长江感潮河段潮波传播变化特征及影响因素分析

径潮相互作用是感潮河段水动力变化的典型特征,受其影响潮波传播具有明显的洪枯季及沿程变化。本文基于长江感潮河段天生港、江阴、镇江、南京、马鞍山及芜湖6个潮位站2002-2014年连续高低潮位资料及大通站月均流量数据,统计分析长江感潮河段潮波振幅衰减率、潮波传播速度及余水位坡度等传播特征值的洪枯季及沿程变化特征,并探讨这些潮波传播特征的变化规律及其主要影响因素。结果表明,潮波传播特征的洪枯季差异自上游至下游逐渐减小,其分界点位于天生港与江阴之间(其中,天生港和江阴站的多年平均洪枯季潮差差值约为0.01 m和-0.04 m);径流动力对潮波衰减的影响主要位于江阴以上河段,江阴以下河段主要受潮汐动力控制;径流驱动下余水位坡度引起的余水位及水深增加,导致潮波传播的有效摩擦减小,当流量超过某个阈值时潮波振幅衰减反而减弱,特别是上游马鞍山-芜湖段最为明显,统计结果表明该河段流量阈值约为33 000 m3/s。本文分析结果作为前人研究的重要补充,可为长江河口感潮河段径潮相互作用机制研究及河口治理等提供基础参考。     

渤海南部表层沉积的相特征

通过海上调查及实验室分析,查明渤海南部表层沉积物在结构类型、矿物组合、生物组分及沉积构造等相特征方面具有明显的分区性。渤海南部存在五种沉积相:黄河水下三角洲相、陆架盆地相、海湾相、潮流浅滩相及古滨岸相。黄河水下三角洲相从河口延至水深15—20米处,沉积速率很高,沉积物富含碎屑云母及CaCo_3。陆架盆地相的沉积为粉砂质粘土,具有生物扰动构造。     

长江水下三角洲的动力沉积

2002年9-10月在长江水下三角洲获取了163个表层样,综合粒度、有孔虫、介形类、有机碳以及CaCO3含量的资料表明,研究区明显分为两部分,即长江河口现代三角洲扣晚更新世末期三角洲。根据表层沉积物的粒度特征,现代水下三角洲可以分为以黏土质砂扣细砂为主的前缘斜坡区(A区)、以黏土质粉砂为主的前三角洲区(B区)扣以砂一粉砂一黏土为主的三角洲向陆架过渡区(C区),呈现较为明显的粒径细化趋势,有机碳与黏土含量呈现明显的正相关,CaCO3含量的变化不大,从Pejrup图可以看出现代三角洲从A区到C区的动力递减变化。晚更新世末期三角洲(D区)粒径较粗,有孔虫扣介形类的氧化壳含量较高,有孔虫扣介形类的丰度扣含量也较高,CaCO3的含量较高,与现代三角洲形成明显的对照。对比20世纪70年代和80年代的资料,近岸物质趋向粗化,北支水下沙脊发育,现代三角洲不断向外扩展,残留砂面积减少。50多年来河口来沙的减少已经引起整个现代三角洲物质粗化,现代沉积区沉降中心面积大幅度减少。     

Variations of the Kuroshio Axis South of Kyushu in Relation to the Large Meander of the Kuroshio

The characteristics of the Kuroshio axis south of Kyushu, which meanders almost sinusoidally, are clarified in relation to the large meander of the Kuroshio by analyzing water temperature data during 1961–95 and sea level during 1984–95. The shape of the Kuroshio axis south of Kyushu is classified into three categories of small, medium, and large amplitude of meander. The small amplitude category occupies more than a half of the large-meander (LM) period, while the medium amplitude category takes up more than a half of the non-large-meander (NLM) period. Therefore, the amplitude and, in turn, the curvature of the Kuroshio axis is smaller on average during the LM period than the NLM period. The mean Kuroshio axis during the LM period is located farther north at every longitude south of Kyushu than during the NLM period, with a slight difference west of the Tokara Islands and a large difference to the east. A northward shift of the Kuroshio axis in particular east of the Tokara Islands induces small amplitude and curvature of the meandering shape during the LM period. During the NLM period, the meandering shape and position south of Kyushu change little with Kuroshio volume transport. In the LM formation stage, the variation of the Kuroshio axis is small west of the Tokara Islands but large to the east due to a small meander of the Kuroshio. In the LM decay stage, the Kuroshio meanders greatly south of Kyushu and is located stably near the coast southeast of Kyushu. This revised version was published online in July 2006 with corrections to the Cover Date.     

