深海沉积物分类与命名的参数指标和主成分分析

对于南海中部(118个表层沉积物样,水深82~4 420 m)、东部(106个表层沉积物样,水深700~4 508 m)海域的表层沉积物的粒度资料按小于200 m,200~2 000 m,大于2 000 m水深段对水深、平均粒径、黏土含量进行统计分析,结果表明从陆架到陆坡再到深海,平均粒径和黏土含量随水深增加呈非常有规律的变化;把大于2 000 m水深区域再细分为大于2 500 m,大于3 000 m,大于3 500 m,结果表明平均粒径和黏土含量随水深增加几乎无变化,在南海中部水深大于2 000 m海域平均粒径为3.39~3.54μm,黏土平均含量为54.91%~55.47%;在南海东部水深大于2 000 m海域平均粒径为3.25~3.37μm,黏土平均含量为53.91%~54.56%。研究表明2 000 m水深具有划分深海沉积物的指示意义。南海中部水深大于2 000 m海域黏土平均含量为55.19%,平均粒径为3.39μm;在南海东部水深大于2 000 m海域黏土平均含量为53.91%,平均粒径为3.37μm;在南海中部、东部水深大于2 000 m海域平均粒径均小于4μm,黏土平均含量均大于50%,表明深海沉积物粒度特征是平均粒径小于4μm和黏土平均含量大于50%。黏土含量是非生物组分的代表和划分深海沉积物类型的一个独立参数,钙质生物和硅质生物组分是另外两个独立参数。南海东部海域表层沉积物中55种元素总含量为47.50%,硅、铝、钛、钠、钾、磷、钙、镁、铁、锰十种主元素含量为47.03%,其他45种元素含量为0.47%,虽然沉积物来源复杂、成因不同,但沉积物化学主成分并不复杂,主要由前10种主元素和氧元素组成。沉积物主元素铝、钙、硅分别富集于黏土、钙质沉积、硅质沉积中。通过建立沉积物生源组分与碳酸钙、三氧化二铝、二氧化硅的量化关系,可把碳酸钙、生物二氧化硅作为钙质生物和硅质生物的两个替代参数。     

北部湾沉积物中重金属元素的地球化学特征及物源初探

本文根据北部湾沉积物岩心样调查结果计算了铜、铅、锌、镉、汞、砷等重金属元素的背景值,并分析了其与南海陆架区和南海全海域沉积物背景值、广西土壤背景值之间的差异.对北部湾表层沉积物中重金属含量及近10 a的变化趋势以及岩心样中重金属元素含量近百年以来的变化趋势综合分析结果表明:北部湾近岸海域沉积物中铜、砷、汞、镉重金属元素含量总体呈增长趋势,北部湾中部海域沉积物中重金属元素含量的年际变化有升有降,至湾口处沉积物中重金属元素的含量基本不变.综合评价结果表明,北部湾近岸沉积物中砷、汞、镉等重金属元素的地球化学特征明显受到广西人类活动的影响.北部湾沉积物中的重金属元素主要来源于人类活动影响下的广西沿岸陆源输入,经由琼州海峡的外部海域物质输入也有贡献.     

南海中部沉积物颗粒组分特征

为研究南海中部沉积物的粒度特征及其蕴含的古海洋信息,对南海中部中沙以南的陆坡和海盆区表层沉积物及分别位于陆坡和海盆的2根柱样进行了粒度、扫描电镜、CaCO3和生物硅含量的分析.结果显示,南海中部沉积物由三类颗粒组分构成,其中,第一类颗粒组分的峰值粒径在5～10μm之间,主要由陆源矿物碎屑组成;第二类组分的峰值粒径在40～70 μm之间,主要由有孔虫和硅藻组成;第三类颗粒组分的峰值粒径＞ 400 μm,由生物骨骼碎屑组成.这三类颗粒组分中第一类在研究区表层沉积物中均存在,第三类则随机分布,第二类颗粒组分多以有孔虫为主,其含量受水深控制.在南海中部碳酸钙临界补偿深度[Dc(CaC03)]以浅的陆坡区,因有孔虫含量较多,沉积物粒度曲线多为双峰形态,而在Dc(CaCO3)值以下的海盆区,因大部分有孔虫被溶解,沉积物中第二类颗粒组分为含量相对较低的硅藻,沉积物粒度曲线呈单峰或双峰形态.无论是陆坡区还是海盆区的柱样沉积,其平均粒径、第二类颗粒组分含量的变化均反映了有孔虫或硅藻含量的变化,因此,可以作为研究南海中部古生产力的替代性指标.     

