Polycyclic aromatic compounds including non-target and 71 target polycyclic aromatic hydrocarbons in scrubber discharge water and their environmental impact Christine Achten a,*, Octavio Marin-Enriquez b, Brigitte Behrends c, Sandra Kupich a, Andreas Lutter a, Richard Korth a, Jan T. Andersson d a Institute of Geology and Palaeontology – Applied Geology, University of Münster, Corrensstraße 24, 48149 Münster, Germany b Federal Maritime and Hydrographic Agency (BSH), Bernhard-Nocht-Straße 78, 20359 Hamburg, Germany c St. Annen-Str. 27, 26441 Jever, Germany d Institute of Inorganic and Analytical Chemistry, University of Münster, Corrensstraße 28/30, 48149 Münster, Germany A R T I C L E I N F O Keywords: Polycyclic aromatic hydrocarbons Scrubber discharge water Atmospheric pressure laser ionization Non-target analysis Shipping emission Dioxin-like effects A B S T R A C T Increasing use of scrubbers on vessels for reduction of SOx emissions has led to environmental concerns due to discharge of partly persistent and toxic substances such as polycyclic aromatic compounds (PAC) into the sea. A comprehensive analysis of the dissolved and particulate phases of the discharge water from open and closed loop operations on four ships was performed. 71 PAC in the discharge waters varied in concentration and were associated with those of the fuels used, as they mainly originate in unburnt fuel. Closed loop discharge water showed higher PAC concentrations, especially of HMW PAC, which partly explains the larger toxic effects re- ported for this discharge. Alkylnaphthalenes and -phenanthrenes dominated in dissolved and particulate frac- tions, respectively. 14 NSO-PAC concentrations were relatively low. Alkylated derivatives of 4H-cyclopenta[4,5- def]phenanthrene and/or phenylnaphthalene were for the first time tentatively identified using GC-APLI-MS. The use of low-PAC fuels could significantly reduce PAC ship emissions. 1. Introduction International shipping is a very important transport mode since an estimated 90 % (by weight) of our goods are transported by ships (IMO, 2023a). Marine fuels are less refined and the standards for their composition and emissions are less strict than those for other transport sectors. Smith et al. (2015) reported that marine transportation accounted for 13 % of the world's anthropogenic sulfur oxide (SOx) emissions. SOx react with water and ultimately form sulfuric acid which causes aquatic and terrestrial acidification, and their salts (sulfates) form aerosols that increase human health risks (EPA, 2023; IMO, 2023b). Therefore, the International Convention for the Prevention of Pollution from Ships (MARPOL), in its Annex VI (Prevention of Air Pollution from Ships), has set limit values on the sulfur content of ma- rine fuels. These values depend on whether the ship sails in a sulfur emission control-area (SECA), where the maximum sulfur content of the fuel is 0.10 % (by weight) since 1st January 2015, or outside these areas, where the sulfur cap is 0.50 % (by weight) since 1st January 2020. These limits are mainly achieved by use of distillate fuels (e.g. marine gasoil and marine diesel oil), very-low sulfur or ultra-low sulfur fuel oils (VLSFO and ULSFO) and/or alternative fuels (e.g. liquefied natural gas). Alternatively, ships are allowed to install technologies that reduce the SOx emissions to an equivalent level. In that case they can continue using cheaper, high?sulfur fuel (heavy fuel oil, HFO). Exhaust Gas Cleaning Systems (EGCS), or so-called wet scrubbers, represent such a technology. As scrubbers are economically more attractive, due to the price-gap between VLSO and ULSFO on the one side and HFO on the other, their installations account for 25 % (by deadweight tonnage) of the global merchant fleet (Marin-Enriquez et al., 2023). Scrubbers can be subdivided into open loop (OL), closed loop (CL) and hybrid systems which can switch between both operation modes (OL and CL). The majority are OL-scrubbers that typically use seawater sprayed into the flue gas to capture SOx that is subsequently discharged into the sea. Some OL-scrubbers include a water treatment step and some dilute the wash water prior to discharge. Wash water is turned * Corresponding author. E-mail address: achten@uni-muenster.de (C. Achten). Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul https://doi.org/10.1016/j.marpolbul.2024.116790 Received 20 June 2024; Received in revised form 26 July 2024; Accepted 27 July 2024 Marine Pollution Bulletin 208 (2024) 116790 Available online 12 September 2024 0025-326X/© 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC license ( http://creativecommons.org/licenses/by- nc/4.0/ ).