Salt Transport Research Articles

Characterization of porewater exchange process and salt release-transport model of multiple geomorphological units in the supratidal zone of muddy tidal flat in semi-arid climate

In the muddy tidal flat controlled by semi-arid climate, porewater exchange (PEX) drives beach surface salt to recharge phreatic brine resources. However, in the Supratidal zone with multiple geomorphological units, the PEX process of such complex areas is still unclear. This study takes the supratidal zone with multiple geomorphological units distributed in the mudflat of Laizhou Bay as the study area. Based on electrical resistivity tomography (ERT) survey and groundwater multi-parameter measurement, the spatiotemporal distribution of salinity in different geomorphological units was described, and the salt release-transport process of these units was finely characterized. The results show that there are spatiotemporal differences in salt distribution in the multi-geomorphological units, and the PEX process is affected by hydraulic gradient, salinity gradient, sediment hydraulic conductivity and bioturbation. The crab burrows enhance the degree of water-salt exchange in the units and drive the salt transport to deeper layers, which leads to the differences in the salt transport process among various units in the PEX. In addition, Due to PEX, the recirculated seawater carries a large amount of salt back to the ocean and accumulate salt at the bottom of the tidal creek during the ebbing tide. Compared with the high tide, the salinity change ratio of the bottom of the tidal creek at the low tide is 261%.

A Baroclinic Fluid Model and Its Application in Investigating the Salinity Transport Process Within the Sediment–Water Interface in an Idealized Estuary

Understanding the salinity transport process around the sediment–water interface is important for water resources management in the upper reach of an estuary. In this study, we developed a baroclinic fluid dynamic model for investigating the flow and salt transport characteristics within the sediment–water interface under tidal forcing. The validation showed robust model performance on the salinity transport within the sediment–water interface. The results revealed that the turbulent kinetic energy, dissipation rate, and kinetic energy production rate exhibited periodic variations within the seabed boundary layer. The thickness of the viscous sublayer and the mean flow showed an inverse relationship. Water and salinity exchange within the sediment–water interface occurred predominantly via turbulent diffusion, with extreme turbulent kinetic energy production rates appearing during the tidal reversal, flood, and ebb stages. The sediment acted as a source of salinity release during ebb tides and a sink for salinity absorption during flood tides. As the sediment depth increased, fluctuations in salinity were weakened. These results clearly illustrated that the sediment layer is important in modulating the salinity transport in the upper reach of an estuary. However, such an important process was usually excluded by previous studies. The model developed in this study can be used as a sediment–water interface module that, coupled with other hydrodynamic models, can evaluate the contributions of the sediment layer to the salinity exchange in coastal water.

Test Study on Water and Salt Transport in Soil Transition Layer under Water Storage Irrigation Based on Big Data Technology and its Mechanism

At present, it is necessary to vigorously transform saline-alkali wasteland, dry land and coastal tidal flat to realize the balance of cultivated land occupation and compensation. In this paper, the experiment and mechanism of water and salt transport in soil transition layer under water storage irrigation are studied by combining big data technology. Moreover, based on the basic principle of water and salt balance, the numerical model of water and salt transport in vadose zone of study area under brackish water irrigation is constructed on the basis of existing data. The model is a set of numerical models for simulating water transport, heat transport, solute transport and root water uptake in one-dimensional variable saturated media. The model analysis shows that soil water and salt transport is a complex natural phenomenon under the joint action of a large number of natural factors and human factors. In addition, this paper uses normal test analysis to find out whether the salt content of each soil layer conforms to the normal distribution, and combines with big data technology to perform mechanism analysis and verify the effectiveness of this method.

