Function Of Salinity Research Articles

Predicting amphipods' brood size variation in brackish environments: an empirical model for Corophium multisetosum Stock, 1952 (Corophiidae) in Ria de Aveiro (NW Portugal).

Data on fecundity of Corophium multisetosum from Areão (Ria de Aveiro, Portugal) are analysed by non linear regression to quantify the relationship between brood size (N(e)) and head length (L(h), in mm), water temperature (T, in degrees Celsius) and salinity (S, in psu). The aim of the analysis is to obtain a simple line N(e)=a+bL(h), in which the slope (b) and the y intercept (a) are functions of salinity and/or temperature on each sampling occasion. The equation N(e)=(-2.940-8.027S)+(-89.431+18.171S+12.904T-0.368T(2))L(h) explains 64% of the variability of brood size throughout the breeding period. The model predicts an optimal temperature around 18 degrees C and a very low fecundity at low salinities. The graphical comparison of the lines obtained by the model and by a usual linear regression illustrates its potential usefulness to predict fecundity changes. The authors suggest that the observed variation in the fecundity of other brackish-water amphipods can be described and predicted using similar models.

Marine barite and celestite saturation in seawater

The stoichiometric solubility product , K sp,T *, of barite and celestite in seawater has been calculated using thermodynamic constants, K s0 , and the activity coefficients for barium, strontium , and sulfate in seawater. An equation of the form: ln K sp,T *=A+B ln T+ C T +DS n has been used. The constants A , B , C , D and n are derived from the calculated stoichiometric (or total) solubility product of barite and celestite in seawater as a function of temperature and salinity. T is the absolute temperature (K) and S is the salinity. The effect of pressure on K sp,T * is also calculated. Comparing the solubility products determined from this equation and the pressure effect equation to the distribution of Ba, Sr and SO 4 in seawater, we conclude that the upper surface water of the Southern Ocean is likely supersaturated with respect to pure barite, in agreement with Jeandel et al. [Jeandel, C., Dupre, B., Lebaron, G., Monnin, C., Minster, J.F., 1996. Longitudinal distributions of dissolved barium, silica and alkalinity in the western and southern Indian Ocean. Deep-Sea Res. 43, 1–31.] and Monnin et al. [Monnin, C., Jeandel, C., Cattaldo, T., Dehairs, F., 1999. The marine barite saturation state of the world oceans. Mar. Chem. 65, 253–261.] and that the oceanic water column is typically <30% saturated with respect to celestite. The model, which includes the thermodynamic solid–solution behavior of barite in seawater at 25°C and 1 atm, suggests that this mineral may contain up to 13 mol% SrSO 4 at equilibrium. Accordingly, we have determined the stoichiometric solubility products of strontian barite as a function of salinity and temperature: ln Ba K sp ′=247.88−38.333 ln T− 15421 T +1.27S 0.3 Using our model results for the total solubility product of the Sr-barite phase and seawater Ba and SO 4 concentration data, we conclude that the maximum saturation level of the oceans with respect to marine barite is 63% in the North Atlantic, 88% in the Indian Ocean, and 111% in the North Pacific. The depth of this maximum saturation level is shallower in the Atlantic Ocean (about 1000 m) than in the Pacific and Indian oceans (about 2000 m).

Control of Phosphate Concentration through Adsorption and Desorption Processes in Groundwater and Seawater Mixing at Sandy Beaches in Tokyo Bay, Japan

Field observation was conducted to monitor phosphate concentrations in groundwater and seawater mixing at two sandy beaches in Futtsu and Miura in Tokyo Bay, Japan. Dissolved phosphate concentrations were measured along transects from fresh groundwater aquifer to seawater adjacent the beaches. The concentrations were often high (up to 46 µM) in fresh groundwater samples (Cl− < 0.2‰). Coastal seawater, on the other hand, exhibited low phosphate concentrations (1.5 µM or less). Along the transects, phosphate generally displayed non-conservative behavior during mixing of fresh and saline waters in the aquifer; concentrations as high as 100 µM were found around the upper limit of seawater intrusion (Cl− = ∼2‰). Laboratory experiments were executed to identify the processes that control the phosphate behavior in the mixing processes. The results revealed that adsorption-desorption processes by the aquifer sand particles could significantly control the phosphate concentrations in the groundwater. Furthermore, the adsorption and/or desorption was found to be a function of salinity; the equilibrium concentration of dissolved phosphate in slurry of sand and water was the highest in freshwater and decreased considerably in saline water. The extreme concentration of phosphate may be caused by release from sand particles coinciding with the rapid change in salinity with tide.

