As the most important component of marine siliceous organisms,diatoms are vital primary producers of the ocean that are often used as indicators of paleoenvironmental change.To understand the response of sedimental di...As the most important component of marine siliceous organisms,diatoms are vital primary producers of the ocean that are often used as indicators of paleoenvironmental change.To understand the response of sedimental diatoms to regional environmental changes and the factors affecting the distribution of sedimental diatoms in the Taiwan Strait,this study quantified and classified the diatoms found in surface sediments collected during four surveys from 2019 to 2020.Overall,118 diatom taxa and 44 genera were identified with total diatom abundance of 8-27353 valves/g.Four diatom assemblages representing different environments were identified.Among them,assemblageⅠrepresented a coastal environment,assemblageⅡcomprised warm water species of a coastal environment,AssemblageⅢrepresented a coastal environment affected markedly by exorheism,AssemblageⅣrepresented a group with lowest diatom abundance.Seasonal variation in total diatom abundance was controlled by seven environmental factors:depth,sea surface salinity,mean grain size,silicate,nitrite,nitrate,and phosphate.Spatiotemporal variation in each of the diatom assemblages was substantial and strongly affected by various currents,upwelling,and low-salinity water.Specifically,it was found that the succession of diatom assemblages reflects change in the range of influence of local warm currents.展开更多
Noncohesive particle clusters are identified and tracked in turbulent flows to determine the breakdown and time evolution of cluster statistics and their implications for interscale mass transfer,which has connections...Noncohesive particle clusters are identified and tracked in turbulent flows to determine the breakdown and time evolution of cluster statistics and their implications for interscale mass transfer,which has connections to the classical turbulent energy cascade and its mass cascade counterpart running in parallel.In particular,the formation and dynamics of sediment and larvae clusters are of interest to coral larvae settlement in coastal regions and particularly the resilience of green-gray coastal protection solutions.Analogous cluster behavior is relevant to cloud microphysics and precipitation initiation,radiation transport and light transmission through colloids and suspensions,heat and mass transfer in particle-laden flows,and viral and pollutant transmission.Following a comparison between various clustering techniques,we adopt a density-based cluster identification algorithm based on its simplicity and efficiency,where particles are clustered based on the number of neighboring particles in their individual spheres of influence.We establish parallels with lattice-based percolation theory,as evident in the power-law scaling of the cluster size distribution near the percolation threshold.The degree of discontinuity of the phase transition associated with this percolation threshold is observed to broaden with larger Stokes numbers and thereby large-scale clustering.The sensitivity of our findings to the employed clustering algorithm is discussed.A novel cluster tracking algorithm is deployed to determine the interscale transfer rate along the particle-number phase-space dimension via accounting of cluster breakup and merger events,extending previous work on the bubble breakup cascade beneath surface breaking waves.Our findings shed light on the interaction between particle clusters and their carrier turbulent flows,with an eye toward transport models incorporating cluster characteristics and dynamics.展开更多
Chlorophyll-a is the most abundant chlorophyll pigment produced by marine phytoplankton,and it bears the isotope signature of the nitrate source assimilated in the N-atoms that are embedded in its porphyrin ring.The c...Chlorophyll-a is the most abundant chlorophyll pigment produced by marine phytoplankton,and it bears the isotope signature of the nitrate source assimilated in the N-atoms that are embedded in its porphyrin ring.The chloropigment and its degradation product,i.e.,pheophytin-a,could be well preserved in marine sediment,usually at nanomolar level.A sensitive and accurate measurement of theδ15N of chloropigment is capable of providing rich information to greatly enhance our understanding of past nitrogen cycling,which therefore is urgently needed.Hereby,we present a successful method based on two-step HPLC separation followed by'denitrifier method'.The N-content in acetone and potassium persulfate(K_(2)S_(2)O_(8))are very critical to the precision and accuracy of the measurements,because they constitute the majority of the N contamination to the Chl-a samples.In this method,the recrystallized K_(2)S_(2)O_(8)that is used as oxidization reagent was discovered to have aδ15N background of-15‰,consolidated by repeated examinations over a period of two months.This 15N background of K_(2)S_(2)O_(8)would cause-1‰–-2‰deviation on theδ^(15)N of sample that contains nanomolar level N,and highlight the need to examine theδ^(15)N of recrystallized K_(2)S_(2)O_(8)when it is used to oxidize samples of organic nitrogen.The overall measurement ofδ^(15)N pigment is reliable and has an average analytical precision better than±0.5‰(1σ).This study establish a sensitive method for accurate measurement of theδ^(15)N of nano-molar level chlorophyll pigment,and with no doubts will advance its wide application in marine nitrogen cycling studying.展开更多
Identifying geohazards such as landslides and methane leakage is crucial during gas extraction from natural gas hydrate(NGH)reservoirs,and understanding reservoir settlement behavior is central to this assessment.Hori...Identifying geohazards such as landslides and methane leakage is crucial during gas extraction from natural gas hydrate(NGH)reservoirs,and understanding reservoir settlement behavior is central to this assessment.Horizontal wells can enlarge the pressure relief zone within the formation,improving single-well productivity,and are therefore considered a promising approach for NGH development.This study examines the settlement response of hydrate-bearing sediments during depressurization using horizontal wells.A fully coupled thermal,hydraulic,mechanical,and chemical(THMC)model with representative reservoir properties(Shenhu region in the South China Sea)is presented accordingly.The simulations show that lower production pressures,while increasing gas output,also intensify formation settlement.The maximum difference in settlement between the lowest and highest production pressures reaches 0.016 m,contributing to more pronounced differential subsidence.Optimal well placement,specifically targeting a low-saturation hydrate zone containing free gas and situated adjacent to a high-saturation hydrate layer,markedly improves both gas production rate and cumulative yield,while reducing overall settlement and limiting changes in effective stress.展开更多
The stability of fruit juice has consistently been an important concern in the food processing industry,which can be time-consuming and costly.Therefore,developing accurate stability early-warning model may serve as a...The stability of fruit juice has consistently been an important concern in the food processing industry,which can be time-consuming and costly.Therefore,developing accurate stability early-warning model may serve as a viable solution.Based on multiple light scattering technology,this paper collects the stability data as the training set of Triphala fruit juice over a three-month period and finds that the sediment amount reached 0.6 mg/mL,composed of ellagic acid and phlobaphene,with the solution's light transmittance fluctuating range(23%-76%)and the particle size(0.27-0.29μm)on day 75.The early warning model comprises a synergistic integration of long short-term memory and backpropagation neural network models.The model exhibits a mean absolute percentage error of 0.626%,an R^(2) of 0.911,and an accuracy of 85.71%.This model is capable of predicting key stability parameters,including sedimentation,transmittance,particle size,particle migration rate,and stability index,within a 90-day period in just 7 days,and thereby provide accurate early-stage stability alerts.展开更多
Soil erosion is a fundamental physical process driving land degradation across various spatial and temporal scales.The Soil and Water Assessment Tool(SWAT)model is a robust tool for predicting soil erosion and evaluat...Soil erosion is a fundamental physical process driving land degradation across various spatial and temporal scales.The Soil and Water Assessment Tool(SWAT)model is a robust tool for predicting soil erosion and evaluating water and soil quality within watersheds.The latest version,SWAT+,introduces advanced encoding capabilities and improved performance,making it better suited for addressing complex watershed modeling challenges.This study implemented the SWAT+model to quantify soil erosion rates within the Chehelchay watershed in northern Iran.The foundational dataset comprises a 30-meter resolution Digital Elevation Model(DEM),land use classification,soil,and weather data.Model performance was evaluated using Nash-Sutcliffe Efficiency(NSE),coefficient of determination(R^(2)),root mean square error(RMSE),and percent bias(PBIAS).The SWAT+simulation revealed substantial spatial variation in erosion patterns across the watershed,with annual sediment yields in critical HRUs,reflecting diverse erosion intensities driven by variations in land use,soil characteristics,and slope.Among the Hydrological Response Units(HRUs),50 critical units,representing approximately 9%of the total watershed area,generate sediment yields exceeding 5 tons per hectare per year.The most severe erosion occurs predominantly in the central zone of the watershed.Downstream regions exhibit minimal soil loss due to gentle topography while upstream areas maintain soil stability through protective forest cover,resulting in negligible erosion rates.Best Management Practices(BMPs)were designed to safeguard water and soil resources at a watershed level.The study evaluated three strategic conservation interventions:alfalfa cultivation,agroforestry implementation,and garden development.When applied in combination,these measures achieved approximately 30%reduction in sediment yield at the HRU level.This integrated approach demonstrates the potential of combining multiple land management strategies to combat erosion effectively.展开更多
