海水的氧化还原电位

天然海水中含有O、C、N、S、Mn、Fe、Cr、I和H等元素的不同价态的单质,离子和化合物。这些变价元素在海洋中都可能存有与其几种不同价态相应的氧化还原反应。     

山东半岛南部近海铬的形态和分布

本文采用无火焰原子吸收分光光度法测定海水不同形态的铬。研究表明:山东半岛南部近海颗粒铬对总铬的比率在60%以上,是铬存在的主要形态;六价铬对总铬比率低于3%,是最次要的形态;三价铬对总溶解铬的比率在80%以上,所以三价铬在溶解态中占主要形态。铬在该海域的分布特征是:丁字湾口为高值区,崂山湾为低值区。 -     

渤海湾海水中铬的形态

本研究测定了渤海湾海水中总溶解铬、Cr(Ⅳ)、Cr(Ⅲ)、颗粒铬和气溶胶中铬,分析了渤海湾海水中Cr(Ⅳ)、总溶解铬、总铬和颗粒铬的分布趋势,以及Cr(Ⅲ)的分布情况。研究表明,河流排污控制着渤海湾铬的分布,渤海湾河流排出有机物主要是与Cr(Ⅲ)产生吸附、络合作用,这是固-液界面交换的机制之一,形态研究表明,颗粒铬是渤海湾铬的主要存在形式,而Cr(Ⅲ)又是价态铬的主要形态,渤海湾Cr(Ⅳ)含量很低,说明海水中铬处在热力学不平衡状态。     

海洋环境地球化学 Ⅰ.海水中铬的存在形态及其在海水—底质间相互交换研究

铬是几个有毒害的主要重金属之一,在水体中的价态不同,其毒性和迁移能力也不一样。饮用水和渔业用水标准规定三价铬不得超过500ppb,六价铬不超过50ppb,而铬又是排入胶州湾的工业废水中数量最大的污染物。因此,查明含铬污水进入胶州湾后,铬在海水中的存在形态、价态及其随悬浮颗粒向海底转移以及污染底质中的铬在海水中的溶出     

海洋细菌作用下海水中铬化学形态的转化

于外加Cr(Ⅳ)和Cr(Ⅲ)的天然海水中接种海洋细菌,充氧条件下培养。在细菌对数生长期,大部分Cr(Ⅳ)被还原为Cr(Ⅲ)继而转化为有机铬。在稳定期,有机铬为溶解铬的主要形态,在无菌控制实验中,Cr(Ⅳ)和Cr(Ⅲ)浓度基本不随培养时间变化。说明在没有海洋细菌活动参与下,水中铬形态转化难以进行。实验结果为天然海水中溶解态铬的热力学不平衡状态提供部分可能的解释。     

海水中磷氮不同形态的同时测定

采用过硫酸钾-硼酸-氢氧化钠混合试剂作为氧化剂,同时测定海水中总磷、氮和总溶解态磷、氮,从而建立了海水中磷、氮不同形态的分析流程及步骤。总磷、总溶解态磷浓度为0.35～1.09μmol/dm3时,相对标准偏差小于6.6%;总氮、总溶解态氮浓度为11.8～54.8μmol/dm3时,相对标准偏差小于5.6%。总磷、总溶解态磷和总氮、总溶解态氮的回收率分别为95.0%～106.0%和94.0%～106.0%。本文的分析方法可用于对近岸海水及河口水中磷、氮不同形态的同时测定。     

耐海水腐蚀10CrMoAl低合金钢的研究

由于海水对金属的腐蚀性,对海水输水管道及各种海水冷却器的使用造成严重威胁,极需研制一种成本低、生产工艺简单而又耐海水腐蚀的低合金钢。达方面研究国外已有报道。他们研制的低合金钢是以铬为主添加合金元素的铬-铝和铬-钼型钢,含铬量约在2%以上。这类钢在海水中耐蚀性一般为碳钢     

福建东山湾海水中溶解态重金属平面分布及影响因素初探

根据2011年5月(春)和8月(夏)福建省东山湾海洋生态环境的调查数据,研究了海水中溶解态重金属(Cu、Pb、Zn、Cd和Cr_(T))的平面分布特征及其影响机制,结果表明:(1)海水中溶解态重金属含量平面分布呈在西南部形成“点源汇集状高值区”且自西向东逐渐递减趋势;除锌元素外,重金属含量季节变化趋势均为夏季>春季。(2)20世纪80年代以来,除海水中Zn含量逐年增加外,Cu、Pb和Cd等污染物含量的变化趋势基本符合倒“U”形环境库兹涅茨曲线。(3)采用数理统计软件分析各溶解态重金属含量之间相关性,春季海水中重金属含量除总铬外,其余4种重金属含量两两呈显著正相关;夏季海水中重金属含量仅Cu-Cd和Cd-Cr_(T)相关性较好。(4)温度、盐度、pH值、化学需氧量、溶解氧、营养盐和生物效应是海水中溶解态重金属含量变化重要的影响因子。     

