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Communication Dans Un Congrès Année : 2018

Evaluation of metal mobility in contaminated sediments using a sequential chemical extraction procedure and a multi-isotopic approach (Zn and Cu)

Résumé

Significant levels of trace metals issued from a variety of sources (industries, runoff from urban area, etc.) accumulate within sediments in many freshwater or marine environments. A major environmental risk is the remobilization of the contaminated particles and the increase in dissolved metal contents, getting more bioavailable for biota. In particular, natural events and anthropogenic activities (flood, dredging, etc.) can trigger the sediment resuspension, leading to changes in physico-chemical conditions surrounding solid particles (solid/liquid ratio, pH, redox potential, etc.). The distribution of trace metals between the solid and dissolved phases is then affected by chemical reactions (desorption, dissolution, etc.), sometimes resulting to an increase in dissolved pollutants. In laboratory, sequential chemical extraction (SCE) procedures are commonly applied to simulate the potential modifications of environmental conditions and assess the behavior of metals in sediments. The SCE procedures are based on the use of a series of reagents to extract metals according to their association within the solid phase including the following fractions: exchangeable, bound to carbonates and to pH dependent sites, associated to Fe-Mn oxides, linked to organic matter and sulfides, and silicate minerals. The purpose of this work was to investigate the behavior of metals (arsenic, chromium, cadmium, copper, nickel, lead and zinc) contained in sediments by coupling a SCE procedure, with Zn-zinc and Cu-copper isotopic measurements in each fraction. This study was performed on superficial freshwater sediments with distinct mineralogical compositions, sampled in three rivers impacted by industrial activities in France. The relative sequence of mobility displayed by the elements was distinct for the three sediments, involving distinct metal sources and various trapping mechanisms according to the sediments. The Zn and Cu isotopic compositions measured in bulk samples and in the different fractions showed that the isotopic ratios were strongly impacted by the physico-chemical processes. These first results highlighted that the isotopic measurements in environmental samples can potentially track the chemical reactions, responsible for the metal repartition between sediments and dissolved loads.
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Dates et versions

hal-03552805 , version 1 (02-02-2022)

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Romain Millot, Anne-Marie Desaulty, Sébastien Perret, S. Mertz, Anaëlle Simonneau, et al.. Evaluation of metal mobility in contaminated sediments using a sequential chemical extraction procedure and a multi-isotopic approach (Zn and Cu). American Geophysical Union, 2018, San Francisco, United States. ⟨hal-03552805⟩
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