In this study,we perform particle-resolved simulations of settling spheroidal particles,considering oblate and prolate spheroids and spheres,and investigate the shape effect on the particle dynamics in suspensions wit...In this study,we perform particle-resolved simulations of settling spheroidal particles,considering oblate and prolate spheroids and spheres,and investigate the shape effect on the particle dynamics in suspensions with volume fraction 1%and 5%.We first examine the single-point statistics of the translational and rotational motion of the settling particles.The horizontal velocity has a symmetrical distribution with standard deviation dependent on the particle shape.The greater horizontal velocity fluctuations of the non-spherical particles,compared to that of spheres,are attributed to the horizontal drift of settling spheroids with oblique orientations induced by the fluid-particle and particle-particle interactions.The fluctuation of particle vertical velocity,instead,is skewed under the effect of wake-induced hydrodynamic interactions.Further,we explore the particle pair statistics,which demonstrate the formation of column-like particle micro-structures for the lowest volume fraction considered.This clustering is more pronounced for spheroidal particles than spheres,due to the stronger attractions among vertically-aligned settling spheroids.Moreover,the particle pair statistics are directly related to the collision rate among the dispersed particles.The local accumulation of oblate/prolate spheroids serves as the major mechanism to promote the particle-particle collisions in dilute suspensions.展开更多
The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or...The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or in response to environmental changes.The volume change is influenced not only by stress but also by the formation and dissociation of hydrates.This study adopted a customized apparatus for one-dimensional compression tests,allowing independent control of gas pressure and effective stress.Tests were conducted on samples with different hydrate saturations along various temperature-gas pressure-effective stress paths,yielding some conclusions related to compressibility and creep.An unusual phenomenon was observed under low-stress conditions:hydrate formation led to shrinkage rather than expansion.Three potential mechanisms behind this occurrence were discussed.As hydrate saturation increases,the yield stress rises while the compression and swelling indexes remain minimally affected.After hydrate dissociation,the compression curve of hydrate-bearing sediment drops to that of hydrate-free sediment.Once hydrate is formed,the compression curve of hydrate-free sediment gradually approaches that of hydrate-bearing sediment during the subsequent loading.Under low-stress conditions,the creep of both hydrate-free and hydrate-bearing sediments is very weak.However,when stress increases,significantly beyond the yield stress,the creep of both sediments increases significantly,with hydrate-bearing sediment exhibiting much greater creep than hydrate-free sediment.展开更多
A debris flow descending through an erodible convex colluvial bed,originating from a landslide dam and its upstream deposits,can entrain massive amounts of sediment,dramatically increasing the debris flow volume.Most ...A debris flow descending through an erodible convex colluvial bed,originating from a landslide dam and its upstream deposits,can entrain massive amounts of sediment,dramatically increasing the debris flow volume.Most existing erosion models assume that bed sediments are fully saturated,although this condition is rarely observed in nature.Therefore,a thorough understanding of debris flow overtopping erosion on a convex unsaturated bed is crucial for quantifying disaster risk.In this study,we experimentally investigated the effects of sediment composition,specifically coarse-grain size distribution and fine particle content,on the pore pressure evolution and entrainment of debris flows overriding a convex unsaturated colluvial bed.The average entrainment rate at convex sites for continuously graded bed sediment was higher than its discontinuous counterpart.The measured pore pressures within the unsaturated bed sediments were primarily generated by the passing debris flows.Furthermore,it was found that these pressures decreased as the fine particle content increased and the coarse-grain size of the erodible substrates decreased.When the coarse-grain size of the debris flow was smaller than that of the bed sediment,only a portion of the eroded material was entrained by the moving debris flow.In contrast,when the coarse-grain size of the debris flow was equal to or greater than that of the bed sediment,nearly all of the eroded material was entrained.The findings of this study could contribute to the assessment of hazard amplification and inform the design of mitigation and prevention strategies.展开更多
The lateral transport of labile organic carbon represents a critical pathway for soil organic carbon(SOC) loss,reducing organic carbon sequestration and increasing the risk of waterbody pollution.Livestock manure appl...The lateral transport of labile organic carbon represents a critical pathway for soil organic carbon(SOC) loss,reducing organic carbon sequestration and increasing the risk of waterbody pollution.Livestock manure application on croplands serves as a common fertilizer reduction practice to sustain crop yields,enhance SOC sequestration,and reduce water erosion.However,limited quantitative assessments have examined the effects of livestock manure substitution on labile organic carbon lateral loss and fluxes in long-term experiments.This study conducted a three-year field investigation on subtropical sloping croplands to assess the impact of livestock manure substitution on dissolved organic carbon(DOC) and particulate organic carbon(POC) loss via surface runoff,interflow and eroded sediments.There are four treatments:no fertilization(CK);chemical nitrogen fertilizer(SF),40% nitrogen substitution with pig manure(PMF),and 100% nitrogen substitution from pig manure(PM).Compared to SF treatment,long-term livestock manure substitution in PMF and PM treatments significantly(P<0.05) reduced annual cumulative surface runoff fluxes by 13.5 and 21.6%,respectively.Manure applications decreased annual sediment fluxes by 12.9 and 19.1%,respectively.Soil water stable aggregates for mean weight diameter(MWD) increased significantly by 37.7 and 73.6%.Annual cumulative POC loss flux via eroded sediment under PMF and PM treatments increased significantly(P<0.05) by 61.1 and 47.9%,respectively.The labile organic carbon loss fluxes,including DOC and POC losses,under PMF and PM treatments increased significantly(P<0.05) by 11.9 and 31.4%,respectively.These results demonstrate that while water erosion intensity decreases due to enhanced soil aggregate stability,the risk of labile organic carbon loss increases after long-term livestock manure substitution in subtropical sloping croplands.Future research should examine labile organic carbon lateral migration under various soil types and slope gradients for livestock manure application in subtropical agricultural ecosystem croplands to better understand extreme rainfall effects.展开更多
In sediment transport on a mobile erodible bed,near-bed particles tend to preferentially locate under specific flow regions and form an uneven bedform.These moving and mobile particles can significantly modulate turbu...In sediment transport on a mobile erodible bed,near-bed particles tend to preferentially locate under specific flow regions and form an uneven bedform.These moving and mobile particles can significantly modulate turbulence at various scales,from inertial large-scale motions to small viscous motions.This study analyzes the particle-resolved direct numerical simulation data of particle-laden two-phase flow with multilayers of particles in turbulent flows over static and mobile beds.The double-average method is adopted for energy transfer analysis.The result shows that the alternative streaky bedform in the spanwise directions correlates with the streak structures in the near-wall turbulence in the mobile bed case.The energy redistribution and exchange,as well as the dissipation,are analyzed in detail,and an energy transfer diagram is given in the last to summarize the energy transfer processes.In both the static and mobile bed cases,flow energy is introduced into the system via the work performed by volume forces acting on the mean flow.The viscous dissipations in the double mean and form-induced fields are more pronounced in the static bed case,and the work done by the fluid-particle interfacial stress in the double mean and turbulent fields is more pronounced in the mobile bed case.The prominent energy contribution in the form-induced field is the production by the form-induced stress on the mean strain in the mobile bed case.In addition,sediment transport involving a limited number of mobile particles is insufficient to capture the energy transfer processes that occur over the troughs and may intertwine the energy transfer processes over the mobile particles and the fixed particle bed.展开更多
