Major Ions In Seawater Research Articles

Competition Between O2 and H2O2 in the Oxidation of Fe(II) in Natural Waters

The oxidation rates of nanomolar levels of Fe(II) in seawater (salinity S = 36.2) by mixtures of O2 and H2O2 has been measured as a function of pH (5.8–8.4) and temperature (3–35∘C). A competition exists for the oxidation of Fe(II) in the presence of both O2 (μ mol⋅L−1 levels) and H2O2 (nmol⋅L−1 levels). A kinetic model has been applied to explain the experimental results that considers the interactions of Fe(II) with the major ions in seawater. In the presence of both oxidants, the hydrolyzed Fe(II) species dominate the Fe(II) oxidation process between pH 6 and 8.5. Over pH range 6.2–7.9, the FeOH+ species are the most active, whereas above pH 7.9, the Fe(OH)02 species are the most active at the levels of CO2−3 concentration present in seawater. The predicted Fe(II) oxidation rate at [Fe(II)]0 = 30nmol⋅L−1 and pH = 8.17 in the oxygen-saturated seawater with [H2O2]0 = 50nmol⋅L−1 (log 10 k = −2.24s−1) is in excellent agreement with the experimental value of log 10 k = −2.29s−1 ([H2O2]0 = 55nmol⋅L−1, pH = 8).

Oxidation of iron (II) nanomolar with H 2O 2 in seawater

The oxidation of Fe(II) with H 2O 2 at nanomolar levels in seawater have been studied using an UV-Vis spectrophotometric system equipped with a long liquid waveguide capillary flow cell. The effect of pH (6.5 to 8.2), H 2O 2 (7.2 × 10 −8 M to 5.2 × 10 −7 M), HCO 3 − (2.05 mM to 4.05 mM) and Fe(II) (5 nM to 500 nM) as a function of temperature (3 to 35 °C) on the oxidation of Fe(II) are presented. The oxidation rate is linearly related to the pH with a slope of 0.89 ± 0.01 independent of the concentration of HCO 3 −. A kinetic model for the reaction has been developed to consider the interactions of Fe(II) with the major ions in seawater. The model has been used to examine the effect of pH, concentrations of Fe(II), H 2O 2 and HCO 3 − as a function of temperature. FeOH + is the most important contributing species to the overall rate of oxidation from pH 6 to pH 8. At a pH higher than 8, the Fe(OH) 2 and Fe(CO 3) 2 2− species contribute over 20% to the rates. Model results show that when the concentration of O 2 is two orders of magnitude higher than the concentration of H 2O 2, the oxidation with O 2 also needs to be considered. The rate constants for the five most kinetically active species (Fe 2+, FeOH +, Fe(OH) 2, FeCO 3, Fe(CO 3) 2 2−) in seawater as a function of temperature have been determined. The kinetic model is also valid in pure water with different concentrations of HCO 3 − and the conditions found in fresh waters.

Adsorption of Co 2+, Ni 2+, Cu 2+ and Zn 2+ from 0.5 M NaCl and major ion sea water on a mixture of δ-MnO 2 and amorphous FeOOH

The pH pzc values of several mechanical mixtures of amorphous hydrous oxides of iron (amorphous FeOOH) and manganese ( δ-MnO 2) have been determined using the solid addition method. While the pH pzc of δ-MnO 2 remains almost unchanged, the corresponding value for amorphous FeOOH tends to increase with increased proportion of δ-MnO 2 in the mixtures. The adsorption behavior of Co 2+, Ni 2+, Cu 2+, and Zn 2+ with respect to pH on a mechanical mixture of 70% δ-MnO 2 and 30% amorphous FeOOH from 0.5 M NaCl and major ion sea water has been studied. Since δ-MnO 2 is much more active adsorbent than amorphous FeOOH at pH below 6.5, the adsorption data on mixture have not only been normalized with respect to the mass of δ-MnO 2 in the mixture, but also compared with adsorption data on δ-MnO 2 alone. It is interesting to note that though each trace metal behaves in a different way from the other especially with respect to the nature of electrolyte medium, it is generally observed that the adsorption on the mixed oxide system is higher than that on δ-MnO 2 alone under similar condition. It is also observed that adsorption in major ion sea water at a particular pH value is lower than in 0.5 M NaCl solution.

