南海北部内孤立波影响海域悬浮颗粒物特征变化研究

悬浮颗粒物在“源-汇”沉积体系中扮演着关键角色,而南海常见的动力现象—内孤立波,则被证实是影响悬浮颗粒物分布和沉积过程的重要因素。该项研究于2022年9月在吕宋海峡至东沙群岛海域开展,采用LISST-deep与CTD设备进行同步观测,以研究悬浮颗粒物的粒径及体积浓度分布。通过调查期内的卫星遥感数据,划定了内孤立波的影响范围,并结合海床基观测内孤立波影响悬浮颗粒物分布过程,从动力学的角度揭示了内孤立波对悬浮颗粒物在输运过程中特征变化的影响。研究发现:(1)在内孤立波的振幅深度区间(6~79 m)内,以较小粒径的悬浮颗粒物(15~25μm)分布为主,且越接近内孤立波的波谷深度,出现较小粒径悬浮颗粒物的频率越高。(2)悬浮颗粒物分布由内孤立波波峰线中心区域扩散到两侧,在中心为体积浓度低值区(≤91μL/L),而波峰线两侧区域与内孤立波传播路径远端区域为体积浓度高值区(≥500μL/L)。此外,研究进一步揭示了内孤立波通过改造作用使聚集状态的悬浮颗粒物被分解为粒径较小、组成单一的颗粒,通过控制作用改变悬浮颗粒物在波峰线不同位置、传播路径和振幅深度上的体积浓度分布,为理解南海源-汇沉积体系提供了重要的理论依据。

海床流体迁移致灾机理与风险防控研究现状及展望

海床流体迁移指海底液体、气体、海水在海床内外的传输运移过程,对海洋地质灾害的孕育、发展、演化具有重要影响;我国海域内广泛发育的海底滑坡等典型灾害,与海床流体迁移现象之间呈现出明显的关联性。本文从海床流体迁移的灾害效应出发并以南海北部为例,分析了典型流体迁移系统类型、地质灾害成因分布特征,梳理了海床流体迁移的观测与调查方法;总结了海床流体迁移致灾与风险防控方向的科学问题,针对性提出了有待开展的重点研究内容。研究建议,从深部高压流体向上迁移影响灾害孕育、天然气水合物分解流体迁移影响灾害发展、海洋水体运动导致灾害发生3个方面着手,研究海床流体迁移影响下的海底灾害孕育、发展与触发演化过程机理,海床流体迁移-地质环境-人类活动耦合作用下海底灾害风险防控理论方法,支持突破深海探测多系统集成、多尺度联合、多维信息处理等技术瓶颈。

海底碳封存环境地质灾害风险及监测技术研究

海底CO_(2)地质封存是我国实现“双碳”目标的重要组成部分,但CO_(2)泄露具有诱发海底地质灾害的风险,威胁海洋工程的安全建设,因此开展封存区环境地质监测对海洋碳封存实施具有重要的现实意义。本文在简要介绍海底CO_(2)地质封存示范案例的基础上,阐述了海底封存区CO_(2)泄露的致灾机制,结合实例梳理了典型CO_(2)控释试验中的海洋环境监测技术,重点分析了与CO_(2)泄露相关的环境地质监测技术,包括地震调查与监测、电阻率法监测技术、重力监测技术、海床变形监测技术以及沉积物孔隙压力监测技术等,展望了我国海底碳封存及其环境地质监测的未来发展前景。研究认为,今后应侧重封存区CO_(2)泄露致灾机制与环境地质监测技术研究,建议在研发长时序、低成本并实时监测技术的基础上,结合封存区基线调查,建立和发展系统性、智能性的多维度灾害识别模型,构建多方面、多层次、多灾种的监测预警预报体系。