石墨炉原子吸收法测定海洋沉积物中铬

一、前言 目前测定沉积物样品中的铬有比色法、气相色谱法、火焰原子吸收法。这些方法中有的操作比较麻烦,有的灵敏度偏低,而且都只能测定沉积物中总铬。石墨炉原子吸收法测定海洋沉积物中的铬,也是测定总铬,而且根据“规范”要求只测对生物有效态部分。本试验在测定沉积物总铬方法的基础上作了改进,对用Mg(NO_3)_2和抗坏血酸作基体改进剂作     

海水中痕量铬的极谱催化波研究

本文研究了海水中痕量铬的极谱催化波及其机理,在乙二胺-NaNO₂-EDTA底液体系中,可得到清晰、灵敏而稳定的极谱催化波,其导数示波极谱上的峰电位为-1.7伏(SCE),检测浓度可低达1.5×10-9M,天然海水试样不必经过分离富集手续即可直接测定,方法精密度好,准确度高,变异系数为5%,回收率相对误差为10%,研究表明为具有吸附性质的氢催化波.     

Uptake and release of 51Cr(VI) and 51cr(III) by Barnacles (Balanus sp)

Barnacles (Balanus sp) were used to examine the uptake and release of chromium-51 added to sea water in two different valence states, ⁵¹Cr(VI) and ⁵¹Cr(III).Hexavalent chromium-51 (sodium chromate) forms a true ionic solution in filtered sea water and barnacles were able to accumulate chronium in soft tissues 543 times the levels found in sea water. The experiment showed that incorporated Cr(VI), is released to the water in such way that only 20%% of maximum uptake was lost by the organisms after 26 days. Addition of the hexavalent form to non filtered sea water showed that 2% of the total radioactivity was attached to the suspended particles. Here again chromium is mainly concentrated in soft tissues, showing a concentration factor of 380 related to total chromium available in aquarium (solution + suspended particles). From the total radioactivity incorporated by the organisms, 20 % was released after 56 days in the clearance experiment.Chromium, as trivalent chromic chloride, when added to sea water precipitates and is quickly removed from the water by the filter activity of the barnacles. Unlike the hexavalent form, trivalent chromium is not concentrated in soft tissues of the barnacles and is quickly released to the water through the organisms digestive system.     

Direct determination of barium in Sea water by inductively coupled plasma emission spectrometry

A method for the determination of barium in sea water was investigated using inductively coupled plasma emission spectrometry, and sea water samples from the Japan Sea and the Pacific Ocean were directly analyzed by this method. Artificial sea water was used to prepare matrix matched standard solutions to overcome the problem of physical interference. The detection limit (signal/noise ratio=2) for barium in deionized and distilled water was 0.08µg l^?1 and in sea water, 0.12µg l^?1. The reproducibilities in the purified water and in the sea water at the 10µg l^?1 level were 0.7% a#FFFFFFnd 0.5%, respectively. The barium concentration in both the Japan Sea and the Pacific Ocean increased with depth and ranged between 5.5–10.0µg l^?1 and 4.1–18.4µg l^?1, respectively.     

Effects of hexavalent chromium on early development of the bay scallop Argopecten irradians Lamarck

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DETERMINATION OF RESIDUAL MALATHION IN NATURAL WATER

A method for determination of malathion in natural water by cathodic stripping voltammetry using mercury film electrode is suggested in this paper. The method is based on the quantitativeformation of group generated by malathion as a result of elimination reaction inthe ethanol solution of sodium hydroxide. The group is similar to sulphide in electrochemical properties, and can be determined by cathodic stripping voltammetry. Interference from inorganic sulphide is prevented by the addition of Hg (NO3)2. This method has been applied to the determination of residual malathion in natural water (e. g. the sea, rivers, lakes, etc.). The waveheight is directly proportional to the malathion concentration within the range 5×10-9 - 1×10-7 mol/L. The method is simple and rapid, and the results of water sample determination is quite in accord with those of Gas Chromatograph.     

