Hydrothermal plumes released from the eruption of sea floor hydrothermal fluids contain large amounts of oreforming materials. They precipitate within certain distances from the hydrothermal vent. Six surficial sedime...Hydrothermal plumes released from the eruption of sea floor hydrothermal fluids contain large amounts of oreforming materials. They precipitate within certain distances from the hydrothermal vent. Six surficial sediment samples from the Southwest Indian Ridge（SWIR） were analyzed by a portable X-ray fluorescence（PXRF） analyzer on board to find a favorable method fast and efficient enough for sea floor sulfide sediment geochemical exploration. These sediments were sampled near, at a moderate distance from, or far away from hydrothermal vents. The results demonstrate that the PXRF is effective in determining the enrichment characteristics of the oreforming elements in the calcareous sediments from the mid-ocean ridge. Sediment samples（〉40 mesh） have high levels of elemental copper, zinc, iron, and manganese, and levels of these elements in sediments finer than 40 mesh are lower and relatively stable. This may be due to relatively high levels of basalt debris/glass in the coarse sediments, which are consistent with the results obtained by microscopic observation. The results also show clear zoning of elements copper, zinc, arsenic, iron, and manganese in the surficial sediments around the hydrothermal vent. Sediments near the vent show relatively high content of the ore-forming elements and either high ratios of copper to iron content and zinc to iron content or high ratios of copper to manganese content and zinc to manganese content. These findings show that the content of the ore-forming elements in the sediments around hydrothermal vents are mainly influenced by the distance of sediments to the vent, rather than grain size. In this way, the PXRF analysis of surface sediment geochemistry is found to satisfy the requirements of recognition geochemical anomaly in mid-ocean ridge sediments. Sediments with diameters finer than 40 mesh should be used as analytical samples in the geochemical exploration for hydrothermal vents on mid-oceanic ridges. The results concerning copper, zinc, arsenic, iron, and manganese and their ratio features can be used as indicators in sediment geochemical exploration of seafloor sulfides.展开更多
This work focuses on the production of a new composite material using Yellow River sediment and coal slime ash via alkali-activating method. XRD, FTIR and SEM/EDS were used to characterize the alkali-activated product...This work focuses on the production of a new composite material using Yellow River sediment and coal slime ash via alkali-activating method. XRD, FTIR and SEM/EDS were used to characterize the alkali-activated products and microstructure of the composite material. Compressive strength was tested to characterize the mechanical property of the composite material. It is found that the compressive strength of the Yellow River sediment-coal slime ash composites increases as the added Ca（OH）_2 content grows. The compressive strength increases fast in the early stage but slowly after 28 days. The strength of the composites can be significantly improved via the addition of small amount of Na OH and gypsum. The products（C-S-H, ettringite and CaCO_3）, especially C-S-H, make much contribution to the enhancement of strength. The highest strength of the composites can reach 14.4 MPa after 90 days curing with 5% Ca（OH）_2, 0.2% NaOH and 7.5% gypsum. The improved properties of the composites show great potential of utilizing Yellow River sediment for inexpensive construction materials.展开更多
Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reduc...Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria（SRB） on mercury（Hg） methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury（DMe Hg） in the overlying water of the control cores with bioactivity maintained（BAC） and cores with only sulfate-reducing bacteria inhibited（SRBI） and bacteria fully inhibited（BACI） were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations（r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively）. The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster（hgc AB）, besides SRB,causing Hg methylation in the sediment–water system.展开更多
The response to the catchment changes of the sedimentary environment of the western intertidal flat of Yalu River Estuary was investigated by analyzing the vertical variations of the grain size of sediment cores,along...The response to the catchment changes of the sedimentary environment of the western intertidal flat of Yalu River Estuary was investigated by analyzing the vertical variations of the grain size of sediment cores,along with the hydrologic data and human activities in the catchment.The results demonstrated a stepwise decreasing trend for the variations of both the sediment load and water discharge into the sea,which could be divided into three stages as 1958–1970,1971–1990 and 1991–2009.Reservoir construction and the changes of catchment vegetation coverage turned out to be the two predominant contributors to the changes.There are four periods for the variation of the sensitive components of the sediment cores from 1940 to 2010,i.e.,1940–1950,1951–1980,1981–1990 and 1991–2010.The vertical distribution of grain size in the cores mainly varied with the changes of vegetation coverage in the catchment and reservoir construction from 1960 to 1980,whereas it varied depending on the intensity of water and soil erosion in the catchment from 1980 to 1990.Despite the further reduction of the water and sediment input into the sea from 1990 to 2009,this period was characterized by coarsening trends for the grain size of sediment in the estuarine intertidal flat and correspondingly,the significantly increased silt contents of the sensitive component.展开更多