基于数字孪生的海底悬浮物时空变化可视化技术实现与应用

数字孪生技术构建的虚拟海洋平台,能够进一步实现海底环境监测数据的三维可视化分析。本文基于深海底长期原位监测数据,使用Unity3D技术构建出多模型融合的虚拟海洋环境,初步建立海洋工程地质环境数字孪生系统;结合MATLAB、ArcGIS数据分析技术实现智能监测、数据分析、人机交互、辅助决策等功能;研究进一步构建虚拟环境粒子系统,对南海北部陆坡神狐海域近底层悬浮物浓度升高事件进行了三维可视化分析,结果表明:在虚拟环境粒子系统中悬浮物浓度、粒子数量与聚集程度具有较大的时空差异。特别是悬浮物浓度维持在较高水平时,发现粒子间相互碰撞、重叠,并在空间中衍生了密集程度更高的微团,当悬浮物浓度进一步升至峰值时,微团数量增加并占据空间大部分体积,形成悬浮颗粒高度聚集,覆盖范围更广的悬浮物聚合体。本文基于图像分析技术,将可视化分析结果与真实海底摄像进行对比,相对误差在0.16%~2.80%范围内,具有较高的可行性。

海洋测绘在西南浅滩海砂资源探测中的应用

以钻探为主要手段的海砂资源勘查,具有高投入和高风险的特点。为了进一步提升资源勘查的效率和精确度,可充分利用多波束测深、浅地层剖面测量等海洋测绘手段,对海砂进行探测。利用单波束测深、多波束测深和浅地层剖面测量,结合钻探验证,圈定了西南浅滩海域海砂资源的分布、范围和厚度;并利用高精度海洋测绘数据,构建了海砂矿体顶底的DEM,预测了研究区海砂资源潜力约13.54亿立方米,该方法预测精度远高于传统钻探方法。因此,海洋测绘方法可以有效地识别海砂资源的空间分布,在资源量预测方面也具有较大优势,能够较大地提升海砂探测的工作效率。

南海北部油气缓释环境沉积物脂类化合物组成特征

认识沉积环境有机碳留存状况是阐述油气形成过程中有机碳早期成岩的关键内容。以南海珠江口盆地及其邻近海域为背景,通过研究表层沉积物中脂类化合物的形态组成,认识脂类有机碳的来源和留存状态,阐述特征脂类分子的早期成岩特征。结果表明,研究区域表层沉积物有机碳含量为0.22%～0.66%,有机碳稳定同位素分布在-20.88‰～-22.93‰之间,表现为显著的海源特征。沉积物中共检测出21种脂肪酸、6种脂肪醇、8种甾醇和植醇;总脂肪酸、脂肪醇、甾醇和植醇含量分别为12.57～40.27μg/g、5.35～8.98μg/g、0.15～3.75μg/g和0.01～3.99μg/g干重,总体表现为靠近珠江口和台湾海峡略高。脂类化合物的存在形态以游离态(FR)和碱性水解态(BH)为主,酸性水解态(AH)贡献较低;其中植醇和甾醇呈现显著的BH优势,植醇中未检出AH组分的贡献。脂类化合物主要来自于海洋现场生产,海洋微藻和细菌的相对贡献率分别为21.18%～33.78%和11.02%～15.64%,陆源高等植物贡献低于5%。来源于硫酸盐还原菌的支链脂肪酸在靠近珠江口海域高达1.79～2.62μg/g,占总脂肪酸的5.14%～6.50%,并与硫酸盐还原过程相关的古菌分布相一致。

建筑用海砂资源开发利用适宜性评价初探:以琼州海峡东口为例

经济的快速发展,对砂石料的需求巨大,海砂的开发成为当前的热点。琼州海峡东口海砂资源丰富,资源潜力概算可达数十亿方。依据前期调查数据,选取含泥量、含砂量、粒级、海砂厚度、水深和离岸距离6类指标,采用层次分析法,构造判断矩阵计算评价因子的权重,运用ArcGIS空间分析功能进行叠加,对琼州海峡东口的海砂进行了开发适宜性评价。结果表明:经计算将研究区分为开发适宜性好、较好、中等、较差、差5个等级,其中浅滩区域海砂规模大、质量好、水深浅和开采环境影响小,其开发适宜性最佳。分析了不同的指标对海砂开发适宜性的影响,在浅滩区,厚度和含砂量指标贡献较大;在近岸海湾,环境影响是主要因子;在琼州海峡深槽区,水深条件则成为海砂开发的主要限制条件。根据海砂资源的特点,建立了以资源自然属性、开发技术条件、生态环境影响和行政管理为主要因子的海砂开发利用适宜性评价体系,具体工作可选取不同的指标开展评价。研究结果可以为研究区海砂的开发利用和其他区域海砂开发适宜性评价提供参考。