Adsorption of Co, Ni, Cu, and Zn on hydrous manganese dioxide from complex electrolyte solutions resembling sea water in major ion content

Adsorption of Co, Ni, Cu, and Zn onto a poorly crystalline hydrous manganese dioxide (δ-MnO2) has been studied in complex electrolyte solutions such as (a) 0.5 M NaCl+0.054 M MgCl2, (b) 0.5 M NaCl+0.028 M Na2SO4, and (c) artificial sea water prepared according to the standard literature method. These three solutions allow us to identify the specific effect of major cations, major anions, and the mixture of major cations and anions (including carbonate and bicarbonate) that is present in real sea water. The adsorption isotherm in major ion sea water at pH 7.25 indicates that while Co and Zn exhibit increases in adsorption with increase in concentration, Ni shows relatively poor adsorption, reaching a plateau at 0.075 mM concentration. The three trace metals (Co, Ni, and Zn) show Langmuirian behavior for adsorption at low concentration. It is generally observed that the fractional adsorption vs pH curve shifts to higher pH either in the presence of 0.054 M MgCl2 or in sea water. In the presence of 0.028 M Na2SO4 the fractional adsorption vs pH curve remains almost unchanged with respect to a 0.5 M NaCl solution. The competitive adsorption of one trace metal in the presence of other three in major ion sea water indicates that this phenomenon is more predominant with Ni and Zn than with Co and Cu.

Development and validation of models predicting the toxicity of major seawater ions to the mysid shrimp,Americamysis bahia

The concentration and balance of major ions that comprise total dissolved solids (TDS) can influence the toxicity of effluents discharged to freshwater and marine environments. An additional complicating factor in waters released to saltwater systems is the effluent salinity since the toxicity of major ions changes with the salinity of the test solution. A study was conducted to evaluate the toxicity of six major seawater ions (bicarbonate, borate, calcium, magnesium, potassium, and sulfate) to the mysid shrimp, Americamysis bahia, at salinities of 10 and 20/1000. Logistic regression models were developed to predict organism survival at deficient and excess concentrations of the ions. Calcium and potassium caused significant mortality to mysid shrimp in both excess and deficient (relative to artificial seawater) solutions. Bicarbonate, borate, and magnesium displayed significant toxicity only in excess concentrations, while sulfate had no adverse impacts at any of the concentrations tested. As the salinity of the test solutions decreased, mysid shrimp tolerated increasingly lower calcium and potassium concentrations. Similarly, as salinity increased, the upper tolerance levels of calcium, potassium, and magnesium also increased. The models developed during these studies, and similar models developed by other researchers, were used to evaluate 11 actual effluents with unexplained toxicity that might be associated with TDS ions. The models correctly identified calcium as the primary toxicant in 9 of the 11 effluents. These results indicate the models can be used as an important tool to identify toxicity associated with major seawater ions.

Real-time measurement of sodium in single aerosol particles by flame emission: laboratory characterization

A flame emission aerosol sodium detector (ASD) has been developed to study the distribution of seasalt in individual marine aerosol droplets. The instrument detects sodium via D-line emission in a fuel-rich, laminar, hydrogen/oxygen/nitrogen flame. Laboratory studies with synthetic monodisperse aerosols were carried out in order to characterize the sensitivity, precision, and linearity of the technique. Experiments were also carried out with aerosols generated from mixed salt solutions and seawater in order to determine whether ionic or other matrix effects lead to interference. The ASD has a linear response function for NaCl aerosol particles from 100 nm to 2.0 μm in diameter. The precision of sodium mass measurements is on the order of ±3% standard error on replicate measurements, with a quantitative response to the sodium content of a single aerosol particle that is independent of the chemical composition of the particle, i.e. anions, cations, seawater. No interferences were found with major ions in seawater and common atmospheric aerosols. These experiments demonstrate a detection limit equivalent to a 100 nm diameter dry 100% NaCl aerosol.

Differences in Major Ions Composition of Artificial Seawater from Aquarium Tanks at the New Jersey State Aquarium

Concentrations of major seawater ions were monitored in six aquarium tanks at the New Jersey State Aquarium over a three-year period. The ratios of these ions to chlorinity were compared to those in freshly prepared artificial seawater. The largest aquarium tank (Ocean Tank) exhibits statistically significant (p<0.01) relative enrichment of potassium, calcium and strontium, and relative depletion of magnesium and sulphate. The likely source of excess potassium is from potassium iodide added to prevent goiter in sharks. Based on the excess potassium, a total amount of 650 µmol/kg iodide added over the years was calculated for the Ocean Tank. The excess calcium observed in several tanks correlates with the presence of concrete or arbonaceous shells in these tanks. In Ocean Tank, a calcium leaching rate of 6.7 kg/month was calculated. Continuous formation of white carbonaceous precipitates serves as a sink for magnesium in Ocean Tank, and a magnesium removal rate of 5.1 kg/month was calculated. These and other results show that concentrations of major ions in artificial seawater aquaria are affected by leaching, precipitation and addition of food supplements, and these factors should be taken into account when preparing artificial seawater for aquarium tanks with long water residence time.

