Salt Mobilization Research Articles

Spatial patterns of soil salinity in the central Argentinean Dry Chaco

The Dry Chaco is a semi-arid ecoregion in South America that hosts one of the largest dry forests in the world, but expansion of dryland agriculture and cattle ranching led to gradual conversion of native vegetation to anthropogenic land cover. The potential impact of these newly established agricultural lands on the surrounding environment is of great concern. Local studies have shown that deforestation leads to changes in the soil-water balance, and can expedite groundwater rise and mobilization of water-soluble salts to the surface affecting plant growth and crop productivity. This study is a regional assessment of soil salinity and salinization processes in the central Argentinean Dry Chaco. It is based on extensive dataset of 492 surface and 142 subsurface samples taken along east-west transects across the Dry Chaco. Soil electrical conductivity (EC) was used as an indicator of salinity, and supplementary information on salt crusts was derived from Google Earth imagery. Subsurface salinity (i.e., measured at 100 cm depth) showed clear regional patterns in natural soil salinity that are related to the annual water budget and topography. Besides primary salinization due to arrested drainage and landscape stagnation, anthropogenic activities increased secondary salinization, especially in the agricultural areas with shallow groundwater tables and irrigated croplands. In addition, the study demonstrated that remotely-sensed vegetation indices such as the seasonal variation in the density of green vegetation are particularly suitable to monitor regional variation in soil salinity. Our results show that the extent of future dryland salinization in the Dry Chaco will mainly depend on whether areas prone to natural soil salinity are further protected from deforestation, and the magnitude and rate of groundwater rise after deforestation as conditioned by local climate and geomorphology. This better understanding of soil salinity patterns and how they are affected as a result of anthropogenic activities is important for the implementation of appropriate and effective measures to prevent severe salinization.

A more accurate definition of water characteristics in stone materials for an improved understanding and effective protection of cultural heritage from biodeterioration

The water associated with cultural heritage materials is the most important factor before initiation microbial colonization and subsequent biodeterioration processes to occur. Since moisture or water in such materials is the key to life, a more refined characterization of water is needed to advance the basic understanding of the fundamental mechanisms, especially for the accurate assessment of bio-susceptibility or bio-receptibility of different materials. Water can be categorized to free, gravitational, capillary, and hygroscopic to account for the physical states and sorption strength with the materials. Material porosity or water-holding capacity are fundamental criteria used in characterization of various types of materials on a common ground and basis, but pore connectivity has been largely ignored and must be addressed to establish the methods for assessment and also its relationship to bio-colonization and biodeterioration. When a threshold value of water in the relevant physical categories is available, microbial life can colonize and establish colonies as biofilms on materials surfaces to carry out the biochemical reactions leading to biodeterioration, from appearance of discoloration to physical damage of the materials. Microbial destruction of inorganic materials is mainly carried out by the biochemical reactions through carbon, nitrogen and sulfur cycles. Among material porosity characteristics, available water and microorganisms, mobility and movement of soluble salts under wet and dry cycles have significant impact on the durability of materials. Uptake of soluble salts and supersaturated salts in water into materials can result in crystallization and mineral formation under evaporation condition to initiate the internal stress and cracks, which eventually result in surface delamination and damage. From an architecture design point of view, it is clear that management of water is a basic and important strategy to prevent development of microbial issues in the long-term protection of cultural heritage.

