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
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 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
Total organic carbon in lake surface sediments(STOC)constitutes a pivotal biogeochemical component within the critical interface of the global carbon cycle,where recently deposited organic matter undergoes burial or m...Total organic carbon in lake surface sediments(STOC)constitutes a pivotal biogeochemical component within the critical interface of the global carbon cycle,where recently deposited organic matter undergoes burial or mineralization,thereby playing a key role in carbon turnover and storage in inland water ecosystems.However,previous studies,constrained by local-scale observations and linear analytical methods,have not systematically characterized the global spatial patterns of STOC values and the mechanisms driving their variability.Here,by integrating STOC measurements from 89 lakes across the Tibetan Plateau with STOC data of 1070 lakes compiled based on a literature search,we present the first machine-learning-based assessment of global lake STOC patterns.Our results indicate that lake STOC concentrations peaked between 45°N and 70°N in the Northern Hemisphere,particularly in northern North America,whereas very high latitudes(>70°N)and mid-to low-latitude regions exhibited comparatively lower values.Structural equation modeling revealed that among basin characteristics,soil organic carbon and ice/snow cover were the strongest direct controls on lake STOC distribution,while temperature indirectly influenced STOC by modulating both variables.Although human activities affect STOC globally,their overall influence was modest.We conclude that temperature primarily governs the global spatial distribution of lake STOC concentrations through its influence on catchment processes.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
The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen conce...The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen concentration.Understanding DIN fluxes in gated estuaries is critical as these systems often serve as hotspots for nutrient transformations,influencing coastal water quality and ecosystem health.However,the subsequent interactions involving NO_(3)^(-)and NH_(4)^(+)adsorption or desorption on suspended sediments are often overlooked.To better understand the impact of these interactions on the overall NO_(3)^(-)and NH_(4)^(+)sorption or desorption and subsequently,the mobility and transport to the coastal zone,we conducted a series of NO_(3)^(-)and NH_(4)^(+)adsorption and desorption experiments.These experiments involved varying suspended sediment concentrations,particle sizes,salinities,and sea-salt ions to assess their potential effects.Results indicate that desorption of NO_(3)^(-)and NH_(4)^(+)from suspended sediments is more prominent than adsorption,with NH_(4)^(+)desorption being particularly significant.Notably,at low suspended particle concentrations and high salinity,NH_(4)^(+)desorption from sediments increased markedly,which further amplified in polyhaline conditions.This effect could result from ion pairing between NH_(4)^(+)and seawater anions,along with competition from seawater cations for sediment cation exchange sites,enhancing NH_(4)^(+)diffusion from estuarine sediments,and the elevated NH_(4)^(+)release could promote DIN transport to nearshore waters,especially in gated estuaries where sediment resuspension occurs.Given the critical role of NH_(4)^(+)in estuarine nitrogen cycling,ignoring these dynamics could lead to underestimations of DIN transport in river-estuary systems.Therefore,incorporating sediment dynamics into DIN flux estimations is crucial for accurately assessing nitrogen transport in gated estuaries.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
The sediments of crater lakes are one of the ideal archives for high-resolution paleoenvironmental reconstruction.This paper presents sedimentary records of 21 crater lakes in monsoonal China and systematically discus...The sediments of crater lakes are one of the ideal archives for high-resolution paleoenvironmental reconstruction.This paper presents sedimentary records of 21 crater lakes in monsoonal China and systematically discusses the geographical distribution and formation ages of these crater lakes.Sediment provenance of the crater lakes and its influencing factors were analyzed,and paleoenvironmental sequences and human activities records on different timescales reconstructed by crater lake sediments in monsoonal China were reviewed.The following points are highlighted:(1)Crater lakes in monsoonal China have been shown to preserve continuous long-time sediments that can exceed even 400 ka,although the chronology of some sediments in the southern part is debated and there were currently fewer long time records from the northern part;(2)the sediment provenance of crater lakes in northern China(e.g.,aeolian inputs)was different from that in the south(e.g.,the volcanic-lake rim),due to the different location and deposition conditions of crater lakes;(3)crater lake sediments have been used to reconstruct the history of climate changes on different timescales,but reconstruction studies of glacial-interglacial and decadal-annual scale records and studies of spatial comparisons of records on different timescales still need to be strengthened;(4)the anthropogenic signals,which include cultivation,logging,and industrial activity,are well documented in crater lake sediments from different areas and can therefore provide key evidence for the study of the Anthropocene.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
