The water quality of Dianchi Lake declines quickly and the eutrophication is getting serious. To identify the internal pollution load of Dianchi Lake it is necessary to evaluate its sediment accumulation. Sedimentatio...The water quality of Dianchi Lake declines quickly and the eutrophication is getting serious. To identify the internal pollution load of Dianchi Lake it is necessary to evaluate its sediment accumulation. Sedimentation rates of Dianchi Lake are determined by ^137Cs dating. However, ^137Cs vertical distribution in sediment cores of Dianchi Lake has special characteristics because Dianchi Lake is located on the southeast of the Qinghai-Tibet Plateau, the Kunming quasi-stationary front is over the borders of Yunnan and Guizhou where the specific precipitation is distributed. Besides 1954, 1963 and 1986 ^137Cs marks can be determined in sediment cores, a ^137Cs mark of 1976 representing the major period of ^137Cs released from China unclear test can be determined and used for an auxiliary dating mark. Meanwhile Dianchi Lake is divided into seven sections based on the water depth, basin topography, hydrological features and supplies of silt and the lakebed area of each section is calculated. The mean annual sedimentation rates for seven sections are 0.0810, 0.1352, 0.1457, 0.1333, 0.0904, 0.1267 and 0.1023 g/cm^2 a in 1963-2003, respectively. The gross sediment accumulation of the lake is 26.18×10^4 t/a in recent 17 years and 39.86×10^4t/a in recent 50 years.展开更多
This research deals with the characterization of areas associated with flash floods and erosion caused by severe rainfall storm and sediment transport and accumulation using topographic attributes and profiles, spectr...This research deals with the characterization of areas associated with flash floods and erosion caused by severe rainfall storm and sediment transport and accumulation using topographic attributes and profiles, spectral indices (SI), and principal component analysis (PCA). To achieve our objectives, topographic attributes and profiles were retrieved from ASTER-V2 DEM. PCA and nine SI were derived from two Landsat-OLI images acquired before and after the flood-storm. The images data were atmospherically corrected, sensor radiometric drift calibrated, and geometric and topographic distortions rectified. For validation purposes, the acquired photos during the flood-storm, lithological and geological maps were used. The analysis of approximately 100 colour composite combinations in the RGB system permitted the selection of two combinations due to their potential for characterizing soil erosion classes and sediment accumulation. The first considers the “Intensity, NDWI and NMDI”, while the second associates form index (FI), brightness index (BI) and NDWI. These two combinations provide very good separating power between different levels of soil erosion and degradation. Moreover, the derived erosion risk and sediment accumulation map based on the selected spectral indices segmentation and topographic attributes and profiles illustrated the tendency of water accumulation in the landscape, and highlighted areas prone to both fast moving and pooling water. In addition, it demonstrated that the rainfall, the topographic morphology and the lithology are the major contributing factors for flash flooding, catastrophic inundation, and erosion risk in the study area. The runoff-water power delivers vulnerable topsoil and contributes strongly to the erosion process, and then transports soil material and sediment to the plain areas through waterpower and gravity. The originality of this research resides in its simplicity and rapidity to provide a solid basis strategy for regional policies to address the real causes of problems and risks in developing countries. Certainly, it can help in the improvement of the management of water regulation structures to develop a methodology to maximize the water storage capacity and to reduce the risks caused by floods in the Moroccan Atlas Mountain (Guelmim region).展开更多
Manadas Creek is an urban tributary of the Rio Grande that flows past a decommissioned antimony smelter and processing plant. This antimony plant is associated with heavy metal contamination in the creek and still pos...Manadas Creek is an urban tributary of the Rio Grande that flows past a decommissioned antimony smelter and processing plant. This antimony plant is associated with heavy metal contamination in the creek and still poses a threat to the surrounding aquatic environment. Corbicula fluminea was used to determine bioaccumulation from the water column and sediments in Manadas Creek. The metals arsenic (As), antimony (Sb) and thallium (Tl) were analyzed in the water, sediments, gills, mantle, foot, digestive (DI) tract, gonads and shell of clams being monitored at eight sites between March and August 2013. Sediment, water, and dissected Corbicula fluminea samples from different sites in the Creek were acid-digested and analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy. High levels of antimony (25.88 ug/L;75.96 mg/kg) and arsenic (8.26 ug/L;6.41 mg/kg) in the water and sediments were observed at the site downstream from the smelter. There were no detectable concentrations of arsenic, antimony, or thallium in the shell of C. fluminea. Arsenic and antimony were detected in the tissues of C. fluminea but thallium was not detected. Based on the results, the organotropism for arsenic is DI tract > gills > gonads > foot > mantle > shell and the organotropism for antimony is gills > DI tract > gonads > mantle > foot > shell. This study shows that the Asiatic clam (Corbicula fluminea) is a useful bio-monitor to provide data on the status of metal pollution in Manadas Creek, Laredo, Texas.展开更多