A wave flume simulator was used to study internal nitrogen release from the surface sediment collected from Taihu Lake, China. Particulate nitrogen concentrations were positively correlated with the concentrations of ...A wave flume simulator was used to study internal nitrogen release from the surface sediment collected from Taihu Lake, China. Particulate nitrogen concentrations were positively correlated with the concentrations of suspended solids, primarily from surface erosion related to the shear stress and duration of wave action. In response to 4 cm- and 10 cm-high wave production representing waves generated in Taihu Lake by gentle and gusty winds, respectively, the mean dynamic release rate of ammonium （NH4＋） from the sediment to the overlying water was 1 × 10-3 mg/（m2.s） and the NH4＋ concentration in the overlying water increased by 0.016 mg/L, indicating that waves resulting from strong wind can induce the rapid release of dissolved nitrogen from Taihu Lake sediments. The decrease in interstitial NH4＋ concentrations at all sediment depths was associated with an increase in NH4＋ concentrations in the overlying water by 0.01 mg/L, showing that sediment below the eroded layer was the main source of internal nitrogen release. Changes in the interstitial dissolved oxygen and NH4＋ concentrations showed that wave-induced pore water movement can greatly increase the diffusion rate, and that these 15 cm. Diffusion induced by pore water movement sediment layer in Taihu Lake. effects can influence the sediment to a depth of at least may be very important for the formation of an active展开更多
A metagenomic library recombinant clone CAPL3, an Escherichia coli strain generated by transformed with metagenomic library from deep-sea sediments, can efficiently produce cold active lipase. The effects of both temp...A metagenomic library recombinant clone CAPL3, an Escherichia coli strain generated by transformed with metagenomic library from deep-sea sediments, can efficiently produce cold active lipase. The effects of both temperature and dissolved oxygen（DO） on cold active lipase production by batch culture of metagenomic library recombinant clone（CAPL3） from deep-sea sediment were investigated. First, a two-stage temperature control strategy was developed, in which the temperature was kept at 34 ℃ for the first 15 h, and then switched to30 ℃. The cold active lipase activity and productivity reached 315.2 U·ml^-1and 8.08 U·ml^-1·h^-1, respectively,increased by both 14.5% compared to the results obtained with temperature controlled at 30℃. In addition, different DO control modes were conducted, based on the data obtained from the different DO control strategies and analysis of kinetics parameters at different DO levels. A step-wise temperature and DO control strategy were developed to improve lipase production, i.e., temperature and DO level were controlled at 34℃, 30% during 0–15 h;30 ℃, 30% during 15–18 h, and 30 ℃, 20% during 18–39 h. With this strategy, the maximum lipase activity reached 354.6 U·ml^-1at 39 h, which was 28.8% higher than that achieved without temperature and DO control（275.3 U·ml^-1）.展开更多
Delta evolution in the context of no sediment discharge has become a global concern,and an accretion-to-erosion conversion is occurring in the Yangtze estuary.This conversion could threaten Changjiang subaqueous delta...Delta evolution in the context of no sediment discharge has become a global concern,and an accretion-to-erosion conversion is occurring in the Yangtze estuary.This conversion could threaten Changjiang subaqueous delta devel-opment.Sediment erodibility is an important indicator of subaqueous delta vulnerability.However,the present and future erodibility of the Changjiang subaqueous delta remains unclear.In this study,37 short cores were collected from the Changjiang subaqueous delta,and the critical shear stress of the sediment was measured using a cohesive strength meter(CSM)and compared with estimates based on an empirical Shields diagram.The sediment erodibility was analyzed by comparing the sediment critical shear stress with the bed shear stress simulated using a numerical model(i.e.,FVCOM),and sediment activity was introduced to discuss the geomorphological change in the subaque-ous delta.The CSM-derived critical shear stress is significantly higher than that derived from the empirical Shields formula,but it better shows the erodibility of the sediment.The annual surface sediment activity ranges from 5%to 30%based on the CSM,indicating low surface erodibility.Moreover,the critical shear stress in this region increases as water depth increases,but the bed shear stress shows the opposite trend.Therefore,the erodibility of the Changjiang subaqueous delta is lower than that of the shallow area,indicating no accretion-erosion conversion or continued vertical erosion under sediment starvation in the coming decades.These findings can provide suggestions for erosion assessment and management in large river deltas under decreasing sediment discharge.展开更多
基金The Open Fund of Key Laboratory of Marine Mineral Resources,Ministry of Land and Resources under contract No.KLMMR-2015-B-03the China Ocean Mineral Resources Research and Development Association Project under contract Nos DY125-11-R-01 and DY125-11-R-05the National Basic Research Program(973 program)of China under contract No.2012CB417305