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
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
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
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
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
Mangrove forests are critical ecosystems for carbon sequestration,effectively capturing atmospheric carbon and permanently storing soil organic carbon(SOC)in coastal wetlands.Recent restoration and afforestation initi...Mangrove forests are critical ecosystems for carbon sequestration,effectively capturing atmospheric carbon and permanently storing soil organic carbon(SOC)in coastal wetlands.Recent restoration and afforestation initiatives have been undertaken to mitigate the rising atmospheric CO_(2) concentrations along tropical ocean coasts worldwide.The expansion of mangrove forests has garnered significant attention for elucidating their contributions to the permanent storage of carbon in both surface and subsoil layers.In this study,we investigated a recently expanding mangrove forest in the Beilun River Estuary of Guangxi Province,focusing on the abundance and sources of organic carbon(OC)in surface sediments.We also analyzed sediment grain size distribution,SOC,total nitrogen(TN)content,and stable carbon isotope composition(δ^(13)C).Additionally,we determined the molar ratio of SOC to nitrogen(C/N).The SOC content ranged from 0.25%to 6.58%,the C/N ratio varied from 9.85 to 17.73,δ^(13)C values spanned from-29.58‰to-24.93‰,andδ^(15)N values ranged from 3.10‰to 7.36‰.A strong correlation was observed between SOC and TN content.However,particle size did not significantly influence these relationships.In terms of SOC sources in the sediments,contributions from mangrove,terrestrial,and marine sources accounted for 37.1%to 99.5%,0.5%to 47.4%,and 0%to 17.6%,respectively.The findings of this study provide essential insights for evaluating and managing carbon sinks within the mangrove ecosystems of the Beibu Gulf region,contributing to more effective carbon management strategies in coastal areas.展开更多
Obtaining high-quality 10000-meter-deep seafloor sediment samples is the prerequisite and foundation for conducting deep-sea geological and environmental scientific research.The bottom structure of the deep seafloor i...Obtaining high-quality 10000-meter-deep seafloor sediment samples is the prerequisite and foundation for conducting deep-sea geological and environmental scientific research.The bottom structure of the deep seafloor is complex,and the physical and mechanical properties and disturbance resistance of sediments of different lithologies vary greatly,so the sediment sampler inevitably disturbs the sediments during the sampling process and affects the quality of the sediment samples.A new type of deep-sea sediment pressure retaining sampler is introduced,the force state and elastic–plastic state of the sampler destroying sediments are analyzed,the radial disturbance model of sediment coring based on the spherical cavity expansion theory is established,and the radius of sediments undergoing plastic deformation around the spherical holes is used as an index for evaluating the radial disturbance of sediments.The distribution of stress and strain fields in the sediments during the expansion of the spherical cavity and the influencing factors of the radius of the radially disturbed region(plastic region)are analyzed using an arithmetic example,and the influence law is analyzed.A sediment disturbance experimental platform was built indoors to simulate the sediment coring process.The radial stress field and pore water pressure of the sediment during the coring process were monitored by sensors arranged inside the sediment,and the results of indoor tests verified the correctness of the perturbation theory model.The sampler was carried aboard the deep-sea manned submersible FENDOUZHE and conducted on-site tests at depths of 9298.4 and 9142.8 m in the Kuril-Kamchatka Trench.Pressure-preserved sediment samples were retrieved,with preservation rates of 94.21%and 92.02%,respectively,which are much higher than the current technical indicator of 80%of pressure-holding ratio for deep-sea sediments.The retrieved sediments have obvious stratification characteristics and little disturbance.展开更多
