陆架区沉积物中重金属研究的基本方法及其应用

陆架区沉积物接纳了来自河流、大气、生物、火山等各种途径的颗粒物，是重金属汇集的场所，反映了一定时间内的环境变化特征。本文分析了沉积物中重金属的来源，探讨了沉积物中重金属研究的基本方法：总量分析方法、元素赋存形态、归一化法及重金属的生物毒性等。并探讨了目前沉积物中重金属研究仍存在的问题。     

烟台近岸典型生态区沉积物重金属形态分布及其污染状况

运用Tessier连续提取法,对烟台海岸带3个典型生态敏感区表层沉积物重金属Cr、Cu、Cd、Pb、Zn、Ni的形态分布和污染状况进行了分析研究。结果表明,研究区域中河口区与排污口区重金属Cr、Cu、Cd、Zn和Ni的含量较高,尤其是Cd污染严重。养殖区基本符合海洋沉积物质量第1类标准;重金属Cr、Cu、Pb、Zn和N...     

长江口及邻近海域夏季表层沉积物中重金属等的分布、来源与沉积物环境质量

通过现场调查研究报道了长江口及邻近海域表层沉积物中重金属、有机碳、石油类、硫化物以及氮磷的分布、来源以及沉积物环境质量.结果显示,长江口及邻近海域表层沉积物中重金属、有机碳、石油类、硫化物以及氮磷的分布很不均匀,除硫化物外,重金属、有机碳、石油类以及氮磷基本呈现长江口和杭州湾东北近岸的上海外海出现高值,其他区域浓度较低...     

长岛海域沉积物污染物时空分布特征及生态风险评价

文章依据2018年8月长岛海域表层海洋沉积物调查数据，分析了表层沉积物主要污染物的时空分布特征及主要来源，通过单因子和潜在生态风险指数法评价了沉积物中各种元素的污染程度和潜在的生态风险。结果显示，长岛表层沉积物各污染物的单因子指数P均值由高到低依次排列为：As、Cr、Cu、Cd、Zn、Pb、有机碳、石油类、硫化物、Hg，重金属指标污染情况较理化指标严重；全部站位综合潜在生态风险指数RI＜105，属低生态风险；Cd对综合潜在生态风险指数的贡献率为47.0%，为主要潜在生态风险因子。长岛海域表层沉积物中重金属污染元素的主要来源包括：①大气沉降、海上交通排污带来的重金属污染；②周边区域的养殖面源、生活污水污染等带来的重金属污染；③煤矿和金矿等矿产资源开发等重金属污染。     

深圳湾表层沉积物中重金属的分布

本文在1986年4月至1989年1月间深圳湾12次环境调查资料的基础上,报道了6个调查站的表层沉积物中6种重金属元素(Cu、Pb、Zn、Cd、Cr、N(?))的含量及其时空分布特征,以及表层沉积物中重金属的含量与环境因子的相关分析结果,并且对该湾表层沉积物中重金属的污染程度作出了评价,为今后深圳湾环境质量综合评价提供了背景资料。     

长江口湿地沉积物中的氮、磷与重金属

研究了总氮NT、总磷Pt、重金属Cu,Zn,Pb和Cd在崇明东滩湿地沉积物中的分布与累积特征。结果表明,NT和重金属表现为：芦苇带〉互花米草带〉海三棱镳草带〉光滩,即从光滩至芦苇带,从南部至北部,NT和重金属的质量分数呈现逐步增加的趋势。由于高潮带以细颗粒为主,有机质含量较高,因此NT和重金属表现出相应的富集;而沉积物PT在各个湖带呈均匀分布,这主要与沉积物中磷的化学形态组成有关。与上海南岸潮滩湿地和世界其他河口湿地相比,东滩湿地沉积物中重金属的质量分数相对较低,表明它是一块保存较为完好未受到污染的天然湿地,这主要与长江径流对污染物的稀释作用有关。     