闽江河口地区河道演变及其影响因素分析

比之传统的调查方法,利用遥惑技术进行岸线解译具有范围大、多时段、省时、省力以及快速等优点。根据多时相TM遥惑数据,对闽江河口地区岸线进行解译,结合20世纪60年代地形图和2001年海图,分析了河口地区河道演变情况．对河流岸线和浅滩变化进行对比分析,发现闽江口南部水道多呈淤积状态,北边水道则为弱侵蚀型岸线;南部水下浅滩有新发育,原有的浅滩面积有很大的扩展,北边水道变化较小;文章最后对河道演变的影响因素进行了初步的探讨。     

现代黄河三角洲滨浅海区的灾害地质

利用卫星遥感、测深、浅地层剖面及钻孔资料研究了黄河三角洲海岸及近海海洋灾害地质,编制了黄河三角洲海洋灾害地质图。黄河三角洲海岸灾害地质以海岸侵蚀为主,根据1976—2001年海岸的变化速率,可将海岸分为快速侵蚀海岸、中等程度侵蚀海岸、稳定海岸和淤积海岸四类,快速侵蚀海岸和中等程度侵蚀海岸长期以来遭受侵蚀。灾害地质因素有浅层气、灾害地貌、活动断层、海底滑坡、底辟、隆起脊、埋藏冲沟一古河道。浅层气主要分布在老黄河口附近渤海海底,近岸少见。浅层灾害地貌主要分布在三角洲前缘斜坡上的扰动区。扰动区位置在整个三角洲上变动明显,有向岸移动的趋势,斜坡坡度减小,扰动强度减弱。底辟除了发生在废弃三角洲侵蚀区外,还发生在三角洲外的渤海海底下部。隆起脊位于黄河口东部渤海海底,沿NE—SW方向发育,顺隆起脊发育活动断层。     

黄河三角洲河道沉积规律研究Ⅱ. 建林边滩沉积作用机理

通过对建林边滩沉积物粒度分布、粒度参数及水体流变性质的分析，阐述了黄河三角洲上河道水流属于牵引流范畴，与低含沙水流无本质上的差别，并探讨沉积物搬运和沉积的基本特征。     

黄河断流对三角洲油气开发环境的影响

黄河断流对三角洲海上油气开发环境的负面影响是显著的,对流域的国民经济可持续发展的影响更是巨大。黄河断流对整个流域海上开发环境的影响深远,解决起来是一个很大的系统工程。从1999年的情况看,由于各级领导重视和措施得当,黄河断流的状况已得到很大缓解,黄河断流已由先前百天以上减少到1999年只断流41d(利津站)。2000年至今,黄河尚未发生过断流。本文从许多学者的研究资料入手,讨论黄河断流对三角洲油气开发环境的影响。     

Detection of free gas and gas hydrate based on 3D seismic data and cone penetration testing: An example from the Nigerian Continental Slope

We present a new method to characterize free gas, gas hydrates and carbonate concretions occurrence which are considered as high-risk factors for sub-sea developments in the Niger delta. This method is based on the combination of 3D seismic data to the geotechnical site characterizations using piezocone CPTU tests (Cone Penetration Test with additional measurement of the pore water pressure). A special processing of the 3D seismic data has enabled the determination of the interval compressional velocity. Using the effective-medium theory, velocity anomalies (negative and positive) within the first 15 m were translated in gas hydrate and free gas distribution. The calibration of the P wave velocity anomalies was done thanks to in-situ geotechnical testing carried out during two oceanographic surveys (2003 and 2004). Comparison between in-situ testing, recovered cores and the prediction of the gas and the gas hydrate distribution based on the compressional wave velocity have shown that 3D seismic data is a valuable tool to identify heterogeneous areas but the use of the piezocone was essential to discriminate between gas hydrate occurrences and carbonate concretions' presence. Furthermore, in-situ compressional wave velocity (V_p) measurements have clearly demonstrated what it was suspected from the 3D seismic data, the co-existence in the study area between gas hydrate and free gas.