南海中部沉积物中粘土矿物的分布

南海中部小于2μm粒级的119个表层沉积物样品的分析表明,粘土矿物主要由伊利石、蒙脱石、绿泥石和高岭石组成。伊利石含量占优势,并由西北逐渐向东南方向减少;蒙脱石含量仅次于伊利石,其变化趋势与伊利石相反。根据粘土矿物的分布和组合,认为南海中部沉积物中粘土矿物主要来源于北部的亚洲大陆,其次是南海东部及南部的邻近岛屿。蒙脱石除源于大陆派生的岩石风化物外,主要来自火山物质的蚀变。     

南海东部海域的沉积作用和物质来源研究

1998年在南海东部海域采集了195个表层和24个柱状沉积物样,对沉积作用和物质来源研究表明:(1)南海东部海域具有典型的边缘海沉积特征,沉积物主要由陆源碎屑、生物碎屑、火山碎屑、浊流沉积物组成,沉积作用具有多样性;(2)黄岩岛以北海区沉积物中基性岩组分含量为23.2%,陆源硅铝质组分含量为76.8%,这两种组分的理论计算值与海底沉积物实际分布相一致;(3)由碎屑矿物分析得出陆源矿物、混合矿物、自生铁锰矿物和中基性火山矿物四种矿物组合区,矿物组成和含量差异反映了物源和沉积环境的变化;(4)对沉积物中大于0.063 mm的物质全组分分析表明,生源组分占66.97%,其中钙质生物含量为23.43%,硅质生物含量为43.54%,钙质生物高值区主要分布在水深小于3 500 m的海区,硅质生物高值区主要分布在水深大于3 500 m的深水区;(5)南海东部海域火山沉积作用明显,海底扩张区沉积物中铜、钡、铁、锰、钴、镍、砷等金属物质分布与海底构造和海底中基性火山活动密切相关;(6)对沉积物粒度、物质组成和生物化石组合分析表明北部陆坡区69柱187.5~190.0,287.5~280.0,377.5~380.0 cm,深海平原区149柱157~187,187~194 cm,南部陆坡区323柱280~350 cm在粒度上表现出浊流沉积特征;(7)对锶同位素物源示踪和粒度、矿物的研究表明,北部陆源碎屑向南一直扩散到约17 N,西吕宋海槽是亚洲大陆物质特别是我国大陆物质向南海东部海域输运的主要通道.     

南海火山玻璃的分布特征、化学成分及源区探讨

研究了南海火山玻璃的分布特征、化学成分及源区,结果表明,表层沉积物中的火山玻璃含量基本呈南北向分布,由北部、西部、南部大陆架分别向中部、东部深海盆逐渐增加;柱样沉积物中的火山玻璃在深海盆出现的层数多、含量大.火山玻璃化学组分之间的相关性不显著,表层沉积物中的火山玻璃属于安山岩,柱样沉积物中的火山玻璃的岩石类型广泛,主要属于安山岩和流纹岩.菲律宾岛弧火山带、南海深海盆火山喷发以及印尼岛弧火山带是南海火山玻璃主要源区,火山玻璃搬运和沉积主要受台风、越赤道气流和环流的影响和控制.     