钦州湾-北海近岸水域表层沉积物重金属分布特征

在调查现有沉积物分布和地貌背景下,进一步研究了钦州湾-北海近岸水域表层沉积物重金属与有机质分布特征,进行了含量对比与变化模拟,分析了重金属与有机质的关系。结果表明,研究区重金属平均含量在0.039×10-6～47.1×10-6之间,有机质平均含量0.85%,空间变异性均比较大,犀牛脚至三娘湾近岸、北海港区是多种重金属的聚集之处,空间梯度往往也比较大;不同类型沉积物中,重金属向细颗粒聚集效应明显,含量最大增幅为153%,平均含量在TY沉积物中达到最高,重金属与有机质相关性总体也较好,且Zn、Pb、As、Cu、Cd、Hg含量依次以对数方式递减;重金属含量分布与地貌类型也有一定关系,沉积了较多细颗粒物质的水下斜坡,重金属含量普遍要高;从三项典型的重金属Cu、Pb、Zn垂直分布来看,在1.0m左右开始明显增加,应与气候变化与人类影响有关;进行了沉积物质量评价,得出重金属质量指数在0.02～1.31之间,Cu、Pb、Zn、Cd、Hg和有机质均为一类沉积物,As出现了二类沉积物,与前人评价结果一致。     

莱州湾滨海湿地沉积物重金属的空间分布

通过研究莱州湾河口区滨海湿地沉积物重金属Pb,Zn,Cd,Cu的含量变化,分析表层沉积物及柱状沉积物,以期了解莱州湾河口区滨海湿地重金属含量的区域性变化,并从柱状沉积物剖面了解沉积物重金属累积的历史变化。研究结果表明,莱州湾河口区与邻近海域沉积物重金属含量在空间分布上与垂直分布上均呈现一定幅度的变化,且高浓度重金属显示区域内重金属呈现污染状况;在沉积物柱状剖面中,发现重金属含量在上层有大幅度增加之现象。另外,利用围隔式生态实验装置研究了该滨海湿地区域污染沉积物中重金属Pb,Zn,Cd,Cu在海水环境中的行为。结果表明,海水中的还原环境能抑制污染沉积物中重金属的释放,有助于体系中原有的重金属清除出水,而低生产力条件下,Pb,Zn表现出释放行为;高生产力和高悬浮物含量条件下,Pb和Zn表现出先释放后迁移,而Cd和Cu则呈现出相反的现象。     

山东丁字湾表层沉积物重金属分布及污染评价

通过对丁字湾海域126个表层沉积物重金属(Hg、Cu、Pb、Zn、Cd、Cr、As、Ni)含量的测定及分析,采用潜在生态危害指数法、内梅罗指数法、地质累计指数法等多种评价方法,对研究区海域环境进行评价。结果表明,丁字湾海域表层沉积物中重金属含量主要集中在丁字湾湾口周边海域,Hg、Cd、As、Pb、Cu、Cr、Zn平均含量分别为0.02、0.08、8.38、15.31、11.49、60.96、46.42μg/g。利用不同的评价方法,可以看出丁字湾海域表层沉积物重金属元素总体呈未污染—轻微污染的现状,这与区内砂质沉积物广泛分布以及不活跃的人类活动密不可分。     

中国海湾沉积物重金属比较分析

随着沿海城市工业、养殖业及船舶运输业的发展,大量的重金属进入到海湾并迁移到沉积物中,海湾沉积物重金属污染已经成为一项突出的海洋环境问题。重金属污染不仅会对海洋沉积环境造成严重的破坏,还会随着食物链富集并危害人类健康。文章比较分析了中国海湾沉积物重金属的含量、时空分布特征、赋存形态、来源以及污染评价,以期全面了解海湾沉积物重金属污染现状与发展趋势,为海湾重金属污染防治及生态修复提供方向。     

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.     

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.     

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.     

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.