Nitrogen forms and decomposition of organic carbon in the southern Bohai Sea core sediments   总被引：5，自引：0，他引：5  

Song Jinming  Ma Hongbo  L&#; Xiaoxia 《海洋学报(英文版)》2002,21(1):125-133

Study on form characteristics of nitrogen in marine sediments is the primary method to research its biogeochemical cycling and nitrogen form characteristics in core sediments can reflect the process and results of early diagenesis in a certain degree. In this paper, Sequential extraction process in natural grain size was used for studying the existent forms of nitrogen in five core sediments of the southern Bohai Sea for the first time. Nitrogen was divided into two parts -transferable and fixed based on whether it could be extracted by the reagent. Distributions and early diagenesis of transferable nitrogen forms in the southern Bohai Sea were researched integratedly. Results indicate that IEF - N and OSF-N are predominant forms in transferable part in the studied core sediments. Contents of different nitrogen forms vary differently with depth, and have different diagenesis process. Decomposition constant of organic nitrogen (ON) and OC are about 15.51 × 10~(-3)a~(-1)and 4.79× 10~(-3)a~(-1) respective  相似文献   

The impact of shrimp trawling and associated sediment resuspension in mud dominated, shallow estuaries     

Timothy M. Dellapenna  Mead A. Allison  Gary A. Gill  Ronald D. Lehman  Kent W. Warnken 《Estuarine, Coastal and Shelf Science》2006,69(3-4):519

To address the relative importance of shrimp trawling on seabed resuspension and bottom characteristics in shallow estuaries, a series of disturbance and monitoring experiments were conducted at a bay bottom mud site (2.5 m depth) in Galveston Bay, Texas in July 1998 and May 1999. Based on pre- and post-trawl sediment profiles of ⁷Be; pore water dissolved oxygen and sulfide concentration; and bulk sediment properties, it was estimated that the trawl rig, including the net, trawl doors, and “tickler chain,” excavate the seabed to a maximum depth of approximately 1.5 cm, with most areas displaying considerably less disturbance. Water column profile data in the turbid plume left by the trawl in these underconsolidated muds (85–90% porosity; <0.25 kPa undrained shear strength) demonstrate that suspended sediment inventories of up to 85–90 mg/cm² are produced immediately behind the trawl net; an order of magnitude higher than pre-trawl inventories and comparable to those observed during a 9–10 m/s wind event at the study site. Plume settling and dispersion caused suspended sediment inventories to return to pre-trawl values about 14 min after trawl passage in two separate experiments, indicating particles re-settle primarily as flocs before they can be widely dispersed by local currents. As a result of the passage of the trawl rig across the seabed, shear strength of the sediment surface showed no significant increase, suggesting that bed armoring is not taking place and the trawled areas will not show an increase in critical shear stress.  相似文献   

The impact of the M₂ internal tide on data-assimilative model estimates of the surface tide     

E.D. Zaron  G.D. Egbert   《Ocean Modelling》2007,18(3-4):210-216

We use a synthetic data experiment to assess the accuracy of ocean tides estimated from satellite altimetry data, with emphasis on the impact of the phase-locked internal tide, which has a surface expression of several centimeters near its sites of genesis. Previous tidal estimates have regarded this signal as a random measurement error; however, it is deterministic and not scale-separated from the barotropic (surface) tide around complex bathymetric features. The synthetic data experiments show that the internal tide has a negligible impact on the barotropic tidal fields inferred under these circumstances, and the barotropic dissipation (a quadratic functional of the tidal fields) is in good agreement with the energetics of the three-dimensional regional primitive equations model which is the source of the synthetic data.  相似文献   

南黄海及相邻陆区松散沉积层磁性地层的研究     

周墨清  葛宗诗 《海洋地质与第四纪地质》1990,(4)

本文通过研究区5个钻孔松散沉积岩心磁性地层的划分对比,获知布容与松山极性带的界线,南黄海和陆区北部位于80.0—99.5m。陆区的南部此界线于270.4m深处。松山和高斯极性带的界线,海区未揭露到,其沉积起始时间都小于1.7Ma。而陆区的南、北部分别位于117m和328.2m。高斯和吉尔伯特极性带的界线,陆区北部为140m,而南部区为460.15m。沉积起始时间为3.4Ma。吉尔伯特底界仅北部陆区所揭示,为190.5m。松散沉积层与下伏白垩纪(?)石灰岩接触面位于400.35m,沉积起始时间约17.0Ma。  相似文献   

湄州湾沉积物地球化学特征     

许金树  李亮歌 《热带海洋学报》1993,(2)

根据湄州湾表层沉积物70个样品18个化学成分的分析结果,得出:本海区沉积物属于海相陆源物,其中细颗粒主要来自台湾海峡,粗颗粒来自当地陆域;化学成分含量按聚类分析,可归为三组:粘土矿物组、碳酸盐组和分散组,微量元素Zn,Cr,Be,Cu和Sr的含量与地壳及台湾海峡相似,但低于胶州湾,说明该海区污染很少。  相似文献   

Geochemistry and palaeo-oceanography of metalliferous and pelagic sediments from the Late Cretaceous Oman ophiolite     

