Salt Mass Research Articles

Rapid evolution of salt glacier caves on a mountain diapir in a semiarid climate

Salt caves occur mostly in hyperarid and arid climates and are typically a few thousand years old. There is little data on the evolution of salt caves in semiarid climates, and no data on caves developed in salt glaciers, i.e., salt masses spreading under their own weight, similar to ice glaciers. The age of salt caves and the incision rates of cave streams were studied on a salt glacier of the Jahani diapir in a semiarid climate, Zagros Mts., Iran. Wood fragments from 3 caves sampled 0–11.3 m above the present streambed were dated by AMS 14C. The cave passages accessible today were developed during the last ~600 years at the Jahani. The cave level 5–6 m above the present streambed was formed 1520–1660 CE or slightly earlier, then the stream incised upward and reached its highest level between 1690 and 1920 CE or slightly earlier. Then, the downward incision started. This indicates that caves in semiarid climates evolve extremely rapidly. The maximum vertical incision rate of the cave stream on the semiarid Jahani diapir is 20–110 mm/yr, which is faster than 0.4–25 mm/yr in caves in hyperarid climates. The incision rate of the cave stream at the Jahani exceeds the denudation rate of the thick cap soil surface, being comparable to the denudation rate of salt exposures. The persistence of the steep longitudinal profiles of the integrated salt caves at the Jahani is probably caused by the transport of very coarse sediment. Aggradation was probably caused either by blocking of cave passages by earthquakes or by more intense erosion of the cap soil. The salt glacier at the Jahani is moving slowly (<10 mm/yr); claims that this glacier is the fastest on Earth (velocity in the range of m/yr) are based on a study that did not follow geodetic standards and are in strong disagreement with the age of the caves and other lines of evidence.

Use of solid thermolytic salts to facilitate microwave-induced in situ amorphization

Moisture was frequently used as dielectric heating source in classical microwave-able systems to facilitate microwave-induced in situ amorphization, however such systems may face the potential of drug hydrolysis. In this study, solid thermolytic salts were proposed to function as moisture substitutes and their feasibility and impacts on microwave-induced in situ amorphization were investigated. It was found that NH4HCO3 was a promising solid alkaline salt to facilitate both microwave-induced in situ amorphization and in situ salt formation of acidic indomethacin (IND). Moreover, it could improve the chemical stability of the drug and the dissolution performance of compacts relative to classical moisture-based compacts upon microwaving. Further mechanistic study suggested that the in situ amorphization occurred prior to the in situ salt formation, especially in formulations with low drug loadings and high solid salt mass ratios. For compacts with low polymer ratios, in situ salt formation took place subsequently, where the previously amorphized IND within compacts could interact with the NH3 gas produced in situ by the decomposition of NH4HCO3 and form the ammonium IND salt. Microwaving time showed great impacts on the decomposition of NH4HCO3 and the in situ generation of water and NH3, which indirectly affected the amorphization and salt formation of IND. In comparison to the moisture-based systems, the NH4HCO3-based system showed a number of advantages, including the reduced potential of IND hydrolysis due to the absence of absorbed moisture, a wider category of applicable polymeric carriers other than hygroscopic polymers, and an increase in drug loading up to 50% (w/w).

THE SPATIAL DISTRIBUTION AND MOVEMENT OF SOLUBLE SALTS FROM ROMANIAN SOILS

The objective of this paper is to present a sketch map of the accumulation of soluble salts in soils from Romania, as a support for improving saline soils or preventing undesirable anthropogenic salinization phenomena.The map highlights the spatial distribution and movement of easily soluble salts in soil at the scale of the entire country, It is an overview on origin, sources and pathways of migration and accumulation of easily soluble salts in interdependence with natural factors and conditions.Taking into account the movement pathways of easily soluble salts in soil, two geochemical zones were separated on the map: the eluviation - transit zone and the transit - accumulation zone. In the last zone, areas where the accumulation of salts becomes dominant have been delimited, their transit being insignificant. The movement directions of easily soluble salts in soil are also highlighted on the map.From a naturalistic point of view, the map highlights the close connection between areas with accumulation of salts and areas where geological, geomorphological and hydrogeological conditions lead to a poor drainage. It also highlights the connection and importance of salt sources from geological deposits or salt masses in the hilly area in the formation, expansion and chemistry of saline soils in the plain or floodplain areas located in the neighbouring lowlands.

