Organic phosphorus(OP)constitutes an important fraction of total phosphorus in lake sediments,with its mobility being influenced by mineralization and transformation of organic carbon(OC).OP and OC co-exist in various...Organic phosphorus(OP)constitutes an important fraction of total phosphorus in lake sediments,with its mobility being influenced by mineralization and transformation of organic carbon(OC).OP and OC co-exist in various forms in the environment,thus a thorough investigation on the impact of OC fractions on the release of OP in sediments should be comprehensively carried out.This study determined the chemical forms of OP and OC in the sediments over four seasons in Lake Taihu and found temporal and spatial variations in their concentrations.The concentration of total OP and total OC ranged from 133 to 348 mg/kg and 4.77 to 21.19 mg/kg,respectively.Correlation between chemical fractions of OP and OC also revealed that Na OH-extracted OP,and fulvic acid-bound and humic acid-bound OP were positively correlated with humic-OC and hot hydrolysis-OC.These results suggest that the algal-derived OC degradation and mineralization may enhance OP mineralization,converting stable or moderately active OP into active forms or inorganic phosphorus under cyanobacterial bloom.This study provides insight and guiding support for investigating the impact of organic matter components on the transformation of OP after cyanobacterial degradation in eutrophic lakes.展开更多
Elemental concentrations of the siliciclastic sediments from a sedimentary basin provide clues on paleo-weathering,paleoclimate,provenance,and tectonic setting of the basin.Records for Permo-Triassic mass extinction a...Elemental concentrations of the siliciclastic sediments from a sedimentary basin provide clues on paleo-weathering,paleoclimate,provenance,and tectonic setting of the basin.Records for Permo-Triassic mass extinction and climatic fluctuations are commonly traced from the sediments in the Gondwana basins.Nevertheless,our understanding on sedimentation,provenance,and regional tectonics of the Raniganj Basin,a Gondwana basin in the eastern India is poor.Minerals including clay particles and major and trace element concentrations of the siliciclastic sediments from different formations of the Raniganj Basin have been studied to establish the paleo-weathering,paleoclimate,provenance,and tectonic settings of the basin.This study suggests that the Talchir Formation experienced cold and dry climatic conditions at the sediment source area,while the Barakar,Raniganj,and Panchet formations had prevailing semiarid climates.The sources of the siliciclastic sediments are from the felsic rocks of the Chotanagpur Granite Gneissic Complex(CGGC).Further,the geochemical results suggest a rift-like(passive)tectonic setting for the Raniganj Basin,while few samples represent the collision tectonic setting of the basement CGGC,formed due to collision of major Indian blocks during the Paleo-Neoproterozoic time.展开更多
The study aims to investigate uranium species in the sediments of the natural-technogenic system within a sludge storage facility in Russia.The relevance of this work is underscored by the need to assess the geochemic...The study aims to investigate uranium species in the sediments of the natural-technogenic system within a sludge storage facility in Russia.The relevance of this work is underscored by the need to assess the geochemical mobility of radionuclides,a critical factor for predicting their migration and environmental impact.The objective of the research was to determine the uranium species in both peat and sedimentary rock samples of the sludge storage facility and the adjacent area.Laboratory analyses included XRD,XRF analysis using synchrotron radiation,and scanning electron microscopy to study the composition and properties of minerals.The uranium species were further identified using a modified Tessier sequential extraction method.The results revealed that uranium predominantly occurs in a stable silicate-bound form(up to 80%)in sedimentary rocks,indicating minimal geochemical mobility.In contrast,in peat deposits,uranium is primarily associated with manganese and iron oxides(30–60%)as well as organic matter(5–40%),with the most mobile forms constituting less than 5%.The decrease in uranium concentration with distance from the facility was attributed to sorption onto organic matter and co-precipitation with mineral compounds,manganese and iron oxides,which serve as effective natural sorbents.The findings highlight the critical role of organic matter and metal oxides in limiting uranium migration,thus identifying them as key components in the formation of natural barriers for radionuclides.These results are crucial for assessing environmental risks associated with radioactive waste management and for developing strategies to minimize the ecological impact of sludge storages.展开更多
This study investigates the distribution,geochemical behavior,and potential anthropogenic influences of rare earth elements(REEs)in the surface sediments of Qinghai Lake,the largest saline lake in China.A total of 36 ...This study investigates the distribution,geochemical behavior,and potential anthropogenic influences of rare earth elements(REEs)in the surface sediments of Qinghai Lake,the largest saline lake in China.A total of 36 surface sediment samples were analyzed for REE concentrations with a combination of self-organizing maps(SOM)and positive matrix factorization(PMF).Results indicate distinct enrichment patterns,with light REEs(LREEs)exhibiting higher concentrations than heavy REEs(HREEs),reflecting natural abundances and geochemical behaviors.The minimum value was found in Lu as low as 0.091 mg/kg,and the maximum concentration was exhibited in Ce at 78.877 mg/kg.Geoaccumulation index(I_(geo))analysis reveals minor to moderate enrichment of specific REEs of Sm and Nd,suggesting possible localized anthropogenic inputs,particularly near river mouths.Spatial analysis using inverse distance weighting(IDW)and self-organizing maps(SOM)highlights significant correlations between REE distributions and riverine inputs,underscoring fluvial transport's role in sedimentary REE dynamics.PMF identifies mixed natural and anthropogenic sources,with agricultural and industrial activities contributing to elevated REE levels in sediment.These findings provide critical insights into the geochemical behavior of REEs in saline lake systems and off er a foundation for pollution control and sustainable resource management in sensitive environments like Qinghai Lake.展开更多
The flow behaviors of gas and water in hydrate-bearing sediments(HBS)are significantly affected by the threshold pressure gradient(TPG).During long-term natural gas hydrates(NGHs)mining,there exists creep deformation ...The flow behaviors of gas and water in hydrate-bearing sediments(HBS)are significantly affected by the threshold pressure gradient(TPG).During long-term natural gas hydrates(NGHs)mining,there exists creep deformation in HBS,which significantly alters pore structures,makes the flow path of fluid more complex,and leads to changes in TPG.Thus,clarifying the evolution of TPG in HBS during creep is essential for NGH production,but it also confronts enormous challenges.In this study,based on the nonlinear creep constitutive model,a novel theoretical TPG model of HBS during creep is proposed that considers pore structures and hydrate pore morphology.The established model is validated against experimental data,demonstrating its ability to capture the evolution of TPG and permeability in HBS during creep.Additionally,the relationship between initial hydrate saturation and TPG of HBS during creep is revealed by sensitivity analysis.The creep strain increases with the decrease in initial hydrate saturation,leading to a greater TPG and a lower permeability.The evolution of TPG at the stable creep stage and the accelerated creep stage is primarily controlled by the Kelvin element and visco-plastic element,respectively.This novel proposed model provides a mechanistic understanding of TPG evolution in HBS during creep,and it is of great significance to optimize the exploitation of NGHs.展开更多
