东海陆架HY126EA1孔沉积物稀土元素地球化学

HY126EA1孔沉积物稀土元素总量(∑REE)变化范围不大,分布范围为123.45～187.12μg/g,平均值为164.07μg/g,接近于全球沉积物平均稀土元素含量(150～300μg/g)的下限,高于黄海、东海表层沉积物的平均含量,低于渤海、南海表层沉积物的平均含量.各类沉积物以及不同时期同类沉积物的稀土元素标准化曲线的变化趋势非常一致,表明这些沉积物具有相同的物源区.∑REE,δEu和δCe在垂向上具有明显变化,反映了沉积物源区气候环境的阶段性变化.     

南黄海中部MIS6期以来沉积物稀土元素组成及其物源指示意义

对南黄海中部SYSC-1孔0～30 m段岩芯稀土元素(REE)和粒度进行分析,结合年代测定,研究了沉积物REE组成特征及其影响因素,并对其物质来源变化进行了探讨。结果表明,∑REE含量为111.66～231.12μg/g,垂向分布变化较大,均值与中国黄土∑REE均值比较接近。∑REE与粒度变化有一定的相关性,但(La/Yb)_N、(Gd/Yb)_N和(δEu)_N等参数受粒级影响较小。稀土元素分异参数有效示踪了物质来源,与周边河流对比发现,SYSC-1孔沉积物(La/Yb)_N和(δEu)_N散点图分布位置与黄河和长江较为一致,而与朝鲜半岛河流有明显不同。REE判别函数(DF)的物源区分结果表明,钻孔MIS6期经历了一次大的物源转换,沉积物由长江源(27.98～30 m)转为黄河源(24.24～27.98 m)。MIS5.5—MIS5.1期间(24.24～16.98 m)发育了浅水陆架冷水团沉积,主要是长江源细颗粒沉积物被古黄海暖流由南往北携带而来,并在冷涡区附近沉积下来。MIS5.1—...     

闽江钻孔沉积物微量元素地球化学研究

河流沉积物微量元素特征对指示沉积演化历史、沉积环境及沉积物的物质来源具有十分重要的示踪作用。闽江福州段540cm的沉积物微量元素比值(Rb/Sr和Sr/Ba)和稀土元素地球化学特征,敏锐地指示了沉积环境从河流快速转变为沼泽的突变点,同时,也清楚地指示了不同沉积环境下的物源变化。受控于闽江流域丰富的岩浆岩和稀土资源以及呈酸性的福建土壤和闽江水体,闽江钻孔沉积物REE明显高于上地壳、长江和黄河,与福建土壤最为接近。经过球状陨石和北美页岩标准化之后,闽江钻孔沉积物稀土元素分配模式呈右倾型,与长江和黄河沉积相比具有更好的轻稀土富集。δEu负异常和δCe正异常非常显著,并且与∑REE密切相关,表明它们均受到源区环境变化和搬运作用的控制。     

冲绳海槽北部15ka B.P.以来沉积物源及控制因素——稀土元素的证据

用等离子体质谱法(ICP-MS)对冲绳海槽北部Y127孔16个沉积物样品的稀土元素(REE)进行了分析。根据AMS14C测年结果,Y127孔记录了冲绳海槽约15kaB.P.以来的沉积历史。约11.1kaB.P.以来,沉积物的稀土元素总量(ΣREE)由表层102.4μg/g向下增加到136.1μg/g,平均为123.3μg/g。15—11.1ka,ΣREE在149.1—169.2μg/g之间,平均为158.6μg/g,总体趋势由上向下逐渐增加。轻、重稀土元素比值(ΣLREE/ΣHREE)在上述两个时间段中分别为8.16和9.42,其变化趋势与∑REE的完全相同。La/Sm在两个时段分别为6.70和7.15。球粒陨石标准化的结果表明,15kaB.P.以来冲绳海槽北部沉积物具有相同的配分模式,表现为LREE富集,HREE弱亏损。δEu的值在0.69—0.76之间,中等程度的负Eu异常;δCe在0.85—0.95之间,为弱的负Ce异常。经页岩标准化(NASC)后,REE配分模式曲线平坦,弱的正Eu异常和弱的负Ce异常。通过Y127孔沉积物REE特征与长江、黄河沉积物的对比研究,在15—11.1kaB.P.沉积物的REE组成基本反映了源区的物质组成特征,沉积物主要以长江物质为主,影响沉积物REE特征的主要因素是海平面变化和源区的物质特征。11.1kaB.P.以来,由于海平面上升,可能仅有少量黄河来源物质进入冲绳海槽北部,源区沉积环境和沉积物的组织,加上火山物质和生源组分的共同作用,形成了这一时期沉积物的REE特征。     

渭南黄土剖面中的稀土元素

对渭南黄土－古土壤序列中稀土元素含量和分布特征的研究结果表明：古土壤比黄土层的∑REE表现丰度高,这主要是古土壤中碳酸盐遭到强烈淋滤造成的相对富集。实际上,在成土过程中稀土元素本身有淋失。黄土层和古土壤层的稀土元素组合模式彼此相似,并且与黄河中游黄土也极相似,这反映了中国黄土的物质来自于相似的源区。黄土中稀土元素对古气候变化的响应主要表现在Ce的异常程度、各种稀土的组成和稀土总量的表现丰度上。因而,δCe、∑Ce/∑Y和∑REE也能从一个方面气候环境的变化。     

