福建安海湾表层沉积物粒度特征及其现代沉积过程分析

通过对福建安海湾表层沉积物的粒度分析和对比,应用系统聚类分析、粒径趋势模型和切应力计算公式,探讨了研究区粒度的分布特征、沉积环境分区、表层沉积物输运趋势及其影响因素.研究结果表明,研究区包括6种表层沉积物类型,以黏土质粉砂和粉砂为主,沉积物大体呈现自海湾两侧潮滩向潮汐通道变粗的分布趋势.表层沉积物粒度的分布特征与水动力条件和物质来源密切相关,湾口附近及湾内深槽内,细颗粒的沉积物被再悬浮带走,粗颗粒的含量增大;在湾内潮滩上,悬浮物质因水动力作用逐渐减弱发生分选沉降,形成向岸变细的横向分异.海湾外泥沙随潮流不断地向海湾东侧岸滩运移,海湾周边陆源来沙由湾顶部往湾口方向下泄,两者是导致表层沉积物出现明显的顺时针方向汇聚趋势的原因之一;表层沉积物的输运趋势、悬浮泥沙的输运、潮滩植被与湾口沙嘴的遮蔽效应共同影响了研究区内浅滩地形的形成和变化.研究区可分为四类沉积环境区,以潮滩和潮汐通道环境为主,不同沉积区内的粒度参数、粒级频率和敏感粒级均有差异,动力条件差异和不同物源的影响程度是现代沉积环境格局的主要影响因素.     

汕头近岸海域表层沉积物粒度特征及其输运趋势

对汕头近岸海域70个站位表层沉积物作了粒度分析和粒度参数计算,以探讨沉积物粒度分布特征。分析结果显示,研究区表层沉积物可划分为9种底质类型,以黏土质粉砂（YT）、砂质粉砂（ST）和砂-粉砂-黏土（S-T-Y）为主;砾、砂、粉砂和黏土的平均含量分别为1.4％,29.2％,51.0％,18.4％。平均粒径在0.12~7.30 之间变化,平均值为5.53 ;分选系数、偏态和峰态值的变化范围分别为0.50~2.94,-0.65~0.30和0.63~2.67,对应的平均值为1.82,-0.02和1.11。根据粒度分析结果,结合系统聚类方法和因子分析方法将研究区分为四类沉积区,分别代表不同的沉积环境,并应用GSTA模型分析了沉积物净输运趋势。结果显示,在汕头港水深＜10 m的海区,径流来沙和海域来沙有在榕江入海口和近岸汇聚的趋势;水深＞10 m的海区,沉积物呈现出明显的沿海岸线东北向输运的特征;在柘林湾,沉积物主要表现为弱的由海岸/海岛向海湾输运的特征。粒径趋势模型所揭示的这种沉积物输运格局与研究区的物源和水动力状况较好吻合,可为研究区港口建设和航道管理的决策提供参考资料。     

江苏王港潮间带表层沉积物特征及输运趋势

潮滩沉积物粒度参数可以用来反映沉积物沉积的水动力条件和沉积环境。根据对江苏王港潮间带采集的15 4个表层样品的粒度资料进行分析,结果表明,沉积物类型以粉砂为主;随着水动力环境由海向陆的减弱,沉积物粒度参数表现出有规律的变化趋势,即由岸向海粒径具有粗化趋势,分选变好,逐渐正偏并达到近对称。研究区与世界其他地区的潮滩在沉积特征上有较大差异,主要是由于沉积物来源、水动力环境及受生物作用的强弱程度不同所致。沉积物输运趋势分析显示,该地区沉积物输运主要受当地潮波特征、大型人工建筑物、地貌形态及生物作用的影响;在低潮线附近主要向西北方向输运,随着向陆地方向的延伸,沉积物由向西输运逐渐转变为向南输运。     

