The resuspension of marine sediments plays a key role in the biogeochemical cycle and marine ecology system.Internal solitary waves are considered to be important driving forces of the resuspension of bottom sediments...The resuspension of marine sediments plays a key role in the biogeochemical cycle and marine ecology system.Internal solitary waves are considered to be important driving forces of the resuspension of bottom sediments.In this paper,the movement of turbidity currents,the generation and the effects on the bottom bed of internal solitary waves and excitation waves are studied by flume tests and numerical simulations,and the sediment resuspension are analyzed.The results show that the excitation wave can lead to the resuspension of the bottom sediments under all the conditions,while the internal solitary wave can lead to the resuspension of the sediment only under some special conditions,such as high amplitude or large underwater slope.Under the experimental conditions,the change in the near-bottom velocity caused by the excitation wave is close to three times that of the internal solitary wave.展开更多
Sediment incipient motion is the first step in sediment resuspension.Previous studies ignored the effect of seepage flow on the mobility of sediment particles and simplified the seabed surface as a rigid boundary.A fl...Sediment incipient motion is the first step in sediment resuspension.Previous studies ignored the effect of seepage flow on the mobility of sediment particles and simplified the seabed surface as a rigid boundary.A flume experiment was designed to innovatively divide the seabed into two parts to control the dynamic response of the seabed and control the seepage conditions.In the experiment,the seabed sediments and the amplitude of internal solitary waves(ISWs)were changed to compare and analyze the impact of seepage flow on the sediment resuspension by shoaling ISWs.Moreover,parametric research and verification were carried out.Results indicate that seepage flow can greatly influence fine sand,promote sediment resuspension,and increase the amount of suspension by two times on average.However,seepage flow had a little effect on the suspension of clayey silt and sandy silt.Besides,seepage force was added to the traditional gravity,drag force,and uplift force,and the parameterization of threshold starting shear stress of coarse-grained sediments was developed.The results of this parameterization were verified,and seepage force was critical to parameterization.The threshold starting shear stress was reduced by 54.6%after increasing the seepage force.The physical mechanism of this process corresponded to the vertical reciprocating transient seepage in and out the seabed interface caused by the wave-induced transient excess pore water pressure.This quantitative study on seepage flow for shear stress of coarse-grained sediments induced by ISWs is critical to geohazard assessment.展开更多
Internal solitary waves(ISWs)are nonlinear fluctuations in nature that could cause significant interactions between seawater and the seabed.ISWs have been proven to be an adequate cause of sediment resuspension in sha...Internal solitary waves(ISWs)are nonlinear fluctuations in nature that could cause significant interactions between seawater and the seabed.ISWs have been proven to be an adequate cause of sediment resuspension in shallow and deep-sea environments.In the South China Sea,ISWs have the largest amplitude globally and directly interact with the seabed near the Dongsha slope in the northern South China Sea.We analyzed the water profile and high-resolution multibeam bathymetric data near the Dongsha slope and revealed that submarine trenches have a significant impact on the sediment resuspension by ISWs.Moreover,ISWs in the zone of the wave-wave interaction enhanced sediment mixing and resuspension.The concentration of the suspended particulate matter inside submarine trenches was significantly higher than that outside them.The concentration of the suspended particulate matter near the bottoms of trenches could be double that outside them and formed a vast bottom nepheloid layer.Trenches could increase the concentration of the suspended particulate matter in the entire water column,and a water column with a high concentration of the suspended particulate matter was formed above the trench.ISWs in the wave-wave interaction zone near Dongsha could induce twice the concentration of the bottom nepheloid layer than those in other areas.The sediment resuspension caused by ISWs is a widespread occurrence all around the world.The findings of this study can offer new insights into the influence of submarine trench and wave-wave interaction on sediment resuspension and help in geohazard assessment.展开更多
Intact sediment cores and wet/dried surficial sediments sampled from the two sublakes in Taihu Lake, Meiliang Bay and Wuli Lake, were incubated in the laboratory to determine the effects of resuspension on internal ph...Intact sediment cores and wet/dried surficial sediments sampled from the two sublakes in Taihu Lake, Meiliang Bay and Wuli Lake, were incubated in the laboratory to determine the effects of resuspension on internal phosphorus loading by simulating different resuspension events. Soluble reactive phosphorus (SRP) release from undisturbed core sediment sampled in the Meiliang Bay and Wuli Lake in July 1998 was 1 53 mg/m 2 and 2 24 mg/m 2 within 4 days, respectively. However during one hour experimental simulation of resuspension, SRP increased by 0 041 mg/L and 0 077 mg/L in the above cores, which indicate that a typical resuspension event in the lake would be accompanied by the release of 10 77 mgSRP/m 2 and 23 1 mgSRP/m 2, respectively. The internal phosphorus loading induced by resuspension is estimated to be 8-10 times greater than the release from undisturbed sediment. SRP release from the dried sediments during simulation of resuspension was mainly dependent on the disturbing intensity. Only when the wind strength gets to certain level, the influence of wind speed on phosphorus release appears significant, indicating that an exchangeable P pool, capable of altering equilibrium conditions in the lake areas, is built up under strongly wind exposed resuspension events.展开更多
In estuarine and coastal areas, the seabed is in a constant process of dynamic change under marine conditions.Seabed sediment erosion and resuspension are important processes that safely control the geological environ...In estuarine and coastal areas, the seabed is in a constant process of dynamic change under marine conditions.Seabed sediment erosion and resuspension are important processes that safely control the geological environment. Field tripod observations conducted in the Jiaozhou Bay in China are reported, to investigate the effects of hydrodynamic conditions on the erosion and resuspension processes of the seabed. The observational results show that the maximum shear stress created by tidal currents can reach 0.35 N/m^2, which is higher than the wave-induced shear stress during fair weather conditions. A seabed erosion frequently occurs during the flood tide, whereas a seabed deposition occurs during ebb tide. Waves can produce a bottom shear stress approximately equivalent to that induced by currents when the local wind reaches Force 4 with a speed of 5 m/s.When the wind reaches 7 m/s and the significant wave height reaches 26 cm, waves play a more significant role than currents in the dynamic processes of the seabed sediment resuspension and lead to a high value of turbidity that is approximately two to eight times higher than that in fair weather. These analyses clearly illustrate that periodic current-induced sediment erosion and resuspension are dominant in fair weather, whereas episodic high waves are responsible for significant sediment resuspension. Additional work is needed to establish a more thorough understanding of the mechanisms of sediment dynamics in the Jiaozhou Bay.展开更多
