposit composed of solid potash minerals (polyhalite, carnallite, sylvite). Polyhalite is one of the representative potassium minerals, widely distributed in the Bieletan area of Qarhan Salt Lake, coexisting with halite, and its deposition indicates that the paleo-temperature of brine in this area once fluctuated obviously. Twenty core samples from two boreholes in the Bieletan area of the Qarhan Salt Lake were subjected to fluid inclusions thermometry, and homogenization temperatures reflecting the brine temperatures during the precipitation of evaporite minerals in the Salt Lake were obtained, ranging from 12.4 to 28.9 °C and 9.2 to 19.8 °C, respectively. By scanning electron microscopy, acicular polyhalite and pompom-like aggregate of polyhalite have been identified in the sampling layer, indicating that evaporite deposition have reached the stage of potassium salt deposition. The temperature fluctuations of the fluid inclusions and the elemental chemical data are compared vertically, and the sections with significant temperature fluctuations are close to the layers where polyhalite were deposited. It shows that the paleo-temperature fluctuation impact the sedimentary environment of brine, and then affected the polyhalite deposition of Qarhan Salt Lake.

Evaluating evaporites as potential archives of lake and seawater lithium isotopic ratios: An experimental study using various natural saline fluids

Reconstructing the lithium isotope composition (δ7Li) of ancient seawater and lacustrine environment is crucial for tracing silicate weathering processes that regulate Earth's carbon cycle and climate. This study examines the reliability of evaporite minerals in preserving the Li isotope signature of the original brines from which they precipitate. We conducted evaporation experiments on modern natural waters from Qinghai Lake, the Yellow Sea, and Chaka Salt Lake, each with unique salinity and chemical composition, to examine the behavior of lithium isotope ratios in the evolving brine and precipitated evaporite minerals.Our results show that initial hydrochemical conditions of the lake and ocean are the primary control on the evolution of major and trace elements and the mineral precipitation sequences during evaporative concentration. Aragonite, calcite, gypsum, and/or nesquehonite precipitated prior to halite. Li isotope fractionation of these non-halite precipitates varied significantly between 4‰ and 17‰. However, the δ7Li values of halite closely mirror those of the initial lake and seawater, indicating negligible Li isotope fractionation (<1‰) during halite precipitation. The δ7Li values of the evolving brines remain unchanged throughout the evaporation experiment. Solid phases precipitating before halite constitute <1–2% of the total moles of salt precipitated from the complete evaporation of the initial waters, thus, having little to no influence on the δ7Li values of evolving brines. Although halite comprises >77% of the total moles of salt, it does not fractionate Li isotopes. Therefore, halite more accurately reflects the δ7Li values of the co-evolving brine as well as those of the initial, unevaporated lake and seawater. These results underscore the potential of late stage evaporites, particularly halite, to serve as high-fidelity archives of ancient lacustrine and seawater δ7Li values. Such records are instrumental in reconstructing past silicate weathering and climatic conditions.

Deciphering chemical and physical processes that give rise to natronization in a shallow aquifer in an arid zone

Groundwater provides a reliable and stable alternative to surface water resources in arid and semiarid regions to meet human and environmental needs. However, excessive exploitation in the last decades has led to significant salinization of groundwater and soils in many parts of the world. In the highlands of central-north Mexico, a number of agriculturally used aquifers show increasing salinization effects. Tierra Nueva is a case where salt precipitations in recent years have made land mostly unsuitable for agriculture. It is assumed that the intensive irrigation under dry climatic conditions, together with the presence of argillaceous horizons at shallow depth and the alteration of Na-rich volcanic rocks, determine the occurrence of specific salinization processes producing evaporite minerals in excess. This investigation provides physical and chemical evidence of groundwater processes explaining the accumulation of solutes in groundwater and soils. It shows that the principal evolutionary processes in the studied aquifer were water-rock interactions and evaporation, while ionic exchange processes dominated the water circulating through the clay-sandy materials of the valley. Geochemical models show that recharging water dissolved CO2 from the unsaturated zone, and reacted with silicates (i.e. hydrolysis of albite, K-feldspar, and biotite), underwent cation exchange, and precipitated kaolinite. In the discharge area, the mineral natron was dissolved, while thermonatrite, natrolite (Na-natrolite), nontronite (Ca-nontronite, K-nontronite, Mg-nontronite, Na-nontronite) were formed, among other reactions. This salinization process eventually leads to soils which are unsuitable for agricultural activities. The study of this phenomenon represents an important contribution to the understanding of the implications of the expansion of arid and semiarid lands.

PA/APVC nanofiltration membrane from reactive positively charged substrate membrane

Efficient Li+ and Mg2+ from natural seawater and salt lakes using nanofiltration is essential for efficient extraction of lithium resources and to address the global energy shortage. The combination of size sieving and the Donnan effect is crucial for optimal selectivity. We proposed a positively charged reactive support layer to design dual positively charged layer to enhance the magnesium-lithium separation. The positively charged support layer was prepared by ammoniating the PVC membrane with PEI, and then reacted with TMC to successfully prepare a dual positively charged layer PA/APVC nanofiltration membrane with high Li+/Mg2+ selectivity. The reactive support layer not only established a covalent bond connection with the PA layer, which increased the stability of the active layer, but also showed a positive charge (23.59 mV at pH=7) after ammonization, which further enhanced the Mg2+ repulsion from 82.57 % to 98.56 %. Furthermore, the highest separation factor achieved was 23.34 when a mixed solution containing Mg2+ and Li+ in a mass ratio of 50:1 was utilized, which was 13.48 times that of commercial nanofiltration membranes. The utilization of a reactive substrate membrane in the fabrication process of the PA/APVC membrane offers innovative prospects for future investigations on magnesium-lithium separation, contributing to the advancement of nanofiltration membranes.