Modified potential ecological risk index （MRI） was proposed based on the potential ecological risk index （RI） and risk assessment code （RAC） by modifying an index. The modified index was relevant to the chemical...Modified potential ecological risk index （MRI） was proposed based on the potential ecological risk index （RI） and risk assessment code （RAC） by modifying an index. The modified index was relevant to the chemical speciation of heavy metals. Xiawan Port, a typical region contaminated by industrial production, was selected as a case study area. The total concentrations and chemical speciation of heavy metals in sediments of Xiawan Port were analyzed. The experimental data indicate that Xiawan Port is seriously polluted by heavy metals, especially by Cd. The risks of heavy metals are evaluated by RI, RAC and MRI, respectively. The resluts of MRI show that the risks of heavy metals are in the decreasing order of Cd〉Pb〉Cu〉Zn. Comparison of results by different methods reveals that MRI integrates the characters of RI and RAC. MRI is recognized to be useful for risk managemnt of heavy metals in sediments.展开更多
Biogenic silica content was determined in 25 surface sediment samples from the southern South China Sea to study its distribution and its modern oceanic environmental significance, which may provide further scientific...Biogenic silica content was determined in 25 surface sediment samples from the southern South China Sea to study its distribution and its modern oceanic environmental significance, which may provide further scientific evidence for paleoceanography explaination. This study showed that biogenic silica content in surface sediments and its water depth have evidently positive correlation, and the correlation coefficient was up to 0.782. Biogenic silica content was very low in continental shelf shallows and could not reflect the productivity of siliceous micropaleontology in surface waters, which may be affected by sedimentary types and terrigenous matter dilution. Distribution of biogenic silica content in surface sediments from deep water areas showed that it could not only reflect the paleoproductivity of siliceous micropaleontology in surface waters, but also indicate the strong or feeble upwelling. Thus, it was further confirmed that using biogenic silica content in sediments to trace upwelling and its change was effective and reliable. The analyzed result showed that radiolariia and poriferous specula have more contribution for biogenic opal, comparing with diatom in surface sediments from the northern studied area, probably owing to the diatom dissolved easily away and eaten by other organisms with little effort. In the upwelling areas, radiolarian, diatom and poriferous specula all approximately showed high abundance, which was consistent with high biogenic silica content.展开更多
Hongfeng Lake,a key drinking-water source located in Karst areas,was selected to analyze the microorganisms associated with nitrogen cycle.Dilution plate method and most probable number method were used to determine t...Hongfeng Lake,a key drinking-water source located in Karst areas,was selected to analyze the microorganisms associated with nitrogen cycle.Dilution plate method and most probable number method were used to determine the distribution condition of ammonifier,ammonium-oxidizing bacteria,nitrite-oxidizing bacteria and denitrifier in surface sediment in eight sites.The results showed that the amount of ammonifier,ammonium-oxidizing bacteria,nitrite-oxidizing bacteria and denitrifier in eight sites were 104-106 CFU/g,105-107 MPN/g,105-108 MPN/g and 105-109 MPN/g,respectively.The sampling site with the largest amount of denitrifier was Daposhang,and the other sampling sites had no significant difference;the sampling site of Huyudong bridge had the largest amount of ammonium-oxidizing bacteria;the amount of nitrite-oxidizing bacteria in Xinzhuang was higher than that of other sampling sites;the sampling site of Daposhang had the larger amount of denitrifier.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 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National Natural Science Foundation of China,No.42225105,No.42494821,No.42201175The China Postdoctoral Science Foundation,No.2023M733605。
文摘Total organic carbon in lake surface sediments(STOC)constitutes a pivotal biogeochemical component within the critical interface of the global carbon cycle,where recently deposited organic matter undergoes burial or mineralization,thereby playing a key role in carbon turnover and storage in inland water ecosystems.However,previous studies,constrained by local-scale observations and linear analytical methods,have not systematically characterized the global spatial patterns of STOC values and the mechanisms driving their variability.Here,by integrating STOC measurements from 89 lakes across the Tibetan Plateau with STOC data of 1070 lakes compiled based on a literature search,we present the first machine-learning-based assessment of global lake STOC patterns.Our results indicate that lake STOC concentrations peaked between 45°N and 70°N in the Northern Hemisphere,particularly in northern North America,whereas very high latitudes(>70°N)and mid-to low-latitude regions exhibited comparatively lower values.Structural equation modeling revealed that among basin characteristics,soil organic carbon and ice/snow cover were the strongest direct controls on lake STOC distribution,while temperature indirectly influenced STOC by modulating both variables.Although human activities affect STOC globally,their overall influence was modest.We conclude that temperature primarily governs the global spatial distribution of lake STOC concentrations through its influence on catchment processes.