Variation of bioavailable phosphorus(BAP) concentrations,i.e.,the sum of dissolved total phosphorus(DTP) and bioavailable particulate phosphorus(BAPP),was investigated in a phosphorus(P)-abundant system as influenced ...Variation of bioavailable phosphorus(BAP) concentrations,i.e.,the sum of dissolved total phosphorus(DTP) and bioavailable particulate phosphorus(BAPP),was investigated in a phosphorus(P)-abundant system as influenced by repeated sediment resuspension.The overlying water and sediments in the studied system collected from a city canal,with the initial BAP concentration about 0.679 mg·L-1 in the overlying water.The sediments were disturbed with rotating blade once every day for 30 days in the experimental system.Concentrations of dissolved inorganic phosphorus(DIP),DTP,and total phosphorus(TP) in overlying water and algal available phosphorus(AAP),total phosphorus(Tot-P) in suspended particles were determined in diminishing frequency.It was found that the BAP decreased rapidly in the beginning few days in the sediment resuspension system,and then kept decreasing gradually at a low level,compared with the static conditions.This was mainly attributed to the sharp decrease of DIP.It is suggested that repeated sediment resuspension plays a significant role in phosphorus migration and converting it to more stable forms.展开更多
The vortex generator(VG)and its well-known effect in flow optimization are widely studied and employed across different engineering sectors.However,while the same working principles of VG may be well suited for the ap...The vortex generator(VG)and its well-known effect in flow optimization are widely studied and employed across different engineering sectors.However,while the same working principles of VG may be well suited for the applications on surface-cleaning technologies,such promising potential is hardly,if any,explored in the published literature.Therefore,in the present study,the influence on flow-induced particle resuspension brought by a rectangular vG in a channel flow is investigated with the help of highfidelity computational fluid dynamics simulations.Substantial increases of particle removal forces and resuspension rates are discovered in long,strip-like regions with reduced boundary-layer thickness resulted from the vG-induced vortices,and the enhancement effect is especially significant for configurations with the VG installed at a greater angle of attack.It is also shown that while the resuspension enhancements on the lower and the upper surfaces of the channel exhibit distinct statistical characteristics,having a VG in the channel improves the overall particle-removing capability of the channel flow by introducing higher surface-averaged removal forces and particle resuspension rates.Last but not least,the increase of resuspension rate is especially significant for the smaller,micron-scale particles which are otherwise hardly disturbed by a VG-less channel flow,and such resuspension-enhancement effectgenerally subsides with increasing particle size.展开更多
The resuspension of graphite dust is an important phenomenon in the release of radioactivity and the safety of nuclear reactors during severe accidents.In this study,a visualization experimental platform is constructe...The resuspension of graphite dust is an important phenomenon in the release of radioactivity and the safety of nuclear reactors during severe accidents.In this study,a visualization experimental platform is constructed to study effects of particle size,flow velocity,and wall roughness on the resuspension characteristics of graphite particles.A statistical model of particle resuspension applicable to monolayer dispersed particles is developed based on the moment equilibrium of the particles and the flow field characteristics,as calculated by the large-eddy simulation framework.The results show that particle resuspension can be divided into short-and long-term resuspension stages.Most particle resuspension occurs during the short-term stage.With increases in flow velocity and particle diameter,the aerodynamic or adhesion force acting on the particles increases,and corresponding particle resuspension fraction increases.The influence of rough walls on particle resuspension is related to both the force on the particles and the arm ratio between the wall morphology and the particle diameter.A comparison with the experimental results demonstrates that the particle resuspension model developed in this study accurately predicts the impact of flow velocity,particle size,and wall roughness on particle resuspension.展开更多
A field observation of the hydrodynamics and the sediment resuspension in a bottom boundary layer was carried out in the Changjiang Estuary, during July-August 1997. Using bottom field research facilities, detailed me...A field observation of the hydrodynamics and the sediment resuspension in a bottom boundary layer was carried out in the Changjiang Estuary, during July-August 1997. Using bottom field research facilities, detailed measurements of near-bottom currents and suspended sediment concentration distribution within 1.0 m above bed have been obtained in the Changjiang Estuary——a high concentration estuary. An Acoustic Suspended Sediment Monitor (ASSM) wasused to observe near bed sediment resuspension processes. In addition, the log-profile method was applied to estimating hydraulic roughness Z0 and bottom shear stress values (or friction velocities u). Further understanding of sediment suspension mechanics and hydrodynamic characteristics will require the long-term measurements of near bed processes.展开更多
