Salt Transfer Research Articles

Circulation, Renewal, and Modification of Antarctic Mode and Intermediate Water*

Nine hydrographic sections are combined in an inverse box model of the Southern Ocean south of ;128S. The inverse model has two novel features: the inclusion of independent diapycnal flux unknowns for each property and the explicit inclusion of air‐sea fluxes (heat, freshwater, and momentum) and the water mass transformation they drive. Transformation of 34 3 106 m3 s21 of Antarctic Surface Water by air‐sea buoyancy fluxes, and cooling and freshening where Subantarctic Mode Water outcrops, renews cold, fresh Antarctic Intermediate Water of the southeast Pacific and southwest Atlantic. Relatively cold, fresh mode and intermediate water enter the subtropical gyres, are modified by air‐sea fluxes and interior mixing, and return poleward as warmer, saltier mode and intermediate water. While the zonally integrated meridional transport in these layers is small, the gross exchange is approximately 80 3 106 m3 s21. The air‐sea transformation of Antarctic surface water to intermediate water is compensated in the Southern Ocean by an interior diapycnal flux of 32 3 106 m3 s21 of intermediate water to upper deep water. The small property differences between slightly warmer, saltier intermediate water and cold, fresh Antarctic Surface Water results in a poleward transfer of heat and salt across the Polar Front zone. Mode and intermediate water are crucial participants in the North Atlantic Deep Water overturning and Indonesian Throughflow circulation cells. The North Atlantic Deep Water overturning is closed by cold, fresh intermediate water that is modified to warm, salty varieties by air‐sea fluxes and interior mixing in the Atlantic and southwest Indian Oceans. The Indonesian Throughflow is part of a circum-Australia circulation. In the Indian Ocean, surface water is converted to denser thermocline and mode water by air‐sea fluxes and interior mixing, excess mode water flows eastward south of Australia, and air‐sea fluxes convert mode water to thermocline water in the Pacific.

Weathering of marbles and granites in marine environment: petrophysical properties and special role of atmospheric salts

The aim of this paper was to study the weathering mechanism of marbles and granites exposed to the marine environment at the Delos archaeological site. Alterations, as granular disintegration, contour scaling and alveolus formations, can be observed either at the base of blocks and columns, or at the median-high zones of monuments. A white marble, which originated from Naxos Island, had a weak porosity (0.2%). Its porous network was organized into two subnetworks of rectilinear and sinuous cracks, which limited capillary transfer to ∼10 cm. The granite, which originated from Delos Island, had a relatively high porosity (2.15%), and had a well-connected system of cracks and microporous zones of weathered minerals. This homogeneous network allowed good capillary transfer for long distances (1–2 m). For the marble, as for the granite, evaporation occurred mainly at depth in the stone, and encouraged its deterioration. This damage depends on the dissolution and crystallization of salts, which occur in cycles. First, by the capillary transfer of water and salt from the ground, when the stones are located near the sea. This processes can explain the deterioration of the marble and the granite bases, and the decay of granite on all its surfaces. Second, by fixation of water vapor by sea salt deposited on the stone by wind. This phenomenon can explain the degradations observed on the median-high parts of monuments in marble and granite, even though, for the granite, the first mechanism was more active.

Experimental Studies of Brine Migration through Unsaturated Zone at an Oil Field

The problem of unsaturated zone pollution by highly mineralized field brines is considered. The results of experiments with field brines and tracer solutions were used to establish the migration mechanism of brines and tracer solutions at the first stages of their spreading with allowance made for the difference between their densities and chemical compositions. Salt transfer parameters are determined for the case of an ion not subject to sorption.

Enhancement of CsNO3 extraction in 1,2-dichloroethane by tris(2-aminoethyl)amine triamide derivatives via a dual-host strategy