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 Tianjin Key R&D Program(No.21YFSNSN00220)。
文摘The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen concentration.Understanding DIN fluxes in gated estuaries is critical as these systems often serve as hotspots for nutrient transformations,influencing coastal water quality and ecosystem health.However,the subsequent interactions involving NO_(3)^(-)and NH_(4)^(+)adsorption or desorption on suspended sediments are often overlooked.To better understand the impact of these interactions on the overall NO_(3)^(-)and NH_(4)^(+)sorption or desorption and subsequently,the mobility and transport to the coastal zone,we conducted a series of NO_(3)^(-)and NH_(4)^(+)adsorption and desorption experiments.These experiments involved varying suspended sediment concentrations,particle sizes,salinities,and sea-salt ions to assess their potential effects.Results indicate that desorption of NO_(3)^(-)and NH_(4)^(+)from suspended sediments is more prominent than adsorption,with NH_(4)^(+)desorption being particularly significant.Notably,at low suspended particle concentrations and high salinity,NH_(4)^(+)desorption from sediments increased markedly,which further amplified in polyhaline conditions.This effect could result from ion pairing between NH_(4)^(+)and seawater anions,along with competition from seawater cations for sediment cation exchange sites,enhancing NH_(4)^(+)diffusion from estuarine sediments,and the elevated NH_(4)^(+)release could promote DIN transport to nearshore waters,especially in gated estuaries where sediment resuspension occurs.Given the critical role of NH_(4)^(+)in estuarine nitrogen cycling,ignoring these dynamics could lead to underestimations of DIN transport in river-estuary systems.Therefore,incorporating sediment dynamics into DIN flux estimations is crucial for accurately assessing nitrogen transport in gated estuaries.
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.
基金supported by the National Natural Science Foundation of China(Nos.41888101,41721002)the National Key Research and Development Program of China(No.2022YFF0801101)+2 种基金the Fundamental Research Funds for the Central Universities,the China Postdoctoral Science Foundation(No.2022M713024)the CAS Youth Interdisciplinary Team(No.JCTD-2021-05)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2018498).
文摘The sediments of crater lakes are one of the ideal archives for high-resolution paleoenvironmental reconstruction.This paper presents sedimentary records of 21 crater lakes in monsoonal China and systematically discusses the geographical distribution and formation ages of these crater lakes.Sediment provenance of the crater lakes and its influencing factors were analyzed,and paleoenvironmental sequences and human activities records on different timescales reconstructed by crater lake sediments in monsoonal China were reviewed.The following points are highlighted:(1)Crater lakes in monsoonal China have been shown to preserve continuous long-time sediments that can exceed even 400 ka,although the chronology of some sediments in the southern part is debated and there were currently fewer long time records from the northern part;(2)the sediment provenance of crater lakes in northern China(e.g.,aeolian inputs)was different from that in the south(e.g.,the volcanic-lake rim),due to the different location and deposition conditions of crater lakes;(3)crater lake sediments have been used to reconstruct the history of climate changes on different timescales,but reconstruction studies of glacial-interglacial and decadal-annual scale records and studies of spatial comparisons of records on different timescales still need to be strengthened;(4)the anthropogenic signals,which include cultivation,logging,and industrial activity,are well documented in crater lake sediments from different areas and can therefore provide key evidence for the study of the Anthropocene.
