The sea bottom in front of a breakwater is scoured under the action of broken waves,and this will affect the stability of the breakwater.In this paper,the scours of sandy seabed in front of a breakwater under the acti...The sea bottom in front of a breakwater is scoured under the action of broken waves,and this will affect the stability of the breakwater.In this paper,the scours of sandy seabed in front of a breakwater under the action of broken waves are investigated experimentally.The depth and range of the scouring trough at the foot of a breakwater are studied,and the influence of open foundation-bed on scouring and depositing is also discussed.In order to apply the research results to practical projects,the scale of model sediment and the scale of scours and depositions are suggested.展开更多
Coastal erosion is an island-wide problem in Taiwan; about 80% of the island＇s sandy coastline had suffered from erosion over the past few decades. Historically, with the specific tectonic environment and rapid uplif...Coastal erosion is an island-wide problem in Taiwan; about 80% of the island＇s sandy coastline had suffered from erosion over the past few decades. Historically, with the specific tectonic environment and rapid uplifting rate, lots of sediment had been yielded and transported to the coastal area that resulted in an advancing shoreline. Taiwan economically moved from a developing country to a developed one; a lot of human intervention had been made along the island coast. These are the major factors on recent coastal erosion. Even actions such as building of stabilization structures may inadvertently increase erosion. Some intervention examples are chosen to address how human-induced change made the profound impact on coastal erosion in Taiwan. All the information serves to provide a better understanding of the coastal processes, and a better response to the erosion problem.展开更多
Study of the major Asian rivers discharge to the ocean reveals variations of their water discharges and sediment loads, and local characteristics of river sediment concentrations. On the basis of this, the Asian river...Study of the major Asian rivers discharge to the ocean reveals variations of their water discharges and sediment loads, and local characteristics of river sediment concentrations. On the basis of this, the Asian rivers fall into three regions, including Eurasia Arctic, East Asia, Southeast and South Asia Regions. The Eurasia Arctic Region is characterized by the lowest sediment concentration and load, while the East Asia Region is of the highest sediment concentration and higher sediment load, and the South-East and South Asia Region yields higher sediment concentration and highest sediment load.The sediment loads of these regions are mainly controlled by climate, geomorphology and tectonic activity. The Eurasia Arctic rivers with large basin areas and water discharge, drain low relief which consists of tundra sediment, thus causing the lowest sediment load. The East Asia rivers with small basin areas and lowest water discharges, drain extensive loess plateau, and transport most erodible loess material, which results in highest sediment concentration. The SE and South Asia rivers originating from the Tibet Plateau have large basin areas and the largest water discharges because of the Summer Monsoon and high rainfall influence, causing the highest sediment load.In Asia, tectonic motion of the Tibet Plateau plays an important role. Those large rivers originating from the Tibet Plateau transport about 50% of the world river sediment load to ocean annually, forming large estuaries and deltas, and consequently exerting a great influence on sedimentation in the coastal zone and shelves.展开更多
This paper presents the results of application of a 3D （three-dimensional） numerical model to study on MTZ （maximum turbidity zone） in the coastal zone of Mekong River Delta. In this study, a 3D system model with ...This paper presents the results of application of a 3D （three-dimensional） numerical model to study on MTZ （maximum turbidity zone） in the coastal zone of Mekong River Delta. In this study, a 3D system model with combination of hydrodynamics--wave and suspended sediment transport was set up and validated with measured data in the study area. Based on calculated scenarios for the flood and the dry season, the results have shown appearance of MTZs in the coastal zone of Mekong River with suspended sediment concentration prevalent of 0.04-0.07 kg·m^3 （the dry season） and 0.05-0.1kg·m^3 （the flood season）. The position and MTZs scale change with the interaction between fresh water and tidal oscillations. The MTZ occur more in the dry seasons compared to the wet season. The MTZs are prevalent located far away from estuaries about in 12-22 km （in the dry season）, and 5-15 km in the flood season.展开更多