A systematic study of a dual-host system exhibiting pairwise anion/cation separations has been performed for CsNO3 extraction. Tripodal triamides 1-4 and 9 derived from condensation of hexanoic (for 1), octanoic (for 2), decanoic (for 3), lauric (for 4), and p-tert-butylbenzoic (for 9) acid with tris(2-aminoethyl)amine (tren) were used together with tetrabenzo-24-crown-8, a well-known Cs+ cation receptor. By using 5 mM crown ether in the organic phase and 10 mM CsNO3 with 0.1 mM HNO3 in the aqueous phase, tripods 1, 2, and 9 enhance CsNO3 extraction by factors of 2.4, 1.7, and 4.4, respectively (for 50 mM amide concentration), while the corresponding monoamide controls 5-8 derived from n-propylamine (5, 6) or N,N'-dimethylethylenediamine (7, 8) and hexanoic (5, 7) or octanoic (6, 8) acid derivatives gave no significant enhancement under the same conditions. This behavior may be ascribed to nitrate complexation by the triamides, which lowers the overall thermodynamic barrier for the salt transfer to the organic phase. The nitrate binding was confirmed by 1H NMR titration of receptor solutions, using tetrabutylammonium nitrate. Association constants for the formation of the anion-nitrate complexes were found to vary between 33 and 52 M-1 for the more soluble triamides. The synergistic effects for CsNO3 extraction are in reasonable agreement with the values predicted theoretically from the measured association constants. Electrospray ionization mass spectrometry confirmed the predominant formation of 1:1 tripod-nitrate complexes. Monoamide controls gave no evidence of anion complexation.

Surface-Enhanced Raman Scattering of Charge Transfer Thin Films of Tetracyanoquinodimethane Derivatives on Metal Surface

The 488.0 and 1064 nm-excited Raman spectra have been measured for dipping films of 2-octadecyl-7,7,8,8-tetracyanoquinodimethane (octadecyl-TCNQ) and docosylpyridinum-TCNQ salt and mixed-stack charge transfer films of octadecyl-TCNQ doped with 3,3′,5,5′-tetramethylbenzidine (TMB) deposited on silver mirror. The 488 nm-excited Raman and 1064-nm excited FT-Raman spectra of dipping films of octadecyl-TCNQ and docosylpyridinum-TCNQ salt and CT film of octadecyl-TCNQ doped with TMB on the silver mirror gave very intense Raman bands with a high signal-to-noise ratio owing to the SERS effect. From the frequency of a C≡N stretching band of the CT film of octadecyl-TCNQ doped with TMB on silver mirror, the degree of CT can be calculated to be 0.42, suggesting that the CT film is in a quasi-neutral state. The C≡N stretching band of the dipping film of docosylpyridinium-TCNQ salt indicates the strong interaction of TCNQ group with silver mirror surface.

Border Irrigation Field Experiment. II: Salt Transport

This paper presents results from an experiment to measure the salt transport processes within a border-irrigated bay in northern Victoria, Australia, an area with shallow saline ground water and cracking soils. The overland flow and drainage salinity measurements showed that lateral surface washoff of salt from the soil surface was the main process of salt transport into surface water. Soil salinity measurements showed that, although salt was removed from the near-surface soil, there was negligible leaching downward through the profile. This was due to the near saturation of the soil, the presence of cracks that minimize the vertical leaching, as well as the lack of deep drainage of ground water. These findings highlight the importance of lateral washoff in the transfer of salt from irrigation bays, suggesting that reduction in irrigation event volumes is likely to reduce salt export and thus affect the sustainability of irrigation in this area.

EQCM studies of polypyrrole films. Part 2. Exposure to aqueous sodium tosylate solutions under thermodynamically non-permselective conditions

We describe electrochemical quartz crystal microbalance studies of polypyrrole films exposed to concentrated aqueous sodium tosylate solutions, in which the polymer is non-permselective in doped and undoped redox states at equilibrium. Then, sources and sinks of salt within the film open up new mechanistic possibilities for film redox switching that are not seen under thermodynamically permselective (low electrolyte concentration) conditions. In particular, sodium co-ion transfer (as opposed to tosylate counter-ion transfer in the opposite direction) is an expedient means to satisfy electroneutrality on short time scales for redox switching in either direction. Film mass responses under potentiodynamic (cyclic voltammetric) conditions depend markedly on experimental time scale (potential scan rates); these are generally non-monotonic as a result of, first, the competing mechanisms for maintaining electroneutrality and, second, slower neutral species transfers. Furthermore, shortening of the time scale can lead to a progressive freezing out of the solvent and salt transfer processes. The complex pattern of redox driven ion, solvent and salt transfer (involving both time scale and history effects) is visualized through an extension of the scheme-of-cubes model.