Biogas separation by semiclathrate hydrates formed with tetra-n-butylammonium and tetra-n-butylphosphonium salts

CH4/CO2 gas separation which frequently appears in biomass energy remains as a kind of challenge for gas hydrates, since these two molecules are similarly preferred by the hydrate phases. Semiclathrate hydrates can improve gas capture preference from the canonical gas hydrates by unique phase behavior. In this study, we perform parametric gas separation tests by the semiclathrate hydrates formed from major four ionic guests, i.e., TBAB, TBAC, TBPB and TBPC with pressure conditions of 1, 3 and 5 MPa and aqueous salt concentrations of 0.10, 0.20, 0.30 in mass fraction. The captured CO2 amounts basically increased with aqueous concentrations. The highest CO2 capture amount was obtained by the TBAB solution with 0.30 in salt mass fraction. TBAC showed the highest CO2 selectivity, while interestingly, the lower the pressure, the higher the CO2 composition in the TBAC hydrate phase, which means that the low-cost operation without high compression of biogas could be feasible and reasonable with this material. TBAB showed relatively simple behavior compared to N2 + CO2 and H2 + CO2 systems. The present results showed that it is possible to eliminate CH4 and enrich CO2 in the hydrate phase when the ionic guest and thermodynamic conditions are appropriately chosen.

Meaningful Metrics for an Efficient Solvent-Free Formulation of Polymer – Argyrodite Hybrid Solid Electrolyte

Solid-state batteries generate huge excitement with the promise of higher energy density than current Li-ion technology, thanks to the use of lithium metal at the anode1. Recent advancements in ceramic electrolytes demonstrate comparable conductivity with liquid ones2. However, the brittleness of ceramics results in mechanical limitations, during both assembly and cycling3, constraining the scale-up of pure-ceramic batteries. Hybrid solid electrolytes (HSE) can overcome this hurdle by combining the superior ionic conductivity of inorganic fillers with the scalable process of polymer electrolytes in a unique material. Depending on the amount of ceramic electrolyte, two types of HSE can be prepared: a ceramic-in-polymer approach, in which the inorganic filler disturbs the polymer crystallinity; and a polymer-in-ceramic system where the organic electrolyte mainly acts as a binder. Many parameters such as polymer molar mass, type and concentration of Li salt, chemistry and size of ceramic particles and the mixing route, make the HSE formulation an intricate process. As a result, there is a large disparity in the reported formulations and performances of HSE4. In particular, most approaches focus on a slurry-assisted preparation, which becomes a limiting factor when using sulfide-based electrolytes, as these ceramics degrade in common solvents used for binder processing5.To circumvent these issues, we propose a novel, solvent-free HSE preparation, combining an organic matrix based on poly(ethylene oxide) and lithium bis(trifluoromethanesulfonyl)imide (PEO:LiTFSI), with the highly conductive argyrodite-type Li6PS5Cl. The optimization of the HSE formulation is driven by key metrics, defined as sufficient ionic conductivity (σion ≥ 10-4 S.cm-1 @25°C) and adequate mechanical characteristics (self-standing property and ability to process as thin membrane <100 µm). Through rational screening, we elucidate the impact of formulation parameters and find the organic-to-inorganic ratio, the polymer molar mass and the ratio of mixed polymer lengths to be factors of paramount importance. Our methodology leads to an optimized formulation of the HSE with high ceramic content (75 wt.%) that meets the fixed criteria. Furthermore, we introduce an activation mechanism fitting (Arrhenius or Vulger-Tammann-Fulcher) as a new and effective metric to unravel the ionic pathway within the HSE. A shift in both ionic conductivity, mechanical cohesion and type of activation mechanism is observed at a unique threshold of 75 wt.% ceramic content. We show that our optimized polymer-in-ceramic HSE provides enhanced conduction through the ceramic network (10-4 S.cm-1 @25°C), displaying an Arrhenius activation, compared to ceramic-in-polymer HSEs, which behave as conventional PEO:LiTFSI following a VTF model. This gain in conductivity coincides with a higher mechanical resistance, as confirmed by tensile test on HSE membranes. Probing the compatibility of the organic and inorganic phases, using electrochemical impedance spectroscopy (EIS) alongside solid-state nuclear magnetic resonance (ssNMR), reveals the formation of an interphase, the quantity and resistivity of which grow with time and temperature. Finally, electrochemical performances are evaluated by assembling an HSE-based battery, which displays comparable stability as pure-ceramic ones (> 100 cycles before reaching 20% capacity loss at C/5) but still suffers from higher polarization and thus lower capacity (130 vs 150 mAh.g-1 at C/20). Janek, J. et al., Nat Energy 1, 16141 (2016).Abakumov, A. et al., Nat Commun 11, 4976 (2020).Doux, J.-M. et al., J. Mater. Chem. A 8, 5049–5055 (2020).Horowitz, Y. et al., J. Electrochem. Soc. 167, 160514 (2020).Ruhl, J. et al., Adv. Ener. Sust. Res. 2, 2000077 (2021).

