Characterization of Sediment from Ourokessoum, North Cameroon: Morphostructural, Mineralogical, and Physicochemical Properties

The present study examines the morphological, physicochemical, and mineralogical specificity of clay sediments in the Hamakoussou Basin with the objective of exploring their potential applications. Field data collection was followed by a series of physicochemical and mineralogical tests on the clay samples. Results show that the clay layers, which range in thickness from 11 - 120 cm, exhibit gray, yellowish, or greenish colors. From a physicochemical perspective, these clay layers are found to be basic with a pH ranging from 8.5 for the higher Hama2 layer to 7.6 for the lower Hama1 layer. The sum of exchangeable bases (S) is medium to high with higher values in the Hama1 layer (53.45 meq/100g) and lower values in the Hama3 layer (17.09 meq/100g). Similarly, the cation exchange capacity (CEC) varies from 62.32 meq/100g for the higher Hama1N4 clay layer to 35.6 meq/100g for the lower Hama1N3 clay layer. Mineralogically, the clay materials are primarily composed of smectites, with illite, kaolinite, calcite, quartz, feldspar, hematite, and goethite also present. This study emphasizes the versatility of clay in various industries and scientific domains. It is known for its impermeability, plasticity, and fossil-preserving capabilities, making it a valuable material for economic, practical, and academic applications.

Concentrations,Accumulation and Sources of PAHs in Surface Layer Sediments of Taizhou Bay

The concentrations, accumulation and sources of 15 polycyclic aromatic hydrocarbons （PAHs） had been studied or evaluated in the surface layer sediments of Taizhou Bay, China. It showed that the concentrations of PAHs ranged from 85.4 to 167.6 ng/g （averaged 138.62 ng/g）, and the highest level was found in Jiao Jiang Dock. Percentages of 2-, 3-, 4-, 5- and 6-cyclic aromatic hydrocarbons were 7.8 %, 42.1%, 33.3 %, 9.6 % and 7.2 % respectively. The accumulation indices of PAHs ranged from 532.7 to 1068.9 （averaged 807.5）, and the index of Phenanthrene was the highest （122.7）, while that of Benzo （a） Pyrene was the lowest （2.7） among them. In Taizhou Bay, PAHs in surface layer sediments came mainly from coal burning, partly from direct pollution of petroleum hydrocarbons.

Observations of boundary layer parameters and suspended sediment transport over the intertidal flats of northern Jiangsu, China

A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above the seabed. Based upon the logarithmic-profile equation, the boundary layer parameters, i.e., u, z0 and C60, were obtained for 247 tidal flow velocity profiles. Around 90% of the profiles were logarithmic according to the critical correlation coefficient. Internal consistency analysis shows that these parameters derived by different methods are consistent with each other. In addition, the height of the bedforms observed is close to the seabed roughness lengths calculated from the velocity profiles, indicating that the boundary layer parameters obtained can reveal the conditions at the sediment-water interface on the intertidal flats. Suspended sediment concentrations were obtained from the 5 CTMS turbidity meters using laboratory and in-situ calibrations. The results show that the in-situ calibrated SSCs have a much higher accuracy than the laboratory calibrated ones. Calculation of suspended sediment fluxes on the intertidal flats, with a magnitude of 104 kg/m per spring tidal cycle, indicates that suspended sediment moves towards the northwest, which is reversal to the transport pattern controlled by the southward Northern Jiangsu Coastal Current in the sub-tidal zone and adjacent shallow waters.

Threshold of Sediment Movement in Different Wave Boundary Layers

A review of former studies on the onset of sediment movement under wave action reveals that the Shields criterion obtained in unidirectional steady flow can also be applicable to oscillatory unsteady flow when the boundary layer is the same. In this paper, through comparison of different boundary layers in wave and steady flow conditions, a new criterion is presented which can be used to predict the threshold of sediment movement Linder wave action. The criterion curve shows good agreement with the experimental data.