北冰洋门捷列夫海岭富锰棕色层稀土元素组成特征与来源初步分析

北冰洋深海广泛分布的富锰棕色沉积层(棕色层)是海冰、洋流、物源供给等多种因素共同作用的结果,本文基于西北冰洋门捷列夫海岭ARC07-E25岩芯沉积物稀土元素与微量元素含量、颜色反射率参数、粗颗粒组分和无机碳含量的变化特征,对该类沉积层中稀土元素的组成特征、形成机制和物质来源进行了综合分析。结果显示,沉积物稀土元素总含量(∑REE)在122.37×10?6～231.94×10?6之间变化,北美页岩标准化配分模式显示出轻微的中稀土(MREE)富集以及由La、Ce、Nd主导的较强的轻稀土(LREE)优势。沉积物中∑REE随着粗组分颗粒(如冰筏碎屑)的增多而呈现降低趋势,表明门捷列夫海脊沉积物中的稀土元素主要富集在细粒沉积物中。根据∑REE在沉积物中的变化特征将E25岩芯沉积物划分为4种地层,反映出了冰期/间冰期的气候转变过程中温暖条件下形成的棕色层与寒冷条件下形成的浅灰绿色沉积层(灰色层)的岩性旋回中稀土元素组成的差异,由于两种沉积层在形成时受到不同的底层水氧化还原环境的控制,导致了铈(Ce)元素在氧化水体中会由Ce3+氧化为Ce4+并发生沉降,而在还原水体中则由Ce4+还原为Ce3+发生溶解,这一特性使LREE含量产生较大波动,进而影响到∑REE,使之趋于在代表氧化条件的棕色层中升高而在代表还原条件的灰色层中降低。R型因子分析和物质来源判别结果显示,E25岩芯沉积物中稀土元素与亲碎屑元素(Nb、U、Th)有较好的相关性,主要来源于东西伯利亚海和新西伯利亚群岛的近岸侵蚀物质以及勒拿河物质的输入。     

北部湾海底沉积物稀土元素与影响因子关系的BP神经网络定量分析

海底沉积物中稀土元素的分布特征受多种影响因子的影响,很难定量分析。北部湾沉积物稀土元素(∑REE)与物源、水动力、沉积物粒度和黏土矿物百分比等关系定性分析显示,本区∑REE的物源主要由陆源岩石控制,弱水动力和细颗粒度都对应较高含量的∑REE。结合北部湾海底沉积物的位置、砾石含量、砂含量、粉砂含量、黏土含量和黏土矿物含量训练出来的BP神经网络在控制变量的情况下定量分析各影响因子与∑REE的关系,获得单个影响因子与∑REE的关系曲线。这些关系曲线揭示了北部湾沉积物中稀土元素与各影响因子的联系,所获结果与定性分析结果基本一致,该方法能够通过自主学习,自动判断并定量计算,有助于识别每一个因子对稀土元素含量影响的大小,是如何控制∑REE的分布,从而根据曲线的变化规律结合实际情况去推断区域的环境变化及地质演变,对稀土元素的富集和分散分析提供有益的理论指导。     

东太平洋CC区沉积物稀土元素特征及物源

对东太平洋CC区中西部33站表层沉积物进行了稀土元素(REE,包括Y)地球化学研究。结果表明,REE在沸石粘土中最富集,在硅质沉积物中含量明显偏低;所有沉积物样品中REE都存在Ce负异常和Eu正异常的轻稀土(LREE)亏损特征,表现为典型受到海水来源物质影响的REE配分模式;硅质粘土中Ce亏损程度、Eu正异常和REE富集程度都比硅质软泥更明显。与东区相比,西区沉积物中LREE、HREE(重稀土和钇元素)和∑REE(稀土元素总量)普遍偏高,LREE与HREE分异更明显,HREE相对更富集,LREE和Ce亏损更显著。研究区表层沉积物中REE主要来自海洋自生物质,同时受到陆源物质、海底火山物质的影响。     

南黄海泥质区西北缘B01孔黏土粒级沉积物地球化学特征及其物质来源的识别

通过对南黄海泥质区西北缘B01孔黏土粒级沉积物的主量、微量和稀土元素的地球化学特征分析,探讨其物质来源及其影响因素。B01孔岩芯黏土粒级沉积物主量、微量和稀土元素在垂向上具有明显变化,以150cm为界,上段元素含量波动强烈,下段相对稳定,B01岩芯黏土粒级沉积物轻重稀土分馏明显,轻稀土元素含量较高,经球粒陨石标准化的δEu明显负异常,δCe无明显异常,呈现负斜率右倾的稀土元素配分模式;经上陆壳(UCC)标准化的δEu和δCe均无明显异常,表明B01岩芯沉积物为陆源物质。(La/Yb)UCC—(Gd/Yb)UCC判别图、La/Sc、Th/Sc和判别函数结果表明B01岩芯具有黄河和长江混合物源特征,在这个物源体系中,黄河与长江物质交替出现,可能是受黄河改道和陆架沉积动力因素的影响,冷水团的形成与演化、黄海暖流的路径及强度变化和受季风驱动的黄海沿岸流都对B01岩芯的物源起到重要作用。     

海底水－沉积物界面系统中稀土元素的变化及配分特征

本文利用”大洋多金属结核调查“期间”海洋4“号调查船HY₄-871、881航次在东太平洋海盆取得的底层水、沉积物、间隙水及多金属结核样品,对比研究了稀土元素(REE)在海底水-沉积物界面系统不同物质相中的分布变化及配分特征。结果表明,在大洋氧化性沉积物间隙水中REE相对于底层水亏损。除Ce外,沉积物与多金属结核REE含量较为接近。底层水、沉积物、间隙水REE配分特征极为相似,都表现出中稀土相对于轻、重稀土的轻度分离和富集,Ce表现为负异常。多金属结核中中稀土也有类似的富集倾向,但Ce主要表现为正异常。随深度的增加,沉积物REE含量增加,但其配分模式不变。     

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.     

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.     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

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.     

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。     

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.     

《Acta Oceanologica Sinica》Vol. 33(2014) contents

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INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,