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 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The National Natural Science Foundation of China under contract No.42476043the Guangxi Key Research and Development Project under contract No.AB21076016+2 种基金the Scientific Research and Technology Development Project of Qinzhou under contract No.202116623the Natural Science Foundation of Guangxi under contract No.2021GXNSFAA075013the China College Students’Innovation and Entrepreneurship Training Program Project under contract No.S202411607002。
文摘Mangrove forests are critical ecosystems for carbon sequestration,effectively capturing atmospheric carbon and permanently storing soil organic carbon(SOC)in coastal wetlands.Recent restoration and afforestation initiatives have been undertaken to mitigate the rising atmospheric CO_(2) concentrations along tropical ocean coasts worldwide.The expansion of mangrove forests has garnered significant attention for elucidating their contributions to the permanent storage of carbon in both surface and subsoil layers.In this study,we investigated a recently expanding mangrove forest in the Beilun River Estuary of Guangxi Province,focusing on the abundance and sources of organic carbon(OC)in surface sediments.We also analyzed sediment grain size distribution,SOC,total nitrogen(TN)content,and stable carbon isotope composition(δ^(13)C).Additionally,we determined the molar ratio of SOC to nitrogen(C/N).The SOC content ranged from 0.25%to 6.58%,the C/N ratio varied from 9.85 to 17.73,δ^(13)C values spanned from-29.58‰to-24.93‰,andδ^(15)N values ranged from 3.10‰to 7.36‰.A strong correlation was observed between SOC and TN content.However,particle size did not significantly influence these relationships.In terms of SOC sources in the sediments,contributions from mangrove,terrestrial,and marine sources accounted for 37.1%to 99.5%,0.5%to 47.4%,and 0%to 17.6%,respectively.The findings of this study provide essential insights for evaluating and managing carbon sinks within the mangrove ecosystems of the Beibu Gulf region,contributing to more effective carbon management strategies in coastal areas.
基金supported by the National Key Research and Development Program of China(Nos.2023YFC2809304 and 2022YFC2805904).
文摘Obtaining high-quality 10000-meter-deep seafloor sediment samples is the prerequisite and foundation for conducting deep-sea geological and environmental scientific research.The bottom structure of the deep seafloor is complex,and the physical and mechanical properties and disturbance resistance of sediments of different lithologies vary greatly,so the sediment sampler inevitably disturbs the sediments during the sampling process and affects the quality of the sediment samples.A new type of deep-sea sediment pressure retaining sampler is introduced,the force state and elastic–plastic state of the sampler destroying sediments are analyzed,the radial disturbance model of sediment coring based on the spherical cavity expansion theory is established,and the radius of sediments undergoing plastic deformation around the spherical holes is used as an index for evaluating the radial disturbance of sediments.The distribution of stress and strain fields in the sediments during the expansion of the spherical cavity and the influencing factors of the radius of the radially disturbed region(plastic region)are analyzed using an arithmetic example,and the influence law is analyzed.A sediment disturbance experimental platform was built indoors to simulate the sediment coring process.The radial stress field and pore water pressure of the sediment during the coring process were monitored by sensors arranged inside the sediment,and the results of indoor tests verified the correctness of the perturbation theory model.The sampler was carried aboard the deep-sea manned submersible FENDOUZHE and conducted on-site tests at depths of 9298.4 and 9142.8 m in the Kuril-Kamchatka Trench.Pressure-preserved sediment samples were retrieved,with preservation rates of 94.21%and 92.02%,respectively,which are much higher than the current technical indicator of 80%of pressure-holding ratio for deep-sea sediments.The retrieved sediments have obvious stratification characteristics and little disturbance.
