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Yipu Huang - One of the best experts on this subject based on the ideXlab platform.
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Thorium Isotopes 228th 230th 232th and applications in reconstructing the yangtze and yellow river floods
International Journal of Sediment Research, 2013Co-Authors: Weifeng Yang, Min Chen, Xinxing Zhang, Zhi-gang Guo, Junhong Yang, L I Guangxue, M A Qiang, Yipu HuangAbstract:In the past decades, the floods of the Yangtze and Yellow River introduced unexpected changes of the ecological community and sedimentary dynamics in the East China Sea (ECS). To reconstruct the flood events in the ECS, 228Th, 230Th and 232Th have been examined in a sediment core. The specific activities of three Thorium Isotopes have good positive relations with fine fractions (<63 μm), indicating that Th activity concentrations heavily depend upon the sediment grain size. The size-normalized activities of 228Th, 230Th and 232Th showed significant variations. Coincidences between the higher Th activities and historical floods of the Yangtze and Yellow River demonstrated that size-normalized Th recorded the two rivers' flood events. The activity ratios of Thorium Isotopes, i.e. 230Th/232Th and 228Th/232Th, also showed similar patterns to the historical river floods. In three periods (1740s, 1840–1860s and 1930–1960s), characterized by frequent floods, the Thorium activity ratios were fairly low and close to the Yangtze and Yellow River estuary sediments, coinciding with the less oceanic 228Th and 230Th contributions during the flooding periods. Accordingly, these results support the size-normalized Th activity and Thorium ratios as proxies of the river floods in coastal seas.
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Thorium Isotopes (228Th, 230Th, 232Th) and applications in reconstructing the Yangtze and Yellow River floods
International Journal of Sediment Research, 2013Co-Authors: Weifeng Yang, Min Chen, Xinxing Zhang, Zhi-gang Guo, Junhong Yang, Yipu HuangAbstract:In the past decades, the floods of the Yangtze and Yellow River introduced unexpected changes of the ecological community and sedimentary dynamics in the East China Sea (ECS). To reconstruct the flood events in the ECS, 228Th, 230Th and 232Th have been examined in a sediment core. The specific activities of three Thorium Isotopes have good positive relations with fine fractions (
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Size-fractionated Thorium Isotopes (228Th, 230Th, 232Th) in surface waters in the Jiulong River estuary, China.
Journal of Environmental Radioactivity, 2005Co-Authors: Lei Zhang, Weifeng Yang, Min Chen, Na Xing, Yusheng Qiu, Yipu HuangAbstract:Abstract Thorium Isotopes ( 228 Th, 230 Th, 232 Th and 234 Th) are useful tracers for studying particle dynamics and trace element scavenging in marine environments. In this study, surface waters were collected along a salinity gradient from the Jiulong River estuary, China, for determination of activity concentrations of 228 Th, 230 Th and 232 Th in different size fractions, namely, the >53 μm, 10–53 μm, 2–10 μm, 0.4–2 μm, 10 kDa–0.4 μm and the 228 Th, 230 Th and 232 Th in the Jiulong River estuarine waters were significantly higher than most of the previously reported values in coastal and oceanic seawaters, suggesting a higher lithogenic U and Th contribution from the Jiulong River Basin. When normalized to the particulate mass concentration, the activity concentrations of the three Thorium Isotopes decreased with increasing particle size, demonstrating the important role of surface areas of particles in controlling the scavenging of Thorium from the water column. The partitioning of three Thorium Isotopes showed a common characteristic, i.e., the >53 μm fraction had the least share (0–1%), while the 10–53 μm fraction had the largest share of Th Isotopes. The average value of the 230 Th/ 232 Th activity ratio ( 230 Th/ 232 Th) A.R. increased from 0.8 in the >53 μm fraction to 3.7 in the 10 kDa–0.4 μm fraction, indicating that the radiogenic Th Isotopes are preferentially scavenged by the small size particles. ( 230 Th/ 232 Th) A.R. in the 228 Th had the highest concentration in the mid-salinity region, showing a non-conservative behavior with additional input. In contrast, dissolved 232 Th showed a concave profile, indicating a net removal of 232 Th during the mixing of fresh water with seawater. The behavior of Th Isotopes in the
Mikael Hult - One of the best experts on this subject based on the ideXlab platform.