Isotope dilution measurement of inorganic chromium(III) and total chromium in seawater

A reproducible, low-blank, isotope-dilution technique for the determination of inorganic Cr(III) and total dissolved chromium in seawater has been developed. Analysis of coastal water from Brittany, France, confirms that inorganic Cr(III) exists in excess of the thermodynamic equilibrium value calculated from the model of Elderfield (1970). A vertical profile of total chromium at 13°N on the East Pacific Rise confirms the general features of Cr behaviour: slight depletion at the surface (Cr = 2.0 nmol l⁻¹ compared to 2.6 nmol l⁻¹ below 1000 m) and bottom excess possibly due to Cr (III) release from sediments (up to 15.8 nmol l⁻¹). A maximum enrichment of six times the average seawater value is obtained in hydrothermal waters. The chromium content of metalliferous sediments is mainly due to scavenging from the water column; input of chromium into the ocean through hydrothermalism is negligible.     

A new fluorometric method of analysis of selenium in sea water

A new method of determination of selenium and separation of Se(IV) and Se(VI) in sea water is described. The selenium is determined by fluorometric method using Se-DAN complex in cyclohexane media. Prior to the fluorometric determination, Se(IV) is separated from sea water by means of Se(IV)-DDTC complex which is adsorbed on the macroreticular resin. As to the separation of the total selenium from sea water sample, the reduction and coprecipitation method is used. Se(VI) is determined with the same method as used for the total selenium after the separation of Se(IV). The average recoveries are 92.5±1.3% for Se(IV) and 97.4±0.9% for Se. The standard deviation of analytical results is below 10%.     

Determination of experimentally enriched15N in nitrate nitrogen based on an improved method of azo dye formation

A method has been developed for determination of¹⁵N isotope ratio in nitrate nitrogen, which is a major analytical step in tracer experiments for studies of nitrate metabolism in the marine environment. The method is based on diazotization of nitrite with sulfanilic acid following reduction of nitrate to nitrite by a cadmium-copper column. The diazonium compound is then subject to the azo coupling reaction with 2-naphthol, and the azo dye formed is extracted by a solid phase extraction column. The dye eluted from the column is collected, and total nitrogen and¹⁵N content of the dye are determined by mass spectrometry. Sulfanilic acid can also remove preexisting nitrite by heating the sample under acidic conditions before passing through the cadmium-copper reduction column. The average recovery of nitrate nitrogen was 86%. A procedure for reducing the background nitrogen that derives from the analytical operations has been developed; background nitrogen was limited to about 0.25 μg-atomN. The variation in the background nitrogen levels reflects the range of error in¹⁵N determination of nitrate nitrogen by this method. Application of the present method to a¹⁵NO₃ ⁻ isotope dilution experiment for determination of nitrification rate in sea water is demonstrated.     

STUDY OF SPECIES OF DISSOLVED CHROMIUM IN SEAWATER

A new and simple analytical procedure has been developed for the determination of the chemical species of dissolved chromium in seawater and used to monitor the water pollution in the sea area of Xiamen. The data obtained by statistical treatment coincides with the environment situation in that sea area.     

Rapid, high-precision potentiometric titration of alkalinity in ocean and sediment pore waters

A system for rapid, high precision potentiometric determination of alkalinity in sea water and sediment pore water is presented. Two titration units were used: a 40 ml unit for seawater and a small volume unit for sediment pore water. Titration time was normally less than 10 minutes per sample, including sample exchange. With a 40 ml sample volume, the relative standard deviation of the alkalinity obtained in the laboratory was 0.05% and at sea 0.1 %. The small-volume system (0.5–1.5 ml) gave a precision of 0.07%. Five titration points, in two groups after the second equivalence point, were used to evaluate the equivalence volume. Results from equilibrium calculations and computer simulated alkalinity titrations show that it was possible to use a non-modified Gran function [(V₀ +v)^*10^(E/Z)] and still achieve good accuracy and precision.     

南极洲赖特谷万达盐湖中铬的垂直迁移

南极洲万达湖湖水上部为氧化环境,铬浓度较低,Cr~(6+)占主导地位,主要以CrO_4~(2-)形式存在;下部为还原环境,铬浓度高,Cr~(3+)为主,以Cr(OH)_2~+和Cr(OH)~(2+)形式存在。湖水中锰、铁的氧化物及氢氧化物颗粒对铬离子的吸附和释放过程,控制了湖水铬浓度的变化。