The GPS data sourced from the permanent GPS network in the Kashmir Himalaya were utilized to quantify both vertical and horizontal deformation rates in the Kashmir Valley of the northwestern Himalaya.While lateral def...The GPS data sourced from the permanent GPS network in the Kashmir Himalaya were utilized to quantify both vertical and horizontal deformation rates in the Kashmir Valley of the northwestern Himalaya.While lateral deformation in the Kashmir basin has been previously quantified,the vertical component has not been studied yet.To quantify the vertical and horizontal deformation rates in the Kashmir Valley,we use GAMIT/GLOBK software to process the GPS data.The lateral motion data indicate that the Indian plate continues to move towards the Eurasian plate at a rate of 36-42 mm/yr,while the vertical vectors infer a transition zone across the Kashmir valley.Using ArcGIS,Iso-base and Iso-ketabase maps were generated from the GPS vertical vectors to study the vertical deformation status of the Kashmir Valley.The analysis of vertical vectors reveals a significant transition zone in the Kashmir Valley.The vertical vector data show distinct patterns:GPS stations in the northeast,south,and southeast of the Kashmir Valley exhibit uplift,while stations in the north,northwest,and southwest show subsidence.The uplift velocity increases as we move from the Srinagar station to the Kulgam station via Tral and Ashmuqam,while the subsidence rate increases as we move from the Bandipora station to Mulgam and Uri.Specifically,the highest uplift rate(5.2±0.6 mm/yr)is observed at the Kulgam station and the highest subsidence rate(-6.5±1.26 mm/yr)at the Uri station.On average,vertical subsidence of-2.81 mm/yr is recorded along the north and northwest sides of the valley,and an average uplift of 3.04 mm/yr in the south and southeast.Integrating geomorphological observations with GPS measurements,we infer the presence of an active normal fault running northeast-southwest across the Kashmir Valley,transverse to the major thrust faults.Recent seismic events,including the M_(W)3.9 event near Nagbal and the M_(W)3.7 event near Mujgund in 2020,clustering of local seismic events,and two devastating historical seismic events(1828 AD and 1877/1878 AD)along this transition zone highlight the fault's activity and the region's vulnerability to future earthquakes.Delineation of such geological structures is crucial for seismic hazard assessment and micro-seismic zonation in the Kashmir Valley.Therefore,this study represents a significant step towards understanding the geodynamics and kinematics of the region and improving seismic risk mitigation strategies.展开更多
Land clearing,river impoundments,and other human modifications to the upland landscape and within estuarine systems can drive coastal change at local to regional scales.However,as compared with mid-latitude coasts,the...Land clearing,river impoundments,and other human modifications to the upland landscape and within estuarine systems can drive coastal change at local to regional scales.However,as compared with mid-latitude coasts,the impacts of human modifications along sediment-starved formerly glaciated coastal landscapes are relatively understudied.To address this gap,we present a late-Holocene record of changing sediment accumulation rates and sediment sources from sediment cores collected across a tidal flat in the Merrimack River estuary(Mass.,USA).We pair sedimentology,geochronology,bulk-and stable-isotope organic geochemistry,and hydrodynamic simulations with historical data to evaluate human and natural impacts on coastal sediment fluxes.During the 17th to 19th centuries,accumulation rates increased by an order of magnitude in the central tidal flat,likely in response to enhanced delivery of terrestrial sediment resulting from upland deforestation.However,the overall increase in accumulation(0.56–2.6 mm/year)within the estuary is subtle and spatially variable across the tidal flats because of coincident anthropogenic land clearing and dam building,upland sediment storage,and estuarine hydrodynamics.This study provides insight into the response of formerly glaciated fluvialcoastal systems to human modifications,and underscores the role of estuarine environmental conditions in modifying upland signals of land-use change.展开更多
基金National Natural Science Foundation of China, No.40771186The Key Project of the State Key Laboratory of Soil Sustainable Agriculture,Nanjing Institute of Soil Sciences,Chinese Academy of Sciences,No.5022505
