IEG 환경지질연구정보센터

>> 89

Jong-Sik Ryu

, Kwang-Sik Lee

, and Ho-Wan Chang

1

Korea Basic Science Institute, Daejeon 305-333, Korea

2

Seoul National University, Seoul 151-742, Korea E-mail: [email protected]

U isotopes in the dissolved and suspended loads of the Han River, Republic of Korea: a comparison of carbonate dissolution and silicate weathering

Recent researches have indicated that U-series isotopes could be used as proxies for investigating water-rock interaction and infering timescales for sediment production and transport in river systems.

In this study, (

U/

U) was measured by MC-ICP-MS in the dissolved and suspended loads in the Han River waters, Republic of Korea. (

U/

U) ranges from 1.04 to 1.40 for dissolved loads and from 1.01 to 1.28 for suspended loads.

U-

U disequlilibrium in the dissolved loads indicates direct links with indices of weathering. On the other hand,

U-

U system in the suspended loads is almost near in secular equilibrium. (

U/

U) in the dissolved loads positively correlate with Ca/Na, HCO

and

Sr/

Sr indicating that both the carbonate dissolution and silicate weathering affect river water chemistry in the study area. Furthermore, the combination of (

U/

U) and

87

Sr/

Sr ratios gives a basis to differentiate the influence of tributaries with different water chemistries. Even known

as dissolved organic matter plays a key role in the release of

U from silicates, (

U/

U) of river waters draining

silicate terrain in the Han River basin shows a negative correlation with dissolved organic carbon (DOC), which is

different from basins with tropical climates.