In this study,particle resuspension due to surface vibration was investigated.A spherical particle was assumed to rest on top of a thin plate,and an external vibrating force was applied normal on the plate at t=0 and ...In this study,particle resuspension due to surface vibration was investigated.A spherical particle was assumed to rest on top of a thin plate,and an external vibrating force was applied normal on the plate at t=0 and at distance R from the particle.The external driving force created a displacement field in both time and space domains,where deformations in the body of the plate were considered small elastic oscillations that are perpendicular to the propagation of the displacement.Free oscillations were introduced via the theory of elasticity and the creation of waves on thin plates,i.e.,bending waves.Particle motion in the vertical direction was initiated through plate displacement,provided that inertia due to particle mass is overcome.In particular,the particle was assumed to oscillate with a force(of oscillation)estimated via Newton’s second law of motion,comprising of two components:the acceleration due to the plate displacement and the particle mass.Subsequently,a simple force balance method was used to determine the conditions for resuspension.Accordingly,resuspension occurs when the oscillation force exceeds the couple of the adhesive and gravitational forces.The results suggest that the plate displacement depends on the characteristics of the applied force,material properties,and plate thickness.In addition,it was found that the oscillation force is substantially lower than the applied force and that it depends on plate displacement and particle mass.Additionally,the particle size significantly influencedthe outcome of resuspension.Thus,resuspension is favorable for large particles,strong applied forces,and high forcing frequencies.展开更多
The vibration of dusty surfaces inevitably causes re-entrainment of particles into the atmosphere.Given that movement of mineral dust particles deposited on a surface begins at a critical frequency (fc) and amplitude,...The vibration of dusty surfaces inevitably causes re-entrainment of particles into the atmosphere.Given that movement of mineral dust particles deposited on a surface begins at a critical frequency (fc) and amplitude,an experimental laboratory study was conducted to determine the onset conditions for resuspension of a vibrated granular soil.We determined the resuspension state diagram as a function of frequency and amplitude of a sinusoidal vibration,the granulometry of the dust and the thickness of the soil bed.The mitigation effect of humidity was also evaluated.Critical frequencies ranged between 2.5 and 23 Hz when amplitudes were less than 12 rmm.These results were independent of bed thickness and perturbation type.For all particle sizes observed,fc decreased monotonically with A,contrasting with behavior observed for individual particles.In dry samples,fe for large size classes was markedly less when A was greater than 6 mm;while thefc for fine fractions only decreased once amplitudes reached 10 mm.Experiments with wet granular soils demonstrated that wetting above an optimum humidity did not necessarily impede movement and caused agglomeration.This study provides guidelines for managing resuspension of granular soils subjected to vibrations.展开更多
In this study,we sampled the original sediment columns from three points located in the eastern,central,and western areas of Chaohu Lake,and then investigated sediment resuspension under hydraulic disturbances in the ...In this study,we sampled the original sediment columns from three points located in the eastern,central,and western areas of Chaohu Lake,and then investigated sediment resuspension under hydraulic disturbances in the laboratory. The results showed that when the hydraulic disturbance is weak and sediment surface shear stress is small (<0.02 N/m²),sediment surface layer moves alone. When the hydraulic disturbance is moderate and sediment surface shear stress is within a threshold (3.7 N/m²),only a small proportion of the surface sediments begins to move. However,when the hydraulic disturbance is further strengthened and sediment surface shear stress is larger than the threshold value,surface sediments move smoothly. By the experimental results,we found that the plankton layer is about 1 mm (1.56% of the maximum content of suspended matter (SSCmax)),which is the major contribution of individual sediment initiation. The new sediment layer is about 19–22 mm (20.9% of the SSCmax),which considerably affects sediment resuspension in shallow lakes. The consolidated layer is about 22 mm below the bed surface,which requires high shear stress and is hard to be transferred to the water column. The quantified experimental observation results are further verified with the theoretical results.展开更多
Vertical distribution processes of sediment contaminants in water were studied by flume experiments.Experimental results show that settling velocity of sediment particles and turbulence characteristics are the major h...Vertical distribution processes of sediment contaminants in water were studied by flume experiments.Experimental results show that settling velocity of sediment particles and turbulence characteristics are the major hydrodynamic factors impacting distribution of pollutants,especially near the bottom where particle diameter is similar in size to vortex structure. Sediment distribution was uniform along the distance, while contaminant distribution slightly lagged behind the sediment. The smaller the initial sediment concentration was, the more time it took to achieve a uniform concentration distribution for suspended sediment. A contaminants transportation equation was established depending on mass conservation equations. Two mathematical estimation models of pollutant distribution in the overlying water considering adsorption and desorption were devised based on vertical distribution of suspended sediment: equilibrium partition model and dynamic micro-diffusion model. The ratio of time scale between the sediment movement and sorption can be used as the index of the models. When this ratio was large, the equilibrium assumption was reasonable, but when it was small, it might require dynamic micro-diffusion model.展开更多
Sediment convergence and resuspension are the two major mechanisms in forming turbidity maximum (TM) in the Changjiang Estuary. Sediment convergence is mainly controlled by the interaction between runoff and tidal cur...Sediment convergence and resuspension are the two major mechanisms in forming turbidity maximum (TM) in the Changjiang Estuary. Sediment convergence is mainly controlled by the interaction between runoff and tidal current, the mixing of freshwater and salt water, the former forming tidal TM, whereas the latter forming brackish TM. The TM in the Changjiang Estuary is characterized by a combination of tidal TM and brackish TM, which varies temporally and spatially.展开更多
