| Paper Code |
13 |
| Title |
Li isotopes in the middle Yellow River: Seasonal variability, sources and fractionation |
| Authors |
Gou, LF |
| Corresponding Author |
Jin Zhangdong |
| Year |
2019 |
| Title of Journal |
|
| Volume |
248 |
| Number |
|
| Page |
88-108 |
| Abstract |
To evaluate the roles of climate and hydrology in continental-scale silicate weathering, we applied Li isotopes to the Yellow River and systematically investigated seasonal Li flux, Li isotopic compositions and potential sources. We collected samples from the middle reaches of the Yellow River weekly over the full hydrological year of 2013. We find that the dissolved Li is mainly derived from silicates and evaporites in the arid to semi-arid Yellow River basin. Silicate weathering of loess during the monsoonal season dominates the Li flux in the middle reaches of the Yellow River, with a positive relationship between dissolved Li flux and physical erosion rate. Evaporite contribution for riverine Li was relatively constant in the middle reaches of the Yellow River but slightly increased after the storm event, with an average proportion of similar to 25%, which might represent the proportion of evaporite contribution to global oceans. Seasonal variations in the riverine Li isotopic compositions are dominantly controlled by temperature with a fractionation gradient as -0.182 parts per thousand per degrees C over the full year with deviations likely driven by re-dissolution of suspended particulate matter, extreme hydrological events, and groundwater contribution. Temperature dependent delta Li-7 value variation of river water inputted into oceans indicates that Cenozoic climate cooling itself may be able to explain similar to 2 parts per thousand of the 9 parts per thousand rise of Cenozoic seawater delta Li-7 value (Misra and Froelich, 2012). The seasonal variation in riverine Li isotopes highlights that erosion and weathering of loess may provide valuable clues on secular chemical weathering and seawater delta Li-7 variation spanning a range of time scales. |
| Full Text |
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| Full Text Link |
https://www.sciencedirect.com/science/article/pii/S0016703719300201?via%3Dihub |
| Others: |
To evaluate the roles of climate and hydrology in continental-scale silicate weathering, we applied Li isotopes to the Yellow River and systematically investigated seasonal Li flux, Li isotopic compositions and potential sources. We collected samples from the middle reaches of the Yellow River weekly over the full hydrological year of 2013. We find that the dissolved Li is mainly derived from silicates and evaporites in the arid to semi-arid Yellow River basin. Silicate weathering of loess during the monsoonal season dominates the Li flux in the middle reaches of the Yellow River, with a positive relationship between dissolved Li flux and physical erosion rate. Evaporite contribution for riverine Li was relatively constant in the middle reaches of the Yellow River but slightly increased after the storm event, with an average proportion of similar to 25%, which might represent the proportion of evaporite contribution to global oceans. Seasonal variations in the riverine Li isotopic compositions are dominantly controlled by temperature with a fractionation gradient as -0.182 parts per thousand per degrees C over the full year with deviations likely driven by re-dissolution of suspended particulate matter, extreme hydrological events, and groundwater contribution. Temperature dependent delta Li-7 value variation of river water inputted into oceans indicates that Cenozoic climate cooling itself may be able to explain similar to 2 parts per thousand of the 9 parts per thousand rise of Cenozoic seawater delta Li-7 value (Misra and Froelich, 2012). The seasonal variation in riverine Li isotopes highlights that erosion and weathering of loess may provide valuable clues on secular chemical weathering and seawater delta Li-7 variation spanning a range of time scales. |
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