Salt-driven fluid venting chimneys at the base of the Sigsbee Escarpment, northwestern Gulf of Mexico

We discovered a large field of cylindrically-shaped sediment chimneys at the seafloor along the flank of Farnella Canyon (water depth ∼2775 m) at the base of the Sigsbee Escarpment in the northwestern Gulf of Mexico. The chimneys are about 10 cm in diameter with 1 cm wide axial cavities; they rise about 0.5–1 m above the seafloor and continue down into the seabed. Their composition and fabric were characterized using X-ray diffraction, carbonate content, stable oxygen and carbon isotopes, and scanning electron microscopy and microanalysis. Seismic profiles and bathymetric data from the location were analyzed to seek links between the chimneys and seabed geological structures. Results indicate that the vented liquids were warm seawater with brine and there is no evidence of hydrocarbons. These chimneys are residual sediment-filled fluid-escape conduits formed in the seabed from hemipelagic sediments that were locally consolidated by the pressure of fluid moving upward through the seabed in adjacent conduits and bound together by iron oxide and amorphous silica precipitates, as well as authigenic dolomite. The chimneys were subsequently exposed at the seafloor when bottom currents eroded the surrounding seabed. Concentric and crosscut bands evident in chimney cross sections indicate venting occurred episodically (venting is not currently active). The chimney field is situated at the toe of the Jurassic salt massif that extends beneath much of the continental slope. Salt movement created a pressure gradient within the seabed, directing porewater flow toward the base of the slope where the chimneys occur; thus, venting most likely occurred during times of salt mobility and shortly thereafter.

Interplay between base‐salt relief, progradational sediment loading and salt tectonics in the Nordkapp Basin, Barents Sea – Part II

AbstractReprocessed, regional, 2D seismic reflection profiles, 3D seismic volumes and well data (exploration and shallow boreholes), combined with 2D structural restorations and 1D backstripping were used to study the post‐salt evolution of the Nordkapp Basin in Barents Sea. The post‐salt evolution took place above a pre‐salt basement and basin configuration affected by multiple rift events that influenced the depositional facies and thickness of Pennsylvanian‐lower Permian‐layered evaporite sequence. Initially, regional mid‐late Permian extension reactivated pre‐salt Carboniferous faults, caused minor normal faulting in the Permian strata and triggered slight salt mobilization towards structural highs. The main phase of salt mobilization occurred during earliest Triassic when thick and rapidly prograding sediments entered from the east into the Nordkapp Basin. In the early‐mid‐Triassic, the change in the direction of progradation and sediment entry‐points shifted to the NW led to rotation of the earlier‐formed mini‐basins and shift of dominant salt evacuation direction to the south. The prograding sediment influx direction, sediment transport velocity and thickness influenced the dynamics of the early to late passive diapirism, salt expulsion and depletion along the strike of the basin. The basin topography resulting from salt highs and mini‐basin lows strongly affected the Triassic progradational fairways and determined the distinct sediment routing patterns. Minor rejuvenation of the salt structures and rotation of the mini‐basins took place at the Triassic–Jurassic transition, due to far‐field stresses caused by the evolving Novaya Zemlya fold‐and‐thrust belt to the east. This rejuvenation influenced the sediment dispersal routings and caused formation of dwarf secondary mini‐basins. The second and main rejuvenation phase took place during likely early‐mid‐Eocene when propagated far‐field stresses from the transpressional Eurekan/Spitsbergen orogeny to the NW inverted pre‐salt normal faults, reactivated the structural highs and rejuvenated the salt structures. The studied processes and study outcomes can be applicable to other evaporite‐dominated basins worldwide.

Geology and Geochemistry of Noachian Bedrock and Alteration Events, Meridiani Planum, Mars: MER Opportunity Observations

