| Size-fractionated uranium isotopes in surface waters in the Jiulong Estuary in China |
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| 作者姓名： | L&#; E ZHANG Lei CHEN Min QIU Yusheng XING N YANG Weifeng LI Yanping HUANG Yipu |
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| 作者单位： | Department of Oceanography, Xiamen University, Xiamen 361005, China;Department of Oceanography, Xiamen University, Xiamen 361005, China;Department of Oceanography, Xiamen University, Xiamen 361005, China;State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China;Department of Oceanography, Xiamen University, Xiamen 361005, China;State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China;Department of Oceanography, Xiamen University, Xiamen 361005, China;Department of Oceanography, Xiamen University, Xiamen 361005, China;Department of Oceanography, Xiamen University, Xiamen 361005, China;Department of Oceanography, Xiamen University, Xiamen 361005, China;State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China |
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| 基金项目： | The National Key Basic
Research Special Foundation Program of China under contract No.2005CB422305 and the China
Ocean Mineral Resources Research and Development Association Foundation under contract Nos
DY105-02-04 and DY105-02-01. |
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| 摘 要： | Surface water was collected from the Jiulong Estuary for determination of activity concentrations of uranium isotopes in different size fractions, namely, greater than 53, 10 -53, 2 - 10, 0.4 -2 μm, 10 000 u -0.4 μm and less than 10 000 u fractions by microfihration and cross-flow uhrafiltration technologies. Results indicated that most of the dissolved uranium （ 〈 0.4 μm） exis- ted in the low molecular mass fraction （ 〈 10 000 u）, and the colloidal uranium-238 （10 000 u -0.4 μm） only contributed less than 1% of the dissolved uranium-238. The fractions of colloidal uranium in the dissolved phases decreased with the increasing sa- linity. A positive linear relationship between uranium-238 activities and salinities was observed for the dissolved, colloidal and low molecular mass fractions, indicating a conservative behavior of uranium in the Jiulong Estuary. In the particulate phases （ 〉 0.4 μm）, the partitioning of uranium isotopes among different size fractions was controlled by the partitioning of particle concentrations. In the regions with salinities below 20, the partitioning of uranium-238 among different size fractions was as follows： 10 - 53 μm 〉 2 - 10 μm 〉 0.4 - 2 μm greater than above 53 μm. However, the order at the offshore station with salinities above 30 changed as follows ： 0.4 - 2 μm 〉 10 - 53 μm 〉 2 - 10 μm greater than above 53 μm. The fraction of the 0.4 - 2 μm particles increased at the offshore station, suggesting the increased contribution of the authigenic uranium. The activity ratio of uranium-234 to uranium-238 in the dissolved phases, including the low molecular mass fraction and the colloidal fraction, was larger than unity, showing the occurrence of excess uranium-234. In contrast, the activity ratio of uranium-234 to uranium-238 in all size fractions of the particulate phase was close to the equilibrium value （1.0）. The observed different values of the activity ratio of uranium-234 to uranium-238 in the dissolved phase and the partic
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| 关 键 词： | 铀同位素 分馏法 表层水 九龙河 中国 |
| 收稿时间： | 2007/4/23 0:00:00 |
| 修稿时间： | 2007/5/31 0:00:00 |
Size-fractionated uranium isotopes in surface waters in the Jiulong Estuary in China |
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| L&#; E,ZHANG Lei,CHEN Min,QIU Yusheng,XING N,YANG Weifeng,LI Yanping,HUANG Yipu.Size-fractionated uranium isotopes in surface waters in the Jiulong Estuary in China[J].Acta Oceanologica Sinica,2008,27(1):29-41. |
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| Authors: | L&#; E ZHANG Lei CHEN Min QIU Yusheng XING N YANG Weifeng LI Yanping and HUANG Yipu |
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| Institution: | 1.Department of Oceanography, Xiamen University, Xiamen 361005, China2.Department of Oceanography, Xiamen University, Xiamen 361005, China;State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China |
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| Abstract: | Surface water was collected from the Jiulong Estuary for determination of activity concentrations of uranium isotopes in different size fractions,namely,greater than 53,10～53,2～10,0.4～2 μm,10 000 u～0.4 μm and less than 10 000 u fractions by microfihration and cross-flow ultrafihration technologies.Results indicated that most of the dissolved uranium (<0.4 μm) exis- ted in the low molecular mass fraction ( < 10 000 u),and the colloidal uranium-238 ( 10 000 u～0.4 μm) only contributed less than 1% of the dissolved uranium-238.The fractions of colloidal uranium in the dissolved phases decreased with the increasing sa- linity.A positive linear relationship between uranium-238 activities and salinities was observed for the dissolved,colloidal and low molecular mass fractions,indicating a conservative behavior of uranium in the Jiulong Estuary.In the particulate phases ( 0.4 μm),the partitioning of uranium isotopes among different size fractions was controlled by the partitioning of particle concentra- tions.In the regions with salinities below 20,the partitioning of uranium-238 among different size fractions was as follows:10～ 53 μm2～10 μm0.4～2 μm greater than above 53 μm.However,the order at the offshore station with salinities above 30 changed as follows:0.4～2 μm 10～53 μm 2～10 μm greater than above 53 μm.The fraction of the 0.4～2 μm particles increased at the offshore station,suggesting the increased contribution of the authigenic uranium.The activity ratio of uranium-234 to uranium-238 in the dissolved phases,including the low molecular mass fraction and the colloidal fraction,was larger than uni-ty,showing the occurrence of excess uranium-234.In contrast,the activity ratio of uranium-234 to uranium-238 in all size frac-tions of the particulate phase was close to the equilibrium value (1.0).The observed different values of the activity ratio of urani-um-234 to uranium-238 in the dissolved phase and the particulate phase were ascribed to the preferential leaching of uranium-234 and the small amount of the leaching particulate uranium.The mass ratio of thorium-232 to uranium-238 also showed different val- ues between the dissolved phase and the particulate phase.Mass ratio of thorium-232 to uranium-238 in the dissolved,colloidal and low molecular mass fractions was less than unity,while those in the different size fractions of particulate phases were larger than unity,reflecting a different behavior between uranium and thorium during their transport into the ocean. |
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| Keywords: | uranium isotopes size fractionation Jiulong Estuary in China |
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