The behaviour of di-(2-ethylhexyl) phthalate in estuaries

Because of their extensive use as non-reactive plasticisers, phthalate esters have become widespread contaminants of the aquatic environment. There is, however, little accurate information on the solubility and sorptive behaviour of phthalates in estuaries, where contaminants generally occur at elevated concentrations and are under the influence of a number of reaction-controlling variables. In this work we have investigated the relative solubility and particle–water interactions of di-(2-ethylhexyl) phthalate (DEHP), one of the most important and abundant phthalate esters, under simulated estuarine conditions using water and sediment samples from a small, organic-rich estuary (Beaulieu, southern England). Dissolved DEHP was salted out in sea water from distilled water, and a salting constant of about 1.2 l mol−1 was derived. Although the compound apparently interacts with dissolved organic matter in river water, it showed no evidence of enhanced solubility over the range in DEHP concentrations studied. Adsorption onto estuarine particles was defined by the Freundlich equation, and was significantly greater in sea water than river water suggesting that the particulate organic matter is subject to either salting out or salinity-induced structural modification which improves its solvency for DEHP. Distribution coefficients (KDs) exhibited a strong inverse relationship with particle concentration (SPM), an effect defined by the equations: KD=2.63×106SPM−1.15 and KD=2.64×106SPM−0.75; in river water and sea water, respectively, and only partly accounted for by experimental artefacts (e.g., adsorption of DEHP to container walls). That the gradient of the relationship was greater in river water than in sea water suggests the effect is caused, to some extent, by a particle–particle interaction mechanism (e.g., flocculation) which is inhibited at high salinities. A comparison of the results of this study with a compilation of data on DEHP distributions and partitioning in aquatic environments suggests that the estuarine behaviour of DEHP is a function of salinity, particle concentration, particulate organic carbon, and its degradation rate in the aqueous phase. A model for predicting the retention of DEHP in estuaries, incorporating these effects, is presented, and calculations indicate that, under certain hydrodynamic and chemical conditions, more than 50% DEHP discharged to a catchment may be retained by estuarine sediment, at least over a timescale equivalent to the estuarine particle residence time.

Estimation of evaporation from the Dead Sea

A project to link the Dead Sea to the Red Sea via a canal is undergoing extensive study. As part of this study, a method to estimate evaporation from the Dead Sea is required as it is a hypersaline lake in which standard methods cannot be applied. Two methods based on Penman and Dalton formulae were examined. The method derived here is a modified Penman model that estimates the evaporation as a function of salinity, humidity, air temperature and wind speed. Other parameters such as water temperature are included implicitly in the model. The results obtained were verified as satisfactory agreement was achieved by comparison with previous measurements. A short-cut relationship to estimate evaporation as a function of salinity only was also derived. Copyright © 1999 John Wiley & Sons, Ltd.

234Th and 7Be as tracers for the transport and dynamics of suspended particles in a partially mixed estuary

The sources of the natural radionuclides 234Th (half-life = 24 d) and 7Be (half-life = 53 d) to the partially mixed Hudson River estuary are distinctly different: 234Th is produced from decay of dissolved 238U that varies conservatively as a function of salinity, and 7Be is added directly from the atmosphere. 234Th and 7Be activities were measured in suspended and bottom sediments under varying conditions of river flow to evaluate the relative importance of local sediment resuspension and advection of suspended sediments through the estuary. Both radionuclides are removed from the estuarine water column on time scales of from <1 to 13 d. The 234Thxs/7Be activity ratio is used to eliminate variations in the specific activities caused by grain size or sediment compositional changes. A simple steady-state model is used to set limits on the activity ratios expected if local processes (in situ production of 234Th, atmospheric supply of 7Be, scavenging, particle settling, and resuspension) dominate the activity ratio. During low river discharge, observed 234Thxs/7Be ratios exceed the model upper limits in the higher salinity portions of the estuary, suggesting that particles labeled with Th and Be in higher salinities are transported to lower salinities with the estuarine circulation. Distance scales of particle transport are estimated to be from 10 to 20 km, comparable to the tidal excursion. Sampling during a high-flow event of short duration shows that the activity ratios tend toward the lower limit. Such a pattern could be produced by down-river transport of particles or by enhanced resuspension. Similarities between the 234Thxs/7Be activity ratios of suspended and bottom sediments suggest that increases in resuspension during high flow events dominate the activity ratio in the suspended sediment reservoir.