AbstractWe have used Mars Exploration Rover Opportunity data to investigate the origin and alteration of lithic types along the western rim of Noachian‐aged Endeavour crater on Meridiani Planum. Two geologic units are identified along the rim: the Shoemaker and Matijevic formations. The Shoemaker formation consists of two types of polymict impact breccia: clast‐rich with coarser clasts in upper units; clast‐poor with smaller clasts in lower units. Comparisons with terrestrial craters show that the lower units represent more distal ejecta from at least two earlier impacts, and the upper units are proximal ejecta from Endeavour crater. Both are mixtures of target rocks of basaltic composition with subtle compositional variations caused by differences in post‐impact alteration. The Matijevic formation and lower Shoemaker units represent pre‐Endeavour geology, which we equate with the regional Noachian subdued cratered unit. An alteration style unique to these rocks is formation of smectite and Si‐ and Al‐rich vein‐like structures crosscutting outcrops. Post‐Endeavour alteration is dominated by sulfate formation. Rim‐crossing fracture zones include regions of alteration that produced Mg‐sulfates as a dominant phase, plausibly closely associated in time with the Endeavour impact. Calcium‐sulfate vein formation occurred over extended time, including before the Endeavour impact and after the Endeavour rim had been substantially degraded, likely after deposition of the Burns formation that surrounds and embays the rim. Differences in Mg, Ca and Cl concentrations on rock surfaces and interiors indicate that mobilization of salts by transient water has occurred recently and may be ongoing.

Response of Salts in Saline Soil Using Different Irrigation Scheduling in Semi-Arid Zone of Pakistan

The salinity of soil is a crucial challenge for growers irrigating in semi-arid zones. To accomplish salinity, growers require information about salt's basis and processes of the salt mobility through the root zone. Soil salinity can be managed by exceptional irrigating farming practices including irrigation scheduling to leach down salts through the root zone. This study aimed at examining the salts movement in saline soil in a semi-arid region in Sindh, Pakistan. This field experiment was conducted during the summer of 2017 on a salt-affected land by using three irrigation treatments of canal water including T1 (7 day irrigation interval), T2 (14 day irrigation interval) and T3 (21 days irrigation interval) under 10, 9 and 8 cm depths of irrigation water, respectively. The texture of soil was silty clay loam having an electrical conductivity (EC) ranging from 7.73 to 20.69 dS/m. However, the pH of the soil ranged from 7.89 to 8.04. The findings of a two-way analysis of variance were consistent with the statistical examination of EC and pH data day- wise (7, 14 and 21 days) and depths-wise (10, 9 and 8 cm). Average reductions in the EC and pH of the soil were observed at 7 days interval and 10cm depth at P<0.05. Overall, the findings exhibited that, compared to the 14 and 21 day intervals, a 7 day irrigation interval was more effective in terms of salt leaching from the soil profile.
 

Intermittent hydrologic perturbations control solute cycling and export in the Okavango Delta

We measured the concentrations of the total dissolved ions (TDI), dissolved silica, major cations and the δD and δ18O at sub-weekly intervals for one year in the Okavango River at the outlet of the Okavango Delta (Delta). Our objectives were to (1) document the temporal variations in the concentrations of solutes in the Okavango River, (2) determine the processes controlling the transfer of solutes to the river and (3) assess the temporal solute load and outflux from the Delta. We found that the TDI and major cation concentrations in the river were anomalously high during the rainy season and before the arrival of the annual flood pulse. The anomalous increases in the solute concentrations are due to dissolution and mobilization of precipitated salts stored in the floodplains and on hundreds of thousands of islands scattered across the Delta wetlands, as well as from ‘flushing’ of remnant evaporated flood water of higher salinity trapped in isolated wetland pools. Overland flow generated by local rains and flooding connect the river to the solute stores in the watershed. The temporally activated hydrologic flow pathways transfer solutes to the river that flushes them out of the Delta. The solute load in the river was higher during the rainy season and during pulse flooding, and mimicked the discharge hydrograph. We estimate that 17,838 Mg/y of dissolved solutes was flushed out of the Delta, with 67% removed during pulse flooding (6 months) and 30% during the rainy season (4 months). The transfer of solutes from the watershed to the river during pulse flooding and the rainy season, and solute export from the Delta is an important mechanism that keeps the Delta’s surface water resources fresh, which is critical for supporting a freshwater wetland ecosystem. Our results highlight the importance of intermittent activation of hydrologic flow pathways in controlling solute cycling in this and other arid watersheds.

