Rapid collection of iron hydroxide for determination of Th isotopes in seawater

This work introduces a novel method of recovery of iron hydroxide using a DIAION CR-20 chelating resin column to determine Th isotopes in seawater with a sector field (SF) inductively coupled plasma mass spectrometer (ICP-MS). Thorium isotopes in seawater were co-precipitated with iron hydroxide, and this precipitate was sent to chelating resin column. Ferric ions in the iron hydroxide were bonded to functional groups of the chelating resin directly, resulting in a pH increase of the effluent by release of hydroxide ion from the iron hydroxide. The co-precipitated thorium isotopes were quantitatively collected within the column, which indicated that thorium was retained on the iron hydroxide remaining on the chelating column. The chelating column quantitatively collected ²³²Th with iron hydroxide in seawater at flow rates of 20–25 mL min⁻¹. Based on this flow rate, a 5 L sample was processed within 3–4 h. The >20 h aging of iron hydroxide tends to reduce the recovery of ²³²Th. The rapid collection method was successfully applied to the determination of ²³⁰Th and ²³²Th in open-ocean seawater samples.     

A sensitive flow-batch system for on board determination of ultra-trace ammonium in seawater: Method development and shipboard application

Combining fluorescence detection with flow analysis and solid phase extraction (SPE), a highly sensitive and automatic flow system for measurement of ultra-trace ammonium in open ocean water was established. Determination was based on fluorescence detection of a typical product of o-phthaldialdehyde and ammonium. In this study, the fluorescence reaction product could be efficiently extracted onto an SPE cartridge (HLB, hydrophilic–lipophilic balance). The extracted fluorescence compounds were rapidly eluted with ethanol and directed into a flow cell for fluorescence detection. Compared with the common used fluorescence method, the proposed one offered the benefits of improved sensitivity, reduced reagent consumption, negligible salinity effect and lower cost. Experimental parameters were optimized using a univariate experimental design. Calibration curves, ranging from 1.67 to 300 nM, were obtained with different reaction times. The recoveries were between 89.5 and 96.5%, and the detection limits in land-based and shipboard laboratories were 0.7 and 1.2 nM, respectively. The relative standard deviation was 3.5% (n = 5) for an aged seawater sample spiked with 20 nM ammonium. Compared with the analytical results obtained using the indophenol blue method coupled to a long-path liquid waveguide capillary cell, the proposed method showed good agreement. The method had been applied on board during a South China Sea cruise in August 2012. A vertical profile of ammonium in the South East Asia Time-Series (SEATS, 18° N, 116° E) station was produced. The distribution of ammonium in the surface seawater of the Qiongdong upwelling in South China Sea is also presented.     

Response of the Iron Chalcogenide Glass Membrane Ion‐Selective Electrode in a Seawater Ligand Mimetic Calibration Buffer

As a continuation of recent mechanistic studies into the influence of seawater ligands on the surface chemistry of the iron chalcogenide glass membrane ion‐selective electrode (ISE), the present study has investigated the response of the iron(III) ISE in a seawater ligand mimetic system to examine its suitability as a calibration medium for the electroanalysis of raw or natural seawater. Significantly, dip method calibrations of the ISE in a mixture of salicylate, ethylene diamine tetraacetic acid (EDTA), ethylene diamine and minor amounts of dissolved iron(III) and copper(II) yielded the expected Nernstian response of 30 mV/decade according to the known ion‐exchange/electron transfer response mechanism of this ISE. Furthermore, ideal Nernstian response of the electrode is also obtained in a continuous flow analysis (CFA) mode, noting that this provides scope for using a hydrodynamic flow regime to minimize the electrode release of iron and the concomitant detection limit of the ISE. Ultimately, repetitive CFA analyses of free iron(III) in raw or natural seawater yielded a free iron(III) level commensurate with the expected inorganic and organic speciation of iron(III) in seawater.     

海水入浸问题的数值分析

海水入浸问题的数学模型是两个耦合抛物型偏微分方程,其中一个是关于压力的流动方程,另一个是关于浓度的对流扩散方程.压力方程由标准有限元方法逼近,浓度方程则用特征有限元方法逼近.在扩散项系数半正定的情形得到逼近解的次优L2 模误差估计.     

The distribution and potential toxic effects of TBT in UK estuaries during 1986

The concentrations of butyltin compounds in seawater were measured at nine sites in the UK during 1986. In popular yachting centres concentrations of tributyltin (TBT) ranged from less than detectable ( < 1 ng dm^?3) in the winter, up to 1500 ng dm^?3 in marinas in the summer. Measurements of wastewater generated by high-pressure hosing of yachts demonstrated that even higher environmental concentrations of TBT resulted from the procedure. The results of the monitoring programme are discssed in relation to the toxicity of TBT and recent government legislative actions.     