A novel approach for estimating ecosystem production and respiration in estuaries: Application to the oligohaline and mesohaline Hudson River

Most estimates of metabolism in estuaries are based on water samples incubated in bottles. Such approaches may severely underestimate rates of both gross primary production (GPP) and respiration for a variety of reasons, including reduced turbulence, unnatural light fields, respiration of 14C‐labeled organic matter, and altered grazer communities. These problems may be particularly intense in turbid and deeply mixed estuaries. The measurement of metabolism from in situ changes in dissolved oxygen (DO) concentration over a diel time period offers a potential solution to these problems, but complicated patterns of water advection and mixing in estuaries have limited the use of such open‐water approaches. Here, we describe a method of using diel changes in oxygen concentrations in the oligohaline and mesohaline Hudson River estuary to estimate GPP, whole‐ecosystem respiration (ER), and net ecosystem production (NEP). For this approach, concentrations of DO at any given time for several stations are described as a function of salinity and depth, providing a surface in the three‐dimensional space of oxygen, depth, and salinity. The change in this “response surface” for oxygen over time, once corrected for atmospheric exchange, allows the estimation of metabolism rates. The regression procedures used allow an estimate of the standard error associated with the metabolism measures. For the mesohaline Hudson River estuary, these standard errors are reasonably small. Similarly, any potential errors associated with the estimation of atmospheric exchange in oxygen are small for the Hudson. The technique should be useful for estimating GPP, NEP, and ER in other partially mixed estuaries without the biases associated with incubations in bottles.

Phase Behavior and Salt Partitioning in Two- and Three-Phase Anionic Surfactant Microemulsion Systems: Part I, Phase Behavior as a Function of Temperature

Microemulsion phase behavior was studied as a function of salinity and temperature. The objectives were to investigate the influence of different electrolytes on optimal salinity and solubilization, and to relate the efficiency of each cation to change in microemulsion phase behavior. Two five-component microemulsion systems using anionic surfactants were studied as a function of type of cations (Na, K, Mg, Ca) and ionic strength. The phase behavior studies were performed at three different temperatures in the region [20°C, 90°C], and at different surfactant concentrations. The optimal salinity, defined as equal water and oil solubilization in the microemulsion phase, was used to quantify changes in phase behavior. Consistently, the divalent ions reached optimal salinity at lower salt concentrations than did monovalent ions. The effect of the different electrolytes on phase behavior was quantified by introducing an efficiency parameter. Knowledge of the efficiency relation between different cations in a microemulsion system provided a tool for predicting optimal salinity for salt mixtures. The microemulsion phase behavior was more sensitive to temperature in monovalent electrolyte solutions compared to divalent ions. At lower surfactant concentration the divalent cations had an even stronger influence on phase behavior compared to monovalent cation electrolytes.

Complex controls on the trace-element chemistry of non-marine ostracods: an example from Lake Pátzcuaro, central Mexico

The calcitic shells of non-marine ostracods are sources of geochemical information that have the potential to record changes in the water chemistry of closed-basin lakes resulting from variations in the hydrological budget within the catchment. In particular the uptake of Sr and Mg into the shell has been shown to be a function of salinity, and salinity and temperature, respectively. This paper assesses the trace-element chemistry records from 4 short (1.5–2.8 m) cores from Lake Pátzcuaro, central Mexico, in the light of a detailed limnological study of the lake. The following three environmental factors are believed to have influenced the interpretation of the trace-element chemistry record: (i) salinity: the salinity of Lake Pátzcuaro lies close to the calcite branchpoint, below which the linear relationship between Mg/Ca or Sr/Ca and salinity has been lost in the fossil record; (ii) environmental stresses: e.g. low HCO 3 − concentrations, produced poorly calcified valves. This study found this had no significant effect on the trace-element chemistry results; and (iii) solute composition of the host water: changes in the solute concentration of inwash waters played a primary role in determining major water chemistry changes within the lake.