Formulating and assessing best water and salt management practices: Lessons from non-saline and water-logged irrigated fields

To address the on-site and off-site salt load impact associated with non-saline and water-logged irrigated fields a well-considered strategy is required. This implies minimal salt mobilisation and additions through irrigation, no crop yield losses due to excessive salt in the root zone, and minimal irrigation-induced drainage and leaching. The aim was to formulate best water and salt management practices to achieve this strategy and conduct an extensive assessment on whether they are implemented before problems appear. Weekly and seasonal data (2-years) from 19 fields (28 measuring sites) were used. Crops included barley, wheat, groundnuts, maize and lucerne grown in a semi-arid climate. Dominant soils were sandy loam, loamy sand and sandy with lateral moving shallow groundwater tables (depth>1.2 m and electrical conductivity<250mSm−1), while electrical conductivity of primary water sources is < 100mSm−1. Good decisions included the use of centre pivot compared to flood irrigation, irrigation schedules that ensured soil matric potential for maximum crop transpiration and limited yield losses due to water logging and soil salinity. Poor decisions were incorrect sprinkler design and excessive pumping pressure and limited use of rainfall and capillary rise to irrigate less. Growing season rainfall-plus-irrigation were a mean 55% more than the quota (annual water allocated to farmers), and 35%, 39%, 60%, 106% and 67% more than a “conservative” estimate of barley, wheat, groundnuts, maize and lucerne transpiration, respectively. The magnitude of variation in this oversupply were similar than the mean values. Approximately all salts applied through irrigation were leached from the root zone, while minimal re-use of drainage water was made (only 3 fields). In terms of resource use efficiency and preventing environmental degradation the evidence is overwhelming for improved decisions at field level. However, given sufficient supply of water, continuation of the status quo, might be sustainable in the long term.

Assessment of the tectonic role of the Triassic evaporites in the North Toulon fold-thrust belt

The eastern Beausset Syncline and Toulon Belt, in the southern France, represents the easternmost remnant of the Pyrenean Apto-Albian Rift System and of the Pyrenean-Provençal orogen (Late Cretaceous-Eocene). Detailed structural and stratigraphic field mapping as well as the integration of published structural and stratigraphic data, are used to reconstruct the Jurassic to Late Cretaceous tectonic evolution of this area. A layered evaporite sequence, composed of a succession of evaporitic units interbedded with more competent lithologies, behaved as the main decoupling horizon and source of diapiric bodies. Structural and lithostratigraphic observations in the Mont Caumes area are interpreted as halokinetic in origin (wedges, flaps, welds, thrust welds, highly localized depocentes). These were controlled by the sinuous Mont Caumes salt wall that grew along the southern flank of the eastern Beausset Syncline and interacted with regional tectonic stresses from Early Jurassic to latest Santonian times. Jurassic and Lower Cretaceous carbonate units thin toward the Mont Caumes salt wall, recording deposition in salt controlled broad synclinal depocentres controlled by early salt mobilization. Inverted relics of Apto-Albian rift depocenters are aligned along the northern margin of the Toulon Belt and the adjacent Bandol Belt to the west. In the Turonian-Coniacian Revest depocenter, stratal thickness variations, progressive unconformities lateral depocentre, and the westward increase in stratal, overturning of a flap on the basin’s southern margin all record localized strong asymmetrical growth of the 3D Mont Caumes salt wall. During Pyrenean-Provençal N-S convergence starting in Early Campanian, the salt wall was squeezed and reactivated as a thrust weld. The upper part of the flap was sheared and thrust north over the Beausset Syncline (Mont Caumes imbricate). Further to the west, the Saint-Cyr salt extrusion associated with the Santonian-Muschelkalk unconformity, indicates that the Bandol salt wall extruded at the same time as the main diapiric activity of the Mont Caumes salt wall. Compressional reactivation further extruded the salt body leading to emplacement of the Beausset Klippe onto the Beausset Syncline. The Toulon salt structures can be correlated with other examples of contractional salt structures in the external Alps and Pyrenees.

