Ryu,J.-S., Lee,K.-S., Chang,H.-W. and Cheong,C.-S.(2009): Uranium isotopes as a tracer of sources of dissolved solutes in the Han River, South Korea. Chemical Geology, 258, 354-361.

『韓国の漢江における溶質の起源のトレーサーとしてのウラン同位体』


Abstract
 The uranium (U) content and 234U/238U activity ratio were determined for water samples collected from Korea's Han River in spring, summer, and winter 2006 to provide data that might constrain the origin of U isotope fractionation in river water and the link between U isotope systematics in river waters and the lithological nature of the corresponding bedrock. The large difference in the major dissolved loads between the two major branches of the Han River, the North Han River (NHR) and South Han River (SHR), is reflected in the contrasting U content and 234U/238U activity ratio between the tributaries: low U content (0.08-0.75 nM; average, 0.34 nM) and small 234U/238U activity ratio (1.03-1.22; average, 1.09) in the NHR; and high U content (0.65-1.98 nM; average, 1.44 nM) and large 234U/238U activity ratio (1.05-1.45; average, 1.24) in the SHR. The large spatial differences in U content and 234U/238U activity ratio are closely related to both lithological differences between the two tributaries and groundwater input. The low U content and small 234U/238U activity ratio in the NHR arise mainly from a combination of surface and meteoric weathering of the dominant silicate rocks in this branch and congruent dissolution of already weathered (secular equilibrium) materials. In contrast, the high U content and large 234U/238U activity ratio in the SHR are ascribed to the dissolution of carbonates and black shales along with significant inputs of deep groundwater.

Keywords: 234U/238U fractionation; Silicate weathering; Carbonate dissolution; Black shale; Groundwater input; Han River』

1. Introduction
2. Study area
 2.1. Geography and climate
 2.2. Geology
3. Sampling and analytical methods
4. Results
 4.1. Major elements and Sr isotopes
 4.2. Uranium isotopes
5. Discussion
 5.1. Seasonal variation
 5.2. Spatial variation
 5.3. Role of groundwater input
6. Conclusions
Acknowledgements
References


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