Since most of the natural disasters in the Yellow River are caused by sediment,the study of sediment composition,erosion and transport law is a fundamental part of sediment management in the Yellow River.As a method o...Since most of the natural disasters in the Yellow River are caused by sediment,the study of sediment composition,erosion and transport law is a fundamental part of sediment management in the Yellow River.As a method of in-situ testing,shear wave detection can obtain physical parameters such as the shear modulus of sediment.This paper,based on the Biot–Stoll model,deduces the equations for calculating the reflection and transmission coefficients when a shear wave is incident at the interface between sediment layer,and analyzes the effects of frequency,incident angle and porosity on the reflection and transmission coeffi cients of shear waves,as well as the diff erences in the propagation characteristics of longitudinal and shear waves at the interface between sediment layer.The results indicate that the refl ection and transmission coeffi cients of shear waves are linearly related to the porosity of sediment,and the refl ection coeffi cient of shear waves increases with the increase of porosity.The incident angle has a great infl uence on the changes of the reflection and transmission coefficients of shear waves,especially near the critical angle,the coeffi cients change abruptly.The frequency has a great infl uence on the refl ection and transmission coeffi cients of shear waves only near the characteristic frequency of sediment,while deviation from the characteristic frequency,the infl uence is small.The research results have certain signifi cance for obtaining the physical parameters of sediment and analyzying the composition of the Yellow River sediment and its erosion law.展开更多
The concentrations, accumulation and sources of 15 polycyclic aromatic hydrocarbons （PAHs） had been studied or evaluated in the surface layer sediments of Taizhou Bay, China. It showed that the concentrations of PAH...The concentrations, accumulation and sources of 15 polycyclic aromatic hydrocarbons （PAHs） had been studied or evaluated in the surface layer sediments of Taizhou Bay, China. It showed that the concentrations of PAHs ranged from 85.4 to 167.6 ng/g （averaged 138.62 ng/g）, and the highest level was found in Jiao Jiang Dock. Percentages of 2-, 3-, 4-, 5- and 6-cyclic aromatic hydrocarbons were 7.8 %, 42.1%, 33.3 %, 9.6 % and 7.2 % respectively. The accumulation indices of PAHs ranged from 532.7 to 1068.9 （averaged 807.5）, and the index of Phenanthrene was the highest （122.7）, while that of Benzo （a） Pyrene was the lowest （2.7） among them. In Taizhou Bay, PAHs in surface layer sediments came mainly from coal burning, partly from direct pollution of petroleum hydrocarbons.展开更多
DDCl-1 type seismic profiler for deep sediment layers is a large scale marine survey equipment. Its penetrating strata depth may reach to 1 km. This equipment suits surveys for continental shelf,seafloor trench and ge...DDCl-1 type seismic profiler for deep sediment layers is a large scale marine survey equipment. Its penetrating strata depth may reach to 1 km. This equipment suits surveys for continental shelf,seafloor trench and geological structure under seafloor etc. It suits also geological environment surveys of seafloor resources.The working principle, block diagrams composition and echo signal processing characteristics are presented, and some typical strata profiles are shown.展开更多
A review of former studies on the onset of sediment movement under wave action reveals that the Shields criterion obtained in unidirectional steady flow can also be applicable to oscillatory unsteady flow when the bou...A review of former studies on the onset of sediment movement under wave action reveals that the Shields criterion obtained in unidirectional steady flow can also be applicable to oscillatory unsteady flow when the boundary layer is the same. In this paper, through comparison of different boundary layers in wave and steady flow conditions, a new criterion is presented which can be used to predict the threshold of sediment movement Linder wave action. The criterion curve shows good agreement with the experimental data.展开更多
A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above...A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above the seabed. Based upon the logarithmic-profile equation, the boundary layer parameters, i.e., u, z0 and C60, were obtained for 247 tidal flow velocity profiles. Around 90% of the profiles were logarithmic according to the critical correlation coefficient. Internal consistency analysis shows that these parameters derived by different methods are consistent with each other. In addition, the height of the bedforms observed is close to the seabed roughness lengths calculated from the velocity profiles, indicating that the boundary layer parameters obtained can reveal the conditions at the sediment-water interface on the intertidal flats. Suspended sediment concentrations were obtained from the 5 CTMS turbidity meters using laboratory and in-situ calibrations. The results show that the in-situ calibrated SSCs have a much higher accuracy than the laboratory calibrated ones. Calculation of suspended sediment fluxes on the intertidal flats, with a magnitude of 104 kg/m per spring tidal cycle, indicates that suspended sediment moves towards the northwest, which is reversal to the transport pattern controlled by the southward Northern Jiangsu Coastal Current in the sub-tidal zone and adjacent shallow waters.展开更多