Kinetics and mechanism of biphasic transfer of salted water from an aqueous phase to AOT reverse micelles

The transfer of salted water from an external aqueous phase to AOT reverse micelles is studied in relation with the change of properties from a percolating to a non percolating state of the micelles. A membrane-separated two-compartment cell was used to measure the transfer of salt which was followed by conductivity measurements. We expected a sharp conductivity drop which could have been used as a kind of sensor to detect a threshold of salinity. In fact, this sharp drop was not observed and this is shown to be due to the fact that no excess water is incorporated in the microemulsion phase in these conditions. For this purpose separate analysis of the water and salt incorporated in the microemulsion phase versus time has been performed. Under the conditions used the increase of the salt content is accompanied by a decrease of the water content, even though the initial system was far from being saturated with water. The results are discussed in terms of the different possible mechanisms. Molecular diffusion of water appears to be unlikely and its expulsion can be simply explained by the shrinkage of the microdroplets merging with the interfacial film, this being associated with the electrostatic shielding of the polar head repulsions.

Methods for optimization of salt and moisture transfer

Analogs of the well-known methods for solving problems of optimization of salt and moisture transfer are constructed and justified. Bibliography: 4 titles.

Ion transport modelling through nanofiltration membranes

The aim of this work is to study the transport mechanism of ions through nanofiltration membranes. A model based on extended Nernst–Planck and film theory equations is reported. This model can be characterized by three transport parameters: the water permeability L p, the salt transmittance Φ and the effective salt transfer coefficient K eff. The knowledge of the feed and permeate concentration and of the permeate volumetric flux enable us to calculate these transport parameters. The model is used to estimate cadmium salts rejection by a NANOMAX 50 membrane. Experimental and calculated results are shown to be in good agreement. The model is then successfully extended to experimental data reported in the literature.

Transfer of salt and nutrients in Bruguiera gymnorrhiza leaves during development and senescence

The life span of leaves in Bruguiera gymnorrhiza, non-secretor of salt, can be divided into a leaf developing stage, a leaf functioning stage and a leaf senescing stage. The concentrations (mg/g) and the contents (mg/leaf) of Na and Cl increased at the leaf developing stage and remained almost constant at the leaf functioning stage. At the leaf senescing stage, the concentrations of Na and Cl increased markedly by 45 and 31% respectively, while their contents only increased by 16 and 4% respectively. The K/Na ratio remained constant at the leaf functioning stage, and decreased at the leaf senescing stage. During leaf senescence, there was a marked decline in leaf mass (20%) and in leaf area (15%). During senescence, 60% of its N, 48% of its P and 46% of its K was transferred out of the senescing leaf.

Deicing Salt Accumulation and Loss in Highway Snowbanks

AbstractEnvironmental impacts of road deicing salt are well known, although salt pathways following application have rarely been quantified. Deicing salt (NaCl) fate was determined from retention and loss in snow cover adjacent to a 14‐km section of highway in southern Ontario during the 1994–1995 winter. Total salt application was ∼530 Mg (29–74 kg m−1 length). Retention in snow cover in the highway right‐of‐way (ROW) decayed as a power function of distance from the highway, although melting of proximal snowbanks with high salt loads disrupted this pattern. Peak concentrations in snowbanks reached 6506 (Na+) and 9916 (Cl−) mg L−1. Wind transport of salt from the ROW was minor and restricted to relatively exposed sites. Almost all applied NaCl reached the soil surface via (i) direct runoff and infiltration of saline water from the road into the shoulder and ROW, and (ii) transfer of salt to snow cover adjacent to the highway and release during snowmelt. Total salt flux along the two pathways during a 49‐d period was similar. Salt transfer via road runoff occurred during or shortly after application, unlike the intermittent fluxes from snow to soil surfaces in the ROW during this period. The latter were relatively uniform along the highway (3–5 kg m−1 length of highway), accounting for 39 to 65% of applied NaCl. However, magnitude and timing of water and salt fluxes from snow to soil varied within the ROW and should be considered when modeling salt transport to groundwater.