Effects of a subsurface dam on groundwater flow and salt transport in stratified coastal aquifers: Experiments and simulations

Subsurface dams are now widely used to mitigate seawater intrusion in coastal aquifers. Previous studies have mostly focused on the optimal design of subsurface dams under various conditions, but such an attempt in the context of a three-layered (a low-permeability layer in between two high-permeability layers) aquifer is lacked. In reality, many coastal aquifer exhibit such a geological layering feature. This study, using laboratory experiments and numerical simulations, filled the research gap. The results show that, the addition of a subsurface dam to a three-layered coastal aquifer may significantly prolong the particle travel times in both the freshwater zone and the saltwater wedge. Also, the saltwater-freshwater mixing zone in a stratified aquifer can be narrowed by a subsurface dam. However, this trend is reversed when the subsurface dam is located rather landward. Moreover, a subsurface dam may hinder the formation of “freshwater fingers”, which would have formed in aquifers with highly contrasting permeability coefficients between the three layers. Further analysis reveals high-level sensitivity of saltwater-freshwater mixing zone to the height and location of the subsurface dam, and the permeability of the low-permeability layer. These findings promote deeper insights into the impact of subsurface dams on the underground hydrodynamics in complex nearshore groundwater systems. More importantly, conclusions drawn from the study may help to evaluate the environmental impact and optimize the design of subsurface dams to be constructed, ultimately assisting the management of coastal fresh groundwater resources.

Thermal stability of PVDF-HFP based gel electrolyte for high performance and safe lithium metal batteries

Gel polymer electrolytes (GPEs) have garnered significant attention due to their efficacy in addressing safety concerns associated with liquid electrolyte leakage. However, the frail mechanical properties and low thermal stability of GPEs have constituted significant obstacles to their commercialization. In this paper, safe GPEs with excellent mechanical properties and high thermal stability were prepared by introducing high-strength and lithophilic cellulose acetate (CA) into PVDF-HFP gel electrolytes. The incorporation of CA facilitates the dissociation and transport of Li salts, and the formation of a hydrogen bonding network between the –OH of CA and the −F of the PVDF-HFP substrate was identified through FTIR testing. The thermal stability was elucidated through pyrolysis kinetics, and the activation energy was calculated. The pyrolysis products were compared through a TG-FTIR-MS test to demonstrate the high-temperature resistance of the FPF-CA membrane. The prepared GPEs exhibited high ionic conductivity (1.087 × 10−3 S/cm) and some self-extinguishing properties at room temperature, with a higher electrochemical window of 4.81 V and a high Li+ mobility number of 0.56. The capacity retention was 93% after 600 cycles at 1C.

Quantification of Salt Transports Due To Exchange Flow and Tidal Flow in Estuaries

AbstractTo understand mechanisms of salt intrusion in estuaries, we develop a semi‐analytical model, that explicitly accounts for salt transport by both exchange flow and tidal flow. This model, after calibration, successfully hindcasts hydrodynamics and salinity dynamics in three estuaries that have strongly different characteristics. We find, from analyzing the model results for these three estuaries, that salt transport processes by exchange flow and tidal flow interact through the subtidal stratification. Transport by exchange flow creates stratification, thereby generating a phase shift of tidal salinity with respect to the tidal flow, which is important for the magnitude of the tidal salt transport. Conversely, the strength of tidal currents determines the vertical mixing that breaks down stratification. A new analytical formulation is presented for the component of the salt transport driven by the depth‐averaged tidal flow. This salt transport is larger than the component associated with the vertical shear of the tidal current. Finally, a method that yields analytical equations that quantify the importance of different contributions to the salt transport using only primary information is developed using approximate solutions for the subtidal stratification. This method performs well for the estuaries considered.

Mechanistic Simulation of Salt‐Affected Soil‐Plant‐Atmosphere Continuum Dynamics in Seasonally Frozen Regions