3D mapping of intruding salt bodies in the subsurface of the Gulf of Mexico using 3D seismic data

Salt tectonics has important implications for hydrocarbon exploration in salt-bearing basins since salt deformation can directly or indirectly form hydrocarbon traps, influence hydrocarbon migration, and can control deepwater depositional systems. In various basins around the globe, extensive research has been conducted on initiation of salt mobilization, subsequent deformation, and eventual cessation, typically from subsurface two-dimensional (2D) sections. However, 3D seismic data has dominated the petroleum industry for the last 30 years. Despite the plethora of 3D seismic data acquired in salt-bearing basins, there has been hardly any published work displaying the 3D geometries of complex salt bodies. 3D salt mapping in the subsurface can reveal true distribution of salt bodies and their detailed intricacies of geometrical variations, aiding in the overall salt system interpretation. Using a large 3D seismic survey (3,350 km2), this study presents the first 3D salt mapping in the Gulf of Mexico, demonstrating how 3D visualization of the entire Louann Salt system within the Middle Jurassic to present-day stratigraphy can improve interpretation of salt feeder geometries, allochthonous salt canopies, initial salt distribution, and salt weld locations in the study area.

Salt tectonics in salt-bearing rift basins: Progradational loading vs extension

Confined salt flow in narrow (<100 km) and deep (ca. 10 km) rift basins with an initially thick (>3 km) layer of evaporites, results in a complex structural style consisting of vertical and closely-spaced diapirs surrounded by thick (6–10 km) and narrow minibasins with intricate internal patterns recording salt withdrawal. These basins are usually explained as the result of thick-skinned extension, while other important factors such as sediment loading and subsalt basin configuration are not commonly addressed. We use sandbox models, 3D reconstruction of the models’ final stage, and structural restoration to evaluate the impact of sediment loading, thick-skinned extension, and different basin configurations on the suprasalt structural style and the spatial and temporal distribution of salt structures in these basins. Models simulating sediment loading display expulsion rollovers and younger salt structures in the progradation direction. In contrast, thick-skinned extension models display stacked depocenters near basin-boundary faults and opposite timing of diapir growth. Along strike changes in basin configuration and subsalt faults impact salt flow and salt structures as follows: (1) Faults perpendicularly facing the sediment progradation contribute to the formation of salt diapirs, (2) Oblique faults favour salt flow along strike, (3) Fault intersections cause salt inflation and salt diapirs, and (4) Basin confinement by graben narrowing or intrabasinal faults produces along-strike differences in the timing of salt mobilization. The sandbox models show close resemblance and are directly comparable to seismic sections through the Nordkapp Basin (Norwegian Barents Sea) and other salt-bearing rift basins with similar configuration.

Morphology of the basement and Hormuz salt distribution in offshore Abu Dhabi from constrained 3-D inversion of gravity and magnetic data

Many seismic surveys and exploration wells have been conducted in offshore Abu Dhabi, United Arab Emirates. However, the Neoproterozoic basement and the Infracambrian Hormuz salts were not imaged or penetrated by seismic and well data. To delineate the morphology of the basement and distribution of salt bodies, we applied a 3-D constrained inversion method to aerogravity and aeromagnetic data covering offshore Abu Dhabi. Well and seismic data were used to constrain and validate the inversion results. The magnetic inversion model resulted in a robust basement model that varies in depth from 8 to 10 km with two highs at 8 and 8.5 km highlighting possibly magmatic bodies. In contrast, the gravity inversion model does not delineate very well the basement morphology, possibly due to the lower density salt bodies masking the gravity response of the higher density basement. By calculating and removing the gravity response of the magnetic basement model from the observed gravity data, we recovered the residual gravity response of the Hormuz salts. The 3-D gravity inversion of the residual shows that the Hormuz salts are more wide-spread and thicker than previously thought with a depth to top of salt varying from 5.5 to 8.5 km. This salt model suggests that the giant oilfields in offshore Abu Dhabi, such as Umm Shaif, Nasr, Abu Al-Bukhoosh, Zakum, Sarb and Hail, occur exactly above crests of salt pillows. In addition, a series of smaller oilfields are found located at the margin of the northern basement high, and three structural lineament trends (NE-SW, NW-SE, and N-S) were identified from the inverted basement and salt models. Reactivation of these fault trends and associated diapiric salt uplifts, as observed in the seismic sections and curvature map, played a major role in shaping the basement morphology and mobilization of the Hormuz salts.

