海水中金属设施防腐、防海洋生物污损及检测技术研究

随着工业的高速发展和人口的急剧増加及环境污染的加剧，淡水资源危机已引起世界各国的普遍关注。据统计，城市用水中工业用水通常占80%左右，而工业用水中有80%是工业冷却用水，所以开发利用海水代替淡水直接作冷却用水是节约淡水的重要途径。海水直流冷却系统具有深海取水温度低且恒定、冷却效果好和系统管理简单等优点，但必须具备以下条件:(1)管道系统防除生物附着污损；(2)管道系统的防结垢；(3)金属腐蚀与防护。多年来有关方面虽然相应地采取了许多措施，但由于主设备通常需常年连续运行，因而往往出现在某段时间、某些部位上效果降低与失效。现行的对海水环境中生物附着腐蚀检测主要采取取样离位分析方法，其结果与实际状态有差异，且生过程中许多重要部位，如海上平台、浮码头、船舶、海滨电厂、化工厂的海水冷却系统和海水管路的管道内、及死角区都很难取样，必要时只有定期停机检查(侯保荣1998； Efird，1976；吉井彻，1967)，造成很大的经济损失。 防止海水环境中的金属设施遭受海水腐蚀和海洋生物污损的方法很多，通常采用阴极保护、防污涂料、电解海水或电解重金属等方法，但这些方法的缺点是：(1)阴极保护能防止金属腐蚀而不能防止海洋生物附着；(2)防污涂料涂刷一次，只能用3-5年，对许多一次性埋入水中的管件无法进行二次补涂，防污涂料所释放出的毒物将长期污染环境；(3)利用电解海水或电解重金属所产生的次氯酸钠或重金属离子来进行防污，即电解防污效果明显，但对金属防腐的作用不大(侯保荣，1999;陈光章，1994;马土德，1996)。总结前人的经验，经过多年的研究，我们利用电化学方法研制出既能防止金属海水腐蚀又能防生物附着的双防与检测新技术系统装置，已通过实海实验，取得了良好的效果。     

盐度变化对铝牺牲阳极保护效果的影响

为研究河流入海口处盐度周期变化时铝牺牲阳极对钢结构的保护效果,测试对比了盐度固定与盐度循环条件下Q235钢有无阳极保护时的腐蚀失重和电位变化、铝牺牲阳极的电流效率.结果表明盐度循环会造成Q235钢的严重腐蚀,盐度差越大腐蚀越严重,甚至可能超过天然海水的腐蚀程度;在盐度循环条件下铝牺牲阳极对Q235钢具有良好的保护效果,...     

合金元素对铝基牺牲阳极性能影响的研究

于1988年5月在实验室内，利用正交试验的配比方法研究不同含量的Zn，In，Bi，Ti对Al基牺牲阳极在海水中的性能的影响。通过对牺牲阳极的电流效率、工作电位及腐蚀产物附着情况等项性能的正交计算，得出结论：Zn含量为4．5％，In为0．03％，Bi为0．01％，以及Ti为0％时Al基牺牲阳极的各项性能都呈现为最佳值。     

钛/碳钢在海水中电偶腐蚀的研究

研究了国产纯钛和碳钢Q235在青岛近海海水中的电偶腐蚀情况。测定这两种金属材料的自然腐蚀电位和失重速率；用IM6e电化学工作站测定两种金属材料在海水中的稳态极化曲线，研究其极化性能；测定了碳钢与钛组成不同面积比、不同温度、不同海水流速时电偶电流的大小、方向，电偶电位，以及不同面积比时阳极的失重速率。结果表明，阳极的腐蚀速率随阴／阳极面积比、环境温度、海水流速的增大而增加，且阳极腐蚀速率随阴／阳极面积比的增大趋于极限值。     

海洋工程用铝基牺牲阳极发展概况

阴极保护是一种重要的腐蚀防护方法,它分为外加电流保护和牺牲阳极保护。其中 ,用牺牲阳极保护金属构件是一种简单易行 ,投资较少的阴极保护方法。因此 ,在船舶、码头、海洋平台及其他海上大型钢结构的保护上 ,得到了广泛的应用［３］。阴极保护用的牺牲阳极材料有铝、镁、锌三大系列。张经磊１９８６年指出 ,与镁基、锌基牺牲阳极相比 ,铝阳极的最突出优点是单位重量的输出电量大 ,是锌阳极的３．６倍 ,镁阳极的１．３倍 ;铝资源充足 ,价格便宜 ,重量轻 ;工作电位足够负 ,发生电流量大 ,寿命长 ,在海水和含Ｃｌ-的环境中应用性能良好。而…     

海水管道内壁阴极保护——牺牲阳极法

作者曾介绍过海水管道内壁外加电流阴极保护法。本文主要是介绍牺牲阳极保护法。该法是借助于电位更负的金属(牺牲阳极)本身的消耗,放出电流来保护管道。如图1所示,牺牲阳极“1”在海水中溶解,放出电流,通过海水进入钢管,使管壁电位负移至保护电位,从而钢管得到保护。     

海水冷却技术

城市用水中约 5 0 %是工业冷却水。海水代替淡水作为工业冷却用水——海水冷却 ,是解决我国沿海城市和地区淡水资源危机问题的重要途径之一。海水冷却技术包括海水直流冷却技术和海水循环冷却技术 ,目前我国基本具备了具有自主知识产权的海水(直流、循环 )冷却关键技术。寻求政府在资金、政策等方面的大力支持 ,加强有关行业、院所、企业的“强强联合”,适时借鉴国外先进的海水冷却塔技术 ,加快产业化技术示范 ,是推进海水循环冷却技术快速发展的必由之路     

高效铝合金牺牲阳极的研究

在铝中添加合金元素Zn,Mg,In,Ga,Ca,利用正交设计方法,研制出一种高效的铝合金牺牲阳极,它在海水中的电流效率达95.6％,电位为-1.09V(SCE)。并研究了合金元素In,Ga,Ca对铝合金电化学性能的影响及阳极活化机理。     

海水盐度对铝阳极电化学性能影响的研究

于１９９３年７月－１９９３年９月，利用青岛海滨的新鲜海水配制不同盐度（３０－５）的海水样品。采用ＧＢ４９４８－８５规定的方法研究海水盐度的变化对铝基牺牲性阳极电化学性能的影响。结果表明，海水盐度在３０－１０的范围内变化时对铝阳极的电化学性能无明显影响；当海水盐度降至５后，对阳极的开路电位，闭路电位及电流效率等产生明显影响，使性能指标低于国标要求的范围。     

实际海洋条件下铝基牺牲阳极性能研究

铝基牺牲阳极是防止钢铁结构(尤其是海水中的)腐蚀的有效材料，它比镁基、锌基阳极具有更多的优越性，在某些方面也比外加电流阴极保护法为好。所以近十几年来，在国外有了很大的发展。在我国，科学工作者也做了不少研究，并已开始应用。但是，有关阳极的各项性能参数，过去大部分是在实验室条件下测定的，至于在海洋工程实际应用条件下的各项参数及其与海水物理化学性质之间的关系，则尚未见报道。本工作是在室内研究的基础上进一步在实际海洋条件下进行的研究。通过此研究，弄清了主要合金成分和有关海水物理化学因素对阳极性能的影响以及工程设计中应注意的问题。     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

A Review of Some Environmental Issues Affecting Marine Mining

This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested.     

Increased Particle Fluxes at the INDEX Site Attributable to Simulated Benthic Disturbance

Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement.     

Determination of In Situ Sediment Shear Strength from Advanced Piston Corer Pullout Forces

The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.