Benthic habitat mapping is an emerging discipline in the international marine field in recent years,providing an effective tool for marine spatial planning,marine ecological management,and decision-making applications...Benthic habitat mapping is an emerging discipline in the international marine field in recent years,providing an effective tool for marine spatial planning,marine ecological management,and decision-making applications.Seabed sediment classification is one of the main contents of seabed habitat mapping.In response to the impact of remote sensing imaging quality and the limitations of acoustic measurement range,where a single data source does not fully reflect the substrate type,we proposed a high-precision seabed habitat sediment classification method that integrates data from multiple sources.Based on WorldView-2 multi-spectral remote sensing image data and multibeam bathymetry data,constructed a random forests(RF)classifier with optimal feature selection.A seabed sediment classification experiment integrating optical remote sensing and acoustic remote sensing data was carried out in the shallow water area of Wuzhizhou Island,Hainan,South China.Different seabed sediment types,such as sand,seagrass,and coral reefs were effectively identified,with an overall classification accuracy of 92%.Experimental results show that RF matrix optimized by fusing multi-source remote sensing data for feature selection were better than the classification results of simple combinations of data sources,which improved the accuracy of seabed sediment classification.Therefore,the method proposed in this paper can be effectively applied to high-precision seabed sediment classification and habitat mapping around islands and reefs.展开更多
Reliable thickness of sedimentary layers is essential for seismic hazard assessment in active fault zones, especially in regions prone to strong earthquakes. This study analyzed the seismic ambient noise data recorded...Reliable thickness of sedimentary layers is essential for seismic hazard assessment in active fault zones, especially in regions prone to strong earthquakes. This study analyzed the seismic ambient noise data recorded by 60 short-period seismic stations deployed at the Jishishan earthquake source and adjacent areas. The base-order resonance frequencies of sedimentary layers beneath the stations were determined using the horizontal-to-vertical spectral ratio method on ambient noise with diff erent frequencies. Then, a resonance-thickness formula was applied to estimate the sedimentary layer thickness at each station. Finally, the entire regional sediment thickness was obtained via interpolation. The thickness of the sedimentary layer beneath each station was estimated using the equation of the relationship between resonance frequency and sedimentary layer thickness, and fi nally, the distribution of sedimentary layer thickness in the whole region was obtained by interpolation. Results reveal notable spatial variations in sediment thickness in the source and adjacent areas. The shallow sedimentary layer in the source area is relatively thick at approximately 100 m, whereas that in Liugou Village, which is the most severely damaged area, is approximately 150-180 m. In the western region, specifically along the western edge of the Jishishan Mountain rupture and the Pourouliuhe-Cheunhua Nanshan rupture zone, the shallow sedimentary layer is approximately 30-60 m. A comparison between the distribution of seismic secondary hazards and sedimentary layer thickness highlights a strong correlation between these hazards and the amplifi cation eff ects of seismic waves. In regions with thicker sedimentary layers, ground shaking is signifi cantly amplifi ed, resulting in more serious seismic secondary hazards. In addition, the study confi rmed that secondary hazards, such as landslides and liquefaction, were more prevalent in regions with thicker sedimentary layers. These fi ndings provide an important reference for post-earthquake reconstruction, seismic risk assessment, and the development of regional disaster prevention and mitigation strategies..展开更多
China’s lakes are plagued by cadmium(Cd)pollution.Dissolved organic matter(DOM)significantly regulates Cd(II)transport properties at the sediment-water interface.Understanding the effects of different DOM components ...China’s lakes are plagued by cadmium(Cd)pollution.Dissolved organic matter(DOM)significantly regulates Cd(II)transport properties at the sediment-water interface.Understanding the effects of different DOM components on the transportation properties of Cd(II)at the sediment-water interface is essential.In this study,typical DOM from different sources was selected to study Cd(II)mobility at the sediment-water interface.Results showed that terrestrial-derived DOM(fulvic acids,FA)and autochthonous-derived DOM(α-amylase,B1)inhibit Cd(II)sequestration by sediments(42.5%and 5.8%,respectively),while anthropogenic-derived DOM(sodium dodecyl benzene sulfonate,SDBS)increased the Cd(II)adsorption capacity by sediments by 2.8%.Fluorescence quenching coupling with parallel factor analysis(EEM-PARAFAC)was used to characterize different DOM components.The results showed that FA contains three kinds of components(C1,C3:protein-like components,C2:humic-like components);SDBS contains two kinds of components(C1,C2:protein-like components);B1 contains three kinds of components(C1,C2:protein-like components,C3:humic-like components).Three complex reaction modelswere used to characterize the ability of Cd(II)complex with DOM,and it was found that the humic-like component could hardly be complex with Cd(II).Accordingly,humic-like components compete for Cd(II)adsorption sites on the sediment surface and inhibit Cd(II)adsorption fromsediments.Fourier transform infrared spectroscopy(FTIR)of the sediment surface before and after Cd(II)addition was analyzed and proved the competitive adsorption theory.This study provides a better understanding of the Cd(II)mobilization behavior at the sediment-water interface and indicates that the input of humic-like DOM will increase the bioavailability of Cd.展开更多
Dune barrier systems represent highly sought-after coastal landscapes for tourism and urban development around the world.However,a century ago,they were considered hazardous environments due to their great dynamic nat...Dune barrier systems represent highly sought-after coastal landscapes for tourism and urban development around the world.However,a century ago,they were considered hazardous environments due to their great dynamic nature.As a result,stabilization practices were considered necessary.The systematic introduction of fast-growing exotic trees helped stabilize the sand,making it easier for tourism urbanization to take place,but also leading to erosion processes.This paper aims to assess long-term changes in vegetation cover over a large temperate barrier in Argentina.This complex region includes urban resorts,afforestation zones,and protected areas.A GIS-based geospatial analysis was conducted using a large satellite database(>350 images),and the future evolution of the vegetation was modeled.The results revealed two primary spatiotemporal patterns associated with a gradual expansion of vegetation cover,accompanied by a concurrent reduction in sandy areas.In 1986,the dune area comprised 75%more surface than vegetation,whereas in 2021,it represented 60%less than vegetation.Furthermore,the 2050 scenario suggests a potential 40%reduction of dunes in certain areas.It is necessary to enhance management actions aimed at maintaining dune mobility and ensuring local and regional sediment balance.Long-term management strategies must focus on restoring native plant communities and controlling invasive species,and avoiding new dune fixation initiatives based on the introduction of exotic species.展开更多
Based on recent advancements in shale oil exploration within the Ordos Basin,this study presents a comprehensive investigation of the paleoenvironment,lithofacies assemblages and distribution,depositional mechanisms,a...Based on recent advancements in shale oil exploration within the Ordos Basin,this study presents a comprehensive investigation of the paleoenvironment,lithofacies assemblages and distribution,depositional mechanisms,and reservoir characteristics of shale oil of fine-grained sediment deposition in continental freshwater lacustrine basins,with a focus on the Chang 7_(3) sub-member of Triassic Yanchang Formation.The research integrates a variety of exploration data,including field outcrops,drilling,logging,core samples,geochemical analyses,and flume simulation.The study indicates that:(1)The paleoenvironment of the Chang 7_(3) deposition is characterized by a warm and humid climate,frequent monsoon events,and a large water depth of freshwater lacustrine basin.The paleogeomorphology exhibits an asymmetrical pattern,with steep slopes in the southwest and gentle slopes in the northeast,which can be subdivided into microgeomorphological units,including depressions and ridges in lakebed,as well as ancient channels.(2)The Chang 7_(3) sub-member is characterized by a diverse array of fine-grained sediments,including very fine sandstone,siltstone,mudstone and tuff.These sediments are primarily distributed in thin interbedded and laminated arrangements vertically.The overall grain size of the sandstone predominantly falls below 62.5μm,with individual layer thicknesses of 0.05–0.64 m.The deposits contain intact plant fragments and display various sedimentary structure,such as wavy bedding,inverse-to-normal grading sequence,and climbing ripple bedding,which indicating a depositional origin associated with density flows.(3)Flume simulation experiments have successfully replicated the transport processes and sedimentary characteristics associated with density flows.The initial phase is characterized by a density-velocity differential,resulting in a thicker,coarser sediment layer at the flow front,while the upper layers are thinner and finer in grain size.During the mid-phase,sliding water effects cause the fluid front to rise and facilitate rapid forward transport.This process generates multiple“new fronts”,enabling the long-distance transport of fine-grained sandstones,such as siltstone and argillaceous siltstone,into the center of the lake basin.(4)A sedimentary model primarily controlled by hyperpynal flows was established for the southwestern part of the basin,highlighting that the frequent occurrence of flood events and the steep slope topography in this area are primary controlling factors for the development of hyperpynal flows.(5)Sandstone and mudstone in the Chang 7_(3) sub-member exhibit micro-and nano-scale pore-throat systems,shale oil is present in various lithologies,while the content of movable oil varies considerably,with sandstone exhibiting the highest content of movable oil.(6)The fine-grained sediment complexes formed by multiple episodes of sandstones and mudstones associated with density flow in the Chang 7_(3) formation exhibit characteristics of“overall oil-bearing with differential storage capacity”.The combination of mudstone with low total organic carbon content(TOC)and siltstone is identified as the most favorable exploration target at present.展开更多