Marine Geohazards： Review and Future Perspective

With offshore resource exploration moving to the deep water, marine geohazards have been attracting attention from the academic and industry. Research achievements of marine geohazards were reviewed in this paper. We analyzed and discussed typical issues among marine geohazards, including coastal erosion, submarine slope failure, turbidity current and special hazards induced by gas hydrate dissociation, in terms of their definition, distribution, characteristics and case studies. Major international projects on marine geohazards headed by the United States, Europe, Japan and other international organizations are introduced as well. Three marine geohazard survey methods, including geophysical survey, geotechnical exploration and in-situ observation, were summarized with a brief description of each approach, respectively. Especially, the history of marine geohazard researches in China is briefly reviewed, showing the disparity between China and developed countries in the study of marine geohazards narrows gradually. The potential research tendency in future was suggested.

Vertical Migration of Fine-Grained Sediments from Interior to Surface of Seabed Driven by Seepage Flows–‘Sub-Bottom Sediment Pump Action'

A scientific hypothesis is proposed and preliminarily verified in this paper: under the driving of seepage flows, there might be a vertical migration of fine-grained soil particles from interior to surface of seabed, which is defined as ‘sub-bottom sediment pump action' in this paper. Field experiments were performed twice on the intertidal flat of the Yellow River delta to study this process via both trapping the pumped materials and recording the pore pressures in the substrate. Experimental results are quite interesting as we did observe yellow slurry which is mainly composed of fine-grained soil particles appearing on the seabed surface; seepage gradients were also detected in the intertidal flat, under the action of tides and small wind waves. Preliminary conclusions are that ‘sediment pump' occurs when seepage force exceeds a certain threshold: firstly, it is big enough to disconnect the soil particles from the soil skeleton; secondly, the degree of seabed fluidization or bioturbation is big enough to provide preferred paths for the detached materials to migrate upwards. Then they would be firstly pumped from interior to the surface of seabed and then easily re-suspended into overlying water column. Influential factors of ‘sediment pump' are determined as hydrodynamics(wave energy), degree of consolidation, index of bioturbation(permeability) and content of fine-grained materials(sedimentary age). This new perspective of ‘sediment pump' may provide some implications for the mechanism interpretation of several unclear geological phenomena in the Yellow River delta area.

Occurrence of Different Forms and Implications of Compound Specific Sterols in Continental Sediments of the Northeast South China Sea

The South China Sea(SCS) is one of the most productive and accumulative marginal shelves of organic carbon in the world. To expound the transformation and preservation of organic carbon in the Northeast SCS, where abundant oil and gas resources have been reported, compound specific sterols in free(FR), base hydrolytic(BH), and acid hydrolytic(AH) forms were analyzed in surface and columnar sediments in May, 2016. The results showed that the total contents of sterols detected ranged from 0.15 to 3.74 ppm dry weight in the surface sediments, and gradually decreased from 3.41 to0.17 ppm dry weight from surface to deep sediments, in which cholesterol(27^(△5)) was the most abundant component. Sterols mainly existed in the BH form(54.51%-74.20%), followed by the FR form(25.50%-45.49%) and then the AH form(0-3.77%) in turn, in the surface sediments. BH and FR sterols accounted for 0-49.08% and 50.92%-100% in the columnar sediments, while AH sterols were undetectable. The contents of specific sterols indicated that, the primary source of marine organic carbon was about 5 times as much as that from terrestrial input. More and more FR sterols transformed into BH sterols with increasing sedimentary depth, and BH sterols absolutely dominated in sediment depths under 25 cm. The forms of Sterols C27 were maintained at a relative consistence state, but Sterols C28 to C30 degraded gradually during the sedimentation process. It was suggested that the stability of sterols, based on the chemical structures, might be the primary factor controlling their degradation and preservation in deeper sediments. These results would help to understand the organic carbon(OC) transformation in a hydrate formation area in a marginal sea.