AbstractThe salt‐affected Soil‐Plant‐Atmosphere Continuum (SPAC) is a dynamic, interactive system that is particularly complex in seasonally frozen regions where salt transport, precipitation‐dissolution, and soil freeze‐thaw processes play crucial, interrelated roles. Understanding these coupled processes and representing them with mathematical models is critical for effective management of SPAC systems. This study presents a new mechanistic approach and an improved model that integrates a chemical equilibrium module within a mechanistic‐based transport computational module (modified SHAW model). The chemical equilibrium module determines salt precipitation‐dissolution using thermodynamic theory and explains the effects of efflorescence and subflorescence on system dynamics. The model enables simultaneous solutions for heat, water, and salt transport with chemical equilibrium throughout non‐freezing and freezing seasons, as well as plant growth dynamics. Assessment of the model using laboratory experiments and field studies showed good performance, with coefficient of determination values exceeding 0.65 for simulated and measured evaporation rate, leaf area index, soil water content, salt content, and temperature. Furthermore, a comparison between simulation results considering and neglecting the impact of salt precipitation‐dissolution highlights potential inaccuracies in soil heat‐water‐salt dynamics and plant water use resulting from the omission of this process in mechanistic models.

Long-term rice cultivation enhances root development and yields by improving the structural properties of soil aggregates in saline–alkaline environments

Rice cultivation has the ability to improve saline soils. However, the effects of long-term rice cultivation on saline soil chemistry, salt ions, root characteristics, and aggregate formation remain unclear. In this study, the impact of different planting durations (1, 3, 5, 8, and 10 years) on the spatial and temporal transport of soil salts, soil chemical properties, distribution and stability of aggregates, root characteristics, and yields, were assessed. Long-term rice cultivation reduced soil pH, exchangeable sodium percentage (ESP), and EC in the 0-60cm soil layer compared to 1Y (5.45%, 61.57%, and 81.87% reduction in topsoil (0-20cm) and 8.54%, 72.82%, and 71.94 in subsoil (20-60cm), respectively). However, the soil organic matter (OM), alkaline nitrogen (AN), phosphorus (AP), and potassium (AK) increased (217.09%, 90.18%, 89.23%, and 179.18% increase in topsoil and 223.72%, 81.24%, 174.28%, and 172.57% increase in subsoil, respectively). Additionally, the Cl-, K+, and Na+ in the soil gradually leached downward with the increase in the duration of rice cultivation (55.87%、36.08%、59.80%). Simultaneously, the increased duration markedly elevated the soil macroaggregate content (11.43%-20.04% by dry-sieving and 53.48%-288.09% by wet-sieving), clayey grain content (59.17%-198.33%), and soil aggregate stability, especially for 8Y and 10Y. The improved soil structure and root characteristic under long-term rice cultivation conditions increased the yield (28.89-54.81%). Partial least squares path model displayed that rice cultivation affected the aggregate stability, root characteristics, and rice yield via the corresponding chemical properties (pH, EC, and ESP), nutrient contents (AN, AP, AK, and SOM), and salt ion contents (Cl-, K+, and Na+). These findings are critical to understanding aggregate formation in saline soils.

Simulation of water-salt transport and balance in cultivated-wasteland system based on SWAP model in Hetao Irrigation District of China

Water and salt transport among different use type land is important to irrigation management in arid area. In this study, a typical irrigation unit including cultivated land and wasteland in Hetao Irrigation District of China was selected to explore water and salt transport between cultivated land and wasteland system. Soil water-salt dynamics, groundwater depth and salinity were observed within the period of crop growing and autumn irrigation period in 2018 and 2019. Calibrated SWAP model was used to simulate water and salt flux of cultivated land and wasteland during the crop growing period and autumn irrigation period. Furthermore, water-salt transport exchange capacity was calculated between cultivated land and wasteland system in study area. Groundwater was recharged by soil water and soil salt was leached in cultivated land during the crop growing period. Soil water was recharged by groundwater and soil salt was accumulated in saline wasteland during the crop growing period. During the crop growing period, the total leaching of soil salinity was 15.64 t·ha−1 in cultivated land. Soil salt accumulation was 2.03 t·ha−1 in saline wasteland. During the autumn irrigation period, the total leaching of soil salinity was 14.93 t·ha−1 in cultivated land. Total leaching of soil salinity was 1.56 t·ha−1 in saline wasteland. Overall, saline wasteland had an important role to receive salt from cultivated land and maintain salt dynamic balance in arid irrigation area with shallow groundwater.