Sedimentary Changes of a Sand Layer in Liquefied Silts

A flume experiment was conducted to investigate the restratification of liquefied sediment strata under a wave load with the focus on the interbedded strata of coarse and fine sediments formed in estuarine and coastal areas.The aim of this research was to study the characteristics and processes of liquefied sediment strata in terms of wave-induced liquefaction.In the experiment,the bottom bed liquefied under the wave action and the liquefied soil moved in the same period with the overlying waves,and the track of the soil particles in the liquefied soil was an ellipse.The sand layer consisting of coarse particles in the upper part,settled into the lower silt layer.The sinking of coarse particles and upward migration of the fine particles of the lower layer induced by liquefied sediment fluctuations are the likely reasons for sedimentation of the sand layer in liquefied silt.

The fine velocity structure of sediment－base－ment layer in the Three－GorgesRegionoftheChangjiangRiver（YangtzeRiver）

In this paper, the study on the fine velocity structure of sedimental and basement layers along 4 deep seismic sounding profiles in the Three Gorges Region of the Changjiang River (Yangtze River) are presented. The velocity of sedimental cover is larger in hills of western Hubei in the western profiles, the total thickness is about 0～0.3 km. However, it becomes thick in southern part of Zigui basin and Zushui river valley, about 5.0 km and 4.0 km thick respectively. The sedimental cover is very thick in Jianghan plains in the eastern profiles, about 5～8 km, and the velocity is lower. The velocity of basemental plane is greater than 6.0 km/s over the whole region. An interface can be divided within the sedimental layer, it is about 3～4 km deep in Jianghan plains, while it approximates to surface in other regions. The profiles are cut by faults in many positions. Where the faults pass, the velocity isopleth varies sharply, and the velocity is obviously low. The basement layer is characterized by high velocity and low gradient, there exist 3 high velocity anomalous zones within the layer, which are located at the west, south and east of Huangling Anticlinorium respectively. They are the upwelling materials of basalt magma with high velocity from deep crust. Perhaps, this process took place before formation of Huangling Anticlinorium. Its action produces the significant variation of basement plane depth and the correspondent development and action of faults.

Study on reflection and transmission characteristics of shear waves at sediment layer interface

Since most of the natural disasters in the Yellow River are caused by sediment,the study of sediment composition,erosion and transport law is a fundamental part of sediment management in the Yellow River.As a method of in-situ testing,shear wave detection can obtain physical parameters such as the shear modulus of sediment.This paper,based on the Biot–Stoll model,deduces the equations for calculating the reflection and transmission coefficients when a shear wave is incident at the interface between sediment layer,and analyzes the effects of frequency,incident angle and porosity on the reflection and transmission coeffi cients of shear waves,as well as the diff erences in the propagation characteristics of longitudinal and shear waves at the interface between sediment layer.The results indicate that the refl ection and transmission coeffi cients of shear waves are linearly related to the porosity of sediment,and the refl ection coeffi cient of shear waves increases with the increase of porosity.The incident angle has a great infl uence on the changes of the reflection and transmission coefficients of shear waves,especially near the critical angle,the coeffi cients change abruptly.The frequency has a great infl uence on the refl ection and transmission coeffi cients of shear waves only near the characteristic frequency of sediment,while deviation from the characteristic frequency,the infl uence is small.The research results have certain signifi cance for obtaining the physical parameters of sediment and analyzying the composition of the Yellow River sediment and its erosion law.

The age measures and its layer sequence tratigraphy of Late Quaternary sediment in Lushan Dajiaochang of China

Through the scientific investigation on Lushan for a long time, detailed studies have been carried out on the geologic stratum section of Late Quaternary in Dajiaochang. The series age data of complete stratigraphic section and full time formation since 400 kaBP were based on the results of the analyses using the dating methods with various instruments such as the ancient geomagnetism, electronics spin resonance （ESR）, 36C1 and lumines- cence dating, etc. Corresponding to these data, it identified the paleomagnetic polarity events including Biwa- III event （320 kaBP）, Biwa- 1I event （260 kaBP）, Biwa- I event （180 kaBP, scarcity due to the disturbance of the iron dish）, Blake event （100 kaBP） and Laschamp event （20 kaBP, didn＇t grow due to the activities of the surface）, etc. Combined with the sequence stratigraphy, layer type characteristics and its sediment environment, the strati- graphic can be divided into 4 stages of development respectively ： Stage [ is the climate period of glacial epoch （200-400 kaBP）; stage 11 is the climate period of interglacial epoch （100-200 kaBP）; stage llI is the climate peri- od of periglacial epoch （10-100 kaBP）; stage IV is the climate period ofpostglacial epoch （0-10 kaBP）.