In-situ Observations of Engineering Geological Environment during Hydrate Production Tests in Deepwater

Gas hydrates are ice-like combinations of methane and water.The global inventory of gas hydrates appears to be very large.Recent estimates of the total amount of methane contained in the world’s gas hydrates range

深海滑坡研究进展

随着深水油气资源开发、天然气水合物试采和海底管线铺设等人类工程活动的日益增多,影响资源开采和工程施工的深海地质灾害备受关注。深海滑坡作为主要深海灾害,其不稳定性研究具有重要的科学意义和实际价值。本文总结了国内外深海滑坡的研究历程,梳理了深海滑坡的形态结构及类型、深海滑坡研究的方法手段,讨论了地震与断层活动、天然气水合物分解两个重要因素对深海斜坡不稳定性的影响。近十年来,随着一些新方法的涌现,研究热点已由深海滑坡的形态结构及分类等转移到深海滑坡的触发机制、滑动过程原位观测等方面。但现场调查技术、物理模拟试验和数值模拟试验仍是深海滑坡研究的主要方法手段,ROV/HOV等非常规技术也在逐步应用于深海滑坡的研究中。深海滑坡的产生通常是由海床内部地质作用和外部水动力作用共同引起,多种触发机制对深海滑坡的耦合作用及新触发机制对深海滑坡的影响仍是未来研究的重点。

The observations of seabed sediment erosion and resuspension processes in the Jiaozhou Bay in China

In estuarine and coastal areas, the seabed is in a constant process of dynamic change under marine conditions.Seabed sediment erosion and resuspension are important processes that safely control the geological environment. Field tripod observations conducted in the Jiaozhou Bay in China are reported, to investigate the effects of hydrodynamic conditions on the erosion and resuspension processes of the seabed. The observational results show that the maximum shear stress created by tidal currents can reach 0.35 N/m2, which is higher than the wave-induced shear stress during fair weather conditions. A seabed erosion frequently occurs during the flood tide, whereas a seabed deposition occurs during ebb tide. Waves can produce a bottom shear stress approximately equivalent to that induced by currents when the local wind reaches Force 4 with a speed of 5 m/s.When the wind reaches 7 m/s and the significant wave height reaches 26 cm, waves play a more significant role than currents in the dynamic processes of the seabed sediment resuspension and lead to a high value of turbidity that is approximately two to eight times higher than that in fair weather. These analyses clearly illustrate that periodic current-induced sediment erosion and resuspension are dominant in fair weather, whereas episodic high waves are responsible for significant sediment resuspension. Additional work is needed to establish a more thorough understanding of the mechanisms of sediment dynamics in the Jiaozhou Bay.

Dynamics of Bottom Boundary Layers in the Yellow River Subaqueous Delta Based on Long-Term In-Situ Observations

Objective In geo-marine science,the generalized bottom boundary layer（BBL）represents a layer between sediments and seawater.The BBL plays an important role in geological,geobiochemical,geophysical and geotechnical research because it is the connection region of hydrosphere,

海底天然气水合物开发的前景研究——基于经济可行性的视角

海底天然气水合物的开发利用对于国家能源安全与环境保护具有重要意义。然而,作为一种新型深海能源,海底天然气水合物至今仍未实现商业化生产。除开发技术等因素外,天然气水合物开发投入、产出的成本问题也是制约海底天然气水合物大规模开发的另一关键因素。文章从经济可行性的视角分析海底天然气水合物目前开采成本、未来开采成本的变化以及未来的价格优势,从而对天然气水合物开发的前景进行相关研究。研究结果显示,虽然目前天然气水合物的开采成本要高于常规天然气,但随着今后开采技术的改进,天然气水合物开采的总成本、边际成本和平均成本都会相应降低,当天然气水合物的价格低于常规天然气价格时,天然气水合物的商业化生产便可能实现。

