Theoretical model for the formation of ion-pairs in seawater

Predictions of association constants for ion-pair formation in seawater were compared to measured constants as a test for the existence of ion-pairs. A fair agreement was obtained in most cases, although the theoretical electrostatic calculations indicate that significant chloride ion-pairing should occur which has not been observed in most experimental investigations.     

人工海水中碳酸根—碳酸氢根离子对的研究

本工作测定了有效离子强度I_=0.5277mol/L和25℃下碳酸在若干人工海水介质中的表现离解常数,计算了碳酸根和碳酸氢根与钾、钠、镁、钙的缔合常数,讨论了包括氯离子缔合和未考虑氯离子缔合的海水化学模型,还通过试验证实了钾与碳酸根、碳酸氢根的缔合是不可忽视的,其缔合常数与钠的缔合常数相近,从而扩展了Pytkowic和Hawley(1974)的碳酸根-碳酸氢根离子对的海水化学模型。     

Association constant of fluoride and hydrogen ions in seawater

A method is described to obtain the association constant of fluoride and hydrogen ions and its influence on the total and free ion concentration. The following equation was found with an error of ± 0.05 for the salinity and temperature range 10–40 and 9–33°C, respectively In β_HF = -874/T - 0.111S^0.6 + 9.68 where T is the absolute temperature and S the salinity.     

Interaction of metal complexes with coulombic ion-pairs in aqueous media of high salinity

The competition for anions between the cations of the alkali and alkaline earth metals (to form ion pairs) and the cations of heavy metals (to form complexes) is investigated. The interaction is shown to affect the stability constants of the heavy metal complexes and the nature of the ionic species present in aqueous media of high salinity. The theory is discussed with special reference to NaCl-NaClO₄ solutions, seawater and the labile complexes of lead and cadmium.     

Thallium concentrations in seawater

Measurements of the concentration of thallium in seawater collected from numerous ocean locations ranged from 12 to 16 ng kg⁻¹. Variations between the Atlantic and Pacific Oceans, between the northern and southern hemispheres of the Pacific Ocean, and between surface and deep waters of both the Pacific and Atlantic oceans were comparable with the precision of the analyses. This relatively constant distribution indicates that the element's cycle in seawater may be similar to those of the alkali metals which are its principal biogeochemical analogues.     

Thorium speciation in seawater

Since the 1960s, thorium isotopes occupy a special place in the oceanographer's toolbox as tracers for determining rates and mechanisms of oceanic scavenging, particle dynamics, and carbon fluxes. Due to their unique and constant production rates from soluble parent nuclides of uranium and radium, their disequilibrium can be used to calculate rates and time scales of sinking particles. In addition, by ratio-ing particulate ²³⁴Th (as well, in principle, other Th-nuclides) to carbon (and other elements), and linking this ratio to the parent–daughter disequilibrium in the water column, it is possible to calculate fluxes of carbon and other elements. Most of these applications are possible with little knowledge of the dissolved chemical properties of thorium, other than its oxidation state (IV) and tendency to strongly sorb to surfaces, i.e., its “particle- or surface-activity”. However, the use of any tracer is hindered by a lack of knowledge of its chemical properties. Recent observations in the variability of carbon to ²³⁴Th ratios in different particle types, as well as of associations of Th(IV) with various marine organic biomolecules has led to the need for a review of current knowledge and what future endeavors should be taken to understand the marine chemistry of thorium.     

Silica-alumina interactions in seawater

Amorphous silica can polymerize in distilled water, in 0.6 N NaCl solution and in seawater to form a colloidal suspension that contains approximately 200 ppm Si. Solid amorphous alumina can prevent this polymerization in seawater and in 0.6 N NaCl, and can inhibit but not prevent it in distilled water. This prevention of polymerization may be an important factor in authigenic mineral formation.The presence of solid amorphous alumina with solid silica in the same solutions causes the final concentrations of dissolved silica to be lower than those attained by solid silica in the absence of solid alumina. The effects are similar whether the final levels are approached from above or below the saturation concentration for amorphous silica. This indicates that the observed concentration of dissolved silica will be a function of available alumina as well as of the silica solubility.The presence of solid amorphous alumina with quartz in seawater, 0.6 N NaCl solution and distilled water causes dissolved silica levels to remain below 0.7 ppm Si for at least 38 days. The same systems in the absence of alumina approach the solubility levels of quartz within that time period.     

