Trace metals in sediments of the Var Canyon turbidite system at the DYFAMED station in the Ligurian Sea, supplement to: Heimbürger, Lars-Eric; Cossa, Daniel; Thibodeau, Benoit; Khripounoff, Alexis; Mas, Virginie; Chiffoleau, Jean-François; Schmidt, Sabine; Migon, Christophe (2012): Natural and anthropogenic trace metals in sediments of the Ligurian Sea (Northwestern Mediterranean). Chemical Geology, 291, 141-151


The magnitude and the chronology of anthropogenic impregnation by Hg and other trace metals of environmental concern (V, Cr, Ni, Cu, Zn, Ag, Cd and Pb, including its stable isotopes) in the sediments are determined at the DYFAMED station, a site in the Ligurian Sea (Northwestern Mediterranean) chosen for its supposed open-sea characteristics. The DYFAMED site (VD) is located on the right levee of the Var Canyon turbidite system, at the end of the Middle Valley. In order to trace the influence of the gravity current coming from the canyon on trace metal distribution in the sediment, we studied an additional sediment core (VA) from a terrace of the Var Canyon, and material collected in sediment traps at the both sites at 20 m above sea bottom. The patterns of Hg and other trace element distribution profiles are interpreted using stable Pb isotope ratios as proxies for its sources, taking into account the sedimentary context (turbidites, redox conditions, and sedimentation rates). Major element distributions, coupled with the stratigraphic examination of the sediment cores point out the high heterogeneity of the deposits at VA, and major turbiditic events at both sites. At the DYFAMED site, we observed direct anthropogenic influence in the upper sediment layer (<2 cm), while on the Var Canyon site (VA), the anthropization concerns the whole sedimentary column sampled (19 cm). Turbiditic events superimpose their specific signature on trace metal distributions. According to the 210Pbxs-derived sedimentation rate at the DYFAMED site (0.4 mm yr-1), the Hg-enriched layer of the top core corresponds to the sediment accumulation of the last 50 years, which is the period of the highest increase in Hg deposition on a global scale. With the hypothesis of the absence of significant post-depositional redistribution of Hg, the Hg/C-org ratio changes between the surface and below are used to estimate the anthropogenic contribution to the Hg flux accumulated in the sediment. The Hg enrichment, from pre-industrial to the present time is calculated to be around 60%, consistent with estimations of global Hg models. However, based on the chemical composition of the trapped material collected in sediment traps, we calculated that epibenthic mobilization of Hg would reach 73%. Conversely, the Cd/C-org ratio decreases in the upper 5 cm, which may reflect the recent decrease of atmospheric Cd inputs or losses due to diagenetic processes.

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Metadata Access
Creator Heimbürger, Lars-Eric; Cossa, Daniel; Thibodeau, Benoit; Khripounoff, Alexis; Mas, Virginie; Chiffoleau, Jean-François; Schmidt, Sabine; Migon, Christophe
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 2012
Funding Reference Sixth Framework Programme; Seventh Framework Programme
Rights Creative Commons Attribution 3.0 Unported
OpenAccess true
Language English
Resource Type Supplementary Collection of Datasets
Format application/zip
Size 2 datasets
Discipline Earth System Research
Spatial Coverage (7.349W, 43.410S, 7.861E, 43.492N)
Temporal Coverage Begin 2006-09-05T11:12:39Z
Temporal Coverage End 2006-09-08T10:48:45Z