Resistance of the diffusive boundary layer to salt release from saline sediments to freshwater

The diffusive boundary layer （DBL） is the zone for matter exchange between surface water and aquatic sediments. To elucidate the influence of DBL on salt release from saline sediments to freshwater, two experiments with or without wind blowing were conducted. According to the experiments, a 3.5 cm DBL is formed above the smoothed sediments at a steady wind field and this thickness is greater than other studies. The observed flux of salt through the DBL is 6% larger than the calculated value from Fick＇ s first law. The results indicate that molecular diffusion is the dominant mechanism for salt transport through the DBL. The presence of DBL suppresses the hydrodynamic enhancement for matter exchange between sediments and overlying water. Therefore, salts in the sediments of a polder reservoir may influence the water quality chronically.

Impacts of channel dredging on hydrodynamics and sediment dynamics in the main channels of the Jiaojiang River Estuary in China

Channel dredging in estuaries increases water depth and subsequently impacts sediment dynamics and morphology. The Jiaojiang River Estuary is dredged frequently owing to heavy shipping demands. In this study,the effects of different dredging schemes on siltation were assessed through numerical modeling. The sediment model of the Jiaojiang River Estuary utilized an optimized bottom boundary layer model that considered the bed sediment grain size and fluid mud, and this model was calibrated using field data. Result reveal that channel dredging modifies the flow velocity inside and around the channel by changing the bathymetry;subsequently, this affects the residual current, bed stress, suspended sediment concentration, and sediment fluxes. Increasing the dredging depth and width increases the net sediment fluxes into the channel and dredging depth has a greater influence on the channel siltation thickness. When the dredging depth is 8.4 m or11.4 m, the average siltation thickness of the channel is 0.07 m or 0.15 m per mouth respectively. The parallel movement of the channel has small effects on the siltation volume during the simulation period. The sediment deposits in the channel primarily originates from the tidal flats, through bottom sediment fluxes. Vertical net circulation has a dominant impact on siltation because the difference of horizontal current of each layer on the longitudinal section of the channel increases, which intensifies the lateral sediment transport between the shoal and channel. The influence of vertical frictional dissipation on the lateral circulation at the feature points accounts for more than 50% before dredging, while the non-linear advective term is dominant after dredging. Tidal pumping mainly affects the longitudinal sediment fluxes in the channel. These results can be used for channel management and planning for similar estuaries worldwide.

悬浮区对竖流沉淀效果影响研究

竖流沉淀依靠絮体自然沉淀和悬浮区拥挤沉淀实现固液分离,适度絮凝能充分发挥二者的协同作用,降低药剂投加量,提高沉淀效果。为了明确悬浮区的作用,开展了连续流竖流沉淀试验,考察测试不同工况下絮体的形态、悬浮区状态、沉淀效果等变化规律,重点分析了轻度絮凝、中度絮凝和重度絮凝3个典型的工况。结果表明:轻度絮凝的絮体自然沉降效能和悬浮区拦截效果均不佳;重度絮凝虽然絮体自然沉降效果好,但是悬浮区拦截效果较差;只有中度絮凝可以较好地平衡絮体自然沉降和悬浮区拦截的协同作用,沉淀效果最好,对应的絮体分型维数为1.83,密度为1.391 g/cm^(3),悬浮区高度为2.2 m左右。