A. H. F. Robertson 《Marine and Petroleum Geology》1986,3(4)

Metalliferous and pelagic sediments are exposed within and above the extrusive successions of the Upper Cretaceous Oman ophiolite which, on the basis of mostly geochemical evidence, is believed to have formed in an incipient marginal basin setting located above a NE-dipping subduction zone. The ophiolitic extrusives document various volcano-tectonic settings which include the axial zones of a spreading ridge, fault-controlled seamounts and off-axis volcanic edifices. Most of the Fe, Mn and trace metal-enriched sediments studied are interpreted as precipitates formed by oxidation of solutions derived from high-temperature sulphide-precipitating vents. The trace element content (e.g. REE and Sr) was largely scavenged from seawater. The sediments are similar to the dispersed metalliferous sediments on the flanks of modern spreading ridges, and the ‘basal’ sediments of DSDP wells and of other ophiolite complexes (e.g. Troodos, Cyprus).Distinctive mound structures located low in the lavas are attributed to percolation of sulphide-rich solutions into already deposited metalliferous oxide sediments. The resulting iron-silica rock was probably originally precipitated as ferruginous silicates.Major massive sulphides formed off-axis at the base of intermediate-basic edifices of volcanic arc affinities. Fe, Mn and trace metal enrichment in the sediment cover of a flat-topped seamount of axial lavas is interpreted as a dispersion halo around the largest massive sulphide orebody which is situated 5 km away (Lasail). Small massive sulphide bodies are common in the axial lavas particularly along major seafloor fault zones. The metalliferous sediments, locally precipitated near these vents, are ferromanganiferous, but trace metal-depleted.The metalliferous and pelagic sediment cover of the extrusive successions, generally, documents waning hydrothermal input after volcanism ended in the area.A model is discussed in which the ophiolite was created at a spreading axis above a subduction zone dipping away from the Arabian continental margin. With progressive subduction this crust approached the margin. Initially, calcareous sediment accumulated above the calcite compensation depth (CCD), but then non-calcareous radiolarites were deposited as the ophiolitic crust approached the continental margin where the CCD was higher and marginal upwelling possibly enhanced productivity. As the edge of the Arabian continental margin entered the trench, the over-riding ophiolite was regionally uplifted allowing short-lived chalk accumulation above the CCD. This was followed by volcaniclastic deposition related to the tectonic emplacement.  相似文献   

云南程海近500年来湖泊初始生产力的演化   总被引：14，自引：1，他引：14  

吴敬禄  蒋雪中  夏威岚  潘红玺  尹宇 《海洋地质与第四纪地质》2002,22(2):95-98

程海为富营养化封闭湖泊，通过对程海CH01乳沉积物色素分析，定性恢复了近500a来程海湖泊初始生产力演化过程，结果表明，近500a来程海湖泊初始生产力总体上呈现由低到高的上升趋势，其中1700AD前后，1790AD前后是湖泊初始生产力出现变化的界限，另外，色素含量变化揭示研究时期内存在1750AD前后，1930AD前后二次明显暖波动。  相似文献   

Geoacoustic Characterisation of Fine-grained Sediments using Single and Multiple Reflection Data     

J.-P. Hermand  C.W. Holland 《Marine Geophysical Researches》2005,26(2-4):267-274

Fine-grained sediments commonly occur in areas of the continental shelf where wave and current energy are weak. Bulk density, compressional wave speed and attenuation are fundamental physical properties of these sediments required for predicting the response of the seabed for diverse branches of marine science. The traditional coring approach is time and labor-intensive, with large uncertainties associated with sediment disturbance in the sampling phase. Acoustic methods offer the advantages of remote sensing, i.e., sampling the sediment structure without mechanical disturbance and a significantly larger seabed coverage rate per unit time. Two different acoustic methods are described: one using short-range single-bounce interactions with the seabed, and the second using long-range modal propagation to infer the sediment properties. The relative strengths and sensitivities of each approach are explored through simulations guided by experience with measured data.  相似文献   

A Preliminary Study of Shear Wave in Seafloor Surface Sediments   总被引：1，自引：0，他引：1  

Bo Lu  Ganxian Li  Shaojian Huang 《Marine Georesources & Geotechnology》2006,24(1):17-28

This article preliminarily reports and analyses the transmission characteristics and behaviors of shear wave in the offshore seafloor surface sediments in China, discusses the relationships between the physical and mechanical features of the shear wave and the compression wave, and compares the testing results with that of Hamilton and Chen et al. The result shows that the shear wave can be tested if the seafloor surface sediment has tangent modulus. The shear wave velocity ranges from 50-600 m/s and the measuring frequency from 50-200 kHz. The sound velocity rate of shear wave and compression wave can be used to appraise the stress-strain feature of seafloor surface sediments. This study provides a basis for further describing and appraising the seafloor sedimentary acoustic-mechanical feature and building a geological-acoustic model on China's offshore sea area.  相似文献   

北太平洋赤道海域表层沉积物的热释光特征及其指示意义          下载免费PDF全文

吕华华  石学法  吴永华  杨刚  魏建伟  王湘芹 《海洋学报》2007,29(3):162-171

热释光是矿物晶体接受环境核辐射作用后积蓄起来的能量在受到热激发时以光的形式释放出来的一种物理现象,它与晶体损伤、晶体中杂质混入等原因所导致的晶格缺陷有关.热释光强度的大小主要取决于自然界中长寿命放射性元素(238U,235U,230Th,40K及其子体)的衰变,与其他物理、化学、生物或人类活动无关.热释光特征能有效反映晶体形成的环境条件.热释光方法的制样简单、测量快捷,因此在辐射学、核工业、核医学、环境学、农业、考古学、地质学等领域都得到了广泛的应用.在陆地地质学上热释光方法在地质年代测定[1,2]、地层对比[3]、矿物世代划分[4]、矿床含矿评价[4,5]、陨石形成热的历史恢复[6]以及地质事件识别[7]等方面都取得了不少成果.  相似文献