In this paper,core samples from the Well LS33 in the deep-water area of the Qiongdongnan Basin(QDNB)in the South China Sea were selected and analyzed by group(authigenic carbonate and terrigenous detritus)to obtain th...In this paper,core samples from the Well LS33 in the deep-water area of the Qiongdongnan Basin(QDNB)in the South China Sea were selected and analyzed by group(authigenic carbonate and terrigenous detritus)to obtain the contents of rare earth elements(REE)to explore the degree of preservation of paleo-seawater information by carbonate components and elucidate the provenance relationship between the QDNB and the Yinggehai Basin and the provenance changes in the deep-water area of the QDNB since the Oligocene.The main achievements of this paper are as follows:(1)In the process of extracting the autogenic carbonate,the iron-manganese oxide envelope on the surface of the sediment particles(which can adsorb REE or its complexes in seawater)will partially dissolve into the autogenic carbonate components,thus covering the REE geochem-ical information of paleo-seawater carried by the auto-genic carbonate.Therefore,caution should be exercised when using the geochemical characteristics of REE in the carbonate component of impure carbonate rocks to reflect the sedimentary paleoenvironment.(2)The analysis of the REE geochemical characteristics of multiple cores in the Ying-gehai-QDNB shows that there is a close provenance rela-tionship between the two Basins.The sediments in the central depression area of the Yinggehai Basin and the deep-water area in the western part of the QDNB generally contain more feldspar(Eu-rich)minerals.Since the Eocene,paleo-rivers have carried ultramafic-mafic materials originating from the western South China Sea into the sea.Affected by the transport distance and sea level changes,the content of feldspar(Eu-rich)minerals in the sediments of the QDNB from west to east gradually decreased.展开更多
Industrial activities have contributed so much to the pollution of water bodies and these pollutions have adversely affected the aquatic ecosystem.This study aimed to investigate the ecological risk evaluation of heav...Industrial activities have contributed so much to the pollution of water bodies and these pollutions have adversely affected the aquatic ecosystem.This study aimed to investigate the ecological risk evaluation of heavy metal accumulation in Aba River bottom sediments:implications for soap and detergent industry wastewater management.Varian AA240 Atomic absorption spectrometer was used to analyse heavy metals.Individual and complex ecological indices were used to evaluate heavy metal contamination in bottom sediments.According to the results,the heavy metal properties of the wastewater indicated that Fe,Pb,Cd,Cr and Cu mean concentration values were higher than the World Health Organization(WHO)and the National Environmental Standards and Regulations Enforcement Agency(NESREA)permissible limits.Heavy metal properties of the surface water in Aba River(dry seasons)showed that Pb,Cd,Cu,Mn,Fe,and Cr,mean concentrations were above the NESREA,WHO and U.S.Environmental Protection Agency(USEPA)permissible limits.Heavy metal properties of the bottom sediments of Aba River(wet and dry season)showed that Pb,Cd,and Fe mean concentrations were significantly higher than the NESREA,WHO and USEPA permissible limits.The heavy metal contamination factor(CF)of sediments obtained from Aba River during the wet and dry season was low and the CFs of each of the assayed heavy metals were less than 1(CD<1).This also signifies the existence of a low contamination in the sediments of the course streams of Aba River during wet and dry season.The pollution load index(PLI)values of Aba River(sediment)indicated that there is no metal pollution at PLI<1 in the sampled sediments.The potential ecological risk index(RI)of Aba River was less than 150(RI<150)indicating a low ecological RI.Abatement of pollutants in the wastewater to permissible concentrations required for natural environment protection is needed.展开更多
The concentrations of polycyclic aromatic hydrocarbons(PAHs),their sources and toxic equivalent(TEQ)in soil,suspended matter and bottom sediments in the Fatala River Basin ecosystem were obtained for the fi rst time t...The concentrations of polycyclic aromatic hydrocarbons(PAHs),their sources and toxic equivalent(TEQ)in soil,suspended matter and bottom sediments in the Fatala River Basin ecosystem were obtained for the fi rst time to our knowledge.Determination of 14 PAHs(ΣPAHs)was carried out using high-performance liquid chromatography.TheΣPAH content in soil ranged from 13 to 50,920(Me=820)ng/g.The composition of PAHs(high proportion of low-molecular-weight compounds and values of individual PAHs ratios)refl ected the signifi cant oil pollution of soil.Contaminated soil was localated in the central part of the Fatala River Basin.The median benzo(a)pyrene toxic equivalent of soil at the study site was 1.08(range,0.05 to 53.16)ngTEQ/g,showing generally low soil toxicity.TheΣPAH content in suspended matter was in the range of 33 to 1316(Me=309)ng/L.TheΣPAH content in bottom sediments ranged from 36 to 6943(Me=478)ng/L,corresponding to clean and moderately contaminated sediments.TheΣPAH content in bottom sediments depended on the anthropogenic impact on the Fatala River Basin territory and the bottom sediment features.Bottom sediments and suspended matter had a low toxic equivalent.展开更多
Environmental problems from heavy metals(HMs)attract global attention.Accurately identifying sources and quantitatively evaluating ecological risks are keys for HMs pollution prevention.Dongting Lake in China was inve...Environmental problems from heavy metals(HMs)attract global attention.Accurately identifying sources and quantitatively evaluating ecological risks are keys for HMs pollution prevention.Dongting Lake in China was investigated through integrated methods like positive matrix factorization and Nemerow integrated risk index to examine spatial distribution,contamination characteristics,pollution sources,and the contribution of each source and pollutant to the ecological risk of 14 HMs in its surface sediments.Results showed that the mean concentrations of HMs were 0.82-9.44 times greater than the corresponding background values.The spatial distribution of HMs varied significantly,with high values of As,Cd,Mn,Pb,Sn,Tl and Zn concentrated in the sediments from Xiangjiang inlet and Yangtze outlet;Co,Cr,Cu,Ni and V in the Lishui sediments;Hg and Sb in the sediments from Yuanjiang and Zishui inlets,respectively.The accumulation of HMs was affected by five sources:mercury mining and atmospheric deposition(F1)(17.99%),urban domestic sewage and industrial sewage discharge(F2)(24.44%),antimony ore mining and smelting(F3)(6.50%),non-ferrous metal mining and extended processing industrial sources(F4)(15.72%),and mixed sources mainly from natural sources and agricultural sources(F5)(35.35%).F1 and F2 were identified as priority pollution sources;Cd,Hg,Tl,Sb and As,especially Cd and Hg,posed relatively high ecological risks and were prioritized HMs for control.展开更多
The arsenic(As)release from sediments in great lakes is affected by various factors.In this study,the characteristics of As release fromsediments was investigated,and the As sources and sinks with the strengths in sed...The arsenic(As)release from sediments in great lakes is affected by various factors.In this study,the characteristics of As release fromsediments was investigated,and the As sources and sinks with the strengths in sediments from different areas(grass-type,algae-type,and grass-algae alternation areas)in great shallow lakes(Taihu Lake,China)were analyzed,and the influence of P competition in the process of As release was also studied.The results showed that changing trend of the values of equilibrium As concentration in sediments were consistent with the regional changes(0 to 28.12μg/L),and the sediments from algaetype areas had the higher values.The sediments from western lake and northwest lake bay were a strong As and a weak P source,and the north lake bay had the opposite trend of these two regions.Intense P source competition with As from the sediments occurred in algae-type areas.The grass-type areas had strong As and P retention capacities,indicating a sink role of sediment with high As and P sorption capacities.The degree of As and P saturation had similar trend in sediments,and the grass-type areas had the higher values,18.3%-21.4%and 15.31%-20.34%,respectively.Contribution analysis results showed that most of As release contribution was from the bottom(30-50 cm)sediments,and the surface(0-10 cm)sediments from algae-type areas contributed more to the overlying water than other region.展开更多
In the long-term exploitation of natural gas hydrate,the stress change intensifies the creep effect and leads to the destruction of pore structures,which makes it difficult to predict the permeability of hydrate reser...In the long-term exploitation of natural gas hydrate,the stress change intensifies the creep effect and leads to the destruction of pore structures,which makes it difficult to predict the permeability of hydrate reservoir.Although permeability is crucial to optimize gas recovery for gas hydrate reservoirs,until now,accurately modeling the permeability of hydrate-bearing clayey-silty sediments during the creep process remains a significant challenge.In this study,by combining the nonlinear fractional-order constitutive model and the Kozeny-Carman(KC)equation,a novel creep model for predicting the permeability of hydrate-bearing clayey-silty sediments has been proposed.In addition,experimental tests have been conducted to validate the derived model.The proposed model is further validated against other available test data.When the yield function F<0,the permeability decreases gradually due to the shrinkage of pore space.However,when the yield function F≥0,the penetrating damage bands will be generated.Results show that,once the model parameters are determined appropriately by fitting the test data,the model can also be used to predict permeability under any other stress conditions.This study has a certain guiding significance for elucidating the permeability evolution mechanisms of hydrate-bearing clayey-silty sediments during the extraction of marine gas hydrates.展开更多