海上高温高盐油藏层内沉淀深部调驱体系研究与应用

针对常规调驱体系因注入困难、耐温抗盐性差及价格昂贵,难以满足海上高温高盐油藏深部调驱需求的问题,研发出一种以Na_(2)SiO_(3)为主剂的层内沉淀深部调驱体系。通过化学分析、仪器检测和物理模拟等多种方法对体系进行了配方优化和性能评价。实验研究结果表明:调驱体系的最佳母液配方组成为7%硅酸钠+30%沉淀控制剂A+1.0%沉淀控制剂B,该配方可与现场注入水中的成垢离子反应生成粒径为67.0~123.1 nm的颗粒,在向地层深部运移过程中由小到大逐渐聚并成粒径为42.6~47.4μm的无机沉淀,封堵水窜通道最终实现深部液流转向。该调驱体系耐温150℃,在50~500 mD岩心均具有良好的注入性,沉淀后封堵率可达95.9%,对于渗透率级差为8~20的双岩心提高采收率幅度可达11.0%~16.4%。矿场试验表明,层内沉淀调驱体系注入性好、工艺简单,稳油控水效果显著,W油田A井组实施措施后日增油超25 m^(3),含水率平均下降13.3%,累计增油达到7675 m^(3)。技术对于海上高温高盐油田开发具有良好的示范作用。

咪唑啉类缓蚀剂在模拟沉积物层中的扩散行为研究

采用紫外-可见分光光度法(UV-Vis)和动电位极化曲线法研究了三种咪唑啉类缓蚀剂(SOIMS,SOIM和OIM)在模拟沉积物层中的扩散行为。通过SEM(扫描电镜)和压汞法试验对试验前后的模拟沉积物层进行了表征。UV-Vis法试验结果表明:缓蚀剂在溶液中的扩散行为与其水溶性密切相关,缓蚀剂的水溶性越好,其通过沉积物层的能力越强。UV-Vis法试验和动电位极化曲线试验结果表明:随着试验时间的增加,三种缓蚀剂均能通过模拟沉积物层。

利用低声速沉积层反射特性线性反演地声参数

为提高反演效率和降低地声参数耦合,提出一种线性反演低声速沉积层地声参数的方法。从类线性声速剖面的两层海底平面波反射系数出发,分析了全透射角及全透射角下最大反射损失、干涉条纹等反射特性与各相关地声参数的关系,并构建了相应的代价函数。结合敏感性分析和分步反演策略,分步反演了低声速沉积层地声参数。该方法适用于低声速沉积层声速梯度恒定的情况。利用新英格兰泥地实验部分海底反射损失数据进行了实验验证。实验反演结果与相关跨维反演结果基本一致,反演误差分别为声速比0.1%,密度比0.3%,吸收系数14.6%,声速梯度为15.8%。反演效果显示,该方法一定程度上规避了部分地声参数间的耦合,且可给出决定类线性声速剖面形状的幂次项的最佳估计。

海底原位分层声学测量模拟装置的设计与实验

【目的】为研究原位测量装置的测量特性和不同环境下海底沉积物声学特性的变化机制,设计一种海底原位分层声学测量模拟装置。【方法】装置主要由分层运动控制单元、声学测量单元和计算机控制单元三部分组成,通过电动缸对声学测量探杆进行定位运动与连续运动控制,实现对声学测量探杆运动精度分析。通过在水中进行测量标定,获得装置声学测量探杆的校正距离差和扩散衰减系数。通过模拟原位分层声学测量实验,实现不同类型海底沉积物的声学特性测量。【结果与结论】声学测量探杆的校正距离差为77.14 mm,此装置发射声波的平均扩散衰减系数为(34.30±0.46)dB/m。声学测量探杆运动控制精度高,能准确运动到不同层中进行声学特性分层测量,定位测量和连续测量两种测量方式都能获得稳定的实验数据。

Interaction between internal solitary waves and the seafloor in the deep sea

Internal solitary wave(ISW),as a typical marine dynamic process in the deep sea,widely exists in oceans and marginal seas worldwide.The interaction between ISW and the seafloor mainly occurs in the bottom boundary layer.For the seabed boundary layer of the deep sea,ISW is the most important dynamic process.This study analyzed the current status,hotspots,and frontiers of research on the interaction between ISW and the seafloor by CiteSpace.Focusing on the action of ISW on the seabed,such as transformation and reaction,a large amount of research work and results were systematically analyzed and summarized.On this basis,this study analyzed the wave–wave interaction and interaction between ISW and the bedform or slope of the seabed,which provided a new perspective for an in‐depth understanding of the interaction between ISW and the seafloor.Finally,the latest research results of the bottom boundary layer and marine engineering stability by ISW were introduced,and the unresolved problems in the current research work were summarized.This study provides a valuable reference for further research on the hazards of ISW to marine engineering geology.