210Po and 210Pb are increasingly used to constrain particle dynamics in the open oceans,however they are less used in coastal waters.Here,distributions and partitions of 210Po and 210Pb were examined in the Taiwan Str...210Po and 210Pb are increasingly used to constrain particle dynamics in the open oceans,however they are less used in coastal waters.Here,distributions and partitions of 210Po and 210Pb were examined in the Taiwan Strait,as well as their application to quantify particle sinking.Activity concentrations of dissolved 210Po and 210Pb(<0.6μm)ranged from 1.21 to 7.63 dpm/(100 L)and from 1.07 to 6.33 dpm/(100 L),respectively.Activity concentrations of particulate 210Po and 210Pb varied from 1.96 to 36.74 dpm/(100 L)and from 3.11 to 38.06 dpm/(100 L).Overall,particulate 210Po and 210Pb accounted for the majority of the bulk 210Po and 210Pb.210Po either in dissolved or particulate phases showed similar spatial patterns to 210Pb,indicating similar mechanisms for controlling the distributions of 210Po and 210Pb in the Taiwan Strait.The different fractionation coefficients indicated that particles in the Zhemin Coastal Current(ZCC)inclined to absorb 210Po prior to 210Pb while they showed an opposite effect in the Taiwan Warm Current(TWC).Based on the disequilibria between 210Po and 210Pb,the sinking fluxes of total particulate matter(TPM)were estimated to range from–0.22 to 3.84 g/(m2·d),showing an overall comparable spatial distribution to previous reported sediment accumulation rates.However,our sinking fluxes were lower than the sedimentation rates,indicating a sediment resuspension in winter and horizontal transport of particulate matter from the Taiwan Strait to the East China Sea.展开更多
For a long time,most studies about pyrite have focused on sediments while only a few have focused on pyrite in water.In this study,a method that combines the scanning electron microscopy(SEM)and the energy dispersive ...For a long time,most studies about pyrite have focused on sediments while only a few have focused on pyrite in water.In this study,a method that combines the scanning electron microscopy(SEM)and the energy dispersive X-ray spectrometry(EDS)was used to compare pyrite particles suspended in water to those in associated bottom sediments,both obtained from the mixing zone of the Yangtze Estuary.It was found that the pyrite particles in the two media have similar morphologies and size distributions.The particle morphology mainly includes two types,single crystal and aggregate,and the particle size mainly ranges from 0.5 to 2μm.The pyrite particles in water exhibit an increase in relative content towards the sea,and their transport and deposit processes are mainly affected by hydrodynamic conditions.It is concluded that the pyrite particles in the suspended matter mainly derived from the resuspension of sediments,which are products of the early diagenesis.Precursor minerals may appear during the formation of pyrite,but are generally restricted by the diagenetic environment and local microenvironment.展开更多
The aim of this study was to investigate the release of inorganic and organic phosphorus species from particles in rivers and estuaries during resuspension events such as storm, wind and tidal induced turbulence. To a...The aim of this study was to investigate the release of inorganic and organic phosphorus species from particles in rivers and estuaries during resuspension events such as storm, wind and tidal induced turbulence. To achieve this aim, laboratory beaker experiments were designed with autoanalyzer 3 (AA3). The study first investigates phosphorus equilibration in ultra-pure water (UHP) water, biotic river water and abiotic river water under short term and long term conditions. Then, three typical organic and inorganic phosphorus compounds were selected (orthophosphate, phytic acid (PTA) and β-D-glucose-6-phosphate monosodium salt (G-6-P)) to simulate the effect of addition input to river and estuaries in the time period of 150 h. The results show that in a turbulent river, dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) will reach equilibrium between the particulate matter and the water column within 24 h. Additional input of DIP or DOP to the river, has different effects to the river nutrients balance. The buffering capacity of the suspended particulate matter (SPM) plays an important role and behavior difference to the inorganic and various organic phosphorus compounds.展开更多
The investigation and continuous monitoring with an innovative iron oxide embedded cellulose acetate membrane (FeO/CAM) on the concentrations of biologically available phosphorus (BAP) were conducted in the Meiliang B...The investigation and continuous monitoring with an innovative iron oxide embedded cellulose acetate membrane (FeO/CAM) on the concentrations of biologically available phosphorus (BAP) were conducted in the Meiliang Bay of the Taihu Lake during summer in 2004. The results showed that the concentrations of dissolved (FeO-DP), particulate (FeO-PP) and total bioavailable phosphorus (FeO-P) had similar horizontal distribution. The BAP concentrations were the highest in those estuaries in the northern bay. With the decrease of the distance to the estuary or long shore,there was little difference between BAP concentrations in an open lake area. During the observation period, algal blooms occurred in most waters of the northern bay, which was reflected from the high concentrations of chlorophyll a (Chl-a). While they were not highest in the estuarine waters of those major rivers, this is the case for the BAP concentrations. The concentrations of Chl-a had a significantly positive correlation with those of bioavailable phosphorus in the open area of the Meiliang Bay.With the sediment resuspension induced by wind and wave, BAP concentrations increased in a short-term, indicating that the riverine P inputs mainly contribute to the concentrations of BAP in the estuarine water while internal P release was the major source of BAP in the open lake area. In the eutrophic shallow lake, the blooms of alga may cause pH increase and further result in internal P release. The above results showed that the new membrane of FeO/CAM can be used to monitor the concentrations of BAP and provide the scientific justifications for the control strategy of the lake eutrophication.展开更多
Nitrogen in pond sediments is a major water quality concern and can impact the productivity of aquaculture.Dissolved oxygen is an important factor for improving water quality and boosting fish growth in aquaculture po...Nitrogen in pond sediments is a major water quality concern and can impact the productivity of aquaculture.Dissolved oxygen is an important factor for improving water quality and boosting fish growth in aquaculture ponds,and plays an important role in the conversion of ammonium-nitrogen(NH4-N)to nitrite-nitrogen(NO2--N)and eventually nitrate-nitrogen(NO3--N).A central goal of the study was to identify the best aeration method and strategy for improving water quality in aquaculture ponds.We conducted an experiment with six tanks,each with a different aeration mode to simulate the behavior of aquaculture ponds.The results show that a 36 hr aeration interval(Tc=36 hr:36 hr)and no aeration resulted in high concentrations of NH4-N in the water column.Using a 12 hr interval time(Tc=12 hr:12 hr)resulted in higher NO2--N and NO3--N concentrations than any other aeration mode.Results from an 8 hr interval time(Tc=8 hr:8 hr)and 24 hr interval time(Tc=24 hr:24 hr)were comparable with those of continuous aeration,and had the benefit of being in use for only half of the time,consequently reducing energy consumption.展开更多
基金The research was supported by the National Natural Science Foundation of China(Nos.42206055,41976049,41720104001)the Taishan Scholar Project of Shandong Province(No.TS20190913)the Fundamental Research Funds for the Central Universities(No.202061028).