In this paper, the study on the fine velocity structure of sedimental and basement layers along 4 deep seismic sounding profiles in the Three Gorges Region of the Changjiang River (Yangtze River) are presented...In this paper, the study on the fine velocity structure of sedimental and basement layers along 4 deep seismic sounding profiles in the Three Gorges Region of the Changjiang River (Yangtze River) are presented. The velocity of sedimental cover is larger in hills of western Hubei in the western profiles, the total thickness is about 0～0.3 km. However, it becomes thick in southern part of Zigui basin and Zushui river valley, about 5.0 km and 4.0 km thick respectively. The sedimental cover is very thick in Jianghan plains in the eastern profiles, about 5～8 km, and the velocity is lower. The velocity of basemental plane is greater than 6.0 km/s over the whole region. An interface can be divided within the sedimental layer, it is about 3～4 km deep in Jianghan plains, while it approximates to surface in other regions. The profiles are cut by faults in many positions. Where the faults pass, the velocity isopleth varies sharply, and the velocity is obviously low. The basement layer is characterized by high velocity and low gradient, there exist 3 high velocity anomalous zones within the layer, which are located at the west, south and east of Huangling Anticlinorium respectively. They are the upwelling materials of basalt magma with high velocity from deep crust. Perhaps, this process took place before formation of Huangling Anticlinorium. Its action produces the significant variation of basement plane depth and the correspondent development and action of faults.展开更多
The diffusive boundary layer （DBL） is the zone for matter exchange between surface water and aquatic sediments. To elucidate the influence of DBL on salt release from saline sediments to freshwater, two experiments ...The diffusive boundary layer （DBL） is the zone for matter exchange between surface water and aquatic sediments. To elucidate the influence of DBL on salt release from saline sediments to freshwater, two experiments with or without wind blowing were conducted. According to the experiments, a 3.5 cm DBL is formed above the smoothed sediments at a steady wind field and this thickness is greater than other studies. The observed flux of salt through the DBL is 6% larger than the calculated value from Fick＇ s first law. The results indicate that molecular diffusion is the dominant mechanism for salt transport through the DBL. The presence of DBL suppresses the hydrodynamic enhancement for matter exchange between sediments and overlying water. Therefore, salts in the sediments of a polder reservoir may influence the water quality chronically.展开更多
Tanlu fault zone(TLFZ)is the largest active fault zone in eastern China.It is characterized by complex tectonic evolution and multiple faults and marks the boundary between the North and South China blocks.An indepth ...Tanlu fault zone(TLFZ)is the largest active fault zone in eastern China.It is characterized by complex tectonic evolution and multiple faults and marks the boundary between the North and South China blocks.An indepth understanding of the distinct crustal structures of both parts of the TLFZ will provide valuable insights into the lithospheric and crustal thinning in eastern China,extensive magmatism since the Mesozoic,and formation mechanisms of metallogenic belts along the Yangtze River.In this study,a two-layer H-κstacking approach was adopted to estimate the thicknesses of the sediment and crystalline crust as well as the corresponding vP/vS ratios based on high-quality teleseismic P-wave receiver functions recorded by permanent and temporary stations in and around the TLFZ.The geological units in the study region were delineated,especially the crustal structures beneath extensive sedimentary basins on both sides of the TLFZ.The following conclusions can be drawn:(1)The crustal thickness in and around the TLFZ greatly varies depending on the segment.In the northern segment,the crust is relatively thin beneath the eastern part of the Songliao Basin,a broad uplift of the Moho can be observed,and the Moho descends from south to north.The crust below the central and southern segments becomes thinner from west to east.The thickness of the crust is less than 30 km toward the eastern side of the boundary between the Jiangsu and Anhui provinces,that is,significantly thinner than in other areas.In terms of the vP/vS ratios,high anomalies were detected in the central-southern segments of the TLFZ,indicating the upwelling of deep mantle magma via deep faults.(2)Positive isostatic gravity anomalies were observed in the eastern part of the northern segment of the TLFZ and in the eastern part of the Suwan segment.The crustal thickness is smaller than that obtained from the Airy model of isostasy.This suggests that the lower crust in this area may have experienced intensive transformation processes,which may be related to crustal thinning(caused by crustal extension)and the strong uplift of the mantle in eastern China.The isostatic gravity anomalies between the eastern and western parts of the TLFZ indicate that the fault zone plays a dominant role in controlling the development of the deep crustal structure.