Numerical Approach for Isotopic Variations of Lithium in River Water

Abstract:

To investigate chemical weathering of silicate rocks, the riverine chemical composition can be considered. Since lithium is a fluid-mobile element and mainly derived from silicate minerals, Li isotopes are a useful proxy to describe water-solid interaction. In order to understand the continental weathering processes, numerical approach by developing a one-dimensional model is conducted. Unlike traditional stable isotopes, however, non-traditional isotopes are not yet clearly known about causes and mechanisms, making it difficult to illustrate isotope fractionation in quantitatively. In this study, we have developed an isotopic transport model for lithium isotopes by setting up governing equations. The model is tuned by γ and ψ representing the participation of solid phase in the isotopic reaction and the time to reach isotopic equilibrium, respectively. To verify the model, lithium isotopic data were obtained from Nakdong upstream to Andong dam, Republic of Korea. The best fit of γ and ψ from the analysis is 0.015 and 0.005, respectively. It is expected that this model can be used to explain lithium isotopic variations in weathering processes from upstream to downstream.