文摘The resuspension of marine sediments plays a key role in the biogeochemical cycle and marine ecology system.Internal solitary waves are considered to be important driving forces of the resuspension of bottom sediments.In this paper,the movement of turbidity currents,the generation and the effects on the bottom bed of internal solitary waves and excitation waves are studied by flume tests and numerical simulations,and the sediment resuspension are analyzed.The results show that the excitation wave can lead to the resuspension of the bottom sediments under all the conditions,while the internal solitary wave can lead to the resuspension of the sediment only under some special conditions,such as high amplitude or large underwater slope.Under the experimental conditions,the change in the near-bottom velocity caused by the excitation wave is close to three times that of the internal solitary wave.
基金Supported by the Natural Science Foundation of Jiangsu Province(No.BK20210527)the Open Research Fund of Key Laboratory of Coastal Science and Integrated Management,Ministry of Natural Resources(No.2021COSIMQ002)+1 种基金the National Natural Science Foundation of China(Nos.42107158,41831280)the Fundamental Research Funds for the Central Universities(No.2021QN1096)。
文摘Sediment incipient motion is the first step in sediment resuspension.Previous studies ignored the effect of seepage flow on the mobility of sediment particles and simplified the seabed surface as a rigid boundary.A flume experiment was designed to innovatively divide the seabed into two parts to control the dynamic response of the seabed and control the seepage conditions.In the experiment,the seabed sediments and the amplitude of internal solitary waves(ISWs)were changed to compare and analyze the impact of seepage flow on the sediment resuspension by shoaling ISWs.Moreover,parametric research and verification were carried out.Results indicate that seepage flow can greatly influence fine sand,promote sediment resuspension,and increase the amount of suspension by two times on average.However,seepage flow had a little effect on the suspension of clayey silt and sandy silt.Besides,seepage force was added to the traditional gravity,drag force,and uplift force,and the parameterization of threshold starting shear stress of coarse-grained sediments was developed.The results of this parameterization were verified,and seepage force was critical to parameterization.The threshold starting shear stress was reduced by 54.6%after increasing the seepage force.The physical mechanism of this process corresponded to the vertical reciprocating transient seepage in and out the seabed interface caused by the wave-induced transient excess pore water pressure.This quantitative study on seepage flow for shear stress of coarse-grained sediments induced by ISWs is critical to geohazard assessment.
基金supported by the National Natural Science Foundation of China(Nos.42107158 and 41831280)the Natural Science Foundation of Jiangsu Province(No.BK20210527)+2 种基金the Open Research Fund of Key Laboratory of Coastal Science and Integrated Management,the Ministry of Natural Resources,the National Basic Research Program of China(No.2018YFC0309200)the Fundamental Research Funds for the Central Universities(No.2021QN1096)We thank the Natural Science Foundation of China for the Open Research Cruise(No.NORC2018-05).
文摘Internal solitary waves(ISWs)are nonlinear fluctuations in nature that could cause significant interactions between seawater and the seabed.ISWs have been proven to be an adequate cause of sediment resuspension in shallow and deep-sea environments.In the South China Sea,ISWs have the largest amplitude globally and directly interact with the seabed near the Dongsha slope in the northern South China Sea.We analyzed the water profile and high-resolution multibeam bathymetric data near the Dongsha slope and revealed that submarine trenches have a significant impact on the sediment resuspension by ISWs.Moreover,ISWs in the zone of the wave-wave interaction enhanced sediment mixing and resuspension.The concentration of the suspended particulate matter inside submarine trenches was significantly higher than that outside them.The concentration of the suspended particulate matter near the bottoms of trenches could be double that outside them and formed a vast bottom nepheloid layer.Trenches could increase the concentration of the suspended particulate matter in the entire water column,and a water column with a high concentration of the suspended particulate matter was formed above the trench.ISWs in the wave-wave interaction zone near Dongsha could induce twice the concentration of the bottom nepheloid layer than those in other areas.The sediment resuspension caused by ISWs is a widespread occurrence all around the world.The findings of this study can offer new insights into the influence of submarine trench and wave-wave interaction on sediment resuspension and help in geohazard assessment.
文摘Intact sediment cores and wet/dried surficial sediments sampled from the two sublakes in Taihu Lake, Meiliang Bay and Wuli Lake, were incubated in the laboratory to determine the effects of resuspension on internal phosphorus loading by simulating different resuspension events. Soluble reactive phosphorus (SRP) release from undisturbed core sediment sampled in the Meiliang Bay and Wuli Lake in July 1998 was 1 53 mg/m 2 and 2 24 mg/m 2 within 4 days, respectively. However during one hour experimental simulation of resuspension, SRP increased by 0 041 mg/L and 0 077 mg/L in the above cores, which indicate that a typical resuspension event in the lake would be accompanied by the release of 10 77 mgSRP/m 2 and 23 1 mgSRP/m 2, respectively. The internal phosphorus loading induced by resuspension is estimated to be 8-10 times greater than the release from undisturbed sediment. SRP release from the dried sediments during simulation of resuspension was mainly dependent on the disturbing intensity. Only when the wind strength gets to certain level, the influence of wind speed on phosphorus release appears significant, indicating that an exchangeable P pool, capable of altering equilibrium conditions in the lake areas, is built up under strongly wind exposed resuspension events.