Plastic pollution and microplastics in sediments are a growing concern for marine ecosystems worldwide.We examined the vertical distribution and properties of microplastics in beach sediments of Xuwen Coral Reef Natio...Plastic pollution and microplastics in sediments are a growing concern for marine ecosystems worldwide.We examined the vertical distribution and properties of microplastics in beach sediments of Xuwen Coral Reef National Nature Reserve,in Leizhou Peninsula,Zhanjiang,China.Sediment samples were taken in seven locations at 5-cm intervals from the surface to a depth of 30 cm.The vertical distribution of microplastic particles ranged from 0 to 1340 particles per kg on average of 119.05particles per kg.The most prevalent material was fibers(76%),followed by film(12%),fragments(11.2%),and foam(0.8%).The microplastics in size of 1-2 mm constituted the largest percentage(40%)of the total,followed by those in size of<1 mm(26.4%),2-3 mm(21.2%),3-4 mm(9.6%),and 4-5 mm(2.81%).Site S1 observed maximum sizes between 1 and 2 mm,S2 reported higher availability of microplastics with sizes ranging from 0.3 to 1 mm.Six different types of polymers were identified in the investigation,and mostly were polyethylene(PE)and polypropylene(PP).In general,the observation of microplastics in deeper sediments indicates that they have the ability to last for prolonged periods in the marine environment,which may present long-term hazards to benthic creatures.In conclusion,the discovery of microplastics in deep layers of coastal sediments highlights the necessity of minimizing plastic waste and enhancing management strategies to safeguard marine environments.展开更多
Subducted sediments,as an integral part of subducted slab,can strongly influence the chemistry of volcanic arc lavas,and clarify the relationship between subduction input and arc output,which is the focus of the subdu...Subducted sediments,as an integral part of subducted slab,can strongly influence the chemistry of volcanic arc lavas,and clarify the relationship between subduction input and arc output,which is the focus of the subduction factory theory in the context of plate tectonics.In this study,we analyzed major and trace element compositions of the subducting sediments from two sites[Deep Sea Drilling Program(DSDP)Site 495 and Ocean Drilling Program(ODP)Site 1039]at the different locations along the Middle America Trench.The results showed that the sediments from these two sites are mainly composed of terrigenous material,carbonate components,and biogenic silicate in different proportions.In order to reduce the effects of the variations in subduction topography on the chemical composition of sediments,we recalculated the bulk subducted sediment composition at northern and southern Central America subduction zone,and identified the Nicaragua Fracture Zone as the dividing line for northern and southern subducting sediments at Middle America Trench.Compared to the global trench subducting sediment,both the subducting sediments from northern and southern Central America subduction zone exhibit lower contents of terrigenous material-controlled elements and are more enriched in the biogenic components-controlled elements.We suggested that the variations in both chemical compositions for sediments and subduction angles are responsible for the different contributions of subducting sediments to volcanic arc magmatism in the northern Central America.展开更多
Microplastic(MP)contamination is becoming a major worldwide concern,affecting terrestrial and aquatic ecosystems.This study investigated the source,distribution,and abundance of MPs in sediments from Dongshan Bay,Fuji...Microplastic(MP)contamination is becoming a major worldwide concern,affecting terrestrial and aquatic ecosystems.This study investigated the source,distribution,and abundance of MPs in sediments from Dongshan Bay,Fujian,South China,emphasizing particularly the coastline region's susceptibility to tidal impacts in four study sites.The concentrations of MPs in the sediments in the four sites were high from 7.4 to 283.1 items/kg(dry weight).There were notable differences in abundance between the locations and tide levels.Tides influenced the distribution of MPs greatly;however,the estuary areas showed greater MPs abundance during high tide,due possibly to enhanced water turbulence and riverine inputs.Low tide indicated higher concentrations in coastal locations owing to accumulation.Popular varieties,including nylon,polypropylene,and polyethylene,were identified by polymer research,pointing to the origins from fishing,packaging,and mariculture industries.Potential sources were determined using the PCA-K-means statistical analysis,by linking the origins of MPs to domestic activities,fishing,mariculturing,shipping,and packing.Fishing and packing were shown in the Sankey diagram as the two main sources,but their effects varied with research locations and tidal regimes.This study clarified the intricate dynamics of MPs pollution,highlighting the impact of tides on its dispersal and the variety of sources that contribute to this widespread environmental problem in coastal areas.展开更多
The mound-making behavior of plateau zokors is one of the most important factors in remodeling meadow microtopography and causing soil erosion in the Yellow River source area of western China,but little is known about...The mound-making behavior of plateau zokors is one of the most important factors in remodeling meadow microtopography and causing soil erosion in the Yellow River source area of western China,but little is known about the effects of microtopography on particle size characteristics(PSC)of eroded sediments from the bare slopes of zokor mounds during different rainfall events.In this study,we analyzed the relationship of microtopographic features derived from laser point cloud data and PSC of eroded sediments at six simulated rainfall intensities(all lasting 60 min).The effects of microtopography on PSC of eroded sediments were studied via partial least squares regression(PLSR)and structural equation modeling(SEM).The results showed that:(1)15-20 minutes from the beginning of rainfall was the sensitive period of soil loss from the slopes,and the function relationship between the rate of sediment and runoff and rainfall intensity can better predict the development trend of soil erosion;(2)Intense erosion occurred mainly in the upper half of the zokor mound,while deposition was mainly limited to its lower half.It is suggested that diminished plateau zokor activity intensity can effectively prevent and control soil erosion;(3)The PSC of eroded sediment is dominated by silt,followed by sand,with clay being the least abundant,and the eroded sediments with a particle size of 10-20μm were sensitive and highly susceptible to rainfall erosion.This finding facilitates the understanding of the formation process of surface geomorphology and the mechanism of soil erosion;(4)The PLSR model indicates that microtopography has an extensive influence on eroded sediments during hydraulic erosion,and the SEM analysis results further confirm that the fractal dimension was the best parameter to represent the PSC of eroded sediments,whereas surface cutting degree was the dominant factor controlling the PSC of eroded sediments.These findings are crucial for predicting soil erosion in the Yellow River source area and provide a new perspective for understanding soil erosion mechanisms in alpine meadow ecosystems.展开更多
A novel shear damage model based on homogenization theory and a modified Mohr-Coulomb criterion is proposed to predict the full deformation process of gas hydrate-bearing sediments(GHBSs)during shearing by analyzing m...A novel shear damage model based on homogenization theory and a modified Mohr-Coulomb criterion is proposed to predict the full deformation process of gas hydrate-bearing sediments(GHBSs)during shearing by analyzing micro-mechanisms of shear deformation and failure characteristics.Then,the physical significance of the model's parameters is explored.Finally,the damage evolution and shear stress partition inside GHBSs during the shearing process are analyzed in detail.The results show that model parameters have clear physical meaning,and the shear damage model is capable of reflecting the nonlinear deformation and strain softening characteristics of GHBSs due to its ability to better describe the damage evolution and shear stress partition mechanisms inside GHBSs during the shearing process.Comparisons of experimental and theoretical results show that the global performance of the novel shear damage model is satisfactory.The model is expected to be widely adopted to analyze submarine landslide instability due to hydrate dissociation.展开更多
