Environmental Concern Over High Levels of Hg and other Metals in Sediments from the Seabed of the Northern Patagonian Platform (“El Rincón” Area), Argentina

Abstract

The present study evaluates, for the first time, the concentration and distribution of metals (Cd, Cu, Cr, Fe, Hg, Mn, Ni, Pb, Zn) in the sediments of the seabed of El Rincón and adjacent shelf areas, in the South Atlantic coast. Over a three-year period, coastal sectors were differentiated from offshore platform areas. The results revealed spatial and temporal differences, with concentration ranges of < LOD—2.58 mg/kg for Hg, < LOD—0.655 mg/kg for Cd, 24—638 mg/kg for Mn, 2.46—26.89 mg/kg for Cr, 2.02—13.43 mg/kg for Ni, 1.41—6.47 mg/kg for Pb, 0.44 -13.90 mg/kg for Cu, 5.85—36.05 mg/kg for Zn and 8300—43900 mg/kg for Fe. The concentrations of Cd were high and reached values ​​close to, but without exceeding, the maximum level recommended by the Sediment Quality Guidelines for marine and estuarine sediments (0.7 mg/kg), while Hg concentrations exceeded the Sediment Quality Guidelines (0.13 mg/kg) and the Probable Effect Level values (0.70 mg/kg). For Hg, the geoaccumulation index and the enrichment factor revealed highly contaminated sediments across all sectors during 2016. For Cd and Mn, only a minor anthropogenic impact was suggested through the enrichment factor, while the geoaccumulation indicated an absence of contamination by these metals. Overall, being an integrated index, the PLI indicated no metal pollution for the study area even when individual metrics for Hg revealed severe contamination. Therefore, long-term monitoring of this metal is crucial to assess potential ecological risks and support the development of environmental management policies to prevent potential adverse effects.