基金The National Natural Science Foundation of China under contract Nos 41402253,41427803 and 41372287the Project of Qingdao National Laboratory for Marine Science and Technology under contract No.QNLM2016ORP0110
文摘In estuarine and coastal areas, the seabed is in a constant process of dynamic change under marine conditions.Seabed sediment erosion and resuspension are important processes that safely control the geological environment. Field tripod observations conducted in the Jiaozhou Bay in China are reported, to investigate the effects of hydrodynamic conditions on the erosion and resuspension processes of the seabed. The observational results show that the maximum shear stress created by tidal currents can reach 0.35 N/m^2, which is higher than the wave-induced shear stress during fair weather conditions. A seabed erosion frequently occurs during the flood tide, whereas a seabed deposition occurs during ebb tide. Waves can produce a bottom shear stress approximately equivalent to that induced by currents when the local wind reaches Force 4 with a speed of 5 m/s.When the wind reaches 7 m/s and the significant wave height reaches 26 cm, waves play a more significant role than currents in the dynamic processes of the seabed sediment resuspension and lead to a high value of turbidity that is approximately two to eight times higher than that in fair weather. These analyses clearly illustrate that periodic current-induced sediment erosion and resuspension are dominant in fair weather, whereas episodic high waves are responsible for significant sediment resuspension. Additional work is needed to establish a more thorough understanding of the mechanisms of sediment dynamics in the Jiaozhou Bay.
基金National Natural Science Foundations of China(No.50908154,No.50938005)
文摘Variation of bioavailable phosphorus(BAP) concentrations,i.e.,the sum of dissolved total phosphorus(DTP) and bioavailable particulate phosphorus(BAPP),was investigated in a phosphorus(P)-abundant system as influenced by repeated sediment resuspension.The overlying water and sediments in the studied system collected from a city canal,with the initial BAP concentration about 0.679 mg·L-1 in the overlying water.The sediments were disturbed with rotating blade once every day for 30 days in the experimental system.Concentrations of dissolved inorganic phosphorus(DIP),DTP,and total phosphorus(TP) in overlying water and algal available phosphorus(AAP),total phosphorus(Tot-P) in suspended particles were determined in diminishing frequency.It was found that the BAP decreased rapidly in the beginning few days in the sediment resuspension system,and then kept decreasing gradually at a low level,compared with the static conditions.This was mainly attributed to the sharp decrease of DIP.It is suggested that repeated sediment resuspension plays a significant role in phosphorus migration and converting it to more stable forms.
基金the National Natural Science Foundation of China under grant No.92052102 and 12272006 for the third author are hereby gratefully acknowledged.
文摘The vortex generator(VG)and its well-known effect in flow optimization are widely studied and employed across different engineering sectors.However,while the same working principles of VG may be well suited for the applications on surface-cleaning technologies,such promising potential is hardly,if any,explored in the published literature.Therefore,in the present study,the influence on flow-induced particle resuspension brought by a rectangular vG in a channel flow is investigated with the help of highfidelity computational fluid dynamics simulations.Substantial increases of particle removal forces and resuspension rates are discovered in long,strip-like regions with reduced boundary-layer thickness resulted from the vG-induced vortices,and the enhancement effect is especially significant for configurations with the VG installed at a greater angle of attack.It is also shown that while the resuspension enhancements on the lower and the upper surfaces of the channel exhibit distinct statistical characteristics,having a VG in the channel improves the overall particle-removing capability of the channel flow by introducing higher surface-averaged removal forces and particle resuspension rates.Last but not least,the increase of resuspension rate is especially significant for the smaller,micron-scale particles which are otherwise hardly disturbed by a VG-less channel flow,and such resuspension-enhancement effectgenerally subsides with increasing particle size.
基金This project was supported by the Beijing Natural Science Foundation(No.JQ21009)the National Natural Science Foundation of China(NSFC)(No.52176158)+1 种基金the National Key R&D Program of China(No.2020YFB1901401)the Youth Talent Project of China National Nuclear Corporation.
文摘The resuspension of graphite dust is an important phenomenon in the release of radioactivity and the safety of nuclear reactors during severe accidents.In this study,a visualization experimental platform is constructed to study effects of particle size,flow velocity,and wall roughness on the resuspension characteristics of graphite particles.A statistical model of particle resuspension applicable to monolayer dispersed particles is developed based on the moment equilibrium of the particles and the flow field characteristics,as calculated by the large-eddy simulation framework.The results show that particle resuspension can be divided into short-and long-term resuspension stages.Most particle resuspension occurs during the short-term stage.With increases in flow velocity and particle diameter,the aerodynamic or adhesion force acting on the particles increases,and corresponding particle resuspension fraction increases.The influence of rough walls on particle resuspension is related to both the force on the particles and the arm ratio between the wall morphology and the particle diameter.A comparison with the experimental results demonstrates that the particle resuspension model developed in this study accurately predicts the impact of flow velocity,particle size,and wall roughness on particle resuspension.
基金We thank the staff of the Second Institute of Oceanography and State Key Lab of Es-tuarine and Coastal Research for their data collection This work was supported by the State "95" Science and Technology Key Project (Grant No. 96-922-03-02) Supplement
文摘A field observation of the hydrodynamics and the sediment resuspension in a bottom boundary layer was carried out in the Changjiang Estuary, during July-August 1997. Using bottom field research facilities, detailed measurements of near-bottom currents and suspended sediment concentration distribution within 1.0 m above bed have been obtained in the Changjiang Estuary——a high concentration estuary. An Acoustic Suspended Sediment Monitor (ASSM) wasused to observe near bed sediment resuspension processes. In addition, the log-profile method was applied to estimating hydraulic roughness Z0 and bottom shear stress values (or friction velocities u). Further understanding of sediment suspension mechanics and hydrodynamic characteristics will require the long-term measurements of near bed processes.
基金The study was supported by theEuropean Union 7th framework program HEXACOMM FP7/2007-2013 under grant agreement No.315760.
