Microplastic particles investigated by Fourier transform infrared spectroscopy. Left: Examples of three different particles found in the coastal surface waters west of Sweden, in November 2015. The particles, as seen in the photograph, differ in size and structure. Right: Using Fourier transform infrared spectroscopy (FTIR), particles 1 and 2 were recognized as polystyrene and particle 3, as polypropylene. The photograph also indicates that the particles have undergone degradation, which is further supported by the formation of hydroxyl groups (around 3000 cm^–1) and a formation of carbonyl groups (1714 cm^–1) in the FTIR spectra. The formation of these groups has previously been associated with degradation for both polypropylene and polystyrene (Wang et al., 1996; Qin et al., 2005). (Left photo: Sameh Az Aldeen; right data: Karlsson, T, Hassellöv, M, unpublished). DOI: https://doi.org/10.1525/elementa.149.f3