Coupling metal concentrations and drift simulations for tracing emissions from offshore wind farms

During the last decade offshore wind energy production has become an important source of renewable energy. To ensure safe operation during the lifetime of an offshore wind turbine, the steel structures need to be protected against corrosion. This work evaluates potential metal emissions and environmental impacts from galvanic anodes used for corrosion protection of offshore wind farms (OWFs) by applying a novel multi-tracer approach. A total of 235 surface water samples from different German North Sea OWFs were taken between 2016 and 2022 and analyzed for their concentration of 32 metals via online preconcentration/matrix removal ICP-MS/MS. The concentrations were assessed for temporal and spatial trends with an emphasis on the previously proposed OWF tracers Al, Cd, Pb, Zn, Ga and In. By comparing patterns of In concentrations and Gd anomalies together with modelled drift trajectories of water masses, a differentiation of riverine and OWF-induced metal load was achieved. Results suggest that elevated In concentrations may be linked to OWF corrosion protection systems. Other metal concentrations remained within natural variability. This study demonstrates that the applied tracer approach is effective in identifying OWF-induced metal emissions. Furthermore, it highlights the necessity for long-term monitoring of these tracers to further investigate this emerging source of contamination.