Gamma-ray spectra of post-irradiated uranium salt for total mass accounting with sodium-22 tracer

In order to meet the safeguard requirements for Nuclear Material Control and Accountability (MC&A) in liquid-fueled molten salt reactors, fuel salt transportation, and fuel cycle processes, it is important to develop effective methods for measuring and monitoring the mass of molten fuel salt or coolant salt. This paper seeks to validate the radioactive tracer dilution (RTD) method used for determining the mass of irradiated uranium-bearing molten salt. Small scale testing was conducted for this method by irradiating 6.065 g of MgCl–KCl–UCl3 salt mixture with 1.21 mg of 235U at The Ohio State University, resulting in a neutron fluence of 4.0 × 1016 n/cm2. Gamma spectra were acquired over the course of a 42-day period starting in March 2023 to assess fission products and activity levels of the 22Na tracer that was added before irradiation. No additional interference peaks were observed to overlap with the 1274.54 keV energy peak from 22Na, aside from the known 154Eu peaks, which can be corrected based on prior studies. By placing a thin piece of lead between the source and detector, deadtime was effectively reduced while still allowing observation of the higher-energy peaks, most notably around the 154Eu peak at 1004.76 keV used for interference correction. Overall, the uranium salt irradiation techniques applied in this experiment demonstrate the potential of the RTD method to effectively measure small irradiated samples for large scale molten fuel salt applications.

Engineering A Boron-Rich Interphase with Nonflammable Electrolyte toward Stable Li||NCM811 Cells Under Elevated Temperature.

Despite the high energy of LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) cathode, it still suffers serious decay due to the continuous solvents decomposition and unstable cathode electrolyte interphase (CEI) layers, especially under high temperatures. The intense exothermic reaction between delithiated NCM811 and flammable electrolyte, on the other hand, pushes the batteries to their safety limit. Herein, these two issues are tackled via engineering the electrolytes, that is, utilizing salts with higher HOMO levels and nonflammable solvents with lower HOMO levels, to reduce the massive decomposition of solvents and improve battery safety under elevated temperatures. Consequently, a thin and boron-rich CEI is generated, which effectively inhibited the side reactions, thus improving the cycling stability and safety. Deviated from the highly concentrated electrolytes which heavily relies on the usage of massive salts, the electrolyte recipe can introduce a robust inorganic-rich CEI but use much less salt (i.e., dilute electrolyte), and thus, offer an encouraging alternative toward practical applications. As such, the NCM811 cathode exhibits a high-capacity retention of 81.2% after 950 cycles at 25°C and 75% after 300 cycles at 55°C. This work provides a universal electrolyte design strategy for designing stable and safe high-temperature electrolytes for the NCM811 cathode.

