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Fate of metals in coastal sediments of a Mediterranean flood-dominated system: An approach based on total and labile fractions

Roussiez, Vincent and Ludwig, Wolfgang and Radakovitch, Olivier and Probst, Jean-Luc and Monaco, André and Charrière, Bruno and Buscail, Roselyne Fate of metals in coastal sediments of a Mediterranean flood-dominated system: An approach based on total and labile fractions. (2011) Estuarine, Coastal and Shelf Science, vol. 92 (n° 3). pp. 486-495. ISSN 0272-7714

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Official URL: http://dx.doi.org/10.1016/j.ecss.2011.02.009

Abstract

The dynamics of sediment-bound metals (Cs, Cu, Ni, Pb, Ti and Zn) were studied off the Têt River (western Gulf of Lion), a typical Mediterranean coastal river punctuated by short and violent flash-floods. Spatial and temporal sampling strategies were combined to elucidate the fate of these elements in response to both the riverine sediment input and the offshore transport of these sediments through hydrodynamics. Our results show the temporal entrapment of riverborne particles and associated metals, consecutively to a major flood event, in the nearshore sedimentary unit called prodelta. Here, deposition and resuspension mechanisms define a sedimentological cycle that could be followed completely in this study. In terms of speciation between reactive (labile) and residual fractions along the fluvio-deltaic continuum, our results show that Cu, Pb and Zn are the most labile (potentially mobile) metals in the river, in accordance with their contributions from anthropogenic sources. But in the marine surficial sediments, two main behaviours can be discriminated when compared to the riverine suspended particulate matter. While Pb and Zn depict rather a constant labile fraction, Cu is characterized by decreasing levels (up to 50% difference). In terms of environmental impact, these contrasting trends have direct repercussions for the contaminant dispersal in the coastal area. Whereas Pb and Zn conserve their enhanced levels because of their stronger affinity with fine sediments, Cu is marked by the entire loss of its anthropogenic component that is progressively transferred to the dissolved phase, likely mediated by organic ligands. We ascribe these behaviours to different post-depositional partition mechanisms with respect to oxidation of the particulate organic phase at the bottom sediment/water interface. Also, analysis of one sediment core from the prodelta indicates that these early diagenetic processes govern the chemical forms of land-derived contaminants sequestrated in the nearshore sedimentary archives.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com The original PDF of the article can be found at : http://www.sciencedirect.com/science/article/pii/S0272771411000503
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS
Other partners > Collège de France (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT
French research institutions > Institut de Recherche pour le Développement - IRD
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
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Other partners > Université de Provence - Aix-Marseille I (FRANCE)
Other partners > Université de la Méditerranée - Aix-Marseille II (FRANCE)
Other partners > Université Paul Cézanne - Aix-Marseille III (FRANCE)
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Deposited By:Nadia Kelmouss

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