沉积物粒径趋势分析:原理与应用条件

长期以来,沉积学家尝试用粒度数据来识别沉积环境的类型或判定物质运动的方式,但只取得了部分成功。粒度参数还有一项可能的用途,即用其平面差异来获取物质输运信息。沉积学家将粒度参数的平面差异定义为“粒径趋势”,并建立了以“粒径趋势分析”为基础的定性物质输运模型。粒径趋势分析的基本科学问题包括:如何提取粒径趋势信息;如何确定含有物质输运信息的粒径趋势类型;粒径趋势分析的应用条件是什么。粒径趋势信息可通过粒径趋势矢量的定义及其各向异性显著性的检验而获得,而经验证据也显示,含有物质输运信息的粒径趋势类型是存在的。初步研究表明,粒径趋势分析应满足以下条件:粒径趋势矢量具有显著性;底质采样深度应代表同一时间尺度;平面采样间距应符合地统计法的规则;避免使用位于采样网格边缘上的采样点的粒径趋势矢量;沉积物样品应属于同一个输运体系或研究区处于堆积状态。但是,由于不同来源的物质混合、源区沉积物特征及变化、不同水动力条件下的物质输运、悬沙沉降、溶解态—颗粒态物质转换、物质输运动力的侧向分布等因素与粒径趋势形成之间的关系还不够明确,因此这些条件还不是完备的,这个问题的解决依赖于粒径趋势形成的过程和机制的进一步研究。     

长江口北槽沉积物的粒度特征和输运趋势探讨

基于长江口北槽沉积物样品的粒度分析结果,使用粒径趋势分析法,研究了北槽底质沉积物的分布特征和输运趋势。结果表明:北槽表层沉积物总体较细,沉积物组分以砂质粉砂和粉砂为主。北槽底床沉积物的总体分选性较差,偏态系数则处于极正偏和近对称之间;峰度系数小于1.8,为低峰态,频率曲线比较平缓。北槽深槽表层沉积物为双向输运,在低能环境下向陆搬运,在高能环境下向海搬运;北槽南边坡与深槽类似,而北槽北边坡表现为向陆搬运。在北槽深槽和南、北边坡出现输运差异,与它们所处的环境密切相关。     

粒度分析理论技术进展及其应用

粒度分析在区分沉积环境、判定物质输运方式、判别水动力条件和分析粒径趋势等方面具有重要作用。本文主要介绍粒径测试技术方法及其新进展,包括传统的直接测量法、筛析法、沉降法和以计算机为依托的激光粒度测试仪法;评述沉积物分类命名方法理论及其在区分沉积环境、判定物质输运方式和判别水动力条件等方面的应用,以及粒度分析在研究海洋环境中沉积物输运方向、即粒径趋势分析方面的重要作用。随着计算机技术的快速发展,粒度分析测试技术正朝向自动化和测试内容多样化方向发展,其在实践中的应用也将更加广泛。     

广西钦州湾外湾海域表层沉积物粒度特征及沉积环境

沉积物粒度特征是反映沉积作用、沉积环境和沉积动力条件的明显标志,为了解广西钦州湾外湾海域沉积环境,对研究区167组表层沉积物样品进行粒度测定,分析粒度参数特征并划分沉积物类型,运用Pejrup三角投图对研究区进行沉积动力环境分区,采用Gao-Collins粒径趋势分析法总结研究区表层沉积物的运移趋势。结果表明：研究区表层沉积物以粉砂和砂为主,分选系数差。Folk-Ward分类法的结果显示研究区表层沉积物类型共12种,以砂质粉砂、砂质泥和粉砂分布最广,分别占样品总数的22.16%、17.37%和14.97%。沉积动力分析显示研究区的沉积环境复杂,水动力整体表现出由湾口向外逐渐减弱的特征。粒径趋势分析表明研究区表层沉积物整体向湾口及潮流深槽(航道)方向运移。综合分析表明研究区的沉积环境主要受潮流、波浪及人类活动等的影响。研究成果可为港口建设、深水航道改扩建以及海洋牧场建设等提供科学参考。     