A Multidisciplinary Investigation of an Abandoned Old Mining Area Which Has Been Affected by the Combined Influences of Salt Karst and Human Exploration Activity

The authors discuss a case that is full of examples of the problems faced by civil engineers whose task is to develop areas in the face of natural, technological, or post-mining hazards. The study area is in the central part of Inowrocław, a town located on a massive salt dome of Zechstein salts. A strong deformation zone expanded in its upper part; this was caused by a natural process (related to so-called salt karst) and by mining activities that occurred in the past, creating a problem with regard to any potential spatial development in the town. The authors show a combination of data obtained using gravimetric and geodetic methods, which helps us to assess the geohazard risk. These include remote sensing data, which can be used to evaluate displacements of the ground surface. The authors used an approach that they term the Elevation Difference Method. This consists of determining displacements between ground surfaces: estimated on the basis of remote sensing data and on the basis of the historical data, when mounted measurement points (and remote sensing data) did not exist. The authors discuss the results in the light of the geological background. Within the area of the study, the displacements of the positive values dominate. The displacement occurs at 6 mm/yr on average and indicates diapiric uplift movement. The results are important for the town authorities for planning and development and for infrastructure management.

"Greening" of the industrial technology of enoxaparin sodium synthesis

The aim: carrying out stages of synthesis of intermediates of Enoxaparin sodium, considering the variation of synthesis parameters. Correlation analysis between the technological parameters of the synthesis and the quality of the obtained samples. Evaluation of the influence of the quality of semi-finished products on the quality of the final substance. Implementation of the principles of green chemistry in the synthesis of Enoxaparin sodium by reducing the production cycle and using the most environmentally friendly solvents and reagents. Materials and methods: samples of intermediates of the substance Enoxaparin sodium were synthesized according to the method described in the patent, as well as with a variation of the selected critical technological parameters. The obtained samples of intermediate products were analyzed according to the internal specification. In addition, an NMR-spectroscopy analysis was carried out for detailed structural characterization of Enoxaparin sodium intermediate molecules. Results: the method of synthesis of intermediates of the Enoxaparin substance proposed in the patent was evaluated and the critical parameter for the formation of the final molecule was selected, namely the reaction mass holding time. The intermediate of Enoxaparin sodium - benzethonium salt of heparin and benzyl ester of heparin were developed according to the selected parameters and the analysis of the obtained samples was carried out according to the internal ND. Taking into account the principles of green chemistry, the method of synthesis of the intermediate product - benzyl ester of heparin was optimized by solvent regeneration. Conclusions: As a result of the research, the methods of synthesis of intermediates of Enoxaparin were evaluated and the technological parameters of the synthesis of intermediates were determined, allowing to obtain a substance equivalent to the original Clexane® and Lovenox®. Evaluation of the method of synthesis of intermediate products according to the principles of green chemistry was carried out. The possibilities of greening the synthesis were analyzed. The holding time of the reaction mass of the benzethonium salt of heparin was reduced from 6 to 4 hours, and the benzyl ester of heparin from 25 to 22 hours. The E-factor indicator was reduced by regeneration of the solvent at the stage of synthesis of heparin benzyl ester

Intercomparison of marine tracer and catchment-based submarine groundwater discharge estimates for a karst aquifer

Submarine groundwater discharge (SGD) is a major source of solutes to the ocean. Consequently, the accuracy of estimates of the magnitude and seasonal variability of SGD is critical for the management of coastal marine ecosystems. However, very few intercomparison studies between different conceptual approaches have been made to assess the reliability and consistency of SGD flow estimates while simultaneously gauging the applicability of underlying models and budget assumptions in real-world scenarios. To date, intercomparison efforts have focused on homogeneous aquifers, and less so on highly heterogeneous aquifers such as karst systems. Here we compare the results of tracer-based (salt mass balance, tidal prism and radon mass balances) and catchment-based methods (water balance, semi-distributed karst network model) to assess SGD at a data-rich coastal location. All approaches tested here reveal a positive relationship between SGD fluxes and groundwater level measured close to the preferential groundwater flow pathways in the phreatic karst aquifer (e.g. water-saturated conduits or fracture network). We use this finding to derive site-specific relationships between groundwater level and SGD flow rates. We derive these relationships from least square fitting of Darcian and Non-Darcian models and regression analysis. The relationships validate the findings derived independently from hydraulic/hydrogeological modelling of the complex karst networks. By combining various estimates made with distinct assumptions, this method produces robust estimates of the SGD seasonal variability, essential to develop optimal management strategies of SGD resources in coastal karstic regions. Where direct measurements of SGD are not possible, monitoring of coastal groundwater level close to preferential phreatic groundwater pathways can be thus used as a useful indicator to compare past groundwater flow measurements and derive site-specific relationships, particularly in settings where large flow rate changes are present such as karst aquifers.