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Timescales of hydrothermal scavenging in the South Pacific Ocean from 234 Th, 230 Th, and 228 Th
Earth and Planetary Science Letters, 2019Co-Authors: Frank Pavia, Robert Anderson, Erin Black, Lauren Kipp, Sebastian Vivancos, Martin Fleisher, Matthew Charette, Virginie Sanial, Willard Moore, Mikael HultAbstract:Hydrothermal activity in the deep ocean generates plumes of metal-rich particles capable of removing certain trace elements from seawater by adsorption and sedimentation. This removal process, known as scavenging, can be probed using the insoluble radiogenic Isotopes of Thorium (Th), which are produced at a known rate in the water column via the decay of soluble uranium (234 Th, 230 Th) and radium (228 Th) Isotopes. We present dissolved and particulate measurements of these three Thorium Isotopes in a hydrothermal plume observed in the southeast Pacific Ocean on the GEOTRACES GP16 section. Since their half-lives vary from days (234 Th) to years (228 Th) to tens of thousands of years (230 Th), the combination of their signals can be used to understand scavenging processes occurring on a wide range of timescales. Scavenging is a multi-step process involving adsorption and desorption onto particles, followed by particle aggregation, sinking, and eventual sedimentation. We use Thorium Isotopes to study how hydrothermal activity affects these steps. The rate constants for net adsorption of 234 Th determined here are comparable to previous estimates from hydrothermal plumes in the Atlantic and North Pacific Oceans. The partitioning of 234 Th and 230 Th between large and small particles is more similar in the hydrothermal plume than above it, indicating faster aggregation of particles within the hydrothermal plume at stations nearby the East Pacific Rise than in waters outside the plume. In addition to rapid scavenging and aggregation near the ridge axis, we also infer continuous off-axis scavenging from observations and modeling of 228 Th/ 228 Ra activity ratios. The degree of depletion of the three Thorium Isotopes increases in order of half-life, with total 234 Th activity close to that of its parent 238 U, but 230 Th showing nearly 70% depletion compared to expected values from reversible scavenging. By modeling the variations in depletion for the different Isotopes, we show that much of the 230 Th removal is inherited from scavenging events happening long before the most recent hydrothermal inputs.
Francois Fernex - One of the best experts on this subject based on the ideXlab platform.
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uranium and Thorium Isotopes in the rivers of the amazonian basin hydrology and weathering processes
Hydrological Processes, 2003Co-Authors: A N Marques, Michel Bernat, Iyad Algharib, Francois FernexAbstract:Two expeditions (October 1989 and May 1992) were carried out to two points of the main Amazon River channel and four tributaries. The Solimoes and Madeira rivers, taking their origin in the Andes, are whitewater rivers. The Negro River is a typical acid, blackwater river. The Trombetas River flows through bauxite-rich areas, and is characterized by low concentrations of dissolved humic substances. The 238U, 234U, 232Th and 230Th activities were recorded from dissolved, suspended particulate phases and river bank sediments. The latter were analysed for their 226Ra, 228Ra and 210Pb contents, and also subjected to leaching with 0·2 M hydroxylamine–hydrochloride solution to determine the concentrations of radionuclides bound to amorphous Fe hydroxides and Mn oxides and hydroxides. The dissolved U average concentration in the Amazon system is ten times lower than the mean world river concentration. The uranium concentration observed at Obidos in the lower Amazon (0·095 µg L−1), where the U content in the river bank sediments and suspended matter is lowest, suggests U release from the solid phase during river transport. About 485 t of U are transported annually to the Amazon delta area in dissolved form, and 1943 t bound