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1.
The presence of electrolytes (salts) in aqueous solution modifies the solubility and related properties of organic compounds in water. Reported data for salting-out constants (Setschenow constants) which relate solubility to the salt concentration of aromatic and alkane hydrocarbons, and their chlorinated derivatives, and some organic acids have been compiled for 25 aqueous salt solutions at 20–25 °C. The salting-out sequences for various electrolytes are discussed and it is shown that the salting-out effect is greater for organic solutes with large molar volumes. A compilation of salting-out constants for NaCl solutions and seawater (natural or synthetic) with a variety of solutes, shows that the Setschenow constants are similar for natural or artificial seawater (at salinity of 30–35%.) and NaCl solutions (at 3.0–3.5% or 0.5 M). A simple correlation is suggested for estimating the Setschenow constants for a variety of organic solutes in seawater which typically yields a reduction in solubility by a factor of 1.36. The hydrophobicity of organic solutes is therefore increased by this factor, as is the air-water partition coefficient, implying an increased partitioning from aqueous solution into air, organic carbon and lipid phases. The effect must be quantified when comparing the behavior of organic contaminants in freshwater and marine conditions. 相似文献
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Comparisons of yttrium and rare earth stability constants for organic ligands indicate that Y(III)-organic complexation behavior most closely resembles, on average, the complexation characteristics of Sm(III). Yttrium organic complexation behavior distinctly differs from the behavior of Ho(III), whose ionic radius is most similar to that of yttrium. However, our stability constant comparisons demonstrate that the most reliable basis for predicting Y(III) organic stability constants are predictions based on the complexation behavior of Ho(III). Linear free energy relationships between Ho(III) and Y(III) exhibit better fits than those obtained for other rare earth elements, and much better fits than those obtained between Sm(III) and Y(III).The comparative abundances and distributions of yttrium and the rare earths in seawater are controlled by competitive equilibria between inorganic solution ligands and organic surface ligands. Due to yttrium solution complexation with hard inorganic ligands resembling that of Ho(III) and, yttrium surface complexation with soft organic ligands resembling that of light rare earth elements, the input normalized abundances of yttrium and the rare earths should be decoupled in seawater. In its seawater scavenging behavior, yttrium should act as a pseudolanthanide even heavier than the heaviest rare earth element, lutetium. 相似文献
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Masachika Maeda 《Journal of Oceanography》1980,36(3):167-176
This article summarizes the author's current work on microbial degradation of nucleic acid. The aim of this work is to elucidate parts of the saprogenic process in the marine ecosystem through the study of the behavior of nucleic acid-hydrolyzing bacteria inhabiting seawater and sediments.Considerably large population of nucleic acid-hydrolyzing bacteria was found to occur in seawater and sediments. The main genera of these microbes areVibrio spp. in coastal seas, andPseudomonas spp. in the oceanic waters. As a result of microbial attack, nucleic acid components are released into seawater. The properties of extracellular nuclease produced by a marineVibrio sp. are well adapted to the seawater environment; consequently this enzyme has high activity and stability in seawater. By determining nuclease activity in seawater and sediments, the intensities of nucleic acid-hydrolysisin situ were evaluated.Distribution patterns of marine bacteria are also discussed in reference to the occurrence of phytoplankton in seawater. 相似文献
4.
A novel approach to in situ extraction of Cs radionuclides from seawater is described which offers many advantages over previous methods. Cesium (stable and radioactive) is partially stripped from seawater as it passes in series through a tandem cartridge consisting of twin beds of ion exchange resin impregnated with cupric ferrocyanide. It is demonstrated that, when seawater passes through this cartridge at a constant flow-rate, collection efficiencies of each bed are the same, allowing the calculation of the seawater Cs nuclide concentration. The cartridge is made of inexpensive, readily available, PVC pipe fittings and is easily deployed under various field conditions. Procedures are described for resin preparation and desorption and radiochemical purification of the collected Cs. Thousands of liters of seawater can be stripped of Cs in this way, permitting substantial improvement in the sensitivity of measurement of 134Cs and 137Cs. 相似文献
5.