Optimization of Irrigation of Wine Grapes with Brackish Water for Managing Soil Salinization

Water scarcity and quality are critical impediments to sustainable crop production. In this study, HYDRUS-2D was calibrated using field measurements of water contents and salinities in the soil under wine grapes irrigated with river water (Rw, 0.32 dS/m). The calibrated model was then used to evaluate the impact of (a) four different water qualities ranging from 0.32 (Rw) to 3.2 dS/m (brackish water, Gw) including blended (Mix) and monthly alternating (Alt) irrigation modes; (b) two rainfall conditions (normal and 20% below normal); and (c) two leaching options (with and without 30 mm spring leaching irrigation) during the 2017–2022 growing seasons. Irrigation water quality greatly impacted root water uptake (RWU) by wine grapes and other water balance components. Irrigation with brackish water reduced average RWU by 18.7% compared to river water. Irrigation with blended water or from alternating water sources reduced RWU by 8.8 and 7%, respectively. Relatively small (2.8–8.2%) average annual drainage (Dr) in different scenarios produced a very low (0.05–0.16) leaching fraction. Modeling scenarios showed a tremendous impact of water quality on the salts build-up in the soil. The average electrical conductivity of the saturated soil extract (ECe) increased three times with Gw irrigation compared to Rw (current practices). Blended and alternate irrigation scenarios showed a 21 and 28% reduction in ECe, respectively, compared to Gw. Irrigation water quality substantially impacted site-specific actual basal (Kcb act) and single (Kc act) crop coefficients of grapevine. Threshold leaching efficiency estimated in terms of the salt mass leached vs. added (LEs; kg/kg) for salinity control (LEs &gt; 1) was achieved with LFs of 0.07, 0.12, 0.12, and 0.15 for the Rw, Mix, Alt, and Gw irrigations, respectively. Applying annual leaching irrigation (30 mm) before bud burst (spring) in the Mix and Alt with Rw and Gw scenarios was found to be the best strategy for managing irrigation-induced salinity in the root zone, lowering the ECe to levels comparable to irrigation with Rw. Modeling scenarios suggested that judicious use of water resources and continuous root zone monitoring could be key for salinity management under adverse climate and low water allocation conditions.

Geometry and kinematics of the Middle to Late Miocene salt tectonics, central Egyptian Red Sea margin

The Red Sea basin includes a thick Middle to Late Miocene evaporitic succession that underwent halokinesis and caused intensive reshaping of the seafloor and the development of salt-tectonic structures. However, the geometry and kinematics of these structures are still poorly understood. This study uses 2D and 3D seismic surveys and well data of the northern Egyptian Red Sea to systematically describe the distribution and morphology of salt structures, discuss their initiation, and construct a kinematic model for their origin. Our results indicate that the massive salt layer developed into five major NW-SE to NNE-SSW trending salt walls, characterized by relatively irregular crests and moderately dipping flanks. In addition, several symmetrical and asymmetrical folds and two categories of normal faults (subsalt and suprasalt) have been recognized. Based on our observations, salt mobilization in the study area started in the Late Miocene, during the precipitation of layered evaporites, and continued until the present day. In the northern Egyptian Red Sea, seismic interpretation indicates that halokinesis was triggered by a combination of thin- and thick-skinned systems, where the latter played a major role. The salt layer was welded during the Quaternary as several sags and grabens developed above the salt diapirs. Thick-skinned physical models are compatible with our observations, supporting the impact of basement faulting on Red Sea diapirism.