(3)Significant crustal thinning was observed beneath the eastern part of the boundary between the Jiangsu and Anhui provinces in the southern segment of the TLFZ,suggesting that this area is prone to lithospheric thinning of the North China Craton.Due to the subduction,compression,and retreat of the Paleo-Pacific Plate during the Yanshanian Period as well as the dehydration of subducting oceanic crust(within subduction zones),the asthenosphere and oceanic crust in eastern China partially melted,resulting in mantle enrichment.The basic magma from the mantle is accumulated at the base of the crust,leading to magmatic underplating.In areas with weak topography toward the east of the TLFZ,magma rises to the upper crust and surface,resulting in the enrichment of multiple metal deposits in this area.展开更多
Based on a wave bottom boundary layer model and a sediment advection-diffusion model, seven turbulence schemes are compared regarding their performances in prediction of near-bed sediment suspension beneath waves abov...Based on a wave bottom boundary layer model and a sediment advection-diffusion model, seven turbulence schemes are compared regarding their performances in prediction of near-bed sediment suspension beneath waves above a plane bed. These turbulence algorithm., include six empirical eddy viscosity schemes and one standard two-equation k-e model. In particular, different combinations of typical empirical formulas for the eddy viscosity profile and for the wave friction factor are examined. Numerical results are compared with four laboratory data sets, consisting of one wave boundary layer hydrodynamics experiment and three sediment suspension experiments under linear waves and the Stokes second-order waves. It is shown that predictions of near-bed sediment suspension are very sensitive to the choices of the empirical formulas in turbulence schemes. Simple empirical turbulence schemes are possible to perform equally well as the two-equation k-ε model. Among the empirical schemes, the turbulence scheme, combining the exponential formula for eddy viscosity and Swart formula for wave friction factor, is the most accurate. It maintains the simplicity and yields identically good predictions as the k-ε model does in terms of the wave-averaged sediment concentration.展开更多
An analytical model with essential parameters given by a two-phase numerical model is utilized to study the net boundary layer current and sediment transport under skewed asymmetric oscillatory sheet flows. The analyt...An analytical model with essential parameters given by a two-phase numerical model is utilized to study the net boundary layer current and sediment transport under skewed asymmetric oscillatory sheet flows. The analytical model is the first instantaneous type model that can consider phase-lag and asymmetric boundary layer development. The two-phase model supplies the essential phase-lead, instantaneous erosion depth and boundary layer development for the analytical model to enhance the understanding of velocity skewness and acceleration skewness in sediment flux and transport rate. The sediment transport difference between onshore and offshore stages caused by velocity skewness or acceleration skewness is shown to illustrate the determination of net sediment transport by the analytical model. In previous studies about sediment transport in skewed asymmetric sheet flows, the generation of net sediment transport is mainly concluded to the phase-lag effect.However, the phase-lag effect is shown important but not enough for the net sediment transport, while the skewed asymmetric boundary layer development generated net boundary layer current and mobile bed effect are key important in the transport process.展开更多
In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom bound...In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer （BBL）. Field observations were carried out in the northwest Caofeidian sea area in the Bohai Bay. Near 2 m isobath （under the lowest tidal level）, a tripod system was installed with AWAC （Acoustic Wave And Current）, ADCP （Acoustic Doppler Current Profilers）, OBS-3A （Optical Backscatter Point Sensor）, ADV （Acoustic Doppler Velocimeters）, etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt： 1） The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m^3 and the average value being 0.03 kg/m^3; 2） The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m^3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m^3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended load sediment concentration is mainly influenced by wave-induced sediment suspension.展开更多