文摘In this study,particle resuspension due to surface vibration was investigated.A spherical particle was assumed to rest on top of a thin plate,and an external vibrating force was applied normal on the plate at t=0 and at distance R from the particle.The external driving force created a displacement field in both time and space domains,where deformations in the body of the plate were considered small elastic oscillations that are perpendicular to the propagation of the displacement.Free oscillations were introduced via the theory of elasticity and the creation of waves on thin plates,i.e.,bending waves.Particle motion in the vertical direction was initiated through plate displacement,provided that inertia due to particle mass is overcome.In particular,the particle was assumed to oscillate with a force(of oscillation)estimated via Newton’s second law of motion,comprising of two components:the acceleration due to the plate displacement and the particle mass.Subsequently,a simple force balance method was used to determine the conditions for resuspension.Accordingly,resuspension occurs when the oscillation force exceeds the couple of the adhesive and gravitational forces.The results suggest that the plate displacement depends on the characteristics of the applied force,material properties,and plate thickness.In addition,it was found that the oscillation force is substantially lower than the applied force and that it depends on plate displacement and particle mass.Additionally,the particle size significantly influencedthe outcome of resuspension.Thus,resuspension is favorable for large particles,strong applied forces,and high forcing frequencies.
基金the Universidad Nacional de San Luis(grant 03-2718)National Scientific and Technical Research Council of Argentina(CONICET).
文摘The vibration of dusty surfaces inevitably causes re-entrainment of particles into the atmosphere.Given that movement of mineral dust particles deposited on a surface begins at a critical frequency (fc) and amplitude,an experimental laboratory study was conducted to determine the onset conditions for resuspension of a vibrated granular soil.We determined the resuspension state diagram as a function of frequency and amplitude of a sinusoidal vibration,the granulometry of the dust and the thickness of the soil bed.The mitigation effect of humidity was also evaluated.Critical frequencies ranged between 2.5 and 23 Hz when amplitudes were less than 12 rmm.These results were independent of bed thickness and perturbation type.For all particle sizes observed,fc decreased monotonically with A,contrasting with behavior observed for individual particles.In dry samples,fe for large size classes was markedly less when A was greater than 6 mm;while thefc for fine fractions only decreased once amplitudes reached 10 mm.Experiments with wet granular soils demonstrated that wetting above an optimum humidity did not necessarily impede movement and caused agglomeration.This study provides guidelines for managing resuspension of granular soils subjected to vibrations.
基金supported by the National Natural Science Foundation of China [grant numbers 52109099,52079094].
文摘In this study,we sampled the original sediment columns from three points located in the eastern,central,and western areas of Chaohu Lake,and then investigated sediment resuspension under hydraulic disturbances in the laboratory. The results showed that when the hydraulic disturbance is weak and sediment surface shear stress is small (<0.02 N/m²),sediment surface layer moves alone. When the hydraulic disturbance is moderate and sediment surface shear stress is within a threshold (3.7 N/m²),only a small proportion of the surface sediments begins to move. However,when the hydraulic disturbance is further strengthened and sediment surface shear stress is larger than the threshold value,surface sediments move smoothly. By the experimental results,we found that the plankton layer is about 1 mm (1.56% of the maximum content of suspended matter (SSCmax)),which is the major contribution of individual sediment initiation. The new sediment layer is about 19–22 mm (20.9% of the SSCmax),which considerably affects sediment resuspension in shallow lakes. The consolidated layer is about 22 mm below the bed surface,which requires high shear stress and is hard to be transferred to the water column. The quantified experimental observation results are further verified with the theoretical results.
基金supported by the National Natural Science Foundation of China (Grant 11502138)the National Key Research and Development Program (Grant 2016YFC0401500)the National Water Pollution Control and Treatment Science and Technology Major Project (Grant 2012ZX07506-002b)
文摘Vertical distribution processes of sediment contaminants in water were studied by flume experiments.Experimental results show that settling velocity of sediment particles and turbulence characteristics are the major hydrodynamic factors impacting distribution of pollutants,especially near the bottom where particle diameter is similar in size to vortex structure. Sediment distribution was uniform along the distance, while contaminant distribution slightly lagged behind the sediment. The smaller the initial sediment concentration was, the more time it took to achieve a uniform concentration distribution for suspended sediment. A contaminants transportation equation was established depending on mass conservation equations. Two mathematical estimation models of pollutant distribution in the overlying water considering adsorption and desorption were devised based on vertical distribution of suspended sediment: equilibrium partition model and dynamic micro-diffusion model. The ratio of time scale between the sediment movement and sorption can be used as the index of the models. When this ratio was large, the equilibrium assumption was reasonable, but when it was small, it might require dynamic micro-diffusion model.
基金the National Natural Science Foundation of China under contract! No. 9487005.
文摘Sediment convergence and resuspension are the two major mechanisms in forming turbidity maximum (TM) in the Changjiang Estuary. Sediment convergence is mainly controlled by the interaction between runoff and tidal current, the mixing of freshwater and salt water, the former forming tidal TM, whereas the latter forming brackish TM. The TM in the Changjiang Estuary is characterized by a combination of tidal TM and brackish TM, which varies temporally and spatially.