Shear strength of hydrate-bearing sediment is an essential parameter for assessing landslide potential ofhydrate reservoirs under exploration conditions. However, the characteristics and simulation of thisshear streng...Shear strength of hydrate-bearing sediment is an essential parameter for assessing landslide potential ofhydrate reservoirs under exploration conditions. However, the characteristics and simulation of thisshear strength under varying dissociation conditions have not been thoroughly investigated. To this end,a series of triaxial compression tests were first carried out on sediments with varying initial hydratesaturations along dissociation pathways. Combining measured data with microscale analysis, the underlyingmechanism for the evolution of shear strength in hydrate-bearing sediment was studied undervarying partial dissociation pathways. Moreover, a shear strength model for hydrate-bearing sedimentwas proposed, taking into account the hydrate saturation and the unhydrated water content. Apart fromthe parameters derived from the hydrate characteristic curve, only one additional model parameter isrequired. The proposed model was validated using measured data on hydrate sediments. The resultsindicate that the proposed model can effectively capture the shear strength behavior of hydrate-bearingsediment under varying dissociation paths. Finally, a sensitivity analysis of the model parameters wasconducted to characterize the proposed model.展开更多
This study examines the potential impacts o climate change on Lake Biwa,Japan’s largest freshwate lake,with a focus on temperature,wind speed,and pre cipitation variations.Leveraging data from the IPCC Sixth Assessme...This study examines the potential impacts o climate change on Lake Biwa,Japan’s largest freshwate lake,with a focus on temperature,wind speed,and pre cipitation variations.Leveraging data from the IPCC Sixth Assessment Report,including CCP scenarios,projecting a significant temperature rise of 3.3–5.7℃in the case o very high GHG emission power,the research investigates how these shifts may influence dissolved oxygen levels in Lake Biwa.Through a one-dimensional model incorporat ing sediment redox reactions,various scenarios where ai temperature and wind speed are changed are simulated.I is revealed that a 5℃increase in air temperature leads to decreasing 1-2 mg/L of dissolved oxygen concentrations from the surface layer to the bottom layer,while a decrease in air temperature tends to elevate 1–3 mg/L of oxygen lev els.Moreover,doubling wind speed enhances surface laye oxygen but diminishes it in deeper layers due to increased mixing.Seasonal variations in wind effects are noted with significant surface layer oxygen increases from 0.4to 0.8 mg/L during summer to autumn,increases from 0.4 to 0.8 mg/L in autumn to winter due to intensified vertica mixing.This phenomenon impacts the lake’s oxygen cycle year-round.In contrast,precipitation changes show limited impact on oxygen levels,suggesting minor influence com pared to other meteorological factors.The study suggests the necessity of comprehensive three-dimensional models that account for lake-specific and geographical factors fo accurate predictions of future water conditions.A holistic approach integrating nutrient levels,water temperature,and river inflow is deemed essential for sustainable management of Lake Biwa’s water resources,particularly in addressing precipitation variations.展开更多
We measured the content of six heavy-metal elements(Co,Cu,Zn,As,Cd,Pb)in 72 lake surface-sediment samples from the Xizang Autonomous Region(referred to as Xizang)of China,and calculated four indices:enrichment factor(...We measured the content of six heavy-metal elements(Co,Cu,Zn,As,Cd,Pb)in 72 lake surface-sediment samples from the Xizang Autonomous Region(referred to as Xizang)of China,and calculated four indices:enrichment factor(EF),geo-accumulation index(Igeo),pollution load index(PLI),and a comprehensive potential ecological risk index(RI)to explore the differences in the accumulation and the major sources of heavy metals,and to reveal the role of human activities in the ecological environment of high-elevation cold regions.Results show that the heavy-metal contents in lake surface sediment samples in eastern Xizang are much higher than those in central and western areas,and are also higher than the background value of surface soils.Their distribution can be related to regional sources of heavy metals:natural parent material(western Xizang),agriculture(eastern Xizang),mining-related industrial sources(central Xizang),and degree of development of road network(all of Xizang).The majority of lakes in Xizang have a relatively low risk of ecological harm,but there are notable regional peculiarities in the element content and evaluation indices and the lakes in eastern Xizang are at higher risk than those in central and western parts.Lakes at higher ecological risk(such as Lake Butuo(Lake 71)and Samu Co(Lake 68)),remind us that the potential influence of heavy-metal enrichment on lake sediments and aquatic plants should not be overlooked.展开更多
The Shichuanhe River,a major tributary of the lower Weihe River,is situated in Xi’an,Shaanxi Province,China.It holds signifi cant information regarding the evolution of the Northern Weihe River,making its study cruci...The Shichuanhe River,a major tributary of the lower Weihe River,is situated in Xi’an,Shaanxi Province,China.It holds signifi cant information regarding the evolution of the Northern Weihe River,making its study crucial for understanding environmental changes in the region.Despite its importance,research on the Shichuanhe River basin has thus far been primarily focused on riverbank construction,with limited exploration of its sediment characteristics.Although river sediments hold potential for guiding agricultural practices in the area,comprehensive studies on their composition and provenance remain scarce.To address this gap,a systematic sediment sampling campaign was conducted in the lower reaches of the Shichuanhe River,and detailed mineralogical analyses were performed.The results show that the sediment is predominantly composed of detrital quartz and feldspar(albite and orthoclase),with heavy minerals constituting approximately 10%–12%of the total sediment volume.The analysis of the heavy mineral assemblage reveals an absence of signifi cant contributions from igneous rocks in the sedimentary profi le.Furthermore,the distribution patterns of major,trace,and rare-earth elements in the Shichuanhe River’s argillaceous sediments exhibit similarities to those found in the Weihe River’s sediments.Elemental fractionation patterns suggest that the Shichuanhe River sediments are primarily derived from Loess Plateau sediments,aligning with fi ndings from both the Weihe River and the middle reaches of the Yellow River.展开更多
基金supported by the Project of Ecological and Environmental Protection Integration Research Institute in Yangtze River Delta(No.ZX2023SZY118)the Special Basic Research Service for the Central Level Public Welfare Research Institute(No.GYZX230409)+1 种基金the National Natural Science Foundation of China(No.42407557)the Belt and Road Special Foundation of the National Key Laboratory of Water Disaster Prevention,China(No.2023491611)。
文摘Organic phosphorus(OP)constitutes an important fraction of total phosphorus in lake sediments,with its mobility being influenced by mineralization and transformation of organic carbon(OC).OP and OC co-exist in various forms in the environment,thus a thorough investigation on the impact of OC fractions on the release of OP in sediments should be comprehensively carried out.This study determined the chemical forms of OP and OC in the sediments over four seasons in Lake Taihu and found temporal and spatial variations in their concentrations.The concentration of total OP and total OC ranged from 133 to 348 mg/kg and 4.77 to 21.19 mg/kg,respectively.Correlation between chemical fractions of OP and OC also revealed that Na OH-extracted OP,and fulvic acid-bound and humic acid-bound OP were positively correlated with humic-OC and hot hydrolysis-OC.These results suggest that the algal-derived OC degradation and mineralization may enhance OP mineralization,converting stable or moderately active OP into active forms or inorganic phosphorus under cyanobacterial bloom.This study provides insight and guiding support for investigating the impact of organic matter components on the transformation of OP after cyanobacterial degradation in eutrophic lakes.