Diagnosis of Chemical Reactivity and Pollution Sources from Particulate Trace Metal Distributions in Estuaries

A simple approach is outlined for the diagnosis of chemical reactivity and pollution sources from distributions of suspended particulate constituents in estuaries of low turbidity and limited bed-water column particle exchange. The approach is demonstrated using acetic acid-extractable particulate trace metal data for the Clyde Estuary, where water and particle mixing in the vertical is restricted by a strong pycnocline, resuspension is limited by slow subsurface currents and internal sediment cycling is inhibited by the topography of the outer estuary. The salinity distributions of particulate Fe and Mn result from end-member particle mixing, modified by the geochemical mechanisms controlling their particle–water exchange (salt-induced flocculation of riverine, Fe-bearing colloidal material and autocatalytic oxidation-sorption of dissolved Mn). The axial distributions of particulate Cu, Cr, Pb and Zn are, additionally, affected by external inputs to the tidal estuary. The magnitudes of internal (e.g. particle–water exchange) or external (e.g. pollution) sources are calculated from the deviation of metal concentrations from a theoretical dilution line adjoining estuarine end-members, via chemical mass balances and empirical equations defining particle–water partitioning as a function of salinity. Calculated particle–water exchanges of Fe and Mn are compatible with independent dissolved metal measurements in the Clyde Estuary. Calculated external sources of Cu and Pb are in reasonable agreement with monitored trace metal input data to the estuary, but discrepancies exist between calculated and monitored external sources of Cr and Zn because of the significance of unmonitored inputs and chemical reactivity for these metals.Although suspended particulate trace metal concentrations in the Clyde are among the highest of industrialized estuaries in the U.K., it is argued that this, in part, reflects the inability of the Clyde to buffer pollution inputs because of the restricted internal cycling and bed-suspension exchange of particles in the system. A more general implication is that the mobility of the sediment reservoir and standing stock of suspended particles, in addition to concentration of particulate constituents (w/w), should be accounted for in any estuarine pollution impact evaluation.

The temperature dependence of pH in surface seawater

The temperature dependence of pH in surface seawater was investigated as a function of salinity and CO 2 composition using the most recent values for the equilibrium constants of the CO 2 system in seawater. A substantial discrepancy was found in one of the previously published algorithms used to correct shipboard pH measurements made at 25°C to the in situ temperature. Over the range of values expected in oceanic surface waters, both salinity and total alkalinity affected the pH temperature correction to a small extent ( ΔpH<0.0017). However, by using salinity to estimate the total alkalinity, the error in the calculated pH temperature correction is reduced to less than 0.0002 pH unit over the temperature range 0–40°C.

Stability of Concentrated Colloids: The Controlling Parameters

A theoretical framework has been developed for predicting and explaining the colloidal stability of concentrated dispersions. It is based on multiparticle interaction models for the electrical double layer (EDL) and van der Waals (vdW) interactions. An asymmetric cell model is used for estimating EDL interaction energy from the solution of the Poisson–Boltzmann equation. The unretarded vdW interaction energy is calculated via Hamaker's method, adopting the pairwise-additivity approach. Various dispersion parameters are investigated for their effects on the flocculation energy barrier. These include volume fraction, size, and surface potential of particles, as well as the ionic strength of the dispersing medium. The results show several new trends borne out of multiparticle interaction effects. A maximum in the energy barrier is predicted as a function of salinity, contrasting the monotonic dependence from the classical DLVO theory. This salinity dependence of the energy barrier provides the first comprehensive explanation of reported experimental findings on stability and rheological properties of concentrated dispersions. Other predictions include the occurrence of flocculation at a secondary minimum and the particle-size dependent variation of suspension stability with particle volume fraction.

