Weathering Processes in the Four Largest Chinese River Basins: Insights from the Lithium Isotopic Compositions of River-transported Material
Abstract
Chemical and isotopic compositions of riverine material (sediment and dissolved load) carry the fingerprints of weathering and erosion processes integrated over large areas of the Earth's surface. However, deciphering the message is complicated by the superimposition of the effects resulting from lithological heterogeneities, mineral sorting during the transport, as well as anthropogenic disturbances.
In this aim, sampling along depth profile across river section is a powerful way to appraise the integrated chemical composition of the transported material not biased by transport processes for example and allows for retrieving information on the compositions of the rock source material and weathering products by analyzing different grain sizes of the river sediment. We combined this approach with time series sampling of surface water from the four largest rivers in China: Zhujiang, Changjiang, Huanghe and Heilongjiang from south to north. These four river basins covering a variety of lithologies and facing with an increasing anthropogenic pressure are characterized by a strong climatic gradient and different geomorphic regimes, providing an ideal study object to decipher natural and anthropogenic processes from river-transported materials. Li isotopes are strongly fractionated during weathering processes and have been proved to be a good proxy of weathering intensity (e.g. Dellinger et al., 2015). We present here the Li isotope composition of the sedimentary and dissolved loads of the four Chinese rivers. By combining Li isotopes with other geochemical proxies of sediment provenance and grain size and using mass balances, we aim at disentangling the effects of lithology and mineral sorting to evaluate : (1)weathering processes over a large scale; (2) the impact of anthropogenic activities on the supply and transport of material by the four largest Chinese rivers. Reference Dellinger, M., GCA, 2015. This work is supported by an NSFC-ANR joint research program through the NSFC grant No.41561134017.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP33C2366S
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 1030 Geochemical cycles;
- GEOCHEMISTRY;
- 1815 Erosion;
- HYDROLOGY;
- 1862 Sediment transport;
- HYDROLOGY