文摘The water quality of Dianchi Lake declines quickly and the eutrophication is getting serious. To identify the internal pollution load of Dianchi Lake it is necessary to evaluate its sediment accumulation. Sedimentation rates of Dianchi Lake are determined by ^137Cs dating. However, ^137Cs vertical distribution in sediment cores of Dianchi Lake has special characteristics because Dianchi Lake is located on the southeast of the Qinghai-Tibet Plateau, the Kunming quasi-stationary front is over the borders of Yunnan and Guizhou where the specific precipitation is distributed. Besides 1954, 1963 and 1986 ^137Cs marks can be determined in sediment cores, a ^137Cs mark of 1976 representing the major period of ^137Cs released from China unclear test can be determined and used for an auxiliary dating mark. Meanwhile Dianchi Lake is divided into seven sections based on the water depth, basin topography, hydrological features and supplies of silt and the lakebed area of each section is calculated. The mean annual sedimentation rates for seven sections are 0.0810, 0.1352, 0.1457, 0.1333, 0.0904, 0.1267 and 0.1023 g/cm^2 a in 1963-2003, respectively. The gross sediment accumulation of the lake is 26.18×10^4 t/a in recent 17 years and 39.86×10^4t/a in recent 50 years.
文摘This research deals with the characterization of areas associated with flash floods and erosion caused by severe rainfall storm and sediment transport and accumulation using topographic attributes and profiles, spectral indices (SI), and principal component analysis (PCA). To achieve our objectives, topographic attributes and profiles were retrieved from ASTER-V2 DEM. PCA and nine SI were derived from two Landsat-OLI images acquired before and after the flood-storm. The images data were atmospherically corrected, sensor radiometric drift calibrated, and geometric and topographic distortions rectified. For validation purposes, the acquired photos during the flood-storm, lithological and geological maps were used. The analysis of approximately 100 colour composite combinations in the RGB system permitted the selection of two combinations due to their potential for characterizing soil erosion classes and sediment accumulation. The first considers the “Intensity, NDWI and NMDI”, while the second associates form index (FI), brightness index (BI) and NDWI. These two combinations provide very good separating power between different levels of soil erosion and degradation. Moreover, the derived erosion risk and sediment accumulation map based on the selected spectral indices segmentation and topographic attributes and profiles illustrated the tendency of water accumulation in the landscape, and highlighted areas prone to both fast moving and pooling water. In addition, it demonstrated that the rainfall, the topographic morphology and the lithology are the major contributing factors for flash flooding, catastrophic inundation, and erosion risk in the study area. The runoff-water power delivers vulnerable topsoil and contributes strongly to the erosion process, and then transports soil material and sediment to the plain areas through waterpower and gravity. The originality of this research resides in its simplicity and rapidity to provide a solid basis strategy for regional policies to address the real causes of problems and risks in developing countries. Certainly, it can help in the improvement of the management of water regulation structures to develop a methodology to maximize the water storage capacity and to reduce the risks caused by floods in the Moroccan Atlas Mountain (Guelmim region).
文摘Manadas Creek is an urban tributary of the Rio Grande that flows past a decommissioned antimony smelter and processing plant. This antimony plant is associated with heavy metal contamination in the creek and still poses a threat to the surrounding aquatic environment. Corbicula fluminea was used to determine bioaccumulation from the water column and sediments in Manadas Creek. The metals arsenic (As), antimony (Sb) and thallium (Tl) were analyzed in the water, sediments, gills, mantle, foot, digestive (DI) tract, gonads and shell of clams being monitored at eight sites between March and August 2013. Sediment, water, and dissected Corbicula fluminea samples from different sites in the Creek were acid-digested and analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy. High levels of antimony (25.88 ug/L;75.96 mg/kg) and arsenic (8.26 ug/L;6.41 mg/kg) in the water and sediments were observed at the site downstream from the smelter. There were no detectable concentrations of arsenic, antimony, or thallium in the shell of C. fluminea. Arsenic and antimony were detected in the tissues of C. fluminea but thallium was not detected. Based on the results, the organotropism for arsenic is DI tract > gills > gonads > foot > mantle > shell and the organotropism for antimony is gills > DI tract > gonads > mantle > foot > shell. This study shows that the Asiatic clam (Corbicula fluminea) is a useful bio-monitor to provide data on the status of metal pollution in Manadas Creek, Laredo, Texas.