Effects of water salinity, saturation and clay content on the complex resistivity of sandstone samples

Abstract Complex resistivity measurements were made on sandstone samples in the frequency range from 10 Hz to 2 MHz. The main objective was to investigate the frequency response of complex resistivity and phase angle as a function of salinity, water saturation and clay content. The results showed the classical frequency dependence behaviour where the complex resistivity decreases with increasing frequency. The complex impedance behaviour in the intermediate frequency range (10–100 kHz) was used to relate the effect of frequency dispersion with interface polarization and, hence, pore geometry, specific surface area and permeability. Both water saturation and salinity were found to influence the gradient and the relaxation frequency of the complex resistivity versus frequency relationship. A variation in water saturation from full to partial saturation resulted in a dramatic increase in the gradient and a clear shift of the relaxation frequency. Both the saturation and salinity dependence can be attributed to the polarization of both the rock-fluid and fluid-fluid interfaces within the pore space, which depend on the geometry and physical characteristics of the interfacial layers. The results presented in this paper can have important applications in identifying low resistivity and low contrast pay zones.

Electrochemical nitrite and ammonia oxidation in sea water

Nitrite and ammonia destruction from sea water by an electrochemical oxidation was investigated to determine nitrite and ammonia oxidation efficiencies. Operating conditions considered in the experimental studies included the electric current, pH, initial nitrite and ammonium concentrations and salinity. Both nitrite and ammonia oxidation processes were found to obey a zero‐order kinetics and reaction rate coefficients were a linear function of electric current and a nonlinear function of salinity. Nitrite removal was found to be significantly faster than the ammonia removal. In the presence of an electrolyte (chloride), the indirect oxidations of both nitrite and ammonia by a strong oxidant (hypochlorite) were faster than direct anodic oxidation of the pure component.

Mechanical Properties of First-Year Sea Ice at Tarsiut Island

This paper deals with the interpretation of small-scale first-year sea ice strength and property test data collected in 1982 during several field trips at Tarsiut Island N-44 location in the Canadian Beaufort Sea. Measurements of flexural, horizontal, and vertical uniaxial compressive and confined plane strain and borehole jack strengths are presented. Mathematical relationships representing the variation of these mechanical properties with temperature; salinity; strain and stress rates; and crystal structure (depth) are analyzed. Uniaxial unconfined compressive strength data of horizontal sea ice samples are compared with triaxially confined borehole jack strength data. Flexural strength data obtained from laboratory tests are compared with full-thickness cantilever beam tests performed in the field. The measured flexural strength of first-year sea ice is also provided in a statistical format. The apparent elastic modulus of sea ice is presented as a function of salinity and temperature.

Determination of ammonia in seawater by the indophenol-blue method: Evaluation of the ICES NUTS I/C 5 questionnaire

Abstract Replies to the questionnaire on the determination of ammonia, sent to participants in the Fifth ICES Intercomparison Exercise for nutrients in seawater, are evaluated. The conclusions provide some useful recommendations for analysts. Berthelot's reaction (formation of indophenol-blue) is the basis of the colorimetry used by the great majority of participants, and their individual methods are examined in detail. Application of the indophenol-blue method to seawater poses some specific problems, for example, precipitation, and variation of the pH of the matrix as a function of salinity. Basic principles are discussed and participants' procedures are compared with those most commonly used in the literature. Large disparities in reaction and operating conditions are evident between these many versions of what is nominally the same method. Various points of the reaction mechanism are examined in order to determine optimal ranges for reagent concentrations. Procedures for calibration, measuring the blank, and defining the concentration-zero are also evaluated, as the intercomparison results indicate that systematic (particularly relative) errors are widespread. The use of low-nutrient seawater as a calibration matrix is strongly recommended if errors such as those incurred by the use of demineralised water or artificial seawater are to be avoided. Sources of contamination are discussed, the majority of participants being aware that ambient laboratory air can be a major problem. In general, users of automated methods produce better results than users of manual methods, but this may simply reflect a tendency for the former to be the more experienced analysts. Although it was not possible consistently to relate performance in the intercomparison with methodology, it would appear that many procedures deviate from optimal operating conditions, while some are unnecessarily complicated and might benefit from simplification. Analysts are invited to re-examine their ammonia methods, with particular attention to suitability of reagents and reaction conditions, use of adequate blank and calibration procedures and matrices, correction for refraction effects and identification of local contamination sources.

