Long-term records of trace metal elements in core sediments: anthropogenic impacts in the Eure river watershed

Abstract : The Martot Dam is located in the Eure River Watershed (Normandy, France), few hundred meters upstream the Eure-Seine Rivers confluence. In the context of the European Water Framework Directive (2000/60/EC), the French Authorities planned to remove this dam in 2017. Nevertheless, impacts of the removal remain poorly studied. Classically, dam blocked sedimentary transfers downstream, but here, sediments are not blocked behind the dam but stored three hundred meters upstream in a hydraulic annex, called the Martot Pond. Furthermore, this pond is submitted to the tidal flow from the Seine Estuary despite the Martot Dam.The aim of the study is to evaluate the dam removal impacts on sedimentary transfers and re-suspension of contaminated sediments stored in the Martot Pond and the Eure River’s channel. Concerning past transfers and sediments accumulation in the Eure River Watershed, sedimentary archives have been cored, before dam removal, at the Martot Pond and the Les Damps Pond (located 10km upstream the latter). Dating of sedimentary cores for both ponds indicates a sedimentation rate around 1 cm y-1. Trace metal elements quantification showed a wide metallic contamination with highest concentrations evidenced during the 1950-1960’s (As: ~13-22 mg kg-1; Cd: ~40-55 mg kg-1; Cr: ~170-210 mg kg-1; Cu: ~400-490 mg kg-1; Hg: ~2.3 mg kg-1; Mn: ~1,280-2,200 mg kg-1; Ni: ~64-75 mg kg-1; Zn: ~905-990 mg kg-1) and the 1990-2000’s (Cr: ~95-215 mg kg-1; Ni: ~100 mg kg-1; Pb: ~670-855 mg kg-1). These variations of concentrations along cores can be associated with industrial past of the Eure River Watershed and sources of contamination can be identified. Thereby, Zn, Ni or Hg contamination could be associated with wastes of battery factory released in the Eure River during the economic recovery, while Pb contamination is linked to the activities of a cathode-ray tubes factory.Metals quantification in core materials highlighted anthropogenic impacts in the Eure River Watershed.These contaminated sediments could be re-suspended and transferred to the Seine River in case of remobilization in Martot Pond and the Eure River’s channel after dam removal.
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Thomas Gardes, Maxime Debret, Yoann Copard, Edouard Patault, Julien Deloffre, et al.. Long-term records of trace metal elements in core sediments: anthropogenic impacts in the Eure river watershed. AGU Fall Meeting, Dec 2017, New Orleans, United States. ⟨hal-01855428⟩

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