Numerical study on the fluid flow and condensation heat transfer characteristics of two-phase NaCl-H2O fluids on the external swept spiral coil in a hydrothermal vent

The substantial thermal energy of two-phase NaCl-H2O hydrothermal fluids makes them a significant target for utilizing deep-sea energy. A fundamental understanding of the thermal performance of two-phase NaCl-H2O hydrothermal fluids during condensation is crucial for heat energy harnessing. It aims to obtain the flow and condensation heat transfer characteristics of two-phase NaCl-H2O fluids during the heat transfer process outside a spiral coil structure in this paper. The properties of the NaCl-H2O binary systems were adopted instead of pure water, and the salt transport equation was considered to reflect the impact of salinity change on heat transfer, making the simulation more representative of natural venting fluids. The results indicated a significant tangential velocity when the fluids externally swept the spiral coil. Secondly, the heat transfer area can be divided into the “normal region” and the “island region,” of which convection and condensation contribute to the heat transfer mechanisms. The “island region” formation was attributed to both vapor condensation and the spoiler effect caused by the spiral structure. Moreover, the heat flux increased with decreasing salinity in the “island region,” and a weak interaction was observed between heat flux and salinity in the “normal region.” Finally, the spiral structure's heat transfer performance was superior to the straight structure's. This investigation may provide a basis for designing and optimizing the heat transfer equipment for deep-sea hydrothermal extraction.

Amplified vertical salinity contrasts in the northwestern tropical Pacific under ocean warming

Analyses of vertically layered structures in ocean salinity present a recently amplified vertical contrast in the northwestern tropical Pacific, which has been attributed to the reversal of the long-term linear trend in salinity within the upper ocean from 1960 to 2023. Based on data obtained from both observations (Argo and WOD) and reanalysis (EN4), salinity trends shifted from freshening (− 0.04 psu/40 yr) to salinification (+ 0.04 psu/60 yr) in the near-surface (above 24.6 σθ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\sigma }_{\ heta }$$\\end{document} surface), while subsurface (below 25 σθ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\sigma }_{\ heta }$$\\end{document} surface) freshening further strengthened from – 0.03 psu/40 yr to – 0.1 psu/60 yr after 2000. The near-surface salinification can be partly explained by atmospheric forcing related to global warming. The anomalous cyclonic wind-induced Ekman suction and wind-driven horizontal salt transport were favorable for increased salinity in upper layers. Nevertheless, the oceanic dynamic forces governed the vertical salinity structure. Under a warming climate, heat influx and warm water accumulation due to diabatic effects play a deterministic role in isopycnal deepening. The changes in salinity evoked by isopycnal changes were investigated from two perspectives: entrainment at the bottom of 24.6 σθ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\sigma }_{\ heta }$$\\end{document} layer and heaving variabilities for the upper layers above 24.6 σθ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\sigma }_{\ heta }$$\\end{document}, were primary factors in near-surface salinification. However, the relative significance of heaving variabilities decreased with depth and the major controlling factor became contingent on spiciness variabilities. It is suggested that, owing to a northward migration of the outcrop line, subduction along the path of the geostrophic streamline from the ventilation region, where freshened spiciness anomalies can be injected into subduction surfaces, tended to dominate the significant freshening trend at subsurface isopycnals.

Temperature dependence of water and salt transport in concentration gradient batteries: Insight from membrane properties

The performance of concentration gradient batteries (CGBs) based on reverse electrodialysis technology is inevitably influenced by seasonal temperature fluctuations; however, these effects have not been thoroughly investigated. This study explored the temperature dependence of water and salt transport in CGBs using five different membranes over a temperature range of 5–45 °C to elucidate these impacts. The results indicated that the temperature dependence of current efficiency and voltage efficiency in CGBs was respectively controlled by permeation processes (including both water and salt) and membrane resistance. The temperature dependence of mass transfer in these membranes was associated with the characteristics of the species crossing the membrane (such as size) and, more significantly, with membrane properties, including water volume fraction and fixed charge density. Therefore, we proposed that controlling these membrane characteristics can modulate the influence of temperature on mass transfer and CGB performance. This research enhanced our understanding of how temperature affects mass transfer mechanisms in different membranes and provided valuable insights for improving energy conversion in CGBs and other membrane processes.