杭州湾海水中钾、钠、钙、镁、锶和硫酸根的迁移变化研究

以氯度作为保守性指数研究了杭州湾海区由于离子强度的变化水体中钾、钠、钙、镁、锶和硫酸根离子的保守性、非保守性行为,结果发现在测定相对误差分别为±０．２％ ,±０．５％ ,±０．５ ％ ,±０．２％ ,±０ ．５ ％ 时,钾、钠、镁、硫酸根在整个氯度范围内表现为保守性;锶在整个氯度范围内没有规律性的“迁入”或“迁出”行为;钙的不保守行为表现为在氯度６ ～８ 之间有明显的“迁入”,其在低氯和高氯区则具有较好的保守性。并对此结果作了初步探讨。     

Ionization of water in seawater

The ion product of water in seawater and the total activity coefficients of hydroxide and hydrogen ions were determined over the temperature range 2° to 35°C, and the salinity range 20‰ to 44‰. At 25°C and 35‰ salinity, the measured values are pK_W^SW = 13.20, f_OH = 0.22, f_H = 0.71 on the molar concentration scale.     

Polarographic determination of orthophosphate in seawater

-In the system HCl-Sb (Ⅲ)-ammonium molybdatc-acetone-butanone, PO43-, Sb (Ⅲ) and Mo (VI) form ternary heteropoly acid. This ternary heteropoly acid anion is adsorbed on the dropping mercury electrode and reduced quickly into heteropoly blue. The process of electrochemical reaction will produce a sensitive polarographic wave with peak potential -0.42V (vs S.C.E.). The detection limit is 6×10-8 mol/1. Variable coefficients are 10% and 3% for 0.1 μmol/l and 1 μmol/1 respectively.This method is sensitive, accurate and extremely rapid for analysis of seawater.     

MgSO4 ION association in seawater

Examination of the consequences of the stoichiometric association constant $\text{K}{}^1{}_{\mathrm{<mtext>a</mtext>}}\text{= 41.7}$ for MgSO₄ in seawater as advocated by Johnson and Pytkowicz (1979) leads to a thermodynamic association constant K_a = 212.6, a value 32% greater than K_A = 160 derived from conductance data. Use of K_a = 160 leads to a $\text{K}{}^1{}_{\mathrm{<mtext>a</mtext>}}$ in essential agreement with the value of 10.2 reported by Kester and Pytkowicz (1969).     

Photochemical oxidation of dimethylsulfide in seawater

Dimethylsulfide(DMS) is generally thought to be lost from the surface oceans by evasion into the atmosphere as well as consumption by microbe.However,photochemical process might be important in the removal of DMS in the oceanic photic zone.A kinetic investigation into the photochemical oxidation of DMS in seawater was performed.The photo-oxidation rates of DMS were influenced by various factors including the medium,dissolved oxygen,photosensitizers,and heavy metal ions.The photo-oxidation rates of DMS were higher in seawater than in distilled water,presumably due to the effect of salinity existing in seawater.Three usual photosensitizers(humic acid,fulvic acid and anthroquinone),especially in the presence of oxygen,were able to enhance the photo-oxidation rate of DMS,with the fastest rate observed with anthroquinone.Photo-oxidation of DMS followed first order reaction kinetics with the rate constant ranging from 2.5×10-5 to 34.3×10-5 s-1.Quantitative analysis showed that approximately 32% of the photochemically removed DMS was converted to dimethylsulfoxide.One of the important findings was that the presence of Hg2 could markedly accelerate the photo-oxidation rate of DMS in seawater.The mechanism of mercuric catalysis for DMS photolysis was suggested according to the way of CTTM(charge transfer to metal) of DMS-Hg2 complex.     

