Historical records of suspended particulate matter (SPM) origin in a large watershed: use of non-reactive geochemical signature of particles in the Upper Rhône River (France)
Abstract
Suspended particulate matter (SPM) flows in rivers are mainly due to soil erosion and anthropogenic activities. They contribute to the transport of a large amount of contaminants and can affect water quality and river ecosystem. To better manage these inputs in river systems, it is essential to identify the origin of SPM and sediments. In that way, SPM fluxes monitoring or fingerprinting approaches in rivers are increasingly addressed. In the frame of the Rhône sediment observatory (OSR) program, the Rhône River, the main sediment input to the Mediterranean Sea, is studied in details. Since 2011, SPM were monthly collected on the Rhône River and its main tributaries during contrasting hydrological conditions allowing developing fingerprinting approaches. Since chemical transformations of tracers (trace elements) can occur during particles transport and after settlement of SPM (diagenesis), the use of conservative parameters is essential to determine the origin of sediment at a given time and space.
The aims of this study were to use major and trace element concentrations in the conservative fraction of SPM from the Rhône and its tributaries in order (i) to determine the actual relative contribution of SPM fluxes from tributaries to the Rhône River and (ii) to determine the historical SPM inputs of the tributaries by applying this approach on a sediment core collected in the Upper Rhône. To assess element concentrations in the conservative fraction of SPM, samples were extracted by a total mineralization (HNO3, HCl, HF) and a soft extraction (HCl 1M). The discrimination of SPM and sediment sources were realized by using a Kruskal-Wallis test and a Discriminatory Factory Analysis to select element concentrations that could discriminate the 5 main tributaries of the Rhône. 6 discriminant elements were then integrated into a mixing model with uncertainty analysis using the Monte Carlo method. Artificial SPM mixtures were realized to assess the accuracy of our fingerprinting procedure. Subsequently, this method was applied on a sediment core sampled in the Upper Rhône located downstream 3 main sources. The results of fingerprinting analyses in this sediment core will allow defining a historical profile of sediment inputs and to set up the fingerprinting approach for subsequent application at the outlet of the Rhône catchment.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMEP33C2409B
- Keywords:
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- 0470 Nutrients and nutrient cycling;
- BIOGEOSCIENCESDE: 1815 Erosion;
- HYDROLOGYDE: 1862 Sediment transport;
- HYDROLOGYDE: 1879 Watershed;
- HYDROLOGY