基金funded by SERB-DST,New Delhi,India for Early Career Research(ECR/2016/001100)during 2017 to 2021.
文摘Elemental concentrations of the siliciclastic sediments from a sedimentary basin provide clues on paleo-weathering,paleoclimate,provenance,and tectonic setting of the basin.Records for Permo-Triassic mass extinction and climatic fluctuations are commonly traced from the sediments in the Gondwana basins.Nevertheless,our understanding on sedimentation,provenance,and regional tectonics of the Raniganj Basin,a Gondwana basin in the eastern India is poor.Minerals including clay particles and major and trace element concentrations of the siliciclastic sediments from different formations of the Raniganj Basin have been studied to establish the paleo-weathering,paleoclimate,provenance,and tectonic settings of the basin.This study suggests that the Talchir Formation experienced cold and dry climatic conditions at the sediment source area,while the Barakar,Raniganj,and Panchet formations had prevailing semiarid climates.The sources of the siliciclastic sediments are from the felsic rocks of the Chotanagpur Granite Gneissic Complex(CGGC).Further,the geochemical results suggest a rift-like(passive)tectonic setting for the Raniganj Basin,while few samples represent the collision tectonic setting of the basement CGGC,formed due to collision of major Indian blocks during the Paleo-Neoproterozoic time.
基金supported by the Russian Science Foundation grant number 23-27-00362,https://rscf.ru/en/project/23-27-00362/.
文摘The study aims to investigate uranium species in the sediments of the natural-technogenic system within a sludge storage facility in Russia.The relevance of this work is underscored by the need to assess the geochemical mobility of radionuclides,a critical factor for predicting their migration and environmental impact.The objective of the research was to determine the uranium species in both peat and sedimentary rock samples of the sludge storage facility and the adjacent area.Laboratory analyses included XRD,XRF analysis using synchrotron radiation,and scanning electron microscopy to study the composition and properties of minerals.The uranium species were further identified using a modified Tessier sequential extraction method.The results revealed that uranium predominantly occurs in a stable silicate-bound form(up to 80%)in sedimentary rocks,indicating minimal geochemical mobility.In contrast,in peat deposits,uranium is primarily associated with manganese and iron oxides(30–60%)as well as organic matter(5–40%),with the most mobile forms constituting less than 5%.The decrease in uranium concentration with distance from the facility was attributed to sorption onto organic matter and co-precipitation with mineral compounds,manganese and iron oxides,which serve as effective natural sorbents.The findings highlight the critical role of organic matter and metal oxides in limiting uranium migration,thus identifying them as key components in the formation of natural barriers for radionuclides.These results are crucial for assessing environmental risks associated with radioactive waste management and for developing strategies to minimize the ecological impact of sludge storages.
基金funded by the Basic Research Program of Qinghai Province(2023-ZJ-910M)。
文摘This study investigates the distribution,geochemical behavior,and potential anthropogenic influences of rare earth elements(REEs)in the surface sediments of Qinghai Lake,the largest saline lake in China.A total of 36 surface sediment samples were analyzed for REE concentrations with a combination of self-organizing maps(SOM)and positive matrix factorization(PMF).Results indicate distinct enrichment patterns,with light REEs(LREEs)exhibiting higher concentrations than heavy REEs(HREEs),reflecting natural abundances and geochemical behaviors.The minimum value was found in Lu as low as 0.091 mg/kg,and the maximum concentration was exhibited in Ce at 78.877 mg/kg.Geoaccumulation index(I_(geo))analysis reveals minor to moderate enrichment of specific REEs of Sm and Nd,suggesting possible localized anthropogenic inputs,particularly near river mouths.Spatial analysis using inverse distance weighting(IDW)and self-organizing maps(SOM)highlights significant correlations between REE distributions and riverine inputs,underscoring fluvial transport's role in sedimentary REE dynamics.PMF identifies mixed natural and anthropogenic sources,with agricultural and industrial activities contributing to elevated REE levels in sediment.These findings provide critical insights into the geochemical behavior of REEs in saline lake systems and off er a foundation for pollution control and sustainable resource management in sensitive environments like Qinghai Lake.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(Grant No.2022A1515110376)the Open Research Fund of National Center for International Research on Deep Earth Drilling and Resource Development,Ministry of Science and Technology(Grant No.DEDRD-2023-04)the Fundamental Research Funds for the Central Universities,China University of Geosciences(Grant No.107-G1323523046).
文摘The flow behaviors of gas and water in hydrate-bearing sediments(HBS)are significantly affected by the threshold pressure gradient(TPG).During long-term natural gas hydrates(NGHs)mining,there exists creep deformation in HBS,which significantly alters pore structures,makes the flow path of fluid more complex,and leads to changes in TPG.Thus,clarifying the evolution of TPG in HBS during creep is essential for NGH production,but it also confronts enormous challenges.In this study,based on the nonlinear creep constitutive model,a novel theoretical TPG model of HBS during creep is proposed that considers pore structures and hydrate pore morphology.The established model is validated against experimental data,demonstrating its ability to capture the evolution of TPG and permeability in HBS during creep.Additionally,the relationship between initial hydrate saturation and TPG of HBS during creep is revealed by sensitivity analysis.The creep strain increases with the decrease in initial hydrate saturation,leading to a greater TPG and a lower permeability.The evolution of TPG at the stable creep stage and the accelerated creep stage is primarily controlled by the Kelvin element and visco-plastic element,respectively.This novel proposed model provides a mechanistic understanding of TPG evolution in HBS during creep,and it is of great significance to optimize the exploitation of NGHs.