Improvement Effect of Straw Interlayer Thickness on Saline-Alkali Soil

In order to evaluate and optimize the application effect of straw interlayer technology in improving soil quality and crop production in saline-alkali soil, and to understand the synergistic relationship between soil water and nutrient distribution, crop roots and above-ground growth in saline-alkali soil, the improvement effect of straw interlayer thickness on saline-alkali soil was studied. Through the indoor root box control experiment combined with the field micro-zone verification experiment, four corn straw interlayer thickens were set (CK: no straw interlayer; S3: Straw layer thickness is 3 cm; S5: The straw layer thickness is 5 cm; S7: straw interlayer thickness is 7 cm), and the effects of straw interlayer thickness on soil water and salt transport and nutrient distribution are simulated. The results showed that straw interlayer could enhance the water retention and salt leaching capacity of 0–40 cm soil layer after irrigation, and S5 treatment had the best effect, with soil water content increased by 11.0% and salt content decreased by 4.0% compared with CK (P < A0.05). Compared with CK, straw separation treatment decreased the soil nutrient content in 0–40 cm soil layer (except alkali-hydrolyzed nitrogen and available potassium), and increased the soil nutrient content in 40–60 cm soil layer, and S5 treatment had the largest increase, in which available potassium was significantly increased by 15.0% compared with CK (P <0.05). Therefore, it shows that the straw interlayer can play a role in preventing water and reducing permeability, and can reduce the salt content of the soil above the interlayer, and has a good effect on the improvement of saline-alkali soil.

A comparison of sea-level rise and storm-surge overwash effects on groundwater salinity of a barrier island

Coastal fresh groundwater is threatened by salinization due to both sea-level rise and storm-surge overwash. Most studies of subsurface saltwater intrusion focus on sea-level rise, but storms that are becoming more frequent and intense with climate change could have more imminent and permanent effects on aquifer salinity. Few studies directly compare saltwater intrusion due to sea-level rise with saltwater intrusion due to storm-surge overwash, and no studies address this issue on barrier islands. In this study, a hydrological model simulating coupled, variable-density, surface and subsurface flow and salt transport was developed and calibrated to water level and specific conductance data at Assateague Island, MD. The calibrated model was used to calculate the mass of salt and the total volume of aquifer salinized in 2080 due to both sea-level rise and more frequent storm surges. The results suggest that the total mass of salt that intrudes into the aquifer due to changes in the 2-year storm surge height is approximately equal to that of sea-level rise (∼300 kg), and the surges salinize nearly the entire aquifer, exceeding the volume salinized by sea-level rise (∼80 %). The influence of aquifer properties and unsaturated zone thickness was investigated by reducing aquifer hydraulic conductivity, resulting in greater salinization from storm-surge overwash (100 % of aquifer volume) than from sea-level rise (∼20 %). Higher storm surges are expected to overtop the dunes on Assateague by 2080 causing a 75 % decline in areas above the 2-year storm event while sea-level rise will only inundate ∼ 40 % of the land area on Assateague. This analysis suggests that groundwater is likely more vulnerable to storm-surge overwash than to sea-level rise induced salinization, even in systems where sea-level rise is expected to be most severe.

Dye tracing of upward brine migration in snow

Abstract Salt is often present in the snow overlying seasonal sea ice, and has profound thermodynamic and electromagnetic effects. However, its provenance and behaviour within the snow remain uncertain. We describe two investigations tracing upward brine movement in snow: one conducted in the laboratory and one in the field. The laboratory experiments involved the addition of dyed brine to the base of terrestrial snow samples, with subsequent wicking being measured. Our field experiment involved dye being added directly (without brine) to bare sea-ice and lake ice surfaces, with snow then accumulating on top over several days. On the sea ice, the dye migrated upwards into the snow by up to 5 cm as the snow's basal layer became more salty, whereas no migration occurred in our control experiment over non-saline lake ice. This occurred in relatively dry snowpacks where brine took up $< 6\%$ of the snow's calculated pore volume, suggesting pore saturation is not required for upward salt transport. Our results highlight the potential role of microstructural parameters beyond those currently retrievable with penetrometry, and the potential value of longitudinal, process-based field studies of young snowpacks.