Film mass and volume changes accompanying redox-driven solvent and salt transfer during redox switching of polyvinylferrocene films

We describe electrochemical quartz crystal microbalance (EQCM) measurements of salt and solvent transfers that accompany redox switching of poly(vinylferrocene) (PVF) films exposed to aqueous solutions of NaClO4. At low salt concentration (csalt ⩽ 0.1 mol dm−3), oxidized and reduced PVF films are both permselective. At high salt concentration, salt partitions into the film upon film oxidation; this effect is significant for csalt 1 mol dm−3. In order to explain salt partition quantitatively, we develop a new thermodynamic model that directly incorporates the variation of electroactive polymer film volume with film redox state and salt concentration. Application of the model to the PVF–NaClO4 system shows that oxidized PVF films shrink appreciably (typically 35%) under non-permselective conditions. The salt and solvent partition coefficients into oxidized PVF are Ksalt,Ox≈ 1.0 and Ksolv,Ox ≈ 0.15, respectively.

Specification of Eddy Transfer Coefficients in Coarse-Resolution Ocean Circulation Models*

Parametric representations of oceanic geostrophic eddy transfer of heat and salt are studied ranging from horizontal diffusion to the more physically based approaches of Green and Stone (GS) and Gent and McWilliams (GM). The authors argue for a representation that combines the best aspects of GS and GM: transfer coefficients that vary in space and time in a manner that depends on the large-scale density fields (GS) and adoption of a transformed Eulerian mean formalism (GM). Recommendations are based upon a two-dimensional (zonally or azimuthally averaged) model with parameterized horizontal and vertical fluxes that is compared to three-dimensional numerical calculations in which the eddy transfer is resolved. Three different scenarios are considered: 1) a convective ‘‘chimney’’ where the baroclinic zone is created by differential surface cooling; 2) spindown of a frontal zone due to baroclinic eddies; and 3) a wind-driven, baroclinically unstable channel. Guided by baroclinic instability theory and calibrated against eddy-resolving calculations, the authors recommend a form for the horizontal transfer coefficient given by 2 fM 2 2 k 5 a l 5 a l, N ˇRi where Ri 5 f2N2/M4 is the large-scale Richardson number and f is the Coriolis parameter; M2 and N2 are measures of the horizontal and vertical stratification of the large-scale flow, l measures the width of the baroclinic zone, and a is a constant of proportionality. In the very different scenarios studied here the authors find a to be a ‘‘universal’’ constant equal to 0.015, not dissimilar to that found by Green for geostrophic eddies in the atmosphere. The magnitude of the implied k, however, varies from 300 m2 s21 in the chimney to 2000 m2 s21 in the wind-driven channel.

Theory for solvent and salt transfer accompanying redox switching of electroactive polymers under permselective and non-permselective conditions. Part 1.—Complete redox switching

We present a thermodynamic treatment of ion and solvent transfer processes that accompany redox switching of an electroactive polymer under permselective and non-permselective conditions. A comprehensive model for solvent and salt transfer in polymers with different charge types is developed for the ‘end-to-end’ redox switching (complete oxidized/reduced interconversion) process. In this model during the redox reaction, an arbitrary number of electrons are involved in the interconversion of the two polymer redox forms, and solvent and salt are allowed to partition into the reduced and the oxidized forms of the polymer. We derive expressions for the concomitant mass changes, taking into account counter-ion, solvent and co-ion (salt) transfer. The results are given in terms of the partition coefficients of solvent and salt between the bathing solution and polymer in its reduced and oxidized states, and a quantity ΔR that describes the difference between co-ion exclusion properties of the polymer in its two different oxidation states. We discuss and illustrate the behaviour of ΔR as a function of electrolyte concentration for systems with different charge type.

Topographic Hadley cells

When a rotating fluid over sloping topography is heated from below and/or cooled from above, horizontal temperature gradients develop which drive convection cells aligned with isobaths. We refer to these cells as topographic Hadley cells. Laboratory experiments reveal that sinking occurs in small cyclonic vortices situated in relatively shallow regions. This is balanced by slower upwelling in adjacent deeper regions. The cross-isobath motions which connect the upwelling and downwelling are accelerated by Coriolis forces, resulting in strong jets which follow isobathic contours. For anticlockwise rotation, the surface jets keep the shallows to their left when looking in the direction of flow, which is opposite to both Kelvin and Rossby wave propagation. The width of the jets scales with the Rossby deformation radius and if this is much less than the width of the slope region then a number of parallel jets form. Motions on the deeper side of the jets where the flow is accelerating are adequately described by linear inviscid theory. However, the strong shears generated by this acceleration lead to baroclinic instability. The resulting cross-stream momentum fluxes broaden and flatten the velocity profile, allowing the flow on the shallow side of the jet to decelerate smoothly before sinking. Topographic Hadley cells are dynamically similar to terrestrial atmospheric Hadley cells and may also be relevant to the zonal jet motions observed on Jupiter and Saturn. It is also suggested that in coastal seas they may represent an important mode of heat (or salt) transfer where surface cooling (or evaporation) drives convection.

