First indication of platinum input into the southern North Sea via German Rivers

Platinum (Pt) is an emerging critical metal, but the long-term environmental impacts of anthropogenic Pt remain largely unknown. We report, for the first time, Pt input from three major German rivers (Ems, Weser and Elbe) into the southern North Sea. All three rivers were a major source of Pt, with a maximum of 6.3 pmol L−1 in the Elbe endmember, compared to generally <1.0 pmol L−1 in the North Sea samples. All samples measured in the North Sea were elevated in Pt (mean of ∼0.9 pmol L−1) relative to typical open-ocean values (∼0.2–0.3 pmol L−1 in the Atlantic and Pacific). Across the Weser and Elbe estuarine transect, an initial sharp drawdown of Pt concentrations at low salinity (S < 1.5) was observed, which correlated well with Fe and Mn concentrations, indicating adsorption and co-precipitation at low salinity. At higher salinities (S ≥ 3) Pt concentrations followed a more conservative distribution relative to salinity. In addition, we followed a 12 h tidal cycle in each of the rivers, which generally reflected an inverse correlation of Pt concentrations against salinity. This study indicates that Pt might be an emerging contaminant in the North Sea, requiring further study to define specific sources.