Influence of submarine fumaroles on the distribution of mercury in the sediment of Kagoshima Bay,Japan     

Takashi Tomiyasu  Tomomi Eguchi  Masahiko Yamamoto  Katsuro Anazawa  Hayao Sakamoto  Tetsuo Ando  Munetomo Nedachi  Katsumi Marumo 《Marine Chemistry》2007

To estimate the influence of mercury emitted from submarine fumaroles, the horizontal and vertical distribution of mercury in sediment of Kagoshima Bay was studied. The fumaroles are located in the northern bay head area, and the sediment samples had been taken from 52 points throughout the bay with a gravity core sampler. The core samples obtained were cut at a thickness of 1–2 cm and used for measurements. The total concentration of mercury in surface sediment in the northern and central areas of the bay was 51–679 μg kg^− 1 (average 199 μg kg^− 1, n = 22) and 23–100 μg kg^− 1 (average 55 μg kg^− 1, n = 30), respectively. The highest value was obtained in the vicinity of the fumaroles. The mercury concentration in sediment near the fumaroles varied with depth, which may reflect the variation in fumarolic activity. A successive extraction method was applied to the speciation of mercury in the sediment. The results showed that sediment taken in the vicinity of submarine fumaroles contained a higher percentage of mercury bound with organic matter.  相似文献   

On the behaviour of liquefied soil   总被引：1，自引：0，他引：1  

Andrzej Sawicki  Jacek Mierczyński 《Computers and Geotechnics》2009

Engineering mechanics of liquefied soil is presented. Firstly, experimental methods and their results are described in order to show that liquefied soil can be approximated as a viscous fluid. The experiments proposed allow for determination of dynamic viscosity of liquefied soil, which is of the order of 10⁶ Ns/m². This value agrees with some theoretical estimates. Then, the model of viscous fluid is applied to practically important problems, in order to predict sinking of structures in liquefied subsoil, and to describe underwater flows of seabed. Enclosed examples show that the model and methods proposed lead to realistic results and, therefore, can be applied in engineering calculations.  相似文献   

海底浅表层信息声探测技术研究现状及发展   总被引：8，自引：0，他引：8  

吴自银  郑玉龙  初凤友  陶春辉  高金耀 《地球科学进展》2005,20(11):1210-1217

回顾了我国海洋仪器研发的历史,综述并对比了多波束测深、侧扫声呐和浅层剖面仪等海底浅表层信息声呐探测技术的国内外研究现状:经过数十年的海洋技术研发,国内在设备研发、数据资料处理方法研究和探测数据资料应用研究等方面已取得了较丰硕的研究成果,但同时也发现在当前国内海洋技术研发中仍存在一些潜在的问题,与国外相关海洋技术尚存在一定差距。以维护海洋权益为目标的系列重大海洋基础勘测项目的启动和深海资源勘查及研究的纵深发展是近年海洋技术得以快速发展的源动力。声学底质分类、声学海底原位测试、动力地貌和构造地貌等是目前海底浅表层声探测信息资料应用于海底科学研究的热点。对海洋技术的可持续发展提出了几点建议：①提高理论研究水平;②加快仪器设备研制的国产化进程;③加强自主知识产权数据处理软件的研发;④进行探测数据资料的深层次利用研究。  相似文献   

Current Status of Scientific Deep-diving Investigations in Submarine Canyons     

Guangfa Zhong 《地球科学进展》2019,34(11):1111-1119

Submarine canyons represent one of the most important geomorphologic features in continental margins, act as one of the most important conduits of seafloor sediment transporting from shallow waters into the deep sea, and are also biodiversity hotspots. Submarine-canyon investigations are therefore significant for seafloor scientific research, submarine mineral and resource exploitation, and the construction and safety operation of submarine infrastructures. Deep-sea diving by manned submersibles and robot submersibles represented by Remotely Operated Vehicles (ROV) and Autonomous Underwater Vehicles (AUV) provides an important approach to the investigation of modern submarine canyons. The biggest advantage of manned submersibles is that they can bring scientists to the deep sea for in-place observations and precise sampling, while the robot deep-sea diving has the advantages of low cost, high efficiency, no personnel safety concerns, and the ability to reach the extreme sea areas that are difficult for humans to reach. Deep-sea diving has found broad applications in the geo-scientific research of submarine canyons. These studies cover seafloor topography and geomorphology, seafloor sediments, erosional and depositional bedforms, mass transport processes and flow dynamics, cold springs, cold-water corals and other biological habitats, as well as seafloor biological erosion. The research experience and scientific findings in scientific diving investigation of submarine canyons accumulated by the developed countries in Europe and the United States over the past 70 years are of great reference and significance to the emerging scientific deep-sea diving in China.  相似文献   

