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Multi isotopic characterization (Li-Cu-Zn-Pb) of waste waters pollution in a small watershed (Loire River basin, France)

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Résumé

The goal of this study is to use multi-isotopic signature to track the pollution in surface waters, and to understand the complex processes causing the metals mobilization and transport in the environment. In the present study, we investigate waste water releases from a hospital water treatment plant and its potential impact in a small river basin near Orléans in France (Egoutier watershed: 15 km²and 5 km long). We decided to monitor this small watershed which is poorly urbanized in the Loire river basin. Its spring is located in a pristine area (forested area), while it is only impacted some kilometers further by the releases rich in metals coming from a hospital water treatment plant. A sampling of these liquid effluents as well as dissolved load and sediment from upstream to downstream was realized and their concentrations and isotopic data were determined. Isotopic ratios were measured using a MC-ICP-MS at BRGM, after a specific protocol of purification for each isotopic systematics. Lithium isotopic compositions are rather homogeneous in river waters along the main course of the stream. The waste water signal is very different from the natural background with significant heavy lithium contribution (high 7Li). Lead isotopic compositions are rather homogenous in river waters and sediments with values close to geologic background. For Zn, the sediments with high concentrations and depleted isotopic compositions (low 66Zn), typical of an anthropic pollution, are strongly impacted. The analyses of Cu isotopes in sediments show the impact of waster waters, but also isotopic fractionations due to redox processes in the watershed. To better understand these processes controlling the release of metals in water, sequential extractions on sediments are in progress under laboratory conditions and will provide important constraints for metal distribution in this river basin.

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Dates et versions

hal-01351018 , version 1 (02-08-2016)

Identifiants

  • HAL Id : hal-01351018 , version 1

Citer

Romain Millot, Anne-Marie Desaulty, Sébastien Perret, Xavier Bourrain. Multi isotopic characterization (Li-Cu-Zn-Pb) of waste waters pollution in a small watershed (Loire River basin, France). AGU Fall Meeting , American Geophysical Union, Dec 2016, San Francisco, United States. ⟨hal-01351018⟩

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