Transition from a Sponge-Like to an Onion-Like Nanostructure in the L3 Phase – Part I

HypothesisIn the phase diagram of the system H2O/NaCl – AOT (sodium bis(2-ethylhexyl) sulfosuccinate) a homogeneous L3 channel can be detected at T = 25 °C as a function of the surfactant and the NaCl mass fraction. Our hypothesis is that a structural transition from a sponge-like to an onion-like structure occurs in this channel. ExperimentsWe (a) determined the relevant part of the phase diagram, (b) carried out electrical conductivity and viscosity measurements, (c) visualized the nanostructure with freeze-fracture electron microscopy (FFEM) and freeze fracture direct imaging (FFDI), (d) determined the characteristic length scales from Small Angle Neutron Scattering (SANS) curves. FindingsWe detected a narrow one-phase L3 channel in which the conductivities decrease, while the viscosities increase with increasing surfactant and salt mass fractions. Together with the FFEM/FFDI images and the SANS curves we provide experimental evidence for a structural transition from a sponge-like to an onion-like structure: all structures as well as their coexistences are thermodynamically stable.

Investigating the Impact of Seawater Intrusion on the Operation Cost of Groundwater Supply in Island Aquifers

AbstractManaging fragile island freshwater resources requires identifying pumping strategies that trade off the financial cost of groundwater supply against controlling the seawater intrusion (SWI) associated with aquifer pumping. In this work, these tradeoffs are investigated through a sensitivity analysis conducted in the context of an optimization formulation of the groundwater management problem, which aims at minimizing the groundwater supply operation cost associated with groundwater pumping and desalination treatment, subject to constraints on SWI control, as quantified by the water table drawdown over the well (∆s), the reduction in freshwater volume (∆FV) in the aquifer, or the salt mass increase (∆SM) in the aquifer. This study focuses on a simplified two‐dimensional model of the San Salvador Island aquifer (Bahamas). Pumping strategies are characterized by the distance of the pumping system from the shoreline (WL), the abstraction screen depth (D) and overall pumping rate (Q), constituting the decision variables of the optimization problem. We investigate the impacts of pumping strategies on the operation cost, ∆s, ∆FV and ∆SM. Findings indicate increasing D or decreasing WL reduces ∆s, ∆FV and ∆SM, thus preserving the aquifer hydrogeologic stability, but also leads to extracting saltier groundwater, thus increasing the water treatment requirements, which have a strong impact on the overall groundwater supply cost. From a financial perspective, groundwater abstraction near the island center and at shallow depths seems the most convenient strategy. However, the analysis of the optimization constraints reveals that strategies where the pumping system approaches the island center tend to cause more severe SWI, highlighting the need to trade off groundwater supply cost against SWI control.

The Role of In‐Cloud Wet Removal in Simulating Aerosol Vertical Profiles and Cloud Radiative Forcing

AbstractAmong the physical processes controlling aerosol vertical profiles, in‐cloud wet removal is of utmost importance while its representation in global climate models (GCMs) is crude. In this study, we implement into the Community Atmosphere Model version 6 (CAM6) a physically‐based aerosol wet removal parameterization scheme that explicitly treats aerosol activation, removal and resuspension. Evaluation against in‐situ observations shows that the default scheme substantially overestimates the upper tropospheric black carbon (BC) and sea salt mass. Our physically‐based scheme reduces BC and sea salt mass by a factor of 10 and 1,000, respectively, in better agreement with observations. Also, the new scheme slightly increases number of aerosol particles between 12 nm and 4.8 μm in diameter, thereby mitigating the aerosol number underestimation in the default scheme. Our new scheme reduces the overestimation of coarse‐mode aerosol (0.5–4.8 μm) number. Overall, the aerosol property changes (mass decrease and number increase) reduce the cloud condensation nuclei (CCN) concentration at low supersaturation (i.e., 0.02% and 0.1%), and increase CCN at high supersaturations (i.e., 0.5% and 1%). Consequently, the global annual mean cloud liquid water path increases by 1.89 g m−2 and the ice water path increases by 0.51 g m−2. The global annual mean shortwave, longwave, and net cloud radiative forcing change by −1.06, 0.57, and −0.48 W m−2, respectively. Further improvement is needed to reflect the real physics that the removal efficiencies for aerosol mass and number are disproportionate and to advect cloud‐borne (activated) aerosols for a complete aerosol lifecycle.