Submarine Hydrothermal Mineralization on the Izu-Bonin Arc, South of Japan: An Overview     

G. P. Glasby  K. Iizasa  M. Yuasa  A. Usui 《Marine Georesources & Geotechnology》2000,18(2):141-176

Considerable effort has been expended in studying the Izu-Bonin Arc over the past 15 years. In particular, 43 dives of the Shinkai 2000 have been undertaken there to discover and evaluate the extent of submarine hydrothermal activity and mineraliza tion. Most effort has been focused on Myojin Knoll (23 dives), Suiyo Seamount (6 dives), and Kaikata Caldera (10 dives). The Izu-Bonin Arc is divided in two by the Sofugan Tectonic Line. Eight submarine caldera are located north of this line but only one is south of it. The physiography of the northern sector of the arc is quite different from that of the southern sector. Volcanic rocks from the northern sector are more acidic than those from the southern sector. Evidence for submarine hydrothermal mineralization has been observed at four seamounts along the Izu-Bonin Arc (Myojin Knoll, Myojinsho, Suiyo Seamount, and Kaikata Caldera), and submarine hydrothermal activity is evident at another three seamounts along the arc (Kurose Hole, Mokuyo Seamount, and Doyo Seamount). The most extensive submarine hydrothermal mineral deposit so far located on the Izu-Bonin Arc is the Sunrise deposit at Myojin Knoll. This deposit, at least 400 m in diameter and 30 m high, is associated with black smoker venting, inactive sulfide chimneys, massive sulfides, hydrothermal Mn crusts, and a hydrothermal vent fauna. The maximum recorded temperature of the hydrothermal vents there was 278°C. Some of the sulfide chimneys contained as much as 49 μg / g Au and 3,400 μg / g Ag. The sunrise deposit is one of the largest submarine volcanic massive sulfide deposits so far discovered in midocean ridge, backarc, or arc settings and has an estimated mass of 9 x 10 6 t. This deposit may be of the Kuroko-type. The discovery of the Sunrise deposit in 1997 gives hope that other, similarly large, sulfide deposits may be found in other caldera along the Izu-Bonin Arc. The geological variability along the arc, the high seismicity, the occurrence of active volcanism and submarine hydrothermal venting, and a proven submarine hydrothermal mineral potential coupled with the proximity of the region to Japan suggest that the Izu-Bonin Arc could profitably serve as a natural laboratory for the long-term monitoring of the seafloor.  相似文献   

Submarine cables: a challenge for ocean management     

Scott Coffen-Smout  Glen J. Herbert 《Marine Policy》2000,24(6):1026

The international submarine cable industry is a major component of the global telecommunications system, providing important services and requiring increased levels of protection for the maintenance of global economic and maritime security, broadly defined. An overview is given of the submarine cable industry, including its technological developments, legal aspects, security considerations, and implications for integrated ocean planning and management. In the context of multiple ocean use, submarine cables can cause spatial conflicts with other ocean users, particularly the fishing industry. Issues to be examined include compensation for lost or damaged gear, legal liability for cable damage, and regulation and licensing of cables on the seabed of the continental shelf and the high seas. Recent industry-to-industry agreements and programs for compensation to fishers in the USA and Canada are significant advancements in the implementation of integrated approaches to ocean management and planning. The development of transparent and stable interdepartmental processes for the coordinated planning, management and regulation of submarine cables is required for national EEZs. The regulation of international cable industry practices must be harmonized with national management approaches.  相似文献   

Wake II model for hydrodynamic forces on marine pipelines including waves and currents     

Said R. Sabag  Billy L. Edge  Iwan Soedigdo 《Ocean Engineering》2000,27(12)

The Wake II model for the determination of the hydrodynamic forces on marine pipelines is extended to include currents and waves. There are two main differences between the Wake II and the traditional model. First, in the Wake II model the velocity is modified to include the pipe's encounter with the wake flow when the velocity reverses. Second, the model uses time dependent drag and lift coefficients. The flow field is assumed to be the linear superposition of regular waves and uniform current and is treated as wave only but in two different phases. The model requires eight empirical parameters that are obtained from comparisons with field data for various Keulegan–Carpenter numbers and current to wave ratios. The effective velocity and the force predictions are compared with field data from Exxon Production Research Company and with the conventional model. The model gives satisfactory results and predicts lift forces that in shape, magnitude and phase relative to the velocity are in very close agreement with measured forces. For the horizontal forces the results are very accurate. A substantial improvement is obtained over the predictions with the conventional model. This work is applicable to the design of submarine pipelines laying on the sea bottom in water depths where waves or waves and currents contribute to the hydrodynamic forces.  相似文献   