基金supported by The National Science and Technology Major Project under contract(No.2011ZX05025-002-03)The Project of China National Offshore Oil Corporation(CNOOC)Limited under contract(No.CCL2013ZJFNO729)The National Natural Science Foundation of China under contract(No.41530963)。
文摘In this paper,core samples from the Well LS33 in the deep-water area of the Qiongdongnan Basin(QDNB)in the South China Sea were selected and analyzed by group(authigenic carbonate and terrigenous detritus)to obtain the contents of rare earth elements(REE)to explore the degree of preservation of paleo-seawater information by carbonate components and elucidate the provenance relationship between the QDNB and the Yinggehai Basin and the provenance changes in the deep-water area of the QDNB since the Oligocene.The main achievements of this paper are as follows:(1)In the process of extracting the autogenic carbonate,the iron-manganese oxide envelope on the surface of the sediment particles(which can adsorb REE or its complexes in seawater)will partially dissolve into the autogenic carbonate components,thus covering the REE geochem-ical information of paleo-seawater carried by the auto-genic carbonate.Therefore,caution should be exercised when using the geochemical characteristics of REE in the carbonate component of impure carbonate rocks to reflect the sedimentary paleoenvironment.(2)The analysis of the REE geochemical characteristics of multiple cores in the Ying-gehai-QDNB shows that there is a close provenance rela-tionship between the two Basins.The sediments in the central depression area of the Yinggehai Basin and the deep-water area in the western part of the QDNB generally contain more feldspar(Eu-rich)minerals.Since the Eocene,paleo-rivers have carried ultramafic-mafic materials originating from the western South China Sea into the sea.Affected by the transport distance and sea level changes,the content of feldspar(Eu-rich)minerals in the sediments of the QDNB from west to east gradually decreased.
文摘Industrial activities have contributed so much to the pollution of water bodies and these pollutions have adversely affected the aquatic ecosystem.This study aimed to investigate the ecological risk evaluation of heavy metal accumulation in Aba River bottom sediments:implications for soap and detergent industry wastewater management.Varian AA240 Atomic absorption spectrometer was used to analyse heavy metals.Individual and complex ecological indices were used to evaluate heavy metal contamination in bottom sediments.According to the results,the heavy metal properties of the wastewater indicated that Fe,Pb,Cd,Cr and Cu mean concentration values were higher than the World Health Organization(WHO)and the National Environmental Standards and Regulations Enforcement Agency(NESREA)permissible limits.Heavy metal properties of the surface water in Aba River(dry seasons)showed that Pb,Cd,Cu,Mn,Fe,and Cr,mean concentrations were above the NESREA,WHO and U.S.Environmental Protection Agency(USEPA)permissible limits.Heavy metal properties of the bottom sediments of Aba River(wet and dry season)showed that Pb,Cd,and Fe mean concentrations were significantly higher than the NESREA,WHO and USEPA permissible limits.The heavy metal contamination factor(CF)of sediments obtained from Aba River during the wet and dry season was low and the CFs of each of the assayed heavy metals were less than 1(CD<1).This also signifies the existence of a low contamination in the sediments of the course streams of Aba River during wet and dry season.The pollution load index(PLI)values of Aba River(sediment)indicated that there is no metal pollution at PLI<1 in the sampled sediments.The potential ecological risk index(RI)of Aba River was less than 150(RI<150)indicating a low ecological RI.Abatement of pollutants in the wastewater to permissible concentrations required for natural environment protection is needed.
基金support of the Project of the Russian Federation represented by the Ministry of Science and Higher Education of the Russian Federation:assistance in the form of grants in accordance with paragraph 4 of article 78.1 of the Budget Code of the Russian Federation(agreement No.075-15-2023-592 on subject No.13.2251.21.0216)CEREMAC-G own research fund and a Support special fi nancier of the Ministry of Higher Education,Scientifi c Research and Innovation(MESRSI)of the Republic of Guinea.
文摘The concentrations of polycyclic aromatic hydrocarbons(PAHs),their sources and toxic equivalent(TEQ)in soil,suspended matter and bottom sediments in the Fatala River Basin ecosystem were obtained for the fi rst time to our knowledge.Determination of 14 PAHs(ΣPAHs)was carried out using high-performance liquid chromatography.TheΣPAH content in soil ranged from 13 to 50,920(Me=820)ng/g.The composition of PAHs(high proportion of low-molecular-weight compounds and values of individual PAHs ratios)refl ected the signifi cant oil pollution of soil.Contaminated soil was localated in the central part of the Fatala River Basin.The median benzo(a)pyrene toxic equivalent of soil at the study site was 1.08(range,0.05 to 53.16)ngTEQ/g,showing generally low soil toxicity.TheΣPAH content in suspended matter was in the range of 33 to 1316(Me=309)ng/L.TheΣPAH content in bottom sediments ranged from 36 to 6943(Me=478)ng/L,corresponding to clean and moderately contaminated sediments.TheΣPAH content in bottom sediments depended on the anthropogenic impact on the Fatala River Basin territory and the bottom sediment features.Bottom sediments and suspended matter had a low toxic equivalent.
基金financially supported by the Key Research and Development Program of Hunan Province,China(No.2023SK2006)the Natural Science Foundation of Hunan Province,China(No.2023JJ50057)+2 种基金the Science and Technology Plan Project of Geological Bureau of Hunan Province,China(No.HNGSTP202411)the Open Project of Key Laboratory of the Ministry of Natural Resources,China(No.BL202105)the Natural Science Foundation of Changsha City,China(No.kq2202090)。
文摘Environmental problems from heavy metals(HMs)attract global attention.Accurately identifying sources and quantitatively evaluating ecological risks are keys for HMs pollution prevention.Dongting Lake in China was investigated through integrated methods like positive matrix factorization and Nemerow integrated risk index to examine spatial distribution,contamination characteristics,pollution sources,and the contribution of each source and pollutant to the ecological risk of 14 HMs in its surface sediments.Results showed that the mean concentrations of HMs were 0.82-9.44 times greater than the corresponding background values.The spatial distribution of HMs varied significantly,with high values of As,Cd,Mn,Pb,Sn,Tl and Zn concentrated in the sediments from Xiangjiang inlet and Yangtze outlet;Co,Cr,Cu,Ni and V in the Lishui sediments;Hg and Sb in the sediments from Yuanjiang and Zishui inlets,respectively.The accumulation of HMs was affected by five sources:mercury mining and atmospheric deposition(F1)(17.99%),urban domestic sewage and industrial sewage discharge(F2)(24.44%),antimony ore mining and smelting(F3)(6.50%),non-ferrous metal mining and extended processing industrial sources(F4)(15.72%),and mixed sources mainly from natural sources and agricultural sources(F5)(35.35%).F1 and F2 were identified as priority pollution sources;Cd,Hg,Tl,Sb and As,especially Cd and Hg,posed relatively high ecological risks and were prioritized HMs for control.
基金supported by the National Natural Science Foundation(Nos.52000024 and 41907335)the Natural Science Foundation of Shanghai(No.23ZR1400700).
文摘The arsenic(As)release from sediments in great lakes is affected by various factors.In this study,the characteristics of As release fromsediments was investigated,and the As sources and sinks with the strengths in sediments from different areas(grass-type,algae-type,and grass-algae alternation areas)in great shallow lakes(Taihu Lake,China)were analyzed,and the influence of P competition in the process of As release was also studied.The results showed that changing trend of the values of equilibrium As concentration in sediments were consistent with the regional changes(0 to 28.12μg/L),and the sediments from algaetype areas had the higher values.The sediments from western lake and northwest lake bay were a strong As and a weak P source,and the north lake bay had the opposite trend of these two regions.Intense P source competition with As from the sediments occurred in algae-type areas.The grass-type areas had strong As and P retention capacities,indicating a sink role of sediment with high As and P sorption capacities.The degree of As and P saturation had similar trend in sediments,and the grass-type areas had the higher values,18.3%-21.4%and 15.31%-20.34%,respectively.Contribution analysis results showed that most of As release contribution was from the bottom(30-50 cm)sediments,and the surface(0-10 cm)sediments from algae-type areas contributed more to the overlying water than other region.