超厚特细砂层中超深地下连续墙的沉渣控制方法研究

针对在超厚砂层中进行地下连续墙施工时沉渣过厚的问题,以上海轨道交通市域线机场联络线上海浦东国际机场站工程为依托,对超深地下连续墙成槽施工过程中的沉渣控制方法进行研究。通过对沉槽施工过程中的新拌泥浆配比、成槽用时、清基换浆用时等各项施工数据进行全过程总结研究,探索出一套超深地下连续墙在超厚砂层中槽段施工沉渣效果控制比较好的方法,以期为后续类似项目提供借鉴。

长江口徐六泾站垂线含沙量代表层研究

在水深大、交通繁忙而无法开展传统六层采样测量的情况下,如何获取更为准确的垂线平均含沙量进而提升入海泥沙通量的测量精度是当前学者关注的重点。以长江口入海观测关键节点——徐六泾水文断面为例,采用多种分层组合的方法计算垂线平均含沙量,运用置信区间、平均相对误差以及Lilliefors假设检验等统计方法进行计算与分析;同时,结合观测节点上下游水文断面数据,分析了垂线平均含沙量代表层的表征规律。研究结果表明:虽然徐六泾水文断面受到径-潮流相互作用,但0.6 H层被证实是最佳的垂线平均含沙量代表层,其平均相对误差均值在(0±5)%范围内;然而在下游南支河段,白茆沙水文断面受潮汐动力的影响显著增大,从而导致0.6 H单层代表性较差。研究成果对未来水文综合浮标改造和准确获取长江入海泥沙通量具有重要指导意义。

合水地区长6_(3)深水重力流沉积特征研究

合水地区是鄂尔多斯盆地近年来原油勘探的重点区块,在系统分析沉积构造、岩石学特征、结构粒度特征等沉积相识别标志的基础上,结合区域沉积背景,开展了合水地区长6_(3)重力流沉积类型及展布特征研究。结果表明,合水地区长6_(3)油层亚组为湖泊-重力流沉积体系,发育半深湖-深湖沉积亚相,可进一步划分为浊流沉积、砂质碎屑流、滑塌沉积三种重力流沉积类型;其中砂质碎屑流及浊流为主要控砂微相,主要分布在研究区的中部、南部区域,为区内有利储集相带。

赤道印度洋中部沉降颗粒物的季节变化特征及调控机制研究

基于2020年1—12月在赤道印度洋中部海域获取的沉积物捕获器时间序列样品,分析了沉降颗粒物与颗粒有机碳(particulate organic carbon,POC)通量的季节变化特征,并结合卫星遥感、数值模式及再分析数据探究上层物理过程对生物泵输出通量的调控作用。结果表明,2020年赤道印度洋中部海域的沉降颗粒物总通量与颗粒有机碳通量的变化范围分别为4.57~35.75 mg/(m^(2)·d)[(18.94±10.18)mg/(m^(2)·d)]和0.27~2.97 mg/(m^(2)·d)[(1.09±0.66)mg/(m^(2)·d)],两者均呈现显著的季节变化特征。总体上,1—3月、6月和9—11月呈现出3个显著的高通量事件。通过分析发现混合层深度变化与营养盐跃层波动的耦合作用可能是调控中深层通量变化的主要原因。与此同时,西南季风流(Southwest Monsoon Current,SMC)与赤道Wyrtki急流生消也可能通过改变温跃层或营养盐跃层深度对沉降颗粒物通量强度和季节变化起调控作用。