On-line preconcentration of chromium(III) and speciation of chromium in waters by flame atomic absorption spectrometry

The chemistry of complexation has been investigated and conditions optimized for on-line preconcentration of CrIII by resins with immobilized quinolin-8-ol or iminodiacetate functional groups. When solutions were buffered to 0.1 mol l–1 acetate at pH 9, the detection limit of CrIII was 6 ng ml–1 for preconcentration on the quinolin-8-ol resin at 6 ml min–1 for 3 min. With the iminodiacetate resin (Muromac A-1), the optimum buffer conditions were 0.1 mol l–1 acetate at pH 4, which gave a CrIII detection limit of 2 ng ml–1(3 min preconcentration at 6 ml min–1). The major ions in sea-water did not interfere with preconcentration of 100 ng ml–1 CrIII by Muromac A-1. However, suppressive interferences were caused by 100 µg ml–1 of Ca2+ or Fe2+ with the quinolin-8-ol resin. Despite having similar log stability constants of complexation with either resin, the interference caused by Ca2+ was much greater than that by Mg2+. Muromac A-1 was used for preconcentration of CrIII in estuarine- and sea-waters, prior to determination by flame atomic absorption spectrometry (FAAS). By reduction of CrVI to CrIII, it was also possible to determine the total concentration of ionic Cr in the waters, which allowed calculation of the CrVI concentration by difference. The CrIII concentration in the samples from the Clyde estuary were 3–8 ng ml–1, with the CrVI concentration about 0.7 ng ml–1. Only CrIII(3 ng ml–1) was found in the sea-water samples from the Cumbrian Coast.

Study of the complexation chemistry and speciation of thallium for on-line preconcentration with immobilised quinolin-8-ol

The effects of various buffering reagents and pH conditions were investigated by flame atomic absorption spectrometry to optimise complexation of T13+ with quinolin-8-ol (8-Q), immobilised on controlled-pore glass beads in a 5-cm column. As Tl3+ is a softer acid than the other trivalent cations of the Group III elements, the effects of the buffers are different from those observed previously for Al3+, Ga3+ and In3+. A mixed buffer of 0.1 mol l−1 acetate and 0.1 mol l−1 ammonium chloride at pH 10 proved most successful, although 0.1 mol l−1 maleate was also satisfactory over a pH range of 4–10. As thallium normally exists as Tl+ in solution, an oxidation method was developed to convert the ions to Tl3+, which is more efficiently complexed by 8-Q. Addition of 1–10 μl of bromine per 100 ml of sample was sufficient to oxidise Tl+ without heating. Excess bromine was removed by addition of phenol. With a flow-rate of 6 ml min−1, the detection limit of Tl3+ is 3 ng ml−1, for a 3-miri preconcentration time. The enrichment factor under these conditions is 55 and the characteristic concentration is 2 ng ml−1. The major ions in sea water did not interfere with Tl3+ preconcentration and the tolerable limits of Fe3+, Cu2+ and Al3+ are high enough to permit analysis of river and sea waters. The method was applied successfully to the determination of thallium in potassium-enriched table salt. It was also shown that the concentrations of Tl+ and Tl3+ in a solution can be derived using the described procedure, allowing speciation of inorganic thallium.

Adsorption of Cations on Hydrous Oxides of Iron

Abstract The adsorption behavior of Mn, Co, Ni, and Zn onto a synthetic akageneite (β-FeOOH) sample from different background electrolyte solutions, such as KNO3, NaCl, and major ion seawater, has been studied. Constant pH adsorption isotherms indicate the heterogeneous nature of the adsorbent surface, and Langmuirian behavior is followed only for concentrations below 10-5M of the metal ions. The effect of pH shows that the adsorption edge shifts to the alkaline side not only with increasing concentration of the electrolyte solution but also in major ion seawater. The extent of metal ion uptake calculated from different surface complexation models is found to predict 50-90% of the adsorption depending upon the trace metal as well as on the supporting electrolyte medium. This also suggests more than one adsorption site on akaganeite. A critical appraisal of the adsorption behavior of hydrous iron oxides is presented.