基金support from the Open Research Fund of the National Center for International Research on Deep Earth Drilling and Resource Development,Ministry of Science and Technology (Grant No.DEDRD-2023-04)the National Natural Science Foundation of China (Grant No.42306237)the Fundamental Research Funds for the Central Universities,China University of Geosciences,Wuhan (Grant No.107-G1323523046).
文摘In the long-term exploitation of natural gas hydrate,the stress change intensifies the creep effect and leads to the destruction of pore structures,which makes it difficult to predict the permeability of hydrate reservoir.Although permeability is crucial to optimize gas recovery for gas hydrate reservoirs,until now,accurately modeling the permeability of hydrate-bearing clayey-silty sediments during the creep process remains a significant challenge.In this study,by combining the nonlinear fractional-order constitutive model and the Kozeny-Carman(KC)equation,a novel creep model for predicting the permeability of hydrate-bearing clayey-silty sediments has been proposed.In addition,experimental tests have been conducted to validate the derived model.The proposed model is further validated against other available test data.When the yield function F<0,the permeability decreases gradually due to the shrinkage of pore space.However,when the yield function F≥0,the penetrating damage bands will be generated.Results show that,once the model parameters are determined appropriately by fitting the test data,the model can also be used to predict permeability under any other stress conditions.This study has a certain guiding significance for elucidating the permeability evolution mechanisms of hydrate-bearing clayey-silty sediments during the extraction of marine gas hydrates.
基金Supported by the Southern Marine Science and Engineering Guangdong Laboratory、Zhanjiang(No.ZJW-2019-08)APN、CRRP2019-09MYOnodera、Shinichi Onodera、and the SCS Scholar Grant(No.002029002008/2019)。
文摘Plastic pollution and microplastics in sediments are a growing concern for marine ecosystems worldwide.We examined the vertical distribution and properties of microplastics in beach sediments of Xuwen Coral Reef National Nature Reserve,in Leizhou Peninsula,Zhanjiang,China.Sediment samples were taken in seven locations at 5-cm intervals from the surface to a depth of 30 cm.The vertical distribution of microplastic particles ranged from 0 to 1340 particles per kg on average of 119.05particles per kg.The most prevalent material was fibers(76%),followed by film(12%),fragments(11.2%),and foam(0.8%).The microplastics in size of 1-2 mm constituted the largest percentage(40%)of the total,followed by those in size of<1 mm(26.4%),2-3 mm(21.2%),3-4 mm(9.6%),and 4-5 mm(2.81%).Site S1 observed maximum sizes between 1 and 2 mm,S2 reported higher availability of microplastics with sizes ranging from 0.3 to 1 mm.Six different types of polymers were identified in the investigation,and mostly were polyethylene(PE)and polypropylene(PP).In general,the observation of microplastics in deeper sediments indicates that they have the ability to last for prolonged periods in the marine environment,which may present long-term hazards to benthic creatures.In conclusion,the discovery of microplastics in deep layers of coastal sediments highlights the necessity of minimizing plastic waste and enhancing management strategies to safeguard marine environments.
基金The Laoshan Laboratory Project under contract No.LSKJ202204103the National Natural Science Foundation of China under contract Nos 41322036 and 41776070+1 种基金the Qingdao Postdoctoral Sustentation Foundation under contract No.QDBSH20220202147the Taishan Scholarship from Shandong Province under contract No.tstp20230643.
文摘Subducted sediments,as an integral part of subducted slab,can strongly influence the chemistry of volcanic arc lavas,and clarify the relationship between subduction input and arc output,which is the focus of the subduction factory theory in the context of plate tectonics.In this study,we analyzed major and trace element compositions of the subducting sediments from two sites[Deep Sea Drilling Program(DSDP)Site 495 and Ocean Drilling Program(ODP)Site 1039]at the different locations along the Middle America Trench.The results showed that the sediments from these two sites are mainly composed of terrigenous material,carbonate components,and biogenic silicate in different proportions.In order to reduce the effects of the variations in subduction topography on the chemical composition of sediments,we recalculated the bulk subducted sediment composition at northern and southern Central America subduction zone,and identified the Nicaragua Fracture Zone as the dividing line for northern and southern subducting sediments at Middle America Trench.Compared to the global trench subducting sediment,both the subducting sediments from northern and southern Central America subduction zone exhibit lower contents of terrigenous material-controlled elements and are more enriched in the biogenic components-controlled elements.We suggested that the variations in both chemical compositions for sediments and subduction angles are responsible for the different contributions of subducting sediments to volcanic arc magmatism in the northern Central America.
基金the Natural Science Key Foundation of Fujian ProvinceChina(No.2020J02002)+4 种基金the Hainan Province Science and Technology Special Fund(No.ZDYF2022SHFZ317)the National Natural Science Foundation of China(Nos.U2005207,41976216,41776088,42106224)the Norwegian Institute of FoodFishery and AquacultureGovernance of Marine Plastic Litter in the Arctic。
文摘Microplastic(MP)contamination is becoming a major worldwide concern,affecting terrestrial and aquatic ecosystems.This study investigated the source,distribution,and abundance of MPs in sediments from Dongshan Bay,Fujian,South China,emphasizing particularly the coastline region's susceptibility to tidal impacts in four study sites.The concentrations of MPs in the sediments in the four sites were high from 7.4 to 283.1 items/kg(dry weight).There were notable differences in abundance between the locations and tide levels.Tides influenced the distribution of MPs greatly;however,the estuary areas showed greater MPs abundance during high tide,due possibly to enhanced water turbulence and riverine inputs.Low tide indicated higher concentrations in coastal locations owing to accumulation.Popular varieties,including nylon,polypropylene,and polyethylene,were identified by polymer research,pointing to the origins from fishing,packaging,and mariculture industries.Potential sources were determined using the PCA-K-means statistical analysis,by linking the origins of MPs to domestic activities,fishing,mariculturing,shipping,and packing.Fishing and packing were shown in the Sankey diagram as the two main sources,but their effects varied with research locations and tidal regimes.This study clarified the intricate dynamics of MPs pollution,highlighting the impact of tides on its dispersal and the variety of sources that contribute to this widespread environmental problem in coastal areas.
基金financially supported by the Qinghai University Graduate Student Research and Practice Innovation Project(2025-GPKY-12)Basic Research Project of Qinghai Provincial Science and Technology Department(2021-ZJ-701)+1 种基金National Natural Science Foundation of China(U23A20159,42161068)the 111 Project of China(D18013)。
文摘The mound-making behavior of plateau zokors is one of the most important factors in remodeling meadow microtopography and causing soil erosion in the Yellow River source area of western China,but little is known about the effects of microtopography on particle size characteristics(PSC)of eroded sediments from the bare slopes of zokor mounds during different rainfall events.In this study,we analyzed the relationship of microtopographic features derived from laser point cloud data and PSC of eroded sediments at six simulated rainfall intensities(all lasting 60 min).The effects of microtopography on PSC of eroded sediments were studied via partial least squares regression(PLSR)and structural equation modeling(SEM).The results showed that:(1)15-20 minutes from the beginning of rainfall was the sensitive period of soil loss from the slopes,and the function relationship between the rate of sediment and runoff and rainfall intensity can better predict the development trend of soil erosion;(2)Intense erosion occurred mainly in the upper half of the zokor mound,while deposition was mainly limited to its lower half.It is suggested that diminished plateau zokor activity intensity can effectively prevent and control soil erosion;(3)The PSC of eroded sediment is dominated by silt,followed by sand,with clay being the least abundant,and the eroded sediments with a particle size of 10-20μm were sensitive and highly susceptible to rainfall erosion.This finding facilitates the understanding of the formation process of surface geomorphology and the mechanism of soil erosion;(4)The PLSR model indicates that microtopography has an extensive influence on eroded sediments during hydraulic erosion,and the SEM analysis results further confirm that the fractal dimension was the best parameter to represent the PSC of eroded sediments,whereas surface cutting degree was the dominant factor controlling the PSC of eroded sediments.These findings are crucial for predicting soil erosion in the Yellow River source area and provide a new perspective for understanding soil erosion mechanisms in alpine meadow ecosystems.