基金The National Natural Science Foundation of China under contract Nos 41076043 and 51608142the Guangxi Young and Middle-aged Teachers’ Basic Ability Upgrading Project under contract No.2019KY0298the Guangxi Science and Technology Planning Project under contract No.Gui Ke-AD18126018
文摘210Po and 210Pb are increasingly used to constrain particle dynamics in the open oceans,however they are less used in coastal waters.Here,distributions and partitions of 210Po and 210Pb were examined in the Taiwan Strait,as well as their application to quantify particle sinking.Activity concentrations of dissolved 210Po and 210Pb(<0.6μm)ranged from 1.21 to 7.63 dpm/(100 L)and from 1.07 to 6.33 dpm/(100 L),respectively.Activity concentrations of particulate 210Po and 210Pb varied from 1.96 to 36.74 dpm/(100 L)and from 3.11 to 38.06 dpm/(100 L).Overall,particulate 210Po and 210Pb accounted for the majority of the bulk 210Po and 210Pb.210Po either in dissolved or particulate phases showed similar spatial patterns to 210Pb,indicating similar mechanisms for controlling the distributions of 210Po and 210Pb in the Taiwan Strait.The different fractionation coefficients indicated that particles in the Zhemin Coastal Current(ZCC)inclined to absorb 210Po prior to 210Pb while they showed an opposite effect in the Taiwan Warm Current(TWC).Based on the disequilibria between 210Po and 210Pb,the sinking fluxes of total particulate matter(TPM)were estimated to range from–0.22 to 3.84 g/(m2·d),showing an overall comparable spatial distribution to previous reported sediment accumulation rates.However,our sinking fluxes were lower than the sedimentation rates,indicating a sediment resuspension in winter and horizontal transport of particulate matter from the Taiwan Strait to the East China Sea.
基金the National Natural Science Foundation of China(NSFC)who organized the public survey cruise in the Yangtze River Estuary in March 2015,with special thanks to the crew of the R/V Run Jiang No.1 for kindly assisting in sediment sampling on the cruiseThis study was funded by the NSFC(No.41676036)and the National Key R&D Program of China(No.2016YFA0600904).
文摘For a long time,most studies about pyrite have focused on sediments while only a few have focused on pyrite in water.In this study,a method that combines the scanning electron microscopy(SEM)and the energy dispersive X-ray spectrometry(EDS)was used to compare pyrite particles suspended in water to those in associated bottom sediments,both obtained from the mixing zone of the Yangtze Estuary.It was found that the pyrite particles in the two media have similar morphologies and size distributions.The particle morphology mainly includes two types,single crystal and aggregate,and the particle size mainly ranges from 0.5 to 2μm.The pyrite particles in water exhibit an increase in relative content towards the sea,and their transport and deposit processes are mainly affected by hydrodynamic conditions.It is concluded that the pyrite particles in the suspended matter mainly derived from the resuspension of sediments,which are products of the early diagenesis.Precursor minerals may appear during the formation of pyrite,but are generally restricted by the diagenetic environment and local microenvironment.
文摘The aim of this study was to investigate the release of inorganic and organic phosphorus species from particles in rivers and estuaries during resuspension events such as storm, wind and tidal induced turbulence. To achieve this aim, laboratory beaker experiments were designed with autoanalyzer 3 (AA3). The study first investigates phosphorus equilibration in ultra-pure water (UHP) water, biotic river water and abiotic river water under short term and long term conditions. Then, three typical organic and inorganic phosphorus compounds were selected (orthophosphate, phytic acid (PTA) and β-D-glucose-6-phosphate monosodium salt (G-6-P)) to simulate the effect of addition input to river and estuaries in the time period of 150 h. The results show that in a turbulent river, dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) will reach equilibrium between the particulate matter and the water column within 24 h. Additional input of DIP or DOP to the river, has different effects to the river nutrients balance. The buffering capacity of the suspended particulate matter (SPM) plays an important role and behavior difference to the inorganic and various organic phosphorus compounds.
文摘The investigation and continuous monitoring with an innovative iron oxide embedded cellulose acetate membrane (FeO/CAM) on the concentrations of biologically available phosphorus (BAP) were conducted in the Meiliang Bay of the Taihu Lake during summer in 2004. The results showed that the concentrations of dissolved (FeO-DP), particulate (FeO-PP) and total bioavailable phosphorus (FeO-P) had similar horizontal distribution. The BAP concentrations were the highest in those estuaries in the northern bay. With the decrease of the distance to the estuary or long shore,there was little difference between BAP concentrations in an open lake area. During the observation period, algal blooms occurred in most waters of the northern bay, which was reflected from the high concentrations of chlorophyll a (Chl-a). While they were not highest in the estuarine waters of those major rivers, this is the case for the BAP concentrations. The concentrations of Chl-a had a significantly positive correlation with those of bioavailable phosphorus in the open area of the Meiliang Bay.With the sediment resuspension induced by wind and wave, BAP concentrations increased in a short-term, indicating that the riverine P inputs mainly contribute to the concentrations of BAP in the estuarine water while internal P release was the major source of BAP in the open lake area. In the eutrophic shallow lake, the blooms of alga may cause pH increase and further result in internal P release. The above results showed that the new membrane of FeO/CAM can be used to monitor the concentrations of BAP and provide the scientific justifications for the control strategy of the lake eutrophication.
基金supported by the National Science Foundation of China(No.51579106)financial support from the China Scholarship Council(No.201806150070)
文摘Nitrogen in pond sediments is a major water quality concern and can impact the productivity of aquaculture.Dissolved oxygen is an important factor for improving water quality and boosting fish growth in aquaculture ponds,and plays an important role in the conversion of ammonium-nitrogen(NH4-N)to nitrite-nitrogen(NO2--N)and eventually nitrate-nitrogen(NO3--N).A central goal of the study was to identify the best aeration method and strategy for improving water quality in aquaculture ponds.We conducted an experiment with six tanks,each with a different aeration mode to simulate the behavior of aquaculture ponds.The results show that a 36 hr aeration interval(Tc=36 hr:36 hr)and no aeration resulted in high concentrations of NH4-N in the water column.Using a 12 hr interval time(Tc=12 hr:12 hr)resulted in higher NO2--N and NO3--N concentrations than any other aeration mode.Results from an 8 hr interval time(Tc=8 hr:8 hr)and 24 hr interval time(Tc=24 hr:24 hr)were comparable with those of continuous aeration,and had the benefit of being in use for only half of the time,consequently reducing energy consumption.