Sediment cores （-40-100 cm） were collected at 12 locations in the western Bohai Bay, the Haihe River estuary, the Yongding River estuary and the Tianjin Harbor, China, during 24-26 July 2007, and analyzed for ^7Be a...Sediment cores （-40-100 cm） were collected at 12 locations in the western Bohai Bay, the Haihe River estuary, the Yongding River estuary and the Tianjin Harbor, China, during 24-26 July 2007, and analyzed for ^7Be and ^210pb activities. Due to localized hydrodynamic patterns and frequent disturbance from dredging activities, steady-state sedimentation features were not observed in this study. As demonstrated in the VBe and ^210pb profiles, the temporal and spatial variations of these radionuclides support a non-steady state depositional environment in the study area. By comparing ^7Be and ^210pb inventories in the sediments with those of the atmospheric source, we found that： 1） sediments dredged from the Tianjin Harbor or eroded from nearby estuarine and coastal areas are retained in the western Bohai Bay for relatively short intervals （several months）, as reflected in the relatively high ^7Be inventories in the western Bohai Bay; 2） over the long-term （years to decades）, ^210Pb inventories in the sediments imply that there is a net on-shore transport of sediments, and the sediments are mass-balanced in the entire study area. Overall, our results suggest that the sediments are retained in the estuaries and the western Bohai Bay despite local variability in sediment dynamics and disturbance due to human activities.展开更多
The biosurfactant produced by Candida sphaerica in a fermentor containing 5% vegetal oil refinery waste and 2.5% was tested in the removal of motor oil from soils and seawater. In kinetic assays, the isolated biosurfa...The biosurfactant produced by Candida sphaerica in a fermentor containing 5% vegetal oil refinery waste and 2.5% was tested in the removal of motor oil from soils and seawater. In kinetic assays, the isolated biosurfactant removed more than 86% of the motor oil adsorbed to clay, silty and sandy soils at the critical micelle concentration （CMC）. Static removal tests performed in glass columns demonstrated that the crude biosurfactant was able to remove 75% and 92% of the oil contained in clay and silty soil, respectively, whereas the isolated biosurfactant at its CMC removed 50% of the oil from sandy soil. In the washing of hydrophobic compound on a porous surface, the removal rate was 60%. The biosurfactant also proved to be efficient in detergency tests since the crude surfactant removed 41% of motor oil from contaminated cotton cloth. In tests carried out with seawater, the crude biosurfactant showed an oil spreading efficiency of 75% in both screening dispersion test and oil displacement efficiency methods. Regarding the swirling bottle test, the dispersion rate was 72% for the isolated biosurfactant at a concentration twice the CMC. The biosurfactant studied demonstrated potential for application as an adjuvant in biotechnological processes for environmental decontamination.展开更多
基金the National Natural Science Foundation of China!(No.599790 1 9)
文摘The sea bottom in front of a breakwater is scoured under the action of broken waves,and this will affect the stability of the breakwater.In this paper,the scours of sandy seabed in front of a breakwater under the action of broken waves are investigated experimentally.The depth and range of the scouring trough at the foot of a breakwater are studied,and the influence of open foundation-bed on scouring and depositing is also discussed.In order to apply the research results to practical projects,the scale of model sediment and the scale of scours and depositions are suggested.
文摘Coastal erosion is an island-wide problem in Taiwan; about 80% of the island＇s sandy coastline had suffered from erosion over the past few decades. Historically, with the specific tectonic environment and rapid uplifting rate, lots of sediment had been yielded and transported to the coastal area that resulted in an advancing shoreline. Taiwan economically moved from a developing country to a developed one; a lot of human intervention had been made along the island coast. These are the major factors on recent coastal erosion. Even actions such as building of stabilization structures may inadvertently increase erosion. Some intervention examples are chosen to address how human-induced change made the profound impact on coastal erosion in Taiwan. All the information serves to provide a better understanding of the coastal processes, and a better response to the erosion problem.
