| LÜ E,ZHANG Lei,CHEN Min,QIU Yusheng,XING Na,YANG Weifeng,LI Yanping,HUANG Yipu. 2008. Size-fractionated uranium isotopes in surface waters in the Jiulong Estuary in China. Acta Oceanologica Sinica, (1):29－41 |
| Size-fractionated uranium isotopes in surface waters in the Jiulong Estuary in China |
| Size-fractionated uranium isotopes in surface waters in the Jiulong Estuary in China |
| Received:April 23, 2007 Revised:May 31, 2007 |
| DOI： |
| Key words:uranium isotopes size fractionation Jiulong Estuary in China |
| 中文关键词: uranium isotopes size fractionation Jiulong Estuary in China |
| 基金项目:The National Key Basic Research Special Foundation Programof China under contract No.2005CB422305;the China Ocean Mineral Resources Research and Development Association Foundation under contract Nos DY105-02-04 and DY105-02-01. |
| Author Name | Affiliation | E-mail | | LÜ E | Department of Oceanography, Xiamen University, Xiamen 361005, China | | | ZHANG Lei | Department of Oceanography, Xiamen University, Xiamen 361005, China | | | CHEN Min | Department of Oceanography, Xiamen University, Xiamen 361005, China
State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China | mchen@xmu.edu.cn | | QIU Yusheng | Department of Oceanography, Xiamen University, Xiamen 361005, China
State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China | | | XING Na | Department of Oceanography, Xiamen University, Xiamen 361005, China | | | YANG Weifeng | Department of Oceanography, Xiamen University, Xiamen 361005, China | | | LI Yanping | Department of Oceanography, Xiamen University, Xiamen 361005, China | | | HUANG Yipu | 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 microfiltration and cross-flow ultrafiltration technologies. Results indicated that most of the dissolved uranium (<0.4 μm) existed 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 salinity. 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 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 values 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. |
| 中文摘要: |
| 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 microfiltration and cross-flow ultrafiltration technologies. Results indicated that most of the dissolved uranium (<0.4 μm) existed 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 salinity. 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 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 values 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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