研究了氧化还原电位(Oxidation Reduction Potential, ORP)对海水中碳钢腐蚀电化学特征的影响,应用动电位极化曲线法探讨了 ORP 与碳钢腐蚀行为之间的关系。结果表明,海水的 ORP 参数对碳钢腐蚀行为具有较大的影响,其中 O2/OH?电对的作用占主导,其他电对如 Fe3+/Fe2+也有一定的影响。随着海水 ORP 的增大,其氧化能力越强,碳钢腐蚀电流增大,腐蚀速度加快。水质相对稳定的开放性大洋海水中,可以考虑海水氧化还原电位在碳钢腐蚀速度预测评估中的应用。 相似文献
6.
Particulate fluxes were determined by two methods to elucidate the behavior of settling particles in seawater. One method involves direct observation of fluxes with sediment traps, while in the other method flux is indirectly calculated from the radioactive disequilibrium between U-238 and Th-234 in seawater, which gives net flux. Observations were carried out several times throughout a year in Funka Bay. When linearly extrapolated, the observed gross fluxes of Th-234 did not converge to zero at the surface. In the subsurface water the difference between the observed and calculated fluxes showed a seasonal variation. The observed fluxes roughly coincided with the calculated net fluxes in the summer stratified water but the observedfluxes were much larger than the calculated ones in the convective winter water. Conversely the observed fluxes were smaller than the calculated ones in spring when the water was exchanging. These results suggest that we can apply this two approach method to get information not only on the behavior of settling particles in seawater but also on the physical stability of water. 相似文献
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西南印度洋中脊热液产物稀土元素组成变化及其来源 总被引：1，自引：1，他引：0
对西南印度洋中脊热液区不同热液产物稀土元素(REE)进行了分析,探讨了热液产物形成过程中稀土元素组成变化及其来源。研究结果表明:不同热液产物稀土元素总量变化范围从3.47×10-7到4.80×10-5,轻重稀土比值(LREE/HREE)从2.06到6.16,表明轻重稀土有较大程度分异,δEu异常(δEu=0.86~3.88)和δCe异常(δCe=0.40~0.86)显示热液产物中REE呈Eu富集和Ce亏损特征。稀土元素球粒陨石标准化模式呈现两种类型:(1)呈轻微富集LREE的平坦模式,REE大于2×10-5;(2)呈显著富集LREE和正Eu异常模式,REE小于5×10-7。模式1类似于洋壳火山岩REE配分模式,而模式2与西南印度洋中脊黑烟囱REE模式相似,也与典型洋中脊热液喷口流体和硫化物LREE富集和正Eu异常模式类似。热液产物中稀土元素含量变化和模式特征以及Mg与LREE极强正相关关系可能反映了西南印度洋中脊硫化物形成在热液流体与海水混合沉淀的初始阶段,后期经历了广泛的热液流体再循环和海水蚀变过程。 相似文献
9.
针对透明度盘只能在白天开展海水透明度测量,易受自然环境和人为因素影响、客观定量性较差的不足,提出了基于海水固有光学性质的海水透明度计算方法。该方法仿真透明度盘测量海水透明度的基本原理,采用蒙特卡罗方法,利用海水固有光学性质,计算透明度盘所处位置海水上涌光相对量,结合对比度传输方程和人眼阈值,建立了基于海水固有光学性质的海水透明度计算模型。利用2006年1月至2月共37组海水透明度的观测数据与该模型数值实验结果比较表明,测量与计算值平均绝对误差为1.1 m。利用该方法可以客观、定量、准确地计算海水透明度,并且为夜间海水透明度要素计算增加了一种新途径。 相似文献
10.
A direct, spectrophotometric method has been adapted for quantitative determination of nitrate concentrations in seawater. The method is based on nitration of resorcinol in acidified seawater, resulting in a color product. The absorption spectrum obtained for the reaction product shows a maximum absorption at 505 nm, with a molar absorptivity of 1.7 × 104 L mol− 1 cm− 1. This method has a detection limit of 0.5 μM and is linear up to 400 μM for nitrate. The advantage of this method is that all reagents are in aqueous solutions without involving cadmium granules as a heterogeneous reactant, as in conventional methods, and therefore is simple to implement. Application of the resorcinol to seawater analysis demonstrated that the results obtained are in good agreement with the conventional approach involving the reduction of nitrate by cadmium followed by diazotization. 相似文献
11.