The present study examines the morphological, physicochemical, and mineralogical specificity of clay sediments in the Hamakoussou Basin with the objective of exploring their potential applications. Field data collecti...The present study examines the morphological, physicochemical, and mineralogical specificity of clay sediments in the Hamakoussou Basin with the objective of exploring their potential applications. Field data collection was followed by a series of physicochemical and mineralogical tests on the clay samples. Results show that the clay layers, which range in thickness from 11 - 120 cm, exhibit gray, yellowish, or greenish colors. From a physicochemical perspective, these clay layers are found to be basic with a pH ranging from 8.5 for the higher Hama2 layer to 7.6 for the lower Hama1 layer. The sum of exchangeable bases (S) is medium to high with higher values in the Hama1 layer (53.45 meq/100g) and lower values in the Hama3 layer (17.09 meq/100g). Similarly, the cation exchange capacity (CEC) varies from 62.32 meq/100g for the higher Hama1N4 clay layer to 35.6 meq/100g for the lower Hama1N3 clay layer. Mineralogically, the clay materials are primarily composed of smectites, with illite, kaolinite, calcite, quartz, feldspar, hematite, and goethite also present. This study emphasizes the versatility of clay in various industries and scientific domains. It is known for its impermeability, plasticity, and fossil-preserving capabilities, making it a valuable material for economic, practical, and academic applications.展开更多
Coastal salt marshes represent an important coastal wetland system. In order to tmderstand the differences between boundary layer parameters of vegetated and unvegetated areas, as well as the mechanisms of sediment tr...Coastal salt marshes represent an important coastal wetland system. In order to tmderstand the differences between boundary layer parameters of vegetated and unvegetated areas, as well as the mechanisms of sediment transport, several electromagnetic current meters （AEM HR, products of Alec Electronics Co. Ltd.） were deployed in coastal wetlands in Quanzhou Bay, China, to measure current velocity. During the low tide phase, the surficial sediment was collected at 10 m intervals. In situ measurements show that the current velocities on the bare flat were much higher than those in the Spartina alterniflora marsh. Current velocity also varied with distance from marsh edge and plant canopy height and diameter. Around 63% of the velocity profiles in the tidal creek can be described by a logarithmic equation. Over the bare flat and Spartina alterniflora marsh, a logarithmic profile almost occurs during the flood tide phase. Sediment analysis shows that mean grain size was 6.7 Ф along the marsh edge, and surface sediments were transported from bare fiat to marsh; the tidal creeks may change this sediment transport pattern. The hydrodynamics at early flood tide and late ebb tide phases determined the net transport direction within the study area.展开更多
This paper describes a radioactive tracer experiment carried out at the landward spoil site of the North Passage in the Yangtze Estuary in June, 1991. Scandium -46 was selected as the tracer, the total activity releas...This paper describes a radioactive tracer experiment carried out at the landward spoil site of the North Passage in the Yangtze Estuary in June, 1991. Scandium -46 was selected as the tracer, the total activity released was 179.45 GBq and the amount of the Sandium-46 glass was 495 g. The purpose of the experiment was to determine the sediment movement direction, path, velocity and transport rate, and therefore, to provide direct evidence for using the landward spoil site in the future. The experimental results showed that the sediment movement was governed by the ebb tide current during the period of mean and neap tides when the radioactive tracer was injected both on the flood and ebb tides, and the sediment moved from the release point to the middle of the North Passage near navigation buoy No. 269. The direciton of the sediment movement was 110 ° , the particle velocity was 758 m/d, and the sediment transport rate per unit width was 47.8 m3 / md.展开更多
Single-chamber sediment microbial fuel cells(SSMFCs) have received considerable attention nowadays because of their unique dual-functionality of power generation and enhancement of wastewater treatment performance. Th...Single-chamber sediment microbial fuel cells(SSMFCs) have received considerable attention nowadays because of their unique dual-functionality of power generation and enhancement of wastewater treatment performance. Thus, scaling up or upgrading SSMFCs for enhanced and efficient performance is a highly crucial task. Therefore, in order to achieve this goal, an innovative physical technique of using interface layers with four different pore sizes embedded in the middle of SSMFCs was utilized in this study.Experimental results showed that the performance of SSMFCs employing an interface layer was improved regardless of the pore size of the interface material, compared to those without such layers. The use of an interface layer resulted in a positive and significant effect on the performance of SSMFCs because of the effective prevention of oxygen diffusion from the cathode to the anode. Nevertheless, when a smaller pore size interface was utilized, better power performance and COD degradation were observed. A maximum power density of 0.032 mW/m^2 and COD degradation of 47.3% were obtained in the case of an interface pore size of 0.28 μm. The findings in this study are of significance to promote the future practical application of SSMFCs in wastewater treatment plants.展开更多
基金supported by the Natural Science Foundation of Henan Province(Grant No.202300410547)National Natural Science Foundation of China(Grant No.41774066)Fundamental Research Funds for Yellow River Institute of Hydraulic Research(Grant No.HKY-JBYW-2021-10).