Sorption of cadmium on suspended matter under estuarine conditions; competition and complexation with major sea-water ions

Sorption of Cd at low concentrations onto river Rhine suspended matter was examined in terms of sorption rate, reversibility and factors such as competition and complexation with major inorganic sea-water ions. More than 90% of the final amount of Cd is sorbed within the first few hours. Desorption experiments show that the process is virtually reversible. In experiments with diluted sea water the sorption of Cd strongly decreases even at low salinity. Sorption isotherms show that the sorption of Cd in NaNO3 solutions is regulated by the free Cd2+ activity. In a Ca(NO3)2 environment the Cd sorption decreases with increasing Ca2+ concentrations, which implies competition between Ca2+ and Cd2+ for the different sorption sites. In different electrolyte solutions of similar ionic strength the sorption of Cd decreases in the solution order NaNO3 > NaCl > NaCl+MgCl2+CaCl2 > diluted sea water. Although inorganic speciation calculations show that even at low salinities dissolved Cd is dominated by Cd-chloro complexes, chloride accounts for only about one third of the increased mobility of Cd. As a result of addition of Ca2+ and Mg2+ the sorption capacity of suspended matter for Cd is further reduced by a factor three.

Adsorption of Cations on Hydrous Oxides of Iron

The adsorption behavior of Mn, Co, Ni, and Zn onto an amorphous FeOOH sample from different electrolyte solutions such as KNO 3 , NaCl, and major ion seawater has been studied. The electrolyte medium was varied in such a way that the effect of each major cation and anion on the adsorption of the trace metal could be evaluated separately. Adsorption isotherms at constant pH values indicate that adsorption of these trace metals is non-Langmuirian in the range of concentration studied. It also has been observed that at the present adsorbate/adsorbent ratio the presence of 0.054 M MgCl 2 in 0.5 M NaCl shifts the adsorption edge to the alkaline side; the presence of 0.028 M Na 2 SO 4 does not lead to increased adsorption with respect to 0.5 M NaCl alone. While Co and Ni exhibit strong competition for higher energy surface sites, Mn shows little and Zn exhibits no competition for surface sites. Adsorption of Zn is therefore almost independent of the nature of the background electrolyte solutions. Intrinsic binding constants have been determined by different methods and appropriate values were chosen after considering different conjectures. It is observed that the triple-layer model fits the experimental data at least up to pH 7.5, above which surface precipitation plays an important role at the present adsorbate/adsorbent ratio.

Determination of picomolar concentrations of titanium, gallium and indium in sea water by inductively coupled plasma mass spectrometry following an 8-hydroxyquinoline chelating resin preconcentration

Picomolar concentrations of dissolved titanium, gallium and indium in sea water are measured using inductively coupled plasma mass spectrometry (ICP-MS) after concentration and separation from the major ions in sea water via an 8-hydroxyquinoline chelating ion exchange resin (TSK-8HQ). Detection limits of 5–10 pM (0.2–0.4 part per trillion, ppt), 0.5 pM (0.02 ppt) and 0.1 pM (0.01 ppt) were found for Ti, Ga and In, respectively, after a 400-fold (Ti) or 3000-fold (Ga and In) concentration. The detection was blank limited for Ti, due primarily to background interferences from the HNO 3 matrix, and sensitivity limited for Ga and In. Open ocean sea water concentrations for these elements are in the range of 6–300 pM for Ti, 2–60 pM for Ga, and 0.1–2.0 pM for In. Sampling and analytical precision of 7–10% was generally found for concentrations greater than twice the detection limit.

Determination of nonionic surfactants by spectrophotometry after extraction with potassium triiodide

A method is described for the determination of nonionic surfactants in the concentration range 0.1-1 mg 1 −1. The surfactant is extractec into 1,1,1-trichloroethane as an uncharged adduct twith pottasium triiodide and the determination is completed by measuring the absorbance of the extract at 380 nm. The performance of the method in the presence of anionic surfactants and the major ions of sea water is assessed.

Coprecipitation of manganese from marine sediment pore waters for x-ray fluorescence spectrometry

Dissolved manganese at the μ l −1 level is coprecipitated with a cobalt pyrrolidinecarbodithioate (tetramethylenedithiocarbamate) carrier complex for analysis by film x-ray fluorescence spectrometry. The detection limit, for 100-ml samples and a total counting time of 180 s, is 50 ng Mn l −1. The major ions in sea water do not interfere and colloidal Mn(III)/Mn(IV) oxides respond with the same efficiency as Mn (II). The method is used, with electron-spin resonance spectrometry, to study dissolved manganese in the anoxic pore waters of marine sediments.