Low–angle submarine landslides pose a greater threat to offshore infrastructure compared to those with steep sliding angles.Understanding the preparation and triggering mechanism of these low–angle submarine landsli...Low–angle submarine landslides pose a greater threat to offshore infrastructure compared to those with steep sliding angles.Understanding the preparation and triggering mechanism of these low–angle submarine landslides remains a significant challenge.This study focuses on a deformed low–angle submarine landslide in the shelf–slope break of the Pearl River Mouth Basin,South China Sea,integrating sedimentology,geophysics,and geotechnology to investigate potential failure mechanisms.The architecture and deformation characteristics of the submarine landslide were elucidated by analyzing multibeam and seismic data.Within the context of the regional geological history and tectonic framework,this study focuses on the factors(e.g.,rapid sedimentation,fluid activity,and earthquakes)that potentially contributed to the submarine slope failure.Furthermore,a series of stability evaluations considering the effects of rapid sedimentation and earthquakes was conducted.Our findings indicate that the most probable triggering mechanism involves the combined effects of sedimentation controlled by sea–level fluctuations,high–pressure gas activity,and seismic events.The high–pressure gas,which acts as a long–term preconditioning factor by elevating pore pressures and reducing shear resistance within the sediment,accumulated beneath the upper and middle sections of the low–permeability stratum that was formed during sea–level rise and ultimately evolved into the sliding mass.The overpressure generated by gas accumulation predisposed the submarine slope to instability,and a frequent or moderate earthquake ultimately initiated local failure.This study enhances the mechanistic understanding of low–angle slope failures in the shelf–slope break zone and provides critical insights for assessing marine hazard risks.展开更多
Guided by the analysis of source-to-sink system,this study investigates the Paleogene Oligocene Lingshui Formation in the Qiongdongnan Basin by comparing the geological characterizes in land and sea areas and integrat...Guided by the analysis of source-to-sink system,this study investigates the Paleogene Oligocene Lingshui Formation in the Qiongdongnan Basin by comparing the geological characterizes in land and sea areas and integrating outcrop,core,drilling,logging and 3D seismic data,to systematically analyze the characteristics of the source,transport pathway,and sink during the deposition of Lingshui Formation,and reveal the patterns,controlling factors and petroleum geologic significance of the source-to-sink systems.The results are obtained in five aspects.First,during the fault-depression transition,the Qiongdongnan Basin received sediments from the provenances presenting as segments in east-west and zones in north-south,primarily with the Indosinian granites in the Shenhu Uplift in the east and the Yanshanian granites in the west.Overall,the sources are young in the southern and northern parts and old in the interior of the basin.Second,three types of sediment transport pathways are identified:paleo-valleys,fault troughs and trough-valley transitional zones.Third,based on differences in sediment supply modes,the unique source-to-sink systems during the fault-depression transition in marine rift basins are categorized into three types:exogenous,endogenous and composite.Fourth,the characteristics of these source-to-sink systems are primarily controlled by provenance,paleogeomorphology,and sea-level changes.Provenance lithology and scale dictated the composition and volume of sedimentary deposits.Paleogeomorphology influenced erosion intensity in the provenance and the development of paleodrainage systems,thereby affecting the distribution and types of sedimentary systems.Additionally,sea-level changes decided the extent of the provenance,but also regulated the sediment distribution patterns through oceanic processes such as waves and tides.Fifth,the exogenous source-to-sink systems may form large-scale reservoir bodies,the endogenous systems develop secondary pores due to presence of soluble minerals,and the composite systems demonstrate reservoir properties varying from area to area.展开更多
The spatiotemporal characterization of plume sedimentation and microorganisms is critical for developing plume ecological monitoring model.To address the limitations of traditional methods in obtaining high-quality se...The spatiotemporal characterization of plume sedimentation and microorganisms is critical for developing plume ecological monitoring model.To address the limitations of traditional methods in obtaining high-quality sediment,a novel sampling system with 6000 m operational capability and three-month endurance was developed.It is equipped with three sediment samplers,a set of formaldehyde preservation solution injection devices.The system is controlled by a low-power,timing-triggered controllers.To investigate low-disturbance rheological mechanisms,gap controlled rheological tests were conducted to optimize the structural design of the sampling and sealing assembly.Stress-controlled shear rheological tests were employed to investigate the mechanisms governing yield stress in sediments under varying temperature conditions and boundary roughness.Additionally,the coupled Eulerian-Lagrangian(CEL)method and sediment rheological constitutive models were employed to simulate tube-soil interaction dynamics and sediment disturbance.The radial heterogeneity of sediment disturbance and friction variation of the sampling tube were revealed.The tube was completely“plugged”at a penetration depth of 261 mm,providing critical data support to the penetration depth parameters.The deep-sea pressure test and South China Sea field trials demonstrated the system’s capability to collect and preserve quantitative time-series sediment samples with high fidelity.展开更多
China’s lowland rural rivers are facing severe eutrophication problems due to excessive phosphorus(P)from anthropogenic activities.However,quantifying P dynamics in a lowland rural river is challenging due to its com...China’s lowland rural rivers are facing severe eutrophication problems due to excessive phosphorus(P)from anthropogenic activities.However,quantifying P dynamics in a lowland rural river is challenging due to its complex interaction with surrounding areas.A P dynamic model(River-P)was specifically designed for lowland rural rivers to address this challenge.This modelwas coupled with the Environmental Fluid Dynamics Code(EFDC)and the Phosphorus Dynamic Model for lowland Polder systems(PDP)to characterize P dynamics under the impact of dredging in a lowland rural river.Based on a two-year(2020-2021)dataset from a representative lowland rural river in the Lake Taihu Basin,China,the coupled model was calibrated and achieved a model performance(R^(2)>0.59,RMSE<0.04 mg/L)for total P(TP)concentrations.Our research in the study river revealed that(1)the time scale for the effectiveness of sediment dredging for P control was~300 days,with an increase in P retention capacity by 74.8 kg/year and a decrease in TP concentrations of 23%after dredging.(2)Dredging significantly reduced P release from sediment by 98%,while increased P resuspension and settling capacities by 16%and 46%,respectively.(3)The sediment-water interface(SWI)plays a critical role in P transfer within the river,as resuspension accounts for 16%of TP imports,and settling accounts for 47%of TP exports.Given the large P retention capacity of lowland rural rivers,drainage ditches and ponds with macrophytes are promising approaches to enhance P retention capacity.Our study provides valuable insights for local environmental departments,allowing a comprehensive understanding of P dynamics in lowland rural rivers.This enable the evaluation of the efficacy of sediment dredging in P control and the implementation of corresponding P control measures.展开更多
基金The Natural Science Foundation of Fujian Province of China under contract No.2023J011378the National Key Research and Development Program of China under contract No.2019YFE0124700the Special Fund for Basic Scientific Research Foundation of the Third Institute of Oceanography,Ministry of Natural Resources,China under contract Nos 2019018 and 2020017.
