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本文通过对中太平洋海盆４０多个表层沉积物的分析和研究，根据沉积物中各组分含量、物质来源和成因等特征，把本区表层沉积物分为六种类型。它们分布在不同区域和不同水深范围内。钙质沉积物分布在碳酸钙补偿深度（ＣＣＤ）界面以浅区。硅质粘土、深海粘土等沉积物出现在ＣＣＤ以下水深区，这些沉积物的分布具有明显的垂向分带性和横向分区性。沉积物类型的变化主要受水深与物质来源的控制，南极底层流也有一定的影响。在不同的沉积物中锰结核的丰度、品位、类型等亦有明显的差异。 相似文献
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冲绳海槽中部南奄西海丘海底热液活动的若干特征 总被引：1，自引：0，他引：1
冲绳海槽中部南奄西海丘海底热液活动为弧后盆地型热液活动。在水深 ６５０～７７０ｍ处发育有活烟囱，喷出的热液温度（２７０℃）临近当地沸点（２７５℃），热液 中富含ＣＯ２气泡。稳定同位素研究表明，热液活动与岩浆活动有关。根据热液沉积 物的矿物学及化学特征可将其划分为４种类型，它们是富硅热液沉积物、富硫酸盐 热液沉积物、块状富硫化物热液沉积物和碎屑状富硫化物热液沉积物。热液沉积物 中至少含有２７种矿物，并富集了Ｚｎ，Ｐｂ，Ｃｕ，Ａｇ等成矿元素。 相似文献
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海洋沉积物和上伏水的样品是在华盛顿州的三个航次和墨西哥西北海岸的两个航次中采集的。墨西哥边缘１５０～１６０ｍ水深有一个明显的缺氧带。其溶解氘的浓度太低了,用常规方法检验不出来。相反,华盛顿边缘较低的缺氧带的氧浓度在８００ｍ降至２０μｍ０ｌ。海岸带彩色... 相似文献
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岩心ＮＥＡＰ１８Ｋ（５２°４６′Ｎ ,３０°２１′Ｗ,水深３２７５ｍ）是从Ｃｈａｒｌｉｅ＿Ｇｉｂｂｓ断裂带获得的。该断裂带位于向西流出冰岛盆地的北大西洋深水主体内部。岩心中浅成底栖有孔虫Ｃｏｂｉｃｉｄｏｉｄｅｓｗｕｅｌｌｅｒｓｔｏｒｆｉ和浮游有孔虫Ｇｌｏｂｉｇｅｒｉｎａｂｕｌｌｏｉｄｅｓ的δ１８Ｏ和δ１３Ｃ组成变化已达到了１～２ｃｍ的分辨率。该岩心的冰携物历史是通过大于１５０μｍ沉积物组分中的大量有关冰携碎屑颗粒的变化重建的。作为ＣａＣＯ３ 百分比指标的沉积物亮度是用分光光度计在岩心下部以１ｃｍ为… 相似文献
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南海北部陆坡区是中国最具潜力的天然气水合物聚集区。通过对研究区似海底反射层（BSR）、水深及热流值分布进行交会,得到了水深、热流双因素对天然气水合物形成的共同控制机理。研究认为,热流值中等（70～83mW／m^2）的地区最有利于天然气水合物的形成和聚集,热流值升高,天然气水合物形成的水深有总体增大的趋势。另外,天然气水合物的形成也需要良好的盖层条件。模拟了当上覆泥质沉积物盖层厚度不同时,天然气水合物形成所需的最低水深,并对不同泥质沉积物盖层厚度对天然气水合物稳定带底界面和厚度的影响做了研究和探讨。当泥质沉积物盖层的厚度越大时,天然气水合物形成的水深可以更浅;当泥质沉积物盖层厚度较小时,天然气水合物的形成则需要更大的水深。另外,当水深越大时,天然气水合物稳定带的底界面（BGHSZ）越深,天然气水合物稳定带的厚度越大。 相似文献
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宁波及其邻近海域沉积物释放耗氧有机物（COD）的初步研究 总被引：2，自引：0，他引：2
本文通过对城市污水纳污海区沉积物样品释放有机物的研究，初步揭示了沉积物释放耗氧有机物（ＣＯＤ）的一般规律。研究表明宁波海域沉积物释放ＣＯＤ的范围在０．１５×１０－３～０．８０×１０－３之间，释放速率平均为１０３．９ｍｇ／（ｍ２．ｄ）；舟山沈家门附近海域沉积物释放ＣＯＤ速率平均为２５３．１ｍｇ（ｍ２·ｄ）。沉积物释放ＣＯＤ的量与沉积物中有机质的含量成正比，而其释放速率与沉积物有机质的含量关系不大。 相似文献
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宫古群岛外陆架和陆坡上受潮流影响的高能环境和与红藻石有关的碳酸盐沉积ＹｏｓｈｉｈｉｒｏＴｓｕｊｉ宫古群岛位于日本琉球岛弧南部。沉积在开阔陆架和水深９００ｍ陆坡上的沉积物泥质含量低（＜５％），而沉积在潮流受阻水深２０ｍ的浅部陆架区的沉积物泥质含量高（＞... 相似文献
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深海沉积物和海水碳交换的同位素示踪Ｊ．Ｅ．Ｂａｎｅｒ等海洋沉积物含有较多的有机碳，对上覆水体中有机质的性质有一定的影响．普遍认为，海底沉积物可能是深层水中老而难已测定的溶解有机碳（ＤＯＣ）的来源；另外，放射性Ｃ同位素值（△１４Ｃ）和稳定Ｃ同位素比值（... 相似文献
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Chandralata Raghukumar G. Sheelu P. A. Loka Bharathi Shanta Nair C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16
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. 相似文献
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Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
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. 相似文献
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Derek V. Ellis 《Marine Georesources & Geotechnology》2001,19(1):51-63
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. 相似文献
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G. Parthiban 《Marine Georesources & Geotechnology》2000,18(3):223-235
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. 相似文献
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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. 相似文献
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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。 相似文献
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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. 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
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The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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