to suspended particulate matter. Total U and Th concentrations in the river bank sediments ranged from 1·59 to 7·14 µg g−1 and from 6·74 to 32 µg g−1, respectively. The highest concentrations were observed in the Trombetas River. The proportion extracted by means of the hydroxylamine solution (HL) was relatively high for U in the Trombetas river bank sediment (31%) and for Th in the Solimoes sediment (30%). According to the alpha recoil effects, the 234U/238U activity ratios of the Andean river waters and downstream Amazon water (Obidos) were >1, but were 1 in the Trombetas and Negro rivers. Such ratios probably result from the binding of dissolved uranium to solid sediment. The 228Th/232Th ratios of river bank sediments were close to unity (except for the Negro River, where it is lower), suggesting no significant Th exchanges between the river water and the sediment. The 226Ra/232Th activity ratios were <1, and the 226Ra/228Ra activity ratios generally were significantly higher than the activity ratios of their respective parents. This perhaps is the result of easier leaching of the 226Ra parent, 230Th, from solid material (owing to the alpha recoil effect) than of the 228Ra parent. Uranium and Thorium Isotopes were used as tools to evaluate the chemical weathering rate of rocks in the Amazon system, which was estimated to be 2·7 cm 1000 year−1 s−1. Copyright © 2002 John Wiley & Sons, Ltd.
Frank Pavia - One of the best experts on this subject based on the ideXlab platform.
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Timescales of hydrothermal scavenging in the South Pacific Ocean from 234 Th, 230 Th, and 228 Th
Earth and Planetary Science Letters, 2019Co-Authors: Frank Pavia, Robert Anderson, Erin Black, Lauren Kipp, Sebastian Vivancos, Martin Fleisher, Matthew Charette, Virginie Sanial, Willard Moore, Mikael HultAbstract:Hydrothermal activity in the deep ocean generates plumes of metal-rich particles capable of removing certain trace elements from seawater by adsorption and sedimentation. This removal process, known as scavenging, can be probed using the insoluble radiogenic Isotopes of Thorium (Th), which are produced at a known rate in the water column via the decay of soluble uranium (234 Th, 230 Th) and radium (228 Th) Isotopes. We present dissolved and particulate measurements of these three Thorium Isotopes in a hydrothermal plume observed in the southeast Pacific Ocean on the GEOTRACES GP16 section. Since their half-lives vary from days (234 Th) to years (228 Th) to tens of thousands of years (230 Th), the combination of their signals can be used to understand scavenging processes occurring on a wide range of timescales. Scavenging is a multi-step process involving adsorption and desorption onto particles, followed by particle aggregation, sinking, and eventual sedimentation. We use Thorium Isotopes to study how hydrothermal activity affects these steps. The rate constants for net adsorption of 234 Th determined here are comparable to previous estimates from hydrothermal plumes in the Atlantic and North Pacific Oceans. The partitioning of 234 Th and 230 Th between large and small particles is more similar in the hydrothermal plume than above it, indicating faster aggregation of particles within the hydrothermal plume at stations nearby the East Pacific Rise than in waters outside the plume. In addition to rapid scavenging and aggregation near the ridge axis, we also infer continuous off-axis scavenging from observations and modeling of 228 Th/ 228 Ra activity ratios. The degree of depletion of the three Thorium Isotopes increases in order of half-life, with total 234 Th activity close to that of its parent 238 U, but 230 Th showing nearly 70% depletion compared to expected values from reversible scavenging. By modeling the variations in depletion for the different Isotopes, we show that much of the 230 Th removal is inherited from scavenging events happening long before the most recent hydrothermal inputs.
Weifeng Yang - One of the best experts on this subject based on the ideXlab platform.