冲绳海槽南部沉积层序的粒度特征

对取自冲绳海槽南部的A2 3孔经前处理后的沉积物样品进行了粒度测试,探讨了陆源沉积层序的粒度特征。沉积物平均粒径、分选系数、偏态、峰态等粒度参数的变化显示出A2 3孔的沉积层序以 4 0 0cm为界可分为上、下两段,下段各参数稳定,代表了比较稳定的水动力条件的沉积环境;上段则波动较大,小规模浊流沉积频繁发育,暗示了不稳定的沉积环境。浊流层内粗粒与细粒组分含量及粒度分布的变化具有明显的规律性。通过分析A2 3孔陆源沉积层序的各沉积参数特征,认为冲绳海槽南部的沉积环境和动力在时间尺度上有较大的变化,东海陆架物质向南部海槽的输运可能是以峡谷为通道的重力作用引起的床底沉积作用为主。另外,对陆源碎屑和全样粒度结果的对比,显示了前处理方法对于海洋沉积物粒度分析的重要性.     

钙质碎屑对热带海滩砂粒度参数的影响分析

钙质碳酸盐碎屑是热带海滩沉积物的重要组成部分,其物理特性与海滩中的石英颗粒差异明显。对海南岛东部文昌铜鼓角两侧海湾海滩砂样采用除钙和不除钙两种预处理方法,使用Mastersizer 2000激光粒度仪和筛析法进行粒度分析,结果表明:除钙以后粒度频率曲线主体朝细偏,但在粒度频率曲线细尾(4~9)会新增一小峰;去钙前后粒度参数存在明显的线性相关,平均粒径、分选系数和偏态的相关系数依次降低;粒度参数的组合变化以“平均粒径变细、分选系数变好、偏态朝细偏”为主,但仍存在其他的组合变化;在对类似于铜鼓岭周边环境的海滩进行沉积物粒度分析及动力环境研究时,需要了解钙质碎屑含量和颗粒组成。     

中国海域表层沉积物分布规律及沉积分异模式

中国海域拥有宽广的大陆架，同时还有陆坡和深海盆，有众多河流入海并输入巨量的陆源物质，沉积物记录了海陆变迁、环流变化、海平面升降、物质输送和气候变化等环境信息。沉积物的粒度特征可以反映沉积动力、物质来源和搬运距离等，可以通过沉积物粒度组成、参数及各种图解来研究沉积环境的变化。前人对中国海域表层沉积物的粒度分布特征展开了大量的研究，取得了丰富的研究成果，但这些研究多集中在某一海域或区域，缺乏对整个中国海域的表层沉积物类型的宏观系统认识。本文基于中国地质调查局“1：100万海洋区域地质调查项目”获取了中国海域4300个海底表层沉积物样品，通过沉积物粒度分析，结合前人已发表资料，对中国海域表层沉积物的沉积类型特征、物质来源和运移模式等开展了系统的研究。本文把浅海和半深海沉积物按照含砾石和不含砾石主要划分出5个和7个沉积物类型，深海沉积物主要划分了9个沉积类型，研究结果表明：中国海域表层沉积物沉积类型多样、来源复杂，主要受控于物质来源、水动力条件和地形地貌的变化，在东部海域总体呈现“大江大河-宽缓陆架-残留慢速沉积”的条带状沉积分异模式，而在南部海域呈现的是“短源性河流-多类型陆架-重力流快速沉积”的环带状沉积分异模式。本文的结果对研究中国海域沉积物的宏观分布规律提供了基础资料，对理解海洋沉积动力过程具有重要意义，同时沉积物粒度的特征对海底砂矿分布也具有指示意义。     

Hydrographic surveys and sedimentation in Deep Bay,Hong Kong

Three hydrographic surveys were carried out in Deep Bay, which is located in the eastern part of Pearl estuary between Shenzhen, the most successful special economic zone of PRC, and Hong Kong. Data on current, size distributions of bottom sediment, suspended solids, and some water quality parameters were obtained. This information is of value for mathematical modeling of tidal circulation and sediment transport in the bay, and also useful in the planning of further development in this area. The sedimentation rate in Deep Bay was estimated by two different approaches, viz. comparison of historical navigation maps and²¹⁰Pb dating. Information obtained from the maps indicated that average sedimentation rate between 1898 and 1949 was about 8 mm/yr, while a 15 mm/yr figure was obtained from the²¹⁰Pb dating for recent years.     