文摘As the most important component of marine siliceous organisms,diatoms are vital primary producers of the ocean that are often used as indicators of paleoenvironmental change.To understand the response of sedimental diatoms to regional environmental changes and the factors affecting the distribution of sedimental diatoms in the Taiwan Strait,this study quantified and classified the diatoms found in surface sediments collected during four surveys from 2019 to 2020.Overall,118 diatom taxa and 44 genera were identified with total diatom abundance of 8-27353 valves/g.Four diatom assemblages representing different environments were identified.Among them,assemblageⅠrepresented a coastal environment,assemblageⅡcomprised warm water species of a coastal environment,AssemblageⅢrepresented a coastal environment affected markedly by exorheism,AssemblageⅣrepresented a group with lowest diatom abundance.Seasonal variation in total diatom abundance was controlled by seven environmental factors:depth,sea surface salinity,mean grain size,silicate,nitrite,nitrate,and phosphate.Spatiotemporal variation in each of the diatom assemblages was substantial and strongly affected by various currents,upwelling,and low-salinity water.Specifically,it was found that the succession of diatom assemblages reflects change in the range of influence of local warm currents.
文摘Noncohesive particle clusters are identified and tracked in turbulent flows to determine the breakdown and time evolution of cluster statistics and their implications for interscale mass transfer,which has connections to the classical turbulent energy cascade and its mass cascade counterpart running in parallel.In particular,the formation and dynamics of sediment and larvae clusters are of interest to coral larvae settlement in coastal regions and particularly the resilience of green-gray coastal protection solutions.Analogous cluster behavior is relevant to cloud microphysics and precipitation initiation,radiation transport and light transmission through colloids and suspensions,heat and mass transfer in particle-laden flows,and viral and pollutant transmission.Following a comparison between various clustering techniques,we adopt a density-based cluster identification algorithm based on its simplicity and efficiency,where particles are clustered based on the number of neighboring particles in their individual spheres of influence.We establish parallels with lattice-based percolation theory,as evident in the power-law scaling of the cluster size distribution near the percolation threshold.The degree of discontinuity of the phase transition associated with this percolation threshold is observed to broaden with larger Stokes numbers and thereby large-scale clustering.The sensitivity of our findings to the employed clustering algorithm is discussed.A novel cluster tracking algorithm is deployed to determine the interscale transfer rate along the particle-number phase-space dimension via accounting of cluster breakup and merger events,extending previous work on the bubble breakup cascade beneath surface breaking waves.Our findings shed light on the interaction between particle clusters and their carrier turbulent flows,with an eye toward transport models incorporating cluster characteristics and dynamics.
基金National Science Foundation of China(No.41576082)。
文摘Chlorophyll-a is the most abundant chlorophyll pigment produced by marine phytoplankton,and it bears the isotope signature of the nitrate source assimilated in the N-atoms that are embedded in its porphyrin ring.The chloropigment and its degradation product,i.e.,pheophytin-a,could be well preserved in marine sediment,usually at nanomolar level.A sensitive and accurate measurement of theδ15N of chloropigment is capable of providing rich information to greatly enhance our understanding of past nitrogen cycling,which therefore is urgently needed.Hereby,we present a successful method based on two-step HPLC separation followed by'denitrifier method'.The N-content in acetone and potassium persulfate(K_(2)S_(2)O_(8))are very critical to the precision and accuracy of the measurements,because they constitute the majority of the N contamination to the Chl-a samples.In this method,the recrystallized K_(2)S_(2)O_(8)that is used as oxidization reagent was discovered to have aδ15N background of-15‰,consolidated by repeated examinations over a period of two months.This 15N background of K_(2)S_(2)O_(8)would cause-1‰–-2‰deviation on theδ^(15)N of sample that contains nanomolar level N,and highlight the need to examine theδ^(15)N of recrystallized K_(2)S_(2)O_(8)when it is used to oxidize samples of organic nitrogen.The overall measurement ofδ^(15)N pigment is reliable and has an average analytical precision better than±0.5‰(1σ).This study establish a sensitive method for accurate measurement of theδ^(15)N of nano-molar level chlorophyll pigment,and with no doubts will advance its wide application in marine nitrogen cycling studying.
基金supported by the State Key Research Development Program of China(Grant No.2021YFC2800905-02)the National Natural Science Foundation of China(Grant No.52304208)。
文摘Identifying geohazards such as landslides and methane leakage is crucial during gas extraction from natural gas hydrate(NGH)reservoirs,and understanding reservoir settlement behavior is central to this assessment.Horizontal wells can enlarge the pressure relief zone within the formation,improving single-well productivity,and are therefore considered a promising approach for NGH development.This study examines the settlement response of hydrate-bearing sediments during depressurization using horizontal wells.A fully coupled thermal,hydraulic,mechanical,and chemical(THMC)model with representative reservoir properties(Shenhu region in the South China Sea)is presented accordingly.The simulations show that lower production pressures,while increasing gas output,also intensify formation settlement.The maximum difference in settlement between the lowest and highest production pressures reaches 0.016 m,contributing to more pronounced differential subsidence.Optimal well placement,specifically targeting a low-saturation hydrate zone containing free gas and situated adjacent to a high-saturation hydrate layer,markedly improves both gas production rate and cumulative yield,while reducing overall settlement and limiting changes in effective stress.
基金supported by grants from the National Natural Science Foundation of China(82304871)China Postdoctoral Science Foundation(2023MD734100)Sichuan Science and Technology Program(2024NSFSC1846),Sichuan Science and Technology Program(2024YFFKO185)。
文摘The stability of fruit juice has consistently been an important concern in the food processing industry,which can be time-consuming and costly.Therefore,developing accurate stability early-warning model may serve as a viable solution.Based on multiple light scattering technology,this paper collects the stability data as the training set of Triphala fruit juice over a three-month period and finds that the sediment amount reached 0.6 mg/mL,composed of ellagic acid and phlobaphene,with the solution's light transmittance fluctuating range(23%-76%)and the particle size(0.27-0.29μm)on day 75.The early warning model comprises a synergistic integration of long short-term memory and backpropagation neural network models.The model exhibits a mean absolute percentage error of 0.626%,an R^(2) of 0.911,and an accuracy of 85.71%.This model is capable of predicting key stability parameters,including sedimentation,transmittance,particle size,particle migration rate,and stability index,within a 90-day period in just 7 days,and thereby provide accurate early-stage stability alerts.
文摘Soil erosion is a fundamental physical process driving land degradation across various spatial and temporal scales.The Soil and Water Assessment Tool(SWAT)model is a robust tool for predicting soil erosion and evaluating water and soil quality within watersheds.The latest version,SWAT+,introduces advanced encoding capabilities and improved performance,making it better suited for addressing complex watershed modeling challenges.This study implemented the SWAT+model to quantify soil erosion rates within the Chehelchay watershed in northern Iran.The foundational dataset comprises a 30-meter resolution Digital Elevation Model(DEM),land use classification,soil,and weather data.Model performance was evaluated using Nash-Sutcliffe Efficiency(NSE),coefficient of determination(R^(2)),root mean square error(RMSE),and percent bias(PBIAS).The SWAT+simulation revealed substantial spatial variation in erosion patterns across the watershed,with annual sediment yields in critical HRUs,reflecting diverse erosion intensities driven by variations in land use,soil characteristics,and slope.Among the Hydrological Response Units(HRUs),50 critical units,representing approximately 9%of the total watershed area,generate sediment yields exceeding 5 tons per hectare per year.The most severe erosion occurs predominantly in the central zone of the watershed.Downstream regions exhibit minimal soil loss due to gentle topography while upstream areas maintain soil stability through protective forest cover,resulting in negligible erosion rates.Best Management Practices(BMPs)were designed to safeguard water and soil resources at a watershed level.The study evaluated three strategic conservation interventions:alfalfa cultivation,agroforestry implementation,and garden development.When applied in combination,these measures achieved approximately 30%reduction in sediment yield at the HRU level.This integrated approach demonstrates the potential of combining multiple land management strategies to combat erosion effectively.
基金supported by the National Natural Science Foundation of China(Grant Nos.92252104,12388101,and 12472224).
