Abstract
Mercury contents were determined in surface sediments from the Central and Southern Adriatic Sea to gain insight into the processes, factors, and variables affecting its distribution. Mercury concentration was measured by thermal decomposition amalgamation atomic absorption spectrometry in samples collected by box-corer from Ancona to Santa Maria di Leuca during the CNR-PERTRE cruise (16/9-4/10/2016). Sediments were also evaluated for chemical-physical parameters (pH, Eh), biogeochemical composition (total carbon, inorganic carbon, total organic carbon, organic matter) and grain size. The average mercury concentration in the Adriatic Sea sediment was 0.053 mg/Kg (d.w.), range 0.011–0.12 mg/Kg (d.w.). Mercury content was mainly affected by grain size and organic matter (OM) distribution, whereas anthropic factors exerted a limited influence. Concentrations followed the distribution of sediment types (clay > silt > sand) due to Adriatic Sea hydrodynamics and were well below the regulatory limits in all samples.
Highlights
In marine ecosystems, the contaminant load is highest in sediment, which is the ultimate sink for the particulate material circulating in the overlying water column
The finer offshore belt is due to sediments from the Po River and the Apennine river system, which are transported southward by the cyclonic Adriatic circulation [27]
Mercury concentrations were determined in surface sediment collected in the Central and Southern Adriatic Sea to investigate their relationships with grain size and depositional processes
Summary
The contaminant load is highest in sediment, which is the ultimate sink for the particulate material circulating in the overlying water column. The contaminants adsorbed to or incorporated in particulate material are transferred by sedimentation to the seafloor, which in turn becomes a potential source of pollution for the overlying aqueous matrix. Pelagic and benthic aquatic ecosystems are characterised by four closely interacting compartments, the water column, suspended material, sediments, and pore waters. Adsorption/desorption and co-precipitation between suspended particulate and the dissolved phase are strongly influenced by pH, salinity, and oxidation-reduction conditions. Particulate material and bottom deposits are closely interconnected through erosion and sedimentation processes [1,2].
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