文摘Hydrothermal plumes released from the eruption of sea floor hydrothermal fluids contain large amounts of oreforming materials. They precipitate within certain distances from the hydrothermal vent. Six surficial sediment samples from the Southwest Indian Ridge（SWIR） were analyzed by a portable X-ray fluorescence（PXRF） analyzer on board to find a favorable method fast and efficient enough for sea floor sulfide sediment geochemical exploration. These sediments were sampled near, at a moderate distance from, or far away from hydrothermal vents. The results demonstrate that the PXRF is effective in determining the enrichment characteristics of the oreforming elements in the calcareous sediments from the mid-ocean ridge. Sediment samples（〉40 mesh） have high levels of elemental copper, zinc, iron, and manganese, and levels of these elements in sediments finer than 40 mesh are lower and relatively stable. This may be due to relatively high levels of basalt debris/glass in the coarse sediments, which are consistent with the results obtained by microscopic observation. The results also show clear zoning of elements copper, zinc, arsenic, iron, and manganese in the surficial sediments around the hydrothermal vent. Sediments near the vent show relatively high content of the ore-forming elements and either high ratios of copper to iron content and zinc to iron content or high ratios of copper to manganese content and zinc to manganese content. These findings show that the content of the ore-forming elements in the sediments around hydrothermal vents are mainly influenced by the distance of sediments to the vent, rather than grain size. In this way, the PXRF analysis of surface sediment geochemistry is found to satisfy the requirements of recognition geochemical anomaly in mid-ocean ridge sediments. Sediments with diameters finer than 40 mesh should be used as analytical samples in the geochemical exploration for hydrothermal vents on mid-oceanic ridges. The results concerning copper, zinc, arsenic, iron, and manganese and their ratio features can be used as indicators in sediment geochemical exploration of seafloor sulfides.
基金Funded by the National Natural Science Foundation of China(No.51578108)the Ministry of Water Resource of the People’s Republic of China(No.201501003)
文摘This work focuses on the production of a new composite material using Yellow River sediment and coal slime ash via alkali-activating method. XRD, FTIR and SEM/EDS were used to characterize the alkali-activated products and microstructure of the composite material. Compressive strength was tested to characterize the mechanical property of the composite material. It is found that the compressive strength of the Yellow River sediment-coal slime ash composites increases as the added Ca（OH）_2 content grows. The compressive strength increases fast in the early stage but slowly after 28 days. The strength of the composites can be significantly improved via the addition of small amount of Na OH and gypsum. The products（C-S-H, ettringite and CaCO_3）, especially C-S-H, make much contribution to the enhancement of strength. The highest strength of the composites can reach 14.4 MPa after 90 days curing with 5% Ca（OH）_2, 0.2% NaOH and 7.5% gypsum. The improved properties of the composites show great potential of utilizing Yellow River sediment for inexpensive construction materials.
基金supported by the National Natural Science Foundation of China(nos.41063006,41363007,and 41273099)the Science and Technology Fund of Guizhou Province(no.[2013]2296)
文摘Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria（SRB） on mercury（Hg） methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury（DMe Hg） in the overlying water of the control cores with bioactivity maintained（BAC） and cores with only sulfate-reducing bacteria inhibited（SRBI） and bacteria fully inhibited（BACI） were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations（r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively）. The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster（hgc AB）, besides SRB,causing Hg methylation in the sediment–water system.
基金The National Natural Science Foundation of China under contract Nos 41576043 and 40976051
文摘The response to the catchment changes of the sedimentary environment of the western intertidal flat of Yalu River Estuary was investigated by analyzing the vertical variations of the grain size of sediment cores,along with the hydrologic data and human activities in the catchment.The results demonstrated a stepwise decreasing trend for the variations of both the sediment load and water discharge into the sea,which could be divided into three stages as 1958–1970,1971–1990 and 1991–2009.Reservoir construction and the changes of catchment vegetation coverage turned out to be the two predominant contributors to the changes.There are four periods for the variation of the sensitive components of the sediment cores from 1940 to 2010,i.e.,1940–1950,1951–1980,1981–1990 and 1991–2010.The vertical distribution of grain size in the cores mainly varied with the changes of vegetation coverage in the catchment and reservoir construction from 1960 to 1980,whereas it varied depending on the intensity of water and soil erosion in the catchment from 1980 to 1990.Despite the further reduction of the water and sediment input into the sea from 1990 to 2009,this period was characterized by coarsening trends for the grain size of sediment in the estuarine intertidal flat and correspondingly,the significantly increased silt contents of the sensitive component.