文摘In this study,we perform particle-resolved simulations of settling spheroidal particles,considering oblate and prolate spheroids and spheres,and investigate the shape effect on the particle dynamics in suspensions with volume fraction 1%and 5%.We first examine the single-point statistics of the translational and rotational motion of the settling particles.The horizontal velocity has a symmetrical distribution with standard deviation dependent on the particle shape.The greater horizontal velocity fluctuations of the non-spherical particles,compared to that of spheres,are attributed to the horizontal drift of settling spheroids with oblique orientations induced by the fluid-particle and particle-particle interactions.The fluctuation of particle vertical velocity,instead,is skewed under the effect of wake-induced hydrodynamic interactions.Further,we explore the particle pair statistics,which demonstrate the formation of column-like particle micro-structures for the lowest volume fraction considered.This clustering is more pronounced for spheroidal particles than spheres,due to the stronger attractions among vertically-aligned settling spheroids.Moreover,the particle pair statistics are directly related to the collision rate among the dispersed particles.The local accumulation of oblate/prolate spheroids serves as the major mechanism to promote the particle-particle collisions in dilute suspensions.
基金supported by the National Natural Science Foundation of China(Grant No.42171135)the Science and Technology Program of CNOOC Research Institute(Grant No.2023OTKK03)the“CUG Scholar”Scientific Research Funds at China University of Geosciences(Project No.2022098).
文摘The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or in response to environmental changes.The volume change is influenced not only by stress but also by the formation and dissociation of hydrates.This study adopted a customized apparatus for one-dimensional compression tests,allowing independent control of gas pressure and effective stress.Tests were conducted on samples with different hydrate saturations along various temperature-gas pressure-effective stress paths,yielding some conclusions related to compressibility and creep.An unusual phenomenon was observed under low-stress conditions:hydrate formation led to shrinkage rather than expansion.Three potential mechanisms behind this occurrence were discussed.As hydrate saturation increases,the yield stress rises while the compression and swelling indexes remain minimally affected.After hydrate dissociation,the compression curve of hydrate-bearing sediment drops to that of hydrate-free sediment.Once hydrate is formed,the compression curve of hydrate-free sediment gradually approaches that of hydrate-bearing sediment during the subsequent loading.Under low-stress conditions,the creep of both hydrate-free and hydrate-bearing sediments is very weak.However,when stress increases,significantly beyond the yield stress,the creep of both sediments increases significantly,with hydrate-bearing sediment exhibiting much greater creep than hydrate-free sediment.
基金supported by the National Key R&D Program of China(Grant No.2018YFC1505205)the Science and Technology Research Program of the Institute of Mountain Hazards and Environment,Chinese Academy of Sciences(Grant No.IMHE-ZDRW-01)Sichuan Science and Technology Program(Grant No.2024NSFSC0781).
文摘A debris flow descending through an erodible convex colluvial bed,originating from a landslide dam and its upstream deposits,can entrain massive amounts of sediment,dramatically increasing the debris flow volume.Most existing erosion models assume that bed sediments are fully saturated,although this condition is rarely observed in nature.Therefore,a thorough understanding of debris flow overtopping erosion on a convex unsaturated bed is crucial for quantifying disaster risk.In this study,we experimentally investigated the effects of sediment composition,specifically coarse-grain size distribution and fine particle content,on the pore pressure evolution and entrainment of debris flows overriding a convex unsaturated colluvial bed.The average entrainment rate at convex sites for continuously graded bed sediment was higher than its discontinuous counterpart.The measured pore pressures within the unsaturated bed sediments were primarily generated by the passing debris flows.Furthermore,it was found that these pressures decreased as the fine particle content increased and the coarse-grain size of the erodible substrates decreased.When the coarse-grain size of the debris flow was smaller than that of the bed sediment,only a portion of the eroded material was entrained by the moving debris flow.In contrast,when the coarse-grain size of the debris flow was equal to or greater than that of the bed sediment,nearly all of the eroded material was entrained.The findings of this study could contribute to the assessment of hazard amplification and inform the design of mitigation and prevention strategies.
基金funded by the Joint Funds of the National Natural Science Foundation of China (U20A20107 and U22A20562)the National Key Research and Development Program of China (2023YFD1900201-3)the International Cooperation Project,Ministry of Science and Technology of China (G2023019005L)。
文摘The lateral transport of labile organic carbon represents a critical pathway for soil organic carbon(SOC) loss,reducing organic carbon sequestration and increasing the risk of waterbody pollution.Livestock manure application on croplands serves as a common fertilizer reduction practice to sustain crop yields,enhance SOC sequestration,and reduce water erosion.However,limited quantitative assessments have examined the effects of livestock manure substitution on labile organic carbon lateral loss and fluxes in long-term experiments.This study conducted a three-year field investigation on subtropical sloping croplands to assess the impact of livestock manure substitution on dissolved organic carbon(DOC) and particulate organic carbon(POC) loss via surface runoff,interflow and eroded sediments.There are four treatments:no fertilization(CK);chemical nitrogen fertilizer(SF),40% nitrogen substitution with pig manure(PMF),and 100% nitrogen substitution from pig manure(PM).Compared to SF treatment,long-term livestock manure substitution in PMF and PM treatments significantly(P<0.05) reduced annual cumulative surface runoff fluxes by 13.5 and 21.6%,respectively.Manure applications decreased annual sediment fluxes by 12.9 and 19.1%,respectively.Soil water stable aggregates for mean weight diameter(MWD) increased significantly by 37.7 and 73.6%.Annual cumulative POC loss flux via eroded sediment under PMF and PM treatments increased significantly(P<0.05) by 61.1 and 47.9%,respectively.The labile organic carbon loss fluxes,including DOC and POC losses,under PMF and PM treatments increased significantly(P<0.05) by 11.9 and 31.4%,respectively.These results demonstrate that while water erosion intensity decreases due to enhanced soil aggregate stability,the risk of labile organic carbon loss increases after long-term livestock manure substitution in subtropical sloping croplands.Future research should examine labile organic carbon lateral migration under various soil types and slope gradients for livestock manure application in subtropical agricultural ecosystem croplands to better understand extreme rainfall effects.
基金supported by the National Natural Science Foundation of China(Grant Nos.12388101 and 12472221)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2024-oy10).
文摘In sediment transport on a mobile erodible bed,near-bed particles tend to preferentially locate under specific flow regions and form an uneven bedform.These moving and mobile particles can significantly modulate turbulence at various scales,from inertial large-scale motions to small viscous motions.This study analyzes the particle-resolved direct numerical simulation data of particle-laden two-phase flow with multilayers of particles in turbulent flows over static and mobile beds.The double-average method is adopted for energy transfer analysis.The result shows that the alternative streaky bedform in the spanwise directions correlates with the streak structures in the near-wall turbulence in the mobile bed case.The energy redistribution and exchange,as well as the dissipation,are analyzed in detail,and an energy transfer diagram is given in the last to summarize the energy transfer processes.In both the static and mobile bed cases,flow energy is introduced into the system via the work performed by volume forces acting on the mean flow.The viscous dissipations in the double mean and form-induced fields are more pronounced in the static bed case,and the work done by the fluid-particle interfacial stress in the double mean and turbulent fields is more pronounced in the mobile bed case.The prominent energy contribution in the form-induced field is the production by the form-induced stress on the mean strain in the mobile bed case.In addition,sediment transport involving a limited number of mobile particles is insufficient to capture the energy transfer processes that occur over the troughs and may intertwine the energy transfer processes over the mobile particles and the fixed particle bed.
