Marine Pollution Bulletin 194 (2023) 115396 Available online 13 August 2023 0025-326X/© 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/). Investigation of potential metal emissions from galvanic anodes in offshore wind farms into North Sea sediments Anna Ebeling a,b,1, Dominik Wippermann a,b,1, Tristan Zimmermann a, Ole Klein a, Torben Kirchgeorg c, Ingo Weinberg c, Simone Hasenbein c, Anna Plaß c, Daniel Profrock a,* a Helmholtz-Zentrum Hereon, Institute of Coastal Environmental Chemistry, Department Inorganic Environmental Chemistry, Max-Planck-Str. 1, 21502 Geesthacht, Germany b Universitat Hamburg, Department of Chemistry, Inorganic and Applied Chemistry, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany c Federal Maritime and Hydrographic Agency (BSH), Wüstland 2, 22589 Hamburg, Germany A R T I C L E I N F O Keywords: Multielement analysis Technology-critical elements Isotope ratios German bight Pollution Offshore wind energy A B S T R A C T To evaluate potential metal emissions from offshore wind farms (OWFs), 215 surface sediment samples from different German North Sea OWFs taken between 2016 and 2022 were analyzed for their mass fractions of metals and their isotopic composition of Sr. For the first time, this study provides large-scale elemental data from OWFs of the previously proposed galvanic anode tracers Cd, Pb, Zn, Ga and In. Results show that mass fractions of the legacy pollutants Cd, Pb and Zn were mostly within the known variability of North Sea sediments. At the current stage the analyzed Ga and In mass fractions as well as Ga/In ratios do not point towards an accumulation in sediments caused by galvanic anodes used in OWFs. However, further investigations are advisable to evaluate long-term effects over the expected lifetime of OWFs, especially with regard to the current intensification of offshore wind energy development. 1. Introduction Renewable energy systems such as offshore wind energy play an important role to achieve the goal of sustainable energy transition and climate neutrality by 2050. The continuous rise and expansion of offshore wind power produced in offshore wind farms (OWFs) lead to a European-wide production capacity of 28 GW by the end of 2021 with 8 GW contributed by Germany (WindEurope, 2022). However, OWFs pose new anthropogenic pressures to the marine environment. Effects include, but are not limited to noise emissions, changes in ocean strat- ification and habitat changes (both, avoidance and attraction) (e.g. Christiansen et al., 2022; Degraer et al., 2021; Wright et al., 2020). Another aspect is possible emissions of both organic and inorganic substances from OWFs and related infrastructure (Kirchgeorg et al., 2018). Offshore structures are mainly constructed of steel, thus requiring thorough corrosion protection against harsh environmental conditions. Different corrosion protection systems are commonly applied, including galvanic anode cathodic protection, impressed cur- rent cathodic protection (ICCP), organic coatings, and corrosion allowance. Galvanic anodes dissolve over time and could therefore be a relevant source of metal emissions to the marine environment related with OWFs (Kirchgeorg et al., 2018). To protect offshore structures in seawater, Al-Zn-In-based galvanic anodes are commonly applied. In a previous study we estimated the dissolution of at least 2164 kg of Al-Zn-In-based anode material within the planned protection period of 27 years for one offshore wind monopile (6 m diameter, 26 m submerged in water and additionally coated) (Reese et al., 2020), resulting in a continuous emission of metals into the marine environment (Kirchgeorg et al., 2018). Al-based galvanic anodes contain alloying elements like Zn (>26,200 mg kg 1) and In (>143 mg kg 1) which influence the physi- cochemical properties of the anodes. Besides, up to 25 other elements like Cd (>0.255 mg kg 1), Pb (>6.7 mg kg 1) or elements with low natural abundance like Ga (>78.5 mg kg 1) have been found in Al-based galvanic anodes (Reese et al., 2020). The North Sea is a very unique and dynamic marine ecosystem with highly variable geological characteristics, which is partly due to inten- sive sediment movements in the coastal areas, not only through natural currents (Zeiler et al., 2008) but also by anthropogenic sediment * Corresponding author. E-mail address: daniel.proefrock@hereon.de (D. Profrock). 1 Both authors contributed equally as first author. Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul https://doi.org/10.1016/j.marpolbul.2023.115396 Received 8 May 2023; Received in revised form 3 August 2023; Accepted 5 August 2023