文摘Since most of the natural disasters in the Yellow River are caused by sediment,the study of sediment composition,erosion and transport law is a fundamental part of sediment management in the Yellow River.As a method of in-situ testing,shear wave detection can obtain physical parameters such as the shear modulus of sediment.This paper,based on the Biot–Stoll model,deduces the equations for calculating the reflection and transmission coefficients when a shear wave is incident at the interface between sediment layer,and analyzes the effects of frequency,incident angle and porosity on the reflection and transmission coeffi cients of shear waves,as well as the diff erences in the propagation characteristics of longitudinal and shear waves at the interface between sediment layer.The results indicate that the refl ection and transmission coeffi cients of shear waves are linearly related to the porosity of sediment,and the refl ection coeffi cient of shear waves increases with the increase of porosity.The incident angle has a great infl uence on the changes of the reflection and transmission coefficients of shear waves,especially near the critical angle,the coeffi cients change abruptly.The frequency has a great infl uence on the refl ection and transmission coeffi cients of shear waves only near the characteristic frequency of sediment,while deviation from the characteristic frequency,the infl uence is small.The research results have certain signifi cance for obtaining the physical parameters of sediment and analyzying the composition of the Yellow River sediment and its erosion law.
文摘The concentrations, accumulation and sources of 15 polycyclic aromatic hydrocarbons （PAHs） had been studied or evaluated in the surface layer sediments of Taizhou Bay, China. It showed that the concentrations of PAHs ranged from 85.4 to 167.6 ng/g （averaged 138.62 ng/g）, and the highest level was found in Jiao Jiang Dock. Percentages of 2-, 3-, 4-, 5- and 6-cyclic aromatic hydrocarbons were 7.8 %, 42.1%, 33.3 %, 9.6 % and 7.2 % respectively. The accumulation indices of PAHs ranged from 532.7 to 1068.9 （averaged 807.5）, and the index of Phenanthrene was the highest （122.7）, while that of Benzo （a） Pyrene was the lowest （2.7） among them. In Taizhou Bay, PAHs in surface layer sediments came mainly from coal burning, partly from direct pollution of petroleum hydrocarbons.
文摘DDCl-1 type seismic profiler for deep sediment layers is a large scale marine survey equipment. Its penetrating strata depth may reach to 1 km. This equipment suits surveys for continental shelf,seafloor trench and geological structure under seafloor etc. It suits also geological environment surveys of seafloor resources.The working principle, block diagrams composition and echo signal processing characteristics are presented, and some typical strata profiles are shown.
文摘A review of former studies on the onset of sediment movement under wave action reveals that the Shields criterion obtained in unidirectional steady flow can also be applicable to oscillatory unsteady flow when the boundary layer is the same. In this paper, through comparison of different boundary layers in wave and steady flow conditions, a new criterion is presented which can be used to predict the threshold of sediment movement Linder wave action. The criterion curve shows good agreement with the experimental data.