Uncertainty quantification in coastal aquifers using the multilevel Monte Carlo method

AbstractWe are solving a problem of salinisation of coastal aquifers. As a test case example, we consider the Henry saltwater intrusion problem. Since porosity, permeability and recharge are unknown or only known at a few points, we model them using random fields and random variables. The Henry problem describes a two‐phase flow and is non‐linear and time‐dependent. The solution to be found is the expectation of the salt mass fraction, which is uncertain and time‐dependent. To estimate this expectation, we use the well‐known multilevel Monte Carlo (MLMC) method. The MLMC method takes just a few samples on computationally expensive (fine) meshes and more samples on cheap (coarse) meshes. Then, by building a telescoping sum, the MLMC method estimates the expected value at a much lower computational cost than the classical Monte Carlo method. The deterministic solver used here is the well‐known parallel and scalable ug4 solver.

Mitigating seawater intrusion in coastal aquifers: Novel approach with treated wastewater injection and groundwater circulation

Seawater intrusion (SWI) is a natural phenomenon that negatively impacts the potability of groundwater and is expected to worsen with rising sea levels due to climate change. Artificial recharge of freshwater is a commonly-used remediation method to mitigate SWI and improve freshwater supply security in affected coastal aquifers. However, limited freshwater availability can limit the effectiveness of this approach. This study proposes a novel mitigation measure, called Inj-GCW, which combines the injection of reclaimed water with the use of groundwater circulation wells (GCW) to enhance the effectiveness of artificial recharge in controlling SWI. GCW is a dual-screened well with isolated screens that extract and inject groundwater into the aquifer. The performance of the proposed measure was quantitatively evaluated using an illustrative simplified unconfined coastal aquifer. Based on the findings, the design parameters were estimated for a field-scale case study of the Nile Delta aquifer (NDA), a large Mediterranean coastal aquifer in Egypt. The study adopts a future scenario that considers Sea-level rise due to climate change and projected population growth by 2100. Results demonstrate that introducing of GCWs into the saltwater wedge, along with injection, effectively retreated the saltwater wedge, due to enhanced velocity, seaward fluxes, and dilution of contamination. Inj-GCW measure led to an 8.9% reduction in SWI and a 5.2% decrease in aquifer salinity compared to the expected intrusion in 2100. Furthermore, the Inj-GCW measure resulted in a 2.2% higher repulsion rate and 0.3% reduction in total salt mass compared to injection alone. The Inj-GCW measure presents a promising solution to SWI challenges in the NDA and other coastal aquifers facing similar issues. The formation of a brackish water bubble at the injection well screen of the GCW and the generated vertical groundwater circulation cells acted as a hydraulic barrier and contributed to the proposed method effectiveness.

Systematic laboratory investigations concerning the reduction of uncertainties related to the modeling of the material behavior of crushed salt