Impact of Irrigation on Soil Water Balance and Salinity at the Boundaries of Cropland, Wasteland and Fishponds under a Cropland–Wasteland–Fishpond System

In order to explore the effect of fishponds on soil water, salt transport and salinization in cropland wasteland, a study on soil water balance and salt distribution pattern in a cropland–wasteland–fishpond system was carried out in 2022–2023 in a typical study area selected from the Yichang Irrigation Area of the Hetao Irrigation District. A water balance model was established for the cropland–wasteland–fishpond system to analyze the effects of irrigation on soil salinity at the boundaries of the cropland, wasteland, and fishpond. The results showed that the lateral recharge from the cropland to the wasteland during spring irrigation in 2022 was 24 mm, the lateral recharge generated by fishponds to wasteland was 18 mm, and the lateral recharge from fishponds to fishpond boundaries was 34 mm. In the fertility period of 2023, the lateral recharge from cropland to wasteland was 15 mm, the lateral recharge from fishponds to wasteland was 9 mm, and the lateral recharge from fishponds to fishpond boundaries was 21 mm. Due to the low salinity content of fishpond water, it diluted the groundwater of the wasteland, and the soil salinity at the boundary between the wasteland and the fishpond was monitored. The data show that the soil salinity at the boundary of the fishpond was smaller than that of the wasteland, which indicates that the migration of fishpond water to the wasteland will not lead to an increase in the soil salinity of the wasteland, but rather to a decrease in the soil salinity of the wasteland. Fishpond regulation has a significant impact on soil and groundwater, and when the topographic conditions of the Hetao irrigation area allow, the model of cropland–wasteland–fishpond can be appropriately adopted to solve land degradation and increase the economic income of farmers; the results of the study provide a contribution for the improvement of the management of land use and soil salinization in the Hetao irrigation area.

The Link between Surface Visible Light Spectral Features and Water–Salt Transfer in Saline Soils—Investigation Based on Soil Column Laboratory Experiments

Monitoring soil salinity with remote sensing is difficult, but knowing the link between saline soil surface spectra, soil water, and salt transport processes might help in modeling for soil salinity monitoring. In this study, we used an indoor soil column experiment, an unmanned aerial vehicle multispectral sensor camera, and a soil moisture sensor to study the water and salt transport process in the soil column under different water addition conditions and investigate the relationship between the soil water and salt transport process and the spectral reflectance of the image on the soil surface. The observation results of the soil column show that the soil water and salt transportation process conforms to the basic transportation law of “salt moves together with water, and when water evaporates, salt is retained in the soil weight”. The salt accumulation phenomenon increases the image spectral reflectance of the surface layer of the soil column, while soil temperature has no effect on the reflectance. As the water percolates down, water and salt accumulate at the bottom of the soil column. The salinity index decreases instantly after the addition of brine and then tends to increase slowly. The experimental results indicate that this work can capture the relationship between the water and salt transport process and remote sensing spectra, which can provide theoretical basis and reference for soil water salinity monitoring.

Intraventricular haemorrhage in premature infants: the role of immature neuronal salt and water transport.