A rapid procedure for the determination of thorium,uranium, cadmium and molybdenum in small sediment samples by inductively coupled plasma-mass spectrometry: application in Chesapeake Bay

This paper describes a rapid procedure that allows precise analysis of Mo, Cd, U and Th in sediment samples as small as 10 mg by using a novel approach that utilizes a “pseudo” isotope dilution for Th and conventional isotope dilution for Mo, Cd and U by ICP-MS. Long-term reproducibility of the method is between 2.5 and 5% with an advantage of rapid analysis on a single digestion of sediment sample and the potential of adding other elements of interest if so desired. Application of this method to two piston cores collected near the mouth of the Patuxent River in Chesapeake Bay showed that the accumulation of authigenic Mo and Cd varied in response to the changing bottom water redox conditions, with anoxia showing consistent oscillations throughout both pre-industrial and industrial times. Accumulation of authigenic U shows consistent oscillations as well, without any apparent increase in productivity related to anoxic trends. Degrees of Mo and Cd enrichment also inversely correlate to halophilic microfaunal assemblages already established as paleoclimate proxies within the bay indicating that bottom water anoxia is driven in part by the amount of freshwater discharge that the area receives.     

Investigation and numerical simulation of summer sedimentation in Jiaozhou Bay,China

In recent years, development activities have had a significant impact on the environment of the Jiaozhou Bay, China. To ensure the sustainable economic and social development of the Jiaozhou Bay area, it is necessary to strengthen corresponding control measures. The important prerequisite is to properly understand the environmental conditions laws of natural change, especially the dynamic processes of sediment and the characteristics of landform evolution. Based on the data of continuous observation at 6 stations in Jiaozhou Bay for 25 hours, the Hydrodynamic Eutrophication Model (HEM-3D) was used to simulate the sediment erosion and deposition. The results show that the maximum suspended sediment concentration in the sea area of Jiaozhou Bay is about 40 mg/L, which appears in the northwestern area of the bay top and the Cangkou watercourse area, and the low concentration is located in the area of the central Jiaozhou Bay towards the bay mouth. The suspended sediment is 6–10 mg/L. Affected by a decrease in seawater material, the direction of the prevailing current in the Jiaozhou Bay area is different from that of the sediment transport. The velocity of the flood current is higher than that of the ebb current. However, during flood tide, the flux of resuspended seafloor sediment outside and at the mouth of the bay is limited and cannot contribute significantly to the suspended sediment in the bay. During ebb tide, the resuspended sediment at the shallow-water bay head and the east and west sides spreads toward the bay mouth with the ebb current, although it extends beyond the bay through the bay mouth. The research results can provide scientific support for the Jiaozhou Bay project construction and environmental protection.     

强潮海湾近岸表层沉积物时空分布特征及水动力响应——以杭州湾北岸为例

沉积物粒度参数是表征其分布和输运特征的重要信息。根据2005年7月和2006年12月采集的167个表层沉积物样品以及收集到的实测水文资料,以杭州湾北岸为例,分析研究强潮海湾近岸表层沉积物的时空变异特征,同时在应用GSTA模型对沉积物进行输运趋势分析的基础上探讨该区域的泥沙来源,并通过掀沙计算分析表层沉积物对高能水动力环境的响应过程。结果表明:（1）杭州湾北岸表层沉积物普遍较细,以粉砂质粘土为主,在南汇、金山岸段存在两个砂质密集区,并且随动力条件的不同在由岸向海方向呈现出逐渐变细的粒度趋势;（2）表层沉积物粒度特征在洪、枯季亦存有差异,枯季较洪季存在普遍粗化现象;（3）GSTA模型结果显示该区域泥沙主要来源于上游岸段来沙和湾口海域来沙,此外局部区域之间的泥沙交换过程也是区域内泥沙平衡协调的重要途径;（4）潮流掀沙作用主要以南汇和奉贤水域为主,波浪掀沙作用范围基本覆盖研究区域的整个岸段,且波高为1.5 m（P=94.9%）以下的波浪掀沙作用对浅水区域的影响最为显著。     

Swell impact on reef sedimentary processes: A case study of the La Reunion fringing reef