基金Supported by the National Natural Science Foundation of China(Nos.42376185,41876111)the Shandong Provincial Natural Science Foundation(No.ZR2023MD073)。
文摘Benthic habitat mapping is an emerging discipline in the international marine field in recent years,providing an effective tool for marine spatial planning,marine ecological management,and decision-making applications.Seabed sediment classification is one of the main contents of seabed habitat mapping.In response to the impact of remote sensing imaging quality and the limitations of acoustic measurement range,where a single data source does not fully reflect the substrate type,we proposed a high-precision seabed habitat sediment classification method that integrates data from multiple sources.Based on WorldView-2 multi-spectral remote sensing image data and multibeam bathymetry data,constructed a random forests(RF)classifier with optimal feature selection.A seabed sediment classification experiment integrating optical remote sensing and acoustic remote sensing data was carried out in the shallow water area of Wuzhizhou Island,Hainan,South China.Different seabed sediment types,such as sand,seagrass,and coral reefs were effectively identified,with an overall classification accuracy of 92%.Experimental results show that RF matrix optimized by fusing multi-source remote sensing data for feature selection were better than the classification results of simple combinations of data sources,which improved the accuracy of seabed sediment classification.Therefore,the method proposed in this paper can be effectively applied to high-precision seabed sediment classification and habitat mapping around islands and reefs.
基金jointly supported by the National Natural Science Foundation of China (42204061)Special Fund for Basic Research Operations of the Institute of Geophysics,China Earthquake Administration (0419501)+1 种基金the Gansu Jishishan6.2 magnitude earthquake scientific investigation (DQJB23Y45) programthe Sichuan Provincial Natural Science Foundation (2023NSFSC0768,2023NSFSC0770)。
文摘Reliable thickness of sedimentary layers is essential for seismic hazard assessment in active fault zones, especially in regions prone to strong earthquakes. This study analyzed the seismic ambient noise data recorded by 60 short-period seismic stations deployed at the Jishishan earthquake source and adjacent areas. The base-order resonance frequencies of sedimentary layers beneath the stations were determined using the horizontal-to-vertical spectral ratio method on ambient noise with diff erent frequencies. Then, a resonance-thickness formula was applied to estimate the sedimentary layer thickness at each station. Finally, the entire regional sediment thickness was obtained via interpolation. The thickness of the sedimentary layer beneath each station was estimated using the equation of the relationship between resonance frequency and sedimentary layer thickness, and fi nally, the distribution of sedimentary layer thickness in the whole region was obtained by interpolation. Results reveal notable spatial variations in sediment thickness in the source and adjacent areas. The shallow sedimentary layer in the source area is relatively thick at approximately 100 m, whereas that in Liugou Village, which is the most severely damaged area, is approximately 150-180 m. In the western region, specifically along the western edge of the Jishishan Mountain rupture and the Pourouliuhe-Cheunhua Nanshan rupture zone, the shallow sedimentary layer is approximately 30-60 m. A comparison between the distribution of seismic secondary hazards and sedimentary layer thickness highlights a strong correlation between these hazards and the amplifi cation eff ects of seismic waves. In regions with thicker sedimentary layers, ground shaking is signifi cantly amplifi ed, resulting in more serious seismic secondary hazards. In addition, the study confi rmed that secondary hazards, such as landslides and liquefaction, were more prevalent in regions with thicker sedimentary layers. These fi ndings provide an important reference for post-earthquake reconstruction, seismic risk assessment, and the development of regional disaster prevention and mitigation strategies..
基金supported by the National Natural Science Foundation of China(Nos.42307524,and 51879103).
文摘China’s lakes are plagued by cadmium(Cd)pollution.Dissolved organic matter(DOM)significantly regulates Cd(II)transport properties at the sediment-water interface.Understanding the effects of different DOM components on the transportation properties of Cd(II)at the sediment-water interface is essential.In this study,typical DOM from different sources was selected to study Cd(II)mobility at the sediment-water interface.Results showed that terrestrial-derived DOM(fulvic acids,FA)and autochthonous-derived DOM(α-amylase,B1)inhibit Cd(II)sequestration by sediments(42.5%and 5.8%,respectively),while anthropogenic-derived DOM(sodium dodecyl benzene sulfonate,SDBS)increased the Cd(II)adsorption capacity by sediments by 2.8%.Fluorescence quenching coupling with parallel factor analysis(EEM-PARAFAC)was used to characterize different DOM components.The results showed that FA contains three kinds of components(C1,C3:protein-like components,C2:humic-like components);SDBS contains two kinds of components(C1,C2:protein-like components);B1 contains three kinds of components(C1,C2:protein-like components,C3:humic-like components).Three complex reaction modelswere used to characterize the ability of Cd(II)complex with DOM,and it was found that the humic-like component could hardly be complex with Cd(II).Accordingly,humic-like components compete for Cd(II)adsorption sites on the sediment surface and inhibit Cd(II)adsorption fromsediments.Fourier transform infrared spectroscopy(FTIR)of the sediment surface before and after Cd(II)addition was analyzed and proved the competitive adsorption theory.This study provides a better understanding of the Cd(II)mobilization behavior at the sediment-water interface and indicates that the input of humic-like DOM will increase the bioavailability of Cd.
基金supported by the Ministry of Science,Technology and Innovation of Argentina trough the project“Topografía,escurrimiento superficial y monitoreo de playas en el Partido de Villa Gesell,provincia de Buenos Aires”(Impact.AR N°106-RESOL-2022-224-APN-SACT#MCT)by the Nacional Council of Scientific and Technical Research(CONICET)through the project“Impactos de la reversión del nivel del mar en Buenos Aires,Argentina”(PIP 21/2311220200100041CO-RESOL-2021-1639-APN-DIR#CONICET)。
文摘Dune barrier systems represent highly sought-after coastal landscapes for tourism and urban development around the world.However,a century ago,they were considered hazardous environments due to their great dynamic nature.As a result,stabilization practices were considered necessary.The systematic introduction of fast-growing exotic trees helped stabilize the sand,making it easier for tourism urbanization to take place,but also leading to erosion processes.This paper aims to assess long-term changes in vegetation cover over a large temperate barrier in Argentina.This complex region includes urban resorts,afforestation zones,and protected areas.A GIS-based geospatial analysis was conducted using a large satellite database(>350 images),and the future evolution of the vegetation was modeled.The results revealed two primary spatiotemporal patterns associated with a gradual expansion of vegetation cover,accompanied by a concurrent reduction in sandy areas.In 1986,the dune area comprised 75%more surface than vegetation,whereas in 2021,it represented 60%less than vegetation.Furthermore,the 2050 scenario suggests a potential 40%reduction of dunes in certain areas.It is necessary to enhance management actions aimed at maintaining dune mobility and ensuring local and regional sediment balance.Long-term management strategies must focus on restoring native plant communities and controlling invasive species,and avoiding new dune fixation initiatives based on the introduction of exotic species.
基金Supported by the CNPC Major Science and Technology Project(2021DJ1806).
文摘Based on recent advancements in shale oil exploration within the Ordos Basin,this study presents a comprehensive investigation of the paleoenvironment,lithofacies assemblages and distribution,depositional mechanisms,and reservoir characteristics of shale oil of fine-grained sediment deposition in continental freshwater lacustrine basins,with a focus on the Chang 7_(3) sub-member of Triassic Yanchang Formation.The research integrates a variety of exploration data,including field outcrops,drilling,logging,core samples,geochemical analyses,and flume simulation.The study indicates that:(1)The paleoenvironment of the Chang 7_(3) deposition is characterized by a warm and humid climate,frequent monsoon events,and a large water depth of freshwater lacustrine basin.The paleogeomorphology exhibits an asymmetrical pattern,with steep slopes in the southwest and gentle slopes in the northeast,which can be subdivided into microgeomorphological units,including depressions and ridges in lakebed,as well as ancient channels.(2)The Chang 7_(3) sub-member is characterized by a diverse array of fine-grained sediments,including very fine sandstone,siltstone,mudstone and tuff.These sediments are primarily distributed in thin interbedded and laminated arrangements vertically.The overall grain size of the sandstone predominantly falls below 62.5μm,with individual layer thicknesses of 0.05–0.64 m.The deposits contain intact plant fragments and display various sedimentary structure,such as wavy bedding,inverse-to-normal grading sequence,and climbing ripple bedding,which indicating a depositional origin associated with density flows.(3)Flume simulation experiments have successfully replicated the transport processes and sedimentary characteristics associated with density flows.The initial phase is characterized by a density-velocity differential,resulting in a thicker,coarser sediment layer at the flow front,while the upper layers are thinner and finer in grain size.During the mid-phase,sliding water effects cause the fluid front to rise and facilitate rapid forward transport.This process generates multiple“new fronts”,enabling the long-distance transport of fine-grained sandstones,such as siltstone and argillaceous siltstone,into the center of the lake basin.(4)A sedimentary model primarily controlled by hyperpynal flows was established for the southwestern part of the basin,highlighting that the frequent occurrence of flood events and the steep slope topography in this area are primary controlling factors for the development of hyperpynal flows.(5)Sandstone and mudstone in the Chang 7_(3) sub-member exhibit micro-and nano-scale pore-throat systems,shale oil is present in various lithologies,while the content of movable oil varies considerably,with sandstone exhibiting the highest content of movable oil.(6)The fine-grained sediment complexes formed by multiple episodes of sandstones and mudstones associated with density flow in the Chang 7_(3) formation exhibit characteristics of“overall oil-bearing with differential storage capacity”.The combination of mudstone with low total organic carbon content(TOC)and siltstone is identified as the most favorable exploration target at present.