基金supported by the Independent Innovation Research Program of China University of Petroleum(East China)(No.27RA2215005)。
文摘A novel shear damage model based on homogenization theory and a modified Mohr-Coulomb criterion is proposed to predict the full deformation process of gas hydrate-bearing sediments(GHBSs)during shearing by analyzing micro-mechanisms of shear deformation and failure characteristics.Then,the physical significance of the model's parameters is explored.Finally,the damage evolution and shear stress partition inside GHBSs during the shearing process are analyzed in detail.The results show that model parameters have clear physical meaning,and the shear damage model is capable of reflecting the nonlinear deformation and strain softening characteristics of GHBSs due to its ability to better describe the damage evolution and shear stress partition mechanisms inside GHBSs during the shearing process.Comparisons of experimental and theoretical results show that the global performance of the novel shear damage model is satisfactory.The model is expected to be widely adopted to analyze submarine landslide instability due to hydrate dissociation.
基金supported by the National Natural Science Foundation of China(Grant No.51939011)the Science and Technology Program of CNOOC Research Institute(Grant No.2023OTKK03)supported by the program of the Youth Innovation Promotion Association,Chinese Academy of Sciences(Grant No.2020326).
文摘Shear strength of hydrate-bearing sediment is an essential parameter for assessing landslide potential ofhydrate reservoirs under exploration conditions. However, the characteristics and simulation of thisshear strength under varying dissociation conditions have not been thoroughly investigated. To this end,a series of triaxial compression tests were first carried out on sediments with varying initial hydratesaturations along dissociation pathways. Combining measured data with microscale analysis, the underlyingmechanism for the evolution of shear strength in hydrate-bearing sediment was studied undervarying partial dissociation pathways. Moreover, a shear strength model for hydrate-bearing sedimentwas proposed, taking into account the hydrate saturation and the unhydrated water content. Apart fromthe parameters derived from the hydrate characteristic curve, only one additional model parameter isrequired. The proposed model was validated using measured data on hydrate sediments. The resultsindicate that the proposed model can effectively capture the shear strength behavior of hydrate-bearingsediment under varying dissociation paths. Finally, a sensitivity analysis of the model parameters wasconducted to characterize the proposed model.
基金Open Access funding provided by Kobe UniversityThis research was partially performed by the Environment Research and Technology Development Fund(2RL-2301)of the Environmental Restoration and Conservation Agency provided by Ministry of the Environment of Japan.
文摘This study examines the potential impacts o climate change on Lake Biwa,Japan’s largest freshwate lake,with a focus on temperature,wind speed,and pre cipitation variations.Leveraging data from the IPCC Sixth Assessment Report,including CCP scenarios,projecting a significant temperature rise of 3.3–5.7℃in the case o very high GHG emission power,the research investigates how these shifts may influence dissolved oxygen levels in Lake Biwa.Through a one-dimensional model incorporat ing sediment redox reactions,various scenarios where ai temperature and wind speed are changed are simulated.I is revealed that a 5℃increase in air temperature leads to decreasing 1-2 mg/L of dissolved oxygen concentrations from the surface layer to the bottom layer,while a decrease in air temperature tends to elevate 1–3 mg/L of oxygen lev els.Moreover,doubling wind speed enhances surface laye oxygen but diminishes it in deeper layers due to increased mixing.Seasonal variations in wind effects are noted with significant surface layer oxygen increases from 0.4to 0.8 mg/L during summer to autumn,increases from 0.4 to 0.8 mg/L in autumn to winter due to intensified vertica mixing.This phenomenon impacts the lake’s oxygen cycle year-round.In contrast,precipitation changes show limited impact on oxygen levels,suggesting minor influence com pared to other meteorological factors.The study suggests the necessity of comprehensive three-dimensional models that account for lake-specific and geographical factors fo accurate predictions of future water conditions.A holistic approach integrating nutrient levels,water temperature,and river inflow is deemed essential for sustainable management of Lake Biwa’s water resources,particularly in addressing precipitation variations.
基金Under the auspices of National Natural Science Foundation of China(No.42471179,42071107)。
文摘We measured the content of six heavy-metal elements(Co,Cu,Zn,As,Cd,Pb)in 72 lake surface-sediment samples from the Xizang Autonomous Region(referred to as Xizang)of China,and calculated four indices:enrichment factor(EF),geo-accumulation index(Igeo),pollution load index(PLI),and a comprehensive potential ecological risk index(RI)to explore the differences in the accumulation and the major sources of heavy metals,and to reveal the role of human activities in the ecological environment of high-elevation cold regions.Results show that the heavy-metal contents in lake surface sediment samples in eastern Xizang are much higher than those in central and western areas,and are also higher than the background value of surface soils.Their distribution can be related to regional sources of heavy metals:natural parent material(western Xizang),agriculture(eastern Xizang),mining-related industrial sources(central Xizang),and degree of development of road network(all of Xizang).The majority of lakes in Xizang have a relatively low risk of ecological harm,but there are notable regional peculiarities in the element content and evaluation indices and the lakes in eastern Xizang are at higher risk than those in central and western parts.Lakes at higher ecological risk(such as Lake Butuo(Lake 71)and Samu Co(Lake 68)),remind us that the potential influence of heavy-metal enrichment on lake sediments and aquatic plants should not be overlooked.
基金supported by the Key Project of Natural Science Basic Research Program of Shaanxi Province(2023-JC-ZD-16).
文摘The Shichuanhe River,a major tributary of the lower Weihe River,is situated in Xi’an,Shaanxi Province,China.It holds signifi cant information regarding the evolution of the Northern Weihe River,making its study crucial for understanding environmental changes in the region.Despite its importance,research on the Shichuanhe River basin has thus far been primarily focused on riverbank construction,with limited exploration of its sediment characteristics.Although river sediments hold potential for guiding agricultural practices in the area,comprehensive studies on their composition and provenance remain scarce.To address this gap,a systematic sediment sampling campaign was conducted in the lower reaches of the Shichuanhe River,and detailed mineralogical analyses were performed.The results show that the sediment is predominantly composed of detrital quartz and feldspar(albite and orthoclase),with heavy minerals constituting approximately 10%–12%of the total sediment volume.The analysis of the heavy mineral assemblage reveals an absence of signifi cant contributions from igneous rocks in the sedimentary profi le.Furthermore,the distribution patterns of major,trace,and rare-earth elements in the Shichuanhe River’s argillaceous sediments exhibit similarities to those found in the Weihe River’s sediments.Elemental fractionation patterns suggest that the Shichuanhe River sediments are primarily derived from Loess Plateau sediments,aligning with fi ndings from both the Weihe River and the middle reaches of the Yellow River.