Two surface‐sediment sampling campaigns were carried out in November and December 2003, before and after a strong swell event, in the back‐reef area of a microtidal fringing reef on the western coast of La Reunion, Indian Ocean. The spatial distributions of the mean grain size, sorting and skewness parameters are determined, and grain‐size trend analysis is performed to estimate the main sediment transport pathways in the reef. The results of this analysis are compared with hydrodynamic records obtained in the same reef area during fair weather conditions and during swell events. Sediment dynamics inferred from the hydrodynamic records show that significant sediment erosion and transport occur only during swell events and under strongly agitated sea states. Under normal wave conditions, there is a potential for onshore sediment transport from the reef‐flat to the back‐reef, but this transport is episodic and occurs principally during high‐tide stages. Sediment transport trends revealed by the grain‐size trend analysis method show onshore and alongshore low‐energy transport processes that are in agreement with the hydrodynamic records. The grain‐size trend analysis method also provides evidence of an offshore high‐energy transport trend that could be interpreted as a real physical process associated with return flow from the shore to the reef. The impact of swell on the reef sediment dynamics is clearly demonstrated by onshore and alongshore transport. Considering different combinations of the vector transport trends computed through the grain‐size trend analysis approach, more realistic and pertinent results can be obtained by applying an exclusive OR operation (XOR case) on the vectors. The main results presented here highlight a trend towards the accumulation of carbonate sands in the back‐reef area of the fringing reef. These sediments can only be resuspended during extreme events such as storms or tropical cyclones.     

Seafloor environmental changes resulting from nineteenth century reclamation in Mishou Bay, Bungo Channel, Southwest Japan

This study reconstructed environmental changes to the seafloor associated with reclamation in Mishou Bay, Bungo Channel, Japan, based on measurements of sediment grain size, organic matter and sulfur contents of surface sediments and data from sediment cores. Grain size within sediment cores from the middle of Mishou Bay decreased from the beginning of the 1800s to the 1900s. In contrast, a grain size profile from the river mouth shows a gradual increase in grain size up through the sediment core. These changes in grain size indicate a decrease in tidal current velocity within the middle of the bay and that the delta system is gradually prograding from the river mouth. Records of organic matter composition and sulfur contents indicate that the effect of the river on seafloor sedimentation became stronger during the nineteenth century. These changes are related to reclamation during the late 1700s and 1800s. The decrease in sea area resulting from reclamation probably led to a decrease in tidal prism and current velocity. It is likely that the increasing effect of river water on sedimentation is associated with reclamation-related progradation of the river delta system.     

人类活动影响下伶仃洋沉积格局演变特征

根据2016年伶仃洋128个表层沉积物粒度参数以及前人对伶仃洋表层沉积物的研究成果,结合Flemming沉积动力判别图解和粒径趋势分析模型（GSTA）,分析伶仃洋40年来的沉积格局演变特征,并探讨了人类活动在伶仃洋沉积格局演变中的作用。结果显示:1）2016年,伶仃洋表层沉积物中粉砂组分含量最多（56.67%）,黏土组分含量其次（26.08%）,砂含量最少（17.23%）,湾内表层沉积物总体较细,主要有砂、砂—粉砂—黏土、砂质粉砂、粉砂质砂和黏土质粉砂5种类型,各类型沉积物呈现斑块状分布。2）近40年来,伶仃洋表层沉积物的平均粒径、粒级组分的空间格局发生了显著变化,从之前的条带状分布变为斑块状分布,但沉积格局的剧烈演变主要集中于2004—2016年这十多年间,Flemming三角图分区变化显示出40年来伶仃洋沉积环境整体表现出动力增强的趋势。3）受人类大规模采砂影响,中滩区域原有的完整沉积中心被分散,分别向北和向南形成“两格局、三中心”的新型沉积模式,从而改变伶仃洋的沉积物源—汇过程。4）伶仃洋沉积物空间分布、沉积动力环境、运移趋势等特征的变化与采砂、航道浚深等人类活动有着密切的联系,反映出人类工程活动已成为影响伶仃洋沉积格局演变的重要因素。