基金supported by NSFC Shiptime Sharing Project(Nos.42349302,and 42149905)the Hubei Provincial Natural Science Foundation of China(No.2024AFB515)+4 种基金the National Natural Science Foundation of China(Nos.42207173,41831280,and 42176071)the National Key R&D Program of China(No.2024YFC3082500)the Shandong Provincial Natural Science Foundation of China(No.ZR2022QD002)the Shandong Provincial Taishan Scholar Construction Project(No.tsqn202507091)the Shandong Provincial Young Innovators Team(No.2024KJH183).
文摘Low–angle submarine landslides pose a greater threat to offshore infrastructure compared to those with steep sliding angles.Understanding the preparation and triggering mechanism of these low–angle submarine landslides remains a significant challenge.This study focuses on a deformed low–angle submarine landslide in the shelf–slope break of the Pearl River Mouth Basin,South China Sea,integrating sedimentology,geophysics,and geotechnology to investigate potential failure mechanisms.The architecture and deformation characteristics of the submarine landslide were elucidated by analyzing multibeam and seismic data.Within the context of the regional geological history and tectonic framework,this study focuses on the factors(e.g.,rapid sedimentation,fluid activity,and earthquakes)that potentially contributed to the submarine slope failure.Furthermore,a series of stability evaluations considering the effects of rapid sedimentation and earthquakes was conducted.Our findings indicate that the most probable triggering mechanism involves the combined effects of sedimentation controlled by sea–level fluctuations,high–pressure gas activity,and seismic events.The high–pressure gas,which acts as a long–term preconditioning factor by elevating pore pressures and reducing shear resistance within the sediment,accumulated beneath the upper and middle sections of the low–permeability stratum that was formed during sea–level rise and ultimately evolved into the sliding mass.The overpressure generated by gas accumulation predisposed the submarine slope to instability,and a frequent or moderate earthquake ultimately initiated local failure.This study enhances the mechanistic understanding of low–angle slope failures in the shelf–slope break zone and provides critical insights for assessing marine hazard risks.
基金Supported by National Natural Science Foundation of China Enterprise Joint Fund Project(U24B200849)National Natural Science Foundation of China(91528303).
文摘Guided by the analysis of source-to-sink system,this study investigates the Paleogene Oligocene Lingshui Formation in the Qiongdongnan Basin by comparing the geological characterizes in land and sea areas and integrating outcrop,core,drilling,logging and 3D seismic data,to systematically analyze the characteristics of the source,transport pathway,and sink during the deposition of Lingshui Formation,and reveal the patterns,controlling factors and petroleum geologic significance of the source-to-sink systems.The results are obtained in five aspects.First,during the fault-depression transition,the Qiongdongnan Basin received sediments from the provenances presenting as segments in east-west and zones in north-south,primarily with the Indosinian granites in the Shenhu Uplift in the east and the Yanshanian granites in the west.Overall,the sources are young in the southern and northern parts and old in the interior of the basin.Second,three types of sediment transport pathways are identified:paleo-valleys,fault troughs and trough-valley transitional zones.Third,based on differences in sediment supply modes,the unique source-to-sink systems during the fault-depression transition in marine rift basins are categorized into three types:exogenous,endogenous and composite.Fourth,the characteristics of these source-to-sink systems are primarily controlled by provenance,paleogeomorphology,and sea-level changes.Provenance lithology and scale dictated the composition and volume of sedimentary deposits.Paleogeomorphology influenced erosion intensity in the provenance and the development of paleodrainage systems,thereby affecting the distribution and types of sedimentary systems.Additionally,sea-level changes decided the extent of the provenance,but also regulated the sediment distribution patterns through oceanic processes such as waves and tides.Fifth,the exogenous source-to-sink systems may form large-scale reservoir bodies,the endogenous systems develop secondary pores due to presence of soluble minerals,and the composite systems demonstrate reservoir properties varying from area to area.
基金supported by the National Key R&D Program of China(No.2022YFC2803900)the National Natural Science Foundation of China(No.42276191)Zhejiang University Students Science and Technology Innovation Activity Plan(New Talent Plan)(No.2024R401185).
文摘The spatiotemporal characterization of plume sedimentation and microorganisms is critical for developing plume ecological monitoring model.To address the limitations of traditional methods in obtaining high-quality sediment,a novel sampling system with 6000 m operational capability and three-month endurance was developed.It is equipped with three sediment samplers,a set of formaldehyde preservation solution injection devices.The system is controlled by a low-power,timing-triggered controllers.To investigate low-disturbance rheological mechanisms,gap controlled rheological tests were conducted to optimize the structural design of the sampling and sealing assembly.Stress-controlled shear rheological tests were employed to investigate the mechanisms governing yield stress in sediments under varying temperature conditions and boundary roughness.Additionally,the coupled Eulerian-Lagrangian(CEL)method and sediment rheological constitutive models were employed to simulate tube-soil interaction dynamics and sediment disturbance.The radial heterogeneity of sediment disturbance and friction variation of the sampling tube were revealed.The tube was completely“plugged”at a penetration depth of 261 mm,providing critical data support to the penetration depth parameters.The deep-sea pressure test and South China Sea field trials demonstrated the system’s capability to collect and preserve quantitative time-series sediment samples with high fidelity.
基金supported by the National Key Research and Development Program of China(No.2021YFD1700600)the National Natural Science Foundation of China(Nos.42222104 and 41971138)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA23020201)and the Science and Technology Planning Project of NIGLAS(No.NIGLAS2022GS10).
文摘China’s lowland rural rivers are facing severe eutrophication problems due to excessive phosphorus(P)from anthropogenic activities.However,quantifying P dynamics in a lowland rural river is challenging due to its complex interaction with surrounding areas.A P dynamic model(River-P)was specifically designed for lowland rural rivers to address this challenge.This modelwas coupled with the Environmental Fluid Dynamics Code(EFDC)and the Phosphorus Dynamic Model for lowland Polder systems(PDP)to characterize P dynamics under the impact of dredging in a lowland rural river.Based on a two-year(2020-2021)dataset from a representative lowland rural river in the Lake Taihu Basin,China,the coupled model was calibrated and achieved a model performance(R^(2)>0.59,RMSE<0.04 mg/L)for total P(TP)concentrations.Our research in the study river revealed that(1)the time scale for the effectiveness of sediment dredging for P control was~300 days,with an increase in P retention capacity by 74.8 kg/year and a decrease in TP concentrations of 23%after dredging.(2)Dredging significantly reduced P release from sediment by 98%,while increased P resuspension and settling capacities by 16%and 46%,respectively.(3)The sediment-water interface(SWI)plays a critical role in P transfer within the river,as resuspension accounts for 16%of TP imports,and settling accounts for 47%of TP exports.Given the large P retention capacity of lowland rural rivers,drainage ditches and ponds with macrophytes are promising approaches to enhance P retention capacity.Our study provides valuable insights for local environmental departments,allowing a comprehensive understanding of P dynamics in lowland rural rivers.This enable the evaluation of the efficacy of sediment dredging in P control and the implementation of corresponding P control measures.