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Thorium Isotopes 228th 230th 232th and applications in reconstructing the yangtze and yellow river floods
International Journal of Sediment Research, 2013Co-Authors: Weifeng Yang, Min Chen, Xinxing Zhang, Zhi-gang Guo, Junhong Yang, L I Guangxue, M A Qiang, Yipu HuangAbstract:In the past decades, the floods of the Yangtze and Yellow River introduced unexpected changes of the ecological community and sedimentary dynamics in the East China Sea (ECS). To reconstruct the flood events in the ECS, 228Th, 230Th and 232Th have been examined in a sediment core. The specific activities of three Thorium Isotopes have good positive relations with fine fractions (<63 μm), indicating that Th activity concentrations heavily depend upon the sediment grain size. The size-normalized activities of 228Th, 230Th and 232Th showed significant variations. Coincidences between the higher Th activities and historical floods of the Yangtze and Yellow River demonstrated that size-normalized Th recorded the two rivers' flood events. The activity ratios of Thorium Isotopes, i.e. 230Th/232Th and 228Th/232Th, also showed similar patterns to the historical river floods. In three periods (1740s, 1840–1860s and 1930–1960s), characterized by frequent floods, the Thorium activity ratios were fairly low and close to the Yangtze and Yellow River estuary sediments, coinciding with the less oceanic 228Th and 230Th contributions during the flooding periods. Accordingly, these results support the size-normalized Th activity and Thorium ratios as proxies of the river floods in coastal seas.
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Thorium Isotopes (228Th, 230Th, 232Th) and applications in reconstructing the Yangtze and Yellow River floods
International Journal of Sediment Research, 2013Co-Authors: Weifeng Yang, Min Chen, Xinxing Zhang, Zhi-gang Guo, Junhong Yang, Yipu HuangAbstract:In the past decades, the floods of the Yangtze and Yellow River introduced unexpected changes of the ecological community and sedimentary dynamics in the East China Sea (ECS). To reconstruct the flood events in the ECS, 228Th, 230Th and 232Th have been examined in a sediment core. The specific activities of three Thorium Isotopes have good positive relations with fine fractions (
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Size-fractionated Thorium Isotopes (228Th, 230Th, 232Th) in surface waters in the Jiulong River estuary, China.
Journal of Environmental Radioactivity, 2005Co-Authors: Lei Zhang, Weifeng Yang, Min Chen, Na Xing, Yusheng Qiu, Yipu HuangAbstract:Abstract Thorium Isotopes ( 228 Th, 230 Th, 232 Th and 234 Th) are useful tracers for studying particle dynamics and trace element scavenging in marine environments. In this study, surface waters were collected along a salinity gradient from the Jiulong River estuary, China, for determination of activity concentrations of 228 Th, 230 Th and 232 Th in different size fractions, namely, the >53 μm, 10–53 μm, 2–10 μm, 0.4–2 μm, 10 kDa–0.4 μm and the 228 Th, 230 Th and 232 Th in the Jiulong River estuarine waters were significantly higher than most of the previously reported values in coastal and oceanic seawaters, suggesting a higher lithogenic U and Th contribution from the Jiulong River Basin. When normalized to the particulate mass concentration, the activity concentrations of the three Thorium Isotopes decreased with increasing particle size, demonstrating the important role of surface areas of particles in controlling the scavenging of Thorium from the water column. The partitioning of three Thorium Isotopes showed a common characteristic, i.e., the >53 μm fraction had the least share (0–1%), while the 10–53 μm fraction had the largest share of Th Isotopes. The average value of the 230 Th/ 232 Th activity ratio ( 230 Th/ 232 Th) A.R. increased from 0.8 in the >53 μm fraction to 3.7 in the 10 kDa–0.4 μm fraction, indicating that the radiogenic Th Isotopes are preferentially scavenged by the small size particles. ( 230 Th/ 232 Th) A.R. in the 228 Th had the highest concentration in the mid-salinity region, showing a non-conservative behavior with additional input. In contrast, dissolved 232 Th showed a concave profile, indicating a net removal of 232 Th during the mixing of fresh water with seawater. The behavior of Th Isotopes in the