Intraventricular haemorrhage is a common complication of premature birth. Survivors are often left with cerebral palsy, intellectual disability and/or hydrocephalus. Animal models suggest that brain tissue shrinkage, with subsequent vascular stretch and tear, is an important step in the pathophysiology, but the cause of this shrinkage is unknown. Clinical risk factors for intraventricular haemorrhage are biomarkers of hypoxic-ischaemic stress, which causes mature neurons to swell. However, immature neuronal volume might shift in the opposite direction in these conditions. This is because immature neurons express the chloride, salt and water transporter NKCC1, which subserves regulatory volume increases in non-neural cells, whereas mature neurons express KCC2, which subserves regulatory volume decreases. When hypoxic-ischaemic conditions reduce active ion transport and increase the cytoplasmic membrane permeability, the effects of these transporters are diminished. Consequentially, mature neurons swell (cytotoxic oedema), whereas immature neurons might shrink. After hypoxic-ischaemic stress, in vivo and in vitro multi-photon imaging of perinatal transgenic mice demonstrated shrinkage of viable immature neurons, bulk tissue shrinkage and blood vessel displacement. Neuronal shrinkage was correlated with age-dependent membrane salt and water transporter expression using immunohistochemistry. Shrinkage of immature neurons was prevented by prior genetic or pharmacological inhibition of NKCC1 transport. These findings open new avenues of investigation for the detection of acute brain injury by neuroimaging, in addition to prevention of neuronal shrinkage and the ensuing intraventricular haemorrhage, in premature infants.

Effects of grid resolution on regional modelled groundwater salinity and salt fluxes to surface water

Coastal fresh groundwaters face growing threats from rising withdrawals and climate change, with salinization of surface and groundwater as notable impacts. Recent developments in parallel variable-density modelling enable studying these threats at unexplored resolutions and extents. To improve the understanding of ground- and surface water salinization processes, we designed an experiment to measure how spatial resolution affects both groundwater salinity distribution and salt loads to surface waters. An existing parallelized coupled variable-density groundwater flow and salt transport (VD-GWT) model is applied to a region in the Netherlands whereby the surface water drainage network is parameterized at grid resolutions between 10 and 250 m. The results show a strong dependency between resolution and the salinity distribution in shallow groundwater while simulated salt loads are affected by imperfect flux scaling. The computational resources needed for this test suggest that regional high-resolution VD-GWT models are feasible using HPC environments, albeit not practical.

Deletion of KS-WNK1 promotes NCC activation by increasing WNK1/4 abundance.

Dietary potassium deficiency causes stimulation of sodium reabsorption leading to an increased risk in blood pressure elevation. The distal convoluted tubule (DCT) is the main rheostat linking plasma K+ levels to the activity of the Na-Cl cotransporter (NCC). This occurs through basolateral membrane potential sensing by inwardly rectifying K+ channels (Kir4.1/5.1); decrease in intracellular Cl-; activation of WNK4 and interaction and phosphorylation of STE20/SPS1-related proline/alanine-rich kinase (SPAK); binding of calcium-binding protein 39 (cab39) adaptor protein to SPAK, leading to its trafficking to the apical membrane; and SPAK binding, phosphorylation, and activation of NCC. As kidney-specific with-no-lysine kinase 1 (WNK1) isoform (KS-WNK1) is another participant in this pathway, we examined its function in NCC regulation. We eliminated KS-WNK1 specifically in the DCT and demonstrated increased expression of WNK4 and long WNK1 (L-WNK1) and increased phosphorylation of NCC. As in other KS-WNK1 models, the mice were not hyperkalemic. Although wild-type mice under low-dietary K+ conditions demonstrated increased NCC phosphorylation, the phosphorylation levels of the transporter, already high in KS-WNK1, did not change under the low-K+ diet. Thus, in the absence of KS-WNK1, the transporter lost its sensitivity to low plasma K+. We also show that under low K+ conditions, in the absence of KS-WNK1, there was no formation of WNK bodies. These bodies were observed in adjacent segments, not affected by the targeting of KS-WNK1. As our data are overall consistent with those of the global KS-WNK1 knockout, they indicate that the DCT is the predominant segment affecting the salt transport regulated by KS-WNK1.NEW & NOTEWORTHY In this paper, we show that KS-WNK1 is a critical component of the distal convoluted tubule (DCT) K+ switch pathway. Its deletion results in an inability of the DCT to sense changes in plasma potassium. Absence of KS-WNK1 leads to abnormally high levels of WNK4 and L-WNK1 in the DCT, resulting in increased Na-Cl phosphorylation and function. Our data are consistent with KS-WNK1 targeting WNK4 and L-WNK1 to degradation.