Effects of Salinity Changes and the Formation of Dissolved Organic Matter Coatings on the Sorption of Phenanthrene: Implications for Pollutant Trapping in Estuaries

Estuaries have been reported to be sinks for hydrophobic pollutants, and sorption has been commonly attributed to be an important mechanism responsible for the observed pollutant trapping. The sorption enhancement caused by “salt effects” and dissolved organic matter (DOM) coatings were both measured and modeled, and the results were used to probe the extent to which equilibrium sorption could explain estuarine pollutant trapping. The polycyclic aromatic compound phenanthrene, an extracellular polymer from a soil bacterial isolate, and a low organic carbon kaolinite were used as models for the hydrophobic pollutant, DOM, and suspended sediment, respectively. Sorptive interactions between phenanthrene, extracellular polymer, and kaolinite were measured at pH 8 as a function of salinity. The experimentally determined binary distribution coefficients were combined using a three-component sorption model to calculate the overall sorption coefficient for phenanthrene, KO. Increasing the ionic strength to seawat...

Uptake of zinc by the midge larvaeChironomus ripariusat different salinities: Role of speciation, acclimation, and calcium

The uptake of zinc by the freshwater midge larvae Chironomus riparius was studied as a function of salinity. Fourth instar larvae were exposed to a salinity range up to 10‰ by diluting chemically defined seawater with chemically defined river water. The effect of prior acclimation at five different salinities on zinc uptake rate was examined. Solutions of different composition were tested to discriminate between the effect of the free zinc ion concentration, the free zinc ion activity, and the free calcium ion activity. Zinc uptake rate decreased with increasing salinity in all exposure solutions. Prior acclimation at salinities up to 10% did not influence zinc uptake rate. Changes in the free zinc ion activity explained most of the observed variation (58%). Changes in calcium ion activity had only a minor effect on zinc uptake (1%). Besides these effects the salinity of the exposure also influences the physiology of the larvae, altering zinc uptake when larvae are transferred from one salinity to another (6%). The combination of the different effects explained 65% of the total variation in zinc uptake by midge larvae. The remaining variation could not be explained by the experimental design and was attributed to natural variation in zinc uptake among midge larvae.

Optical measurements in the North Sea-Baltic Sea transition zone. II. Water mass classification along the Jutland west coast from salinity and spectral irradiance measurements

Spectral irradiance measurements were gathered along three fixed sections outside Thyborøn, Hanstholm and Hirtshals on the north west coast of Denmark during seven cruises with R. V. Svanic in the years 1990–1992. It is argued that the irradiance attenuation coefficient Kd (410) can be taken as a good indicator of yellow substance in the study region. Salinity - Kd (410) scatter plots show that three water types can be identified in the area: Atlantic/Central North Sea water, German Bight water and Baltic water. Estimates of the mean width of the part of the Jutland Coastal Current that primarily is influenced by the freshwater inflow to the German Bight are given for each of the three sections. A salinity- K d (410) water mass analysis was carried out based on long-term mean characteristic values of salinity and K d (410) for the three core water types and the measurements from this study. The average contents of Atlantic/Central North Sea water, German Bight water and Baltic water was estimated for the surface layer at each of the three sections. Based on the volume flow estimates (provided as a function of salinity) from the three sections as listed in Rydberg (Report No. 53, Department of Oceanography, University of Gothenburg, Sweden, 1993) an estimate of the mean volume flow of water with German Bight origin entering the Skagerrak is given.

Stable isotope record of late Holocene salinity and river discharge in San Francisco Bay, California

Oxygen and carbon isotopic measurements of fossil mollusks from San Francisco Bay are used to derive a record of paleosalinity and paleostreamflow for the past 5,900 years. The δ 18O and δ 13C values of river water (−12‰ and −9‰) are markedly different than seawater (0‰ and 1‰), and vary systematically as a function of salinity in the estuary. The data show that annually averaged salinity in the south-central part of the Bay was very close to the modern ‘diversion-corrected’ value of 26.8‰ over the past 2,700 years, and 4‰ lower than modern between 3,800 and 5,100 yr B.P. Based on those salinities, the average annual river inflow to San Francisco Bay is calculated to have been 1290 m 3/s over the past 2,400 years, and 1990 m 3/s between 3,800 and 5,100 yr B.P., 1.8 times greater than the modern ‘diversion-corrected’ value of 1100 m 3/s, assuming a constant bay volume. The inferred river discharge record generally corroborates independent paleohydrologic records in California, including tree-ring, treeline and lake level records.