文摘A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above the seabed. Based upon the logarithmic-profile equation, the boundary layer parameters, i.e., u, z0 and C60, were obtained for 247 tidal flow velocity profiles. Around 90% of the profiles were logarithmic according to the critical correlation coefficient. Internal consistency analysis shows that these parameters derived by different methods are consistent with each other. In addition, the height of the bedforms observed is close to the seabed roughness lengths calculated from the velocity profiles, indicating that the boundary layer parameters obtained can reveal the conditions at the sediment-water interface on the intertidal flats. Suspended sediment concentrations were obtained from the 5 CTMS turbidity meters using laboratory and in-situ calibrations. The results show that the in-situ calibrated SSCs have a much higher accuracy than the laboratory calibrated ones. Calculation of suspended sediment fluxes on the intertidal flats, with a magnitude of 104 kg/m per spring tidal cycle, indicates that suspended sediment moves towards the northwest, which is reversal to the transport pattern controlled by the southward Northern Jiangsu Coastal Current in the sub-tidal zone and adjacent shallow waters.
文摘In this paper, the study on the fine velocity structure of sedimental and basement layers along 4 deep seismic sounding profiles in the Three Gorges Region of the Changjiang River (Yangtze River) are presented. The velocity of sedimental cover is larger in hills of western Hubei in the western profiles, the total thickness is about 0～0.3 km. However, it becomes thick in southern part of Zigui basin and Zushui river valley, about 5.0 km and 4.0 km thick respectively. The sedimental cover is very thick in Jianghan plains in the eastern profiles, about 5～8 km, and the velocity is lower. The velocity of basemental plane is greater than 6.0 km/s over the whole region. An interface can be divided within the sedimental layer, it is about 3～4 km deep in Jianghan plains, while it approximates to surface in other regions. The profiles are cut by faults in many positions. Where the faults pass, the velocity isopleth varies sharply, and the velocity is obviously low. The basement layer is characterized by high velocity and low gradient, there exist 3 high velocity anomalous zones within the layer, which are located at the west, south and east of Huangling Anticlinorium respectively. They are the upwelling materials of basalt magma with high velocity from deep crust. Perhaps, this process took place before formation of Huangling Anticlinorium. Its action produces the significant variation of basement plane depth and the correspondent development and action of faults.
基金The National Science Foundation of China under contract No.40572142the Doctoral Foundation of the Ministry of Education of China under contract No.20040423016.
文摘The diffusive boundary layer （DBL） is the zone for matter exchange between surface water and aquatic sediments. To elucidate the influence of DBL on salt release from saline sediments to freshwater, two experiments with or without wind blowing were conducted. According to the experiments, a 3.5 cm DBL is formed above the smoothed sediments at a steady wind field and this thickness is greater than other studies. The observed flux of salt through the DBL is 6% larger than the calculated value from Fick＇ s first law. The results indicate that molecular diffusion is the dominant mechanism for salt transport through the DBL. The presence of DBL suppresses the hydrodynamic enhancement for matter exchange between sediments and overlying water. Therefore, salts in the sediments of a polder reservoir may influence the water quality chronically.
文摘Tanlu fault zone(TLFZ)is the largest active fault zone in eastern China.It is characterized by complex tectonic evolution and multiple faults and marks the boundary between the North and South China blocks.An indepth understanding of the distinct crustal structures of both parts of the TLFZ will provide valuable insights into the lithospheric and crustal thinning in eastern China,extensive magmatism since the Mesozoic,and formation mechanisms of metallogenic belts along the Yangtze River.In this study,a two-layer H-κstacking approach was adopted to estimate the thicknesses of the sediment and crystalline crust as well as the corresponding vP/vS ratios based on high-quality teleseismic P-wave receiver functions recorded by permanent and temporary stations in and around the TLFZ.The geological units in the study region were delineated,especially the crustal structures beneath extensive sedimentary basins on both sides of the TLFZ.The following conclusions can be drawn:(1)The crustal thickness in and around the TLFZ greatly varies depending on the segment.In the northern segment,the crust is relatively thin beneath the eastern part of the Songliao Basin,a broad uplift of the Moho can be observed,and the Moho descends from south to north.The crust below the central and southern segments becomes thinner from west to east.The thickness of the crust is less than 30 km toward the eastern side of the boundary between the Jiangsu and Anhui provinces,that is,significantly thinner than in other areas.In terms of the vP/vS ratios,high anomalies were detected in the central-southern segments of the TLFZ,indicating the upwelling of deep mantle magma via deep faults.(2)Positive isostatic gravity anomalies were observed in the eastern part of the northern segment of the TLFZ and in the eastern part of the Suwan segment.The crustal thickness is smaller than that obtained from the Airy model of isostasy.This suggests that the lower crust in this area may have experienced intensive transformation processes,which may be related to crustal thinning(caused by crustal extension)and the strong uplift of the mantle in eastern China.The isostatic gravity anomalies between the eastern and western parts of the TLFZ indicate that the fault zone plays a dominant role in controlling the development of the deep crustal structure.(3)Significant crustal thinning was observed beneath the eastern part of the boundary between the Jiangsu and Anhui provinces in the southern segment of the TLFZ,suggesting that this area is prone to lithospheric thinning of the North China Craton.Due to the subduction,compression,and retreat of the Paleo-Pacific Plate during the Yanshanian Period as well as the dehydration of subducting oceanic crust(within subduction zones),the asthenosphere and oceanic crust in eastern China partially melted,resulting in mantle enrichment.The basic magma from the mantle is accumulated at the base of the crust,leading to magmatic underplating.In areas with weak topography toward the east of the TLFZ,magma rises to the upper crust and surface,resulting in the enrichment of multiple metal deposits in this area.