Characterization of four unknown impurities in azithromycin and erythromycin imino ether using two-dimensional liquid chromatography coupled to high-resolution quadrupole time-of-flight mass spectrometry and nuclear magnetic resonance.

A simple and sensitive method was developed for the separation and characterization of four unknown impurities in azithromycin and erythromycin imino ether using two-dimensional liquid chromatography coupled to high-resolution quadrupole time-of-flight mass spectrometry (2D LC/QTOFMS) with positive and negative electrospray ionization. The chromatographic separation in the first dimension was performed with a Waters Xbridge RP18 column in gradient mode using binary mobile phase: (A) phosphate buffer (pH 8.2)-acetonitrile (47:53, v/v) and (B) water-acetonitrile (90:10, v/v). In the second dimension, the chromatographic separation was performed using a Shimadzu Shim-pack GISS C18 column with volatile mobile phases: (A) ammonium formate solution (10 mM) and (B) methanol. The molecular formulae and structures of the four impurities were deduced based on the LC/MS/MS data, and further confirmed using 1 H NMR, 13 C NMR, 1 H-1 H COSY, HSQC and HMBC NMR spectra after semi-preparative isolation of impurities. In addition, the mechanism for the formation of the impurities was also proposed. The contradiction between the non-volatile salt mobile phase and mass spectrometry was solved by means of a multiple heart-cutting 2D LC approach and on-line desalination technology. Four impurities were separated and characterized. These results could further improve the method of official monographs in pharmacopoeias and guides to improve the process of reducing impurity content.

Separation and characterization of unknown impurities in rutin tablets using trap-free two-dimensional liquid chromatography coupled with ion trap/time-of-flight mass spectrometry.

A new high-performance liquid chromatography method was developed for the determination of impurities in rutin tablets to improve on the method of the official monograph in national drug standards. Five impurities in rutin tablets were characterized using trap-free two-dimensional liquid chromatography coupled with ion trap/time-of-flight mass spectrometry (2D-LC/IT-TOFMS) in both positive and negative ion modes of electrospray ionization. In the first dimension, the LC column was a Thermo Acclaim 120™ C18 (4.6 mm × 250 mm, 5 μm), and the mobile phase was composed of 0.1 M sodium dihydrogen phosphate aqueous solution (pH adjusted to 4.4 with phosphoric acid) and acetonitrile (80:20, v/v). In the second dimension, the column was a Shimadzu Shim-pack GISS C18 (50 mm × 2.1 mm, 1.9 μm), and the mobile phase was composed of 10 mM ammonium formate solution and methanol. The structures of five impurities in rutin tablets were deduced based on the MS n data in both positive and negative ion modes, in which two impurities were unknown. Impurity 1, impurity 2 and impurity 3 were proposed as flavonol 3,7-di-O-glycoside, flavonol mono-O-triglycoside and quercetin 3-O-glycoside, respectively, and impurity 4 and impurity 5 were proposed as kaempferol 3-O-rhamnosylglucoside and isorhamnetin 3-O-rhamnosylglucoside, respectively. The method established in this study was simple and reliable for the routine quality control of rutin tablets. The contradiction between non-volatile salt mobile phase and mass spectrometry was solved by means of a multiple heart-cutting 2D-LC approach and on-line desalination technology. Five impurities were separated and characterized. These results provide a scientific basis for further improving the national drug standard of rutin tablets.

