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| Titel |
Behaviour of Mg isotopes during chemical weathering in the Han River, South Korea |
| VerfasserIn |
Jong-Sik Ryu, Sin-Woo Lee, Kwang-Sik Lee |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088409
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| Publikation (Nr.) |
 EGU/EGU2014-2509.pdf |
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| Zusammenfassung |
| Magnesium (Mg) isotopes can be useful for directly constraining the sources of riverine Mg,
but the dominant controls on riverine Mg isotope ratios are still uncertain. Here, we
report Mg isotope ratios for river waters, experimental leachates and digestions, bulk
rocks, and fertilizers in the Han River (HR), South Korea. The HR is composed
of two lithologically distinct tributaries: the North Han River (NHR) that flows
over only silicate rocks, and the South Han River (SHR) that flows over carbonate
rocks in the upper part. The lithological differences between the NHR and SHR
are reflected in major ion, 87Sr/86Sr, and δ26Mg geochemistry. In particular, the
NHR has lower major ion concentrations but higher 87Sr/86Sr ratios and δ26Mg
values than the SHR. Simple mass balances and mixing equations indicate that if the
riverine δ26Mg values in the HR system are mainly controlled by conservative mixing
between silicate and carbonate weathering, the average carbonate end-member δ26Mg
value should be unlikely lower than what are measured in this study. Although
multiple process-related fractionations occur in the HR system, the enrichment of
24Mg in the NHR could be mostly controlled by either fractionation or mixing
between isotopically distinct reservoirs, such as minerals or fractions (labile and
structural Mg), during dissolution, while the little depletion of 24Mg in the SHR
could be likely due to the input of groundwater with lower δ26Mg value rather than
fractionation. However, it is difficult to identify the contribution of anthropogenic
inputs to riverine δ26Mg because their effects are little. This study suggests that the
potential of Mg isotopes for constraining Mg sources in a lithologically varied river
basin can be enhanced with a better understanding of process-related fractionation. |
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