基金supported by the National Key Basic Research Development Program of China (973 Program, Grant No.2010CB429002)the National Natural Science Foundation of China (Grant No. 50979033)+1 种基金the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions, the Special Research Funding of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering (Grant No. 2009585812)Scotland-China Higher Education Research Partnership for PhD Studies (Grant No. [2010]6044)
文摘Based on a wave bottom boundary layer model and a sediment advection-diffusion model, seven turbulence schemes are compared regarding their performances in prediction of near-bed sediment suspension beneath waves above a plane bed. These turbulence algorithm., include six empirical eddy viscosity schemes and one standard two-equation k-e model. In particular, different combinations of typical empirical formulas for the eddy viscosity profile and for the wave friction factor are examined. Numerical results are compared with four laboratory data sets, consisting of one wave boundary layer hydrodynamics experiment and three sediment suspension experiments under linear waves and the Stokes second-order waves. It is shown that predictions of near-bed sediment suspension are very sensitive to the choices of the empirical formulas in turbulence schemes. Simple empirical turbulence schemes are possible to perform equally well as the two-equation k-ε model. Among the empirical schemes, the turbulence scheme, combining the exponential formula for eddy viscosity and Swart formula for wave friction factor, is the most accurate. It maintains the simplicity and yields identically good predictions as the k-ε model does in terms of the wave-averaged sediment concentration.
基金The National Natural Science Foundation of China under contract Nos 51609244 and 51779258
文摘An analytical model with essential parameters given by a two-phase numerical model is utilized to study the net boundary layer current and sediment transport under skewed asymmetric oscillatory sheet flows. The analytical model is the first instantaneous type model that can consider phase-lag and asymmetric boundary layer development. The two-phase model supplies the essential phase-lead, instantaneous erosion depth and boundary layer development for the analytical model to enhance the understanding of velocity skewness and acceleration skewness in sediment flux and transport rate. The sediment transport difference between onshore and offshore stages caused by velocity skewness or acceleration skewness is shown to illustrate the determination of net sediment transport by the analytical model. In previous studies about sediment transport in skewed asymmetric sheet flows, the generation of net sediment transport is mainly concluded to the phase-lag effect.However, the phase-lag effect is shown important but not enough for the net sediment transport, while the skewed asymmetric boundary layer development generated net boundary layer current and mobile bed effect are key important in the transport process.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51061130546 and 51379127)the Key Projects in the National Science&Technology Pillar Program(Grant No.2012BAC07B02)
文摘In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer （BBL）. Field observations were carried out in the northwest Caofeidian sea area in the Bohai Bay. Near 2 m isobath （under the lowest tidal level）, a tripod system was installed with AWAC （Acoustic Wave And Current）, ADCP （Acoustic Doppler Current Profilers）, OBS-3A （Optical Backscatter Point Sensor）, ADV （Acoustic Doppler Velocimeters）, etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt： 1） The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m^3 and the average value being 0.03 kg/m^3; 2） The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m^3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m^3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended load sediment concentration is mainly influenced by wave-induced sediment suspension.