The fluorine complexation degree in seawater

Ionometric measurements of the complexation degree of fluorides in seawater of 5–35‰ salinity at 25°C were carried out using two procedures for the standardization of the measuring electrochemical circuits. It was shown that, if we determine the degree of the fluorine complexation in seawater using the measured values of the total coefficients of the activity, the fraction of free ions is much dependent on the value used of the activity coefficient of the free ions calculated by means of one of the versions of either the second or third approximation of the Debye-Huckel electrostatic theory of strong electrolyte solutions. With the more correct measurement of the fluorine complexation degree in seawater on the basis of the comparison of the EMF values in pure KCl-KF solutions and in mixtures of these solutions and seawater at equal ionic power and fluoride concentrations, a close correlation was revealed for the free ion fraction in three series of experiments at fluorine contents of 0.2, 0.3, and 0.4 mM (the concentration of the fluorine in seawater of 35‰ salinity amounts to 0.421 ± 0.014 mM.)     

海水垂向入侵问题研究进展

随着全球气候变暖,风暴潮在沿海地区的频率和强度均可能增长,由此引发的海水垂向入侵可能会造成大面积的含水层淡水咸化。同时,由人类活动引起的沿海虾塘咸水养殖规模日益增长,由此引发的咸水垂向入侵可能会导致沿海地区地下水水质及生态环境的恶化。虽然已有一部分学者在海水(咸水)垂向入侵的研究中取得了成果,但由于海水(咸水)垂向入侵过程复杂,其对地下水咸化及恢复规律依然有待深入研究。文章阐述了海水垂向入侵的危害及前人的研究办法,总结了他们的研究成果并得出了海水垂向入侵的影响因子,指出了洪水和养殖活动对沿海地区含水层的威胁。得出的结果如下:研究海水垂向入侵常用的方法包括室内试验和数值模拟;海水垂向入侵主要与地形地貌、含水层性质和水文气象条件有关;虾塘养殖等人类活动可能会成为垂向咸水入侵的潜在来源。建议未来在海水垂向入侵研究中将多种现场观测实验方法结合起来。数值模拟应注重与现场观测实验数据相互验证,模型简化的方式有必要仔细考虑。虾塘养殖等人类活动可能造成的垂向咸水入侵问题应更多地受到关注。     

Nitrite photolysis in seawater by sunlight

Nitrite is chemically stable but photochemically unstable in seawater. The net disappearance rate in abiotic low-nitrate seawater exposed to sunlight is ～ 10% per day. The primary products are the free radicals NO and OH. Quantitative aspects of the kinetics and secondary product formation are discussed in terms of a fourteen-step reaction scheme. Possible pathways explaining the results are suggested but not unequivocally identified.The rate of reaction in various marine environments is estimated from cruise data and extrapolations to vary between 0.2–60·10^?3 moles m^?2yr^?1, with a suggested global average for comparison purposes of 1–10·10³ moles m^?2yr^?1.These results confirm and quantify our previous suggestion that nitrite photolysis represents a source of OH radical in seawater. The reaction rate is large enough that significant impacts on the geochemical cycles of dissolved organic carbon and nitrogen and heavy metals may plausibly result. Effects on marine biota and atmospheric trace gas composition are also possible. However, specific reactions coupling the nitrite system to other processes have not yet been identified or demonstrated empirically.     

Oscillopolarographic determination of microsillicon in seawater

A new oscillopolarographic method for the determination of Si (Ⅳ) is described in this paper. In the system HC1- Sb(Ⅲ) -Mo(Ⅵ) -NaCl-ethyl alcohol, Si (Ⅳ) with Sb (Ⅲ) and Mo (Ⅵ) form ternary heteropoly acid. The anion of ternary heteropoly is adsorbed on the dropping mercury electrobe and under proper electric potentials reduced quickly into heteropoly blue. The process of electrochemical reaction will produce a sensitive polarographic wave with peak potential at- 0. 30(Vs. SCE). The lower limit of determination is 8×10-8 mol/dm3. This method is sensitive, accurate and extremely rapid for the determination of micro-silicon in seawater.     

High molecular-weight material in Baltic seawater

The concentration of high molecular-weight material (>10,000), HMWM, in Baltic water was estimated by Amicon membrane ultra-filtration, followed by transmission spectroscopy of the concentrate. In most cases, the HMWM accounted for about 1% of the dissolved organic matter as estimated by absorption measurements at 280 nm. A loss of HMWM with increasing salinity is indicated.