Abstract. The planned use of crushed salt as the backfill and sealing material in the context of the final disposal of radioactive waste in rock salt is justified and favored by the realization that the material properties of loosely deposited crushed salt will be transformed into the material properties of in situ rock salt in the long term by the convergence of the viscous rock salt mass. In other words, the convergence-induced compaction of crushed salt ultimately results in a nearly pore-free material, with a tightness and creep capacity corresponding to that of the ambient rock salt mass. The computational prognosis of the load-bearing and sealing behavior required for the long-term safety assessment of underground repositories requires a sufficiently proven physical modeling of the, in general, three-dimensional load bearing and permeability behavior of crushed salt. This requirement can only be met if the influencing variables on the load bearing and permeability behavior are sufficiently quantified and represented by mathematical–physical functions on the basis of suitable laboratory and field investigations. In order to eliminate or reduce the currently (still) existing scientific deficits and uncertainties concerning the general three-dimensional load bearing and permeability behavior of crushed salt, a systematized laboratory program was developed within the framework of the joint project KOMPASS (compaction of crushed salt for the safe containment), with the aim of ensuring an isolated recording of individual processes and influencing factors on the compaction behavior. Based on this, triaxial long-term compaction tests, TUC-V2 and TUC-V4, with a test duration of 750 and 180 d, respectively, were carried out within the framework of the joint project KOMPASS and of the follow-up project KOMPASS II. Both tests, but especially TUC-V2 with its 2-year duration, represent a sequence of several loading phases for separate analysis of the effects of individual influencing factors on the compaction behavior of crushed salt. By integrating several loading phases in one long-term test each, it was possible, on the one hand, to eliminate the scattering of the material behavior that would have been expected if several individual tests had been carried out as an alternative and, on the other hand, to provide metrological evidence of the range of validity of the compaction behavior as a function of individual influencing factors for a comparatively wide range of different porosities in each case. The computational reanalysis of the long-term tests opens up the possibility of validating and strengthening the currently available constitutive model approaches with regard to their ability to influence several parameters on the compaction behavior, while eliminating the scatter band of the material behavior. The improvement of the existing constitutive model approaches up to the sufficient reproduction of the measurement results equals an increase in the validation status or the credibility of the constitutive models or, vice versa, a reduction in the uncertainties remaining due to (not yet) validated model assumptions. Within the framework of the KOMPASS II joint project, a benchmark was carried out against the background outlined above for the comparative analysis of the constitutive models currently available to the project partners for depicting the compaction behavior of crushed salt with regard to their ability to computationally represent the measurement results generated within the TUC-V2 experiment. Specifically, the focus is on constitutive model functions that control the viscous compaction and shear deformation behavior and, within these functions, the influencing factors of mean stress, deviatoric stress, and temperature, which were recorded by laboratory tests for medium ranges of porosities from ≈ 16 % to very low porosities of ≈ 2.5 %. Within the framework of the continuation of the investigations planned under the acronym MEASURES (Multi-scale Experimental and numerical Analysis of crushed Salt material Used as engineered backfill for a nuclear waste REpository in rock Salt), it is intended to continue the benchmark study with a more detailed investigation of the influence of the deviatoric stress, which includes considering the data from TUC-V4. It is also intended to supplement the laboratory data base with further experiments by (a) investigations on the compaction behavior in the range of high-to-medium porosities and (b) investigations on the influence of the moisture content on the compaction capability (to be performed with KOMPASS reference material).

Evaluating a Dual-Ion Battery with an Antimony-Carbon Composite Anode.

Dual-ion batteries (DIBs) are attracting attention due to their high operating voltage and promise in stationary energy storage applications. Among various anode materials, elements that alloy and dealloy with lithium are assumed to be prospective in bringing higher capacities and increasing the energy density of DIBs. In this work, antimony in the form of a composite with carbon (Sb-C) is evaluated as an anode material for DIB full cells for the first time. The behaviour of graphite||Sb-C cells is assessed in highly concentrated electrolytes in the absence and presence of an electrolyte additive (1 % vinylene carbonate) and in two cell voltage windows (2-4.5 V and 2-4.8 V). Sb-C full cells possess maximum estimated specific energies of 290 Wh/kg (based on electrode masses) and 154 Wh/kg (based on the combined mass of electrodes and active salt). The work expands the knowledge on the operation of DIBs with non-graphitic anodes.

Efficacy of urban road salt reduction strategies on public supply well quality

Long-term road salt application has increased chloride (Cl−) concentrations in public drinking water wells in many cold climate communities. A range of Best Management Practices (BMPs) have been adopted to mitigate the impact of road deicing compounds on groundwater quality. Chronic increases in chloride levels have been observed in several municipal well fields within the southern Ontario Regional Municipality of Waterloo (RMOW). In response, the RMOW and City of Kitchener implemented a plan to reduce salt application on roads by 25% within the local capture zones of one of the impacted well fields, the Greenbrook Well Field. Here the influence of salt reduction BMPs on subsurface water quality are examined by documenting changes in pore water Cl− concentrations and stored salt mass in vadose zone core samples collected at sites near the well field both before and after the implementation of the BMPs. The data indicate that ~6 years after salt reduction measures were initiated, average pore water Cl− concentration and average cumulative stored chloride mass in the vadose zone had decreased by approximately 60% and 40%, respectively. Groundwater samples collected from shallow monitoring wells installed at each field site showed similar post-BMP reductions in shallow groundwater Cl− concentration (~35%). Long-term (1973–2022) trends in raw water Cl− concentration data from the deeper public drinking water supply wells clearly demonstrate a slow, time-lagged response of the municipal supply wells to the salt reduction BMPs. The combined results suggest that controlled reductions in road salt applications within vulnerable, capture zone regions of public supply wells can reduce the impact of road salt deicing practices on municipal groundwater supplies over time.