Steady filtration problems with seawater intrusion: macro‐hybrid penalized finite element approximations

Macro‐hybrid penalized finite element approximations are studied for steady filtration problems with seawater intrusion. On the basis of nonoverlapping domain decompositions with vertical interfaces, sections of coastal aquifers are decomposed into subsystems with simpler geometries and small scales, interconnected via transmission conditions of pressure and flux continuity. Corresponding local penalized formulations are derived from the global penalized variational formulation of the two‐free boundary flow problem, with continuity transmission conditions modelled variationally in a dual sense. Then, macro‐hybrid finite element approximations are derived for the system, defined on independent subdomain grids. Parallel relaxation penalty‐duality algorithms are proposed from fixed‐point problem characterizations. Numerical experiments exemplify the macro‐hybrid penalized theory, showing a good agreement with previous primal conforming penalized finite element approximations (Comput. Methods Appl. Mech. Engng. 2000; 190 :609–624). Copyright © 2005 John Wiley & Sons, Ltd.     

基于可视化图形特征的入侵检测方法

入侵检测是保障网络安全的重要措施,网络攻击手段的多样性和隐蔽性不断增强导致入侵检测愈加困难,迫切需要研究新的入侵检测方法。结合可视化技术和k近邻分类算法,提出一种基于图形特征的入侵检测方法。采用信息增益方法对原始特征进行排序选择,并进行雷达图可视化表示,提取雷达图的图形特征构成新的数据集并送入k近邻分类器进行训练和测试。通过KDDCUP99数据集仿真实验表明,该方法不仅能直观显示攻击行为,而且获得较好的攻击检测性能,对DOS攻击的检测率可达97.9%,误报率为1.5%。     

Direct determination of uranium in seawater by laser fluorimetry

A method for estimation of uranium in seawater by using steady state laser flourimetry is described. Uranium present in seawater, in concentration of approximately 3 ng ml⁻¹ was estimated without prior separation of matrix. Quenching effect of major ions (Cl⁻, Na⁺, SO₄⁻, Mg⁺, Ca⁺, K⁺, HCO₃⁻, Br⁻) present in seawater on fluorescence intensity of uranium was studied. The concentration of phosphoric acid required for maximum enhancement of fluorescence intensity was optimized and was found to be 5%. Similarly the volume of concentrated nitric acid required to eliminate the quenching effect of chloride and bromide completely from 5 ml of seawater were optimized and was found to be 3 ml. A simple equation was derived using steady state fluorescence correction method and was used for calculation of uranium concentration in seawater samples. The method has a precesion of 1% (1 s, n = 3). The values obtained from laser fluorimetry were validated by analyzing the same samples by linear sweep adsorptive stripping voltametry (LSASV) of the uranium-chloranilic acid (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone) complex. Both the values are well in agreement.     

Speciation of arsenic using capillary gas chromatography with atomic emission detection

A gas chromatography method with atomic emission detection (GC-AED) for the determination of dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and inorganic arsenic was optimized. The analytes were derivatized in the sample solutions with methyl thioglycolate (TGM) and the products were extracted into cyclohexane before an aliquot of this organic phase was directly injected into the chromatograph. The procedure was applied to the analysis of seawaters, wines, beers and infant foods, the last requiring an additional enzymatic reaction prior to analyte derivatization. Detection limits in seawaters and beverages were 0.05, 0.15 and 0.8 ng mL⁻¹ for DMA, MMA and inorganic arsenic, respectively. In infant foods the detection limits were 1, 10 and 25 ng g⁻¹ for DMA, MMA and inorganic arsenic, respectively. Inorganic arsenic was detected in some of the seawater samples and three of the wines analyzed at concentration levels in the range 1-40 ng mL⁻¹, and DMA in several of the infant foods in the range 20-80 ng g⁻¹. The method was validated by analyzing a certified reference material and by recovery studies. All the samples were also analyzed by hydride generation and atomic fluorescence spectrometry (HG-AFS), which provided data for the total arsenic content.     

Inorganic adsorbent containing polymeric membrane reservoir for the recovery of lithium from seawater

Polymeric membrane reservoir system which contains inorganic ion-exchange adsorbent inside is suggested for the recovery of lithium from natural seawater. Manganese oxide particles having high selectivity toward lithium adsorption was used as inorganic ion-exchange adsorbent. Polymeric membrane reservoir was prepared from non-woven fabric, polysulfone (PSf) membrane, PSf/non-woven fabric composite membrane, and Kimtex^®. Leakage of the inorganic particles and morphology of the membrane were investigated and availability as membrane reservoir for the lithium recovery was evaluated by the lithium desorption from Li_1.33Mn_1.67O₄ in the membrane reservoir. From this study, ease of water diffusion to the reservoir was the most important factor for the reservoir system to be applied to lithium recovery from seawater and membrane reservoir prepared by Kimtex^® showed the best result. The proposed system has the advantage of direct application in the sea without using pressurized flow system.