基金Projects (51039001, 50978087, 51009063, 50808071) supported by the National Natural Science Foundation of ChinaProject (SX2010-026) supported by State Council Three Gorges Project Construction Committee Executive Office,China+2 种基金Project (2009ZX07212-001) supported by Ministry of Environmental Protection of ChinaProject (BYHGLC-2010-02) supported by Guangzhou Water Authority,ChinaProject (CX2010B157) supported by Hunan Provincial Innovation Foundation for Postgraduate,China
文摘Modified potential ecological risk index （MRI） was proposed based on the potential ecological risk index （RI） and risk assessment code （RAC） by modifying an index. The modified index was relevant to the chemical speciation of heavy metals. Xiawan Port, a typical region contaminated by industrial production, was selected as a case study area. The total concentrations and chemical speciation of heavy metals in sediments of Xiawan Port were analyzed. The experimental data indicate that Xiawan Port is seriously polluted by heavy metals, especially by Cd. The risks of heavy metals are evaluated by RI, RAC and MRI, respectively. The resluts of MRI show that the risks of heavy metals are in the decreasing order of Cd〉Pb〉Cu〉Zn. Comparison of results by different methods reveals that MRI integrates the characters of RI and RAC. MRI is recognized to be useful for risk managemnt of heavy metals in sediments.
基金National Natural Science Foundation of China (No. 40476024)National Key Technology R&D Program (No. 2006BAB19B03)+1 种基金supported by Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences (No. MSGL0613)the Knowledge Innovation Program of the Chinese Academy of Sciences (No. SQ200808)
文摘Biogenic silica content was determined in 25 surface sediment samples from the southern South China Sea to study its distribution and its modern oceanic environmental significance, which may provide further scientific evidence for paleoceanography explaination. This study showed that biogenic silica content in surface sediments and its water depth have evidently positive correlation, and the correlation coefficient was up to 0.782. Biogenic silica content was very low in continental shelf shallows and could not reflect the productivity of siliceous micropaleontology in surface waters, which may be affected by sedimentary types and terrigenous matter dilution. Distribution of biogenic silica content in surface sediments from deep water areas showed that it could not only reflect the paleoproductivity of siliceous micropaleontology in surface waters, but also indicate the strong or feeble upwelling. Thus, it was further confirmed that using biogenic silica content in sediments to trace upwelling and its change was effective and reliable. The analyzed result showed that radiolariia and poriferous specula have more contribution for biogenic opal, comparing with diatom in surface sediments from the northern studied area, probably owing to the diatom dissolved easily away and eaten by other organisms with little effort. In the upwelling areas, radiolarian, diatom and poriferous specula all approximately showed high abundance, which was consistent with high biogenic silica content.
基金Supported by Science and Technology Found Project of Guizhou Province(QKH J[2008]2239)~~
文摘Hongfeng Lake,a key drinking-water source located in Karst areas,was selected to analyze the microorganisms associated with nitrogen cycle.Dilution plate method and most probable number method were used to determine the distribution condition of ammonifier,ammonium-oxidizing bacteria,nitrite-oxidizing bacteria and denitrifier in surface sediment in eight sites.The results showed that the amount of ammonifier,ammonium-oxidizing bacteria,nitrite-oxidizing bacteria and denitrifier in eight sites were 104-106 CFU/g,105-107 MPN/g,105-108 MPN/g and 105-109 MPN/g,respectively.The sampling site with the largest amount of denitrifier was Daposhang,and the other sampling sites had no significant difference;the sampling site of Huyudong bridge had the largest amount of ammonium-oxidizing bacteria;the amount of nitrite-oxidizing bacteria in Xinzhuang was higher than that of other sampling sites;the sampling site of Daposhang had the larger amount of denitrifier.