南海北部沙波运移的观测与理论分析   总被引：3，自引：0，他引：3       下载免费PDF全文

林缅  范奉鑫  李勇  阎军  江文滨  龚德俊 《地球物理学报》2009,52(3):776-784

针对南海北部海域特点建立了模拟该区域小尺度沙波运移过程的准三维力学模型.以多波束海底地貌扫描数据和水文资料为基础,预测了研究区域沙波的运移,其结果在沙脊脊沟处与实际观测一致,而在脊背上与实际观测值存在差异.分析表明,本文所提出的物理模型可以用于预测南海海域以推移质泥沙运动为主的小尺度沙波运移规律.这一结果对该区域海底管线等工程设计是很有意义的.  相似文献   

Sumisu volcano,Izu-Bonin arc,Japan: site of a silicic caldera-forming eruption from a small open-ocean island     

Kenichiro Tani  Richard S. Fiske  Yoshihiko Tamura  Yukari Kido  Jiro Naka  Hiroshi Shukuno  Rika Takeuchi 《Bulletin of Volcanology》2008,70(5):547-562

Sumisu volcano was the site of an eruption during 30–60 ka that introduced ∼48–50 km³ of rhyolite tephra into the open-ocean environment at the front of the Izu-Bonin arc. The resulting caldera is 8 × 10 km in diameter, has steep inner walls 550–780 m high, and a floor averaging 900 m below sea level. In the course of five research cruises to the Sumisu area, a manned submersible, two ROVs, a Deep-Tow camera sled, and dredge samples were used to study the caldera and surrounding areas. These studies were augmented by newly acquired single-channel seismic profiles and multi-beam seafloor swath-mapping. Caldera-wall traverses show that pre-caldera eruptions built a complex of overlapping dacitic and basaltic edifices, that eventually grew above sea level to form an island about 200 m high. The caldera-forming eruption began on the island and probably produced a large eruption column. We interpret that prodigious rates of tephra fallback overwhelmed the Sumisu area, forming huge rafts of floating pumice, choking the nearby water column with hyperconcentrations of slowly settling tephra, and generating pyroclastic gravity currents of water-saturated pumice that traveled downslope along the sea floor. Thick, compositionally similar pumice deposits encountered in ODP Leg 126 cores 70 km to the south could have been deposited by these gravity currents. The caldera-rim, presently at ocean depths of 100–400 m, is mantled by an extensive layer of coarse dense lithic clasts, but syn-caldera pumice deposits are only thin and locally preserved. The paucity of syn-caldera pumice could be due to the combined effects of proximal non-deposition and later erosion by strong ocean currents. Post-caldera edifice instability resulted in the collapse of a 15° sector of the eastern caldera rim and the formation of bathymetrically conspicuous wavy slump structures that disturb much of the volcano’s surface.  相似文献   

Submarine groundwater discharge into the coast revealed by water chemistry of man-made undersea liquefied petroleum gas cavern   总被引：1，自引：0，他引：1  

Jin-Yong Lee  Byung Wook Cho 《Journal of Hydrology》2008,360(1-4):195-206

The occurrence of submarine groundwater discharge (SGD) as well as its supply of many nutrients and metals to coastal seawaters is now generally known. However, previous studies have focused on the chemical and radiological analysis of groundwater, surface seawater, shallow marine sediments and their pore waters, as well as the measurement of upward flow through the marine sediments, as end members of the discharge process. In this study, chemical and isotopic analysis results of marine subsurface waters are reported. These were obtained from deep boreholes of an undersea liquefied petroleum gas (LPG) storage cavern, located about 8 km off the western coast of Korea. The cavern is about 130–150 m below the sea bottom, which is covered by a 4.8–19.5 m silty clay stratum. An isotopic composition (δ²H and δ¹⁸O) of the marine subsurface waters falls on a mixing line between terrestrial groundwater and seawater. Vertical EC profiling at the cavern boreholes revealed the existence of a fresh water zone. An increase in the contents of ferrous iron and manganese and a decrease in levels of nitrate, bicarbonate and cavern seepage were recorded in August 2006, indicating a decreased submarine groundwater flux originating from land, mainly caused by an elevated cavern gas pressure. It is suggested in this study that the main source of fresh waters in the man-made undersea cavern is the submarine groundwater discharge mainly originating from the land.  相似文献