基金Supported by the National Natural Science Foundation of China(Nos.41101458, 40825004,40871095,40801200)the Major Project for National Science and Technology Development(No.2010ZX03006-006)the "100-Talent Project" of Chinese Academy of Sciences,China(No.YOBROB045)
文摘A wave flume simulator was used to study internal nitrogen release from the surface sediment collected from Taihu Lake, China. Particulate nitrogen concentrations were positively correlated with the concentrations of suspended solids, primarily from surface erosion related to the shear stress and duration of wave action. In response to 4 cm- and 10 cm-high wave production representing waves generated in Taihu Lake by gentle and gusty winds, respectively, the mean dynamic release rate of ammonium （NH4＋） from the sediment to the overlying water was 1 × 10-3 mg/（m2.s） and the NH4＋ concentration in the overlying water increased by 0.016 mg/L, indicating that waves resulting from strong wind can induce the rapid release of dissolved nitrogen from Taihu Lake sediments. The decrease in interstitial NH4＋ concentrations at all sediment depths was associated with an increase in NH4＋ concentrations in the overlying water by 0.01 mg/L, showing that sediment below the eroded layer was the main source of internal nitrogen release. Changes in the interstitial dissolved oxygen and NH4＋ concentrations showed that wave-induced pore water movement can greatly increase the diffusion rate, and that these 15 cm. Diffusion induced by pore water movement sediment layer in Taihu Lake. effects can influence the sediment to a depth of at least may be very important for the formation of an active
基金Supported by the Hi-Tech Research and Development Program of China(863 program of China2012AA092103)China Ocean Mineral Resources R&D Association(DY125-15-T-06)
文摘A metagenomic library recombinant clone CAPL3, an Escherichia coli strain generated by transformed with metagenomic library from deep-sea sediments, can efficiently produce cold active lipase. The effects of both temperature and dissolved oxygen（DO） on cold active lipase production by batch culture of metagenomic library recombinant clone（CAPL3） from deep-sea sediment were investigated. First, a two-stage temperature control strategy was developed, in which the temperature was kept at 34 ℃ for the first 15 h, and then switched to30 ℃. The cold active lipase activity and productivity reached 315.2 U·ml^-1and 8.08 U·ml^-1·h^-1, respectively,increased by both 14.5% compared to the results obtained with temperature controlled at 30℃. In addition, different DO control modes were conducted, based on the data obtained from the different DO control strategies and analysis of kinetics parameters at different DO levels. A step-wise temperature and DO control strategy were developed to improve lipase production, i.e., temperature and DO level were controlled at 34℃, 30% during 0–15 h;30 ℃, 30% during 15–18 h, and 30 ℃, 20% during 18–39 h. With this strategy, the maximum lipase activity reached 354.6 U·ml^-1at 39 h, which was 28.8% higher than that achieved without temperature and DO control（275.3 U·ml^-1）.
基金the Natural Science Foundation of China(No.41876092 and 42006151)the Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-05-E00027)the Open Research Fund of Key Laboratory of Coastal Salt Marsh Ecosystems and Resources,Ministry of Natural Resources(No.KLCSMERMNR2021001).
文摘Delta evolution in the context of no sediment discharge has become a global concern,and an accretion-to-erosion conversion is occurring in the Yangtze estuary.This conversion could threaten Changjiang subaqueous delta devel-opment.Sediment erodibility is an important indicator of subaqueous delta vulnerability.However,the present and future erodibility of the Changjiang subaqueous delta remains unclear.In this study,37 short cores were collected from the Changjiang subaqueous delta,and the critical shear stress of the sediment was measured using a cohesive strength meter(CSM)and compared with estimates based on an empirical Shields diagram.The sediment erodibility was analyzed by comparing the sediment critical shear stress with the bed shear stress simulated using a numerical model(i.e.,FVCOM),and sediment activity was introduced to discuss the geomorphological change in the subaque-ous delta.The CSM-derived critical shear stress is significantly higher than that derived from the empirical Shields formula,but it better shows the erodibility of the sediment.The annual surface sediment activity ranges from 5%to 30%based on the CSM,indicating low surface erodibility.Moreover,the critical shear stress in this region increases as water depth increases,but the bed shear stress shows the opposite trend.Therefore,the erodibility of the Changjiang subaqueous delta is lower than that of the shallow area,indicating no accretion-erosion conversion or continued vertical erosion under sediment starvation in the coming decades.These findings can provide suggestions for erosion assessment and management in large river deltas under decreasing sediment discharge.