With the rising cost of oil the electric power generating companies are turning to coal as a fuel source. Large amounts of fly ash are produced as a by product of coal combustion. This fly ash must then be disposed of, with the oceans being considered an alternative to land fill disposal. This research investigated the sorptive behavior of the surface-associated arsenic and utilized the results to project arsenic's impact on the water column during the ocean disposal of fly ash.Several acid digests were investigated to determine an effective method of arsenic recovery from fly ash. Of these, the HCl digest was the most effective technique, yielding 100% arsenic recoveries from fly-ash particles. The arsenic content of the fly ashes studied varied from 69 ± 11 μg g−1 to 323 ± 24 μg g−1, reflecting differences in the arsenic content of the source coal. In both seawater and freshwater there is an increase in arsenic desorption with increasing pH. The greatest release of arsenic occurred at pH 12 with generally over 80% of the surface arsenic released.Fly ash in contact with seawater and freshwater can exhibit either acidic or alkaline tendencies depending upon the soluble elemental composition on the surface of the flyash particle. The acidic ashes were shown to leach a greater percentage of arsenic (16.9%) than the more alkaline ashes (8.2%). During these leaching studies in seawater, arsenic was found to leach in both the pentavalent and trivalent oxidation state. The pentavalent state was predominant, comprising 77% of the arsenic initially desorbed.The dissolution in seawater of arsenic was utilized to assess the possible impact of the ocean disposal of fly ash. Based upon these data it appears that the natural levels of arsenic in the water column would not be significantly increased. Further research is needed on the fate of fly-ash particles in marine sediments. 相似文献
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以Web of Science数据库核心合集内收录的1971—2020年海水淡化文献为数据源,借助CiteSpace对国际海水淡化研究领域的国家和研究机构、关键词、参考文献、期刊与基金等信息进行分析,提出国际海水淡化技术演进大致经历了三个阶段:起步阶段;以反渗透、多级闪蒸、超滤、微滤等研究为主的积累阶段;减压渗透、正渗透、纳米颗粒、石墨烯等海水淡化新材料新技术不断涌现的快速发展阶段。同时,从技术进步和政策支持两个方面提出了对国内相关研究的借鉴与启示。 相似文献
13.
Joan D. Willey 《Marine Chemistry》1978,7(1):53-65
Natural marine sediments can release dissolved silica to silica-poor seawater and can remove silica from seawater enriched with dissolved silica. These are fast reactions, with sufficient reaction occurring within the first 48 hours to indicate clearly the direction of the reaction. The relative importance of these two processes varies with the ratio of clays to biogenic silica in the sediment. Both the release and the uptake reactions approach the interstitial water concentration of dissolved silica as an end point, which suggests that these reactions may influence this concentration. No change in sediment reactivity with respect to silica uptake or release reactions was observed with increasing depth in core for the three sediment cores investigated; this indicates that uptake sites are not saturated, and silica is available for dissolution for a long time after deposition. 相似文献
14.
The interaction of Mn2+ with the surface of calcite in aqueous solutions is complex. In dilute solutions the Mn2+ is rapidly absorbed, MnCO33 nucleates on the calcite surface and then grows by a first order reaction with respect to the initial Mn2+ concentration. At higher ionic strengths in NaCl solutions, the rate of these processes is slower, but the same general pattern persists. In solutions containing Mg2+, at the concentration of seawater and in seawater, the nucleation phase of the uptake process does not appear to occur. The long-term uptake rate of Mn2+ on the surface of calcite in seawater is first order with respect to the dissolved Mn2+ concentration. The rate constant is over three orders of magnitude smaller than that found in dilute Mg2+-free solutions. A probable explanation for the slower growth rate in seawater is that MnCO3 is not nucleated on the calcite surface due to the presence of high Mg2+ concentrations. The Mg2+, through site competition, prevents enough Mn2+ from being adsorbed to reach a critical concentration for MnCO3 nucleation. This behavior is similar to that found for orthophosphate with calcite surfaces in dilute solutions and seawater. It indicates that rhodochrosite cannot nucleate in carbonate-rich recent sediments unless the Mg2+ concentration is lowered below that of seawater.Measurements of the solubility of rhodochrosite in seawater gave results from an undersaturation approach to equilibrium in excellent agreement with those found in previous studies in dilute solutions. When equilibrium was approached from supersaturation, approximately fifty times more calcium was precipitated than Mn2+. The measured solubility was over twice that determined from undersaturation. It is possible that a Mn—calcite containing 25 to 30 mol% MnCO3 formed on the rhodochrosite from the supersaturated solutions. Consequently, it is doubtful that pure rhodochrosite controls the concentration of Mn2+ even in calcium carbonate-poor marine environments. 相似文献
15.
