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891.
冲绳海槽轴线地质特征 总被引:10,自引:2,他引:10
冲绳海槽位于东海大陆架与琉球岛弧之间,海槽中发育着一系列平行轴向延伸的地堑型正断层。穿越海槽的地震剖面证实了海槽扩张中心的存在,扩张轴沿海槽轴线方向延伸。由于地堑构造中心的扩张速率较大,由某引起的海槽中心下陷的速率大于沉积作用的补偿速率,使海槽中心海底出现明显的下陷。在轴线的大陆坡一侧,陆源沉积占绝对优势;轴线的岛坡一侧,以火山坡碎屑、浮岩、有孔虫软泥为沉积特征。 相似文献
892.
根据垂向二维悬沙扩散方程和谢才公式,假定泥沙垂向扩散系数为常数或为水深和摩阻流速的函数时,从理论上推导得到一个新的不仅适用一般水域,也适用于高含沙水域的挟沙力公式。公式一阶近似形式上与近岸海域常用的刘家驹公式相一致也不显含泥沙沉速,从理论上证明了刘家驹公式的合理性,说明其经验公式在理论上也成立。对更高阶近似,公式显含泥沙沉速,与维利卡诺夫以及张瑞瑾等挟沙力公式相一致,说明了张瑞瑾公式的合理性。分析了导出的公式的物理意义以及与刘家驹公式和张瑞瑾公式的异同。新的挟沙力公式也表明挟沙力公式的近似应是流速平方的多项式,选择低阶项作为近似会有一定的误差。 相似文献
893.
CheeKongYap AhmadIsmail SoonGuanTan 《湿地科学》2005,3(2):94-103
1INTRODUCTION Studiesonheavymetalcontaminationinsedi mentshavealwaysbeenfocusedonthecoastalandin tertidalareas(Sivalingam,etal.,1980;Ismail,1993;Ismail,etal.,1993;IsmailandRosniza,1997;Yap,etal.,2002a,2002b).Theheavymet alconcentrationsfoundinthesediments… 相似文献
894.
The change in community diversity and structure of the indigenous, dominant, polycyclic aromatic hydrocarbon (PAH)-degrading bacterial genera, Sphingomonas and Mycobacterium, due to contamination in the environment is not very well known. A combination of PCR-DGGE with specific primers and a cultivation-dependent microbiological method was used to detect different populations of Sphingomonas and Mycobacterium in mangrove sediments. The structure of the entire bacterial community (including Sphingomonas) did not show a shift due to environmental contamination, whereas the diversity of Mycobacterium populations in mangrove sediments with higher PAH contamination increased from exposure between Day 0 and Day 30. The isolated Mycobacterium strains migrated to the same position as the major bands of the bacterial communities in Mycobacterium-specific DGGE. A dioxygenase gene system, nidA, which is commonly found in PAH-degrading Mycobacterium strains, was also detected in the more highly contaminated sediment slurries. The present study revealed that Mycobacterium species were the dominant PAH-degraders and played an important role in degrading PAHs in contaminated mangrove sediments. 相似文献
895.
An investigation has been conducted to identify the key parameters that are likely to scale laboratory sediment deposits to the field scale. Two types of bed formation were examined: one where sediment is manually placed and screeded and the second where sediment is fed into a running flume. This later technique created deposits through sequential cycles of sediment transport and deposition. Detailed bed surface topography measurements have been made over a screeded bed and three fed beds. In addition, bulk subsurface porosity and hydraulic conductivity have been measured. By comparing the four beds, results revealed that certain physical properties of the screeded bed were clearly different from those of the fed beds. The screeded bed had a random organization of grains on both the surface and within the subsurface. The fed beds exhibited greater surface and subsurface organization and complexity, and had a number of properties that closely resembled those found for water‐worked gravel beds. The surfaces were water‐worked and armoured and there was preferential particle orientation and direction of imbrication in the subsurface. This suggested that fed beds are able to simulate, in a simplified manner, both the surface and subsurface properties of established gravel‐bed river deposits. The near‐bed flow properties were also compared. It revealed that the use of a screeded bed will typically cause an underestimation in the degree of temporal variability in the flow. Furthermore, time‐averaged streamwise velocities were found to be randomly organized over the screeded bed but were organized into long streamwise flow structures over the fed beds. It clearly showed that caution should be taken when comparing velocity measurements over screeded beds with water‐worked beds, and that the formation of fed beds offers an improved way of investigating intragravel flow and sediment–water interface exchange processes in gravel‐bed rivers at a laboratory scale. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
896.
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898.
依据2011年3月4日对胶州湾走航连续实测所得pCO2数据,结合水文、化学和生物等要素的同步实测资料,对胶州湾海域pCO2分布及其影响因素进行了初步探讨,并估算了3月海-气CO2通量。结果表明:3月胶州湾表层海水pCO2实测值在191~332μatm之间,平均值为278μatm,海-气CO2通量在-22.76~-7.13mmol·m-2·d-1,平均值为-14.2mmol·m-2·d-1,这一时期胶州湾从大气吸收约1.59×103t C,表现为大气CO2的强汇。生物活动是影响这一时期表层海水pCO2分布的主要原因。 相似文献
899.
根据2015年6月莱州湾西南部海域5个站位大小潮25 h海流连续同步观测及悬浮泥沙取样资料,分析了研究区悬浮泥沙浓度的时空变化规律;结合通量机制分解法,研究了悬浮泥沙输运机制,并探讨了悬浮泥沙浓度变化的影响因素。结果表明,莱州湾西南部海域悬浮泥沙浓度整体具有由北向南逐渐减小、由表层向底层逐渐增加的趋势;底层悬浮泥沙浓度在涨、落急时段出现峰值;潮周期内悬浮泥沙输运表现出不对称性,并且平流输运在悬浮泥沙输运中起到主导作用;水动力是影响悬浮泥沙浓度变化的主要因素,悬浮泥沙浓度与流速变化基本呈正相关关系,但浓度峰大多滞后流速峰1~2 h。 相似文献
900.