南海表层沉积物与水柱中沉降颗粒物对比研究及其古环境再造意义

分析了南海62个表层沉积物样品中生源(有机质、碳酸钙和蛋白石)和非生源(岩源物质)组分的含量变化和分布特征,并以沉积学分区为基础,结合5个沉积物捕获器站位,将南海划分为N、C-NE、SW和S 4个区域,对比分析了各区表层沉积物和水柱中沉降颗粒物中各组分含量、沉积通量分布特征和变化,探讨了表层沉积物的输出生产力、沉降颗粒物的初级生产力及真光层下100 m输出生产力三者之间的对应关系.结果显示:南海4个海域表层沉积物中各组分平均含量多数低于沉降颗粒物中的平均含量,而碳酸钙、岩源物质的沉积通量却多数高于沉降颗粒物中的沉积通量,分析得出表层沉积物中各组分平均含量和沉积通量不仅受水柱中各组分输出量影响,还受到陆源物质输入、溶解作用和上层水体营养盐影响.南海表层沉积物中生源组分沉积通量大小对应其输出生产力的大小.但是,由于陆源有机质、生源颗粒侧向漂移的影响,表层沉积物的输出生产力大小分布并不完全对应沉降颗粒物的初级生产力大小分布,尽管南海真光层下100 m输出生产力与沉降颗粒物的初级生产力比值与世界大洋"f"比平均值基本一致,但是,明显低于表层沉积物的输出生产力大小,只有在沉降颗粒物的初级生产力较高区域,真光层下100 m输出生产力大小才最接近表层沉积物的输出生产力大小.     

三亚市近岸海域SYD1钻孔沉积物的稀土元素和物质来源

文章采集三亚市近岸海域SYD1钻孔的沉积物样品,对其稀土元素的含量进行计算和对比;通过对稀土元素δEu_(CN)、δCe_(CN)和LREE/HREE等的平均值以及球粒陨石标准化配分模式的分析和对比,探讨该区沉积物的物质来源。研究结果表明:SYD1钻孔沉积物稀土元素总量的平均值低于中国浅海沉积物和南海海域表层沉积物;稀土元素含量受沉积物粒度影响,符合"元素粒度控制律";该区沉积物源具有大陆地壳性质,以海南岛近岸陆源碎屑为主。     

浙江近岸海域表层沉积物中氮的存在形态及其含量的分布特征

运用分相浸取法分析了浙江近岸海域60个站位的表层沉积物(0～2 cm)中各形态氮的含量和分布.研究结果表明,表层沉积物中总氮(TN)含量为214.66～861.44 mg/kg,均值为580.52mg/kg,位于浅水区的长江口、杭州湾和浙江沿岸的TN含量低于东部远岸海域;可转化态氮(TTN)含量只占总氮的3.06%～37.24%,有机态和硫化物结合态氮(OSF-N)是沉积物中可转化态氮的主要赋存形态,非转化态氮(NTN)是浙江近岸海域表层沉积物中的优势形态.各站位沉积物中氮在不同提取相中的含量差异较大,与沉积物的陆源输入、沉积物重金属含量、粒径分布及沉积海域的水动力条件等因素有关.     

砷在贝类养殖区表层沉积物及贝类体中的积累和分布

2003—2004年福建近岸海域海洋环境和海洋生物质量的监测资料表明,福建沿海主要贝类养殖区表层沉积物和4种养殖贝类(僧帽牡蛎、太平洋牡蛎、缢蛏和泥蚶)体中砷含量分别为(4.15—13.7)×10-6(干重)和(1.28—3.56)×10-6(湿重),总平均值分别为9.06×10-6(干重)和2.22×10-6(湿重),均低于海洋环境污染评价标准限值。总体上看,福建沿海潮间带滩涂贝类养殖区表层沉积物和养殖贝类体中砷含量高于浅海贝类养殖区的含量,且呈闽东和闽南贝类养殖区高、闽中养殖区低的格局。贝类养殖区表层沉积物中砷含量的多寡与表层沉积物的类型密切相关,并与僧帽牡蛎、缢蛏体砷含量之间总体成正相关。     

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.     

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。     

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,