基金The Project is sponsored by the Chinese National Nature Science Foundation (49676288) Scientific Research Foundation for the Returned Overseas Chinese Scholars of the Ministry of Education of China and the Russian Foundation for Fundamental Research (Pr
文摘Study of the major Asian rivers discharge to the ocean reveals variations of their water discharges and sediment loads, and local characteristics of river sediment concentrations. On the basis of this, the Asian rivers fall into three regions, including Eurasia Arctic, East Asia, Southeast and South Asia Regions. The Eurasia Arctic Region is characterized by the lowest sediment concentration and load, while the East Asia Region is of the highest sediment concentration and higher sediment load, and the South-East and South Asia Region yields higher sediment concentration and highest sediment load.The sediment loads of these regions are mainly controlled by climate, geomorphology and tectonic activity. The Eurasia Arctic rivers with large basin areas and water discharge, drain low relief which consists of tundra sediment, thus causing the lowest sediment load. The East Asia rivers with small basin areas and lowest water discharges, drain extensive loess plateau, and transport most erodible loess material, which results in highest sediment concentration. The SE and South Asia rivers originating from the Tibet Plateau have large basin areas and the largest water discharges because of the Summer Monsoon and high rainfall influence, causing the highest sediment load.In Asia, tectonic motion of the Tibet Plateau plays an important role. Those large rivers originating from the Tibet Plateau transport about 50% of the world river sediment load to ocean annually, forming large estuaries and deltas, and consequently exerting a great influence on sedimentation in the coastal zone and shelves.
文摘This paper presents the results of application of a 3D （three-dimensional） numerical model to study on MTZ （maximum turbidity zone） in the coastal zone of Mekong River Delta. In this study, a 3D system model with combination of hydrodynamics--wave and suspended sediment transport was set up and validated with measured data in the study area. Based on calculated scenarios for the flood and the dry season, the results have shown appearance of MTZs in the coastal zone of Mekong River with suspended sediment concentration prevalent of 0.04-0.07 kg·m^3 （the dry season） and 0.05-0.1kg·m^3 （the flood season）. The position and MTZs scale change with the interaction between fresh water and tidal oscillations. The MTZ occur more in the dry seasons compared to the wet season. The MTZs are prevalent located far away from estuaries about in 12-22 km （in the dry season）, and 5-15 km in the flood season.
基金Supported by the New Jersey Sea Grant (No. 6560-0000, H. Feng)the Tianjin Science and Technology Committee (No. 06YFGHHZ01500)
文摘Sediment cores （-40-100 cm） were collected at 12 locations in the western Bohai Bay, the Haihe River estuary, the Yongding River estuary and the Tianjin Harbor, China, during 24-26 July 2007, and analyzed for ^7Be and ^210pb activities. Due to localized hydrodynamic patterns and frequent disturbance from dredging activities, steady-state sedimentation features were not observed in this study. As demonstrated in the VBe and ^210pb profiles, the temporal and spatial variations of these radionuclides support a non-steady state depositional environment in the study area. By comparing ^7Be and ^210pb inventories in the sediments with those of the atmospheric source, we found that： 1） sediments dredged from the Tianjin Harbor or eroded from nearby estuarine and coastal areas are retained in the western Bohai Bay for relatively short intervals （several months）, as reflected in the relatively high ^7Be inventories in the western Bohai Bay; 2） over the long-term （years to decades）, ^210Pb inventories in the sediments imply that there is a net on-shore transport of sediments, and the sediments are mass-balanced in the entire study area. Overall, our results suggest that the sediments are retained in the estuaries and the western Bohai Bay despite local variability in sediment dynamics and disturbance due to human activities.
文摘The biosurfactant produced by Candida sphaerica in a fermentor containing 5% vegetal oil refinery waste and 2.5% was tested in the removal of motor oil from soils and seawater. In kinetic assays, the isolated biosurfactant removed more than 86% of the motor oil adsorbed to clay, silty and sandy soils at the critical micelle concentration （CMC）. Static removal tests performed in glass columns demonstrated that the crude biosurfactant was able to remove 75% and 92% of the oil contained in clay and silty soil, respectively, whereas the isolated biosurfactant at its CMC removed 50% of the oil from sandy soil. In the washing of hydrophobic compound on a porous surface, the removal rate was 60%. The biosurfactant also proved to be efficient in detergency tests since the crude surfactant removed 41% of motor oil from contaminated cotton cloth. In tests carried out with seawater, the crude biosurfactant showed an oil spreading efficiency of 75% in both screening dispersion test and oil displacement efficiency methods. Regarding the swirling bottle test, the dispersion rate was 72% for the isolated biosurfactant at a concentration twice the CMC. The biosurfactant studied demonstrated potential for application as an adjuvant in biotechnological processes for environmental decontamination.
