Article Dans Une Revue Science of the Total Environment Année : 2025

Geochemical analysis of overbank fine sediments of the Upper Rhine (Rhinau island, France): Evidence of metal (Pb, Zn, Cu & Sn) enrichments over the last century

Résumé

A geochemical analysis of a well-dated 1.2 m-thick sedimentary sequence collected on the Rhinau island at ~60km south of Strasbourg (France) has been performed in order to reconstruct the evolution of metal contents inoverbank fine sediments of the Upper Rhine over the last 150 years. Data indicate that most of the geochemicalvariations in major elements as well as in trace elements along the sedimentary profile can be related to variationsin the sediment mineralogical composition during deposition. Only Cu, Pb, Zn, and Sn highlight enrichmentin the sediments, interpreted as resulting from human releases into the fluvial hydrosystem. Enrichmentquantification is made by using diagrams of variation of element X normalized to silica as a function of Al2O3/SiO2. The results point out that each metal has its own enrichment pattern. The enrichment significances andorigins are discussed by comparing them with the knowledge of historical contaminant release and/or depositionin the Upper Rhine hydrosystem. Sn enrichment is thus linked to Sn releases by textile industries downstream ofBasel, whose activity peaked in ~1940/1950 CE before gradually declining. Pb enrichment, which started to decline in the mid-1980s and disappeared in the 2000s, is explained by the reduction and then cessation in the early 2000s of the two main sources of Pb pollution to the Rhine hydrosystem, namely (i) atmospheric fallout linked to the combustion of leaded gasoline and (ii) Pb flux associated to the Alsacian Potassium Mining rejects into the Rhine river. Cu and Zn enrichments are explained by diverse sources (e.g. agriculture, industries and wastewater treatment plants), whose emissions have reduced over the last decades but can still occur to a significant extent. Overall these results confirm potential and usefulness of our multi-method approach for assessing the effectiveness of public policies to reduce the impact of metal releases into continental hydrosystems, as well as their response time.

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Dates et versions

hal-05074671 , version 1 (20-05-2025)

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Cassandra Euzen, François Chabaux, Anne-Désirée Schmitt, Frédérique Eyrolle, Gilles Rixhon, et al.. Geochemical analysis of overbank fine sediments of the Upper Rhine (Rhinau island, France): Evidence of metal (Pb, Zn, Cu & Sn) enrichments over the last century. Science of the Total Environment, 2025, 967, pp.178678. ⟨10.1016/j.scitotenv.2025.178678⟩. ⟨hal-05074671⟩
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