Liquid-plastic Limit of Surface Sediments in North Slope of South China Sea

1 Introduction China has a vast area of continental shelf and is very rich in marine resources,but because of the complex geological environment and frequent geological disasters,the utilization of marine resources and the construction of marine engineering are limited(Zhu et al.,2016).As the

Surface Sediment Density and Moisture Content in North slope of South China Sea

Marine engineering geology is mainly based on the actual project to study the seabed.This provides a variety of engineering geological parameters for the development of marine engineering(Zhu et al.,2016).This is an early

持续与间歇声门下吸引预防呼吸机相关性肺炎效果的Meta分析

目的系统综述持续和间歇声门下吸引预防呼吸机相关性肺炎的效果.方法计算机检索Cochrane图书馆、PubMed、MEDLINE、EMBASE、Web of Science、中国生物医学文献数据库、中国知网、万方和维普数据库自1994年7月—2019年7月国内外公开发表的随机对照试验,进行文献筛选、质量评价、数据提取,采用RevMan 5.3软件进行Meta分析.结果共纳入18篇文献,1951例患者.Meta分析结果显示,两组呼吸机相关性肺炎发生率和发生时间、气囊上滞留物吸引量、机械通气时间、ICU住院时间差异无统计学意义(P>0.05),气囊上滞留物隐血试验阳性率差异有统计学意义(P<0.01).结论与间歇声门下吸引相比,持续声门下吸引并不能降低VAP发生率、机械通气时间、ICU住院时间,也不能延缓VAP发生时间和增加气囊上滞留物吸引量,且存在增加气道黏膜损伤的风险.

Preservation of Lipid Molecular Fossils in the Sediments from an Oil-Gas Releasing Zone in the South China Sea

In order to explore the standing stock and preservation of organic carbon, different forms of compound specific lipids were analyzed, based on a 1.8 m sediment core collected in the northern continental shelf of South China Sea in May, 2016. In the core sediments, 21 species of fatty acids, 6 species of alcohols, 8 species of sterols and phytol were detected. Fatty acids were dominated components with the percent of 67%–91% in the total lipids, in which saturated fatty acid C16:0 accounted for about 50%. The contents of lipid species generally decreased from the sediments at surface to those deep, except alcohols waving in a certain range at the same time. Fatty acids primarily existed in free form, followed by base hydrolytic form, and then acid hydrolytic form. Free alcohols were obviously dominated, while base and acid hydrolytic forms contributed small comparably. Phytol gave a significant priority to base hydrolytic form, while acid hydrolytic form could be neglected. Similar to phytol, sterols mostly presented in base hydrolytic form, and then in free form. The compositions of lipids and their forms suggested that organic carbon basically originated from primary production in upper waters in studying area, and were well preserved in the sediments.

快速沉积作用对海底滑坡的贡献机制及影响因素研究

众多海底滑坡都与快速沉积作用相关,然而,对海底滑坡的贡献机制以及影响因素缺乏系统研究。通过收集与快速沉积作用相关的海底滑坡相关案例,归纳和总结了海底滑坡基本特征。在此基础上,阐明了快速沉积作用触发海底滑坡机制,并给出在ABAQUS中的实现方法,最后对快速沉积作用触发海底滑坡的影响因素进行系统分析。研究结果表明:快速沉积作用导致海底地层超孔隙水压力累积,造成地层有效应力和强度增长减缓甚至降低,形成类似于“低重力场”环境,使海底斜坡在抵御地震、水合物分解、底辟等地质作用下能力减弱。此外,随着海底斜坡坡度的增加,沉积速率的加快,沉积物压缩性的增大,海底斜坡更易出现短滑动周期的浅层破坏。在低沉积速率,沉积物高压缩性条件下,也会导致海底地层欠固结,最终对海底斜坡稳定性产生不利影响。