The influence of halokinesis on prograding clinoforms: Insights from the Tiddlybanken Basin, Norwegian Barents Sea

AbstractAlthough the trajectory and geometry of clinoforms in different types of basins have been described in many studies, few studies discuss the influence of halokinesis on clinoforms in salt‐related basins. In this study, we analyse the Lower Cretaceous clinoforms in the Tiddlybanken Basin, Norwegian Barents Sea to evaluate the impact of salt mobilization on the geometry and trajectory of clinoforms as well as its implications on sediment partitioning. To accomplish this objective, we use a multidisciplinary approach consisting of seismic and well‐interpretation, 3D structural restoration, and forward stratigraphic modelling. The results show that salt mobilization affects prograding clinoforms by: (a) causing lateral variations in progradation rates, resulting in complex palaeogeography, (b) increasing slope angles, which affect the equilibrium of the clinoform profile and can trigger slope‐readjustment processes and (c) producing lateral and temporal variations in accommodation space, leading to different clinoform trajectories, stacking patterns and reservoir distribution along the basin. Forward stratigraphic modelling shows that in salt‐related basins and other tectonically active basins, the isolated use of conventional methods for clinoform analysis might lead to potential interpretation pitfalls such as misinterpretation of trajectories and overestimation of foreset angles, which can have negative consequences for exploration models.

Biodrainage- an Eco-Friendly Solution for Waterlogged Areas

Of late, drainage problems and salinity development in various irrigation project areas are felt and they draw the attention in the recent past. Drainage is highly necessary on flat wetlands, which is characterized by very gentle slope (less than 2%) and water stagnation. The excessive seepage, wasteful use of water - over irrigating crops, lack of drainage have led into water logging and this is a matter of concern in all our major command areas. Water logging and rise of water table lead to mobility of soluble salts from deeper layers to soil surface. There by resulting in salinization initially and then into sodicity. The conventional means of drainage involves construction of drainage channels, lining of channels, removing the water through pipes and establishing controlling and regulatory structures which require a huge investment and time for implementation of the work. The best alternative to conventional means of drainage is Bio Drainage.

A pectin-gelatin gel containing oral rehydration solution and the release of sodium chloride under simulated gastric conditions

Both gelatin and pectin have the ability to trap salt and facilitate its release under simulated gastric conditions. The objective of this study was to develop a pectin-gelatin gel fortified with oral rehydration solution/s (ORS) that can maintain a more rigid structure to limit salt mobility (potentially less salty taste), yet allow rapid release in simulated gastric conditions. Two gels containing both pectin and gelatin were developed: (1) low salt (LS) containing 2.6 g/L salt and 13.5 g/L sugar and (2) high salt (HS) containing 5.2 g/L salt and 27.0 g/L sugar. The ORS-fortified gels were compared with commercially available gelatin gels and a control pectin-gelatin gel without added salt or sugar. A stronger gel network (higher G′) and higher viscosity was noted for HS compared to other samples. HS had slower salt release (80.70 ± 1.92%) than LS (95.95 ± 3.82%) at 1 min in simulated gastric conditions. After 120 min, HS showed up to 99.38 ± 1.08% release of salt, while LS had 95.95 ± 3.82% release. HS had a favorable textural profile, having values more similar to the ready-to-eat commercial cup gel than did the LS formulation. The HS formulation resulted in a stable structure for ORS delivery and beneficial release properties.