作者采用水化学演化图（hydrochemical facies evolution diagram,HFE-D）和海水入侵地下水质量指数（GQISWI）对山东威海文登区地下水的化学演化和海水入侵情况进行了分析。Piper图的结果表明文登区从北到南地下水的化学组成分别是Ca-HCO3、Ca-Mg-Cl、Na-Cl。HFE-D表明沿海地区的含水层中海水占主导地位,并且地下淡水补给不足,无明显淡化趋势;内陆地区含水层中的淡水多数处于海水侵入期,有咸化趋势。运用GQISWI、地理信息系统和空间插值法结合,得到了文登区浅层海水入侵现状图。另外,作者考虑渗透系数对离子浓度的影响,运用反距离加权插值算法并结合渗透系数分析了文登区浅层地下水海水入侵程度。结果表明文登沿海地区已经发生了极其严重的海水入侵现象,结合HFED可知咸水有向内陆继续扩散的趋势。研究结果对文登区地下水资源的利用和海水入侵的防治具有重要意义。另外本文是HFE-D和GQISWI在国内文献中的首次应用,为国内其他地区的海水入侵评价提供了参考。 相似文献
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模拟海洋大气腐蚀试验方法的研究 总被引：1，自引：0，他引：1
本文以不同浓度的天然海水、人造海水和氯化钠溶液对五种钢材进行了试验,结果表明,采用天然海水喷雾模拟性和试验重现性为最佳,腐蚀形态与海洋环境腐蚀结果基本一致· 相似文献
18.
Hasan Firat Pulat 《Marine Georesources & Geotechnology》2013,31(5):466-472
The present study examines the suction characteristics and swelling behavior of clayey soils when exposed to natural seawater with respect to distilled water. The effects of saline waters on the engineering behavior of soils need to be determined since the salinity of the pore fluid of soils near coastal areas increases continuously. Six clayey soil samples with different mineralogy and characteristics were gathered and tested to determine the suction and swelling characteristics in the presence of natural seawater and distilled water. The results show that the total suction values of the samples are higher in the presence of seawater than in distilled water. The samples with high swelling potential have lower matric suction values than nonswelling soils. Moreover, in contrast to swelling-type soils, the matric suction values of the nonswelling soils remain similar in the presence both distilled water and seawater. The modified free swell index (MFSI) of the samples is well correlated with the liquid limit (LL), plasticity index (PI), and cation exchange capacity (CEC) in distilled water. However, coefficients of determination decreased in the presence of seawater. Also, there is no significant correlation existing between total and matric suction values and the MFSI values of the samples. 相似文献
19.
An intercomparison study of voltammetric and atomic absorption spectrometric methods for determining cadmium, lead and copper in seawater samples was conducted. The voltammetric approach utilizes differential pulse anodic stripping voltammetry using a rotating, glassy carbon, mercury film electrode under conditions developed to minimize contamination sources and to enhance sensitivity for seawater matrices. The atomic absorption approach involves a concentration step using either an organic solvent extraction of metal dithiocarbamate chelates or a Chelex-100 column with detection by graphite furnace atomic absorption spectrometry. Similar and consistent results were obtained using both methods for the three trace metals studied on a wide range of natural seawater samples. Both methods are comparable in sensitivity for cadmium and copper, however the voltammetric method is better suited for the analysis of lead in seawater because of its enhanced sensitivity and low blank. An advantage of the voltammetric approach is its amenability towards real-time shipboard analysis. 相似文献
20.
Li Jinxia 《海洋学报(英文版)》1989,8(3):401-408
Isotope dilution mass spectrometry (IDMS) and ultra-clean room approach are successfully used in the determination of Cd, Pb and Zn in seawater and the sample pretreatment of analysis. The precision in the determination of Cd, Pb and Zn in seawater is better than±3% and the limits of detection are 6×10-12, 6×10-11 and 2.4×10-10 respectively. The effects of sample pretreatment such as filtration and acidification on the results of determination of Cd- Pb and Zn in seawater are disscussed. 相似文献