Item characteristics of marine litter at the seafloor of the Baltic Sea

Plastic litter items (LI) at the seafloor of the Baltic Sea comprises different polymers. 40 LI were collected within fishery catches by bottom trawling during three cruises in 2020 and 2021 and analysed for their polymer types using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, performed on a Spotlight 400 FTIR Imaging System (PerkinElmer Inc., Waltham, USA). The resulting spectra were compared against reference spectra databases. Just LI spectra showing correlation factors above 0.90 compared to the reference spectra were included in the evaluation. Polymer type of plastic LI under investigation could be attributed to six different polymer groups: Polyethylene (PE), polyamide (PA), polypropylene (PP), polyvinylchloride (PVC), polyester (PES) and polyethylene terephthalate (PET). PE was the most frequently identified polymer representing 59% of all plastic items under investigation - followed by PA (17%), PP (12%), PVC (7%) and PES (3%).