Analytical Models for 3-D Diffusion of Ions from Salt-Contaminated Aggregates

Abstract This article presents an analytical investigation of the mobility of salts from contaminated aggregates in concrete. Salt-contaminated aggregates may have varied effects on the mechanical properties and durability of concrete. These depend primarily on the mobility of salts within the concrete matrix. Existing diffusion-based models for the mobility of salts in concrete focus on their intrusion from external sources (e.g., chloride penetration from deicing salts and brines). Such problems are well described by the closed-form solution of Fick’s law for diffusion in one dimension from a continuous source. Salt-contaminated aggregates represent a case of diffusion from a finite internal source rather than intrusion from a continuous external source. When the source is internal—as in the case of salt-contaminated aggregates—diffusion occurs in three dimensions and the source is finite. The 1-D solution is ill conditioned to model this problem, so new diffusion models must be introduced. This article presents two models of varying complexity that are well conditioned to model diffusion of salts from contaminated aggregates. First, the problem is modeled using Fick’s law for the simplified case of 3-D diffusion from an instantaneous point source in an infinite medium. Contaminated aggregates are treated as infinitesimal slugs of diffusing material. The same problem is then modeled using Fick’s law for the more realistic case of 3-D diffusion from an instantaneous spherical source, where contaminated aggregates are treated as approximately spherical. The intent of this article is to present an academic discussion on how chloride ions might migrate within the concrete matrix if they are assumed to do so by diffusion alone.

DelPhiPKa: Including salt in the calculations and enabling polar residues to titrate.

DelPhiPKa is a widely used and unique approach to compute pKa 's of ionizable groups that does not require molecular surface to be defined. Instead, it uses smooth Gaussian-based dielectric function to treat computational space via Poisson-Boltzmann equation (PBE). Here, we report an expansion of DelPhiPKa functionality to enable inclusion of salt in the modeling protocol. The method considers the salt mobile ions in solvent phase without defining solute-solvent boundary. Instead, the ions are penalized to enter solute interior via a desolvation penalty term in the Boltzmann factor in the framework of PBE. Hence, the concentration of ions near the protein is balanced by the desolvation penalty and electrostatic interactions. The study reveals that correlation between experimental and calculated pKa 's is improved significantly by taking into consideration the presence of salt. Furthermore, it is demonstrated that DelphiPKa reproduces the salt sensitivity of experimentally measured pKa 's. Another new development of DelPhiPKa allows for computing the pKa 's of polar residues such as cysteine, serine, threonine and tyrosine. With this regard, DelPhiPKa is benchmarked against experimentally measured cysteine and tyrosine pKa 's and for cysteine it is shown to outperform other existing methods (DelPhiPKa RMSD of 1.73 vs RMSD between 2.40 and 4.72 obtained by other existing pKa prediction methods).

Development of a novel HPLC method for the determination of the impurities in desonide cream and characterization of its impurities by 2D LC-IT-TOF MS

A novel HPLC method for the determination of the impurities in desonide cream was established and validated for the further improvement of the official monograph in USP. Desonide was well resolved from the photodegradation impurity, which overlapped with desonide in USP method. The method was validated in accordance to the regulatory guidelines recommended by the International Conference on Harmonisation and this validation included specificity, limit of detection, limit of quantification, linearity and accuracy. Four degradation impurities in desonide cream were characterized by a trap-free two-dimensional liquid chromatography coupled to high resolution ion trap/time-of-flight mass spectrometry (2D LC-IT-TOF MS) in positive mode of electrospray ionization. Through the multiple heart-cutting 2D LC approach and online demineralization technique, the problem of incompatibility between non-volatile salt mobile phase and mass spectrometry was solved completely, and the TIC chromatogram of LC–MS could be in conformity with the LC chromatogram of the official analytical method in the peak sequence of impurities. In the first dimension, the column was Phenomenex Kinetex C8 (4.6 mm × 150 mm, 2.6 μm) with a non-volatile salt mobile phase. In the second dimension, the column was Shimadzu Shim-pack GISS C18 (50 mm × 2.1 mm, 1.9 μm) with a volatile salt mobile phase. The structures of four degradation impurities in desonide cream were deduced based on the HPLC-MSn data. The established method in this study was simple and reliable for routine quality control of desonide cream.