Advances in understanding mobilization processes of trace metals in marine sediments

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Different mobilization mechanisms control the metal distribution in surface sediments of the Belgium coastal zone (BCZ) and the anoxic Gotland basin (GB). This mobilization was studied using DGT (Diffusive Gradients in Thin-films): vertical 1D profiles of Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn were measured at 5 mm intervals, while 2D high-resolution (100 µm) images of smaller zones of the sediment profile were obtained on separate DGT probes. Consumption of Cd, Cu, and Pb in BCZ sediments caused steep vertical gradients at the sediment water interface that were well replicated in 1D profiles and 2D images. While 1D profiles showed apparent coincident maxima of Co, Mn, and Fe, 2D images revealed mutually exclusive Co and Fe mobilization. Correlation analysis supported this observation and showed a consistent linkage between Co and Mn. Sharp maxima of some metals in the vertical 1D profiles of GB sediment were attributed to localized mobilization in microniches. Examination of a ~1 mm diameter Cu and Ni maximum in 2D, defined by ~300 data points, showed that the metals were supplied from localized decomposition of reactive organic material, rather than release from reductively dissolving Fe or Mn oxides, and that they were removed as their sulfides.
Original languageEnglish
Pages (from-to)15151-15161
Number of pages11
JournalEnvironmental Science and Technology
Issue number23
Publication statusPublished - 1 Dec 2020

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