文摘The GPS data sourced from the permanent GPS network in the Kashmir Himalaya were utilized to quantify both vertical and horizontal deformation rates in the Kashmir Valley of the northwestern Himalaya.While lateral deformation in the Kashmir basin has been previously quantified,the vertical component has not been studied yet.To quantify the vertical and horizontal deformation rates in the Kashmir Valley,we use GAMIT/GLOBK software to process the GPS data.The lateral motion data indicate that the Indian plate continues to move towards the Eurasian plate at a rate of 36-42 mm/yr,while the vertical vectors infer a transition zone across the Kashmir valley.Using ArcGIS,Iso-base and Iso-ketabase maps were generated from the GPS vertical vectors to study the vertical deformation status of the Kashmir Valley.The analysis of vertical vectors reveals a significant transition zone in the Kashmir Valley.The vertical vector data show distinct patterns:GPS stations in the northeast,south,and southeast of the Kashmir Valley exhibit uplift,while stations in the north,northwest,and southwest show subsidence.The uplift velocity increases as we move from the Srinagar station to the Kulgam station via Tral and Ashmuqam,while the subsidence rate increases as we move from the Bandipora station to Mulgam and Uri.Specifically,the highest uplift rate(5.2±0.6 mm/yr)is observed at the Kulgam station and the highest subsidence rate(-6.5±1.26 mm/yr)at the Uri station.On average,vertical subsidence of-2.81 mm/yr is recorded along the north and northwest sides of the valley,and an average uplift of 3.04 mm/yr in the south and southeast.Integrating geomorphological observations with GPS measurements,we infer the presence of an active normal fault running northeast-southwest across the Kashmir Valley,transverse to the major thrust faults.Recent seismic events,including the M_(W)3.9 event near Nagbal and the M_(W)3.7 event near Mujgund in 2020,clustering of local seismic events,and two devastating historical seismic events(1828 AD and 1877/1878 AD)along this transition zone highlight the fault's activity and the region's vulnerability to future earthquakes.Delineation of such geological structures is crucial for seismic hazard assessment and micro-seismic zonation in the Kashmir Valley.Therefore,this study represents a significant step towards understanding the geodynamics and kinematics of the region and improving seismic risk mitigation strategies.
基金funded by the National Science Foundation Coastal SEES(award No.OCE 1325430)the Charles Center at William&Mary,and the Southeastern Section of the Geological Society of America+1 种基金The Virginia Institute of Marine Science(VIMS)National Science Foundation REU Program(award No.OCE 1062882)a VIMS Short Trust GK-12 Fellowship supported JLS.
文摘Land clearing,river impoundments,and other human modifications to the upland landscape and within estuarine systems can drive coastal change at local to regional scales.However,as compared with mid-latitude coasts,the impacts of human modifications along sediment-starved formerly glaciated coastal landscapes are relatively understudied.To address this gap,we present a late-Holocene record of changing sediment accumulation rates and sediment sources from sediment cores collected across a tidal flat in the Merrimack River estuary(Mass.,USA).We pair sedimentology,geochronology,bulk-and stable-isotope organic geochemistry,and hydrodynamic simulations with historical data to evaluate human and natural impacts on coastal sediment fluxes.During the 17th to 19th centuries,accumulation rates increased by an order of magnitude in the central tidal flat,likely in response to enhanced delivery of terrestrial sediment resulting from upland deforestation.However,the overall increase in accumulation(0.56–2.6 mm/year)within the estuary is subtle and spatially variable across the tidal flats because of coincident anthropogenic land clearing and dam building,upland sediment storage,and estuarine hydrodynamics.This study provides insight into the response of formerly glaciated fluvialcoastal systems to human modifications,and underscores the role of estuarine environmental conditions in modifying upland signals of land-use change.
