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Poster De Conférence Année : 2012

Assessment of metal lability in freshwater sediments by passive sampling: parameters controlling metal release from particles and influence of bioturbation

Evaluation de la biodisponibilité des métaux dans les sédiments par le biais de capteurs passifs : paramètres contrôlant le relargage des particules et influence de la bioturbation

Résumé

The total metal concentration in sediments is generally not a good proxy to predict bioaccumulation or biological effects . Moreover, acid-volatile sulphides (AVS) strongly control metal mobility in sediments, as they are known to bind trace metals in marine or freshwater sediments (Burton et al., 2005). Indeed, metal–sulfide complexes may not be stable with oxidation (e.g. bioturbation), inducing a strong modification of metal mobility. To date, little work has been done to investigate the potential changes in metal bioavailability in surface sediments linked to variable oxygen concentration conditions, associated, in particular, with bioturbation. The Diffusive Gradient in Thin films (DGT), a passive sampler initially developed to measure labile metals in surface waters (Zhang and Davison, 1995), has been applied to soil and sediment (e.g. Roulier et al., 2010). When a DGT is introduced into sediments, trace metals of the pore waters are rapidly bound by the resin of the device; this results in a decrease of pore waters trace metals concentrations, inducing a variable resupply from the particulate phase. The aim of our study was first, to identify the parameters (particulate carrier phases) controlling the metal release from the particulate fraction to the pore water at the DGT-sediment interface and second, to assess the impact of bioturbation on metal mobility at the sediment–water interface. We first performed a series of laboratory experiments on naturally contaminated sediments with DGT (piston); then, we used DGT-probes to measure labile metals at the water-sediment interface, on a high AVS contents sediment while modifying the chironomids density of the sediment. First results showed that Cu and Pb bound to particulate phases were poorly reactive to supply DGT demand. In contrast, Zn was bound to reactive particulate phases inducing a strong supply from the particulate phase to pore waters in response to DGT demand. Preliminary results on the coupling of DGT probes and bioturbation showed a significant decrease of oxygen saturation in overlaying waters and in the first millimeters of sediment with increasing chironomids density. This difference induced of AVS concentration and an increase of metal labile concentrations (Mn and Ni) at the sediment interface (1.5 cm) suggesting an increase of labile metal fluxes to the water column.
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Dates et versions

hal-02597398 , version 1 (15-05-2020)

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A. Dabrin, R. Etienne, L. Dherret, J. Gahou, B.J.D. Ferrari, et al.. Assessment of metal lability in freshwater sediments by passive sampling: parameters controlling metal release from particles and influence of bioturbation. Environmental sensors, Sep 2012, Anglet, France. pp.1, 2012. ⟨hal-02597398⟩

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