The influence of the major ions of seawater on the adsorption of simple organic acids by goethite

The adsorption of oxalic, phthalic, salicylic, and lactic acids on goethite from 0.53 M NaCl and from synthetic major ion sea water is examined to determine the effect of Mg, Ca, and SO/sub 4/ on the adsorption behavior of the organic compounds. The comparison shows that organic acid adsorption is suppressed in sea water relative to the NaCl system. Successive additions of SO/sub 4/, Mg, and Ca in their natural ionic proportions found in sea water to 0.53 M NaCl indicate that sulfate suppresses the adsorption of all the organic acids, especially in the low pH range. The addition of Mg also suppresses the adsorption of oxalic and phthalic acids while the addition of Ca suppresses lactic acid adsorption. The effect of SO/sub 4/, Mg and Ca on the adsorption of the organic acids is due to competition for available binding sites and the formation of solution complexes which either do not absorb or weakly absorb.

87:6218 The influence of the major ions of seawater on the adsorption of simple organic acids by goethite: Balistrieri, L.S. and J.W. Murray, 1987. Geochim. cosmochim. Acta, 51(5):1151–1160

87:6218 The influence of the major ions of seawater on the adsorption of simple organic acids by goethite: Balistrieri, L.S. and J.W. Murray, 1987. Geochim. cosmochim. Acta, 51(5):1151–1160

The effect of seawater magnesium on natural fluorescence during estuarine mixing, and implications for tracer applications

Natural fluorescence, which is thought to result from low molecular weight humic and fulvic compounds, can be used as a tracer to distinguish between individual river waters. Natural fluorescence exhibits conservative mixing with seawater, except for a slight fluorescence increase which is sometimes observed in the low salinity range (0–5‰). This increase is not due to the inner filter effect (internal quenching). Laboratory experiments can reproduce this low-salinity natural fluorescence increase. Of the major seawater ions, only magnesium can cause a similar natural fluorescence increase. Variation in sample pH, ionic strength, or particle content cannot explain the natural fluorescence increase, nor does it appear to be related to the estuarine flocculation of humic material. Addition of seawater magnesium to the fluorescent material with subsequent loss of hydrogen ions could enhance fluorescence by adding crosslinking to the structure. Replacement of a fluorescence-depressing metal like copper or iron by magnesium could also enhance fluorescence, essentially by removing the quenching effect of the metal. Experimental data in this study are consistent with both of these possible mechanisms. Calcium also enhances fluorescence, however the effect of seawater calcium during estuarine mixing is not as apparent as the magnesium effect. The implications of this low-salinity natural fluorescence increase with respect to estuarine and coastal tracer applications depend on whether individual rivers mix in the high or low salinity region of an estuary or coastal area.

The adsorption of Cu, Pb, Zn, and Cd on goethite from major ion seawater

The adsorption of Cu, Pb, Zn, and Cd on goethite (αFeOOH) from NaNO 3 solutions and from major ion seawater was compared to assess the effect of the major ions of seawater (Na, Mg, Ca, K, Cl, and SO 4) on the adsorption behavior of the metals. Magnesium and sulphate are the principal seawater ions which enhance or inhibit adsorption relative to the inert system. Their effect, as determined from the site-binding model of Davis et al. (1978), was a combination of changing the electrostatic conditions at the interface and decreasing the available binding sites. The basic differences between the experimental system of major ion seawater and natural seawater were examined. It was concluded that: 1) although the experimental metal concentrations in major ion seawater were higher than those found in natural seawater, estimates of the binding energy of Cu, Zn, and Cd with αFeOOH for natural seawater concentrations could be made from the data, 2) Cu, Pb, Zn, and Cd showed little or no competition for surface sites on goethite, and 3) the presence of carbonate, phosphate, and silicate had little or no effect on the adsorption of Zn and Cd on goethite.

The surface chemistry of δMnO 2 in major ion sea water

The surface chemistry of δMnO 2 in major ion seawater is defined by determining the stoichiometry of the reactions which describe the association of the surface hydroxyl groups with Na, Mg, Ca, and K ions, the intrinsic equilibrium constants which define these reactions, and the speciation of the surface at pH 8. The results indicate: 1. 1) that the surface forms monodentate complexes with Na and K ions and bidentate complexes with Mg and Ca ions; 2. 2) that pK 2 INT = 4.2, p ∗K INT Na = 3.0 ± 0.3 , p ∗K INT K = 2.0 ± 0.2 , p ∗K INT >Mg = 3.9 ± 0.1 , and p ∗K INT >Ca = 3.3 ; and 3. 3) ion exchange processes other than with H are important and as a result 84.8% of the surface sites of δMnO 2 in major ion seawater at pH 8 are complexed by H, 8.4% by Mg, 4.6% by Ca, 1.6% by Na, and 0.6% by K. Chloride and sulphate do not adsorb on δMnO 2 in the pH range of natural waters.