On mass diffusion effects in a Stefan-like problem arising in the melting of antarctic ice shelves

In this paper we analyse the effect of mass diffusion in a Stefan-like problem, referring to the interaction between ice shelves and seawater in Antarctica. This interaction is particularly important, being responsible for the vast majority of ice loss from Antarctica. We conclude that, in our specific case, the results obtained with the model which takes into account mass diffusion are almost indistinguishable from those obtained from the mass diffusion free model, and that therefore possible inversion layers are to be attributed to effects other than mass transfer of salt.

Experimental Study on the Recirculation of Homogeneous and Stratified Fluid Layers in the Advanced Solar Pond

The practical possibilities of constructing and operating a stable flow of homogeneous and stratified fluid layers in a solar pond were investigated in this study. A laboratory setup was prepared to carry out the experimental investigations. Transient and steady-state conditions were analyzed. A numerical model was developed to simulate heat, salt, and momentum transfer in the water body. The model was calibrated with the experimental data. Density and temperature measurements along the laboratory setup showed the configuration to be stable in all of the conditions which were analyzed. These experimental results indicated that through a proper multiselective injection and withdrawal procedure it was possible to create and control the double-diffusion stratified fluid layers, which characterizes the advanced solar pond.

Effect of electrolyte concentration and redox centre oxidation state on the layer mass of osmium-containing poly(4-vinylpyridine) films

A quantitative analysis of the mass changes observed when an [Os(bipy)2(PVP)10Cl]Cl polymer is exposed to perchloric acid electrolytes of different concentrations is reported, together with the mass changes observed as a result of redox switching of the OsII/III redox couple. The rigidity of the polymer under the conditions used is confirmed using admittance spectroscopy. The results obtained are discussed with reference to the structure of the polymer and the effect of osmotic pressure. The equilibrium mass changes observed show that ion and solvent transfer are greatly electrolyte dependent. From the mass changes observed as a function of the HClO4 concentration, a pKa value of 2.5 has been estimated for the immobilised film. Within the concentration range 0.01–1.0 mol dm–3 HClO4, electroneutrality is maintained during redox switching by counter-ion movement, but at very low HClO4 concentrations (0.001 mol dm–3) the mass changes observed are indicative of a mixed transport of co-ions and counter-ions. At concentrations greater than 1.0 mol dm–3 permselectivity breaks down with transfer of salt occurring during oxidation.

High density of Ca(2+)-dependent K+ and Cl- channels on the luminal membrane of lacrimal acinar cells.

Tight-seal whole-cell recording and Ca2+ imaging were simultaneously performed on cell clusters or individual acinar cells of rat lacrimal glands during application of the secretagogue acetylcholine. Activation of Ca(2+)-dependent K+ and Cl- currents was selectively followed as a function of time by placing the cell potential near the equilibrium potential for Cl- or for K+ ion, respectively. Upon acetylcholine application to cell clusters, K(+)- and Cl(-)-selective currents displayed a distinctive initial rise ("hump"). At this time, there was only a small elevation of Ca2+ concentration, [Ca2+]i, that was restricted to the luminal end of acinar cells. A quantitative analysis of Ca2+ and current signals during the hump suggested that the luminal membrane contained high densities of K(+)- and Cl(-)-selective channels, roughly 10 times higher than those found in the basolateral domain. Distinct luminal and basolateral membrane domains were preserved in isolated cells, but with less contrasted densities than in cell clusters. The results suggest that Ca(2+)-dependent K+ channels are implicated not only in the transfer of salt from the blood compartment to the interior of acinar cells, as commonly accepted, but also in the electrolyte secretion from the cell interior to the acinar lumen.