文摘The present study examines the morphological, physicochemical, and mineralogical specificity of clay sediments in the Hamakoussou Basin with the objective of exploring their potential applications. Field data collection was followed by a series of physicochemical and mineralogical tests on the clay samples. Results show that the clay layers, which range in thickness from 11 - 120 cm, exhibit gray, yellowish, or greenish colors. From a physicochemical perspective, these clay layers are found to be basic with a pH ranging from 8.5 for the higher Hama2 layer to 7.6 for the lower Hama1 layer. The sum of exchangeable bases (S) is medium to high with higher values in the Hama1 layer (53.45 meq/100g) and lower values in the Hama3 layer (17.09 meq/100g). Similarly, the cation exchange capacity (CEC) varies from 62.32 meq/100g for the higher Hama1N4 clay layer to 35.6 meq/100g for the lower Hama1N3 clay layer. Mineralogically, the clay materials are primarily composed of smectites, with illite, kaolinite, calcite, quartz, feldspar, hematite, and goethite also present. This study emphasizes the versatility of clay in various industries and scientific domains. It is known for its impermeability, plasticity, and fossil-preserving capabilities, making it a valuable material for economic, practical, and academic applications.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40606012,40576040 and 41076035)
文摘Coastal salt marshes represent an important coastal wetland system. In order to tmderstand the differences between boundary layer parameters of vegetated and unvegetated areas, as well as the mechanisms of sediment transport, several electromagnetic current meters （AEM HR, products of Alec Electronics Co. Ltd.） were deployed in coastal wetlands in Quanzhou Bay, China, to measure current velocity. During the low tide phase, the surficial sediment was collected at 10 m intervals. In situ measurements show that the current velocities on the bare flat were much higher than those in the Spartina alterniflora marsh. Current velocity also varied with distance from marsh edge and plant canopy height and diameter. Around 63% of the velocity profiles in the tidal creek can be described by a logarithmic equation. Over the bare flat and Spartina alterniflora marsh, a logarithmic profile almost occurs during the flood tide phase. Sediment analysis shows that mean grain size was 6.7 Ф along the marsh edge, and surface sediments were transported from bare fiat to marsh; the tidal creeks may change this sediment transport pattern. The hydrodynamics at early flood tide and late ebb tide phases determined the net transport direction within the study area.
文摘This paper describes a radioactive tracer experiment carried out at the landward spoil site of the North Passage in the Yangtze Estuary in June, 1991. Scandium -46 was selected as the tracer, the total activity released was 179.45 GBq and the amount of the Sandium-46 glass was 495 g. The purpose of the experiment was to determine the sediment movement direction, path, velocity and transport rate, and therefore, to provide direct evidence for using the landward spoil site in the future. The experimental results showed that the sediment movement was governed by the ebb tide current during the period of mean and neap tides when the radioactive tracer was injected both on the flood and ebb tides, and the sediment moved from the release point to the middle of the North Passage near navigation buoy No. 269. The direciton of the sediment movement was 110 ° , the particle velocity was 758 m/d, and the sediment transport rate per unit width was 47.8 m3 / md.
基金support from NSC Taiwan under contract number # MOST 106-2923-E-197-001-MY3,106-2221-E-197-019,and 106-26222E-007-CC3the University of Malaya for the high impact research grant HIR-D000006-16001
文摘Single-chamber sediment microbial fuel cells(SSMFCs) have received considerable attention nowadays because of their unique dual-functionality of power generation and enhancement of wastewater treatment performance. Thus, scaling up or upgrading SSMFCs for enhanced and efficient performance is a highly crucial task. Therefore, in order to achieve this goal, an innovative physical technique of using interface layers with four different pore sizes embedded in the middle of SSMFCs was utilized in this study.Experimental results showed that the performance of SSMFCs employing an interface layer was improved regardless of the pore size of the interface material, compared to those without such layers. The use of an interface layer resulted in a positive and significant effect on the performance of SSMFCs because of the effective prevention of oxygen diffusion from the cathode to the anode. Nevertheless, when a smaller pore size interface was utilized, better power performance and COD degradation were observed. A maximum power density of 0.032 mW/m^2 and COD degradation of 47.3% were obtained in the case of an interface pore size of 0.28 μm. The findings in this study are of significance to promote the future practical application of SSMFCs in wastewater treatment plants.
