Glitters in fishing ground baits - A direct source of primary microplastics in soil and freshwater ecosystems

The aim of this paper is to draw attention to the direct source of primary microplastics (MPs) that have been entirely neglected so far, namely by providing qualitative studies of the fishing ground baits with glitters. Among many microplastic sources already detected in fishing and angling gear and reported in the literature, the glitters in synthetic pastry are the only primary source (produced <5 mm; P-MPs), with MPs placed directly into the freshwater, during sports competitions and individual leisure activities, and were so far not discussed. Dozens of different fishbait pastry products available on the market containing glitters were funded to represent, from the material point of view, only three different classes studied further. Fourier-transform infrared (FTIR), ATR-FTIR and Raman spectroscopy combined with scanning electron microscopy with an energy-dispersive detector (SEM/EDS) enabled the characterization of their composition and morphology. Glitters are composite structures with an internal core and several chemical layers symmetrically placed on both sides. The polymer origin of particles, with the polyethylene terephthalate (PET) core, was confirmed as being an essential condition to classify them as P-MPs. One should focus on the fact that those primary microplastics are designed purposely to be particularly attractive and ingested by fishes, thus being efficiently introduced to the trophic chain with all persistent consequences, including their contribution to the plastisphere. The preliminary qualitative results of environmental stability were obtained in the accelerated ageing test to discuss the possible long-term ecological implications further. Glitters were durable in the saltwater (both natural and used for weathering in the ageing chamber) and in the seabed sediments. The primary weathering test was performed in marine environments, as oceans are the final destination of most freshwater MPs. Finally, suggestions for future studies to enlarge the knowledge about this issue are provided.