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An in-situ analysis and measurement of thorium-234,uranium isotopes in seawater

Acta Oceanologica Sinica 2007年第3期26卷 73-83页

作者： ZENG Xianzhang QIU Manhua YINMingduan ZENG Wenyi HE Jianhua WAN Xueguo CHEN Hengliang LI Jing TAN Baozeng Key laboratory of Global Change and Marine - Atmospheric Chemistry of State Oceanic Administration Third Institute of Ocea-nography State Oceanic Administration Xiamen 361005 China Third Institute of Oceanography State Oceanic Administration Xiamen 361005 China China National Nuclear Corporation Beijing Nuclear Instrument Factory Beijing 100020 China

A low-level β counting-or spectrum apparatus used for the detection of the β radiation of thorium-234 and α spectrum of thorium- 228 simultaneously and an easy operating procedure for the enrichment, radiochemical separating, sampling and measurement of thorium-234 and uranium-238 in the ocean are developed based on the requirements of analyzing export productivity in the eupho- ric zone via thorium-234 - uranium-238 radioactivity disequilibrium. The detecting efficiency both of 13 and α radiation is higher than 20%. The background of βradiation is less than 0. 5 min ^-1 , and the energy resolution of ct detector is better than 1%. Total recycle ratio of thorium-234 is about 75%. Using the above apparatus and procedure, the radioactivities of dissolved thorium-234 and uranium-238, particle thorium-234 and uranium-238 in seawater of the South China Sea, the Southern Ocean and the Arctic Ocean were analyzed.

关键词： ocean β counting-or spectrum apparatus radiochemical separating thorium-234 uranium-238

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Utilizing ^(234)Th/^(238)U disequilibrium to constrain particle dynamics in hydrothermal plumes in the Southwest Indian Ocean

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Acta Oceanologica Sinica 2021年第6期40卷 16-25页

作者： Weifeng Yang Xinxing Zhang Min Chen Ziming Fang Yusheng Qiu State Key Laboratory of Marine Environmental Science Xiamen UniversityXiamen 361102China College of Ocean and Earth Sciences Xiamen UniversityXiamen 361102China North China Sea Environmental Monitoring Center State Oceanic AdministrationQingdao 266033China Department of Ocean Science Hong Kong University of Science and TechnologyHong Kong 999077China

Metal-enriched minerals have been widely observed near hydrothermal vent ***,the dynamics of particulate metals influenced by hydrothermal activities is poorly ***,radioactive 234Th in both dissolved and particulate phases were used to examine the kinetics of particle-reactive metal adsorption,removal,and residence in a newly found hydrothermal plume over the Southwest Indian *** results showed a relatively low value on ^(234)Th/^(238)U ratios(i.e.,0.73-0.88)compared to the deep oceans,indicating an enhanced adsorption of particle-reactive metals onto particulate matter in the *** on the 234Th-238U disequilibria,the adsorption and sinking rate constants of 234Th averaged(0.009±0.001)d^(-1) and(0.113±0.024)d^(-1) in the hydrothermal plume,corresponding to the residence times of(115±19)d and(16±5)d for dissolved and particulate 234Th,*** timescale allows vent-discharged particle-reactive metals to disperse hundreds to thousands of miles ***,hydrothermal activities might influence the metal distribution in deep ocean over a very large ***,a high sinking flux of(36.2±5.4)B q/(m^(2)·d)for 234Th was observed for the plume,suggesting an enrichment of metal in particles deposited close to the *** enhancement of particle sinking could also benefit the transport of organic carbon and nitrogen and fuel the benthic ecosystems under the plume ***,hydrothermal plumes may have an impact on both the elemental geochemistry and/or ecosystem to the deep oceans interior than previous expectation.

关键词： thorium-234 particle dynamics hydrothermal plume Indian Ocean

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Sinking of particulates ^(234)Th_(xs),~7Be and ^(210)Pb_(xs) in the Changjiang estuary,China

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Chinese Journal of Oceanology and Limnology 2010年第6期28卷 1152-1159页

作者：黄德坤杜金洲吴云峰李道季张经 State Key Laboratory of Estuarine and Coastal Research East China Normal University

The time scale of transport and reaction processes in the ocean can be evaluated using natural radionuclides of different *** the present study,we evaluated the residence times of particulate reactive radionuclides 7 Be,210 Pb xs and 234 Th in the Changjiang (Yangtze River) estuary,which is a high turbidity estuary,in June,*** residence times of particulate 7 Be,234 Th xs and 210 Pb xs in the Changjiang estuary were calculated to be 0.7-20.4,0.18-4.1 and 0.6-89.8 d,*** obtained residence times of those nuclides are comparable with those of other estuaries and *** 234 Th xs and 7 Be,the residence times decreased with increasing concentrations of suspended particulate matter (SPM);however,those of 210 Pb xs ***,scavenging residence times of 234 Th and 7 Be increased from coast to offshore,while those of 210 Pb xs decreased.

关键词： thorium-234 beryllium-7 lead-210 residence times Changjiang (Yangtze River) estuary

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