Wave-induced Maintenance of Suspended Sediment Concentration during Slack in a Tidal Channel on a Sheltered Macro-tidal Flat,Gangwha Island,Korea

A field campaign was conducted to better understand the influence of wave action, in terms of turbulence and bed shear stress, on sediment resuspension and transport processes on a protected tidal flat. An H-frame was deployed in a tidal channel south of Gangwha Island for 6 tidal cycles during November 2006 with instrumentation including an Acoustic Doppler Velocimeter, an Acoustic Backscatter System, and an Optical Backscatter Sensor. During calm conditions, the current-induced shear was dominant and responsible for suspending sediments during the accelerating phases of flood and ebb. During the high-tide slack, both bed shear stress and suspended sediment concentration were reduced. The sediment flux was directed landward due to the scour-lag effect over a tidal cycle. On the other hand, when waves were stronger, the wave-induced turbulence appeared to keep sediments in suspension even during the high-tide slack, while the current-induced shear remained dominant during the accelerating phases of flood and ebb. The sediment flux under strong waves was directed offshore due to the sustained high suspended sediment concentration during the high-tide slack. Although strong waves can induce offshore sediment flux, infrequent events with strong waves are unlikely to alter the long-term accretion of the protected southern Gangwha tidal flats.     

Field investigation of siltation at a tidal harbor: North Port of Incheon,Korea

Ocean Dynamics - To understand siltation processes within the North Port of Incheon, Korea, this study estimated the sedimentation rate and then determined the dominant mechanisms for the...     

Dynamics of fluid and heat flow in a CO2-based injection-production geothermal system

CO2 is now considered as a novel heat transmission fluid to extract geothermal energy. It can be used for both energy exploitation and CO2 geological sequestration. Here, a 3-D, “two-spot” pattern well model is developed to analyze the mechanism of CO2-water displacement and heat extraction. To obtain a deeper understanding of CO2-geothermal system under some more realistic conditions, heterogeneity of reservoir’s hydrological properties is taken into account. Due to the fortissimo mobility of CO2, as long as the existence of highly permeable zone between the two wells, it is more likely to flow through the highly permeable zone to reach the production well, even though the flow path is longer. The preferential flow shortens circulation time and reduces heat-exchange area, probably leading to early thermal breakthrough, which makes the production fluid temperature decrease rapidly. The analyses of flow dynamics of CO2-water fluid and heat may be useful for future design of a CO2-based geothermal development system.     

初始矿物组分对CO_2矿物储存影响的模拟研究

二氧化碳地质封存(CO2geological sequestration,CGS)是一种直接、高效的减少大气中CO2含量的方式。本文以鄂尔多斯盆地CGS示范工程场地刘家沟组实测数据为基础,利用数值模拟方法,研究储集层岩石初始矿物组分变化对CO2矿物封存能力的影响。结果表明,在长石为主的砂岩储集层中,绿泥石、方解石和长石类矿物是主要的溶解矿物,铁白云石是主要的固碳矿物,初始矿物中钾长石、方解石含量变化对矿物封存量的影响极小,奥长石含量对矿物封存量有一定程度的影响,而绿泥石初始含量显著影响矿物封存量。     

Evaluation of ADCP backscatter inversion to suspended sediment concentration in estuarine environments

Acoustic Doppler Current Profilers (ADCP), designed for measuring velocity profiles, are widely used for the estimation of suspended sediment concentration from acoustic backscatter strength, but its application to estuarine environments requires further refinement. In this study, we examined the inversion capability of two ADCPs with 600 and 1200 kHz in three Korean estuaries: the supra-macrotidal Han River Estuary (HRE), microtidal Nakdong River Estuary (NRE), and anthropogenically altered macrotidal Yeongsan River Estuary (YRE). In particular, we examined the relative importance of the sound attenuations due to water (α_w) and sediment (α_s) in response to sediment characteristics (size and concentration) as well as changing salinity and temperature. The inverted concentration was compared with reference concentrations obtained either from water samples or Optical Backscatter Sensors. In NRE and YRE, where suspended sediment concentrations were less than 0.2 g/l, the acoustic inversion performed poorly only with α_s (r = 0.20 and 0.38 for NRE and YRE, respectively), but well with α_w (r = 0.66 and 0.42 for NRE and YRE, respectively). Thus, it is important to accurately constrain α_w in low-concentration estuarine environments. However, we did not find that the varying α_w performed considerably better than the constant α_w. On the other hand, the acoustic inversion was poorest at HRE regardless of α_w and α_s (r = 0.71 and mean relative error = 45%). The large discrepancy appears to result from the poorly constrained, spatially and temporally varying sediment characteristics (grain size, density and concentration) due to non-local sediment transport in the macrotidal HRE.     

珠琼运动的厘定——来自北部湾盆地福山凹陷构造沉积特征的启示

南海北部盆地构造运动的认识向来存有争议,尤其是在珠琼运动的厘定上更是难以统一。通过分析南海及其周缘盆地的动力学背景特征,认为珠琼运动为发生在始新世至渐新世的一次大型伸展构造运动,根据其动力学背景可分为两幕。北部湾盆地福山凹陷在珠琼运动期间表现出明显的两期伸展背景,分别对应珠琼运动的两次幕式活动。根据福山凹陷沉降速率变化、控沉积断裂与不同期次断裂分布特征,认为珠琼运动一幕的活动时间为早—中始新世,即54~39.4Ma,动力学机制为印度洋板块俯冲欧亚板块引起东南方向的地幔流并导致太平洋板块俯冲后退;珠琼运动二幕的活动时间为晚始新世至渐新世,即39.4~25.5 Ma,起因于海南地幔柱柱头到达岩石圈底部引起东南方向的伸展效应。     

微波消解-电感耦合等离子体质谱测定玉米中铬、镉、铅

研究了微波消解-电感耦合等离子体质谱（ICP-MS）测定玉米中重金属元素的方法。详细讨论了微波样品溶液制备、质谱仪干扰扣除及校准等,在优化的试验条件下,根据国家标准参考物质（GBW10012）的分析结果评价方法的准确性。方法检出限为：Cd：0.003μg/g,Cr：0.04μg/g,Pb：0.1μg/g,相对标准偏差在2.5%-6.0%之间,加标回收率在90.9%-104.9%之间。