中国陆架的沉积环境地球化学

中国陆架沉积环境地球化学研究表明,我国近海和远海海域的海洋沉积物质量保持良好,部分近海海域沉积物质量较差。探讨了我国陆架海域沉积物的有机物、重金属元素和生源要素等环境地球化学。     

近海沉积物中氮磷的生物地球化学研究进展

通过对国内外学者十几年来在近海沉积物氮磷地球化学方面研究工作的综述，阐明了该方面的最新进展。主要包括：沉积物中氮磷的形态及分布特点，各种形态间的分配关系，以及与氮磷迁移转化相关的循环过程。最后对该领域今后的发展方向进行展望。     

近海N_P营养盐的研究现状与进展

海洋中N、P等营养盐是海洋生态系统中的重要营养元素,是海洋生物生存和繁殖的能量来源.同时,营养盐又具有复杂多变的化学地质作用,使得近海生态环境中营养盐的研究一直是海洋研究的热点之一,对海水营养盐的研究历史几乎与海洋化学发展史同步.由于环境问题的日益突出,营养盐的研究成为目前海洋及相关科学研究项目中的核心内容之一.笔者通过回顾当今国内外近海环境营养盐调查研究的历史和综述当今国内外该学科的研究现状,概括了该学科的主要进展,并指出存在的问题和今后的发展方向.     

环境沉积学及其发展趋势

环境沉积学是在地球科学发展到围绕资源、环境、灾害和全球变化4个主题展开工作的情况下产生的。它是指利用沉积学的数据、原理及研究方法，研究人类活动与沉积环境相互作用、相互制约的关系，用以解决人类开发利用自然环境所碰到的和可能引起的与沉积学相关问题的学科，它的目标是探求防治对策，促进社会、经济的持续繁荣与沉积环境保护的协调发展。其主要内容包括水资源问题、地质灾害研究、城市工程研究和矿业开发环境问题等。环境沉积学与人类健康的关系研究目前已得到了重视，环境地球化学与生物地球化学循环、人类对地球环境影响的过程和机制等研究都是值得注意的前沿课题。未来的环境沉积学必将向环境保护、遏止日趋严重的环境恶化等方面发展。     

海洋生物地球化学研究

海洋生物地球化学是在海洋生物化学与海洋地球化学的基础上新发展的一门分支学科．近十年来，该学科研究进展迅速，已成为当前海洋科学中最为活跃的研究领域之一．     

中国近海营养盐结构失衡与磷消耗问题及其生态环境效应的研究进展

近海的生态环境问题态势严峻。在机制上，普遍认为富营养化是导致近海环境恶化的主导因子，但实际上，营养盐的结构失衡对近海生态环境问题的产生可能起到了更重要的作用。目前关于营养盐结构失衡的主导因素和机制尚缺乏全面系统的研究。本文基于对已有数据和文献资料的整合分析发现，由于存在强烈的人类活动影响，中国近海营养盐结构失衡问题较过去更为突出，且可能引发潜在“磷消耗”问题，其影响在某种程度上较传统意义上的磷限制要强，并进而产生深远的生态环境效应。据此提出，今后相关的研究应该特别关注河流流域-近海环境变化和它们之间的内在关联，阐明控制近海营养盐浓度、形态、分布和结构的关键生物地球化学过程，量化近海氮与磷的滞留机制与效率，揭示浮游植物群落结构变化与营养盐结构失衡和磷消耗的耦合关系及其生态效应等，最终制定中国入海河流与近海氮磷协同控制的适应性管理措施。     

加强海洋灾害地质学研究减少海洋工程灾害

随着我国近海油气资源的开发及海洋工程的需要，海洋灾害地质学这一边缘学科正在我国兴起和迅速发展。本文对这一学科的研究对象、研究领域以灾害地质因素分类进行概述，并对海洋灾害地质学的特点与应用前景，进行了初步总结，最后对该学科的发展方向提出了积极建议。     

环境地球化学在农业环境污染方面的应用

综述环境地球化学在农业环境污染方面的应用,包括农业环境背景调查,农业环境污染因素分析,农业环境污染治理和农业环境评价4个方面。指出环境地球化学在农业环境污染研究方面有广阔的应用前景。     

中国近岸海域的沉积环境地球化学

中国近岸海域沉积环境地球化学研究表明,我国近海沉积环境质量总体尚属良好,但局部海域,尤其是一些河口、海湾的沉积物已受到有机物、重金属以及有机氯化合物等的污染。     

中国近海生态环境变化的同位素示踪研究

同位素在确定物质来源、指示生物地球化学循环路径、定量生物地球化学过程速率等方面具有独特的优势，本文以近海生态环境变化研究中常用的稳定同位素（13C、15N、18O）和放射性核素（14C、234Th、232Th、230Th、228Th、210Po、210Pb、137Cs、226Ra、228Ra、224Ra、223Ra）为对象，介绍它们在揭示海洋有机质来源、食物网结构、水体缺氧机制、氮循环过程、颗粒动力学、海底地下水输入、有机地球化学过程、沉积年代学等方面的应用，侧重于总结我国近海生态环境研究中同位素示踪取得的进展。伴随着我国经济的发展，近百年来我国近海生态环境也发生了明显的变化，基于同位素示踪揭示的近海富营养化和沉积环境的演变规律表明，我国近海生态环境自20世纪50年代起经历持续的变化，特别是在过去20~30年时间里，近海生态环境的变化尤为剧烈，反映出人类活动是我国近海生态环境变化的主要驱动力。未来需要通过发展新的同位素技术及拓展更广泛的应用，围绕近海海洋生态环境变化的突出问题，重点揭示近海生态环境变化的响应特征、变化速率和作用机制，从而系统地掌握近海生态环境的时空变化规律。     

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.     

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.     

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.     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

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.     

Flow Cytometric Analysis of Coastal Lagoon Bacterioplankton and Picophytoplankton: Fixation and Storage Effects

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.     

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.     

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,