Abstract
Offshore wind farms (OWFs) are pivotal for fulfilling the EU’s goal to a sustainable energy transition and achieving climate neutrality by the year 2050 and the 2023’s UN Climate Change Conference (COP28) agreement to triple renewable energy capacity by 2030. By 2023, 75.2 GW of offshore wind capacity had been installed worldwide, 38 GW of which in Chinese and 34 GW in European waters. Moreover, recent advancements are aiming to produce green hydrogen and secondary products such as ammonia, methanol and synthetic fuels offshore. The impact of offshore constructions – wind turbines and production platforms – on the marine environment, is in the focus of a broad range of research efforts (e.g. ecological aspects). However, little is known about potential chemical emissions from corrosion protection systems such as galvanic anodes, composed of AlZnIn alloys, used to protect offshore structures. Galvanic anodes are designed to corrode in place of the structural steel, resulting in the continuous emission of metals (e.g. >2000 kg Al-anode material per pile for the lifetime of 25 years [1, 2]) into the marine environment. Four galvanic anodes from various manufacturers were analyzed for their elemental composition and Pb isotope ratios after total digestion via ICP-MS/MS and MC ICP-MS. The elements Al, Zn, Cd, Pb, Ga and In were identified as potential tracers for offshore-wind-induced emissions together with Pb isotope ratios.[2] In order to gain additional insights into the distribution across the compartments seawater, particulate matter and sediments, the dissolution of the four anodes was observed in corrosion measurement cells. The anodes were electrically contacted to steel plates as cathodes in artificial seawater as electrolyte (with and without sediment). The proposed tracers were determined in seawater and sediment samples from OWFs in the German Bight collected between 2016-2022. The presentation will evaluate the suitability of the proposed tracer approach and highlight additional tracer concepts: The combination of In concentrations and Gd anomaly determined in seawater samples proved to be a promising approach to differentiate between offshore-induced emissions (corrosion protection systems) and riverine metal inputs. For sediments a broad multielement dataset enabled the calculation of element ratios like Ga/In which was used together with Sr isotope ratios to find hints of OWF-induced emissions and to identify sources of metals in the sediments.[3]
